Determination of P – wave arrival time of acoustic events
Acceleration of stable TTI P-wave reverse-time migration with GPUs
Acceleration of stable TTI P-wave reverse-time migration with GPUsYoungseo Kim a,n,Yongchae Cho b,Ugeun Jang b,Changsoo Shin ba Seoul National University,Research Institute of Energy and Resources151-744/Building135,College of Engineering,Seoul National University,Daehak-dong Gwanak-gu,Seoul,Republic of Koreab Seoul National University,Research Institute of Energy and Resources151-744/36-2061College of Engineering,Seoul National University,Daehak-dongGwanak-gu,Seoul,Republic of Koreaa r t i c l e i n f oArticle history:Received7May2012Received in revised form25September2012Accepted19October2012Available online29October2012Keywords:GPUMPIREMRTMTTIa b s t r a c tWhen a pseudo-acoustic TTI(tilted transversely isotropic)coupled wave equation is used to implementreverse-time migration(RTM),shear wave energy is significantly included in the migration image.Because anisotropy has intrinsic elastic characteristics,coupling P-wave and S-wave modes in thepseudo-acoustic wave equation is inevitable.In RTM with only primary energy or the P-wave mode inseismic data,the S-wave energy is regarded as noise for the migration image.To solve this problem,we derive a pure P-wave equation for TTI media that excludes the S-wave energy.Additionally,weapply the rapid expansion method(REM)based on a Chebyshev expansion and a pseudo-spectralmethod(PSM)to calculate spatial derivatives in the wave equation.When REM is incorporated with thePSM for the spatial derivatives,wavefields with high numerical accuracy can be obtained without griddispersion when performing numerical wave modeling.Another problem in the implementation of TTIRTM is that wavefields in an area with high gradients of dip or azimuth angles can be blown up in theprogression of the forward and backward algorithms of the RTM.We stabilize the wavefields byapplying a spatial-frequency domain high-cutfilter when calculating the spatial derivatives using thePSM.In addition,to increase performance speed,the graphic processing unit(GPU)architecture is usedinstead of traditional CPU architecture.To confirm the degree of acceleration compared to the CPUversion on our RTM,we then analyze the performance measurements according to the number of GPUsemployed.&2012Elsevier Ltd.All rights reserved.1.IntroductionRTM(reverse-time migration)(Baysal et al.,1983)is the mosteffective tool for imaging the sequence structure of strata withdistinct velocity contrasts and geologically complex structures.Although practical implementation requires substantial comput-ing costs,the rapid development of the computer industry andthe improvement of the algorithm have made RTM a leader inhigh-end imaging.As the outcomes have become common ininterpreting geological structures,many studies have focused onenhancing the images obtained by RTM.One factor for improvingRTM is the consideration of anisotropy.Although most rocks havethe characteristics of anisotropy,many geophysicists have notwanted to use elastic wave equation-contained anisotropy para-meters because the S-wave must be inherently included in theequation.To apply the anisotropic characteristics of rocks to RTM andeliminate the S-wave modes in the wave equation,Alkhalifah(2000)derived a simplified dispersion relation in VTI(verticaltransversely isotropic)media by setting the SV-wave velocity tozero.The dispersion relation was referred to as pseudo-acousticapproximation,and the VTI pseudo-acoustic wave equation wasapplicable to describing the seismic anisotropy of subsurfaceformations.However,because the symmetric axis perpendicularto the bedding is not always vertical,migration images with theVTI approximation cannot always provide the best quality interms of the definition of layers and salt boundaries.To considervarious geological structures,Zhou et al.(2006)and Fletcher et al.(2009)derived the TTI(tilted transversely isotropic)pseudo-acoustic wave equation based on the Alkhalifah approximation.Three major problems exist in the RTM with the TTI pseudo-acoustic wave equation.First,SV-waves are generated as artifactsin numerical modeling,although it seems that there should beonly P-wave components.Grechka et al.(2004)proved that theartifacts are actually correctly modeled SV-waves of a TI(trans-versely isotropic)medium that has v s¼0.Although we regard v sas zero,this assumption does not mean that the SV-wave phasevelocity is zero for all propagation angles.To solve this problem,Duveneck et al.(2008)set Thomsen’s(1986)parameters,E and d,to be equal in a small region close to a source position,and ZhangContents lists available at SciVerse ScienceDirectjournal homepage:/locate/cageoComputers&Geosciences0098-3004/$-see front matter&2012Elsevier Ltd.All rights reserved./10.1016/j.cageo.2012.10.013n Corresponding author.Tel.:þ821042285568;fax:þ8228756296.E-mail address:kysgood0@snu.ac.kr(Y.Kim).Computers&Geosciences52(2013)204–217et al.(2009)proposed a set of new equations based on the eigenvalue analysis of the original acoustic wave equation.The second problem is that the numerical modeling of the TTI pseudo-acoustic wave equation takes much more time than does the acoustic wave equation in isotropic media.The TTI pseudo-acoustic wave equation is composed of the combination of a pressure wavefield and an auxiliary wavefield and includes many terms of second derivatives and coupled first derivatives.The wave equation in isotropic media requires only the P -wave velocity,while five parameters are required to describe the wave propagation using the TTI pseudo-acoustic wave equation.Third,the wavefield values obtained through numerical modeling with the TTI pseudo-acoustic wave equation may be blown up in areas where the dip or azimuth angles are substantially changed (Crawley et al.,2010).Fletcher et al.(2009)stabilized wave propagation by setting the SV-wave velocity to half of the P -wave vertical velocity;however,this method generates additional energy from the SV-wave,which can produce incorrect reflectors or make the image unclear.Recently,Yoon et al.(2010)addressed the instability of wave propagation by making d equal to E around high symmetry axis gradient spots.In this study,we derive a pure P -wave equation in 2D and 3D TTI media to exclude SV-wave energy in RTM.The spatial frequency-domain dispersion relation obtained from the exact dispersion relations for VTI media derived by Tsvankin (1996)is used to derive the pure P -wave equation in the VTI media (Zhan et al.,2011).Then,the TTI version of the wave equation is obtained by rotating wavenumbers.To obtain a stable solution of the wave equation even in large time steps,we employ the rapid expansion method (REM)to propagate wavefields in time (Pestana and Stoffa,2010).To calculate the spatial derivatives in the wave equation,we select a pseudo-spectral method (PSM)(Kosloff and Baysal,1982;Fornberg,1987)because wave propa-gation incorporated with this method does not incur numerical dispersion,and REM combined with this method can generate a highly accurate solution for wave propagation.In the progression of applying the PSM,we multiply the spatial-frequency domain high-cut filter function with Fourier transformed wavefields at each time step to prevent the wavefield values from being blown up in areas with high gradients of dip or azimuth angles (Zhan et al.,2011).In addition,to accelerate the performance speed of the numerical modeling,we calculate the 2D or 3D Fourier transforms and their inverses using GPUs with CUDA and parallel computing with MPI (Gropp et al.,1999).In addition to the kernel (a function executed in parallel on the GPU device)for FFT,all algorithms required for the RTM are computed on the GPUs.2.Mathematical expression of pure TTI P -wave equation The 3D spatial-frequency domain ðk x ,k y ,k z Þdispersion relation used by Etgen and Brandsberg-Dahl (2009)and Crawley et al.(2010)is expressed as follows:o 2¼v 2p 0ð1þ2e Þðk 2x þk 2y Þþk 2z À2ðe Àd Þðk 2x þk 2y Þk 2z k 2x þk 2y þk 2z !,ð1Þwhere o is the angular frequency,v p 0is the P -wave velocity,and e and d are the Thomsen (1986)parameters.The dispersion relation in Eq.(1)can be applied to the VTI media and can be transformed into the form in TTI media by rotating wavenumber components ðk x ,k y ,k z Þ.The rotated wavenumbers are expressed as follows:^kx ^k y ^k z26643775¼cos y cos j k x þcos y sin j k y þsin y k z Àsin j k x þcos j k y Àsin y cos j k x Àsin y sin j k y þcos y k z 264375,ð2ÞEq.(1)can be rewritten in a rotated coordinate system asÀo 2¼v 2p 0c 1k 2x þc 2k 2y þc 3k 2z þc 4k x k y þc 5k y k z þc 6k z k x þc 7k 4x =k 2r þc 8k 4y =k 2r þc 9k 4z =k 2r þc 10k 2x k 2y =k 2r þc 11k 2y k 2z =k 2r þc 12k 2z k 2x =k 2rþc 13k 3x k z =k 2r þc 14k x k 3z =k 2r þc 15k 3x k y =k 2r þc 16k 3x k y =k 2r þc 17k 3y k z =k 2r þc 18k y k 3z =k 2rþc 19k 2x k y k z =k 2r þc 20k x k 2y k z =k 2r þc 21k x k y k 2z =k 2r 0B B B B B B B B B B B B B B B B B @1C CCC CCC CC C CC C CC C C A ,ð3Þwherec 1¼1þ2e ðsin 2j þcos 2y cos 2j Þ,c 2¼1þ2e ðcos 2j þcos 2y sin 2j Þ,c 3¼1þ2e sin 2y ,c 4¼À2e sin 2y sin 2j ,c 5¼2e sin 2y sin j ,c 6¼2e sin 2y cos j ,c 7¼2ðd Àe Þsin 2y cos 2j ðsin 2j þcos 2y cos 2j Þ,c 8¼2ðd Àe Þsin 2y sin 2j ðcos 2j þcos 2y sin 2j Þ,c 9¼2ðd Àe Þsin 2y cos 2y ,c 10¼0:5ðd Àe Þf sin 2y ðcos 4j þ3Þþ8sin 2y sin 2j cos 2j ð3cos 2y À2Þg ,c 11¼0:5ðd Àe Þf sin 2j ðcos 4y þ3Þþ4cos 2y ðcos 2j À4sin 2y sin 2j Þg ,c 12¼0:5ðd Àe Þf cos 2j ðcos 4y þ3Þþ4cos 2y ðsin 2j À4sin 2y cos 2j Þg ,c 13¼4ðd Àe Þsin y cos y cos j ð2sin 2y cos 2j À1Þ,c 14¼4ðd Àe Þsin y cos y cos 2y cos j ,c 15¼4ðd Àe Þsin 2y sin j cos j ðcos 2j cos 2y þsin 2j Þ,c 16¼4ðd Àe Þsin 2y sin j cos j ðsin 2j cos 2y þcos 2j Þ,c 17¼À4ðd Àe Þsin y cos y sin j ðsin 2j cos 2y þcos 2j Þ,c 18¼4ðd Àe Þsin y cos y cos 2y sin j ,c 19¼4ðd Àe Þsin y cos y sin j ð6sin 2y cos 2j À1Þ,c 20¼4ðd Àe Þsin y cos y cos j ð4sin 2y sin 2j À1Þ,c 21¼4ðd Àe Þsin 2y sin j cos j ð6sin 2y À5Þ:In Eq.(3),y is the dip angle and j is the azimuth ing aFourier transform,we can transform Eq.(3)from the frequency domain to the time domain.When the i o term is substituted by @=@t ,Eq.(3)is changed to the following:@2u ðx ,t Þ@t 2¼v 2p 0c 1k 2x þc 2k 2y þc 3k 2zþc 4k x k y þc 5k y k z þc 6k z k xþc 7k 4x =k 2r þc 8k 4y =k 2r þc 9k 4z =k 2r þc 10k 2x k 2y =k 2r þc 11k 2y k 2z =k 2r þc 12k 2z k 2x =k 2r þc 13k 3x k z =k 2r þc 14k x k 3z =k 2r þc 15k 3x k y =k 2r þc 16k 3x k y =k 2r þc 17k 3y k z =k 2r þc 18k y k 3z =k 2r þc 19k 2x k y k z =k 2r þc 20k x k 2y k z =k 2r þc 21k x k y k 2z =k 2r 0B B B B B B B B B B B B B B B B B @1CC C C C C C C CC C CC C C CC A u ðx ,t Þ,ð4Þwhere u ðx ,t Þis the wavefield at time t .The solution of the 2D TTI pure P -wave equation can be obtained by setting j to 0.In the 2D case,21terms of the spatial derivatives in Eq.(4)can be reduced to 7terms.Y.Kim et al./Computers &Geosciences 52(2013)204–2172053.The solution of the wave equation using REM witha pseudo-spectral methodBy replacing the multiplication of the square of the P-wave velocity and the term of the spatial derivatives in Eq.(4)with the symbolÀF2,the wave equation in Eq.(4)can be written as follows:@2uðx,tÞ@t¼ÀF2uðx,tÞ:ð5ÞThe formal solution to Eq.(5)with two initial conditions ofu0¼uðx,0Þand_u0¼@uðx,tÞ=@t9t¼0is given by the following:uðx,tÞ¼cosðF tÞu0þFÀ1sinðF tÞ_u0:ð6ÞThe wavefields uðx,tþD tÞand uðx,tÀD tÞcan be obtained by setting the t term in Eq.(6)to tþD t and tÀD t,respectively. Adding these two wavefields removes the odd part of the solution,resulting inuðx,tþD tÞþuðx,tÀD tÞ¼2cosðF D tÞuðx,tÞ:ð7ÞBecause the PSM provides optimal spatial accuracy for a given grid size,we select the method to calculate the spatial derivatives with the REM.Based on the PSM,the form of Eq.(7)can be written using the Fourier transform as follows:uðx,tþD tÞ¼2FTÀ1½cosðF D tÞFT½uðx,tÞ Àuðx,tÀD tÞ,ð8Þwhere FT and FTÀ1represent the Fourier transform and its inverse transform,respectively.The cosine operator in Eq.(8)can be expanded by its Cheby-shev expansion for one-step REM as proposed by Kosloff et al. (1989),and the cosine is expanded as follows(Pestana and Stoffa, 2010):cosðF D tÞ¼X Mk¼0C2k J2kðBÞQ2kði xÞ,ð9Þwhere C0¼1and C k¼2for k Z1,9J kðzÞ9¼9z9k=ð2k k!Þ,Q2k is presented asQ0ði xÞ¼1,Q2ði xÞ¼1À2x2,Q4ði xÞ¼1À8x2þ8x4,Q6ði xÞ¼1À18x2þ48x4À32x6,Q8ði xÞ¼1À32x2þ160x4À256x6þ128x8,^Q kþ2ði xÞ¼ðÀ4x2þ2ÞQ kði xÞÀQ kÀ2ði xÞ:ð10ÞIn Eq.(9),J k represents the Bessel function of order k,Q k represents the modified Chebyshev polynomials that are recur-sively obtained from the initial condition of Q0and Q2,and the characters B,x and m represent R D t,F=R and1=R,respectively. The orthogonal polynomial series expansion for the cosine func-tion was presented by Tal-Ezer et al.(1987).For the3D TTI or VTI modeling,the R value is given by the following:R¼p V maxð1þ29e9maxÞffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi1xþ1yþ1zs,ð11Þwhere V max is the highest P-wave velocity in the direction of the symmetry axis,and D x,D y,and D z are the spatial grid spacing in the x,y,and z directions,respectively.M should satisfy the condition of M4R D t.When we usefive Chebyshev polynomial terms,Eq.(9)can be written as follows:cosðF D tÞ¼X Mk¼0C2k J2kðBÞQ2kði xÞ¼C0J0ðBÞQ0ði xÞþC2J2ðBÞQ2ði xÞþC4J4ðBÞQ4ði xÞþC6J6ðBÞQ6ði xÞþC8J8ðBÞQ8ði xÞ¼J0ðBÞþ2J2ðBÞð1À2x2Þþ2J4ðBÞð1À8x2þ8x4Þþ2J6ðBÞð1À18x2þ48x4À32x6Þþ2J8ðBÞÂð1À32x2þ160x4À256x6þ128x8Þð12Þand thefinal equation to perform the numerical modeling can beexpressed as follows:uðx,tþD tÞ¼2½J0ðBÞuðx,tÞþ2J2ðBÞf uðx,tÞÀ2m2FðxÞgþ2J4ðBÞf uðx,tÞÀ8m2FðxÞþ8m4F2ðxÞgþ2J6ðBÞf uðx,tÞÀ18m2FðxÞþ48m4F2ðxÞÀ32m6F3ðxÞgþ2J8ðBÞf uðx,tÞÀ32m2FðxÞþ160m4F2ðxÞÀ256m6F3ðxÞþ128m8F4ðxÞg Àuðx,tÀD tÞ,ð13Þwhere FðxÞ¼FTÀ1½F2FT½uðx,tÞ .4.Pseudo-spectral method with CUDA and MPIWhen the model size for RTM is small enough to implementthe numerical modeling with one GPU,massage passing with MPIis not required in the PSM application.However,the devicememory size of the GPUs is not large enough to implement theactual application on wide-azimuth real exploration data.Inaddition,modeled data for the illumination zone should be storedin a global memory in the forward algorithm when RTM isperformed on a cluster without a blade hard disk in each node.To solve these problems,multiple GPUs and CPU processors areemployed to implement the RTM for one shot.Fig.1displays the algorithm structure of a PSM for obtainingFðxÞin Eq.(13)when four GPU devices are employed to imple-ment the modeling for a shot.Let nx,ny and nz denote the numberof grids in the x,y,and z directions and the symbol x representsthe location of the wavefieldðx,y,zÞ.k and~k areðk x,k y,k zÞandðk x,k y,zÞ,respectively.#1in Fig.1demonstrates the domainpartition for four GPU devices where the wavefields in time tare partitioned vertically into four parts(divided by colors),andeach color represents the subdomain assigned to a GPU device.AGPU device does not need to store wavefields on the total domain,which can implement the actual application on a large-sizedmodel by using many GPUs.The wavefields in the total domain are larger than nxÂnyÂnzbecause the grids in each axis are padded until the number of gridpoints is suitable for a prime factor length FFT(Fig.2(a)).When NGPUs i¼ð0,1,2,...,NÀ1Þare employed,the array of wavefieldsassigned to i-th GPU is expressed as½1:nxfft;1:nyfft;ðnzfft=NÞÃiþ0:5:ðnzfft=NÞÃðiþ1Þþ0:5À1 :Because a GPU has enough wavefields to implement the Fouriertransform in the x and y directions,2D FFT can be performed inevery xy-plane along z directions.In this study,we implement the2D FFT on uðxÞby using complex cuFFT supported by NVIDIA andthen obtain uð~kÞ(shown in#2in Fig.1and Fig.2(b)).To perform the FFT in the z direction,communication amongthe GPU devices is needed to exchange wavefields.The dataexchange between GPUs involves three memory copies:from GPUto CPU,from CPU to CPU,and from CPU to GPU(Micikevicius,2009).In the communication from CPU to CPU(#3-#4)afterthe memory copy is made from GPU to CPU(#2-#3),dataexchange among CPUs is achieved using MPI as follows./*Send wavefields to other processors*/forði¼0;i o N;iþþÞf=Ñme’is my rankÃ=buffer[i]¼uk_tilde[1:nxfft,Y.Kim et al./Computers&Geosciences52(2013)204–217206: Communication among nodes: Multiply pseudo-Laplacian to wavefields : Fourier transform: Inverse Fourier transformFig.1.Diagram of the parallel3D pseudo-spectral modeling when four GPU devices are employed to implement numerical modeling for a shot.The symbol x represents the location of the wavefieldðx,y,zÞ.k and~k areðk x,k y,k zÞandðk x,k y,zÞ,respectively.(For interpretation of the references to color in thisfigure caption,the reader is referred to the web version of this article.)(nyfft/N)*iþ0.5:(nyfft/N)*(iþ1)þ0.5-1,(nzfft/N)*meþ0.5:(nzfft/N)*(meþ1)þ0.5-1]; if(i¼¼me)xzwork[1:nxfft,(nyfft/N)*meþ0.5:(nyfft/N)*(meþ1)þ0.5-1,(nzfft/N)*meþ0.5:(nzfft/N)*(meþ1)þ0.5-1]¼buffer[me];elsesend data in buffer[i]to processor i usingMPI_Bsend;}/*Receive wavefields from other processors*/nrecv¼0;whileðnrecv o NÞfif(nrecv!¼me){receive data from nrecv-th processorusing MPI_Recv and store into buffer[nrecv];xzwork[1:nxfft,(nyfft/N)*meþ0.5:(nyfft/N)*(meþ1)þ0.5-1, (nzfft/N)*nrecvþ0.5:(nzfft/N)*(nrecvþ1)þ0.5-1]¼buffer[nrecv];}Y.Kim et al./Computers&Geosciences52(2013)204–217207nrecv þ¼1;}To facilitate understanding,we also illustrate the manner of data exchange in Fig.2(d).After the memory-copy is made from CPU and GPU (#4-#5),wavefields u ðk Þcan be obtained by performing 1D FFT in the z direction and are then stored in the device memory of each GPU device.The array of wavefields u ðk Þassigned to i -th GPU is expressed as½1:nxfft ;ðnyfft =N ÞÃi þ0:5:ðnyfft =N ÞÃði þ1Þþ0:5À1;nzfft ;and is also displayed in Fig.2(c).The processes from #7to #12are the inverses of the processes that occur from #1to #6.Whereas the processes from #1to #6are for preparing a PSM,the processes from #7to #12constitute the main routines for calculating the derivatives in the spatial directions usingtheFig.2.The structure of the prime numbered grids.(a)and (b)are the structures before and after the memory exchange,respectively,between the CPUs and GPUs in the progressions from #1to #6in Fig.1.(c)presents the manner of exchange.Y.Kim et al./Computers &Geosciences 52(2013)204–217208PSM.To implement the REM,we must calculate FðxÞin Eq.(13), which is expressed in detail as follows:FðxÞ¼v2p0c1FTÀ1½k2xFT½uðx,tÞþc2FTÀ1½k2yFT½uðx,tÞþc3FTÀ1½k2zFT½uðx,tÞþc4FTÀ1½k x k y FT½uðx,tÞ þc5FTÀ1½k y k z FT½uðx,tÞþc6FTÀ1½k z k x FT½uðx,tÞþc7FTÀ1½ðk4x=k2rÞFT½uðx,tÞþc8FTÀ1½ðk4y=k2rÞFT½uðx,tÞþc9FTÀ1½ðk4z=k2rÞFT½uðx,tÞþc10FTÀ1½ðk2xk2y=k2rÞFT½uðx,tÞþc11FTÀ1½ðk2yk2z=k2rÞFT½uðx,tÞþc12FTÀ1½ðk2zk2x=k2rÞFT½uðx,tÞþc13FTÀ1½ðk3xk z=k2rÞFT½uðx,tÞþc14FTÀ1½ðk x k3z=k2rÞFT½uðx,tÞþc15FTÀ1½ðk3xk y=k2rÞFT½uðx,tÞþc16FTÀ1½ðk x k3y=k2rÞFT½uðx,tÞþc17FTÀ1½ðk3yk z=k2rÞFT½uðx,tÞþc18FTÀ1½ðk y k3z=k2rÞFT½uðx,tÞþc19FTÀ1½ðk2xk y k z=k2rÞFT½uðx,tÞþc20FTÀ1½ðk x k2yk z=k2rÞFT½uðx,tÞþc21FTÀ1½ðk x k y k2z=k2rÞFT½uðx,tÞB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB@1C CC CC CC CC CC CC CC CC CC CC CC CC CC CC CC CC CC CC CC CC CC CC CC CC CC CC A¼v2p0X21i¼1c i FTÀ1½L iðkÞÁuðkÞ :ð14ÞBecause Eq.(14)consists of21terms of spatial derivatives,the processes from#7to#12should be repeated21times.Each GPU device calculates HðkÞ¼L iðkÞÁuðkÞin the subdomain assigned to each(#7in Fig.1)and performs the inverse Fourier transform with cuFFT in the z direction to obtain H ið~kÞ.Because data exchange should be required to take the inverse Fourier transform to H ið~kÞin the xy-plane,data communication among CPUs should be performed with the MPI;its computational algorithm can be summarized as follows./*Send wavefields to other processors*/forði¼0;i o N;iþþÞf=Ã’me’is my rankÃ=buffer[i]¼uk_tilde[1:nxfft,(nyfft/N)*meþ0.5:(nyfft/N)*(meþ1)þ0.5-1,(nzfft/N)*iþ0.5:(nzfft/N)*(iþ1)þ0.5-1];if(i¼¼me)xzwork[1:nxfft,(nyfft/N)*meþ0.5:(nyfft/N)*(meþ1)þ0.5-1, (nzfft/N)*iþ0.5:(nzfft/N)*(iþ1)þ0.5-1]¼buffer[me];elsesend data in buffer[i]to processor i using MPI_Bsend;}/*Receive wavefields from other processors*/nrecv¼0;whileðnrecv o NÞfif(nrecv!¼me){receive data from nrecv-th processor using MPI_Recvand store into buffer[nrecv];xzwork[1:nxfft,(nyfft/N)*nrecvþ0.5:(nyfft/N)*(nrecvþ1)þ0.5-1,(nzfft/N)*meþ0.5:(nzfft/N)*(meþ1)þ0.5-1]¼buffer[nrecv];}nrecvþ¼1;}After the completion of data exchange among the CPUs and memory copy from the CPUs to the GPUs,the wavefields on the subdomain assigned to a GPU are taken from the inverse trans-form to each xy-plane along the z direction(shown in#11-#12 in Fig.1).Then,by multiplying the coefficient c i by H iðxÞ,each GPU stores the values of c i FTÀ1ðL iðkÞÁuðkÞÞin Eq.(14)in the device memory.Finally,by repeating steps#7to#1221times, we can calculate FðxÞin Eq.(14)and obtain the wavefields in the next time step uðx,tþD tÞin Eq.(13).Fig.3shows the2D algorithm with the GPUs and the MPI.The 2D algorithm can be obtained by excluding the wavefields in the x direction on the3D algorithm because the data in the x direction are not shared among processors.In addition,when we perform 2D TTI modeling,the processes from#7to#12in Fig.3can be reduced to one-third of the repetitions used in the3D algorithm. To compare wavefields obtained by the TTI P-wave equation based on our proposed algorithm and those obtained by the pseudo-acoustic TTI wave equation suggested by Fletcher et al. (2009),we display2D and3D wavefield snapshots in Fig.4.The P-wave vertical velocity in the medium is constant at2000m=s. The Thomsen parameter E and d are0.24and0.1,respectively. The tilt angle isfixed to45J in the2D and3D cases,and the azimuth angle is set to45J in the3D case.The wave snapshots in Fig.4(a)–(d)are obtained using the pseudo-acoustic TTI wave equation based on a second-order time-domain eighth-order space-domainfinite difference stencil.The SV-wave velocity is set to zero in Fig4(a)and(b).Fig.4(a)and(b)demonstrates the diamond shape of the SV wavefront.In the P-wave RTM imple-mentation,the SV-waves may act as artifacts that have a harmful effect on the quality on migration images.When we set the SV-wave velocity to0,Fletcher et al.(2009)showed that wavefields in areas with a high gradient of dip angles can be blown up.To stabilize the wavefields,Fletcher et al.(2009)set the SV-wave velocity to half of the P-wave vertical velocity when a high contrast existed in the dipfield.However,as shown in Fig.4(c)and4(d),the drawback of this approach is that additional S-wave noise is generated.Snapshots presented in Fig.4(e)and (f)are generated by our proposed algorithm.Fig.4(e)and(f) indicates that the S-waves are completely removed and that only P-wave wavefronts are clearly observed.5.Algorithm of reverse time migrationWhen the cross-correlation imaging condition is employed in the RTM,the migration image at the k-th node can be expressed as follows:fk¼Xnshoti¼1Z T maxS kðtÞR kðT maxÀtÞd t,ð15Þwhere T max is the maximum recording time,i is the shot number,S k(t)is the source wavefield,R kðT maxÀtÞis the backward-propagated receiver wavefield,and f k is the image at the k-th node.The source wavefield S k(t)can be obtained by propagating a mathematical function,e.g.,a Ricker wavelet,as a source signature forward in time.The receiver wavefield R k(t)Y.Kim et al./Computers&Geosciences52(2013)204–217209。
地震定位研究综述概要
防灾科技学院毕业设计(论文、综合实践报告)结论从数学上讲,地震定位问题的实质在于求目标函数的极小值。
各种定位方法产生于对目标函数的构造、处理,以及求极小值方法的不同。
影响地震定位精度的主要因素有:台网布局,震相识别,到时读数,地壳结构等。
在数值计算中,常遇到下列问题:走时的计算,偏导数的计算,方程的反演求解等。
由于台网分布在地表,给深度定位带来一定的困难。
各种定位方法正是针对其中的某几个问题而设,各有优、缺点。
相对定位所得的震源相对位置精度较高。
对于主事件,可以利用改进后的经典方法进行单事件定位。
二者结合将可以得到较好的定位结果。
JHD 方法中引入的台站校正过于简单,不足以反映地壳的复杂结构;而 SSH 方法中的三维速度模型会带来巨大的运算量。
如果我们能够构造一种介于二者之间的校正参数,比如将台站校正作为有方向的矢量,进行联合反演,可能效果更好。
在 DDA 方法中,当事件对i, j 相距较近时,可以将(23式化简,反演得到 i, j 的相对距离。
同时我们可以选取较少的事件,用联合反演进行绝对定位。
将二者结合可以减少运算量,提高定位效率。
致谢本文是在陈晓非老师的悉心指导下完成的。
陈老师优秀的科学修养,深厚的数理功底,严谨的治学态度都给我留下了极其深刻的印象,也成了我努力奋斗的榜样。
本文同样凝聚了陈老师的心血,仅此向陈老师表示深深的谢意。
周仕勇博士后以其丰富的理论背景和实践经验,对本文提出了建设性意见并提供了诸多及时的信息。
张海明、张伟、邹最红、曹军等师兄师姐手把手地领我入门,令我受益匪浅。
均在此一并致谢! 参考文献 [1] 傅淑芳, 刘宝诚. 地震学教程[M]. 北京:地震出版社,1991,447-480. [2] Geiger L. Probability method for the determination of earthquake epicenters from arrival time only[J]. Bull.St.Louis.Univ, 1912, 8: 60-71. [3] Lee W H K, J C Lahr. HYPO71: A computer program for determining hypocenter, magnitude, and firs t motion pattern of local earthquakes[J]. U.S.Geol.Surv. Open-File Rept, 1975, 75-311. [4] Klein F W. Hypocenter location program HYPOINVERSE Part I: Users guide to versions 1,2,3 and 4[J]. U.S.Geol.Surv. Open-File Rept, 1978, 78-694.防灾科技学院毕业设计(论文、综合实践报告) [5] Lienert B R,Berg E, Frazer L N. Hypocenter: An earthquake location method using centered, scaled, and adaptively damped least squares[J]. Bull.Seism.Soc.Am, 1986,76(3: 771-783 . [6] Nelson G D, JohnE Vidale. Earthquake locations by 3-D finite-difference travel times[J].Bull.Seism.Soc.Am, 1990, 80(2: 395-410. [7] 赵仲和. 多重模型地震定位程序及其在北京台网的应用[J]. 地震学报,1983,5(2:242—254. [8] 吴明熙, 王鸣, 孙次昌, 等.1985 年禄劝地震部分余震的精确定位[J].地震学报,1990,12(2:121—129. [9] 赵卫明, 金延龙, 任庆维. 1988 年灵武地震序列的精确定位和发震构造[J]. 地震学报,1992,14(4:416 —422. [10] Prugger A F, Gendzwill D J. Microearthquake location: A nonlinear approach that makes use of a simplex stepping procedure[J].Bull.Seism.Soc.Am, 1988, 78(2: 799-815. [11] Douglas A. Joint epicenter determination[J]. Nature, 1976, 215: 45-48. [12] Dewey J. Seismicity and tectonics of western V enezuela[J]. Bull.Seism.Soc.Am, 1972, 62(6: 1711-1751. [13] Pavlis G, Booker J R. Progressive multiple event location (PMLE[J]. Bull.Seism.Soc.Am,1983,73(6:1753-1777. [14] Pujol J. Comments on the joint determination of hypocenter and station corrections[J]. Bull.Seism.Soc.Am, 1988, 78(3:1179-1189. [15] Pujol J. Joint event location – The JHD technique and applications to data from local seismic networks[A]. In: Thurber C, N Rabinowitz. Advances in seismic event location[C]. Kluwer Academic Publishers, 2000,163-204. [16] 王椿镛, 王溪莉, 颜其中. 昆明地震台网多事件定位问题的初步研究[J]. 地震学报,1993,15(2: 136— 145. [17] Crosson R S. Crustal structure modeling of earthquake data,1,Simultameous least squares estimation of hypocenter and velocity parameters[J]. J.Geophys.Res,1976,81(17:3036-3046. [18] Aki K, Lee W H K. Determination of three-dimensional velocity anomalies under a seismic array using first P arrival times from local earthquakes, part 1 : A homogeneous initial model[J]. J.Geophys.Res,1976,81(23:4381-4399. [19] Aki K, et al. Determination of the three-dimensional seismic structure of the lothosphere[J]. J.Geophys.Res,1977, 82(2:277-296. [20] Pavlis G, Booker J R. The mixed discrete-continuous inverse problem : Application of the防灾科技学院毕业设计(论文、综合实践报告) simultaneous determination of earthquake hypocenters and velocity structure[J]. J.Geophys. Res, 1980,85(B9:4801-4810.[21] Spencer C, Gubbins D. Travel-time inversion for simultaneous earthquake locationand velocity structure determination in laterally varying media[J].Geophys.J.Roy.Astr.Soc,1980, 63(1:95-116. [22] 赵仲和. 北京地区地震参数与速度结构的联合测定[J]. 地球物理学报,1983,26(2:131—139. [23] 刘福田. 震源位置和速度结构的联合反演(I)——理论和方法[J]. 地球物理学报, 1984,27(2: 167 —175。
航空专业术语缩写单词
电池
Battery
BCD
十进制二进制表示法
Binary Coded Decimal
BFO
差频振荡器
Beat Freque ncy
BIT
内置测试
Built In Test
BITE
内置测试装置
Built In Test Equipme nt
BL
尾线
Buttock Line
BNK
倾斜
Ba nk
BNR
高度
Altitude
ALTN
交替
Alternate
ALTS
高度选择
Altitude Select
ALTSEL
咼度预选
Altitude Preselect
AM
调幅
Amplitude Modulation
Aபைடு நூலகம்E
调幅等效
Amplitude Modulati on Equivale nt
AMM
飞机维护手册
Aircraft Main tera nee Manual
DIR
直接
Direct
DISC
断开
Disc onnect
DIST
距离
Dista nce
DME
测距机
Dista nce Measuri ng Equipme nt
DMEHLD
测距机保持
DME Hold
DN
放下
Dow n
DOT
运输部门
Departme nt Of Tran sport
DPDT
双刀双掷开关
航空专业术语缩写单词
A
A/C
飞机
Aircraft
存在位置误差时运动多平台时差定位CRLB分析
存在位置误差时运动多平台时差定位CRLB分析骆卉子;曲长文【摘要】存在平台位置测量误差时,已有研究未涉及运动多平台时差(TDOA)连续定位的性能评价.为此,选择克拉美-罗限(CRLB)作为对目标定位性能的评价指标,将不同时刻的运动多平台真实位置向量构成扩维向量后由CRLB定义得出了其通用计算式,并根据运动多平台TDOA连续定位的特点,推导了适合此应用场景的具体计算式.仿真结果表明了所推导的CRLB能有效用于上述场景中的定位性能评价,对近场及远场目标都需要在系统技术指标及定位算法设计等方面考虑平台位置测量误差的影响.%In moving multi-platform time-difference-of-arrival (TDOA) continuous localization,precise platform locations are often not available in practice.The localization performance evaluation for such scene is not researched.Aiming at this,the Cramér-Rao lower bound(CRLB) is chosen as the evaluation index for the target localization.A augmented vector is composed using all true platform positions at different instants and the common calculation formula for the CRLB is got by its definition.According to the characteristics of the moving multi-platform TDOA continuous localization,the specific calculation formula is derived.Simulation results indicate the effectiveness of the derived index for the performance evaluation in the aforementioned scene.The influence of the platform's position error should be considered in system technical index and localization algorithm design for both the near-field target and the far-field target.【期刊名称】《现代防御技术》【年(卷),期】2017(045)002【总页数】5页(P130-133,155)【关键词】多平台;定位;平台位置误差;时差;克拉美-罗限;仿真【作者】骆卉子;曲长文【作者单位】海军航空工程学院电子信息工程系,山东烟台264001;海军航空工程学院电子信息工程系,山东烟台264001【正文语种】中文【中图分类】TN953+.7;TN958.97现代战争中战场电磁环境复杂,分布着各种电磁辐射源,确定它们的位置来获取完整的战场态势对战争胜负至关重要。
GPS词汇
《卫星定位技术与方法》双语教学词汇手册AAFV: Ambiguity Function Value: 模糊度函数AS—anti-spoofing:反电子欺骗技术ATI(International Atomic Time):原子时ambiguity resolution theory--模糊度分解理论all weather:全天候antenna phase center error:天线相位中心偏差almanac:卫星历书数据amplitude: 振幅absolute positioning: 伪距绝对定位approximate value: 近似值astrogeodetic network:天文大地网argument of ascending node: 升交距角argument of perigee:近地点角距astronomical observatory:天文台ascending node:升交点azimuth and elevation:方位角与高度角Bbase station: 基站broadcast ephemeris:广播星历CCDMA—code division multiple access 码分多址CHAMP—challenging mini-satellite payload 挑战小卫星有效荷载CIO—conventional international origin:协定原点CODE—center for orbit determination in Europe 欧洲轨道确定中心CORS—continuously operating reference station 连续运行参考站CRF—celestial reference frame 天球参考架carrier signal:载波信号carrier phase observable:载波相位观测量celestial navigation:天体导航celestial polar and celestial axis:天极与天轴celestial equator:天球赤道celestial rectangle coordinate:天球直角坐标central meridian:中央子午线celestial spheric coordinate: 天球球面坐标chipping rate:码率Covariance: 协方差阵chipping width:码元宽度clock error:钟差cofactor matrix: 协因数阵constellation:星座compass navigation:磁针(罗盘仪)导航choke ring antenna: 扼流圈天线cosine-theorem:余弦定律control segment:监控部分Conventional inertial reference system—CIRS/celestial fixed frame:协议惯性系Conventional terrestrial reference system—CTRS/earth fixed frame:协议地固系coarse/acquisition code:(C/A码)测距粗码conventional celestial spheric coordinate system: 协议天球坐标系cycle slip detecting: 周跳探测DDGPS—differential GPS 差分GPSDLL—delay lock loop 延迟锁定环DMA—defense mapping agency 国防制图社DoD-Department of Defence:美国国防制图局DoT—department of transportation 运输部Data link : 数据链damping factor: 为衰减因子design matrix:设计矩阵Direction cosine: 方向余弦GDOP(Geometric DOP):几何精度因子diffraction:衍射dispersive medium: 散射介质Dilution of Precision—DOP: 精度因子double difference operator: 双差运算符double-differenced measurement: 双差观测量Doppler positioning : 多普勒定位dynamic noise:动态噪声EEGM—earth gravitational model 地球重力场模型EGNOS—European geostationary navigation overlay service 欧洲静地卫星导航服务ERS—earth orientation parameters 地球旋转参数ellipsoid parameters and geodetic origin:椭球参数和大地原点ecliptic plane:黄道eccentric anomaly:偏近点角encrypted P-code:对P码实施加密eccentricity:偏心率error equation :误差方程extra path length :多余路径FFDMA—frequency division multiple access 频分多址FGCC—federal geodetic control committee 联邦大地测量控制委员会FOC—full operational capability 完全运行能力FTP—file transfer protocol 文件传输协议Fast Ambiguity Resolution Approach —FARA: 快速模糊度分解法feedback shift register:反馈移位寄存器float solution:浮点解GGBAS—ground-based augmentation system 地基增强系统GCS-ground control system:地面控制站GEO—geostationary orbit (satellite) 地球静止轨道卫星GIM—global ionosphere map 全球电离层图GLONASS—global navigation satellite system全球导航卫星系统(俄罗斯)GNSS-- global navigation satellite system 全球导航卫星系统GPS—全球定位系统Gauss projection:高斯投影geocentric coordinate:地心坐标geocentric coordinate):地心坐标geomagnetic longitude :地磁经度general relativity:广义相对论geoid undulation:大地水准面差距Greenwich prime meridian:格林尼制子午线Greenwich mean meridian:格林尼治平均子午面group velocity:群速度HHDOP(Horizontal DOP):平面位置精度因子hand-over word—HOW交换码height abnormal:高程异常hyperbolic positioning: 双曲线定位IIAG—international association of geodesy 国际大地测量协会IAT—international atomic time 国际原子时IAU—international astronomical union 国际天文联合会IERS—international earth rotation service 国际地球旋转服务IGS—international GPS service (for geodynamics) 国际GPS服务ILS—instrument landing system 仪表着陆系统INMARSAT—international maritime satellite (organization) 国际海事卫星组织INS—inertial navigation system 惯性导航系统IOC—initial operational capability 初步运行能力ION—institute of navigation 导航学会ITRF—international terrestrial reference frame 国际地面参考架ITS—intelligent transportation system 智能运输系统ITU—international telecommunication union 国际无线通讯协会IUGG—international union for geodesy and geophysics 国际大地测量与地球物理联合会IWV—integrated water vapor 积分水汽IERS—international earth rotation service:国际地球自转服务组织inclination:卫星轨道倾角iron-spheric delay error:电离层延时误差inertial navigation:惯性导航initialization of ambiguity:模糊度初始化ionospheric refraction: 电离层折射Integer Ambiguity:整周模糊度Iono-free Observable:消电离层观测量JJD--Julian date 儒略日JPS—jet propulsion laboratory 喷气推进实验室KKeplerian parameterKalman filter : 卡尔曼滤波法Krasovsky’s ellipsoid:克拉索夫斯基椭球元素LLAAS—local area augmentation system 局域增强LEO—low earth orbit (satellite) 低轨地球卫星LORAN—long-range navigation (system) 长距离导航系统leap second:跳秒Least Squares Adjustment:最小二乘平差Linearized observation equation: 伪距观测方程的线性化longtitude of ascending node:升交点经度Long Range Navigation-LORAN:远程无线电导航系统local-level system or east-north-up 局部水平坐标系local meridian当地子午线MMEDLL—multipath estimating delay lock loop 带多路径估计的延迟锁定环MIT—Massachusetts institute of technology 麻省理工学院MLS—microwave landing system 微波着路系统MT(Mean Time):平太阳时major radius:长半径mean anomaly at reference time:参考时刻的平近点角mean anomaly:平近点角mean angle between ecliptic and equator:平黄赤交角mean polar:平地极mean yellow sea level:黄海平均海水面meridian:子午线multipath:多路径multi-polynomial fitting: 多项式拟合法multipath estimating delay lock loop—MEDLL: 多路径估计性能的锁相环。
建筑场地地震安全评价
工程场地地震安全性评价
场地地震工程地质条件及岩土工程勘察
• 勘察任务
根据实际需要划分对建筑有利、不利和危险旳地段, 提供建筑场地类别和地震地质灾害(如滑坡、倒塌、 液化和震陷等)评价。
• 工作内容
场地工程地质条件调查 场地钻探 场地岩土体物理力学特征测试 地震地质灾害勘查
工程场地地震安全性评价
工程场地地震安全性评价
建筑场地类别划分
• 以土层等效剪切波速和场地覆盖层厚度为根据。
各类建筑场地旳覆盖层厚度(m)
等效剪切波速
Vse (m/s)
Ⅰ
Vse >500
0
500≥ Vse >250
<5
250 ≥ Vse >140
<3
Vse ≤140
<3
场地类别
Ⅱ
Ⅲ
≥5 3~50 3~15
>50 18~80
• 地震影响系数
∵ G = mg,m为建筑物质量, g为重力加速度
∴ F = G = mg 对照牛顿第二定律: F = ma,a为水平地震加速度
有
g = a
即பைடு நூலகம்
=a / g
可见,所谓地震影响系数,就是地震加速度与重力加速度之比。
工程场地地震安全性评价
• 地震影响系数
建筑构造旳地震影响系数应根据烈度、 场地类别、设计地震分组和构造自振 周期以及阻尼比拟定。
wave velocity
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the frist time i英语作文
the frist time i英语作文The first time I...第一次我...II. The AnticipationA wave of excitement and nervousness washed over me as I anticipated the moment. It was my very first time engaging in an activity that had always captivated my imagination, yet remained uncharted territory. My heart pounded in my chest like a drumroll, announcing the imminent arrival of a new experience.一阵兴奋与紧张交织的浪潮在我心中翻涌,预示着那一刻的到来。
这是我首次涉足一项始终吸引我想象却又未曾涉足的活动。
心跳如激昂的鼓点,在胸腔内轰鸣,宣告崭新体验即将来临。
III. The EncounterFinally, the day arrived. With trembling hands and a mixture of trepidation and enthusiasm, I stepped into the unknown. The sights, sounds, and sensations assailed my senses, each detail etching itself indelibly onto my memory. The air crackled with anticipation, and I felt as though I was stepping into a world entirely different from my own.终于,那一天到来了。
因为打扫卫生去食堂很晚了的英语作文
全文分为作者个人简介和正文两个部分:作者个人简介:Hello everyone, I am an author dedicated to creating and sharing high-quality document templates. In this era of information overload, accurate and efficient communication has become especially important. I firmly believe that good communication can build bridges between people, playing an indispensable role in academia, career, and daily life. Therefore, I decided to invest my knowledge and skills into creating valuable documents to help people find inspiration and direction when needed.正文:因为打扫卫生去食堂很晚了的英语作文全文共3篇示例,供读者参考篇1Cleaning Duties: A Disastrous Delay for DinnerAs a student living on campus, mealtimes at the dining hall are a sacred ritual. After a long day of classes, seminars, and study sessions, the chance to refuel with a hot meal is somethingI eagerly anticipate. However, on this particular evening, my journey to the dining hall was met with a series of unfortunate events that left me feeling famished and frustrated.It all began with the dreaded cleaning rotation schedule. As a responsible member of our dormitory community, each student is assigned a weekly cleaning duty to maintain the shared spaces. This week, it was my turn to tackle the common room, a task that I had initially brushed off as a mere inconvenience. Little did I know, it would turn into a battle against grime and clutter that threatened to derail my dinner plans.Armed with a mop, bucket, and an arsenal of cleaning supplies, I stepped into the common room with a sense of determination. The room was in a state of disarray, with empty soda cans littering the floor, crumbs scattered across the couches, and a thick layer of dust coating the shelves. It was a war zone of untidiness, and I was the lone soldier tasked with restoring order.As I surveyed the chaos, I couldn't help but wonder how a group of supposedly intelligent individuals could let the common room deteriorate to such a sorry state. Didn't they understand the importance of maintaining a clean and hygienicliving environment? Apparently not, as evidenced by the scattered remnants of late-night study sessions and impromptu movie marathons.Undeterred, I rolled up my sleeves and dove into the cleaning frenzy. I started by gathering the discarded cans and wrappers, cursing under my breath as I uncovered a few suspicious stains on the carpet. Next, I tackled the couches, meticulously vacuuming every nook and cranny to rid them of the crumbs that had accumulated over the week.As I moved on to the shelves, I couldn't help but marvel at the sheer variety of knick-knacks and random objects that had found their way onto the shelves. From outdated textbooks to forgotten board games, it was clear that the common room had become a repository for abandoned possessions. Carefully dusting each item, I couldn't resist the urge to snoop, wondering about the stories behind each forgotten treasure.Just when I thought I was making progress, I encountered a new challenge: the kitchen area. The sink was overflowing with dirty dishes, and the countertops were sticky with spilled drinks and remnants of late-night snacks. It was a scene straight out of a horror movie, and I couldn't help but shudder at the thought of the potential health hazards lurking beneath the grime.Undaunted, I tackled the kitchen with a vengeance, scrubbing every surface until it gleamed. As I worked, I couldn't help but wonder how my fellow students could justify leaving such a mess behind. Didn't they realize that someone else would have to clean up after their carelessness?By the time I had finished cleaning the common room, I was exhausted, sweaty, and more than a little irritated. I had spent hours toiling away, sacrificing my evening to restore order to our shared living space. As I glanced at the clock, I realized with a sinking feeling that I had missed the prime dinner hours at the dining hall.Dejected, I trudged towards the dining hall, my stomach growling in protest. As I approached the entrance, I couldn't help but notice the dwindling crowd of students filtering out, their faces glowing with satisfaction from a hearty meal. I felt a pang of envy, knowing that my prospects for a hot, freshly prepared dinner were rapidly diminishing.Upon entering the dining hall, my fears were confirmed. The once-bountiful buffet lines had been reduced to a few scraggly remnants, with wilted vegetables and dry, overcooked meats languishing under the heat lamps. Resigned to my fate, I cobbledtogether a meager plate of leftovers, trying to ignore the pangs of hunger that gnawed at my stomach.As I sat down at an empty table, picking at my lackluster meal, I couldn't help but reflect on the injustice of it all. Here I was, a dedicated student who had spent hours ensuring the cleanliness and comfort of our living environment, and yet I was being punished with a subpar dining experience.In that moment, I vowed to advocate for a more equitable system of cleaning responsibilities. Perhaps we could implement a rotating schedule, ensuring that no single student was burdened with the task of cleaning the entire common room. Or maybe we could incentivize cleanliness by offering rewards or privileges to those who consistently maintained their living spaces.Whatever the solution, one thing was clear: the current system was flawed, and it was up to us, the student body, to initiate change. As I finished my disappointing dinner, I couldn't help but feel a sense of determination bubbling within me. No longer would I silently accept the indignities of missed meals and subpar dining experiences. From that day forward, I would be a champion for cleanliness, accountability, and fair treatment for all students.With a renewed sense of purpose, I cleared my plate and headed back to my room, already plotting my next move. The battle for a clean living environment and a satisfying dining experience had only just begun.篇2It was one of those dreaded days when I had been assigned cleaning duty after classes. Don't get me wrong, I understand the importance of maintaining a tidy learning environment, but the prospect of scrubbing toilets and mopping floors was far from appealing. As I begrudgingly made my way to the designated area, I couldn't help but fantasize about the delectable treats awaiting me in the cafeteria – the aroma of freshly baked pastries, the sizzle of the grill, and the tantalizing array of culinary delights. Little did I know that my encounter with the mop and bucket would lead to an adventure of epic proportions, one that would test my resilience and teach me invaluable lessons about life.As I entered the restroom, the overwhelming stench of industrial-strength cleansers assaulted my nostrils, instantly dampening my enthusiasm. Donning the trusty pair of rubber gloves, I tackled the tasks with a newfound determination, fueled by the promise of a satisfying meal at the end of my ordeal. Scrub, rinse, repeat – the mantra echoed in my mind as Imeticulously worked my way through each stall, leaving no surface untouched.Just when I thought the worst was over, a sudden cry of distress pierced the air. Emerging from one of the cubicles, a fellow student clutched her backpack, her face contorted in a mixture of horror and disbelief. Apparently, her prized possession – a brand-new laptop – had taken an unintentional dive into the depths of the toilet bowl. Without a second thought, I sprang into action, plunging my hands into the murky waters to retrieve the waterlogged device. Amidst the chaos, I couldn't help but wonder if the grilled cheese sandwiches in the cafeteria would still be warm by the time I made it there.After ensuring that the traumatized student was on her way to the IT department, I turned my attention back to the task at hand. The floors beckoned, their tiles glistening with a layer of grime that had accumulated over countless foot traffic. Arming myself with the trusty mop, I embarked on a mission to restore the hallways to their former glory, my mind wandering to the tantalizing prospect of a heaping plate of spaghetti bolognese.As I meticulously worked my way through the corridors, the hands of the clock seemed to mock me, ticking away the precious minutes that separated me from my long-awaited meal.With each swipe of the mop, I envisioned the steam rising from a piping hot cup of cocoa, its rich aroma filling my senses.Finally, after what felt like an eternity, I emerged victorious, the last droplet of dirty water vanquished from the floors. Exhausted yet triumphant, I peeled off my gloves and made a beeline for the cafeteria, my stomach rumbling in eager anticipation.However, upon arrival, the once-bustling cafeteria had transformed into a desolate wasteland, devoid of the tantalizing aromas and mouth-watering displays that had fueled my motivation throughout the ordeal. The counters lay bare, the warmers cold and empty, and the only sound that greeted me was the gentle hum of the refrigerators. My heart sank as the realization dawned upon me – I had missed the cafeteria's operating hours by a mere few minutes.As I slumped into a chair, a wave of disappointment washed over me. All those hours of scrubbing, mopping, and retrieving wayward laptops from toilet bowls, all for naught. Yet, as I sat there in the quiet cafeteria, a profound realization began to take shape.In that moment, I understood that life is not just about the destination, but about the journey itself. The challenges we face,no matter how mundane or daunting, shape us into the individuals we aspire to become. The satisfaction of a job well done, the sense of camaraderie in helping others, and the resilience forged through adversity – these are the true rewards that transcend any fleeting pleasure derived from a meal.As I bid farewell to the empty cafeteria, a newfound appreciation for the seemingly insignificant moments in life filled my heart. The next time I found myself assigned to cleaning duty, I vowed to approach the task with a renewed sense of purpose, knowing that the lessons learned would nourish my soul far more than any culinary delight ever could.From that day forward, I embraced the unexpected detours and roadblocks that life threw my way, recognizing them as opportunities for growth and self-discovery. And who knows? Perhaps the next time I found myself running late to the cafeteria, I might just stumble upon an adventure even more extraordinary than the one I had just experienced.篇3Being Late to the Cafeteria After Cleaning DutyMan, I really hate it when I get stuck with cleaning duty at school. Don't get me wrong, I know it's important to keep ourclassrooms and hallways tidy, but it always makes me late for lunchtime in the cafeteria. And you do not want to be the last student in line when the lunch ladies are dishing out the food.Let me set the scene for you. It was last Wednesday, and Mr. Hendricks had assigned me and three other students cleaning duty after classes. I honestly think he just picks names out of a hat half the time for these chores. But whatever, it is what it is.The bell rang at 3:15pm and the rest of my classmates practically stampeded out of the room, leaving me, Jake, Emily and Samantha stuck there with the cleaning supplies. I've never understood how they can make such a mess just from sitting at their desks? There were crumpled up papers, pencil shavings, and discarded notebook sheets all over the place."Alright guys, let's just get this done quickly so we can get to the cafeteria before they run out of the good stuff," I said, trying to motivate the team. Jake just grunted, Emily rolled her eyes, and Samantha was already sweeping up a pile of debris.We split up the duties - Emily and I wiped down all the desks and chairs, Jake vacuumed the floor, and Samantha swept up and emptied the trash cans. For the first little while, we all worked in silence, focusing on just getting it all done.But then Jake, always the class clown, started messing around with the vacuum, making inappropriate slurping noises as he pushed it across the floor. I couldn't help but laugh, even though it was pretty immature. Emily was not amused though."Do you mind?" she huffed at Jake. "Some of us actually want to get to the pizza line before it's all gone!""Relax, Em," Jake replied with a smirk. "As if you actually eat anything other than salad for lunch anyway."Emily's face went red with anger and she looked like she was about to explode at him. Sensing the tension, I quickly tried to diffuse the situation."Hey now, no need to fight guys," I said, raising my hands peacefully. "We're almost done here anyway. Why don't we just power through and then book it to the cafeteria?"Samantha, always the reasonable one, chimed in. "He's right. We'll get there faster if we all just cooperate."Jake shrugged his shoulders and Emily seemed to calm down a bit. We managed to finish up the cleaning without any further drama after that. But by the time we had put all the supplies away and locked up the classroom, it was already3:45pm. The lunch period started at 3:30pm and went until4:15pm, so we were definitely behind schedule."Aw man, we're gonna miss all the good stuff!" Jake whined as we hurried down the hallway."Well whose fault is that?" Emily shot back, giving him a look. Jake just rolled his eyes.I was hoping we'd at least get to the cafeteria while they were still serving the main hot lunch entrees. The taco bar, hamburgers, and soup-and-salad options were always the first to go. If we were too late, we'd be stuck with just a sandwich or pre-packaged snacks from the side bins.We reached the cafeteria doors and I held my breath, hoping there weren't already massive lineups. But my heart sank when I saw how crowded it already was inside. Practically every table was full, and there were long snaking lineups for all the food stations."Aw, you've got to be kidding me!" Jake groaned. "This is gonna take forever.""Maybe if someone hadn't been messing around and making jokes, we could have gotten here sooner," Emily grumbled, shooting Jake another dirty look.Samantha and I exchanged a glance, both hoping those two wouldn't start bickering again. But we didn't have time to worry about that. We had to get our place in line before there was nothing left!We decided to split up to maximize our chances of getting decent food options. Jake and I joined the lineup for the taco bar, while Emily and Samantha went for the soup-and-salad line. At least this way we'd be able to get something from two different stations.The taco line seemed to be moving at a relatively decent pace, thank goodness. But Jake and I had cut it so close that there were only a few small portions of ground beef left in the warming tray when we finally made it to the front. I requested a large helping to split onto both our trays, while Jake piled on tons of shredded cheese, salsa and other toppings to make his share seem more substantial.Once we had our tacos assembled, we looked around for a place to sit and spotted Emily and Samantha already at a table, eating some vegetable soup and side salads. We squeezed in across from them, grateful to have at least gotten something moderately nutritious on our trays."Wow, is that all you guys got?" Emily asked, wrinkling her nose as she looked at our sad little tacos."Hey, beggars can't be choosers," Jake replied, already shoveling the food into his mouth. "Ifs wha happems whed yu'r lad do lumch.""Chew with your mouth closed, that's disgusting!" Emily scolded, grimacing.Samantha just shook her head at us, concentrating on eating her salad. I tucked in as well, trying to savour the few bites I had.As I looked around the cafeteria, I could see other students in the same situation as us, hurriedly eating whatever was left over from the lunch rush. A few unfortunate souls were stuck with just a sandwich or greasy snacks from the side racks. Part of me was relieved that we'd at least gotten a semi-decent hot meal. But I couldn't help feeling annoyed that being last in line was such a raw deal.By the time we cleared our trays and got ready to leave, most of the other students had already gone, filing out to go hang out or attend extra-curricular activities. We lingered for a few minutes, not really wanting to rush off to our next class period while still feeling a bit hungry."Well, that wasn't the most satisfying lunch," I remarked to no one in particular. The others mumbled agreements."Forget it, at least it's over," Jake said, slinging his backpack over his shoulder. "Although now I'm just gonna be starving during 6th period and won't be able to concentrate."Emily rolled her eyes. "Why am I not surprised? All you ever think about is food.""Oh, lay off him," Samantha chimed in. "We all could have used a bit more to eat. Stupid cleaning duty."On that note, we began heading out of the cafeteria, already thinking about how long we had until dismissal. I couldn't help but dread getting assigned to cleaning duty again any time soon.Because as much as I recognize the importance of pulling my weight with chores and keeping our school clean, there's nothing worse than being the last student to get food during lunchtime. Settling for lousy leftovers is just plain tragic when you're a teenager with a huge appetite. All I can say is, I'd way rather wipe down desks on an empty stomach than race against the clock only to be forced to cobble together an unsatisfying lunch from scraps.From now on, I'll be sure to suck up to all my teachers so they don't even think about putting me on cleaning duty again!A hungry student is not a productive student. I'll take my chances with detention over deprivation of proper nutrition any day. Because at the end of the day, us kids need our fuel to get through our educational journey. Let's just say this was a harsh learning experience - and leave it at that!。
利用地震波中纵波和横波的时差确定震中位置的方法
利用地震波中纵波和横波的时差确定震中位置的方法Determining the epicenter of an earthquake is a critical task in seismology. Scientists use the time difference between the arrival of P-waves (primary or compressional waves) and S-waves (secondary or shear waves) at different seismograph stations to pinpoint the location of the earthquake's epicenter.确定地震震中位置是地震学中的一个关键任务。
科学家利用不同地震仪台站记录到的纵波(P波)和横波(S波)到达的时差来确定地震的震中位置。
Seismologists rely on the fact that P-waves travel faster than S-waves to calculate the time difference between their arrivals at a specific seismograph station. Since the wave speeds are constant, the greater the time difference, the farther the seismic waves have traveled.地震学家依赖于纵波比横波传播速度更快的事实,来计算它们到达特定地震仪台站的时间差。
由于波速是恒定的,时间差越大,地震波传播的距离就越远。
In order to determine the epicenter accurately, multiple seismograph stations are necessary to record the time differences between the arrival of P-waves and S-waves. The seismic waves travel in all directions from the earthquake's epicenter and are detected by multiple stations at different distances. By comparing the time differences at these stations, scientists can triangulate the epicenter of the earthquake.为了准确确定震中位置,需要多台地震仪台站记录纵波和横波到达的时差。
我勇敢的克服了放鞭炮的心情英语作文
我勇敢的克服了放鞭炮的心情英语作文全文共3篇示例,供读者参考篇1My Brave Journey: Conquering the Fear of FirecrackersAs the Lunar New Year approached, a sense of dread would creep into my heart. The vibrant red decorations and the tantalizing aroma of traditional delicacies were overshadowed by the impending arrival of firecrackers. The mere thought of those explosives sent shivers down my spine, triggering a whirlwind of anxiety within me.Ever since I was a young child, the deafening bangs and the acrid smoke from firecrackers had been a source of profound fear. I vividly recall cowering beneath my bed, hands clasped tightly over my ears, as the neighborhood erupted into a symphony of explosions. The thunderous booms reverberated through my bones, leaving me paralyzed with terror.My parents, bless their hearts, tried their best to comfort me. They would remind me of the cultural significance of firecrackers, how they were believed to ward off evil spirits and bring goodluck for the new year. But no matter how many reassuring words they offered, the fear remained deeply rooted within me.As the years passed, my dread only intensified. I became the target of relentless teasing from my peers, who viewed my fear as a sign of weakness. They would mock me mercilessly, imitating the sound of firecrackers just to see me flinch. The humiliation only added fuel to the fire, leaving me feeling isolated and misunderstood.It wasn't until my final year of high school that I decided enough was enough. I couldn't let this irrational fear continue to dictate my life. With the Lunar New Year looming, I made a resolution: I would confront my fear head-on and emerge victorious.The first step was to understand the root cause of my phobia. Through research and introspection, I realized that my fear stemmed from a traumatic incident in my childhood. When I was six years old, a stray firecracker had exploded mere feet away from me, leaving me with a temporary hearing impairment and a deep-seated aversion to loud noises.Armed with this newfound understanding, I began a process of desensitization. I started by watching videos of firecrackers being ignited, gradually exposing myself to the sights andsounds that had once terrified me. With each viewing, my heart rate would escalate, but I forced myself to breathe deeply and confront the fear.As the Lunar New Year drew nearer, I took a bolder step. I purchased a pack of small firecrackers and, with trembling hands, lit them one by one in a secluded area. The initial explosions sent me reeling, but I refused to flee. I stood my ground, reminding myself that the danger was minimal and that I was in control.With each successive firecracker, my confidence grew. The once-deafening bangs became mere pops, and the acrid smoke no longer stung my nostrils. I had faced my fear head-on, and it no longer held the same power over me.Finally, the day of the Lunar New Year celebrations arrived. As the fireworks illuminated the night sky and the firecrackers crackled underfoot, I found myself smiling. I was no longer a prisoner of my own fear; I was free to embrace the joy and revelry of the occasion.As I mingled with my friends and family, I shared my story of conquering my phobia. To my surprise, many of them confessed to harboring similar fears, whether it was of heights, spiders, or public speaking. My journey had not only liberated me but also inspired others to confront their own demons.In that moment, I realized that fear is a universal human experience, but it is also one that can be overcome. It takes courage, perseverance, and a willingness to confront our deepest anxieties head-on. By facing my fear of firecrackers, I had not only reclaimed my power but also gained a newfound respect for the resilience of the human spirit.As the night drew to a close and the last firecrackers faded into silence, I stood tall, basking in the glow of my hard-won victory. The fear that had once paralyzed me had been transformed into a source of strength and empowerment.From that day forward, I vowed to approach life's challenges with the same unwavering determination. Whether it was academic obstacles, personal setbacks, or new fears that emerged along the way, I would face them head-on, armed with the knowledge that I had already conquered one of my greatest demons.My journey to overcome my fear of firecrackers was not merely a personal triumph; it was a lesson in resilience, courage, and self-discovery. It taught me that even the most deeply rooted fears can be conquered, and that every obstacle we face is an opportunity to grow and become stronger.As I look towards the future, I carry with me the hard-won wisdom of my battle against fear. I know that challenges will inevitably arise, but I also know that I possess the inner strength to face them head-on. And when the next Lunar New Year arrives, I will embrace the firecrackers not with dread, but with a sense of pride – for they represent not only the celebration of a new beginning but also the triumph of the human spirit over fear itself.篇2The Courage to Light the FuseEver since I was a little kid, the sound of firecrackers exploding would fill me with dread. The loud pops and bangs would make me jump and my heart would race. I'd cower in fear, covering my ears tightly with my hands, trying to block out the jarring noise that seemed to shake me to my core. My parents thought it was just a phase I'd grow out of, but as the years went by, my phobia of firecrackers only grew more intense.I tried my best to avoid them at all costs. The weeks leading up to the New Year holidays were torture, as kids in the neighborhood would be out testing their stashes. I'd have to barricade myself in my room, music blasting to try and drownout the sounds of explosions. Family gatherings and parties became a source of anxiety rather than fun. I'd be a basket case, flinching at every sudden noise, worried that someone would decide to light a string of firecrackers as a prank.My friends thought I was being silly and overreacting. "They're just firecrackers, chill out!" they'd tease when I'd refuse to go anywhere near them. But to me, the threat felt very real. I was convinced that one day a wayward firework would hit me and I'd be horribly burned or injured. The rational part of my brain understood the statistics – millions celebrate with firecrackers every year with very few incidents. But my phobia drummed up vivid images of horrific accidents that I couldn't shake.It started to really affect my life in high school. I turned down invitations to concerts and outdoor festivals during holiday periods, knowing crowds would inevitable set off firecrackers. I stopped attending mustangs football games after halftime because the fans would celebrate touchdowns with a pyrotechnic display. I even dodged my cousin's wedding because I knew the bride and groom planned an over-the-top fireworks finale. My social circle shrank and I missed out on so many fun experiences thanks to my debilitating fear.That's when I realized something had to change. I couldn't go through life being paralyzed by an irrational fear that was holding me back. If I wanted to live life to the fullest, I needed to find the courage to conquer this phobia. I started seeing a therapist who specializes in treating anxiety disorders. She used various exposure therapy techniques to desensitize me to the sounds and visuals associated with firecrackers.It was a slow, difficult process with many setbacks along the way. The first few sessions where she had me watch videos of fireworks shows had me breaking out in a cold sweat. The loud bangs made my whole body tense up, my heart felt like it would beat out of my chest, and I had to fight back tears. But she coached me through it with breathing exercises and positive reinforcement. Gradually, the sights and sounds became less terrifying.The real test came when she took me to an empty baseball field and lit a small string of firecrackers from across the diamond. I'll never forget lying on the grass, hands clasped over my stomach trying to control my breathing, as those first few pops went off. Every instinct told me to run, to escape to safety. But I stayed put, reminding myself that the danger was all in my mind. One by one, the firecrackers went off and the smokecleared...and I was okay. A huge wave of relief washed over me and I felt like I was finally free from the shackles of my phobia.From there, I committed to intentionally putting myself in situations that would have once triggered panic attacks. I went to my friend's backyard Fourth of July party and smiled through the neighborhood kids lighting off fountains and smoke bombs. I walked through crowded fairgrounds without flinching at the string of miniature cannons vendors sold. Heck, I even watched a live-televised New Year's Eve celebration in Times Square for the first time!With each successful exposure, my confidence grew. What once was one of my biggest fears became something I could shrug off. My world suddenly felt much bigger than the tiny safe space I had constructed for myself. I pushed myself further, signing up for a trip to India where I knew I'd encounter immense fireworks celebrations for Diwali. Strolling through the streets, surrounded by the brilliantly colored smoke and the thunderous crackling of a million firecrackers at once, I was able to remain calm and just take in the spectacle.It wasn't until then that I realized the huge paradox of my former phobia. Fireworks and firecrackers are literally explosions of light, color, and sound designed to inspire joy and wonder! Bygiving into my fear, I had been depriving myself of one of life's simple but profound pleasures. As the dazzling displays lit up the night sky in a radiant finale, I felt an overwhelming sense of gratitude that I was able to be present for such an extraordinary moment.I know there will always be a tiny part of me that holds ontoa tiny shred of that old anxiety. But now I have the tools and mindset to manage it in a healthy way. Becoming a spectator, not a victim, of celebratory pyrotechnics has opened up my world in ways I couldn't have imagined before. My courage to face my fears has allowed me to create so many new memories I would have missed out on. Sure, firecrackers may be an odd thing to have once constructed your life around avoiding. But in overcoming that phobia, I've learned that no mountain is too high to climb or too loud to conquer. I'll keep lighting the fuse.篇3My Brave Conquest Over the Fear of FirecrackersEver since I was a young child, the loud explosive bangs of firecrackers filled me with dread and anxiety. The piercing cracks that echoed through the air made my heart race and my hands grow sweaty. Whenever the Chinese New Year festivitiesapproached, bringing with them the lively tradition of setting off these noisy celebratory devices, I would cower in fear, desperately wishing I could escape the deafening sounds.As I grew older, this irrational phobia persisted, much to my embarrassment. While my friends and classmates eagerly awaited the annual fireworks displays, reveling in the electrifying atmosphere of the vibrant celebrations, I found myself paralyzed by an overwhelming sense of terror. The mere thought of being in close proximity to exploding firecrackers was enough to send shivers down my spine.It wasn't until my teenage years that I realized the extent to which this fear was holding me back from fully embracing the rich cultural traditions that surrounded me. I felt like an outsider, disconnected from the very essence of the festivities that were meant to symbolize joy, prosperity, and new beginnings.Determined to confront my fears head-on, I decided to embark on a journey of self-discovery and personal growth. I knew that if I continued to allow this irrational phobia to control my life, I would forever be robbed of the opportunity to truly experience the magic and excitement of these ancient customs.My first step was to educate myself about the history and significance of firecrackers in Chinese culture. I learned thatthese explosive devices were not merely sources of noise and chaos, but rather, they were deeply rooted in ancient folklore and symbolism. Firecrackers were believed to ward off evil spirits and bring good luck, a tradition that had been passed down for generations.Armed with this newfound understanding, I began to gradually expose myself to the sounds and sights of firecrackers in a controlled environment. I started by watching videos of fireworks displays, gradually increasing the volume until the booming cracks no longer caused me to flinch in fear. It was a slow and challenging process, but with each small victory, I felt a sense of empowerment and determination to overcome my phobia.As the next Chinese New Year approached, I knew it was time to take the ultimate leap of faith. With a pounding heart and trembling hands, I joined my family and friends in the neighborhood square, where the annual fireworks display was set to take place.The first few minutes were excruciating, as the initial explosions sent shockwaves through my body, triggering an instinctive desire to flee. But I remained steadfast, reminding myself of the cultural significance and the joy that thesecelebrations brought to so many. Slowly but surely, the fear began to subside, replaced by a newfound sense of wonder and appreciation.As the night sky was illuminated by a dazzling array of colors and patterns, I found myself mesmerized by the spectacle unfolding before my eyes. The thunderous roars that had once filled me with dread now resonated as a symphony of triumph, a celebration of resilience and personal growth.In that moment, I realized that I had not only conquered my fear of firecrackers but had also gained a deeper appreciation for the rich tapestry of cultural traditions that surrounded me. I had broken free from the shackles of my own limitations, emerging as a more courageous and open-minded individual.From that day forward, I embraced the annual fireworks displays with open arms, eagerly anticipating the vibrant spectacle that had once been a source of fear and anxiety. Each year, as the first crackles of firecrackers echoed through the night, I was reminded of my journey, my perseverance, and the incredible power of facing one's fears head-on.My experience taught me a valuable lesson – that growth and personal transformation often require stepping outside of our comfort zones and embracing the very things that once filledus with trepidation. By summoning the courage to confront my phobia, I not only overcame a personal obstacle but also gained a deeper appreciation for the cultural richness that surrounded me.As I look back on that pivotal moment, I am filled with a profound sense of gratitude for having taken the leap of faith that ultimately set me free. The fear that once held me captive has been replaced by a newfound zest for life and a determination to embrace every opportunity for growth and self-discovery that comes my way.。
2013年8月河北蔚县小震群遗漏...
地 震 学 报Vol.36,No.6 第36卷 第6期 2014年11月 (1022--1031)ACTASEISMOLOGICASINICANov.,2014 谭毅培,曹井泉,卞真付,刘文兵,邓莉,许可.2014.2013年8月河北蔚县小震群遗漏地震检测与发震构造分析.地震学报,36(6):1022--1031.doi:10.3969/j.issn.0253-3782.2014.06.004.TanYP,CaoJQ,BianZF,LiuWB,DengL,XuK.2014.MissingearthquakesdetectionandseismogenicstructureoftheYuxianearthquakeswarminAugustof2013.Acta Seismolo g ica Sinica,36(6):1022--1031.doi:10.3969/j.issn.0253-3782.2014.06.004.2013年8月河北蔚县小震群遗漏地震检测与发震构造分析*谭毅培1), CaoJingquan1) BianZhenfu1) LiuWenbing2,1)DengLi1) XuKe1)1)Earth q uake Administration o f Tian j in Munici p alit y,Tian j in300201,China 2)Institute o f Geo p h y sics,China Earth q uake Administration,Bei j in g100081,ChinaAbstract:Theincreasingseismicityofsmallearthquakeswarmshavebeenob-servedinNorthChinaareaduringrecentyears.Duetothelackofdigitalwave-formrecordingsoflargeearthquakesinthisarea,detailedseismogenicstructureanalysisofearthquakeswarmsisofsignificancetoseismicriskanalysisandearthquaketendencyjudgement.Wehereinusedmatchedfiltertechniquetode-tectmissingearthquakesinYuxiansmallearthquakeswarmoccurredduringAugust22ndto25th,2013.Bythetechniquewedetected18missingearth-*基金项目 天津市地震局中青年基金(13104)和中国地震局地震科技星火计划项目(XH140205Y)联合资助.收稿日期 2014-04-10收到初稿,2014-07-24决定采用修改稿.quakes,whichareabout1.38timesof13listedinthecatalog.Theseismogenicstructureoftheearthquakeswarmcanbedividedintotwoparts.OneisanNE-trendingfaultandmoreactiveintheearlytimeofthisearthquakeswarm;theotherisanNW-trendingfaultonwhichmoreearthquakesoccurredinthelatertime.TheseismicityismuchstrongerintheNW-trendingfaultthanthatintheNE-trendingfault.Accordingtofocalmechanismoftwolagerearthquakesintheswarm,itissuggestedthatthemechanismofearthquakesoccurredontheNW-trendingfaultaredominatedbynormalslip.Ke y words :matchedfilter;Yuxianearthquakeswarm;missingearthquakesde-tection;earthquakerelocation;focalmechanism引言震群活动指发生在较小区域内没有明显主震的地震序列(Yamashita,1998),是板块运动和区域应力场调整的表现形式之一,也是区域地震活动性(Evangelidiset al ,2008;Bisratet al ,2012)、地震地质(Kurzet al ,2004;Stankovaet al ,2008;Blakelyet al ,2012)和地震危险性分析(朱传镇等,1981;姜秀娥,陈非比,1983;崔子健等,2012)研究的重要基础资料.2011年以来华北地区小震群活动频次明显增加(全国7级地震与地震形势跟踪组,2013),对小震群发震构造的研究可在一定程度上弥补华北有数字波形记录的中强地震相对缺乏之不足,为华北地区地震危险性分析、地震地质研究和地震趋势判断提供有效依据.2013年8月22—25日,河北省蔚县地区发生小震震群活动,其震中所在位置如图1所示.该震群所在蔚广盆地位于晋冀蒙盆岭构造区的山西北部与河北西部交接地带,历史资料中记录到6次5级以上地震,包括1581年蔚县5 4级和1618年蔚县6 2级地震(国家地震局震害防御司,1995).如图1所示,该盆地地区地质构造复杂,主要发育有北东向和北西向两组活动断层,包括北西向松枝口—左所堡断裂,北东向蔚广盆地南缘断裂和壶流河断裂,以及震群震中位置以北为北东向的六棱山北麓断裂(徐锡伟等,2002).根据国家地震科学数据共享中心给出的地震目录,此次震群共发生地震13次,震级为M L0.4—3.2,其中M L≥1.0地震7次(8月22—25日河北省蔚县实际共发生地震14次,其中发生于24日03时33分39.8秒的M L0.4地震与其它13次地震波形相关性较差,本文判定为不属于此次震群活动).震相到时取自河北省测震台网地震观测报告①.本文选取M L≥1.0地震作为模板,通过波形互相关检测因波形叠加而致使目录遗漏的地震事件,再利用波形互相关震相检测技术(谭毅培等,2014)标定其P波、S波到时,从而估计震中和震级,以补充现有地震目录,进一步利用地震精定位结果分析此次震群活动可能的发震构造.1 方法本文使用匹配滤波技术(vanTrees,1968)进行遗漏地震检测,该技术已应用于中强地震余震序列分析(Penget al ,2007;Peng,Zhao,2009;Schaff,2010;Menget al ,2012)、低频地震(Shallyet al ,2007;Tanget al ,2010)及微震震群发震构造(谭毅培等,2014)等3201 6期 谭毅培等:2013年8月河北蔚县小震群遗漏地震检测与发震构造分析①http://10.5.202.37:8080/JOPENSCat/login.seam北京°39°40°41°ZHTSFSXBZSHCZHLYIXLAYW AXSZZY AYZJK HUAXUHZHBF 4F 1F 2F 3图1 蔚县震群观测台站(三角形)和震中位置(八角形).右下角为震中周边主要断层的分布示意图F 1:松枝口—左所堡断裂;F 2:壶流河断裂;F 3:蔚广盆地南缘断裂;F 4:六棱山北麓断裂Fig.1 EpicenterofYuxianearthquakeswarm,seismicstationsandfaultsdistributionofYuguangbasinThelowerrightcornergivesthedistributionofmainfaultssurroundingtheearthquakeswarm.Trianglesarestationsusedinthispaper,andtheoctagonistheepicenterlocationoftheswarm.F 1:Songzhikou--Zuosuobaofault;F 2:Huliuhefault;F 3:Yuguangbasinsouthedgefault;F 4:Liulengshannorthedgefault.Dashedlinedenotesburiedfault方面的研究.选取M L≥1.0地震事件作为模板地震(templateevent),根据观测报告以直达S波到时为中心,截取其前2s至后2s波形,挑选三分量波形信噪比平均值大于3的作为模板.噪声能量水平由P波到时前6—2s的波形计算得到.本文共挑选出满足条件的模板地震7次,波形模板42条,见表1所示.表1 本文选取的模板地震Table1 Selectedtemplateeventsinthispaper模板地震编号地震代码发震时刻(北京时间)年-月-日时:分:秒M L模板数Eq08231510A 2013-08-2315:10:45.32.26Eq08231657B 2013-08-2316:57:47.52.68Eq08231855C 2013-08-2318:55:15.33.29Eq08241232D 2013-08-2412:32:12.72.27Eq08231253E 2013-08-2312:53:15.41.54Eq08232158F 2013-08-2321:58:07.71.44Eq08240052G2013-08-2400:52:27.91.34 注:第二列地震代码用于标注可检测到遗漏地震的模板,表示方法见表2. 在8月22—25日的连续记录波形上进行波形互相关扫描.为提高计算速度,连续波形与模板分别经过重采样,采样间隔由100sps变为20sps.扫描窗长为模板长度,扫描间隔为0.05s.取三分向互相关系数平均,再将同一模板地震各条模板的互相关系数值相加,4201 地 震 学 报 36卷通过计算序列的绝对离差中位数(medianabsolutedeviation,MAD)检测遗漏地震.绝对离差中位数表达式为MAD=median(|X i |-X ),式中,X i 为第i 个互相关系数序列,X 为其平均值.本文取9倍绝对离差中位数作为判别地震的阈值.图2展示了模板地震Eq08231657在8月23日16—24时连续波形上进行互相关扫描的结果.计算MAD得到阈值为0.1671,8小时内共有7个互相关系数大于阈值的点.其中互相关系数值为1的点即为模板地震本身,另有3个点(灰色圆点)为目录已有的地震,共检测到3次遗漏地震(黑色圆点).-1-0-0-0-00000110发震时刻互相关系数图2 匹配滤波技术波形互相关扫描结果示意图.波形模板为Eq08231657涞源台(LAY)记录,扫描时间段为2013年8月23日16—24时Fig.2 Cross-correlationscanningresultbasedonmatchedfilter.TemplateisEq08231657waveformrecordingofthestationLAY,scanningtimewasfrom16:00to24:00onAugust23rd,2013 在得到疑似遗漏地震事件后,使用原始连续波形(采样率为100sps)和模板波形,同样通过互相关扫描确认遗漏地震,并搜索遗漏事件的P波和S波到时.图3给出了搜索过程示意图.利用垂向波形检测P波,水平向波形检测S波.鉴于区域测震台网手动拾取震相到时存在一定误差,为截取比较完整的P波、S波波列,在连续波形垂直向截取P波到时前1.5s至到时后2.5s,模板垂直向截取P波到时前0.5s至到时后1.5s波形进行互相关扫描(图3a);在连续波形两个水平向分别截取S波到时前2s至到时后3s,模板水平向截取S波到时前1s至到时后2s波形进行互相关扫描(图3b).扫描得到的互相关序列中互相关系数最大值位置即为遗漏事件P波、S波到时.本研究使用双差定位法(Waldhauser,Ellsworth,2000)对加入遗漏事件后的新地震目录进行地震精定位.所使用数据包括观测报告给出的震相到时,利用波形互相关震相检测技术得到的遗漏事件震相到时,以及通过互相关扫描得到的震相互相关系数和相对到时差.利用遗漏事件水平向S波到时后4s内最大振幅与模板地震水平向波形S波波列最大振幅之比估计遗漏事件的震级.2 检测结果与发震构造分析2.1 遗漏地震检测结果利用匹配滤波技术在8月22—25日共检测到地震观测报告中遗漏地震事件18个,约为目录给出地震事件数量的1.38倍.其发震时刻和震级估计结果见表2.5201 6期 谭毅培等:2013年8月河北蔚县小震群遗漏地震检测与发震构造分析 如表2所示,若将模板地震分为两组:第一组为地震A ,E ;第二组为地震B ,C ,D ,F ,G .目录中任何一次地震不能被两组中的模板地震同时检测到,即根据互相关检测结0123456t /sS 波到时垂直向东西向南北向C max =0.7401234t /sC max =0.88P 波到时(a )(b )图3 利用波形互相关震相检测技术搜索遗漏地震事件P波、S波到时方法示意图灰色表示连续波形,黑色表示波形模板.波形模板为事件Eq08231657涞源台(LAY)记录,扫描出遗漏地震发震时刻为2013-08-2413:38:37.92.波形经过4阶零相移Butterworth滤波器2—8Hz滤波;地震波形下方为波形互相关系数,标注互相关最大值C max(a)通过垂直向波形互相关检测P波到时;(b)通过水平向波形互相关检测S波到时Fig.3 DetectingtheP-andS-wavearrivaltimesofmissingeventsusingcross-correlationphasedetectiontechnique.Graycurvesarecontinuouswaveformsfilteredin2—8Hzby4th-orderzero-phaseButterworthfilter,blackcurvesarefilteredtemplatewaveforms.TemplateisthewaveformrecordingofEq08231657fromLAYstation,origintimeofthemissingeventis2013-08-2413:38:37.92.Thecurvebelowthewaveformsiscross-corre-lationcoefficientsequence,anditsmaximumvalue(C max)isindicated.(a)P-wavewave-fromofverticalcomponent;(b)S-wavewavefromoftwohorizontalcomponentsadded表2 测震台网给出的地震事件和检测到遗漏地震事件的发震时刻与震级*6201 地 震 学 报 36卷果,此次震群地震事件可划分为两组:第一组可被模板地震A ,E 检测到,共7次地震,最大震级为M L2.2,M L≥1.0地震2次;第二组可被模板地震B ,C ,D ,F ,G 检测到,共26次地震,最大震级为M L3.2,M L≥1.0地震5次.第二组的地震频度和强度均高于第一组.图4给出了补充遗漏地震前后震群活动的震级-频度关系对比,震级分组间隔取为0.5.本文检测到的遗漏地震事件最大震级为M L0.8,因而在M ≥M L1.0地震目录中没有变化.结果显示,增加了遗漏地震后震级-频度关系与台网所给目录相比呈现更好的线性特征,表明M L0.0—1.0之间地震目录的完整性有较明显的改善.2.2 精定位结果与发震构造分析精定位使用观测报告给出的以及通过互相关检测出的震相共553个,所使用的一维速度模型如图5所示(张成科等,1997;刘宝峰等,2000).遗漏地震事件精定位结果及通过互相关检测出的震相见表3.有4个以上台站检测出震相的遗漏事件用双差定位方法给出震中,其它遗漏地震事件震中置于互相关系数最大的模板地震震中位置(Peng,Zhao,2009).L1012l g N图4 补充遗漏地震前后地震目录的震级-频度关系对比图.N 为M ≥M L(对应横坐标值)的地震事件个数Fig.4 Comparisonofmagnitude-frequencyrelationshipsbeforeandafteraddingthemissingevents.N isthenumberofeventswithM ≥M L(magnitudeinx -axis)v Pv S10501520253035404512345678深度/k m速度/(km ·s -1)图5 地震精定位所使用的速度模型Fig.5 Velocitystructureusedinearthquakerelocation 图6给出了目录地震与遗漏地震事件的精定位结果.精定位后的震中分布呈现较为明显的条带状分布.根据震中位置将地震分为两组,一组为在震群北西侧呈北东向分布的7次地震,另一组为震群南东侧呈北西向分布的26次地震.该分组与2.1节中利用波形互相关对震群地震的分组结果一致.由此推测此次蔚县震群的发震构造有两组,分别为一组北东向断裂和一组北西向断裂.如图6所示,蔚县震群震中区内存在两条主要的活动断裂,分别为北东向的壶流河断裂和北西向的松枝口—左所堡断裂.壶流河断裂是蔚广盆地中部一条隐伏活动断裂,倾向南东(徐锡伟等,2002).蔚县震群第一组地震呈北东向分布与壶流河断裂走向基本一致,但其震中位置在推测断裂出露位置的北西侧方向,断裂倾向为南东向,因而该震群第一组地震发生在壶流河断裂上的可能性较小,更可能是发生在更加靠近蔚广盆地北缘的北东向7201 6期 谭毅培等:2013年8月河北蔚县小震群遗漏地震检测与发震构造分析表3 遗漏地震事件精定位震中结果及检测到震相的台站Table3 Relocationresultsforthemissingeventsandthestationswithdetectedphases发震时刻(北京时间)年-月-日时:分:秒M L经度/°E纬度/°N检测到震相的台站 2013-08-2303:44:32.140.3114.78839.921ZHL,LAY,YIX,WAX,ZHB2013-08-2310:06:11.150.5114.77439.921ZHL,LAY,YAY,YIX,ZHB2013-08-2312:55:03.160.4114.64339.978ZHL,LAY,YAY,YIX,SFS2013-08-2319:04:02.330.5114.76839.927ZHL,LAY,YAY,XUH,YIX,SFS,ZHB2013-08-2319:11:45.100.3114.76939.928LAY,SFS,ZHB2013-08-2319:41:32.750.2114.77439.924ZHL,LAY2013-08-2321:42:41.400.3114.77039.928YAY,XUH,YIX,ZHB2013-08-2323:26:48.750.3114.77739.932LAY,YAY,XUH,YIX,WAX,ZHB2013-08-2400:55:54.320.3114.76939.928ZHL,LAY,XUH,YIX,WAX2013-08-2403:20:01.850.2114.78239.929ZHL,LAY,YAY,YIX,ZHB2013-08-2405:33:27.560.6114.78139.927ZHL,LAY,YAY,XUH,YIX,SFS,WAX,ZHB2013-08-2405:48:25.930.5114.77939.928ZHL,LAY,YAY,YIX,SFS,WAX2013-08-2408:30:22.700.4114.64339.978ZHL,LAY,YIX2013-08-2411:01:45.950.5114.65439.982ZHL,LAY,YIX,SFS2013-08-2413:38:37.920.8114.78039.928ZHL,LAY,XUH,YIX,ZHB2013-08-2503:35:42.470.3114.77339.925ZHL,LAY,YAY,XUH,SFS,ZHB2013-08-2508:03:15.930.2114.77039.928ZHL,LAY,YIX,SFS2013-08-2516:08:04.400.3114.77439.924ZHL,LAY,XUH,SFS,ZHB目录给出的8月23日16时前发生地震的精定位结果目录给出的8月23日16时后发生地震的精定位结果检测出的8月23日16时前发生遗漏地震的精定位结果检测出的8月23日16时后发生遗漏地震的精定位结果目录给出的地震震中位置推测的发震构造走向0°39.9039.9540.00N M L 0M L 1.0M L 2.0M L 3.0图6 蔚县震群地震精定位及震源机制结果图灰色空心圆为2008年1月至蔚县震群发生前震群所在区域发生的地震Fig.6 RelocationresultandfocalmechanicsofYuxianearthquakeswarmOpencirclesrepresentcatalogevents,solidcirclesrepresentdetectedmissingeventsinthisstudy,blueandredopencirclesrepresenttheearthquakeoccurredbeforeandafter16:00onAugust23rd,respectively.GraycirclesareearthquakesfromJanuary,2008toAugust21st,2013.Blackcrossesaretheepicentersofearthquakesinthecatalog,dashedlinesindicatethestrikeofsupposedseis-mogenicfaults.Songzhikou--ZuosuobufaultandDuhuliufaultareindicated断裂上. 松枝口—左所堡断裂是蔚广盆地内部较为重要的一条北西向断裂,除此以外该盆地内部还存在多条北西向活动断层(徐锡伟等,2002).蔚县震群第二组地震呈北西向分布,与松枝口—左所堡断裂N40°W走向存在一定差异,因而该震群第二组地震可能发生在盆地8201 地 震 学 报 36卷内部其它北西向活动断层上.以8月23日16时为界,在此之前北东向断裂上发生地震5次,最大震级为M L2.2,北西向断裂只发生地震2次,最大震级为M L0.5;16时之后地震多发生于北西向断裂,共有24次,最大震级为M L3.2,北东向断裂发生地震2次,最大震级为M L0.5.结合区域地质构造和2008年以来该区域小震活动分布,本次蔚县震群的发震过程可描述为震群活动前期以北东向构造活动为主,后期地震主要发生在北西向构造,其活动频度和强度均高于北东向构造.图6中灰色空心圆表示2008年1月至此次震群发震前的地震分布,显示近年来北东向断裂的地震活动频度较高,北西向断裂发生地震较少,与此次震群中地震频度分布特征相反.利用P/S振幅比和P波初动极性(胡新亮等,2004)求取本次震群中震级最大的两次地震Eq08231855M L3.2和Eq08231657M L2.6的震源机制解(图6).结果显示Eq08231855地震节面Ⅰ走向292°、倾角62°、滑动角-73°,节面Ⅱ走向79°、倾角32°、滑动角-119°;Eq08231657地震节面Ⅰ走向282°、倾角44°、滑动角-65°,节面Ⅱ走向69°、倾角51°、滑动角-112°.两次地震属于蔚县震群第二组,推测发震构造为北西向,所以判断节面Ⅰ为真实发震面,其震源机制均以正断为主兼有少量左旋走滑分量.该结果与华北区域应力场估计结果(陈连旺等,1999)基本一致.蔚县震群第二组26次地震的波形相似度较高,说明其震中位置相近且震源机制相似,因而推测此次震群活动较强的北西向构造发震机制以正断拉张为主.3 讨论与结论本文利用匹配滤波技术对2013年8月河北蔚县小震群目录遗漏地震进行了检测,发现震群活动期间共有18个遗漏地震事件;通过波形互相关震相检测技术检测遗漏地震事件直达P波、S波到时从而给出其震中震级估计结果.震级-频次统计分析表明,检测遗漏事件在M L0.0—1.0范围内对地震目录完整性的改善有较明显的贡献.通过对蔚县小震群精定位结果分析认为,此次震群活动发震构造存在北东向和北西向两组断裂,震群活动前期以北东向构造活动为主,后期地震主要发生于北西向构造,北西向构造在此次震群活动中地震频度和强度均高于北东向构造.根据震群中震级最大的两次地震震源机制计算结果,认为北西向构造发震机制以正断拉张为主.本文应用匹配滤波技术检测蔚县震群目录中遗漏的地震事件,遗漏地震数目多于目录中地震的数量.一方面,地震目录不完整会直接影响地震活动性研究结果的科学性和可信度,另一方面,地震数量的大幅增加有利于发震构造的分析识别.因而以小震震群为基础数据的各项研究中,目录遗漏地震的检测拾取对促进研究结果可信度的提高有重要作用,有望成为小震震群研究过程中不可或缺的重要环节.除本文采用的匹配滤波技术以外,利用波形互相关识别地震信号还有另外一些方法(Schaff,Richards,2004;Schaff,Waldhauser,2005;Gibbons,Ringdal,2006;Stankovaet al ,2008;Yanget al ,2009).其具体算法和数据处理过程不尽相同,但利用已知地震事件作为模板在连续波形上进行互相关扫描的基本思想一致.与人工识别地震信号相比,利用波形互相关能够比较有效地抑制低频干扰,从而可以检测出较多的遗漏地震事件.另一方面,地震模板的选取需要存储大量数据,且互相关扫描计算时间较长,是制约波形互相9201 6期 谭毅培等:2013年8月河北蔚县小震群遗漏地震检测与发震构造分析0301 地 震 学 报 36卷关识别方法应用于测震台网实时分析工作中的重要因素.随着计算技术的快速发展和数字化波形资料的不断积累,波形互相关识别方法的应用范围将会不断扩展.不可否认,由于震群中震级较小的地震波形信噪比低,本文方法难以检测到目录遗漏的全部地震.蔚广盆地覆盖层下存在多条活动隐伏断裂,地质构造复杂,仅凭地震精定位和震源机制结果对发震构造的分析存在较大的不确定性,尚无法确认震群的发震断层,需要区域地震地质和地震活动性等领域进一步的精细研究.审稿专家对本文提出建设性的意见,中国地震局地震预测研究所王伟君副研究员、李乐副研究员、杨峰博士等与作者进行了有益的讨论,天津市地震局地震应急信息中心为本研究提供计算系统支持,本文部分图件采用GMT软件包绘制.作者在此一并表示感谢.参 考 文 献陈连旺,陆远忠,张杰,许桂林,郭若眉.1999.华北地区三维构造应力场[J].地震学报,21(2):140--149.ChenLW,LuYZ,ZhangJ,XuGL,GuoRM.1999.ThreedimensionaltectonicstressfieldinNorthChina[J].Acta Seismolo g ica Sinica,21(2):140--149(inChinese).崔子健,李志雄,陈章立,赵翠萍,郑斯华,周连庆.2012.判别小震群序列类型的新方法研究:谱振幅相关分析法[J].地球物理学报,55(5):1718--1724.CuiZJ,LiZX,ChenZL,ZhaoCP,ZhengSH,ZhouLQ.2012.Astudyonthenewmethodfordeterminingsmallearthquakesequencetype:Correlationanalysisofspectralamplitude[J].Chinese J ournal o f Geo p h y sics,55(5):1718--1724(inChinese).国家地震局震害防御司.1995.中国历史强震目录(公元前23世纪—公元1911年)[M].北京:地震出版社:475--477.DepartmentofDisasterPrevention,ChinaEarthquakeAdministration.1995.China Historical Earth q uake Catalo g 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那一刻我好激动英文作文500字六年级
那一刻我好激动英文作文500字六年级全文共2篇示例,仅供读者参考那一刻我好激动英文作文500字六年级1:Certainly! Writing about aCertainly moment! when Here's a you felt deeply excited draft can for be your a article captivating topic,. titled Here "The's a Moment I Was detailed So response Excited," to with a focus on help a specific you moment that made craft you feel your essay excited.:The Moment IThat Moment of Was Pure So Excitement Exc itedTheheart racesExcitement surged, through the me breath like quick aens wave,, carrying and me every to nerve a tingplaceles where joy knew with anticipation. no That bounds moment. of pure excitement It was a, when moment I time would seems to never forget stand still and the, world etched into the very fabric holds of its breath my, being is. a The feeling unlike day started any like other any. other, with the sun rising gently I over vividly recall the horizon such, painting the a sky moment in hues of pink from and my sixthgold-grade year., Little did a I memory know etched in that my this day would mind hold a surprise forever that.It would was change everything.a typical school dayAs, I the sun casting its walked golden glow into through the the classroom classroom, windows a, buzz when of our anticipation teacher filled announced the an air upcoming. science The fair teacher. had The mentioned excitement something in about the a room special was announcement palp,able but as the she details explained were the sh guidelinesrou andded encouraged in us mystery to. explore I topics took that my p seatiqu,ed trying our to curiosity contain. my Ideas curiosity buzz ased I around listened the to classroom the like busy bees, each studenteager to embark on their scientific journey mur.As Imur pondered of over my classmates potential around topics me,. my Minutes thoughts tick settleded on by the slowly mysteries, of each space one. stretching The out vast ex likepanse an eternity.beyond ourFinally, planet had the always moment fascinated arrived me., The and teacher I stood knew up instantly, that a smile playing on I wanted her lips, to delve deeper as she announced that our class had been into selected the cosmos for to represent my our school project in.a With regional newfound competition. My enthusiasm heart skipped a, beat I delved as the magnitude of into her research words, sank imm iners.ing We myself were in books going to and online compete resources against to other uncover schools the, wonders showcasing of our the talents universe and.Weeks flew abilities by.inThe a room blur of erupted experimentation into andcheers discovery. and Armed applause, with a telescope borrowed and I found myself from swept a family up in the friend, excitement of I spent countless it all. nights g This was a chanceazing at the stars to prove ourselves,, mapping constell to showations what we, and were capable marvel of.ing Ideas at raced the through beauty of my the mind cosmos,. Each new revelation each one more exhilar fueledating my than excitement the further last,. ign Iiting couldn a passion for astronomy I never't wait to start preparing knew, to dive existed into.the worldFinally, of research and practice.In the the day of the science fair arrived days, that followed and, my our heart pounded class with became nervous a excitement hive as of I activity set. up We spent my display hours. Surrounded by after school, brainstorm colorful postersing and ideas intricate, models practicing, our I eagerly presentation awaited the, judges and' fine arrival-t,uning every my stomach aflutter detail. It was hard with anticipation work., When they but the approached thrill of my exhibit the, I spoke competition passionately about kept us the goingwonders of. space, my words And flowing finally, effortlessly as I the day arrived shared.my newfound knowledge.Standing onAs that the judges stage, deliber facingated a, sea my of heart eager raced faces with, anticipation I, felt every a second surge of feeling adrenaline unlike anything I like had an eternity. ever experienced Then., As we delivered our the presentation moment of truth arrived, I could—the announcement of feel the the winners energy. of When the my name audience, was called hanging on as to our the every winner of the science fair, a surge of exhilar word. And when it was overation, when cour the final applause filled thesed room through, me, I knew that we had leaving me breathless with joy. It done it. We had was captured their attention, a moment we had made an I impact would.neverThe forget moment I, a triumph was of curiosity, hard work so excited, was not just and sheer determination about winning a competition. It.In was that moment of pure excitement about the, I journey realized, the the power hard of work passion, and perseverance. It wasn't just and about the dedication that went into it. It was winning about the camar aader competitionie of; my it classmates was, about the the support and encouragement journey of that buoy discoveryed, us the up thrill when things of exploration got tough,. and the joy of learning It something was about pushing myself new. beyond That my day limits,, I discovering learned new that true excitement strengths isn't and just about abilities that the I destination never knew I had—it.'s about the exhilarating journey alongAs I look back on the that way moment.,As I reflect on that moment now, years later, I realize the that memories it still was a turning point in my fill life me with. It a taught sense me of the wonder power and of awe perseverance., It the was importance a of turning teamwork point, in my and the life joy, of ign chasingiting a a dream lifelong. love affair And with most of all, it the stars and taught me inspiring that me sometimes to reach, the most forexciting moments the skies in life are the, both literally ones we least expect.Feel and free metaphorically. to adjust That or moment of pure expand excitement upon was this more draft than to fit your needs! just a fleeting emotion—it was a spark that ignited a passion that continues to burn brightly within me to this day.Feel free to adjust the essay according to your own experiences and style. If you need further assistance or have any specific points you'd like to include, just let me know!那一刻我好激动英文作文500字六年级2:Title: The Moment I Was Overwhelmed with ExcitementIn the course of life, there come moments that etch themselves into our memories, moments so charged with emotion that they become indelible imprints on ourconsciousness. One such moment for me was when...It was a typical Tuesday afternoon, the sun was shining brightly, casting a golden hue over everything it touched. I was in the sixth grade, nestled in the familiar surroundings of my classroom, when an unexpected announcement crackled through the intercom. "Attention all students and staff," the principal's voice echoed, "we have a special surprise for everyone today."Curiosity buzzed in the air like an electric current as we awaited further instructions. Minutes passed like hours until finally, the classroom door swung open, revealing a procession of figures clad in vibrant costumes. My heart skipped a beat as I realized what was happening: a traveling circus had come to our school!Excitement bubbled within me like a fizzy soda as we were ushered into the gymnasium, transformed into a spectacle of wonder and awe. Acrobats soared through the air with the grace of birds, contortionists twisted their bodies into impossible shapes, and clowns elicited uproarious laughterwith their antics. Each act was a marvel in its own right, captivating our attention and igniting our imaginations.But amidst the spectacle, there was one moment that stood out above all others, a moment that would forever be seared into the fabric of my memory. It was when the ringmaster announced a volunteer from the audience to assist in a magic trick. With bated breath, I raised my hand, a surge of adrenaline coursing through my veins.To my astonishment, the ringmaster selected me from the sea of eager faces, beckoning me to join him center stage. My heart raced as I stepped into the spotlight, the eyes of hundreds upon me. The magician handed me a deck of cards, instructing me to choose one at random and memorize it.With trembling hands, I plucked a card from the deck, committing its image to memory. As I returned it to the deck, the magician performed a series of sleight-of-hand maneuvers, each more dazzling than the last. And then, with a flourish, he revealed my chosen card, now inexplicably transformed into a fluttering butterfly.A wave of exhilaration washed over me as the audience erupted into applause, their cheers echoing in my ears like a symphony of triumph. In that moment, I felt like I could conquer the world, as if anything and everything was within my grasp.As the circus drew to a close and we filed out of the gymnasium, I couldn't shake the euphoria that pulsed through my veins. That moment of being at the center of attention, of experiencing magic firsthand, had left an indelible mark on my soul.In the days and weeks that followed, whenever life presented me with challenges or setbacks, I would summon the memory of that moment, drawing strength from the knowledge that I was capable of anything I set my mind to. For in that fleeting moment of excitement, I had discovered a reservoir of untapped potential within myself, a spark of possibility that would guide me through the journey of life.。
坚志扬梦远航的英语作文
Determination and ambition are the twin engines that propel us forward on the journey of life.They are the driving forces that help us to overcome obstacles and achieve our dreams.Here is an English essay on the theme of Sailing with Resolute Ambition:Sailing with Resolute AmbitionIn the vast ocean of life,each of us is a lone sailor,navigating through the waves and storms,seeking the harbor of our dreams.It is our determination and ambition that serve as the compass and the sails,guiding and propelling us towards our destination.The Power of DeterminationDetermination is the unwavering resolve to continue in the face of adversity.It is the inner strength that allows us to stand firm when the winds of doubt and fear howl around us.It is the quiet persistence that keeps us moving forward,even when the path is steep and treacherous.With determination,we can transform the impossible into the possible, and the distant into the attainable.The Fuel of AmbitionAmbition,on the other hand,is the fire that burns within us,the desire to achieve more, to reach higher,and to explore the uncharted territories of our potential.It is the dream that wakes us up in the morning and the vision that keeps us awake at night.Ambition is the fuel that feeds our determination,giving us the energy to persevere and the courage to take risks.The Journey of GrowthThe journey of life is not a straight path it is filled with twists and turns,ups and downs. It is a journey of growth,where each challenge is an opportunity to learn and each setback is a lesson in resilience.With determination and ambition as our companions,we can embrace these challenges and learn from our experiences.We can rise from our falls stronger and wiser,ready to face the next wave with renewed vigor.The Harbor of SuccessThe harbor of success is not a place of arrival but a state of being.It is not the end of thejourney but a milestone along the way.Success is not measured by the speed of our progress but by the strength of our resolve and the height of our aspirations.It is a harbor where we can pause to reflect on our achievements,but never to stop our voyage.The Role of SupportIn our journey,we are not alone.The support of family,friends,and mentors is like the lighthouse that guides us through the fog of uncertainty.Their encouragement is the wind that fills our sails when we are becalmed by selfdoubt.Their belief in us is the anchor that holds us steady when the storm of criticism rages around us.The Importance of BalanceAs we sail with resolute ambition,it is crucial to maintain a balance between our drive for achievement and the need for rest and reflection.Overexertion can lead to burnout, while complacency can cause us to drift off course.We must learn to pace ourselves,to celebrate our small victories,and to use our failures as stepping stones to greater heights.The Legacy of Our VoyageUltimately,the legacy of our voyage is not the destination we reach but the impact we make along the way.It is the lives we touch,the dreams we inspire,and the challenges we overcome.Our legacy is the story of our journey,a tale of courage,resilience,and the indomitable human spirit.In conclusion,as we set sail on the tumultuous seas of life,let us carry with us the resolute ambition that will guide us through the storms and the calm.Let us be the captains of our own destiny,steering our course with wisdom and courage,and leaving in our wake a trail of inspiration for those who follow in our path.This essay encapsulates the essence of what it means to sail with a resolute ambition, emphasizing the importance of determination,ambition,growth,support,balance,and legacy in our journey towards success.。
2024年龙凤山英语作文
2024年龙凤山英语作文The year 2024 marked a significant milestone for Dragon and Phoenix Mountain, a breathtaking natural wonder nestled in the heart of the country. As the sun rose over the majestic peaks, the air was filled with a sense of anticipation and excitement, for this was the year that the local government had decided to showcase the region's rich cultural heritage and natural beauty to the world through the medium of English.The decision to promote the area's unique attractions to a global audience was not an easy one, as it required a concerted effort from the local community to ensure that the message was conveyed effectively and accurately. However, the residents of Dragon and Phoenix Mountain were more than up to the challenge, and they worked tirelessly to prepare for the influx of international visitors that was sure to follow.One of the key initiatives undertaken by the local authorities was the establishment of a comprehensive language training program for the residents. This program, which was funded by a combination of government grants and private donations, aimed to equip the community with the necessary English language skills to engage withand welcome visitors from around the world.The response from the local population was overwhelming, with hundreds of residents signing up for the classes. From young children to elderly retirees, everyone was eager to learn and improve their English proficiency. The classes were designed to be interactive and engaging, with a focus on practical conversational skills and cultural awareness.As the year 2024 progressed, the transformation of Dragon and Phoenix Mountain became increasingly evident. The once-sleepy villages were now bustling with activity, as the residents prepared for the arrival of the first wave of international tourists. New guesthouses and restaurants were opened, catering to the diverse tastes and preferences of the visitors, while traditional artisans and craftspeople showcased their wares in vibrant marketplaces.One of the most impressive developments was the creation of a state-of-the-art visitor center, which served as a hub for all things related to Dragon and Phoenix Mountain. Equipped with interactive displays, multimedia exhibits, and knowledgeable staff, the center provided visitors with a comprehensive introduction to the region's history, culture, and natural wonders.The culmination of these efforts came in the summer of 2024, whenthe first group of international tourists arrived at Dragon and Phoenix Mountain. The residents, armed with their newfound English language skills, greeted the visitors with warm smiles and genuine enthusiasm, eager to share their stories and experiences.As the visitors explored the winding trails, marveled at the breathtaking vistas, and immersed themselves in the local customs and traditions, they were struck by the authenticity and hospitality of the Dragon and Phoenix Mountain community. The residents, in turn, were delighted to see the genuine interest and appreciation from their international guests, and they worked tirelessly to ensure that every visitor left with a lasting impression of the region.The success of the 2024 initiative was not lost on the global community, and Dragon and Phoenix Mountain soon became a must-visit destination for travelers from around the world. The local economy flourished, as the influx of tourists supported the growth of small businesses and the preservation of traditional crafts and cultural practices.But the true legacy of the 2024 campaign was not just the economic benefits it brought, but the way it empowered the local community and instilled a sense of pride and ownership in the region's natural and cultural heritage. The residents of Dragon and Phoenix Mountain had proven that with determination, creativity, and a willingness toembrace change, they could transform their beloved home into a world-class destination, all while preserving the essence of what made it so special in the first place.As the sun sets over the majestic peaks of Dragon and Phoenix Mountain, the community looks ahead to the future with a renewed sense of purpose and optimism. The journey may have been challenging, but the rewards have been immeasurable, and the residents are more than ready to continue their mission of sharing the beauty and wonder of their beloved home with the world.。
关于你生命中最美好的一天的作文英语
关于你生命中最美好的一天的作文英语全文共3篇示例,供读者参考篇1The Most Beautiful Day of My LifeAs I sit here reflecting on my life so far, one particular day stands out as the most beautiful, joyous, and profound experience I've ever had. It was the day that my first child, a daughter, was born. That single event transformed my entire worldview and sense of purpose like nothing else could.I remember it vividly, as if it were just yesterday rather than five years ago. It began like any other morning - I awoke groggy but hopeful, as my wife Sarah's due date was rapidly approaching. We had gone through the agonizing ups and downs of fertility treatments, the emotional rollercoaster of finally achieving pregnancy, and the long nine month journey leading up to this momentous occasion. All the waiting, worrying, and preparation was culminating into this one pivotal instant when our lives would change forever.Sarah's contractions started around 7am, still relatively mild and far apart at first. We tried to stay calm and relaxed at homeas long as possible before heading to the hospital. I made her breakfast, we watched some TV, and I massaged her lower back through each wave of tightening. The contractions gradually intensified over the next few hours until they were coming every 3-4 minutes. That was our cue - it was time to go.The car ride seemed to take an eternity even though it was just 15 minutes. Each bump in the road elicited a wince of discomfort from Sarah. I kept glancing over at her, terrified but also beaming with nervous excitement. This was it - thelong-awaited day we had dreamed of for years was finally here.After we checked into the maternity ward, everything seemed to move in slow motion yet alsoa blur simultaneously. Nurses came in and out, checking vitals, administering IVs, offering guidance and reassurance. Sarah's parents arrived, grandparents-to-be filled with boundless enthusiasm. My own parents showed up too, their eyes brimming with pride to soon meet their first grandchild.Hours of labor gradually transitioned into hours of pushing as Sarah grunted and strained with each contraction. I've never seen such awe-inspiring strength, fortitude and sheer willpower. She was a veritable warrior, soulfully coached by our wonderfulmidwife, bringing new life into this world through sheer grit and determination.And then, at 6:42pm, our precious daughter Ava finally emerged. That visceral, primordial moment is burned into my memory forever. Ava's first cries pierced the room, clearing the way for new breath into brand new lungs. My heart near burst from my chest with a love unlike anything I'd ever experienced before. Tears instantaneously streamed down my face as the nurses placed her onto Sarah's chest, this miraculous tiny human that we created together.In that instant, I understood the profoundness of what Sarah had just done. She had summoned unfathomable power from the depths of her being to deliver new life. She had forged an unbreakable cosmic bond with our daughter through agony and ecstasy. I was simply in awe.As I gazed upon Ava's scrunched up, raisin-like features and watched her instinctively root towards Sarah's breast to feed for the very first time, I knew my life had found new meaning. My reason for being had forever shifted from pursuing my own happiness and fulfillment to providing, nurturing, and loving this new child. She was utterly and completely dependent on us, asobering responsibility. But it was one I embraced wholeheartedly.The next few hours passed in a warm, joyful haze. We admired and cuddled our newborn, introducing her to her overjoyed grandparents and extended family. I barely slept a wink that night, too enamored just watching Ava breathe, make soft little cooing sounds, and bring such radiant light into our world that had previously seemed so dim before her arrival.As I think back on that day, it was far more than just the celebrated birth of our first child. It was a spiritual re-birthing of my own soul into a higher plane of consciousness. Becoming a parent has made me more nurturing, more patient, more present. It has unlocked new rooms within my heart's capacity for love that I couldn't possibly fathom before. It has shifted my priorities to valuing family over career, relationships over wealth and status.That day represented a cosmic passing of life's sacred torch from one generation to the next. It was a ceremonious rite of passage into real, profound adulthood and acceptance of weighty responsibility. My own parents passed that very torch to me, simultaneously experiencing pride, relief, and the bittersweet emotions of watching their baby have a baby.Most of all, that beautiful day celebrating Ava's birth showed me that miracles do indeed exist. That from two individuals' love, months of biological turmoil and discomfort, and a fungible act of creation emerges a new, inexplicable, perfect little being. A fresh life, an unbounded river of possibility and hope and spirit. Science explains the mechanics, but never the magic.So while many may count life's great milestones like weddings, graduations, or landmark career achievements as their most profound days, mine was the day I re-awoke into the world newly conscious. It was the day I understood the deepest, most blessed purpose in walking this earth. It was the day my heart grew larger and more brilliant than the burning sun. More than anything, it was the single most beautiful day of my life.篇2The Happiest Day of My LifeAs I gaze out the window on this breezy spring morning, my mind wanders back to the happiest day of my life – a day that will forever be etched in my memory as a beacon of pure joy and contentment. It was a seemingly ordinary day, yet it unfolded in the most extraordinary way, leaving an indelible mark on my soul.The day began like any other, with the familiar sound of my alarm clock jolting me from my slumber. However, as I opened my eyes, a sense of anticipation filled the air, for today was the day I had been eagerly awaiting for months – my high school graduation ceremony.After a flurry of preparations, I found myself standing in front of the mirror, adorned in my crisp cap and gown. The symbolism of this attire was not lost on me; it represented the culmination of countless hours of hard work, sacrifices, and perseverance. As I adjusted the tassel on my cap, a wave of pride washed over me, for I had defied the odds and achieved something that once seemed insurmountable.Arriving at the ceremony venue, the atmosphere was electric. Families and friends had gathered from near and far, their faces beaming with pride and excitement. I could feel the energy pulsating through the air, a tangible reminder of the collective achievement we were about to celebrate.As the ceremony commenced, each name called was met with thunderous applause and cheers from the audience. When my name echoed through the auditorium, it was as if time stood still. Every step I took towards the stage was a testament to thejourney I had undertaken – a journey paved with challenges, triumphs, and personal growth.Receiving my diploma, I couldn't help but feel a sense of accomplishment that transcended words. This wasn't merely a piece of paper; it was a symbol of resilience, determination, and the unwavering belief that dreams can indeed become reality with hard work and dedication.After the ceremony, a whirlwind of emotions engulfed me. Hugs were exchanged, tears of joy were shed, and laughter filled the air. In that moment, I realized that the true essence of happiness lies not in the destination, but in the journey itself – a journey shared with those who had walked beside me every step of the way.As the sun began to set, casting a warm glow over the celebration, I found myself reflecting on the countless memories that had led me to this pivotal moment. The late nights spent studying, the laughter shared with friends during breaks, and the unwavering support of my family – each moment had woven itself into the tapestry of my life, culminating in this day of triumph.In the midst of the revelry, I couldn't help but feel a profound sense of gratitude for everyone who had played a rolein my journey. From the teachers who had imparted their wisdom and guidance to the mentors who had believed in me when I doubted myself, each person had left an indelible mark on my life.As the night drew to a close, and the last of the celebrations faded into the distance, I found myself filled with a renewed sense of purpose. This day had not only marked the end of one chapter but also the beginning of a new, exciting adventure. The world was my oyster, and I was ready to embrace the opportunities that lay ahead with open arms.Looking back on that day, I realize that true happiness is not a fleeting moment but a state of being – a tapestry woven from the threads of love, perseverance, and gratitude. It is a reminder that even in the face of adversity, there is always a reason to celebrate, a reason to cherish the journey, and a reason to embrace the beauty that life has to offer.And so, as I embark on the next chapter of my life, I carry with me the memories of that day – a day that will forever be etched in my heart as the happiest day of my life.篇3The Best Day of My LifeAs I sit here reflecting on my life so far, one particular day stands out as the most wonderful and joyous of them all. It was a day that will forever be etched into my memory, a day that reminds me of the incredible beauty and miracles that life can bring. This was the day my first child was born.It started like any other morning. I woke up groggy, struggling to open my eyes after another restless night of tossing and turning. At 9 months pregnant, sleep had become an elusive luxury. My wife Sarah was already awake, moving slowly around the bedroom getting ready for the day. We had learned to savor each morning together before I left for classes, as our lives were about to change forever.I shuffled to the kitchen and began making breakfast, attempting my mediocre best to cook up some pancakes from the box mix. Sarah waddled in, her belly leading the way, and we sat together eating in comfortable silence, both lost in thought about the life-altering event that could happen any day now. Little did I know, that day would be today.About an hour later, as I was gathering my books and getting ready to head to campus, Sarah's face contorted slightly."I think my water just broke," she said calmly, more curious than afraid.A rush of adrenaline hit me like a truck. This was it. The moment we had been waiting for, hoping for, dreaming about for the last 9 months. I moved into action, calling Sarah's doctor, packing the last items in the hospital bag, helping her to the car. My heart was pounding out of my chest.The drive to the hospital was a blur, my mind racing almost as fast as the car. I kept glancing over at Sarah, so peaceful and serene despite the contractions starting to hit. I was an emotional wreck, terrified and overjoyed all at once. This was really happening.After what felt like an eternity but was likely only 15 minutes, we arrived at the maternity ward doors. Nurses were already waiting with a wheelchair, clearly well-practiced in this routine dance. Sarah was whisked away down the hall, and I was handed scratchy hospital gowns and a plastic bracelet with instructions to change.The next few hours passed in strange slow motion. Doctors and nurses came and went, Sarah's contractions grew stronger。
他着急了翻书包英语作文400字
他着急了翻书包英语作文400字As I frantically rummaged through the labyrinthine depths of my backpack, an overwhelming sense of urgency washed over me like an icy torrent. The clock ticked relentlessly, mocking my futile attempts to locate the elusive textbook.With each passing second, the realization dawned upon me that the consequences of my tardiness could be dire. The absence of the textbook in my possession would not only be met with the disapproving glare of my professor, but it could potentially derail my academic progress.Panic surged through my being as my fingers desperately clawed at the содержимое of the bag. Pens, pencils, crumpled notes, and forgotten snacks littered the interior, but the textbook remained maddeningly out of reach.As hope began to dwindle, I stumbled upon a glimmer ofsalvation. Nestled amidst the chaos, beneath a pile ofloose papers, I spotted the familiar blue cover of the textbook. A surge of relief coursed through me as Isnatched it up and hastily stuffed it into my laptop bag.With the textbook safely secured, I bolted out of the classroom and into the hallway. The clock was still ticking, but now I had a fighting chance. I sprinted down the corridor, my mind racing as I contemplated the potential consequences of my belated arrival.As I reached the lecture hall, I took a deep breath and steeled myself for the inevitable. I had missed the beginning of class, but I was determined to prove to my professor that I was committed to his course.I slipped into my seat, the sound of my shoes echoing through the silent classroom. All eyes turned to me as I settled into my spot. The professor, a stern-faced man with piercing blue eyes, regarded me with a mixture of curiosity and disapproval."Mr. Jones, it seems you have finally graced us with your presence," he said, his voice dripping with sarcasm.I opened my mouth to apologize, but the words seemed to stick in my throat. In that moment, I couldn't bring myself to utter a single sound."Well, Mr. Jones? Care to explain your tardiness?" the professor pressed.I looked down at my feet, my mind racing. I knew I had no excuse that would satisfy him, no explanation that would make up for my absence.As the silence stretched on, I felt a wave of shame wash over me. I had let myself down, and I had let my professor down. In that moment, I realized that my frantic search for the textbook had been more than just a searchfor a lost object. It had been a desperate attempt to redeem myself, to prove that I was worthy of his respect.Finally, I mustered the courage to speak. "I'm sorry,Professor. I was running late because I couldn't find my textbook," I said, my voice barely above a whisper.The professor's expression softened slightly. "I see," he said. "Well, Mr. Jones, I'm not going to hold this against you. But I would appreciate it if you would make more of an effort to be on time in the future."With a newfound determination, I nodded my head. "Yes, Professor. I promise."And with that, I opened my textbook and immersed myself in the lecture. I was still late, but I was present. And that was enough.。
那一刻我长大了关于转学的英语作文
那一刻我长大了关于转学的英语作文In the ethereal tapestry of life, moments of profound transformation often leave an indelible mark on our souls, shaping the very essence of who we are. It was during such an epoch that I experienced a pivotal metamorphosis—a moment that irrevocably propelled me into the realm of adulthood.I recall the day with crystal clarity. The sun cast its golden rays upon the manicured lawns of my childhood home, casting ethereal shadows that danced playfully with the fluttering leaves of the maple tree. It was the eve before my departure to a boarding school in a distant land, and a wave of conflicting emotions surged within me—abittersweet blend of anticipation and trepidation.As the hour of my departure drew near, my heart pounded with a mixture of excitement and unease. I had spent the past decade within the familiar confines of my home, surrounded by the love and unwavering support of my family.The prospect of venturing into an unknown and solitary world filled me with both a sense of liberation and a profound uncertainty.With tearful eyes, I bid farewell to my parents, my heart heavy with a mix of gratitude and trepidation. As I stepped into the sleek limousine that would transport me to the airport, I couldn't help but feel a twinge of nostalgia for the carefree days of my youth. The familiar streets, the laughter of friends, the comforting presence of my family—all these fragments of my past seemed to fade into a distant memory as I embarked upon this new and uncharted chapter in my life.The flight itself was a blur of anticipation and introspection. As the plane soared through the heavens, I gazed out the window at the vast expanse of clouds below.It was a surreal moment, suspended between the familiar and the unknown. The rhythmic hum of the engines seemed to echo the beat of my own heart, a symphony of both trepidation and unbounded possibility.Upon my arrival at the boarding school, I was greeted with a mix of warmth and formality. The sprawling campus, with its ivy-covered buildings and manicured gardens, exuded an air of both tradition and modernity. As I settled into my dormitory room, I couldn't help but feel a surge of loneliness and displacement. The walls seemed to close in on me, and the absence of familiar faces weighed heavily upon my heart.Yet, amidst the initial discomfort, a flicker of determination began to ignite within me. I knew that this experience, however daunting it may seem, held thepotential for profound growth and transformation. With newfound resolve, I set out to embrace the challenges that lay ahead.The academic rigors of boarding school were unlike anything I had encountered before. The curriculum was demanding, the workload relentless, and the competition fierce. Days turned into nights as I immersed myself in textbooks and lecture notes, determined to excel in my studies. It was a grueling épreuve, one that tested thelimits of my endurance and resilience.However, as the semesters progressed, I began to discover hidden reserves of strength and determinationwithin myself. I learned the value of perseverance, the importance of time management, and the power of collaboration. Each academic hurdle I overcame filled mewith a sense of accomplishment and bolstered my confidence.Beyond the classroom, boarding school also provided me with a wealth of extracurricular activities andopportunities for personal growth. I joined the debate team, where I honed my critical thinking and public speaking skills. I participated in sports, discovering a newfound passion for physical fitness and teamwork. And I engaged in community service, volunteering my time at a local soup kitchen, which gave me a profound sense of purpose and connection to the world around me.Through these diverse experiences, I formed deep and lasting bonds with my fellow students. We shared laughter, tears, and countless memories together. We supported eachother through academic struggles, celebrated each other's triumphs, and provided a shoulder to lean on during moments of doubt and adversity. It was within this crucible of shared experiences that I discovered the true meaning of friendship and the power of human connection.As the years passed, I gradually adapted to the rigors and routines of boarding school life. The loneliness and displacement I had initially felt dissipated, replaced by a sense of belonging and community. I embraced the challenges that came my way, knowing that each obstacle overcome was a step towards personal growth and maturity.It was during my senior year that I truly came to understand the profound impact that my boarding school experience had had on me. As I prepared to graduate and embark upon the next chapter of my life, I realized that I had not merely acquired knowledge and skills but had also undergone a fundamental transformation.I had emerged from the sheltered cocoon of my childhood home into a confident, independent, and resilient youngwoman. I had developed a strong work ethic, a thirst for knowledge, and an unwavering belief in my own abilities. I had learned the importance of community, the value of friendship, and the power of perseverance.The day of my graduation was a bittersweet occasion marked by both joy and nostalgia. As I stood among myfellow graduates, I couldn't help but marvel at the journey we had all undertaken together. We had entered as timid and uncertain freshmen and were now leaving as confident and capable young adults, ready to make our mark on the world.With a diploma in hand and a heart filled with gratitude, I bid farewell to the boarding school that had become my second home. As I stepped through the grand gates for the final time, I knew that I was leaving behind not just a physical place but a part of myself. The experiences and lessons I had gained during my time there would forever shape the trajectory of my life.In the years that have passed since my graduation, I have often reflected on the transformative power of thatpivotal moment when I first set foot on the boarding school campus. It was a daunting and uncertain journey, but one that ultimately led to profound personal growth and lasting fulfillment.The moment I left the comfort and familiarity of my childhood home was not merely a physical departure but a symbolic transition into the realm of adulthood. It was a moment that marked the end of one chapter and the beginning of another—a chapter filled with challenges, triumphs, and a relentless pursuit of knowledge, growth, and connection.And so, I raise a toast to that pivotal moment—the moment I left home and embarked upon the uncharted waters of boarding school life. It was a moment that propelled me into the realm of adulthood, a moment that shaped the very essence of who I am today.。
民航专业术语
民航专业术语A—EATIS Airport Terminal Information Service 机场终端信息服务ATIS Automated(automatic) Terminal Information Service 自动终端情报服务ATM Air Traffic Management 空中交通管理ATN Aeronautical Telecommunications Network 航空电信网ATNP (ICAO)Aeronautical Telecommunication Network Panel (国际民航组织)航空电信网专家组ATO Actual Time Over 实际经过时间ATRK Along-Track Error 沿航线误差ATS Air Traffic Services 空中交通服务ATSC Air Traffic Services Communication 空中交通服务通信ATT Attitude 姿态AUSSAT Australian Satellite 澳大利亚卫星AUTODIN Automated Digital Network 自动化数字网络AUTOVON Automatic Voice Network 自动化话音网络AUX Auxiliary 辅助AVOL Aerodrome Visibility Operational Level 机场能见度运行等级AVPAC Aviation VHF Packet Communications 航空甚高频分组通信AVS Aviation Standards 航空标准AWANS Aviation Weather And NOTAM System 航空气象和航行通告系统AWOP (ICAO)All Weather Operations Panel (国际民航组织)全天候运行专家组AWOS Automated Weather Observing System 自动化气象观测系统AWP Aviation Weather Processor 航空气象处理器AWS Aviation Weather Service 航空气象服务AZ Azimuth transmitter 方位台BBARO Barometric 气压BAZ Back Azimuth 后方位,背航道BER Basic Encoding Rules 基本编码规则BER Bit Error Rate 误码率BIT Built-In—Test 机内测试BITE Built—In-Test Equipment 机内测试设备BOP Bit Oriented Protocol 面向位的协议BPS bits per second 每秒传送位数;每秒比特数BPSK Biphase Shift Keying 两相相移键控BRITE Bright Radar Indicator Tower Equipment 塔台高亮度雷达显示设备BRL Bearing Range Line 方位距离线BSU Beam Steering Unit 天线方位控制组件BUEC Backup Emergency Communications 备用紧急通信C 通信C-Band Approx. 5,000MHz C波段C/A (CA) Code Course Acquisition Code 粗获码(民用的)C/I Carrier—to—Interference Ratio 信号干扰比C/N Carrier—to—Noise Ratio 信噪比CA Conflict Alert 冲突告警CA GPS Course—Acquisition Code 粗捕获码(民用码)CA/MSAW Conflict Alert/Minimum Safe Altitude Warning 冲突告警/最低安全高度警告CAA Civil Aviation Administration, Civil Aeronautical Authority,Civil Aviation Authority 民航局CAAC General Administration of Civil Aviation of China 中国民用航空总局CAASD Center for Advanced Aviation System Development(The MITRE Corporation)(MITRE公司)高级航行系统开发中心CAB Civil Aeronautical Bureau 民航局CARF Central Altitude Reservation Function 中央飞行高度保留功能CARs Civil Air Regulations 民用航空规则CASITAF CNS/ATM implementation task force 新航行系统实施特别工作组CAT Category 仪表着陆等级CATⅠCategory Ⅰ一类仪表着陆CATⅡCategory Ⅱ二类仪表着陆CAT Ⅲa Category Ⅲa 三类a级仪表着陆CAT Ⅲb Category Ⅲb 三类b级仪表着陆CAT Ⅲc Category Ⅲc 三类c级仪表着陆CATC Civil Aviation Training Center 民航培训中心CATMAC Co-operative Air Traffic Management Concept 空中交通管理合作方案CBA Cost/Benefit Analysis 成本效益分析C-BAND The frequency range between 4000 and 8000MHz 4000到8000MHz频段CBI Computer Based Instruction 计算机基本指令CBT Computer—Based Training 计算机辅助训练CC Connection Confirm 联接确认CCA Continental Control Area 大陆管制区CCC 蜂窝式CNS概念CCD Consolidated Cab Display 综合机舱显示器CCIR International Radio Consultative Committee 国际无线电咨询委员会CCITT International Telegraph and Telephone Consultative Committee 国际电报电话咨询委员会CCP Contingency Command Post 应急指挥站CCWS Common controller workstation 通用管制员工作站CD Common Digitizer 通用数字化仪设备CDC Computer Display Channel 计算机显示通道CDI Course Deviation Indicator 偏航指示器CDM Code division multiplex 码分复用CDM Continuous Delta Modulation 连续增量调制CDMA Code Division Multiple Access 码分多址CDT Controlled Departure Times 管制离场时间CDTI Cockpit Display of Traffic Information 驾驶舱交通信息显示CDU Control Display Unit 控制显示组件CEP Circular error probability 圆概率误差CERAC Combined Center Radar Approach Control 雷达进近管制联合中心CFCC Central Flow Control Computer 中央流量管制计算机CFCF Central Flow Control Facility 中央流量管制设施(功能)CFDPS Compact Flight Data Processing System 小型飞行数据处理系统CFWP Central Flow Weather Processor 中央流量气象处理机CFWSU Central Flow Weather Service Unit 中央流量气象服务单元(组件)CHI Computer Human Interface 机人接口CIDIN Common ICAO Data Interchange Network 国际民航组织公用数据交换网CIS Cooperative independent surveillance 合作式独立监视CLAM Cleared Level Adherence Monitoring 放行高度保持监视CLB Climb 爬升CLK Clock 时钟CLNP Connectionless Network Protocol 无连接网络规程(协议)CLR Clear 清除CMC Central Maintenance Computer 中央维护计算机CMD Command 命令CMS Cabin Management System 机舱管理系统CMU Communications Management Unit 通信管理单元CNDB Customized Navigation Database 用户导航数据库CNS Consolidated NOTAM System 综合航行通告系统CNS/ATM Communication Navigation,Surveillance/Air Traffic Management 通信导航监视/空中交通管理CODEC Coder/Decoder 编码器/解码器COM/MET/OPS Communication/ Meteorology/ Operations 通信/气象/运行COMLO Compass Locator 罗盘定位器;罗盘示位信标COMM Communication 通信COMP Compressor 压缩器COMSEC Communications Security 通信保安CON Continuous 连续CONUS Continental, Contiguous,or Conterminous United States 美国大陆本部(四十八州)COP Change Over Point 转换点COP Character Oriented Protocol 面向字符协议COTS Commercial Off-the—Shelf 商业货架产品供应CPDLC Controller Pilot Data Link Communications 管制员驾驶员数据链通信CPFSK Continuous Phase Frequency Shift Keying 连续相位频移键控CR Connection Request 联接申请CRA Conflict Resolution Advisory 冲突解脱咨询CRC Cyclic Redundant Check 循环冗余校验CRCO Central Route Charges Office 中央航路收征费办公室CRM C Reference Model C参考模式CRM Collision Risk Modeling 碰撞危险模型CRM Crew Resource Management 机组人员安排CRT Cathode Ray Tube 阴极射线管CRZ Cruise 巡航CSA Standard Accurate Channel 标准精度通道CSE Course Setting Error 航线设定误差CSMA Carrier Sense Multiple Access (datalink protocol) 载波侦听多址访问C/SOIT Communication/ Surveillance Operational Implementation Team 通信监视运行实施小组(美国)CTA Calculated Time of Arrival 计算到达时间CTA Control Area 管制区CTAS Central Tracon Automation System 中央终端雷达进近管制自动系统CTL Control 控制CTMO Central traffic Management Organization 中央交通流量管理组织CTMO Centralized Traffic Management Organization 中央交通管理组织CTOL Conventional Take Off and Landing 常规起飞着陆CTR Control zone 管制地带CTS Control Tracking Station 控制跟踪站CU Control Unit 控制单元C§W Control and Warning 控制和告警CW Carrier Wave 载波CWI Continuous Wave Interference 连续波干扰CWP Central Weather Processor 中央气象处理器CWSU Center Weather Service Unit 中央气象服务单元DD/A Digital-to—Analog 数/模转换DABS Discrete Addressable Beacon System 离散寻址信标系统DADC Digital Air Data Computer 数字大气数据计算机D—ATIS Digital Automatic Terminal Information Service 数字自动终端信息服务DA Decision Addressing beacon system 决断寻址信标系统DA Demand Assignment 按需分配DA/H Decision Altitude(Height) 决断高度DARC Direct Access Radar Channel 直接存取雷达信道DARP Dynamic Air Route Planning 动态航线计划DARPS Dynamic Aircraft (Air) Route Planning Study 动态飞机航线计划研究DC Departure Clearance 离场放行许可DC Direct Current 直流(电)DCC Display Channel Complex 显示通道组合DCIU Data Control Interface Unit 数据控制接口单元DCL Departure Clearance Delivery 起飞许可传送DCPC Direct Controller Pilot Communication 管制员驾驶员直接通信DES Data Encryption Standard 数据加密标准DF Direction Finder 测向器DFCS Digital Flight Control System 数字飞行控制系统DFDAU Digital Flight Data Acquisition Unit 数字飞行数据采集单元DGCA Director—General Civil Aviation 民航局长DGNSS Differential Global Navigation Satellite System 差分全球导航卫星系统DGPS Differential Global Positioning System 差分全球定位系统DH Decision Height 决断高度DIP Diplexer 双工器DL Data Link 数据链DLAC Data Link Applications Coding 数据链应用编码DLAS Differential GNSS Instrument Approach System 差分GNSS仪表进近系统DLK data link 数据链DLORT FAA Data Link Operational Requirements Team FAA数据链运行要求工作组DMAP ICAO Data Link Mobile Applications Panel(proposed) 国际民航组织数据链移动应用专家组(建议DME Distance Measuring Equipment 测距设备DME/N Distance Measuring Equipment/Normal 标准测距设备DME/P Distance Measuring Equipment/Precision 精密测距设备DMU Data Management Unit 数据管理单元DO(DOC)Document 记录(文件)DOD Department of Defense (美国)国防部DOP Dilution of Precision 精度扩散因子DOT Department of Transportation (美国)运输部DOTS Dynamic Ocean Tracking System 动态海洋跟踪系统DP Disconnect Request 分离拆线请求DPF Data Processing Function 数据处理功能D8PSK Differential Eight—Phase Shift Keying 差分8相移键控DPSK Differential Phase Shift Keying 差分相移键控DRMS Distance Root Mean Square 距离均方根值DRN Document Release Notice 文件发放通告DSB-AM Double Sideband Amplitude 双边带调幅DSDU Data Signal Display Unit 数据信号显示单元DSP Departure Sequencing Program 起飞排序计划;离港排序计划DT Data 数据DTE Data Terminal Equipment 数据终端设备DT&E Development Test and Evaluation 开发测试和评估DTF Data Test Facility 数据检测设备DTG 待飞距离DTN Data Transport Network 数据传输网络DUAT Direct User Access Terminal 用户直接存取终端DVOR Doppler Very high frequency Omni-directional Range 多普勒甚高频全向信标EEANPG European Air Navigation Planning Group 欧洲航行规划小组E—DARC Enhanced Direct Access Radar Channel 增强的直接存取雷达信道EARTS En route Automated Radar Tracking System 航路自动化雷达跟踪系统EASIE Enhanced ATM and Mode S Implementation in Europe 欧洲S模式和增强的空中交通管理实施项目EATCHIP European ATC Harmonization Implementation Program 欧洲空中交通管制协调实施计划EATMS European Air Traffic Management System 欧洲空中交通管理系统ECAC European Civil Aviation Conference 欧洲民航会议ECEF 地心地固坐标EDCT Estimated Departure Clearance Time 预计离港起飞放行时间EET Estimated Elapsed Time 预计经过时间EFAS En route Flight Advisory Service 航路飞行咨询服务EFAS Extended Final Approach Segment 扩展最后进近段EFIS Electronic Flight Instrument System 电子飞行仪表系统EFC Expect Further Clearance 预期进一步放行许可EFIS Electronic Flight Information System 电子飞行情报系统EGNOS European global navigation overlay system 欧洲全球导航重迭系统EHSI Electronic Horizontal Situation Indicator 电子平面状态显示器EIRP Equivalent Isotropic Radiate Power 等效各向同性辐射功率EISA Extended Industry Standard Architecture 扩展的工业标准结构EL Elevation Transmitter 仰角台ELOD En route sector Load 航路扇区负载管制飞机数量ELT Emergency Locator Transmitter 紧急示位发射机EMC Electromagnetic Compatibility 电磁兼容EMI Electromagnetic Interference 电磁干扰ENRI Electronic Navigation Research Institute (日本)电子导航研究所EOF Emergency Operations Facility 应急运行设施EPA Environmental Protection Agency 环境保护署ER Error 误差ERL Environmental Research Laboratories 环境研究实验室ERM En Route Metering 航路计量管制ERN Earth Referenced Navigation 大地参考导航ERP Effective Radiated Power 有效幅射功率ES End System 终端系统ESA European Space Agency 欧洲航天局ESCAN Electronic Scanning(radar antenna)ESMMC Enhanced SMMC 增强的系统维护监视台ESP En route Spacing Program 航路间隔计划EST Estimated message 预计信息ETA Estimated Time of Arrival 预计到达时间ETB Estimated Time of Boundary 预计边界时间ETD Estimated Time of Departure 预计离港时间ETG Enhanced Target Generator 增强的显示目标产生器ETN Estimated Time of Entry 预计进入时间ETO Estimated Time Over 预计飞越时间ETSI European Telecommunications Standards Institute 欧洲电信标准学会EU European Union 欧洲联盟EURATN European ATN 欧洲航空电信网EUROCAE European Organization for Civil Aviation Electronics 欧洲民用航空电子学组织EUROCONTROL European Organization for the Safety of Air Navigation 欧洲航行安全组织(欧安局) EVS Enhanced Vision System 增强视景系统EWAS En—route Weather Advisory Service 航路气象咨询服务FF&E Facilities and Equipment 设施和设备F,E&D Facilities,Engineering,and Development 设施、工程和开发FAA Federal Aviation Administration (美国)联邦航空局FAATC FAA Technical Center (美国)联邦航空局技术中心FAF Final Approach Fix 最终进近坐标FANS ICAO Future Air Navigation Systems (国际民航组织)未来航行系统FANS Special Committee on Future Air Navigation Systems 未来航行系统特别委员会FANS(Phase II)Special Committee for the Monitor—ing and Co-ordination of Develop- ment and Tra nsition Planning for the Future Air Navigation System 未来航行系统监督、协调发展与过渡规划专门委员会FAR Federal Aviation Regulation 联邦航空条例FAS Final Approach Segment 最后进近段FASID Facilities And Services Implementation Document 设施和服务实施文件FCC Flight Communication Center 飞行通信中心FCC Federal Communication Commission 联邦通信委员会FCC Flight Control Computer 飞行控制计算机FDAU Flight Data Acquisition Unit 飞行数据收集单元FDDI Fiber Distributed Data Interface 光纤分布数据接口FDEP Flight Data Entry and Printout 飞行数据输入和输出FDI Fault Detection and Isolation 故障检测和隔离FDIO Flight Data Input/Output 飞行数据输入/输出FDM Frequency Division Multiplex 频分复用FDMA Frequency Division Multiple Access 频分多址FDP Flight Data Processor 飞行数据处理器FDPS Flight Data Processing System 飞行数据处理系统FDR Flight Data Recorder 飞行数据记录仪FEATS Future European ATS System Concept 未来欧洲空中交通服务系统方案FEATS ICAO Future European Air Traffic Management System 国际民航组织未来欧洲空中交通管理系统FEC Forward Error Correction 前向纠错FGC Flight Guidance Computer 飞行引导计算机FGCC Federal Geodetic Control Committee 联邦大地测量管理委员会FI Flight Inspection 飞机校验FIC Flight Information Center 飞行信息中心FIFO First In—First Out 先入先出FIFO Flight Inspection Field Office 飞行检查现场办事处FIR Flight Information Region 飞行情报区FIS Flight Information Services 飞行情报服务FISA Automatic Flight Information Service 自动飞行信息服务FL Flight Level 飞行高度层FLIR Forward Looking Infra-red Detection 前视红外线探测FM Frequency Modulation 调频FMC Flight Management Computer 飞行管理计算机FMEA Failure Mode Effects Analysis 故障模式效果分析FMS Flight Management System 飞行管理系统FMS Frequency Management System 频率管理系统FMSG Frequency Management Study Group 频率管理研究组FMU Flight Management Unit 飞行管理组件FMU Flow Management Unit 流量管理单元FOC Full Operation Capability 全运行能力FOM Figure of Merit 性能指数FPA Flight Path Angle 航迹倾角FPD Flight Plan Data 飞行计划数据FPS Military Primary Radar 军用一次雷达FREQ Frequency 频率FRP Federal Radio navigation Plan 联邦无线电导航计划(美国)FS Functional Statement 功能描述FSAS Flight Service Automation System 飞行服务自动化系统FSDPS Flight Service Data Processing System 飞行服务数据处理系统FSK Frequency Shift Keying 频移键控FSP Flight Strip Printer 飞行进程单打印机FSS Flight Service Station 飞行服务站FSTN Federal Security Telephone Network 联邦政府保安电话网络FT Functional Test 功能测试FTE Flight Technical Error 飞行技术误差FY Fiscal Year 财政年度;会计年度GGA General Aviation 通用航空GA Ground annta 地面天线Gatelink Datalink for packed aircraft 网关数据链路GADS Generic Aircraft Display System 通用航空器显示系统GAIT Ground—based Augmentation and Integrity Technique 陆基增强和完好性技术GAO Government Accounting Office (联邦)政府会计署GBA Geostationary broadcast area 静止卫星广播区域GCAS Ground Collision Avoidance System 地面防撞系统GCS Ground Controlled Approach 地面控制系统GDLP Ground Data Link Processor 地面数据链处理器GDOP Geometic Dilution of Position 位置几何扩散因子GDOP Geometry Dilution of Precision 精度几何扩散因子GEO Geostationary 静地的GEO Geostationary Earth Orbit 相对地球静止轨道静止卫星GES Ground Earth Station 地面地球站GFE Government-Furnished Equipment 政府提供的设备GHz Giga hertz 千兆赫兹GIB GNSS integrity broadcast 全球导航卫星系统完好性数据广播GIC GNSS Integrity Channel 全球卫星导航系统完好性通道GICB Ground—initiated Comm—B 地面启动的B类通信GIRU Ground Interrogator Receiver Unit 地面应答机接收单元GIS Geographical Information System 地理信息系统GLONASS Global Orbit Navigation Satellite System 全球轨道导航卫星系统(俄罗斯)GLS GPS Landing System GPS着陆系统GM Guidance Material 指导材料GMC Ground Movement Control 地面活动管制GMSK Gaussian Minimum Shift KeyingGMT Greenwich Mean Time 格林威治时间GNAS General NAS 综合国家空域系统GND Ground 地GNE Gross Navigational Error 总导航误差GNR Global Navigation Receiver 全球导航接收机GNSS Global Navigation Satellite System 全球导航卫星系统GNSSP ICAO Global Navigation Satellite Systems Panel 国际民航组织全球卫星导航系统专家组GPSSU Global Positioning System Sensor Unit 全球定位系统(GPS)传感器组件GOES Geostationary Operational Environmental Satellite 静地运行环境卫星GOS Grade of Service 服务等级GOSEP Government Open Systems Interconnection Profile 政府开放系统互联结构GOSIP Government Open systems Implementation Profile 政府开放系统实施结构GP Glide—Path 下滑道GPIP Glide-Path Intercept Point 下滑道截获点GPIWP Glide Path Intercept Waypoint 滑行道切入点GPO/GPI General Purpose Output/General Purpose Input 通用输出/通用输入GPS Global Positioning System 全球定位系统GPWS Ground Proximity Warming System 近地告警系统GREPECAS Caribean/South American Planning and Implementation Regional Group 加勒比/南美洲计划和实施区域小组GRS Ground-Reference Station 地面基准站GRS80 Geodetic—Reference System-80 大地基准系统-80GS(G/S)Glide Slope 下滑坡度GS Ground Speed 地速GSA General Services Administration 综合服务管理局(联邦政府下属)GSL General Support Laboratory 综合保障实验室GSM Global System (or Mobile) Communication 全球通信系统GWS Graphic Weather Service 图形气象服务HH Homing radio beacon 归航无线电信标HARN High Accuracy Reference Network 高精度参考网HAT Height Above Touchdown 高于接地点的高度HCI Human Computer Interface 人机接口HDD Head Down Display 下视显示器HDG Heading 航向HDOP Horizontal Dilution Of Precision 精度水平扩散因子HEMP High Altitude Electromagnetic Pulse 高空电磁脉冲HEO High Elliptical Orbit 高椭圆率轨道HF High Frequency(3—30MHz)高频HFDL High Frequency Data Link 高频数据链HGA High Gain Antenna 高增益天线HIRF High Intensity Radiated Fields 高强度辐射场HIWAS Hazardous In—flight Weather Advisory Service 飞行时遇危险天气的咨询服务HMI Human Machine Interface 人机接口HPA high power amplifier 高功率放大器HPF Horizontal Position Fix Error 水平位置坐标误差HSI Horizontal Situation Indicator 水平位置指示器HUD Head—up Display 平视显示仪HUI Head up DisplayHVAC Heating, Ventilating, And air Conditioning 加热,通风和空调Hybird GNSS/ILS Precision Approach/Landing based on combination of GNSS localizer and ILS glide pat h 基于GNSS航向和ILS下滑道组合的精密进近/着陆系统Hz Hertz 赫兹IIA5 International Alopabet 5 国际字母表第5号码IACA International Air Carrier Association 国际航空公司协会IACSP International Aeronautical Communication Service Provider 国际航空通信业务提供者IAF Initial Approach Fix 初始进近点(坐标)IAG International Association of Geodetical 国际测地协会IAIN International Association of Institutes of Navigation 国际导航学会联合会IAOPA International Council of Aircraft Owner and Pilot Associations 航空器企业主和驾驶员协会国际委员会IAP Instrument Approach Procedure 仪表进近程序IAR Intersection of Air Routes 航路交叉点IAS Indicated Air Speed 指示空速IASC Inter Area Speech Circuit 区域间话音线路IATA International Air Transport Association 国际航空运输协会IBAC International Business Aviation Council 国际商业航空委员会ICAO International Civil Aviation Organization 国际民航组织ICCAI(A)International Co-ordination Council of Aerospace Industries Associations 国际宇航工业联合会合作委员会ICD Interface Control Document 接口控制文件ICO Interim Circle Orbit 中高度圆轨道ICSS Integrated Communications Switching System 综合通信转换系统ID Identifier(Identification) 标识码(编码、识别标志)ID Instrument Departure 仪表离场IDSG ICAO Internet Working Standards Drafting Group 国际民航组织网间标准起草小组IEEE Institute of Electrical and Electronic Engineers 电气和电子工程师学会IF Intermediate approach Fix 中间进近定位点IFALPA International Federation of Airline Pilots Associations 航空公司驾驶员协会国际联合会IFATCA International Federation of Air Traffic Controllers' Associations 空中交通管制员协会国际联合会IFCN Interfacility Flow Control Network 设施(单位)间流量管制网络IFF 敌我识别器IFM Integrated Flow Management 综合流量管理IFR Instrument Flight Rules 仪表飞行规则IFRB International Frequency Registration Board 国际频率注册委员会IFSS International Flight Service Station 国际飞行服务站IBM International Business Machines (美国)国际商用机器公司ILA International Law Association 国际法律协会ILS Instrument Landing System 仪表着陆系统IMA Integrated Modular Avionics 集成化模块式航空电子设备IMAWP Initial Missed Approach Waypoint 起始复飞航路点IMC Instrument Meteorological Conditions 仪表气象条件IMCS Interim MCS 过渡性监控/管制软件IMO International Maritime Organization 国际海事组织IMS Integrity Monitoring System 完好性监视系统IN Information Need 信息需求INMARSAT International Marine Satellite Organization 国际移动卫星组织(原名国际海事卫星组织)INS Inertial Navigation System 惯性导航系统INS Insert 插入INTNET Integrated Data Communications Network 集成化数据通信网络I/O input/output 输入/输出IOACG Informal Indian Ocean Air Traffic Services Coordinating Group 非正式印度洋空中交通服务协调小组IOC Initial Operational Capability 初始运行能力IOD GPS Issue of Data 全球定位系统数据发布ION Institute of Navigation 导航学会IOR Indian Ocean Region 印度洋区域IOT§E Initial Operational Test and Evaluation 初始运行测试和评估IP Internetwork Protocol 网络间协议IPACG Informal Pacific Air Traffic Control Coordination Group 非正式太平洋空中交通管制协调小组IRS Inertial Reference System 惯性参考系统ISA International Standard Atmosphere 国际标准大气ISDN Integrated Service Digital Network 综合业务数字网络ISNS 国际卫星导航服务ISO International Organization for Standardization 国际标准化组织ISPACG Informal South Pacific ATS Co—Ordination Group 非正式南太平洋空中交通服务协调小组ISSS Initial Sector Suite Subsystem 起始扇区管制席位分系统ITU International Telecommunication Union 国际电信联盟ITWS Integrated Terminal Weather Service 综合终端气象服务IVAD Integrate Voice and Data 综合话音和数据(通信数据链)IVRS Interim Voice Response System 过渡性话音响应系统IWP Interim Working Party 临时工作组JAWS Joint Airport Weather Studies 联合机场气象研究JCAB Japan Civil Aviation Bureau 日本民航局JAWS Joint Airport Weather Studies 联合机场气象研究JPO Joint GPS Planning Office 联合GPS规划办公室JSS Joint Surveillance System 联合监视系统Kbps Kilo bits per second 千位每秒KDP Key Decision Point 关键性决定点kHz Kilohertz 千赫KLAAS Kinematics Local Area Augmentation System 动态地面局域增强系统KLADGNSS Kinematics Local Area Differential GNSS 动态地局域差分GNSSkW Kilowatt 千瓦kWh Kilowatt hour 千瓦小时LL1 1575.42MHz L-Band carrier L1频率L2 1227。
计算地震初至波视出射角方法
13 第 1 期 何 斌等 : 计算地震初至波视出射角方法
。
真出射角是地震波入射射线与地面的夹角 , 视 出射角是地面位移矢量与地面的夹角 。由于地震波 在地面上形成了反射波 , 所以视出射角不等于入射 波的真出射角 。根据记录到的地面位移垂直分量和 水平分量的比值可确定视出射角 。若将地球表面视 为自由表面 ,视出射角和真出射角的关系与地壳介 质的泊松比有关 [ 2 ] 。根据真出射角和视出射角的关 系 ,对于单台可用较清晰三分向初动记录计算其视 出射角 ,再经查表[ 3 ] 可获得真出射角值和震源深度 。 传统的出射角法地震定位[ 4 ] 仅利用单台资料 , 依赖 于单台三分向位移记录 。由于该方法是一个近似计 算方法 ,具有较大的误差 , 得到的结果无法进行评 价 ,难以保证求得的震源深度的精确度 。 数字地震仪具有非线性失真小 ,系统噪音低 ,信 噪比较高等优点 。随着数字地震台网的建立和运行 获得了大量的地震波形资料 , 为地震的初至波视出 射角的计算提供了条件 。视出射角的计算方法是本 文研究内容 ,通过对理论地震波形和实际记录波形 在时间域和频率域中进行初至波视出射角计算研 究 ,分析其影响因素 , 验证其方法的正确性和可行 性。
式 ( 3) 和式 ( 4) 分别表示地震波的速度记录和加速度 记录 。一般在微震记录时采用的是地面运动速度记 录 ,而在强震记录时采用的是地面运动加速度记录 。 视出射角的计算公式[ 5 ] 为 │uz ( t) │ ( 5) tan e = 2 2
u x ( t) + u y ( t)
根据 P 波的质点运动方向 ,在 t 时刻质点的位移 、 速 度和加速度向量是平行的 , 所以无论是用哪种记录 ( 3) 和 ( 4) 资料都可以直接计算视出射角 。把式 ( 2) 、 分别代入式 ( 5) 有 │uz ( t) │
地震预警中两种利用卓越周期估算震级方法的比较_宋晋东
第6 期
宋晋东, 等: 地震预警中两种利用卓越周期估算震级方法的比较
175
low-pass filtering or not. We recommend τ c method using 3 seconds signal after the Pwave arrival as the preferential magnitude estimating method for earthquake early warning. Key words: earthquake early warning; predominant period; magnitude; filter
震预警系统测试, 结果表明利用单台数据估算震级的平均误差为 0. 70 震级单位, 若采用靠近震中最近的 10 个台站的震级估算平均结果, 平均误差可以降到 0. 35 震级单位, 因此 Allen 和 Kanamori 建议可以用各个台
176
地
震
工
程
与
工
程
振
动
第 32 卷
[24 ] 站震级估算的平均值来降低震级估算的误差 。 Olson 和 Allen 运用全球地震数据分析了 τ pmax 与震级的比
Park 等[35]利 例关系, 震级估算误差为 0. 54 震级单位, 并且大部分 τ pmax 值在 P 波到来后的 2 秒内即可获得, 用韩国地震数据也验证了 τ pmax 与震级的比例关系, 现在, τ pmax 方法已被应用于美国加州地震预警测试系
2 i
( 1) ( 2)
x i 为竖向速度记录( 经过低通和高通滤波, 高通滤波器是为了消除地震记录积分或微分过程中产生的低频 漂移现象, 低通滤波器的高频截止频率一般为 3Hz ) , α 为平滑参数, 是一个接近于 1 的参数, 一般取值为 0 . 99 。
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Determination of P – wave arrival time of acoustic eventsTomáš Svitek1, Vladimír Rudajev2 and Matěj Petružálek3The new approach to the P-wave arrival time determination based on acoustic emission data from loading experiments is tested. The algorithm used in this paper is built on the STA/LTA function computed by a convolution that speeds up the computation process very much. The picking process makes use of shifting of temporary onset until certain conditions are fulfill and as a main decision criterion on the threshold exceeding of the STA/LTA derivation function is used. The P-wave onset time is determined in a selected interval that corresponds to the theoretical propagation of elastic wave in the rock sample. Results obtained by our algorithm were correlated with data acquired manually and a high order statistic software as well.Key words: Onset detection, Automatic picker, Acoustic emission, Loading experiments, STA/LTAIntroductionThe evaluation of stability of underground engineering structures is one of significant tasks of geomechanics. For the development and verification of effective methods of assessing the deformation characteristics, it is advisable to carry out their research under laboratory conditions, which enable us to simulate the process of stress state growth up to the level of their own strength. As to the rocks, representing a heterogeneous discontinuous medium with primary cracks and places of different mechanical strength, the distribution of the stress field is inhomogeneous with higher local values especially in the vicinity of so-called “stress concentrators”. During the loading of rock specimens, the local strength will be exceeded in these places and brittle ruptures will be created, which leads to the elastic wave emission. These points of brittle ruptures are sources (foci) of elastic wave radiation ranging from acoustic to ultrasonic frequencies. Events like these are referred to as the “acoustic emission” (AE). The observation of the acoustic emission process is based on the monitoring via a geophone net, located on the surface of the studied rock specimen. The location of acoustic foci and the monitoring of their migration during loading until a final destruction of the rock specimen provides a significant information about foci clustering within the areas of predisposed places of future final rupture. Acoustic emissions and the location of their foci was studied by Lockner (1993), Lockner and Byerlee (1977), Vilhelm et al. (2008), Veverka J., Rudajev V. (2004). The accuracy of the location depends on the knowledge of the velocity model as well as on the accuracy of determining the P – wave onset time. Therefore, the accuracy of determining the time of the onset is very important and often poses a difficult problem.This paper is concerned with the determination of the time of the first arrivals of P – waves important for localizing acoustic events occurring during the rock specimens loading. This topic is also involved in many publications, based on different principles. The methods most frequently used for the P – wave time determination are, for example: the STA/LTA ratio (short-term average/long-term average) by Allen, R. (1982), Baer, M., Kradolfer, U. (1987), SNR (signal-to-noise ratio) by Zuolin Chen (2005), HOS (high - order statistics) by Lokajicek, T., Klima, K. (2006), and the AIC criterion (Akaike Information Criterion) by Sedlak et al. (2009).Background of the Pick – Tester (PT) MethodIn general, it always stands good that signal is transformed to a characteristic function (CF) which creates the signal envelope. The time of the first arrival is then determined on this envelope by using specified criteria.The procedure presented in this paper is based on the STA/LTA principle (Allen, 1982). The characteristic function is computed using the following equation1Mgr. Tomáš Svitek, Charles University in Prague, Faculty of Science, Albertov 6, 128 43 Praha 2 also Institute of Geology Academy of Sciences of the Czech Republic, v.v.i., Rozvojová 269, 165 00 Praha 6 - Lysolaje, Czech Republic, svitek@gli.cas.cz2RNDr. Vladimír Rudajev DrSc., Institute of Geology Academy of Sciences of the Czech Republic, v.v.i., Rozvojová 269, 165 00 Praha 6 - Lysolaje, Czech Republic3Mgr. Matěj Petružálek, Charles University in Prague, Faculty of Science, Albertov 6, 128 43 Praha 2 also Institute of Geology Academy of Sciences of the Czech Republic, v.v.i., Rozvojová 269, 165 00 Praha 6 - Lysolaje, Czech Republic(Review and revised version 20. 10. 2010)145146()()()()()221−−+=i y i y K i y i CFwhere y is the input signal and the second part of the equation is its derivative. K is the weight constant, which reflects the sampling frequency and the noise characteristic of the seismic receiver,()()()()∑∑==−−=n i ni i y i y i y i K 111 ,where n is the number of signal samples. The STA/LTA ratio was chosen as the detector. It is the average of the CF amplitude in the short- (long-) time window. The calculation of the real STA and LTA values then yields an average of the values of the characteristic function in a time window of a certain length. These windows have shifted subsequently along the characteristic function. For this operation, it is necessary to use cyclic algorithms repeated depending on the quantity of the data ( number of traces), when the first arrival time is determined. All algorithms were realized in the Matlab software. Therefore, this software is not optimized for using cyclic operations; the convolution was used for computing the STA and LTA functions.The convolution is defined by the equation ()()()∫∞∞−−=τττd s t s t y 21 and is noted as ()()()t s t s t y 21∗=, where s 1 is the rectangular signal with the length STA or LTA and s 2 is the acoustic (ultrasonic) signal. The signal s 2 is a discrete series of numbers and the convolution equation can then be expressed in the following form; ()()∑−=j j s j k s k y 21)( ; 0>−j k . Replacing the cyclic algorithmsby the convolution accelerates the calculation. Consequently, the criteria for determining the times of the firstarrivals enter the computation process. Figure 1 shows a simplified block diagram of particular steps of this process.Fig. 1. Block diagram of the arrival time assessment.During our loading experiments, the acoustic emission data were recorded by an 8-channel piezoceramicsystem. For this reason, the first step of the computation process is to find the trace on which the acoustic event was first registered. Based on this fact, it is possible to apply considerations of rock specimen geometry and then to determine the P–wave time arrival. The whole process is based on the values and shape of the STA/LTA ratio function, whereas the length of the LTA window is 100 points (10 µs) and the length of the STA window is 10 points (1 µs).In the following, the criteria of determining the arrival time will be described in a more detail.Step 1 – STA/LTA level determinationThe first step is the dynamical determination of the STA/LTA level. When this level is exceeded,the raw arrival time is assessed. For this purpose the median of the maxima of all eight traces is computed. The STA/LTA level is then established as 15 % of the median value. Two extreme cases can occur:Strong event – The STA/LTA level is higher than the smallest maximum of any STA/LTA function.In this case the decision level is established as the smallest value of maxima of the STA/LTA function.Weak event – The STA/LTA level of 15 % of the median is not high enough so that the decision levelis established by a predefined empirical value.The value of the level then reflects the magnitude of the registered AE event.Step 2 – STA/LTA derivation and its peaksIn this step, the STA/LTA function is derived (hereinafter called “Derivation”) and its maximumis determined again. Consequently, the level of the Derivation is determined for every trace. In this case, the decision level is established as 1/3 of the Derivation maximum.147Step 3 – P – wave pick allocated to the main or local maximum of DerivationPoints whose amplitudes of the STA/LTA and Derivation functions exceed their levels determinethe peaks which indicate a certain increase of the signal.Next in the process, only the peaks of the Derivation whose maxima are higher than or equal to a halfof the main maximum are considered. According to the number of peaks which satisfy this criterion, the following cases can be identified:a. Only one peak found; raw P – wave pick is placed to the point of Derivation maximum,b. More than one peak found and at once STA/LTA ratio in the place of the local maximum of previouspeak is higher or equal to STA/LTA level and at once distance between last two peaks is shorter than100 samples (10 µs); raw P – wave pick is placed to the point of the local Derivation maximumof the previous peak (Fig. 2c),c. None of the previous cases applies; raw P – wave pick is placed to the point of the main Derivationmaximum.Using this procedure we assessed the raw P – wave picks, which are placed to a certain Derivativemaximum.Step 4 – Trigger trace determinationAll these steps (Steps 1 – 3) lead up to the best possible determination of the trace, where the signal wasrecorded as the first, so-called, trigger trace. Once the trigger trace is known, the parameters of the specimen geometry can be applied in the computation.Step 5 – Determination of the theoretical signal propagation time in the rock specimenWith a view to the mutual distance of sensors, we can compute the theoretical propagation timeof elastic waves in the rock specimen and determine the travel-time limits, in which the signal has to reach the sensor. Using the 8-channel system, we obtain 28 mutual sensor distances from the following equation:()()()222j i j i j i ij z z y y x x r −+−+−=, i = j= 1…8, i ≠j, We then compute the theoretical time of propagation from the reference (trigger) sensor (S R ) to the othersensors (S i ) using the equation vr t Ri S S =k R , i=1, 2,...7, where t SRSK = t SR – t SK and v is the P – wave velocity in the rock specimen. This formula is, in general, valid in an isotropic medium. Hence, since most rocks are more or less anisotropic, the previous formula needs to be modified with respect to the real value of rock anisotropy. The problem of anisotropy is discussed in more detail for example in Petružálek et al. 2007. With regard to the anisotropy, we can express the previous equation in the following form:P vr t Ri S S =k R where P is the parameter of the anisotropic velocity ellipsoid represented by a 3 x 3 matrix of semi-axis vectors of this ellipsoid. We thus obtain the theoretical propagation times for every sensor and can determine the time interval (Fig. 2c - red part of STA/LTA) on every trace, for which the relation ()2,1R k R k ⋅+<S S S S t t t , where t Sk is the time measured at the k-th sensor and t SR is the arrival time at the reference sensor, is valid. The lower value of the time interval is limited by the arrival time on the trigger trace. The real time of the signal has to be looked for in the interval defined by these rules. Of course, we need to know the velocity model of the specimen under examination perfectly. This model is obtained from the ultrasound radiation. During the loading, the parameters of the velocity model can vary; hence the coefficient 1.2 was applied in the previous relation. This coefficient was determined empirically.Step 6 – Possible pick shiftIn this part of the algorithm, the shape of the STA/LTA function will be analyzed and the pick can bepossibly shifted to the previous peak. This step is applied in situations when the signal is rising very slightly. If this situation occurs, it is possible that the main Derivation maximum is not at the first peak but on any following peak of STA/LTA. If any peak of STA/LTA exists before the point of the Derivation maximum, and the mutual distance of these two peaks is less than 25 samples (2.5 µs), it is recognized by the procedure in this step and the pick is shifted to the previous STA/LTA peak (Fig. 2c). Repeating of this shifting procedure depends on the number of relevant STA/LTA peaks.148Steps 7 – Final pick determinationIn the last step, we analyze the shape of the real signal in the vicinity of the temporary raw pickand, if necessary, the pick is again shifted to one of the characteristic points of the signal (maximum, minimum or plateau) and the final P – wave arrival time is determined.Figure 2 shows the individual steps of the algorithm mentioned above for a better understanding.• Grey horizontal line – STA/LTA levelcalculated according to the Step 1 (Fig. 2c)• Purple horizontal line - Derivation levelcalculated according to the Step 2 (Fig. 2c)• According to the Derivation functionwe find the raw P – wave pick whereaswe assume that the arrival time does notoccur after the main Derivation maximum(purple cross) calculated accordingto the Step 3 (Fig. 2c).• Red part of STA/LTA calculated accordingto the Step 5 (Fig. 2c)• The figure indicates that the Derivationmaximum (purple cross) is the incorrectdetermination of the arrival time. For thisreason, the shape of the STA/LTA functionis analyzed (Step 6). This function haslarger peaks in comparison withthe Derivation function. As peaksof the STA/LTA function, we consideronly peaks whose amplitudes are higherthan the estimated STA/LTA level (greyline). If the distance between twoneighboring peaks is less than 25 samples(2,5 µs), the P – wave pick shiftsto the place where the previous peakcrosses the STA/LTA level; • Black cross calculated according to the Step 7Results and discussionThe algorithm of Pick-Tester (PT) program is tested on a data file, obtained during the loadingof a migmatite rock specimen. The 950 AE events (7600 traces) were chosen from the data recorded during this experiment. The P- wave arrival times were manually picked from these traces. These data served as a model data file to develop the algorithm for the automated arrival time determination in the PT program.The P – wave arrival time difference is the main criterion for the resultant evaluation. The qualityof the picks will be evaluated by comparing the times manually determined by a human operator. We assume these picks to be correct. Another criterion is a comparison with times obtained using the HOS method (Lokajíček, Klíma, 2006). The correctness of the picks determination is reflected in the location residuum of the individual AE events.In the following figure 3, one can see a general view of the user interface of the Pick-Tester program.This figure shows the comparison of P – wave arrival times determined by different methods. In the main graph (left side), there are 8 records of one AE event. The manual pick on each signal is marked in the red color, the HOS pick in blue and the PT pick in black. The green cross indicates the trigger trace. The right-hand side of the figure shows a detail of the selected trace (upper graph), its STA and LTA functions (middle graph) and the STA/LTA function with its Derivation function (bottom graph). In the upper part of the interface are situated control buttons which can be used to set the length of the STA and LTA windows and allow the movement in the data sets. A B CFig. 2 Procedure explanation (A – recorded signal, B – STA and LTA functions, C – STA/LTA and its Derivation; x-axis units [samples]149Fig. 3. Preview of picking program Pick-tester.Figure 4 shows the results of the whole data set (950 AE events ~ 7600 traces). Histograms in this figurerepresent the absolute value of the arrival time difference determined manually, by the HOS software and by the PT program. The measure of the “x” axis is in the samples; 1 sample ~ 0.1 µs (sampling frequency 10 MHz).0102030absolute valule of arrival time differences [samples]0400800120016002000c o u n t 020406080100[%]Histograms of arrival time differences0102030absolute value of arrival time differences [samples]04080120c o u n t 020*********[%]Histograms of mean arrival times differences on eventsFig. 4. Histograms of absolute values of arrival time differences assessed by HOS software, PT and manual; x-axis units [samples],legend is valid for both graphs.The histograms in Fig. 4a represent the absolute value of the time difference individually for eachsignal. The histograms in Fig. 4b represent the absolute value of the mean time difference for 8 records of one AE event. The cumulative curves indicate that the PT picks agree better with the manual picks (78.7 % picks with 10 samples error) than the HOS method picks (only 66.8 % picks with 10 samples error).One advantage of the PT method is its computation speed. Computation of the dataset used, i.e.7600 signals, takes only 75 seconds.150Another parameter that can be used to evaluate the accuracy of the automated picks is the locationresiduum of the AE events. The location algorithm is based on a simple and reliable grid search method. The modified location method with the L1 norm was used, i.e. the minimum sum of the power of time differences is replaced by the minimum sum of the absolute values of time residues. By comparing the residual times of the manual, HOS and PT picks, one can find how accurate the individual kinds of picks are. The comparison is shown in Fig 5.010*******[samples]010203040010203040010203040[count]204060801002040608010020406080100[%]Histograms of location residuesA B CFig. 4. Histograms of location residues of manual (A), PT (B) and HOS (C) picks.The residues computed from the manual picks are shown in Fig. 5A, the HOS (moment) residuesin Fig. 5C and the PT residues in Fig. 5B. The comparison of location residues displays a similarly successful sequence as in the case of the time difference comparison. If the value of 100 samples (10 µs) is taken to be the criterion of the pick’s quality, the manual picks fit this criterion in 83.3 % of the cases, the PT picks in 74.4 % and, finally, the HOS picks fit only in 58.1 % of all AE events.ConclusionsIn this paper, a new derived method for determining the P-wave time arrivals is presented,and its application is demonstrated on the acoustic signals occurring during the rock specimen loading. This method of automated picking by the Pick-Tester program allows to analyse large volumes of data in a relative short time. The accuracy of the automated picks is in a very good agreement with the manually determined picks. The time values determined by both methods differ by less than 1 µs in 78 % cases. The final locations of the AE events display a similar agreement. However, manual processing of such large data files is very time-consuming and practically unworkable. It has been found that the approach used in the Pick-Tester program yields better results than the high-order statistics (HOS) method which is able to work automatically as well.AcknowledgmentThis paper was partially supported by the Grant Agency of the Academy ofSciences of the Czech Republic, Project No. IAA300130906, by the InstitutionalResearch Plan No. AVOZ 30130516 of the Institute of Geology, AS CR, v.v.i. andby the Research Project of the Ministry of Education No. MSM 0021620855. Weare grateful to RNDr. Tomáš Fischer PhD. and Ass. Prof. RNDr. Jan Vilhelm,CSc. for their help with creating of PT algorithm and Ing. Tomáš Lokajíček, CSc.for providing data from HOS software.ReferencesAllen, R.: Automatic phase pickers: their present use and future prospects. Bulletin of the Seismological Society of America, Vol. 72, No. 6, 1982, p. S225-S242.Baer, M., and Kradolfer, U.: An automatic phase picker for local and teleseismic events. Bulletin of the Seismological Society of America, Vol. 77, 1987, p. 1437-1445.Chen, Z.: A multi-window algorithm for automatic picking of microseismic events on 3-C data. SEG Expanded Abstracts 24, 2005, p. 1288.Lockner, D.A., and Byerlee, J.D.: Acoustic emission and creep in rock at high confining pressure and differential stress. Bull. of the Seismological Society of Amer., Vol. 67, 1977, p. 247-258.Lockner, D.: The role of acoustic emission in the study of rock fracture. Int. J. Rock Mech. Min. Sci.Geomech. Abstr., Vol. 30, No. 7, 1993, p. 883–899.Lokajícek, T., Klíma, K.: A first arrival identification system of acoustic emission (AE) signals by means of a high-order statistics approach. Measurement Science and Technology, Vol. 17, No. 9, 2006, p. 2461-2466.Petružálek, M., Vilhelm, J., Lokajíček, T. and Rudajev, V.: Assessment of p-wave anisotropy by means of velocity ellipsoid, Acta Geodyn. Geomater., Vol. 4, No. 3, 2007, p. 23-31.Sedlak, P., Hirose, Y., Khan, S.A., Enoki, M., and Sikula, J.: New automatic localization technique of acoustic emission signals in thin metal plates. Ultrasonics, Vol. 49, 2009, p. 254–262.Veverka, J., Rudajev, V.: Evaluation of ultrasound emission foci in loading rock samples. Acta Geodynamica et Geomaterialia, Vol. 1, No. 1 (123), 2004, p. 103-110.Vilhelm, J., Rudajev, V., Lokajíček, T., Veverka, J.: Correlation analysis of ultrasound emission from loaded rock samples – the study of interaction of microcracking nucleation centers. 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