XMM-Newton EPIC and OM Observations of Her X-1 over the 35 d Beat Period and an Anomalous L

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The Uncertainty in Newton's Constant and Precision Predictions of the Primordial Helium Abu

a r X i v :a s t r o -p h /0310699v 3 13 F eb 2004The Uncertainty in Newton’s Constant and Precision Predictions of the PrimordialHelium AbundanceRobert J.ScherrerDepartment of Physics and Astronomy,Vanderbilt University,Nashville,TN37235The current uncertainty in Newton’s constant,G N ,is of the order of 0.15%.For values of the baryon to photon ratio consistent with both cosmic microwave background observations and the primordial deuterium abundance,this uncertainty in G N corresponds to an uncertainty in the primordial 4He mass fraction,Y P ,of ±1.3×10−4.This uncertainty in Y P is comparable to the eﬀect from the current uncertainty in the neutron lifetime,τn ,which is often treated as the dominant uncertainty in calculations of Y P .Recent measurements of G N seem to be converging within a smaller range;a reduction in the estimated error on G N by a factor of 10would essentially eliminate it as a source of uncertainty the calculation of the primordial 4He abundance.Big Bang nucleosynthesis (BBN)represents one of the key successes of modern cosmology [1,2].In recent years,the BBN production of deuterium has emerged as the most useful constraint on the baryon density in the universe,both because of observations of deuterium in (presumably unprocessed)high-redshift QSO absorption line systems (see Ref.[3],and references therein),and the fact that the predicted BBN yields of deuterium are highly sensitive to the baryon density.These arguments give a baryon density parameter Ωb h 2,of [3]Ωb h 2=0.0194−0.0234,(1)which is in excellent agreement with the baryon den-sity derived by the WMAP team from recent cosmic mi-crowave background observations [4]:Ωb h 2=0.022−0.024.(2)Given these limits on the baryon density,BBN predicts the primordial abundances of 4He and 7Li.Because the 4He abundance is particularly sensitive to new physics beyond the standard model,a comparison between the predicted and observed abundances of 4He can be used to constrain,for example,neutrino degeneracy or extra relativistic degrees of freedom (see,e.g.,Refs.[5,6]).For this reason,it is useful to obtain the most accurate possible theoretical predictions for the primordial 4He mass fraction,Y P .The primordial production of 4He is controlled by the competition between the rates for the processes which govern the interconversion of neutrons and protons,n +νe ↔p +e −,n +e +↔p +¯νe ,n ↔p +e −+¯νe ,(3)and the expansion rate of the Universe,given by˙R3πG N ρ1/2.(4)In BBN calculations,the weak interaction rates are scaled oﬀof the inverse of the neutron lifetime,τn .When these rates are faster than the expansion rate,the neutron-to-proton ratio (n/p )tracks its equilibrium value.As the Universe expands and cools,the expan-sion rate comes to dominate and n/p essentially freezes out.Nearly all the neutrons which survive this freeze-out are bound into 4He when deuterium becomes sta-ble against photodisintegration.Following the initial calculations of Wagoner,Fowler,and Hoyle [7],numer-ous groups examined higher-order corrections to the 4He production.The ﬁrst such systematic attempt was un-dertaken by Dicus et al.[8],who examined the eﬀects of Coulomb and radiative corrections to the weak rates,ﬁnite-temperature QED eﬀects,and incomplete neutrino ter investigations included more detailed ex-amination of Coulomb and radiative corrections to the weak rates [9,10,11,12],ﬁnite-temperature QED ef-fects [13],and incomplete neutrino decoupling [14],as well as an examination of the eﬀects of ﬁnite nuclear mass [15].These eﬀects were systematized by Lopez and Turner [16](see also Ref.[17]),who argued that all the-oretical corrections larger than the eﬀect of the uncer-tainty in the neutron lifetime had been accounted for,yielding a total theoretical uncertainty ∆Y P <0.0002.Assuming an uncertainty of ±2sec in the neutron life-time,the corresponding experimental uncertainty in Y P is ∆Y P =±0.0004.Similar results were obtained in Ref.[17].Two relevant changes have occurred since the publica-tion of Refs.[16,17].First,the estimated uncertainty in the neutron lifetime has decreased,with the current value being [18]τn =885.7±0.8sec .(5)Second,the estimated uncertainty in the value of G N has increased .The value currently recommended by CO-DATA (Committee on Data for Science and Technology)is [19]G N =6.673±0.010×10−8cm 3gm −1sec −2.(6)This represents a factor of twelve increase over the pre-vious recommended uncertainty [20],and is primarily due to an anomalously high value for G determined by Michaelis,Haars,and Augustin [21].(See Table 1).2Reference6.67407(22)Quinn,et al.(2001)[30]6.674215(92)Luo et al.(1999)[32]6.6742(7)Schwarz et al.(1999)[34]6.6749(14)Kleinevoss et al.(1999)[36]6.673(10)CODATA(1986)[20]3[13]A.J.Heckler,Phys.Rev.D49,611(1994).[14]S.Dodelson and M.S.Turner,Phys.Rev.D46,3372(1992).[15]R.E.Lopez,M.S.Turner,and G.Gyuk,Phys.Rev.D56,3191(1997).[16]R.E.Lopez and M.S.Turner,Phys.Rev.D59,103502(1999).[17]S.Esposito,G.Mangano,G.Miele,and O.Pisanti,Nucl.Phys.B540,3(1999).[18]K.Hagiwara,et al.,Phys.Rev.D66,010001(2002).[19]P.J.Mohr and B.N.Taylor,Rev.Mod.Phys.72,351(2000).[20]E.R.Cohen and B.N.Taylor,Rev.Mod.Phys.59,1121(1987).[21]W.Michaelis,H.Haars,and R.Augustin,Metrologia32,267(1996).[22]R.H.Cyburt,astro-ph/0401091.[23]L.M.Krauss and P.Romanelli,Ap.J.358,47(1990).[24]L.M.Krauss and P.Kernan,Phys.Lett.B347,347(1995).[25]I.P.Lopes and J.Silk,astro-ph/0112310.[26]B.Ricci and F.L.Villante,Phys.Lett.B549,20(2002).[27]O.Zahn and M.Zaldarriaga,Phys.Rev.D67,063002(2003).[28]G.T.Gillies,Meas.Sci.Technol.10,421(1999).[29]St.Schlamminger,E.Holzschuh,and W.K¨u dig,Phys.Rev.Lett.89,161102(2002).[30]T.J.Quinn,C.C.Speake,S.J.Richman,R.S.Davis,andA.Picard,Phys.Rev.Lett.87,111101(2001).[31]J.H.Gundlach and S.M.Merkowitz,Phys.Rev.Lett.85,2869(2000).[32]Luo,J.,Hu,Z.K.,Fu X.H.,Fan S.H.,and Tang,M.X.,Phys.Rev.D59,042001(1999).[33]M.P.Fitzgerald and T.R.Armstrong,Meas.Sci.Technol10,439(1999).[34]J.P.Schwarz,D.S.Robertson,T.M.Niebauer,and J.E.Faller,Meas.Sci.Technol.10,478(1999).[35]F.Nolting,J.Schurr,S.Schlamminger,and W.K¨u ndig,Meas.Sci.Technol.10,487(1999).[36]U.Kleinevoss,H.Meyer,A.Schumacher,and S.Hart-mann,Meas.Sci.Technol.10,492(1999).。

Comparing Suzaku and XMM-Newton Observations of the Soft X-ray Background Evidence for Sola

a r X i v :0712.3538v 1 [a s t r o -p h ] 20 D e c 2007Draft version February 2,2008Preprint typeset using L A T E X style emulateapj v.10/09/06COMPARING SUZAKU AND XMM-NEWTON OBSERVATIONS OF THE SOFT X-RAY BACKGROUND:EVIDENCE FOR SOLAR WIND CHARGE EXCHANGE EMISSIONDavid B.Henley and Robin L.SheltonDepartment of Physics and Astronomy,University of Georgia,Athens,GA 30602Draft version February 2,2008ABSTRACTWe present an analysis of a pair of Suzaku spectra of the soft X-ray background (SXRB),obtained from pointings on and oﬀa nearby shadowing ﬁlament in the southern Galactic hemisphere.Because of the diﬀerent Galactic column densities in the two pointing directions,the observed emission from the Galactic halo has a diﬀerent shape in the two spectra.We make use of this diﬀerence when modeling the spectra to separate the absorbed halo emission from the unabsorbed foreground emission from the Local Bubble (LB).The temperatures and emission measures we obtain are signiﬁcantly diﬀerent from those determined from an earlier analysis of XMM-Newton spectra from the same pointing directions.We attribute this diﬀerence to the presence of previously unrecognized solar wind charge exchange (SWCX)contamination in the XMM-Newton spectra,possibly due to a localized enhancement in the solar wind moving across the line of sight.Contemporaneous solar wind data from ACE show nothing unusual during the course of the XMM-Newton observations.Our results therefore suggest that simply examining contemporaneous solar wind data might be inadequate for determining if a spectrum of the SXRB is contaminated by SWCX emission.If our Suzaku spectra are not badly contaminatedby SWCX emission,our best-ﬁtting LB model gives a temperature of log(T LB /K)=5.98+0.03−0.04and a pressure of p LB /k =13,100–16,100cm −3K.These values are lower than those obtained from other recent observations of the LB,suggesting the LB may not be isothermal and may not be in pressure equilibrium.Our halo modeling,meanwhile,suggests that neon may be enhanced relative to oxygen and iron,possibly because oxygen and iron are partly in dust.Subject headings:Galaxy:halo—Sun:solar wind—X-rays:diﬀuse background—X-rays:ISM1.INTRODUCTIONThe diﬀuse soft X-ray background (SXRB),which is observed in all directions in the ∼0.1–2keV band,is composed of emission from several diﬀerent components.For many years,the observed 1/4-keV emission was believed to originate from the Local Bubble (LB),a cavity in the local interstellar medium (ISM)of ∼100pc radius ﬁlled with ∼106K gas (Sanders et al.1977;Cox &Reynolds 1987;McCammon &Sanders 1990;Snowden et al.1990).However,the discovery of shadows in the 1/4-keV background with ROSAT showed that ∼50%of the 1/4keV emission originates from beyond the LB (Burrows &Mendenhall 1991;Snowden et al.1991).This more distant emission origi-nates from the Galactic halo,which contains hot gas with temperatures log(T halo /K)∼6.0–6.5(Snowden et al.1998;Kuntz &Snowden 2000;Smith et al.2007;Galeazzi et al.2007;Henley,Shelton,&Kuntz 2007).As the halo gas is hotter than the LB gas,it also emits at higher energies,up to ∼1keV.Above ∼1keV the X-ray background is extragalactic in origin,and is due to un-resolved active galactic nuclei (AGN;Mushotzky et al.2000).X-ray spectroscopy of the SXRB can,in principle,de-termine the thermal properties,ionization state,and chemical abundances of the hot gas in the Galaxy.These properties give clues to the origin of the hot gas,which is currently uncertain.However,to de-termine the physical properties of the hot Galactic gas,one must ﬁrst decompose the SXRB into its con-Electronic address:dbh@stituents.This is achieved using a technique called “shadowing”,which makes use of the above-mentioned shadows cast in the SXRB by cool clouds of gas be-tween the Earth and the halo.Low-spectral-resolution ROSAT observations of the SXRB were decomposed into their foreground and background components by modeling the intensity variation due to the varying absorption column density on and around shadow-ing clouds (Burrows &Mendenhall 1991;Snowden et al.1991,2000;Snowden,McCammon,&Verter 1993;Kuntz,Snowden,&Verter 1997).The same tech-nique was used to decompose ROSAT All-Sky Survey data over large areas of the sky (Snowden et al.1998;Kuntz &Snowden 2000).With higher resolution spectra,such as those from the CCD cameras onboard XMM-Newton or Suzaku ,it is possible to decompose the SXRB into its foreground and background components spectroscopically.This is achieved using one spectrum toward a shadowing cloud,and one toward a pointing to the side of the cloud.The spectral shape of the absorbed background component (and hence of the overall spectrum)will diﬀer between the two directions,because of the diﬀerent absorbing col-umn densities.Therefore,by ﬁtting a suitable multicom-ponent model simultaneously to the two spectra,one can separate out the foreground and background emis-sion components.Such a model will typically consist of an unabsorbed single-temperature (1T )thermal plasma model for the LB,an absorbed thermal plasma model for the Galactic halo,and an absorbed power-law for the ex-tragalactic background.The Galactic halo model could be a 1T model,a two-temperature (2T )model,or a dif-2HENLEY AND SHELTONferential emission measure (DEM)model (Galeazzi et al.2007;Henley et al.2007;S.J.Lei et al.,in preparation).Recent work has shown that there is an additional complication,as X-ray emission can originate within the solar system,via solar wind charge exchange (SWCX;Cox 1998;Cravens 2000).In this process,highly ion-ized species in the solar wind interact with neutral atoms within the solar system.An electron transfers from a neutral atom into an excited energy level of a solar wind ion,which then decays radiatively,emitting an X-ray photon.The neutral atoms may be in the outer reaches of the Earth’s atmosphere (giving rise to geo-coronal emission),or they may be in interstellar ma-terial ﬂowing through the solar system (giving rise to heliospheric emission).It has been estimated that the heliospheric emission may contribute up to ∼50%of the observed soft X-ray ﬂux (Cravens 2000).The geocoro-nal emission is typically an order of magnitude fainter,but during solar wind enhancements it can be of similar brightness to the heliospheric emission (Wargelin et al.2004).SWCX line emission has been observed with Chandra ,XMM-Newton ,and Suzaku (Wargelin et al.2004;Snowden,Collier,&Kuntz 2004;Fujimoto et al.2007).As the SWCX emission is time varying,it cannot easily be modeled out of a spectrum of the SXRB.If SWCX contamination is not taken into account,analyses of SXRB spectra will yield incorrect results for the LB and halo gas.This paper contains a demonstra-tion of this fact.Henley et al.(2007)analyzed a pair of XMM-Newton spectra of the SXRB using the pre-viously described shadowing technique.One spectrum was from a direction toward a nearby shadowing ﬁlament in the southern Galactic hemisphere (d =230±30pc;Penprase et al.1998),while the other was from a direc-tion ∼2◦away.The ﬁlament and the shadow it casts in the 1/4-keV background are shown in Figure 1.Contem-poraneous solar wind data from the Advanced Composi-tion Explorer (ACE )showed that the solar wind was steady during the XMM-Newton observations,without any ﬂares or spikes.The proton ﬂux was slightly lower than average,and the oxygen ion ratios were fairly typ-ical.These observations led Henley et al.(2007)to con-clude that their spectra were unlikely to be severely con-taminated by SWCX ing a 2T halo model,they obtained a LB temperature of log(T LB /K)=6.06and halo temperatures of log(T halo /K)=5.93and 6.43.The LB temperature and the hotter halo temperature are in good agreement with other recent measurements of the SXRB using XMM-Newton and Suzaku (Galeazzi et al.2007;Smith et al.2007),and with analysis of the ROSAT All-Sky Survey (Kuntz &Snowden 2000).We have obtained spectra of the SXRB from the same directions as Henley et al.’s (2007)XMM-Newton spectra with the X-ray Imaging Spectrometer (XIS;Koyama et al.2007)onboard the Suzaku X-ray obser-vatory (Mitsuda et al.2007).The XIS is an excellent tool for studying the SXRB,due to its low non-X-ray background and good spectral resolution.Our Suzaku pointing directions are shown in Figure 1.We analyze our Suzaku spectra using the same shadowing technique used by Henley et al.(2007).We ﬁnd that there is poor agreement between the results of our Suzaku analysis and the results of the XMM-Newton analysis in Henley et al.(2007).We attribute this discrepancy to previously un-Fig. 1.—The shadowing ﬁlament used for our observations,shown in Galactic coordinates.Grayscale :ROSAT All-Sky Sur-vey R1+R2intensity (Snowden et al.1997).Contours :IRAS 100-micron intensity (Schlegel et al.1998).Yellow squares :Our Suzaku pointing directions.recognized SWCX contamination in the XMM-Newton spectra,which means that SWCX contamination can oc-cur at times when the solar wind ﬂux measured by ACE is low and does not show ﬂares.This paper is organized as follows.The Suzaku obser-vations and data reduction are described in §2.The anal-ysis of the spectra using multicomponent spectral models is described in §3.The discrepancy between the Suzaku results and the XMM-Newton results is discussed in §4.This discrepancy is due to the presence of an additional emission component in the XMM-Newton spectra,which we also describe in §4.In §5we measure the total intensi-ties of the oxygen lines in our Suzaku and XMM-Newton spectra.We concentrate on these lines because they are the brightest in our spectra,and are a major component of the 3/4-keV SXRB (McCammon et al.2002).In §6we present a simple model for estimating the intensity of the oxygen lines due to SWCX,which we compare with our observations.We discuss our results in §7,and con-clude with a summary in §8.Throughout this paper we quote 1σerrors.2.OBSERVATIONS AND DATA REDUCTIONBoth of our observations were carried out in early 2006March.The details of the observations are shown in Ta-ble 1.In the following,we just analyze data from the back-illuminated XIS1chip,as it is more sensitive at lower energies than the three front-illuminated chips.Our data were initially processed at NASA Goddard Space Flight Center (GSFC)using processing version 1.2.2.3.We have carried out further processing and ﬁl-tering,using HEAsoft 1v6.1.2and CIAO 2v3.4.We ﬁrst combined the data taken in the 3×3and 5×5observa-tion modes.We then selected events with grades 0,2,3,4,and 6,and cleaned the data using the standard data selection criteria given in the Suzaku Data Reduc-tion Guide 3.We excluded the times that Suzaku passed through the South Atlantic Anomaly (SAA),and also times up to 436s after passage through the SAA.We also excluded times when Suzaku ’s line of sight was el-evated less than 10◦above the Earth’s limb and/or was1/lheasoft 2/ciao3/docs/suzaku/analysis/abc/abc.htmlOBSERVING CHARGE EXCHANGE WITH SUZAKU AND XMM-NEWTON3TABLE1Details of Our Suzaku ObservationsObservation l b Start time End time Usable exposureID(deg)(deg)(UT)(UT)(ks)Oﬀﬁlament501001010278.71−47.072006-03-0116:56:012006-03-0222:29:1455.6Onﬁlament501002010278.65−45.302006-03-0320:52:002006-03-0608:01:1969.0less than20◦from the bright-Earth terminator.Finally,we excluded times when the cut-oﬀrigidity(COR)wasless than8GV.This is a stricter criterion than that inthe Data Reduction Guide,which recommends exclud-ing times with COR<6GV.However,the higher CORthreshold helps reduce the particle background,and forobservations of the SXRB one desires as low a particlebackground as possible.The COR threshold that weuse has been used for other Suzaku observations of theSXRB(Fujimoto et al.2007;Smith et al.2007).Finally,we binned the2.5–8.5keV data into256-s time bins,andused the CIAO script analyzepublic4HENLEY AND SHELTON34:00.03:33:00.032:00.031:00.015:00.020:00.025:00.0-63:30:00.035:00.040:00.0Right ascensionD e c l i n a t i o nOn filament22:00.021:00.03:20:00.019:00.015:00.0-62:20:00.025:00.030:00.035:00.0Right ascensionD e c l i n a t i o nOff filamentFig.2.—Cleaned and smoothed Suzaku XIS1images in the 0.3–5keV band for our on-ﬁlament (left )and oﬀ-ﬁlament (right )observations.The data have been binned up by a factor of 4in the detector’s x and y directions,and then smoothed with a Gaussian whose standard deviation is equal to 1.5times the binned pixel size.The particle background has not been subtracted from the data.The red circles outline the regions that were excluded from the analysis (see text for details).in our ﬁt (Snowden et al.1997).The R1and R2count-rates help constrain the model al lower energies (below ∼0.3keV),while the higher channels overlap in energy with our Suzaku spectra.We extracted the ROSAT spec-tra from 0.5◦radius circles centered on our two Suzaku pointing directions using the HEASARC X-ray Back-ground Tool 8v2.3.The spectral analysis was carried out using XSPEC 9v11.3.2(Arnaud 1996).For the thermal plasma com-ponents,we used the Astrophysical Plasma Emission Code (APEC)v1.3.1(Smith et al.2001)for the Suzaku data and the ROSAT R4–7bands,and the Raymond-Smith code (Raymond &Smith 1977and updates)for the ROSAT R1–3bands.For a given model component (i.e.,the LB or one of the two halo components),the tem-perature and normalization of the ROSAT Raymond-Smith model are tied to those of the corresponding Suzaku APEC model.We chose to use the Raymond-Smith code for the lower-energy ROSAT channels be-cause APEC’s spectral calculations below 0.25keV are inaccurate,due to a lack of data on transitions from L-shell ions of Ne,Mg,Al,Si,S,Ar,and Ca 10.As the upper-limit of the ROSAT R1and R2bands is 0.284keV,and the R3band also includes such low-energy photons (Snowden et al.1997),APEC is not ideal for ﬁtting to these energy bands.For the absorption,we used the XSPEC phabs model,which uses cross-sections from Ba l uci´n ska-Church &McCammon (1992),with an updated He cross-section from Yan,Sadeghpour,&Dalgarno (1998).Following Henley et al.(2007),we used the interstellar chemical abundance table from Wilms,Allen,&McCray (2000).For many astrophysically abundant elements,these abundances are lower than those in the widely used solar abundance table of Anders &Grevesse (1989).However,recently several elements’solar photospheric abundances have been revised downwards (Asplund et al.2005),and are in good agreement with the Wilms et al.(2000)8/cgi-bin/Tools/xraybg/xraybg.pl9/docs/xanadu/xspec/xspec1110/atomdb/issuesOBSERVING CHARGE EXCHANGE WITH SUZAKU AND XMM-NEWTON5-4-2 0 2 40.3135channel energy (keV)(d a t a -m o d e l )/σ0.001 0.010.11c o u n t s s -1k e V-1On filamentLocal Bubble Halo (cold)Halo (hot)ExtragalacticInstrumental lines TotalO V I I O V I I IN e I XM g X I ?A l KS i KA u M -4-2 0 2 40.3135channel energy (keV)(d a t a -m o d e l )/σ0.0010.010.11c o u n t s s -1k e V-1Off filamentLocal Bubble Halo (cold)Halo (hot)ExtragalacticInstrumental lines TotalN V I I ?O V I I O V I I IN e I XA l KS i KA uMFig.3.—Our observed on-ﬁlament (left )and oﬀ-ﬁlament (right )Suzaku spectra,with the best-ﬁtting model obtained by ﬁtting jointly to the Suzaku and ROSAT data (Model 1in Table 7).The gap in the Si K instrumental line is where channels 500–504have been removed from the data (see §2).10100100010-6 c o u n t s s -1 a r c m i n-2-4-2 0 2 4R1R2R3R4R5R6R7ROSAT band(d a t a - m o d e l ) / σFig. 4.—The on-ﬁlament (dashed )and oﬀ-ﬁlament (solid )ROSAT All-Sky Survey spectra,compared with Model 1from Ta-ble 7.For clarity the individual model components have not been plotted.CALDB.This model component attenuated the emis-sion from the LB,halo,and extragalactic background for the Suzaku spectra only.We adjusted the model oxygen abundance to give C /O =6(Koyama et al.2007),and set the abundances of all other elements to zero.The results of this model are given as Model 2in Table 7.Figures 5and 6show this model com-pared with the Suzaku and ROSAT spectra,respec-tively.One can see from Figure 6that the ﬁt to the ROSAT data is greatly improved.The model implies a column density of carbon atoms,N C =(0.28±0.04)×1018cm −2,in addition to the amount of contamina-tion given by the CALDB contamination model,which is N C =3.1×1018cm −2at the center of the XIS1chip(from the CALDB ﬁle aecontami xrtxis08.html6HENLEY AND SHELTON-4-2 0 2 40.3135channel energy (keV)(d a t a -m o d e l )/σ0.0010.010.1c o u n t s s -1k e V-1On filamentLocal Bubble Halo (cold)Halo (hot)ExtragalacticInstrumental lines Total-4-2 0 2 40.3135channel energy (keV)(d a t a -m o d e l )/σ0.0010.010.1c o u n t s s -1k e V-1Off filamentLocal Bubble Halo (cold)Halo (hot)ExtragalacticInstrumental linesTotalFig. 5.—As Figure 3,but with a vphabs component included for the Suzaku spectra to model XIS contamination above that included in the CALDB (Model 2in Table 7;see §3.2for details).10 100100010-6 c o u n t s s -1 a r c m i n-2-4-2 0 2 4R1R2R3R4R5R6R7ROSAT band(d a t a - m o d e l ) / σFig.6.—As Figure 5,but for Model 2from Table 7.In Model 5we ﬁt exactly the same model to the Suzaku data alone.Without the ROSAT data,we cannot con-strain the LB temperature T LB .We therefore ﬁx it at the value determined in Model 2:T LB =105.98K.We also ﬁx N C for the vphabs contamination component at the Model 2value:N C =0.28×1018cm −2.The best-ﬁtting model parameters are in very good agree-ment with those obtained by ﬁtting jointly to the Suzaku and ROSAT spectra (compare Models 2and 5).We can only get consistent results between the Suzaku -ROSAT joint ﬁt and the ﬁt to just the Suzaku data by using a two-temperature model for the halo.However,note that the Model 5LB emission measure is consistent (within its errorbar)with zero.This is not to say that our data imply that there is no LB at all:as noted above,we need a LB component and two halo components to get a good joint ﬁt to the Suzaku and ROSAT data.Instead,the Model 5results imply that our Suzaku data are consis-tent with the LB not producing signiﬁcant emission in the Suzaku band (i.e.,E 0.3keV).Also shown in Table 7are the results of ﬁtting our model (without any LB component)to the on-and oﬀ-ﬁlament Suzaku spectra individually (Models 6and 7,respectively).As has already been noted,the normaliza-tion of the extragalactic background diﬀers signiﬁcantly between the two spectra.However,the plasma model pa-rameters for the individual spectra are in good agreement with each other.These results seem to justify allowing the extragalactic normalization to diﬀer between the two spectra while keeping all other model parameters equal for the two spectra.3.3.Chemical Abundances in the HaloWe investigated the chemical abundances of the X-ray-emissive halo gas by repeating the above-described mod-eling,but allowing the abundances of certain elements in the halo components to vary.In particular we wished to investigate whether or not varying the neon and magne-sium halo abundances improved the ﬁts to the Ne ix and Mg xi features noted above.We also allowed the abun-dance of iron to vary,as iron is an important contributor of halo line emission to the Suzaku band.For this investigation we just ﬁt to the Suzaku data,ﬁxing the LB temperature at log(T LB /K)=5.98,and ﬁxing the carbon column density of the vphabs contam-ination component at N C =0.28×1018cm −2.As we could not accurately determine the level of the contin-uum due to hydrogen,we could not measure absolute abundances.Instead,we estimated the abundances rel-ative to oxygen by holding the oxygen abundance at its Wilms et al.(2000)value,and allowing the abundances of neon,magnesium,and iron to vary.Both halo com-ponents were constrained to have the same abundances.The best-ﬁtting temperatures and emission measures of the various model components are presented as Model 8in Table 7,and the abundances are presented in Table 2.The best-ﬁtting model parameters are not signiﬁcantly aﬀected by allowing certain elements’abun-dances to vary (compare Model 8with Model 5).Iron does not seem to be enhanced or depleted relative to oxy-gen in the halo.Neon and magnesium both appear to be enhanced in the halo relative to oxygen,which is what one would expect from Figures 3and 5,as the modelsOBSERVING CHARGE EXCHANGE WITH SUZAKU AND XMM-NEWTON7 TABLE2Halo AbundancesElement AbundanceO1(ﬁxed)Ne a1.8±0.4Mg a4.6+3.5−2.8Fe1.2+0.4−0.5Note.—Abun-dances are relative tothe Wilms et al.(2000)interstellar abundances:Ne/O=0.178,Mg/O=0.051,Fe/O=0.055.a These enhanced abun-dances may be an arte-fact of SWCX contami-nation;see§7.2.shown in thoseﬁgures underpredict the neon and mag-nesium emission.We discuss these results in§§7.2and§7.5.In§7.2we discuss the possibility that the enhanced neon and mag-nesium emission is in fact due to SWCX contamination of these lines,rather than being due to these elements being enhanced in the halo.On the other hand,in§7.5 we discuss the implications of neon really being enhanced in the halo with respect to oxygen and iron.PARING THE SUZAKU AND XMM-NEWTONSPECTRAFor comparison,Table7also contains the results of the analysis of the XMM-Newton spectra from the same ob-servation directions by Henley et al.(2007).The Model9 results are taken directly from their“standard”model. However,it should be noted that Henley et al.(2007) used APEC to model all of their data,whereas in the analysis described above we used the Raymond-Smith code to model the ROSAT R1–3bands.We have therefore reanalyzed the XMM-Newton+ROSAT spec-tra,this time using the Raymond-Smith code to model the ROSAT R1–3bands,and using APEC to model the ROSAT R4–7bands and the XMM-Newton spec-tra.This new analysis allows a fairer comparison of our XMM-Newton results with our Suzaku results.The XMM-Newton spectra we analyzed are identical to those used by Henley et al.(2007)–see that paper for details of the data reduction.We added a broken power-law to the model to take into account soft-proton contamination in the XMM-Newton spectra.This broken power-law was not folded through XMM-Newton’s eﬀective area, and was allowed to diﬀer for the on-and oﬀ-ﬁlament datasets(see Henley et al.2007).The presence of this contamination means we cannot independently constrain the normalization of the extragalactic background.We therefore freeze the on-and oﬀ-ﬁlament normalizations at the Suzaku-determined values.The results of this new analysis are presented as Model10in Table7.As can be seen,there is poor agreement between the best-ﬁt parameters of the Suzaku +ROSAT model(Model2)and the XMM-Newton+ ROSAT model(Model10).We believe this discrepancy is due to an extra emission component in the XMM-Newton spectra.In Figure7we plot the diﬀerences between the XMM-Newton spectra and our best-ﬁtting0.10.20.30.40.5data-model(ctss-1keV-1)On filament MOS 1MOS 2 00.10.20.30.40.50.5125channel energy (keV)Off filament MOS 1MOS 2Fig.7.—The excesses in our on-ﬁlament(top)and oﬀ-ﬁlament (bottom)XMM-Newton spectra over our best-ﬁtting model to the Suzaku+ROSAT data(Table7,Model2).The gap in the data between1.4and1.9keV is where two bright instrumental lines have been removed.Suzaku+ROSAT model(Model2from Table7).To our best-ﬁtting Suzaku+ROSAT model we have added a broken power-law to model the soft-proton contami-nation in the XMM-Newton spectra.The parameters of this broken power-law are frozen at the values de-termined from theﬁtting to the XMM-Newton spectra described in the previous paragraph.The on-ﬁlament XMM-Newton spectra show excess line emission at∼0.57 and∼0.65keV,most likely due to O vii and O viii,re-spectively.The features in the oﬀ-ﬁlament spectra are not as clear.However,there appears to be excess O vii emission in the MOS1spectrum,and excess emission at ∼0.7keV(of uncertain origin)and∼0.9keV(proba-bly Ne ix)in the MOS2spectrum.We can estimate the signiﬁcance of the excess emission by calculatingχ2 for the XMM-Newton data compared with the Suzaku +ROSAT model.We concentrate on the excess oxy-gen emission and calculateχ2for the0.5–0.7keV energy range.Weﬁndχ2=106.28for24degrees of freedom for the on-ﬁlament spectra,andχ2=43.03for22degrees of freedom for the oﬀ-ﬁlament spectra.These correspond toχ2probabilities of2.5×10−12and0.0047,respectively, implying that the excesses are signiﬁcant in both sets of spectra at the1%level.We measure the intensities of the extra oxygen emis-sion byﬁttingδ-functions at E=0.570keV and 0.654keV to the excess spectra in Figure7.Weﬁt theseδ-functions simultaneously to the on-and oﬀ-ﬁlament XMM-Newton excess spectra.The intensities of the excess oxygen emission in the XMM-Newton spec-tra over the best-ﬁtting Suzaku+ROSAT model are 3.8±0.5L.U.(O vii)and1.4±0.3L.U.(O viii).We believe that this excess oxygen emission is due to SWCX contamination in our XMM-Newton spectra.As noted in the Introduction,this was not taken into ac-count in the original analysis of the XMM-Newton spec-tra.This is because the solar windﬂux was steady and slightly below average during the XMM-Newton obser-vations,leading Henley et al.(2007)to conclude that SWCX contamination was unlikely to be signiﬁcant.We discuss the SWCX contamination in our spectra further in§6.5.MEASURING THE OXYGEN LINES8HENLEY AND SHELTONAs well as using the above-described method to sep-arate the LB emission from the halo emission,we mea-sured the total intensities of the O vii complex and O viii line at∼0.57and∼0.65keV in each spectrum.These lines are a major component of the SXRB,accounting for the majority of the observed ROSAT R4diﬀuse back-ground that is not due to resolved extragalactic discrete sources(McCammon et al.2002),and are easily the most prominent lines in our Suzaku spectra.To measure the oxygen line intensities,we used a model consisting of an absorbed power-law,an absorbed APEC model whose oxygen abundance is set to zero,and two δ-functions to model the oxygen lines.As in the pre-vious section,the power-law models the extragalactic background,and its photon index was frozen at1.46 (Chen et al.1997).The APEC model,meanwhile,mod-els the line emission from elements other than oxygen, and the thermal continuum emission.The absorbing columns used were the same as those used in the ear-lier Suzaku analysis.As with our earlier analysis,we multiplied the whole model by a vphabs component to model the contamination on the optical blockingﬁlter which is in addition to that included in the CALDB con-tamination model(see§3.2).Weﬁx the carbon column density of this component at0.28×1018cm−2(Table7, Model2).Weﬁt this model simultaneously to our on-and oﬀ-ﬁlament spectra.However,all the model param-eters were independent for the two directions,except for the oxygen line energies–these were free parameters in theﬁt,but were constrained to be the same in the on-and oﬀ-ﬁlament spectra.We used essentially the same method to measure the oxygen line intensities in our XMM-Newton spectra.However,we did not use a vphabs contamination model,and,as before,we added a broken power-law to model the soft-proton contami-nation.Table3gives the energies and total observed intensities of the O vii and O viii emission measured from our Suzaku and XMM-Newton spectra.We can use the diﬀerence in the absorbing column for the on-and oﬀ-ﬁlament directions to decompose the ob-served line intensities into foreground(LB+SWCX)and background(halo)intensities.If I fg and I halo are the in-trinsic foreground and halo line intensities,respectively, then the observed on-ﬁlament intensity I on is given byI on=I fg+e−τon I halo,(1) whereτon is the on-ﬁlament optical depth at the energy of the line.There is a similar expression for the observed oﬀ-ﬁlament intensity I oﬀ,involving the oﬀ-ﬁlament op-tical depthτoﬀ.These expressions can be rearranged to giveI fg=eτon I on−eτoff I oﬀe−τon−e−τoff.(3) For the purposes of this decomposition,we use the Ba l uci´n ska-Church&McCammon(1992)cross-sections (with an updated He cross-section;Yan et al.1998)with the Wilms et al.(2000)interstellar abundances.We use the cross-sections at the measured energies of the lines. For the Suzaku measurements,the cross-sections we use are7.17×10−22cm2for O vii(E=0.564keV)and 4.66×10−22cm2for O viii(E=0.658keV).For the XMM-Newton O vii emission we use a cross-section of 7.03×10−22cm2(E=0.568keV).We cannot decom-pose the XMM-Newton O viii emission because the on-ﬁlament O viii line is brighter than the oﬀ-ﬁlament line. This gives rise to a negative halo intensity,which is un-physical.The results of this decomposition are presented in Ta-ble4.Note that the foreground oxygen intensities mea-sured from the Suzaku spectra are consistent with zero. This is consistent with our earlierﬁnding that the Suzaku spectra are consistent with there being no local emis-sion in the Suzaku band(see§3.2).The diﬀerence be-tween the foreground O vii intensities measured from our XMM-Newton and Suzaku spectra is5.1±3.1L.U.. This is consistent with the O vii intensity measured from the excess XMM-Newton emission over the best-ﬁtting Suzaku+ROSAT model(3.8±0.5L.U.;see§4).The halo O vii intensities measured from our XMM-Newton and Suzaku spectra are consistent with each other.This is as expected,as we would not expect the halo intensity to signiﬁcantly change in∼4years.6.MODELING THE SOLAR WIND CHARGE EXCHANGEEMISSIONIn§§4and5we presented evidence that our XMM-Newton spectra contain an extra emission component,in addition to the components needed to explain the Suzaku spectra.In particular,the O vii and O viii emission are enhanced in the XMM-Newton spectra.We attribute this extra component to SWCX emission,as it seems unlikely to be due to a change in the Local Bubble or halo emission.This extra component helps explain why our XMM-Newton and Suzaku analyses give such diﬀerent results in Table7.Previous observations of SWCX have found that in-creases in the SWCX emission are associated with en-hancements in the solar wind,as measured by ACE. These enhancements consist of an increase in the pro-tonﬂux,and may also include a shift in the ionization balance to higher ionization stages(Snowden et al.2004; Fujimoto et al.2007).In§6.1,we present a simple model for heliospheric and geocoronal SWCX emission,and use contemporaneous solar wind data from the ACE and WIND satellites to determine whether or not the ob-served enhancement of the oxygen lines in the XMM-Newton spectra is due to diﬀerences in the solar wind between our two sets of observations.In addition to the variability associated with solar wind enhancements,the heliospheric SWCX intensity is also expected to vary during the solar cycle,due to the dif-ferent states of the solar wind at solar maximum and solar minimum(Koutroumpa et al.2006).As our two sets of observations were taken∼4years apart,at diﬀer-ent points in the solar cycle,in§6.2we examine whether the SWCX intensity variation during the solar cycle can explain our observations.6.1.A Simple Model for Heliospheric and GeocoronalSWCX Emission6.1.1.The BasicsA SWCX line from a X+n ion of element X results from a charge exchange interaction between a X+(n+1) ion in the solar wind and a neutral atom.The intensity of that line therefore depends on the density of X+(n+1)。

小波随机耦合模型在胖头泡蓄滞洪区年降水量预测中的应用

律。
采用快速小波变换算法（ｒｕ算法）ＡＴｏｓ对水文时间序列进行小波分解，到某尺度下的小波变换序列；后得然
对各小波变换序列的主要成分（机成分或确定成分）随进
近年来，头泡蓄滞洪区采用科学的分洪调蓄来确胖保汛期大庆油田及哈尔滨市安全，此，究胖头泡蓄滞因研
［要］以胖头泡蓄滞洪区为例，实测年降水资料进行差分和标准化处理，用小波理论摘对采和随机水文学方法进行耦合分析，立了年降水小波随机耦合模型，度检验结果表明，型建精模
有效性和可靠性较高。该模型揭示了区域年降水量的时间变化规律，胖头泡蓄滞洪区充分为利用天然降水、理调蓄洪水及配置地下水资源提供了科学依据。合
第１８卷第２期
２１０２年２月
水利科技与经济
ＷａｅｏｓｒａｃｃｅｃｎｅｈｏｏｙａｄＥｏｏｔｒＣｎｅｖｎｙＳｉｎｅａｄＴｃｎｌｇｎｃｎｍｙ
Ｖｏ．８பைடு நூலகம்Ｎｏ２１１．Ｆｅｂ．，０１２２
展具有重要的意义。
法得到所研究水文时间序列的小波随机耦合模型。
３小波变换序列实例应用
为了充分利用天然降水、约地下水资源以及实现节地下水资源的可持续利用，文以胖头泡蓄滞洪区为例，本对胖头泡蓄滞洪区１５２０９８— ００年的年降水实测序列资料（１进行分析，图）根据上述建模理论，建立胖头泡蓄滞洪区年降水小波随机耦合模型。

The XMM-Newton view of radio-quiet and X-ray dim isolated neutron stars

a r X i v :a s t r o -p h /0401075v 1 7 J a n 2004Mem.S.A.It.Vol.,1cSAIt 2002MemoriedellaF.HaberlMax-Planck-Institut f¨u r extraterrestrische Physik,Giessenbachstraße,85748Garching,GermanyAbstract.As part of the guaranteed time,guest observer and calibration pro-grams,XMM-Newton extensively observed a group of six thermally emitting,isolated neutron stars which are neither connected with a supernova remnant nor show pulsed radio emission.The high statistical quality of the EPIC data allows a detailed and homogeneous analysis of their temporal and spectral properties.Four of the six sources are now well established as X-ray pulsars:The 11.37s period discovered in EPIC-pn data of RX J0806.4−4123was conﬁrmed in a second XMM-Newton observation.In the case of the X-ray faintest of the six stars,RX J0420.0−5022the period marginally indicated in ROSAT data was not seen in the EPIC data,instead a 3.45s pulse period was clearly detected.Spectral variations with pulse phase were discovered for the known 8.39s pul-sar RX J0720.4−3125and also RBS1223.For the latter EPIC data revealed a double-peaked pulse proﬁle for a neutron star spin period of 10.31s.The X-ray continuum spectra of all six objects are consistent with a Planckian energy distribution with black-body temperatures kT between 40eV and 100eV.EPIC data of the pulsars RBS1223and RX J0720.4−3125revealed a broad absorption feature in their spectra at energies of 100-300eV and ∼260eV,re-spectively.The depth of this feature varies with pulse phase and may be caused by cyclotron resonance scattering of protons or heavy ions in a strong magnetic ﬁeld.In such a picture the inferred ﬁeld strength exceeds 1013Gauss,in the case of RX J0720.4−3125consistent with the value estimated from its pulse pe-riod derivative.A similar absorption feature in the RGS and EPIC spectra of RX J1605.3+3249was reported recently.Key words.X-rays:stars –stars:neutron –stars:magnetic ﬁelds1.IntroductionPresently more than half a dozen ROSAT-discovered X-ray dim isolated neutron stars (XDINs,for recent reviews see Treves et al.2 F.Haberl:Radio-quiet and X-ray dim isolated neutronstarsFig.1.EPIC-pn light curves folded on the pulse period for the four pulsars among the XDINs.remnants.Some of them exhibit pulsationsin their X-rayﬂux indicating the neutronstar rotation period.Although there is littledoubt that the soft X-rays are of thermalorigin from the surface of an isolated neu-tron star,the details for the formation ofthe spectrum are not clear.XMM-Newtonobserved six XDINs as part of the guaran-teed time,guest observer and calibrationprograms.Here I summarize some of theﬁrst results of a homogeneous analysis oftheir temporal and spectral properties.2.X-ray pulsationsThe second brightest of the known XDINsis RX J0720.4−3125and was theﬁrstdiscovered as X-ray pulsar(Haberl et al.1997)with a period of8.39s.XMM-Newton observed RX J0720.4−3125sixtimes.As example the folded EPIC-pnlight curve from satellite revolution534is drawn in Fig.1which shows a pulsedfraction of about11%.In Chandra dataof RBS1223=1RXS J130848.6+212708Hambaryan et al.(2002)discovered pulsa-tions with a period of5.16s and XMM-Newton observations revealed that the trueneutron star spin period is more likely10.31s.This is supported by pulse phase de-pendent hardness ratio variations whichare diﬀerent for the two intensity max-ima(Haberl et al.2003).RBS1223ex-hibits the deepest modulation of the knownXDINs in its double peaked pulse proﬁleof18%(Fig.1).Theﬁrst XMM-Newtonobservation of RX J0806.4−4123revealeda6%modulation(Fig.1)with a periodof11.37s(Haberl&Zavlin2002)whichwas conﬁrmed in a second observation(Haberl et al.2004a).Four XMM-Newtonobservations of RX J0420.0−5022did notconﬁrm the22.7s pulsations originally in-dicated in ROSAT data,but clearly re-F.Haberl:Radio-quiet and X-ray dim isolated neutron stars3veal a3.45s period.The pulsed fraction is about12%(Fig.1).In Table1the de-rived pulse periods for the four pulsars are summarized together with pulse period derivatives assuming linear period changes between multiple XMM-Newton observa-tions.In most cases the time base line is too short to determine precise˙P values, only for RX J0720.4−3125observations by diﬀerent satellites cover already more than 10years(Zane et al.2002;Kaplan et al. 2002).3.X-ray spectraThe X-ray spectra of XDINs obtained by the ROSAT PSPC were all consistent with black-body emission little attenuated by interstellar absorption suggesting that the objects are close-by.To look for ab-sorption features which may be created by heavy chemical elements in the stel-lar atmosphere high resolution spectra of RX J1856.4−3754were obtained by the LETGS on Chandra(Burwitz et al.2001, 2003).Surprisingly,no signiﬁcant narrow features were detected.A spectral analysis(in a homogenous way using the latest calibration data)of the EPIC-pn spectra,which are of unprece-dented statistical quality,shows that in sev-eral cases a black-body model yields un-satisfactoryﬁts.The strongest deviations are seen from RBS1223and Haberl et al. (2003)demonstrate that a non-magnetic atmosphere models can neither explain the observed spectrum.However,it was found that adding an absorption feature mod-eled by a broad(100eV)Gaussian line at an energy between100and300eV to the Planckian continuum yields accept-ableﬁts.Similarly,but at a higher en-ergy of450eV and therefore inside the sensitive band of the RGS instruments van Kerkwijk(2004)presented the detec-tion of a broad absorption feature in the spectra of RX J1605.3+3249.Haberl et al. (2004b)report a broad absorption fea-ture in the EPIC-pn spectra of the pul-sar RX J0720.4−3125at an energy of270eV andﬁnd that the depth of the feature varies with pulse phase by a factor of∼2. Finally,also spectra of RX J0420.0−5022 indicate a possible absorption line at330 eV(Haberl et al.2004a).In Table1the spectral parameters in-ferred from theﬁts using the two mod-els(absorbed black-body and absorbed black-body with Gaussian-shaped absorp-tion line)are listed.Theﬁrst value given for column density N H and black-body tem-perature kT refers to the model without ab-sorption line and the second to the model with line added.4.DiscussionFour of the six X-ray-dim isolated neu-tron stars are now known as X-ray pul-sars with spin periods between3.45s and 11.37s.The fraction of pulsedﬂux in their folded X-ray light curves ranges between 6%and18%.RBS1223,RX J0720.4−3125 and RX J0420.0−5022show hardness ratio variations with pulse phase(Haberl et al. 2003,2004b,a)while for RX J0806.4−4123 the shallow modulation makes the signiﬁ-cant detection of such an eﬀect more diﬃ-cult(Haberl et al.2004a).Pulse phase re-solved spectra for theﬁrst three pulsars show that the temperature changes only marginally with pulse phase.Any model for the pulsed emission from this group of iso-lated neutron stars must be able to explain this behaviour.An important piece of information comes from the detection of broad ab-sorption features in the X-ray spectra of several XDINs.At least in the case of RX J0720.4−3125the depth of the feature varies strongly with pulse phase.A likely interpretation of these features is cyclotron resonance absorption which can be ex-pected in spectra from magnetized neutron stars withﬁeld strength B in the range of 1010–1011G or2×1013–2×1014G if caused by electrons or protons,respectively.In the case of RX J0720.4−3125the measured˙P, if interpreted as magnetic dipole braking, rules out the lower range for B,leaving pro-4 F.Haberl:Radio-quiet and X-ray dim isolated neutron starsTable1.X-ray-dim isolated neutron stars observed by XMM-NewtonRX J0420.0−5022 3.453<9×10−12 1.0/2.045/45330?6? RX J0720.4−31258.391(3−6)×10−14 1.4/0.885/842705 RX J0806.4−412311.371<2×10−120.496−RBS122310.313<6×10−127.1/4.195/86100-3002-6 RX J1605.3+3249−−0.3/0.996/934509 RX J1856.5−3754−−0.960−1?F.Haberl:Radio-quiet and X-ray dim isolated neutron stars5 2002,MNRAS,334,345。

牛顿-拉夫逊潮流计算中检测雅可比矩阵奇异性和网络孤岛的新方法

由（式可得：Ｉ【０由于Ｄ是对角矩３）＝阵，，因此至少有一对角元素为０。因为Ｕ＝ＵＬＤＤ，ＶＬ设该潮流计算是ｎ节点系统。所以（）２）２或（工ａｂ弋有一个成立，Ｕ中有一Ｈ子矩阵奇异，那么Ｈ矩阵各个列向量线性相即ｎ一１零行或中有一零列。ｕ中行为零，是行相关隋况；丰中列为关，：这Ｌ即－＝（不全为０ｑ０）零，这是列相关隋况。其中：是Ｈ矩阵的列向量，１是相关系ｃＴＡ矩阵奇异，那么Ａ矩阵行向量、向量线列数。由潮流雅可比矩阵元素计算可知：性相关，即：对同一节点，素和Ｊ素的计算具有完Ｈ元元全相似的表达式，因此，矩阵的各个列向量也Ｊ（ａ４）应满足（，即：
中国新技术新产品
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ＣｉａＮｗＴｃｎｌｇｅｎｒｄｃｓｈｎｅｅｈｏｏｉｓａｄＰｏｕｔ
高新技术
新型停水自动关闭阀结构、点及操作要点特
张金龙曹艳
（西安航空技术高等专科学校机械工程系，陕西西安７０７）１０７
中图分类号：４．文献标识码：Ｇ６４５Ａ
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Ｉ言。在日常生活中，前由于停水时忘记关闭阀门，水时也没能及时关闭阀门，来造成水资源浪费甚至形成安全隐患的情况屡见不鲜。着全民节水概念不断深入人心，一问随这题引起各方关注。因此急需设计一款可以在停水时自动关闭的水阀，它能够在停水后即使人们忘记关闭水龙头也能实现自动关闭，而再次来水时不至于出现水患的情况，能够有效的节约水资源。要实现自动关闭功能首先要有动力，这方面可以借助磁性元件的磁力、弹性元件的弹力、力等外力，时考虑供水和停水时的重同水压变化，通过联动机构实现。２停水自动关闭阀的结构及特点。利用水压、力等力学特性，过一系列的实验、重经改进，发出一种简单、行的带有停水自锁研可机构的水阀。款水阀为纯机械构造，阀体这以为主体框架，有阀芯、封圈、心轮以及配密偏手柄，无弹性元件，作状况不受环境和时间工的限制，构简单，价低廉并方便拆换，结造整体可靠性高。停水自动关闭阀结构原理如图１示，所实物如图２所示。序号ｌ水阀的偏心轮，为２为０型密封圈，为Ｖ型密封圈，阀体，３４为５为阀芯，销轴，手柄。阀体４是主框６为７为架，来装配其它元件，进水口和出水口；用有阀芯５的顶端与末端分别装有Ｖ型密封圈３和０型密封圈２ｖ型密封圈３利用其锥面，与阀体４内部锥面配合实现停水时密封，而０型密封圈２与阀体４内壁的接触实现来水时对水阀末端的密封，在阀芯５的中部开两

A New Approach for Filtering Nonlinear Systems

computational overhead as the number of calculations demanded for the generation of the Jacobian and the predictions of state estimate and covariance are large. In this paper we describe a new approach to generalising the Kalman ﬁlter to systems with nonlinear state transition and observation models. In Section 2 we describe the basic ﬁltering problem and the notation used in this paper. In Section 3 we describe the new ﬁlter. The fourth section presents a summary of the theoretical analysis of the performance of the new ﬁlter against that of the EKF. In Section 5 we demonstrate the new ﬁlter in a highly nonlinear application and we conclude with a discussion of the implications of this new ﬁlter1
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Merging clusters of galaxies observed with XMM-Newton

a r X i v :a s t r o -p h /0501377v 1 18 J a n 2005Merging clusters of galaxies observed withXMM-NewtonE.Belsole a J-L.Sauvageot b G.W.Pratt c and H.Bourdin da H.H.Wills Physics Laboratory -University of Bristol,Tyndall Avenue,Bristol BS81TL,UKb Service d’Astrophysique,CE-Saclay,L’orme des Merisiers,91191Gif sur Yvette Cedex,Francec MPE Garching,Giessenbachstraße,85748Garching,Germanyd Dipartimentodi Fisica,Universit`a degli studi di Roma Tor Vergata,Via della Ricerca Scientiﬁca 1,00133Roma,Italy1IntroductionAs the largest assembled structures in the Universe,clusters of galaxies are commonly thought to form by gradual accretion of matter alongﬁlaments and by interaction and merging with previously formed structures.Hydrody-namical simulations(e.g.Rowley et al.2004and references therein)predict that merger events strongly aﬀect the physical characteristics of the intra-cluster medium(ICM).In particular the temperature structure is thought to be an excellent indicator of the cluster dynamical state and formation his-tory.Spectro-imaging observations with XMM-Newton and Chandra allow the building of precise temperature maps,enabling deeper investigation of the dynamical processes of cluster formation and the eﬀect of the mergers on the ICM(e.g.,Markevitch et al.,2000;Neumann et al.,2003;Henry et al.,2004; Krivonos et al.,2003;Vikhlinin&Markevitch,2003).With the aim of describing an evolutionary sequence of cluster formation,we have selected a small sample of galaxy clusters showing morphological evidence of ongoing merger activity.The sample was selected,on the basis of previous X-ray observations,from nearby clusters which entered theﬁeld of view of XMM-Newton.Here we summarise results for A1750and A3921,presented in detail in Belsole et al.(2004,2005),and we describe preliminary,new results for A2065.2Observations and data analysisIn Table1we list the main physical characteristics of the three clusters,to-gether with basic observation information.The A1750and A3921observations were very little contaminated by soft protonﬂares(details of the data prepa-ration can be found in Belsole et al.2004,2005).Unfortunately,emission from soft protons dominates the whole observation of A2065.This required an ad-hoc treatment for these data,which allowed us to model the background. A2065will be re-observed with XMM-Newton,and thus here we discuss only preliminary results.The background estimates were obtained using a blank-sky observation con-sisting of several high-latitude pointings with sources removed(Lumb et al. (2002)),and source and background events were corrected for vignetting us-ing the eviweight task in the Science Analysis System(SAS),enabling us to use the on-axis response matrices and eﬀective area.Table1Journal of observations.z0.0860.0720.096RA(J2000)13h30m52s15h22m42.6s22h49m38.6sDec(J2000)−01o50′27′′+27o43′′21′′−64o23′15′′Obs time(ks)302330N H(1020cm−2)a 2.39 2.95 2.94Global T(keV) 3.87(2.84)b 5.4 5.0(a)(b)(c)Fig.1.(a)XMM-Newton EPIC0.3-7.0keV energy band count image of A1750;(b)MOS1+MOS20.1-1.4keV energy band count image of A2065,the band chosen to enhance cluster emission above the strong particle background;(c) XMM-Newton EPIC0.3-10keV energy band count image of A3921.These are raw, non-background subtracted images.to A1750were taken into account simultaneously.We found that A1750does not show signiﬁcant residuals above aβ-model,in the region between the two clusters,but there is some excess emission in their cores.On the other hand,A3921shows large residuals to the west(other than those(a)(b)Fig.2.Surface brightness maps of A1750(a)and A3921(b)in the soft energy band (0.3-2.0keV).Contours are the residuals above a2Dβ-model which was subtracted from the image.Theﬁrst contour is at1σ.in the centre of the main cluster),indicating that a signiﬁcant substructure is present and it is related to one or both the brightest galaxies in that area.The two galaxies are at7arcmin(RA=22h48m49s,Dec=−64◦23′10′′(J2000))to the north-west(BG2)and at8arcmin(RA=22h49m04s,Dec=−64◦20′35′′(J2000))to the WNW(BG3)from the central brightest galaxy BG1(RA= 22h49m58s;Dec=−64◦25′46′′(J2000);see Belsole et al.2005for details).3.2Temperature distributionWe computed temperature maps for A1750and A3921by applying the multi-scale spectro-imagery algorithm described in(Bourdin et al.,2004).EMOS cameras only were used for this analysis.For A2065,we obtained an hardness ratio(HR)map once the particle contamination was modelled and subtracted from the images.This gives us qualitative,but signiﬁcant results about tem-perature substructure in this cluster.The temperature maps are shown in Figure3.All three clusters show signiﬁcant temperature variations,even in the cases where surface brightness substructures were not detected(A1750).As is con-ﬁrmed by extraction of spectra from discrete regions(Belsole et al.,2004), the region between A1750N and A1750C has a temperature which is signif-icantly(30%)hotter than the global temperature of either the two clusters. Additional temperature gradients are observed in A1750C,indicating that this(a)(b)(c)Fig.3.Temperature maps.The wavelet algorithm described in Bourdin et al.(2004) was used for A1750(a)and A3921(c).In the case of A2065(b)the image is an hardness ratio map(see text for details).cluster was already perturbed in the past.The temperature enhancement,coincident with the isophotal compression, observed in the A2065HR map points to a bow shock.We also detect a cool core,coincident with the peak of X-ray emission.The orientation of the striking hot temperature bar in A3921represents our strongest proof against the interpretation that this is a merger before close core passage.The temperature here varies between7and8keV,up to60% higher than the main cluster temperature.4DiscussionFor each cluster we summarise the results obtained in the previous sections.A1750(1)From the morphological analysis we found:oﬀ-centre cores and twist ofthe isophotes,but lack of substructure in the region between the two clusters.(2)the temperature increases weakly(∼30%),but signiﬁcantly,in the regionbetween the two clusters(3)strong temperature variations are observed within the main cluster(A1750C)and we also measured a discontinuity in the gas density proﬁle of order 20%.(4)we found a high entropy in the core of the two clusters(see Belsole et al.2004)The combination of these results lead us to interpret A1750as an ongoing merger between two clusters of similar masses,which have just started to in-teract at a real distance comparable to their virial radii.These two units will be in the compact phase(core passage)within1Gyr.However the temperature and density variations within A1750C itself are not explicable by the merger event occurring with A1750N and are intrinsic to this cluster.The most likely interpretation is that this is the signature of(a)previous merger(s).A1750is a good observational test case to be compared with numerical simulations, since it shows all of the signatures expected from gravitationally dominated processes.However,the fact that eﬀects of a previous merger are observed strongly supports the necessity of taking into account time dependent quan-tities,such us the relaxation time,in using galaxy clusters for cosmological purposes.A2065The surface brightness shows an isophotal compression towards the south-east,at∼80arcsec from the X-ray peak.The feature is accompanied by a forward shock in the same axis(NW-SE);moreover a surviving cooling coreis detected.Despite the limited quality of the data,A2065shows clear signatures of be-ing an ongoing merger in the compact phase,when the detection of strong shocks is the most favourable.This is similar to what is observed in numer-ical simulations of head-on collisions of merging clusters.The fact that thecore of the main cluster is cool suggests that this is probably the remnantof a cooling core,and thus the colliding object was probably of smaller mass (e.g.G´o mez et al.,2002).The new XMM-Newton observations of this object should allow us to put better constraint on these preliminary results.A3921Observational merger evidence includes:(1)Two peaks in both the X-ray emission and the galaxy distribution(Ferrari et al.,2005);(2)The hot bar is oriented parallel to the line joining the subclusters,it isnot orthogonal,as in the case of A1750;(3)The central regions of the main cluster and the subcluster to the westare strongly perturbed;(4)There is an oﬀ-set between the galaxy distribution of the smaller sub-cluster and the secondary X-ray peak(Belsole et al.,2005;Ferrari et al.,2005).This evidence cannot be interpreted as the result of a pre-merger.We are seeing maybe the best example of an X-ray observed oﬀ-axis post-merger.The subcluster has come from somewhere in the SE and is currently exiting towards the NW.The two merging units have diﬀerent masses,on a ratio of1to3(or1to5;see also Ferrari et al.2005).Comparison of these high qualityX-ray results with optical observations and numerical simulations yield an estimate of the age of the merger of order0.5Gyr after core passage.Oﬀ-axis mergers are more likely to occur than head-on ones,and they are more eﬃcientin mixing the gas via turbulence.If anything,A3921needs even deeper study,and the combination of these XMM-Newton data with upcoming Chandra observations will give further elements to our interpretation.5ConclusionsThe XMM-Newton observations of this small sample of galaxy clusters has conﬁrmed that the comparison of X-ray morphology and temperature is an excellent tool to understand the dynamical status of these objects.In the case of A1750and A3921,spectroscopy of discrete regions((Belsole et al., 2004,2005)has conﬁrmed the signiﬁcance of the temperature structure found with the multi-scale wavelet approach.The signiﬁcance of the temperature structure in A2065will be investigated with the upcoming XMM-Newton ob-servation.For the better studied cases we have conﬁrmed the previous inter-pretation of a recent merger(A1750),but have added new evidence suggesting that at least one of the subclusters is itself a merger remnant.Good quality X-ray data have allowed us to completely revolutionise the interpretation of the dynamical state of A3921.We can organise these clusters along an evolutionary path,where A1750rep-resents the beginning of a merging event,which in a timescale of order1.5 Gyr will be in the same state as A2065,when a bow shock is departing in the direction of motion after the two cores have collided,and the two(or maybe more)colliding objects are not physically separable anymore.Finally,A3921 represents the epoch when the secondary object has already passed the close core passage phase,it is exiting on the far side with respect to the direction of motion,and it will be accreted by the main cluster on a larger timescale (of order3-5Gyr).From so small a sample we cannot extract global conclusions on the popu-lation of merging galaxy clusters.However,this work supports the necessity of a wider investigation of the eﬀect of the physics of mergers on the global characteristics of galaxy clusters,especially if these objects are to be used to derive cosmological parameters.ReferencesBeers,T.C.,Gebhardt,K.,Forman,W.,Huchra,J.P.,Jones,C.,1991,AJ, 102,1581-1609,A dynamical analysis of twelve clusters of galaxies Belsole,E.,Pratt,G.W.,Sauvageot,J-L.,Bourdin,H.,2004,A&A,415,821-838,An XMM-Newton observation of the dynamically active binary cluster A1750Belsole,E.,Sauvageot,J-L.,Pratt,G.W.,Bourdin,H.,2005,A&A,in press, preprint astro-ph/0409544,An XMM-Newton observation of A3921:an oﬀ-axis mergerBourdin,H.,Sauvageot,J.-L.,Slezak,E.,Bijaoui,A.,Teyssier,R.,2004,A&A, 414,429-443,Temperature map computation for X-ray clusters of galaxiesCavaliere,A.,&Fusco-Femiano,R.,1976,A&A,49,137-144,X-rays from hot plasma in clusters of galaxiesDickey,J.M.,&Lockman F.J.,1990,ARA&A,28,215-261,HI in the Galaxy Ferrari,C.,Benoist,C.,Maurogordato,S.,Cappi,A.,Slezak,E.,2005,A&A, accepted,preprint:astro-ph/0409072,Dynamical state and star formation properties of the merging galaxy cluster Abell3921G´o mez,P.L.,Loken,C.,Roettiger,K.,Burns,J.O.,2002,ApJ,569,122-133, Do Cooling Flows Survive Cluster Mergers?Henry,J.P.,Finoguenov,A.,Briel,U.,2004,ApJ,615,181-195,Wideﬁeld X-ray temperature,pressure and entropy maps of A754Krivonos,R.A.,Vikhlinin,A.A.,Markevitch,M.L.,Pavlinsky,M.N.,2003, AstL,29,425-428,A Possible Shock Wave in the Intergalactic Medium of the Cluster of Galaxies A754Lumb,D.H.,Warwick,R.S.,Page,M.,De Luca,A.,2002,A&A,389,93-105, X-ray background measurements with XMM-Newton EPICMarkevitch et al.,2000,ApJ,541,542-549,Chandra Observation of Abell 2142:Survival of Dense Subcluster Cores in a MergerNeumann,D.M.,Lumb,D.H.,Pratt,G.W.,Briel,U.,2003,A&A,400,811-821,The dynamical state of the Coma cluster sith XMM-Newton Rowley,D.R.,Thomas,P.A.,Kay,S.T.,2004,MNRAS,352,508-522,The merger history of clusters and its eﬀect on the X-ray properties of the intr-acluster medium,Vikhlinin,A.A.,Markevitch,M.L.,2003,AstL,28,495-508,A Cold Front in the Galaxy Cluster A3667:Hydrodynamics,Heat Conduction and Magnetic Field in the Intergalactic Medium。

窄线赛弗特I型星系中可能具有吸积盘热辐射起源的软X射线超

窄线赛弗特I型星系中可能具有吸积盘热辐射起源的软X射线超李晔【摘要】理论上,低质量高吸积率活动星系核的标准吸积盘黑体热辐射有可能形成软X射线波段的超出.然而,活动星系核的软X射线超温度为0.1 keV左右,显著高于标准吸积盘理论预言的最高有效温度.只有Yuan等人在2010年报道的RXJ1633+4718是一个例外,其软超温度为32.5±-8.06.0eV,显著小于0.1 keV,并与吸积盘理论预言的温度相符；此外,其光度也符合吸积盘的理论预期.因此该软X射线超很可能起源于吸积盘的热辐射.这一类源对于吸积盘理论和软X射线超的研究都有重要意义.文中使用ROSAT PSPC数据,在所有已知的窄线赛弗特I型星系(Narrow Line Seyfert I galaxies,NLSIs)中寻找类似于RXJ1633+4718的源,即软X射线超可能起源于吸积盘热辐射的源.分析了150个源的245条光谱,其中58个源的90条光谱具有显著的软X射线超.样本中软X射线超温度分布的平均值-Tsoft为0.10 keV,标准偏差为0.03 keV.除了RX J1633+4718外,只有3个源的软X射线超温度小于60 eV,而且温度接近吸积盘最高温度.这个结果表明,类似于RX J1633+4718的具有低温软X射线超的源很稀少.最后,在具有黑洞质量估计的26个源中,软超温度与黑洞质量MBH、爱丁顿比L/LEdd及预期吸积盘最高温度Tmax都没有明显的关联性,与前人的结果一致.%It is theoretically expected that the thermal radiation from accretion disks of Active Galactic Nuclei (AGNs) with low black hole mass would contribute to the soft X-ray band and result in an excess emission. However, the temperatures of the observed soft X-ray excess of AGNs are typically around 0.1 keV, significantly higher than those predicted by the standard disk model. There is only oneexception found so far, R.X J1633+4718, which has a significantly low soft excess temperature of 32.5l+8.0-6.0 eV, consistent with the maximum temperature as well as the luminosity of the predicted disk emission(Yuan et al. 2010).rnIn this paper, we search for RX J1633 like AGNs, whose soft X-ray excess temperature is close to the maximum temperature of accretion disk, in all known Narrow Line Seyfert I galaxies (NLSIs) observed with ROSAT PSPC in the archive. We analyzed the PSPC spectra of 150 NLSIs (245 observations) in total, 58 (90 observations) of which show significantly soft X-ray excess emission. In addition to RX J1633+4718, only 3 objects (4 observations) show soft X-ray excess temperatures less than 60 eV and close to the theoretical prediction of the disk emission. They form a sample of candidates for future follow-up studies. Our result indicates that RX J1633+4718 like objects are very rare. The correlations between the temperature of the soft X-ray excess and black hole mass as well as the Eddington ratio are also investigated, and no correlation is found. This confirms the previous results, and implies that the soft X-ray excess of most AGNs should originate from other mechanisms rather than the thermal emission of the accretion disk.【期刊名称】《天文学进展》【年(卷),期】2013(031)001【总页数】14页(P110-123)【关键词】活动星系核;吸积盘X射线热辐射;软X射线超【作者】李晔【作者单位】中国科学院国家天文台/云南天文台,昆明650011;中国科学院大学,北京100049;中国科学院国家天文台,北京100012【正文语种】中文【中图分类】P157.6活动星系核中心存在超大质量黑洞，物质落入中心黑洞的过程中形成吸积流，并产生辐射[1-3]。

活动星系核X射线本征谱指数与爱丁顿比关系的研究进展

活动星系核X射线本征谱指数与爱丁顿比关系的研究进展倪嘉阳;薛永泉【摘要】活动星系核是中央核区有剧烈活动的(河外)星系总称.随着观测技术不断进步,人们对活动星系核的研究越来越多,对其理解也越来越深刻.总结整理了近年来对活动星系核X射线本征谱指数与爱丁顿比关系的观测结果,揭示出如下V形关系图像:随着爱丁顿比由大变小,X射线本征谱指数与爱丁顿比由存在正相关关系,转变为存在负相关关系.一般认为,这一观测现象反映了随着吸积率的降低,黑洞吸积模式发生了变化,由高吸积率时的标准薄盘吸积变为低吸积率时的辐射无效吸积流.这表明,基于标准薄盘的最基本的活动星系核统一模型虽然能够成功地解释较高光度活动星系核的很多观测现象,但却需要做一定的修正,以解释低光度活动星系核的一些观测性质.同时,将来有希望利用这一相关关系估算活动星系核一些重要参数,如中央超大黑洞质量、吸积率等,从而帮助人们更好地理解活动星系核的辐射机制和演化过程.最后对这一领域的研究进行了总结与展望.%Active galactic nuclei (AGN) are galaxies that have strong activities at their centers. Due to continual progress in observational technologies, a wide variety ofresearches on AGN have been carried out, leading to profound understanding of the nature of AGN. This paper collects and summarizes recent observational results about the correlation between X-ray intrinsic photon index and Eddington ratio in AGN, which present a V-shape correlation:as the Eddington ratio decreases continuously, such a correlation changes from being positive into being negative. It is generally believed that these observational results reflect that, as the accretion rate decreases, the black hole accretion mode changes as well, from theoriginal standard thin disk into radiatively ine?cient accretion flow. This indicates that the very basic AGN unification models based on the standard thin accretion disk have to be modified in order to well explain some observed properties of the low-luminosity AGN, although those models enjoy great success in explaining many observations of the AGN with higher luminosities. In the future, it is possible to use this correlation (if refined further) to estimate some important AGN parameters such as the black hole mass and accretion rate, which will facilitate our better understanding of the radiation mechanisms and evolution of AGN. Finally, this paper is concluded with some future prospects in this research field.【期刊名称】《天文学进展》【年(卷),期】2017(035)004【总页数】19页(P398-416)【关键词】活动星系核;X射线天文学;吸积物理【作者】倪嘉阳;薛永泉【作者单位】中国科学技术大学天文学系,合肥 230026;中国科学院星系与宇宙学重点实验室,合肥 230026;中国科学技术大学天文学系,合肥 230026;中国科学院星系与宇宙学重点实验室,合肥 230026【正文语种】中文【中图分类】P157.6活动星系核(active galactic nucleus，简称AGN)是宇宙中光度最大的一类天体，其在整个电磁波段都有很强的辐射。

后牛顿力学近似形式__解释说明

后牛顿力学近似形式解释说明1. 引言1.1 概述牛顿力学作为经典力学的基石，已经发展了几个世纪。

然而，在一些极限情况下，牛顿力学的简化模型并不能提供准确的解释和预测。

为了克服这一局限性，科学家们开始研究并发展了后牛顿力学近似形式。

1.2 文章结构本文将对后牛顿力学近似形式进行详细解释和说明。

首先，我们将介绍后牛顿力学的定义和背景，包括它与传统牛顿力学之间的区别和联系。

接着我们将探讨后牛顿力学近似形式的基本原理，包括修正经典力学假设、非惯性参考系下运动定律的修正以及大质量物体引力场中运动方程的修正。

然后我们将重点探讨后牛顿力学在科学研究中的应用与实践，涉及轨道预测、宇航飞行计算、天体物理、相对论物理以及新型技术、工程与设计等领域。

最后，在结论部分我们将总结后牛顿力学近似形式对科学研究的重要性与意义，并对其未来发展进行展望。

1.3 目的本文的目的是为读者提供关于后牛顿力学近似形式的全面认识。

通过对该主题的详细解释和说明，我们希望读者能够理解后牛顿力学近似形式的定义、背景和基本原理，以及它在科学研究中的应用与实践。

同时，我们还将探讨后牛顿力学近似形式可能面临的挑战和未来发展方向，以促进读者对这一领域的思考和研究。

2. 后牛顿力学近似形式的定义和背景2.1 后牛顿力学的概念后牛顿力学是对经典牛顿力学的一种修正和扩展，用于描述当物体具有较高速度或在强引力场中运动时，经典力学不再适用的情况。

它是对牛顿定律进行修正，以更准确地描述这些特殊情况下的物体运动。

2.2 牛顿力学的局限性和需求尽管牛顿力学在描述大多数日常物理运动时非常准确有效，但在高速、低温等特殊条件下，以及在强引力场中如行星轨道等情况下，它显示出局限性。

此外，在精密科学研究和工程设计中，需要更精确的理论来预测和解释实验数据。

2.3 发展后牛顿力学的动机与背景发展后牛顿力学最重要的动机之一是相对论理论的提出。

相对论揭示了高速运动物体行为与经典牛顿力学预言之间存在的偏差，并推动了量子理论等其他领域的发展。

泰勒幂法则生态学意义

泰勒幂法则生态学意义泰勒幂法则是一个描述物种多样性分布的经验规律，它指出物种的数量与其个体的体积或重量之间存在着一个幂函数的关系。

这个规律在生态学中应用十分广泛，对于理解物种多样性的形成、物种生态学特征的预测以及生态系统的稳定性等都有重要意义。

1.物种多样性的形成：泰勒幂法则提供了解释物种多样性形成的一种机制。

根据这一规律，较大的物种数量较少，这可能是因为其较大的身体体积需要更多的资源来维持生存，而这些资源往往在一个生态系统中是有限的，因此较大物种的数量较少。

而较小的物种由于体积较小，对资源需求相对较少，可以占据更多的生态位，因此数量相对较多。

这一分布模式促进了物种间的共存和资源的合理利用。

2.物种生态学特征的预测：根据泰勒幂法则，我们可以通过测量物种的体积或重量来预测其数量。

这对于研究物种的数量动态变化、进行保护和管理工作以及评估生态系统的稳定性等都具有重要意义。

例如，当我们在一个生态系统中测量到其中一物种的体积或重量时，可以根据泰勒幂法则推测出其数量的范围，从而更好地了解该物种的种群状况和生态学特征。

3.生态系统的稳定性：泰勒幂法则对于生态系统的稳定性具有重要影响。

根据这一规律，生态系统中的大多数物种都是小型的，数量较多。

这种分布模式使得生态系统对外界的干扰具有一定的弹性，当一些物种受到干扰而减少时，其他物种可以填补空缺，保持生态系统的稳定性。

此外，物种的数量分布也影响着食物链和食物网的结构，在这些网络中，小型物种扮演着重要的角色，起到能量转化和传递的关键作用。

4.物种保护和管理：泰勒幂法则可以帮助我们更好地了解物种的数量和分布，从而更好地进行物种保护和管理工作。

通过对不同物种的体积或重量进行测量，我们可以推测出它们的数量范围，并进一步评估其濒危程度和潜在的威胁。

这为我们采取有效的保护措施和管理策略提供了重要的依据。

综上所述，泰勒幂法则在生态学中具有重要的意义，它帮助我们理解物种多样性的形成机制，预测物种的数量动态变化，了解生态系统的稳定性，并指导物种保护和管理工作。

基于电子束离子阱的天体X射线和极紫外辐射研究进展

基于电子束离子阱的天体X射线和极紫外辐射研究进展彭吉敏;仲佳勇;梁贵云;刘畅【摘要】观测光谱是研究天体的基础资料,对这些光谱的理解主要依靠理论模型.由于各模型依赖于众多的基本原子参数,且不同的模型对同一特定对象有不同的理解,所以对这些模型进行实验校准十分重要.电子束离子阱(electron beam ion trap,简称EBIT)能够产生与天体环境类似的等离子体环境,因此基于电子束离子阱的实验室光谱测量极大地促进了对天体X射线和极紫外辐射的研究.主要对以下内容进行介绍:卫星观测光谱和理论数值计算的现状及所面临的问题;基于电子束离子阱的类氖铁(Fe XVII)3C/3D重要诊断谱线比的最新研究进展;近年来实验室电子束离子阱对X射线和极紫外辐射的测量进展.最后,对现有的实验室光谱研究工作予以简要的展望.%Observed spectram is the basic data for celestial research. In recent years, with the enhancement of space, equipment, imaging technologies and simulation techniques, spec-trometers with larger effective area have provided abundant X-ray and extreme ultra-violet spectra with high resolution. These spectral data which will post deep insights on different ob jects, such as plasma heating, accretion of compact ob jects, energy storage and release, emission structure, feedback of supernova, as well as kinetics and dynamics in X-ray/EUV emitters, are mainly dissected by theoretical calculations. However, the models depend on many elementary atomic parameters and there are different understanding for the same ob ject between different models, it is necessary to calibrate these models by laboratory measurement. The electron beam ion trap which is an inexpensive compact device is an ideal facility for spectroscopicbenchmark due to its overlapping electron density and temperature with as-trophysical plasma in stellar corona, supernova remnants and so on. Therefore, the spectral measurement based on the electron beam ion trap greatly promotes the study of X-ray and extreme ultraviolet radiation. This article will focus on the following: current situation of spectra of satellite observations and theoretical calculation and the problems; the latest re-search progress of the important diagnostic line ratio(Fe XVII's 3C/3D) based on EBIT;recent advances in laboratory measurement of X-rays and extreme ultraviolet radiation based on electron beam ion trap. Finally, a brief prospect for the laboratory spectroscopy research will be given.【期刊名称】《天文学进展》【年(卷),期】2017(035)004【总页数】12页(P417-428)【关键词】电子束离子阱;X射线;极紫外辐射;原子数据;高分辨率【作者】彭吉敏;仲佳勇;梁贵云;刘畅【作者单位】北京师范大学天文系,北京 100875;中国科学院光学天文重点实验室国家天文台,北京 100012;北京师范大学天文系,北京 100875;中国科学院光学天文重点实验室国家天文台,北京 100012;北京师范大学天文系,北京 100875【正文语种】中文【中图分类】P141了解天体辐射与光谱信息依赖于天体辐射成像和光谱观测，光谱获得主要基于高分辨率光谱仪观测。

Newton.li物理学家用LMPN理论挑战美国费米研究所，发现宇宙“新物质粒子？

Newton.li物理学家用LMPN理论挑战美国费米研究所，发现宇宙“新物质粒子？Newton.li物理学家用LMPN理论挑战美国费米研究所，发现宇宙“新物质粒子？Newton.li theoretical physicist challenge the United States with LMPN Fermi Institute, found that the universe, "the new particles of matter?(Final Revised)（最终改进版）当美国费米研究所高能加速器研究团体的物理学家Giovanni Punzi,于2011-04-06，向世界宣布，它们用高能加速器的粒子碰撞技术，可能找到一个真正“偷走”万物质量和力的，不是“希格斯玻色子”的”新粒子”，而让人类世界能找到万物丢失力和质量的真正源头之后，全球各种媒体无不热烈响应和高调报道…..。

在此，newton.li用威力无比强大的LMPN理论发起对原子论下的电子，中子，中微子，夸克子，“希格斯玻色子”……其它子的，一个尺寸一种物质，一个尺寸一种理论的“尺寸科学“，进行全面挑战。

欢迎所有科学家以及Giovanni Punzi等物理学家们及所有的科学人进行批评，监督，打假，批判和反挑战（此文已送到美国费米研究所，Giovanni Punzi等物理学家，以及全世界更多的物理学家，其它科学家们的手里）。

Newton.li物理学家针对Fermi National Accelerator Laboratory（美国费米国立加速器研究所，Giovanni Punzi 物理学家，在美国Illinois州的费米研究所，用Tevatron Collider，对撞加速器，所进行的粒子对撞试验说：可能找到物质因夸克子破损，而丢失物质（万物）的质量和力的，不是“希格斯波色子”，而是另一个“重夸克子”，就此可能发现物质力和质量的新来源,也就是说,发现传统物理学家，在预测之外的“新粒子“，但它不是费米研究所原来所发现的，曽让全世界兴奋和轰动的，”偷走“万物力和质量的”神秘“的“希格斯波色子”。

哈密尔顿系统有限元的守恒性和辛性质的开题报告

哈密尔顿系统有限元的守恒性和辛性质的开题报告
Title: Conservation and Symplectic Properties of Hamiltonian Systems with Finite Elements
Introduction:
Hamiltonian systems are classical mechanical systems that describe the evolution of a physical system in a conservative manner. They are important in many areas of physics and engineering, including celestial mechanics, fluid dynamics, and quantum mechanics. In numerical simulation, Hamiltonian systems are typically solved using finite element methods due to the complexity of the systems being modeled. This project will explore the conservation and symplectic properties of Hamiltonian systems when solved using finite element methods.
4. A contribution to the field of numerical methods for Hamiltonian systems.
Conclusion:
In conclusion, this project will investigate the conservation and symplectic properties of Hamiltonian systems when solved using finite element methods. The development of numerical algorithms that preserve these properties will improve the accuracy and stability of numerical simulations of Hamiltonian systems. This project will contribute to the field of numerical methods for Hamiltonian systems and provide a better understanding of their behavior.

马同学泰勒公式

马同学泰勒公式
泰勒公式是描述流体力学中的应力分布的一个重要公式。

它由19世纪的英国物理学家泰勒提出，被广泛应用于流体力学领域的研究中。

泰勒公式可以用来描述在流体中的一个微小流动元素所受到的剪切应力。

剪切应力是指流体内部不同层之间因相对速度差异而产生的力。

在流体中，剪切应力的大小与速度梯度成正比，即速度梯度越大，剪切应力越大。

泰勒公式的数学表达形式如下：
τ = μ (∂u/∂y)
其中，τ表示剪切应力，μ表示流体的动力粘度，u表示流体的速度，y表示流体流动元素所处的位置。

通过泰勒公式，我们可以计算出流体在不同位置的剪切应力，从而了解流体在不同位置上的流动情况。

这对于研究流体的运动规律以及流体的力学性质具有重要意义。

泰勒公式的应用范围非常广泛。

在工程上，它可以用来研究液体在管道中的流动情况，优化管道的设计以提高流体输送效率。

在地球科学领域，它可以用来研究海洋和大气中的流动现象，预测天气变化和海洋环流。

在生物医学领域，它可以用来模拟血液在血管中的流动，研究心血管疾病的发生机制。

泰勒公式在流体力学领域的应用非常广泛，它为我们研究流体的运动规律以及流体的力学性质提供了一种有效的方法。

通过对流体剪切应力的计算，我们可以更加深入地了解流体的流动情况，为各个领域的应用提供有力的支持。

非牛顿重力可能存在全球性分布规律

非牛顿重力可能存在全球性分布规律
周平源
【期刊名称】《大自然探索》
【年(卷),期】1989(000)003
【摘要】如果假设存在南北两半球符号相反的弱“涡旋引力场”及排斥性汤川力与检测物体环境相关。

就可能揭示非牛顿重力存在全球性分布规律。

该设想可能逻辑一致地重新理解已证实的非牛顿重力效应,并提出“地下伽利略实验”以检验“第五种力”是否与材料性质有关,可能预言某些新实验结果并引导我们寻找一种与牛顿引力物质对称的新实体物质。

【总页数】7页(P83-89)
【作者】周平源
【作者单位】成都市科学技术协会《成都科技报》
【正文语种】中文
【中图分类】N49
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