Observation of strong-coupling effects in a diluted magnetic semiconductor (Ga,Fe)N

合集下载

微纳光纤谐振腔

微纳光纤谐振腔

微纳光纤谐振腔引言微纳光纤谐振腔是光学领域的一项重要研究方向,它在光学传输、光学通信、生物医学等领域具有广泛的应用前景。

本文将详细探讨微纳光纤谐振腔的原理、结构及其在不同领域中的应用。

原理微纳光纤谐振腔的原理是基于光在光纤中的传输特性及谐振模式的形成。

在微纳尺度下,光纤的直径趋近于光的波长,这样可以实现光纤的高度限制。

当光线在纤芯中传输时,会发生多次反射,并在纤芯中形成谐振模式。

这些谐振模式可以用于传输和储存光能,从而实现光信号的传输和处理。

结构微纳光纤谐振腔的结构是由微纳光纤、镜面和激光器等组成的。

微纳光纤是其中的核心组件,它具有非常小的直径和高的折射率。

微纳光纤常常采用光纤拉制、光刻等微纳加工技术制备而成。

镜面是用于光的反射和形成谐振模式的组件,可以采用金属、介质等不同材料制成。

应用微纳光纤谐振腔在光学传输、光学通信和生物医学等领域中具有广泛的应用。

光学传输微纳光纤谐振腔可以用于光信号的传输和处理。

由于其微小的尺寸和高度限制的特性,它可以实现高密度和高速度的光传输,有助于提高光通信和光网络的传输能力。

光学通信微纳光纤谐振腔可以用于光通信系统中的光源、光放大器和光调制器等组件。

谐振腔可以实现高效率的激光发射和调制,从而提高光通信系统的性能和稳定性。

生物医学微纳光纤谐振腔在生物医学领域中有着广泛的应用。

它可以用于生物传感、病原体检测和细胞成像等方面。

由于其微小的尺寸和高灵敏度的特性,它可以实现对生物样本的高分辨率成像和高灵敏度的检测,有助于提高生物医学诊断的准确性和效率。

结论微纳光纤谐振腔是一项重要的光学研究方向,具有广泛的应用潜力。

通过理解微纳光纤谐振腔的原理和结构,可以实现对光信号的传输和处理。

在光学传输、光学通信和生物医学等领域中,微纳光纤谐振腔都可以发挥重要作用,并有望为相关领域的发展提供新的可能性。

参考文献1.Smith J, Johnson A. Microfiber resonator modulators for opticalcommunications[C]//CLEO: Science and Innovations. Optical Societyof America, 2012: 1-2.2.Xu Y, Ilchenko V S, Maleki L.Whispering-gallery modes inmicroresonators: ultralow-threshold laser oscillation and SBS-induced frequency comb generation[J].Journal of the OpticalSociety of America B,2007,24(3):585-590.3.Cai M, Painter O, Vahala K J, et al. Observation of CriticalCoupling in a Fiber Taper to a Silica-Microsphere Whispering-Gallery Mode System[J]. Physical Review Letters, 2000, 85(1):74-77.4.Vollmer F, Arnold S.Whispering-gallery-mode biosensing: label-freedetection down to single molecules[J]. Nature methods, 2008,5(7):591.引言简单明了地介绍微纳光纤谐振腔的重要性和应用领域。

磁共振(磁谐振耦合)无线充电技术鼻祖级文章-英文原文

磁共振(磁谐振耦合)无线充电技术鼻祖级文章-英文原文

Wireless Power Transfer via Strongly Coupled Magnetic ResonancesAndré Kurs,1* Aristeidis Karalis,2 Robert Moffatt,1 J. D. Joannopoulos,1 Peter Fisher,3Marin Soljačić11Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. 2Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. 3Department of Physics and Laboratory for Nuclear Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.*To whom correspondence should be addressed. E-mail: akurs@Using self-resonant coils in a strongly coupled regime, we experimentally demonstrate efficient non-radiative power transfer over distances of up to eight times the radius of the coils. We demonstrate the ability to transfer 60W with approximately 40% efficiency over distances in excess of two meters. We present a quantitative model describing the power transfer which matches the experimental results to within 5%. We discuss practical applicability and suggest directions for further studies. At first glance, such power transfer is reminiscent of the usual magnetic induction (10); however, note that the usual non- resonant induction is very inefficient for mid-range applications.Overview of the formalism. Efficient mid-range power transfer occurs in particular regions of the parameter space describing resonant objects strongly coupled to one another. Using coupled-mode theory to describe this physical system (11), we obtain the following set of linear equationsIn the early 20th century, before the electrical-wire grid, Nikola Tesla (1) devoted much effort towards schemes to a&m(t)=(iωm-Γm)a m(t)+∑iκmn a n(t)+F m(t)n≠m(1)transport power wirelessly. However, typical embodiments (e.g. Tesla coils) involved undesirably large electric fields. During the past decade, society has witnessed a dramatic surge of use of autonomous electronic devices (laptops, cell- phones, robots, PDAs, etc.) As a consequence, interest in wireless power has re-emerged (2–4). Radiative transfer (5), while perfectly suitable for transferring information, poses a number of difficulties for power transfer applications: the efficiency of power transfer is very low if the radiation is omnidirectional, and requires an uninterrupted line of sight and sophisticated tracking mechanisms if radiation is unidirectional. A recent theoretical paper (6) presented a detailed analysis of the feasibility of using resonant objects coupled through the tails of their non-radiative fields for mid- range energy transfer (7). Intuitively, two resonant objects of the same resonant frequency tend to exchange energy efficiently, while interacting weakly with extraneous off- resonant objects. In systems of coupled resonances (e.g. acoustic, electro-magnetic, magnetic, nuclear, etc.), there is often a general “strongly coupled” regime of operation (8). If one can operate in that regime in a given system, the energy transfer is expected to be very efficient. Mid-range power transfer implemented this way can be nearly omnidirectional and efficient, irrespective of the geometry of the surrounding space, and with low interference and losses into environmental objects (6).Considerations above apply irrespective of the physical nature of the resonances. In the current work, we focus on one particular physical embodiment: magnetic resonances (9). Magnetic resonances are particularly suitable for everyday applications because most of the common materials do not interact with magnetic fields, so interactions with environmental objects are suppressed even further. We were able to identify the strongly coupled regime in the system of two coupled magnetic resonances, by exploring non-radiative (near-field) magnetic resonant induction at MHzfrequencies. where the indices denote the different resonant objects. The variables a m(t) are defined so that the energy contained in object m is |a m(t)|2, ωm is the resonant frequency of thatisolated object, and Γm is its intrinsic decay rate (e.g. due to absorption and radiated losses), so that in this framework anuncoupled and undriven oscillator with parameters ω0 and Γ0 would evolve in time as exp(iω0t –Γ0t). The κmn= κnm are coupling coefficients between the resonant objects indicated by the subscripts, and F m(t) are driving terms.We limit the treatment to the case of two objects, denoted by source and device, such that the source (identified by the subscript S) is driven externally at a constant frequency, and the two objects have a coupling coefficient κ. Work is extracted from the device (subscript D) by means of a load (subscript W) which acts as a circuit resistance connected to the device, and has the effect of contributing an additional term ΓW to the unloaded device object's decay rate ΓD. The overall decay rate at the device is therefore Γ'D= ΓD+ ΓW. The work extracted is determined by the power dissipated in the load, i.e. 2ΓW|a D(t)|2. Maximizing the efficiency η of the transfer with respect to the loading ΓW, given Eq. 1, is equivalent to solving an impedance matching problem. One finds that the scheme works best when the source and the device are resonant, in which case the efficiency isThe efficiency is maximized when ΓW/ΓD= (1 + κ2/ΓSΓD)1/2. It is easy to show that the key to efficient energy transfer is to have κ2/ΓSΓD> 1. This is commonly referred to as the strongcoupling regime. Resonance plays an essential role in thisDS S D'' power transfer mechanism, as the efficiency is improved by approximately ω2/ΓD 2 (~106 for typical parameters) compared to the case of inductively coupled non-resonant objects. Theoretical model for self-resonant coils. Ourexperimental realization of the scheme consists of two self- resonant coils, one of which (the source coil) is coupled inductively to an oscillating circuit, while the other (the device coil) is coupled inductively to a resistive load (12) (Fig. 1). Self-resonant coils rely on the interplay between distributed inductance and distributed capacitance to achieve resonance. The coils are made of an electrically conducting wire of total length l and cross-sectional radius a wound into Given this relation and the equation of continuity, one finds that the resonant frequency is f 0 = 1/2π[(LC )1/2]. We can now treat this coil as a standard oscillator in coupled-mode theory by defining a (t ) = [(L /2)1/2]I 0(t ).We can estimate the power dissipated by noting that the sinusoidal profile of the current distribution implies that the spatial average of the peak current-squared is |I 0|2/2. For a coil with n turns and made of a material with conductivity σ, we modify the standard formulas for ohmic (R o ) and radiation (R r ) µ0ω l a helix of n turns, radius r , and height h . To the best of our knowledge, there is no exact solution for a finite helix in the literature, and even in the case of infinitely long coils, the solutions rely on assumptions that are inadequate for our R o = 2σ 4πa µ πωr 42 ωh 2 (6)system (13). We have found, however, that the simple quasi- R =0 n 2 + (7)static model described below is in good agreementr ε 12 c3π3 c(approximately 5%) with experiment.We start by observing that the current has to be zero at the ends of the coil, and make the educated guess that the resonant modes of the coil are well approximated bysinusoidal current profiles along the length of the conducting wire. We are interested in the lowest mode, so if we denote by s the parameterization coordinate along the length of the conductor, such that it runs from -l /2 to +l /2, then the time- dependent current profile has the form I 0 cos(πs /l ) exp(i ωt ). It follows from the continuity equation for charge that the linear charge density profile is of the form λ0 sin(πs /l ) exp(i ωt ), so the two halves of the coil (when sliced perpendicularly to its axis) contain charges equal in magnitude q 0 = λ0l /π but opposite in sign.As the coil is resonant, the current and charge density profiles are π/2 out of phase from each other, meaning that the real part of one is maximum when the real part of the other is zero. Equivalently, the energy contained in the coil is 0The first term in Eq. 7 is a magnetic dipole radiation term(assuming r << 2πc /ω); the second term is due to the electric dipole of the coil, and is smaller than the first term for our experimental parameters. The coupled-mode theory decay constant for the coil is therefore Γ = (R o + R r )/2L , and its quality factor is Q = ω/2Γ.We find the coupling coefficient κDS by looking at the power transferred from the source to the device coil,assuming a steady-state solution in which currents and charge densities vary in time as exp(i ωt ).P =⎰d rE (r )⋅J (r ) =-⎰d r (A&S (r )+∇φS (r ))⋅J D (r ) at certain points in time completely due to the current, and at other points, completely due to the charge. Usingelectromagnetic theory, we can define an effective inductance L and an effective capacitance C for each coil as follows:=-1⎰⎰d r d r ' µJ &S(r ')+ρS(r ') 4π |r -r |ε0≡-i ωMI S I Dr '-r|r '-r |3⋅J D (r )(8)L =µ04π |I 0 |⎰⎰d r d r 'J (r )⋅J (r ')|r -r '|where the subscript S indicates that the electric field is due to the source. We then conclude from standard coupled-mode theory arguments that κDS = κSD = κ = ωM /2[(L S L D )1/2]. When 1 1 ρ(r )ρ(r ') the distance D between the centers of the coils is much larger= C 4πε 0 |q 0 | ⎰⎰d r d r ' |r -r '|(4)than their characteristic size, κ scales with the D -3dependence characteristic of dipole-dipole coupling. Both κ and Γ are functions of the frequency, and κ/Γ and the where the spatial current J (r ) and charge density ρ(r ) are obtained respectively from the current and charge densities along the isolated coil, in conjunction with the geometry of the object. As defined, L and C have the property that the efficiency are maximized for a particular value of f , which is in the range 1-50MHz for typical parameters of interest. Thus, picking an appropriate frequency for a given coil size, as we do in this experimental demonstration, plays a major role in optimizing the power transfer.1 2Comparison with experimentallydeterminedU =2 L |I 0 |parameters. The parameters for the two identical helical coils built for the experimental validation of the power 1 2 transfer scheme are h = 20cm, a = 3mm, r = 30 cm, and n = =2C|q 0 | (5)5.25. Both coils are made of copper. The spacing between loops of the helix is not uniform, and we encapsulate theuncertainty about their uniformity by attributing a 10% (2cm) uncertainty to h . The expected resonant frequency given these22dimensions is f0 = 10.56 ± 0.3MHz, which is about 5% off from the measured resonance at 9.90MHz.The theoretical Q for the loops is estimated to be approximately 2500 (assuming σ = 5.9 × 107 m/Ω) but the measured value is Q = 950±50. We believe the discrepancy is mostly due to the effect of the layer of poorly conductingcopper oxide on the surface of the copper wire, to which the current is confined by the short skin depth (~20μm) at this frequency. We therefore use the experimentally observed Q and ΓS= ΓD= Γ = ω/2Q derived from it in all subsequent computations.We find the coupling coefficient κ experimentally by placing the two self-resonant coils (fine-tuned, by slightly adjusting h, to the same resonant frequency when isolated) a distance D apart and measuring the splitting in the frequencies of the two resonant modes. According to coupled-mode theory, this splitting should be ∆ω = 2[(κ2-Γ2)1/2]. In the present work, we focus on the case where the two coils are aligned coaxially (Fig. 2), although similar results are obtained for other orientations (figs. S1 and S2).Measurement of the efficiency. The maximum theoretical efficiency depends only on the parameter κ/[(L S L D)1/2] = κ/Γ, which is greater than 1 even for D = 2.4m (eight times the radius of the coils) (Fig. 3), thus we operate in the strongly- coupled regime throughout the entire range of distances probed.As our driving circuit, we use a standard Colpitts oscillator whose inductive element consists of a single loop of copper wire 25cm in radius(Fig. 1); this loop of wire couples inductively to the source coil and drives the entire wireless power transfer apparatus. The load consists of a calibrated light-bulb (14), and is attached to its own loop of insulated wire, which is placed in proximity of the device coil and inductively coupled to it. By varying the distance between the light-bulb and the device coil, we are able to adjust the parameter ΓW/Γ so that it matches its optimal value, given theoretically by (1 + κ2/Γ2)1/2. (The loop connected to the light-bulb adds a small reactive component to ΓW which is compensated for by slightly retuning the coil.) We measure the work extracted by adjusting the power going into the Colpitts oscillator until the light-bulb at the load glows at its full nominal brightness.We determine the efficiency of the transfer taking place between the source coil and the load by measuring the current at the mid-point of each of the self-resonant coils with a current-probe (which does not lower the Q of the coils noticeably.) This gives a measurement of the current parameters I S and I D used in our theoretical model. We then compute the power dissipated in each coil from P S,D=ΓL|I S,D|2, and obtain the efficiency from η = P W/(P S+ P D+P W). To ensure that the experimental setup is well described by a two-object coupled-mode theory model, we position the device coil such that its direct coupling to the copper loop attached to the Colpitts oscillator is zero. The experimental results are shown in Fig. 4, along with the theoretical prediction for maximum efficiency, given by Eq. 2. We are able to transfer significant amounts of power using this setup, fully lighting up a 60W light-bulb from distances more than 2m away (figs. S3 and S4).As a cross-check, we also measure the total power going from the wall power outlet into the driving circuit. The efficiency of the wireless transfer itself is hard to estimate in this way, however, as the efficiency of the Colpitts oscillator itself is not precisely known, although it is expected to be far from 100% (15). Still, the ratio of power extracted to power entering the driving circuit gives a lower bound on the efficiency. When transferring 60W to the load over a distance of 2m, for example, the power flowing into the driving circuit is 400W. This yields an overall wall-to-load efficiency of 15%, which is reasonable given the expected efficiency of roughly 40% for the wireless power transfer at that distance and the low efficiency of the Colpitts oscillator.Concluding remarks. It is essential that the coils be on resonance for the power transfer to be practical (6). We find experimentally that the power transmitted to the load drops sharply as either one of the coils is detuned from resonance. For a fractional detuning ∆f/f0 of a few times the inverse loaded Q, the induced current in the device coil is indistinguishable from noise.A detailed and quantitative analysis of the effect of external objects on our scheme is beyond the scope of the current work, but we would like to note here that the power transfer is not visibly affected as humans and various everyday objects, such as metals, wood, and electronic devices large and small, are placed between the two coils, even in cases where they completely obstruct the line of sight between source and device (figs. S3 to S5). External objects have a noticeable effect only when they are within a few centimeters from either one of the coils. While some materials (such as aluminum foil, styrofoam and humans) mostly just shift the resonant frequency, which can in principle be easily corrected with a feedback circuit, others (cardboard, wood, and PVC) lower Q when placed closer than a few centimeters from the coil, thereby lowering the efficiency of the transfer.When transferring 60W across 2m, we calculate that at the point halfway between the coils the RMS magnitude of the electric field is E rms= 210V/m, that of the magnetic field isH rms= 1A/m, and that of the Poynting vector is S rms=3.2mW/cm2 (16). These values increase closer to the coils, where the fields at source and device are comparable. For example, at distances 20cm away from the surface of the device coil, we calculate the maximum values for the fields to be E rms= 1.4kV/m, H rms= 8A/m, and S rms= 0.2W/cm2. The power radiated for these parameters is approximately 5W, which is roughly an order of magnitude higher than cell phones. In the particular geometry studied in this article, the overwhelming contribution (by one to two orders of magnitude) to the electric near-field, and hence to the near- field Poynting vector, comes from the electric dipole moment of the coils. If instead one uses capacitively-loaded single- turn loop design (6) - which has the advantage of confining nearly all of the electric field inside the capacitor - and tailors the system to operate at lower frequencies, our calculations show (17) that it should be possible to reduce the values cited above for the electric field, the Poynting vector, and the power radiated to below general safety regulations (e.g. the IEEE safety standards for general public exposure(18).) Although the two coils are currently of identical dimensions, it is possible to make the device coil small enough to fit into portable devices without decreasing the efficiency. One could, for instance, maintain the product of the characteristic sizes of the source and device coils constant, as argued in (6).We believe that the efficiency of the scheme and the power transfer distances could be appreciably improved by silver-plating the coils, which should increase their Q, or by working with more elaborate geometries for the resonant objects (19). Nevertheless, the performance characteristics of the system presented here are already at levels where they could be useful in practical applications.References and Notes1. N. Tesla, U.S. patent 1,119,732 (1914).2.J. M. Fernandez, J. A. Borras, U.S. patent 6,184,651(2001).3.A. Esser, H.-C. Skudelny, IEEE Trans. Indust. Appl. 27,872(1991).4.J. Hirai, T.-W. Kim, A. Kawamura, IEEE Trans. PowerElectron. 15, 21(2000).5.T. A. Vanderelli, J. G. Shearer, J. R. Shearer, U.S. patent7,027,311(2006).6.A. Karalis, J. D. Joannopoul os, M. Soljačić, Ann. Phys.,10.1016/j.aop.2007.04.017(2007).7.Here, by mid-range, we mean that the sizes of the deviceswhich participate in the power transfer are at least a few times smaller than the distance between the devices. For example, if the device being powered is a laptop (size ~ 50cm), while the power source (size ~ 50cm) is in thesame room as the laptop, the distance of power transfer could be within a room or a factory pavilion (size of the order of a fewmeters).8. T. Aoki, et al., Nature 443, 671 (2006).9.K. O’Brien, G. Scheible, H. Gueldner, 29th AnnualConference of the IEEE 1, 367(2003).10.L. Ka-Lai, J. W. Hay, P. G. W., U.S. patent7,042,196(2006).11.H. Haus, Waves and Fields in Optoelectronics(Prentice- Supporting Online Material/cgi/content/full/1143254/DC1SOM TextFigs. S1 to S530 March 2007; accepted 21 May 2007Published online 7 June 2007; 10.1126/science.1143254 Include this information when citing this paper.Fig. 1. Schematic of the experimental setup. A is a single copper loop of radius 25cm that is part of the driving circuit, which outputs a sine wave with frequency 9.9MHz. S and D are respectively the source and device coils referred to in the text. B is a loop of wire attached to the load (“light-bulb”). The various κ’s represent direct couplings between the objects indicated by the arrows. The angle between coil D and the loop A is adjusted to ensure that their direct coupling is zero, while coils S and D are aligned coaxially. The direct couplings between B and A and between B and S are negligible.Fig. 2. Comparison of experimental and theoretical values for κ as a function of the separation between coaxially aligned source and device coils (the wireless power transfer distance.) Fig. 3. Comparison of experimental and theoretical values for the parameter κ/Γ as a function of the wireless power transfer distance. The theory values are obtained by using the theoretical κ and the experimentally measured Γ. The shaded area represents the spread in the theoretical κ/Γ due to the 5% uncertainty in Q.Fig. 4. Comparison of experimental and theoretical efficiencies as functions of the wireless power transfer distance. The shaded area represents the theoretical prediction for maximum efficiency, and is obtained by inserting theHall, Englewood Cliffs, NJ, 1984).12.The couplings to the driving circuit and the load donot theoretical values from Fig. 3 into Eq. 2 [with Γκ2/Γ2 1/2 W /ΓD= (1 +have to be inductive. They may also be connected by awire, for example. We have chosen inductive coupling in the present work because of its easier implementation. 13.S. Sensiper, thesis, Massachusetts Institute of Technology(1951).14.We experimented with various power ratings from 5W to75W.15.W. A. Edson, Vacuum-Tube Oscillators (Wiley, NewYork,1953).16.Note that E ≠cμ0H, and that the fields are out of phaseand not necessarily perpendicular because we are not in a radiativeregime.17.See supporting material on Science Online.18.IEEE Std C95.1—2005 IEEE Standard for Safety Levelswith Respect to Human Exposure to Radio FrequencyElectromagnetic Fields, 3 kHz to 300 GHz (IEEE,Piscataway, NJ,2006).19. J. B. Pendry, Science 306, 1353 (2004).20. The authors would like to thank John Pendry forsuggesting the use of magnetic resonances, and Michael Grossman and Ivan Čelanović for technical assistance.This work was supported in part by the Materials Research Science and Engineering Center program of the National Science Foundation under Grant No. DMR 02-13282, by the U.S. Department of Energy under Grant No. DE-FG02-99ER45778, and by the Army Research Officethrough the Institute for Soldier Nanotechnologies under Contract No. DAAD-19-02-D0002.) ]. The black dots are the maximum efficiency obtained from Eq. 2 and the experimental values of κ/Γ from Fig. 3. The red dots present the directly measured efficiency,as described in thetext.。

超导相干峰与超导序参量的关系_概述及解释说明

超导相干峰与超导序参量的关系_概述及解释说明

超导相干峰与超导序参量的关系概述及解释说明1. 引言1.1 概述超导相干峰和超导序参量是固态物理学中重要的概念,它们在研究和理解超导现象中起着关键作用。

超导相干峰是指在超导材料中出现的能谱中的特殊峰值,其存在与否以及特征参数对于研究超导机制具有重要意义。

而超导序参量则描述了系统的超导性质和相变过程。

本文旨在探讨超导相干峰与超导序参量之间的关系,并对其进行综述和解释说明。

1.2 文章结构本文将分为四个主要部分:引言、超导相干峰与超导序参量的关系、解释说明以及结论。

首先,在引言部分将简要介绍文章涉及的主题,并提供一个整体概述。

接下来,重点讨论超导相干峰和超导序参量各自的定义和性质,包括介绍它们在实验上的观测方法、数学表达以及物理意义等内容。

然后,我们将详细探讨二者之间的联系和对比,以揭示它们在理论模型中的相互依赖关系和共同作用机制。

在解释说明部分,将介绍本研究中采用的研究方法和实验设计,并对结果进行分析和解释。

最后,我们将总结文章的主要发现并对未来的研究方向进行展望。

1.3 目的本文旨在深入探讨超导相干峰和超导序参量之间的关系,为理解复杂的超导现象提供更加全面和系统的认识。

通过比较和对比二者,揭示它们在超导机制中的相互联系,进一步推动超导材料领域的研究和发展。

同时,我们也希望通过本文为后续相关研究提供指导和启发,拓展这一领域的知识边界。

以上是文章“1. 引言”部分内容,请根据需要进行修改补充。

2. 超导相干峰与超导序参量的关系2.1 超导相干峰的定义和性质超导相干峰是指在超导体材料中某一特定温度下,由于电子对的形成而产生的一种局域电子态。

它通常表现为能隙下方发生能量增强的尖锐峰值,并且在温度降低时逐渐增强并最终消失。

超导相干峰具有以下几个重要性质:1. 能隙特征:超导相干峰通常出现在超导材料中存在能隙的范围内。

这个能隙是由于库伯对(Cooper pairs)形成而产生的,而库伯对正是超导电流的基本载流子。

Simcenter 3D软件产品介绍说明书

Simcenter 3D软件产品介绍说明书

Complex industrial problems require solutions that span a multitude of physical phenomena, which often can only be solved using simulation techniques that cross several engineering disciplines. This has significant consequences for the computer-aided engineering (CAE) engineer. In the simplest case, he or she may expect the solution to be based on a weakly-coupled scenario in which two or more solvers are chained. The first one provides results to be used as data by the next one, with some iterations to be performed manually until convergence is reached. But unfortunately, many physical problems are more complex! In that case, a complex algorithmic basis and fully integrated and coupled resolution schemes are required to achieve convergence (the moment at which all equations related to the different physics are satisfied).Simcenter™ 3D software offers products for multiphys-ics simulation and covers both weak and strong cou-pling. The capabilities concern thermal flow, thermome-chanical, fluid structure, vibro-acoustics,aero-vibro-acoustics, aero-acoustics, electromagneticSolution benefits• Enables users to take advantage of industry-standard solvers for a full range of applications • Makes multiphysics analysis safer, more effective and reliable • Enables product developers to comprehend the complicated behavior that affects their designs • Promotes efficiency and innovation in the product development process • Provides better products that fulfill functional requirements and provide customers with a safe and durable solutionSiemens Digital Industries SoftwareSimcenter 3D formultiphysics simulationLeveraging the use of industry-standard solvers for a full range of applicationsthermal and electromagnetic-vibro-acoustic. Fully coupled issues deal with thermomechanical, fluid-ther-mal and electromagnetic-thermal problems.One integrated platform for multiphysics Simcenter 3D combines all CAE solutions in one inte-grated platform and enables you to take advantage of industry-standard solvers for a full range of applica-tions. This integration enables you to implement a streamlined multi-physical development process mak-ing multiphysics analysis safer, more effective and reliable.This enables product developers to comprehend the complicated behavior that affects their designs. Understanding how a design will perform once in a tangible form, as well as knowledge of the strengths and weaknesses of different design variants, promotes innovation in the product development process. This results in better products that fulfill functional require-ments and provide target customers with a safe and durable solution.Enabling multiphysics analysisRealistic simulation must consider the real-world inter-actions between physics domains. Simcenter 3D brings together world-class solvers in one platform, making multiphysics analysis safer, more effective and reliable. Results from one analysis can be readily cascaded to the next.Various physics domains can be securely coupled with-out complex external data links. You can easily include motion-based loads in structures and conduct multi-body dynamic simulation with flexible bodies and controls, vibro-acoustic analysis, thermomechanical analysis, thermal and flow analysis and others that are strongly or weakly coupled. You can let simulation drive the design by constantly optimizing multiple performance attributes simultaneously. Quickening the pace of multiphysics analysisWith the help of Simcenter 3D Engineering Desktop, multiphysics models are developed based on common tools with full associativity between CAE and computer-aided design (CAD) data. Any existing analysis data can be easily extended to address additional physics aspects by just adapting physical properties and bound-ary conditions, but keeping full associativity and re-using a maximum of data.One-way data exchange Two-way data exchange (co-simulation)Integrated coupledSolution guide |Simcenter 3D for multiphysics simulationIndustry applicationsSimcenter 3D multiphysics solutions can help designers from many industries achieve a better understanding of the complex behavior of their products in real-life conditions, thereby enabling them to produce better designs.Aerospace and defense• Airframe-Thermal/mechanical temperature and thermalstress for skin and frame-Vibro-acoustics for cabin sound pressure stemming from turbulent boundary layer loading of thefuselage-Flow/aero-acoustics for cabin noise occurring inclimate control systems-Thermal/flow for temperature prediction inventilation-Curing simulation for composite components topredict spring-back distortion• Aero-engine-Thermal/mechanical temperature and thermalstress/distortion for compressors and turbines-Thermal/flow for temperature and flow pressuresfor engine system-Flow/aero-acoustic for propeller noise-Electromagnetic/vibro-acoustics for electric motor(EM) noise in hybrid aircraft-Electromagnetic/thermal for the electric motor • Aerospace and defense-Satellite: Thermal/mechanical orbital temperatures and thermal distortion-Satellite: Vibro-acoustic virtual testing of spacecraft integrity due to high acoustic loads during launch -Launch vehicles: Thermal/mechanical temperature and thermal stress for rocket engines Automotive – ground vehicles• Body-Vibro-acoustics for cabin noise due to engine androad/tire excitation-Flow/vibro-acoustics for cabin noise due to windloading-Thermal/flow for temperature prediction and heatloss in ventilation • Powertrain/driveline-Vibro-acoustics for radiated noise from engines,transmissions and exhaust systems-Thermal/flow for temperature prediction in cooling and exhaust systems-Electromagnetic/vibro-acoustic for EM noise-Electromagnetic/thermal for the electric motorperformance analysisMarine• Propulsion systems-Vibro-acoustics for radiated noise from engines,transmissions and transmission loss of exhaustsystems-Flow/acoustics to predict acoustic radiation due to flow induced pressure loads on the propeller blades -Thermal/flow for temperature prediction in piping systems-Hull stress from wave loads-Electromagnetic/thermal analysis for electricpropulsion systemsConsumer goods• Packaging-Thermal/flow for simulating the manufacture ofplastic components-Mold cooling analysesElectronics• Electronic boxes-Thermal/flow for component temperatureprediction and system air flow in electronicsassemblies and packages-Flow/aero-acoustics noise emitted from coolingfans due to flow-induced pressure loads on fanblades• Printed circuit boards-Thermal/mechanical for stress and distortionUsing Simcenter 3D enables you to map results from one solution to a boundary condition in a second solu-tion. Meshes can be dissimilar and the mapping opera-tion can be performed using different options.Benefits• Make multiphysics analysis more effective andreliable by using a streamlined development process within an integrated environment Key features• Create fields from simulation results and use them as a boundary conditions: a table or reference field, 3D spatial at single time step or multiple time steps, scalar (for example, temperature) and vector (for example, displacement)• Map temperature results from Simcenter 3D Thermal to Simcenter Nastran® software • Use pressure and temperature results fromSimcenter 3D Flow in Simcenter Nastran analysis • Leverage displacement results from Simcenter Nastran for acoustics finite element method (FEM) and boundary element (BEM) computations • Employ pressure and temperature results from Simcenter STAR-CCM+™ software for aero-vibro-acoustics analysis • Exploit stator forces results from electromagnetics simulation for vibro-acoustics analysis • Third-party solvers can be used for mapping: ANSYS, ABAQUS, MSC Nastran, LS-DYNASimcenter 3D Advanced Thermal leverages the multi-physics environment to solve thermomechanical prob-lems in loosely (one-way) or tightly coupled (two-way) modes.This environment delivers a consistent look and feel for performing multiphysics simulations, so the user can easily build coupled solutions on the same mesh using common element types, properties and boundary conditions, as well as solver controls and options. Coupled thermal-structural analysis enables users to leverage the Simcenter Nastran multi-step nonlinear solver and a thermal solution from the Simcenter 3D Thermal solver.Benefits• Extend mechanical and thermal solution capabilities in Simcenter 3D to simulate complex phenomena with a comprehensive set of modeling tools• Reduce costly physical prototypes and product design risk with high-fidelity thermal-mechanical simulation• Gain further insight about the physics of your products• Leverage all the capabilities of the Simcenter 3D integrated environment to make quick design changes and provide rapid feedback on thermal performanceKey features• Advanced simulation options for coupled thermomechanical analysis of turbomachinery and rotating systems• Tightly-coupled thermomechanical analysis with Simcenter Nastran for axisymmetric, 2D and 3D representations• Combines Simcenter Nastran multi-step nonlinear solution with industry-standard Simcenter Thermal solversSimcenter 3D Advanced Flow software is a powerful and comprehensive solution for computational fluid dynamics (CFD) problems. Combined with Simcenter 3D Thermal and Simcenter 3D Advanced Thermal, Simcenter 3D Advanced Flow solves a wide range of multiphysics scenarios involving strong coupling of fluid flow and heat transfer.Benefits• Gain insight through coupled thermo-fluid multiphysics analysis• Achieve faster results by using a consistent environment that allows you to quickly move from design to resultsKey features• Consider complex phenomena related to conjugate heat transfer• Speed solution time with parallel flow calculations • Couple 1D to 3D flow submodels to simulate complex systemsThe Simcenter Nastran software Advanced Acoustics module extends the capabilities of Simcenter Nastran for simulating exterior noise propagation from a vibrat-ing surface using embedded automatically matched layer (AML) technology. Simcenter Nastran is part of the Simcenter portfolio of simulation tools, and is used to solve structural, dynamics and acoustics simulation problems. The Simcenter Nastran Advanced Acoustics module enables fully coupled vibro-acoustic analysis of both interior and exterior acoustic problems.Benefits• Easily perform both weakly and fully coupled vibro-acoustic simulations • Simulate acoustic problems faster and moreefficiently with the next-generation finite element method adaptive order (FEMAO) solver Key features• Simulate acoustic performance for interior, exterior or mixed interior-exterior problems • Correctly apply anechoic (perfectly absorbing, without reflection) boundary conditions• Correctly represent loads from predecessorsimulations: mechanical multibody simulation, flow-induced pressure loads on a structure and electromagnetic forces in electric machines • Include porous (rigid and limp frames) trim materials in both acoustic and vibro-acoustic analysis • Request results of isolated grid or microphone points at any location • Define infinite planes to simulate acoustic radiation from vibrating structures close to reflecting ground and wall surfacesElectromagneticsStructural dynamicsAcousticsThis product supports creating aero-acoustic sources close to noise-emitting turbulent flows and allows you to compute their acoustic response in the environment (exterior or interior); for example, for noise from heat-ing ventilation and air conditioning (HVAC) or environ-mental control system (ECS) ducts, train boogies and pantographs, cooling fans and ship and aircraft propel-lers. The product also allows you to define wind loads acting on structural panels, leading to vibro-acoustic response; for instance, in a car or aircraft cabin.Module benefits• Derive lean, surface pressure-based aero-acoustic sources for steady or rotating surfaces• Scalable and user-friendly load preparation for aero-vibro-acoustic wind-noise simulations• Import binary files with load data directly into Simcenter Nastran for response computationsKey features• Conservative mapping of pressure results from CFD to the acoustic or structural mesh• Equivalent aero-acoustic surface dipole sources • Equivalent aero-acoustic fan source for both tonal and broadband noise• Wind loads, using either semi-empirical turbulent boundary layer (TBL) models or mapped pressure loads from CFD resultsSimcenter MAGNET™ Thermal software can be used to accurately simulate temperature distribution due to heat rise or cooling in the electromechanical device. Simcenter 3D seamlessly couples with the Simcenter MAGNET solver to provide further analysis: You can use power loss data from Simcenter MAGNET as a heat source and determine the impact of temperature changes on the overall design and performance. Each solver module is tailored to different design prob-lems and is available separately for both 2D and 3D designs.Module benefits• Achieve higher fidelity predictions by taking temperature effects into account in electromagnetic simulations• Leverage highly efficient coupling scenariosKey features• Simulates the temperature distributions caused by specified heat sources in the presence of thermally conductive materials• Couples with Simcenter MAGNET solver for heating effects due to eddy current and hysteresis losses in the magnetic systemSolution guide |Simcenter 3D for multiphysics simulationSiemens Digital Industries Software/softwareAmericas +1 314 264 8499Europe +44 (0) 1276 413200Asia-Pacific +852 2230 3333© 2019 Siemens. A list of relevant Siemens trademarks can be found here.Other trademarks belong to their respective owners.77927-C4 11/19 H。

铁道车辆专业英语

铁道车辆专业英语

Chapter 1 Introduction to Railway Locomotive 机车freight wagon货车passenger coach 客车multiple units动车组metro car 地铁车辆light rail轻轨railway service cars 铁路服务车Rail铁轨standard gauge标准轨距narrow gauge, broad gauge窄轨,宽轨Trackbed 道床Sleeper,枕木Crosstie 枕木 Ballast, subballast,道砟,底部道砟fastener紧固件Turnout道岔Derail(derailment)脱轨Crossing 平交道口colliery: 煤矿quarry:采石场flanged steel wheels:有凸缘钢轮copper ore:铜矿speak of:谈到,提及backbone:骨干bulk freight:散装货物mass commutation traffic: 大规模通勤运输short haul: 短途运输Merchandise traffic:货物运输Depreciation:(反-appreciation),减值,折旧,贬值Settling:沉降,沉积bulk freight:散装货物Subgrade: 地基,路基Soil stratum: 地层Embankment:堤坝Trim off:修剪Organic topsoil: 有机表层土Civil engineering: 土木工程Earthwork: 土方,土方工程Gravity wall:重力墙Drainage: 排水系统,排水装置Real estate:房地产,不动产Crane:起重机Tamper:捣固机Trolley:台车,手推车,电车Headway:进展,向目标前进Chapter 2 The TrainCoach, carriage,客车Monorail单轨Refrigerator wagon冷藏车High-speed railways高速铁路Maglev磁悬浮Open-topped wagon敞顶车Cog railway嵌齿铁路Rubber-tired underground橡胶轮地铁Siding旁轨,支线Freight train货运列车Passenger train旅客列车Heavy freight重载货运Sleeping car卧铺车Dining car餐车Run-around track调车线Inter-city train城际列车Local train管内列车,慢车Elctric traction电力牵引Stopper慢车Double-decked passenger train双层旅客列车Motor car (trailer car)动力车(拖车)Container集装箱车Tanker罐车Driving cab司机室TOFC平板拖车Box wagon棚车Coupler车钩Maintenance of way 道路维护Long-distance train长途列车Channel Tunnel海峡隧道parcel: package 包裹Travelling post offices:移动邮局Centrifugal force:离心力pram:婴儿车Wheelchair:轮椅Conurbation:有卫星城市的大都市elevated structure :高架结构Accelerate (decelerate): 加速(减速)Tram, trolley, streetcar:有轨电车Flexibility:机动,灵活Low loder:低架拖车Sneak into:偷偷地摸进Stow away:偷乘,搭白车Fatality:disasterKit:工具包,装备earn one‘s keep:值得雇用, 挣饭吃Show up:揭露,露出Dead end terminal:闭塞终端Buffer stop:止冲器Crossover:转辙轨Locomotive escape:机车折返Phase out:逐步淘汰,逐步停止Intensive service:auxiliary equipment:辅助设备, 备用设备, 附属设备Heavy maintenance:大修Whilst:时时,同时,whilePush-pull:推挽Interval service:Keep at forefront of:保持在……最前沿train loading:列车运载量Train capacity:列车运载能力Density of passengers:乘客密度Load factor:上座率Patronage:保护,光顾,赞助High degree of standardisation:高度标准化Headstock, end sill, pilot:end beamBellmouth:钟形口,喇叭口Line up:整队,排列Semipermanent coupler:半永久车钩Be bolted together:螺栓连接Cushioning:减震,缓冲Uncoupling:解钩,拆开(反,coupling)Buckeye, Knuckle and Janney coupler: 詹式车钩Coupler knuckle (jaw):钩舌Coupler head:钩头Hinge pin:折页销Fully automatic coupler:全自动车钩Disengage:脱离pneumatical:风力的,空气的Keep in good working order:保持正常运转状态Drawgear:牵引装置Bolt:螺栓Pedal:踏板Funicular: 索道Coupler alignment bar:车钩调直杆Pushbutton:按钮Shock absorber:减震器Multicore cable:多芯电缆Chapter 7 Railway Cars(1)Baggage行列车Coach客车Combine合造车Dome圆顶车 Lounge游乐车Dinner餐车Observation瞭望车Sleeper, sleeping car, Pullman卧铺车RPO铁路邮政车Housing car封闭车Autorack, auto carrier汽车运输车Boxcar, or van棚车Refrigerator car, reefer冷藏车Stock car牲畜车Open top car敞车Gondola敞车 Hopper漏斗车Ballast car砟车Flat car平车Depressed-center flat car凹底平车 Piggyback car背负式车Schnabel car钳夹车Tank car罐车Caboose守车Snow plow除雪犁Dynamometer car动力检测(试验)车Encompasss: 包围,环绕,构成,包括Listed in alphabetic order: 按字母顺序排列lining:衬里,衬套,内层,lined withContamination:污染,玷污Corrosive action:腐蚀作用Stainless steel:不锈钢Glass enamel:玻璃釉彩,搪瓷Pocket for stake: 柱插口Tie-down point:栓柱Manual brake equipment: 手制动Air brake equipment: 空气制动primary underframe: 主车架,主底架Cumbersome : 笨重的Intermodal shipping: 联合运输Tonnage:吨位log:木材,原木Lumber:木材Slope down:向下斜Scrap metal: 金属屑,废金属Aggregate:粒料,总计,聚集Wood chip:木屑,木片Drop end:落端门Shovel:铲Perishable freight:易腐货物spoiling: 变坏,损毁Insulation:绝缘层,保温层Keep out:Cooling system:冷却系统Cold brine:冷盐水Waterproof:防水的Airtight:密封的,气密的Warehouse:仓库,库房Breakage:破坏,破损Barrel:桶Drum:鼓型圆桶safety valve:安全阀Chapter 8 Railway Cars(2)For more information see/wiki/Passenger_car_(rail)Tilting train摆式列车Head-end equipment车端设备Branch line支线Air-conditioned hard seat car空调硬座车seating capacity定员Length between truck pivot centers车辆定距tare weight空重Clearance 间隙Wheelbase轴距Gauge轨距Constructional speed构造速度Wheel diameter车轮直径Stanhope:轻便马车en route:在途中Streamlined:流线型的Ornate:装饰的, 华丽的, (文体)绚丽的to date:到此为止Aluminum steel:铝钢,含铝钢evolve into:发展[进化]成Fluted:有凹槽的Conveyance:运输Row upon row:一排排,一行行carry-on:手提行李,手提的Aisle:走廊Partitioned into:分割,分隔开efficiency apartment:有小厨房和卫生设备的小套公寓房间,公寓小套间Interior:内部Galley:厨房Recede:后退,倒退,变得模糊Fell out of use: 开始不用,渐废Vantage:优势,有利情况Roofline:屋顶轮廓线Dumbwaiter:楼上楼下送饭菜的小升降机,可移动的上菜架或上菜桌Aluminum of high strength alloy:高强度铝合金pane:长方块, 尤指窗格, 窗格玻璃, 边, 面,方框Vestibule:门廊, 前厅Chapter 9 BogieRide comfort乘坐舒适性Irregularity轨道不平顺Wheel tread车轮踏面Suspension悬挂系统Tread gradient踏面锥度Flange轮缘Running performance运行品质Articulated bogies铰接式转向架Lower center of gravity低重心Swing hanger摇枕吊Bolster bogie摇枕转向架Bolsterless bogie无摇枕转向架Wheelset hunting轮对蛇行Anti-yaw damper抗蛇行减震器Suspension gear悬挂装置JR日本铁路Bogie frame构架Lateral damper横向减震器Traction transfer device牵引装置 Brake equipment制动装置Axle bearing and axle box轴箱轴承及轴箱Axle spring轴箱弹簧Brake disk制动盘Traction motor牵引电机Gear box齿轮箱,减速箱Wheelset轮对Traction force牵引力Air spring, air bag空气弹簧Side beam侧梁Coil spring圆弹簧Cross beam横梁Press welding压力焊Bearing轴承Support rigidity支撑刚度Pedestal swing spring type导框式定位Play,游间,游隙,摆动量Leaf spring板弹簧 IS typeIS拉板式定位Bending strength弯曲强度Unsprung mass(weight)Non-sprung mass簧下质量Axle beam type转臂式定位Cylindrical roller bearing圆柱滚子轴承Ball bearing球轴承Overhaul大修Nose suspension device轴悬,臂式悬挂装置Cardan driving device 万向轴驱动Torque converter变扭器Wheel tread brake踏面制动Disc brake盘型制动Brake shoe闸瓦Frictional heat摩擦热Brake pad制动闸片Motor braking动力制动Quill drive 空心轴驱动 Hollow shaft空心轴Gearwheel, driven gear从动齿轮Pinion, driving gear主动齿轮Electric locomotive电力机车Rail head轨头Reprofile镟修Wheel/rail interface轮轨关系Lubricant润滑物Flatted wheel车轮擦伤 Bogie transom转向架横梁Brake cylinder制动缸Parking brake停车制动 Heavy duty brake重载制动Frame mounted motor架悬式电机Lifting lug吊耳Gearbox齿轮箱Compressed air压缩空气WSP(wheel slide protection)车轮防滑装置Speed sensor速度传感器Pendulum (titling) bogie摆式转向架Service life使用寿命Design concept设计理念Running speed运行速度Maximum speed最大速度Lateral force横向力Transition curve过渡曲线Circular curve圆曲线Self-steering bogie自导向转向架Running stability 运行平稳性Forced steering bogie迫导向转向架Obscurity:隐蔽,偏僻,含糊Abrasion:磨耗In terms of:according toIn comparison to: 对比Be sensitive to:对……敏感Rotational resistance: 回转阻尼Harmonic:谐波, 和声, 谐函数Isolate …from…:隔离Be commercialized for: 商业化,商品化Welding technology: 焊接技术General structure:一般结构Rolled steel:钢材,轧制钢Seamless steel pipe: 无缝钢管Critical component:关键部件Corrugated wheel: 波形辐板车轮Susceptible to:易受影响的Mass imbalance:动量不平衡Resonance:共振Put into service:投入运营,交付使用Right angle cardan driving device:直角万向轴驱动装置Impede:stopForged steel:锻钢Porcupine:豪猪Rubber bushed links:用橡胶衬里的连杆Gearwheel:大齿轮In relation to: with regard to,关于,涉及,与……比较Degree of coning:锥度Squealing noise:尖啸Flange or rail greasing:轮缘或轨道油脂Slippage: 滑动Weled steel box format:焊接箱型结构Press against: 压向Neutral section:分相区Leading bogie:导向架Chapter 10 Vehicle SuspensionVehicle suspension车辆悬挂系统Cushion system缓冲系统Laminated steel spring板弹簧Axle load轴重Carrying load载重 Spring hanger弹簧吊Spring lank弹簧托板Swing link吊杆Side frame侧架,侧梁Side bearer (bearing)旁承Center bearing下心盘Equalizer bar suspension均衡梁式悬挂系统Commonwealth bogie均衡梁式转向架Levelling valve高度调节阀Solid rubber suspension pack橡胶堆悬挂系统Parlance:idiom,谈话,说法,用法Take the form of leaf steel spring: 采用板弹簧型式Securing strap:保护带,安全带Be left out for simplicity: 为简便起见,不显示(去掉)……End on:从一端看,从端面看,一端向前地Rivete:铆钉,固定Side view:侧视图Simplified diagram:简图Sideways movement:侧面运动Reversal:逆转Durability:耐久性, 耐用性; 坚固Axle box yoke:轴箱轭Rubber Chevron:V型橡胶Boarding and alighting:上车,落下Intermittent gentle hissing:断断续续的轻微的咝咝声Alight from:走下来,下车Chapter 11 BrakingKinetic energy动能Air brakes or pneumatic brakes空气制动Brake pipe列车管,制动管Compressor空气压缩机Main reservoir主风缸Driver’s brake valve司机阀Equalising reservoir均衡风缸Feed valve给气阀;进给阀Angle cock截断塞门,折角塞门Hose橡胶软管(制动软管)Auxiliary reservoir辅助风缸Triple valve三通阀Brake cylinder制动缸Brake block闸瓦Relay valve延迟阀Fail safe 失效安全F riction material摩擦材料Composition material复合材料Brake rigging制动装置 Rate of application制动倍率Slide valve滑阀Graduating valve递动阀,节制阀Regulating valve调整阀,调节阀Propagation rate制动波速Distributor分配阀Diaphragm,膜片Throttle节流阀slack action列车冲动E-P brake电空制动Dynamic braking动力制动Rheostatic braking电阻制动Regenerative braking再生制动Psi:Pounds per square inch磅/平方英尺Replenished:补充Trigger:打开,激发,引起Distributor:分配阀Sophisticated:复杂的Choke:阻气门Inshot:跃升装置; 跃升time lapse:时滞, 时延Elusive:令人困惑的; 油滑的; 难记忆的Spur:踢马剌, 剌激物, 刺激Essential ingredient:关键因素Thyristor:闸流晶体管; 半导体开关元件; 可控硅; 硅可控整流器Circuitry:电路, 线路Resistor:电阻器Power electronic:电力电子Chapter 12 Depots and WorkshopsSliding door滑动门,塞拉门Routine examination常规检查Consumable易损易耗件Maintenance regime维修体制Existing railway既有铁路Maintenance management维修管理Interchangeability互换性Operating pattern运行模式Converging聚集,会合Marshalling编组Electrified railway电气化铁路current collection equipment吸流装置Audit审计Performance indicator绩效指标maintenance standard维修标准Common sense: 常识Revisit:再访, 重游, 重临Draw on:戴上, 吸收, 利用, 引诱, 向...提取, 招来, 临近Rectify:矫正, 调整Progressively adverse effect on:日益增加的反作用Morale:士气,民心Upholstery:室内装潢Clomatic condition:天气条件Of equal importanceChore:家务杂事Contractual:契约的Good access to components:零部件的易接近性Superfluous:多余的, 过剩的, 过量的Watertight:不漏水的, 水密的Thwarted:反对; 阻挠, 挫败, 妨碍Overlook:俯瞰, 耸出, 远眺, 没注意到Refitting:整修, 改装premise:房产; 房屋Planning stage:计划阶段Termini:目的地, 界标,terminus 的复数Converging:集中,收敛,会聚Proximity:接近, 亲近Jack:插孔, 插座, 起重器, 千斤顶, 男人Inspection pit:检查坑Walkway:走道, 人行道Wheel turning facility:车轮加工设备Constructed wash roadDe-icing arrangement:防止结冰, 装以除冰装置, 除冰Fire alarm:火灾报警Chapter 13 Developing Maglev TrainsMagnetic field磁场Maglev磁悬浮Propulsion推进Levitation 悬浮Guidance导向Attractive force吸引力Ferromagnetic 电磁铁的Magnetic repulsion磁力推进Superconducting magnet超导磁体Linear motor线性电机Magnetizing rail磁化轨道Payload weight负载Dynamic load动载荷Electrodynamic suspension, EDS电力悬浮Electromagnetic suspension, EMS电磁悬浮No consensus exists on:Levitate: (使)轻轻浮起, (使)飘浮空中Cryogenics:低温学Linear synchronous motor: LSM同步直线电机Linear induction motor:LIM直线感应电机Gas turbine:燃气涡轮Turboprop:涡轮螺旋桨发动机Concurrently:同时发生的事件,并发的, 协作的, 一致的Availability crisis:Metropolitan:大城市Turbulence:骚乱, 动荡, (液体或气体的)紊乱HSGT,high-speed Ground Transportation ACT:FRA: Federal Railroad Administration 联邦铁路管理局[美]Chapter 14 Power Supply of Electric TractionPower supply供电 Electric traction system电力牵引系统 Overhead wire接触网Power transmission电力传输Third rail第三轨Collector受流器Pantograph受电弓 Return circuit回路 Substation配电站Earthing protection接地保护Signalling circuit信号电路Catenary接触网Dropper吊线Electric arc电弧Mast柱子Booster transformer, BT吸流变流器Return wire回流线Track magnet轨道磁铁Neutral section分相区Communication cable通信线缆Pigtail引线Diaper:尿布In parallel with:与...平行, 与...同时, 与...并联Microprocessor: 微处理器Grip with:掌握,理解Electrolysis: 电解Insulated:绝缘的,insulation, insulatorManhole: (锅炉, 下水道供人出入检修用的)人孔, 检修孔At one’s peril:由某人自担风险Take precautions to do:采取防范措施Aggravate:使恶化, 加重Stitching:用U字钉钉箱, 缝纫Sag:松弛, 下陷, 下垂, (物价)下跌, 漂流Evacuate:疏散, 撤出, 排泄Visual intrusion:视觉障碍,妨碍Chapter 15 The Light Rail TransitionCBI英国工业联合会Urban transport policy城市交通政策Urban sprawl城市扩张Light rail轻轨Road transport路面交通Steep gradient大坡道sharp curve小半径曲线Criteria标准Congested urban area:拥挤的城市区域House of Commons Transport Committee:上议院交通委员会Congested:拥挤的Pedestrians:步行者Cyclists:骑脚踏车的人Public transport user;公共交通使用者Motorists:乘汽车者AMA:Association of Metropolitan AuthoritiesIntractable:难处理的Down-marketed:价廉质次的, 低档市场的Park and ride:停车换乘Pollutant:污染物质Resurgence:复苏Overambitious:野心太大的Tyne:泰恩河Underutilized:为充分利用的Newcastle:纽卡斯尔。

三阶倒立摆

三阶倒立摆

三级倒立摆的研究与仿真摘要在现代工业控制领域中,我们接触的被控对象大多都是稳定,其实不稳定的对象也是普遍存在的。

倒立摆属于多变、快速、非线性、强耦合、和绝对不稳定系统。

倒立摆系统被认为是控制理论在科研教学中和实际实践中典型的、方便使用的物理模型,其控制方法在军用工业、航空航天、智能机器人和普通的工业控制过程中都有广泛的应用和重要的工程意义。

本文主要通过采用力学分析中的Lagrange方程来建立三级倒立摆动力学方程,并且使用LQR方法对三级倒立摆实现了稳定的控制,运用状态全维观测器实现了全维状态观测。

在MATLAB中实现了对三级倒立摆控制系统的仿真,并且从实验结果分析得到,三级倒立摆在LQR方法的控制下达到了稳定。

最后对全篇论文的研究进行总结。

关键词:倒立摆稳定控制LQR算法Research and simulation of triple inverted pendulumABSTRACTIn the modern industrial control field, we contact with most of the controlled object is stable, but unstable objects are universal. Inverted pendulum is a system which is nonlinear, multivariate, strong-coupling and unstable naturally. Inverted pendulum is a rare typical physical model which is used in teaching and researching control theory, the control methods are widely used in the military, aerospace, robotics and general industrial processes and also have important engineering significance.Though Lagrange equations in this paper by means of mechanics analysis to establish the dynamics equation of triple inverted pendulum, and using the LQR method of triple inverted pendulum stable control, using the full dimension observer realizes the full dimensional state observation. In MATLAB implements the triple inverted pendulum control system simulation, and from the experimental results, triple inverted on the control of LQR method is issued to the stable.Finally, summarizes the researching of the whole paper.KEY WORDS: Inverted pendulum stable control LQR algorithm三级倒立摆控制系统设计:倒立摆系统作为现代控制理论应用方面的一个典型实验系统,从六十年代就有许多人对它进行研究,提出了各种控制方案。

PhysRevB.81.153104

PhysRevB.81.153104

Optical evidence of strong coupling between valence-band holes and d-localized spinsin Zn1−x Mn x OV.I.Sokolov,1A.V.Druzhinin,1N.B.Gruzdev,1A.Dejneka,2O.Churpita,2Z.Hubicka,2L.Jastrabik,2and V.Trepakov2,3 1Institute of Metal Physics,UD RAS,S.Kovalevskaya Str.18,620041Yekaterinburg,Russia2Institute of Physics,AS CR,v.v.i.,Na Slovance2,18221Praha8,Czech Republic3Ioffe Institute,RAS,194021St-Petersburg,Russia͑Received3December2009;revised manuscript received2March2010;published30April2010͒We report on optical-absorption study of Zn1−x Mn x O͑x=0–0.06͒films on fused silica substrates takingspecial attention to the spectral range of the fundamental absorption edge͑3.1–4eV͒.Well-pronounced exci-tonic lines observed in the region3.40–3.45eV were found to shift to higher energies with increasing Mnconcentration.The optical band-gap energy increases with x too,reliably evidencing strong coupling betweenoxygen holes and localized spins of manganese ions.In the3.1–3.3eV region the optical-absorption curve inthe manganese-containedfilms was found to shift to lower energies with respect to that for undoped ZnO.Theadditional absorption observed in this range is interpreted as a result of splitting of a localized Zhang-Rice-typestate into the band gap.DOI:10.1103/PhysRevB.81.153104PACS number͑s͒:78.20.ϪeI.INTRODUCTIONDilute magnetic semiconductor Zn1−x Mn x O is one of themost promising materials for the development of optoelec-tronic and spin electronic devices with ferromagnetism re-tained at practical temperatures͑i.e.,Ͼ300K͒.However,researchers are confronted with many complex problems.Ferromagnetic ordering does not always appear and the na-ture of its instability is a subject of controversy.In addition,optical properties of Zn1−x Mn x O appreciably differ fromthose in Zn1−x Mn x Se and Zn1−x Mn x S related compounds,where the intracenter optical transitions of Mn2+ions areconventionally observed in the optical-absorption and photo-luminescence spectra.1,2In contrast,a very intense absorp-tion in the2.2–3.0eV region was reported in Zn1−x Mn x Owithout any manifestations of intracenter transitions,3–5and photoluminescence due to4T1→6A1optical transition of Mn2+is absent as well.Interpretation of this absorption bandas a charge transfer3,5is complicated by the fact that Mn2+forms neither d5/d4donor nor d5/d6acceptor levels in the forbidden gap of ZnO.6,7To resolve this contradiction,Dietl8put forward the con-cept that the oxides and nitrides belong to the little studiedfamily of dilute magnetic semiconductors with strong corre-lations.Characteristic features of such compounds are an in-crease in the band gap with the concentration of magneticions and emergence of a Zhang-Rice͑Z-R͒-type state in theforbidden gap9arising as a result of strong exchange cou-pling of3d-localized spin of the impurity centers andvalence-band holes.According to Ref.8,fulfillment ofstrong hybridization condition depends on the ratio of theimpurity-center potential U to a critical value U c;a coupledhybrid state can be formed when U/U cϾ1.Existence of such electronic state has been verified by ab initio theoretical treatment of electron correlations using the local spin-density approximation͑LSDA+U model͒and calculation of the ex-change coupling values.10In Zn1−x Mn x O the hole can origi-nate by electron transfer from the Mn2+adjacent oxygen to the conduction band.The resulting hole localizes as the Z-R state leading to appearance of additional broad,intense ab-sorption band.In this way the study of optical-absorptionspectra can be used as a probe to identify the Z-R states.It is known that the optical band-edge absorption spec-trum of Mn-doped ZnO is characterized by the onset of astrong rise of the absorption coefficient in theϳ3.1eV spec-tral region.11In Refs.11and12,this absorption inZn1−x Mn x Ofilms was treated as a product of direct interbandoptical transitions using conventional formula␣2ϳ͑ប␻−E g͒.The resulting magnitudes of band gap for composition with x=0.05have been estimated as E g=3.10eV͑Ref.11͒and3.25eV,12which is appreciably less than E g=3.37eV inZnO.13Such“redshift”of the band gap was considered inRef.12as a result of p-d exchange interaction,in analogy tothe shift of the excitonic lines in reflectivity and lumines-cence spectra observed in Ref.14for Zn1−x Mn x Se.At thesame time theory predicts an increase in E g͑x͒with x for Zn1−x Mn x O.8Also excitonic absorption spectrum in Zn1−x Mn x O nanopowders,15appeared to be located at ener-gies higher than that in ZnO nanopowders,that does not confirm the shift of E g to lower energies for Zn1−x Mn x O films.In this work we report on the optical-absorption spectrastudies in thin Zn1−x Mn x Ofilms deposited on fused silicaing suchfilms we succeed to detect the absorp-tion spectra of excitons and to determine reliably the widthof the optical gap E g.This allowed us to elucidate the natureof the additional absorption band appearing atប␻ϽE g near the fundamental absorption edge as a result of splitting of one more Z-R-type state due to strong hybridization and ex-change coupling of3d-localized spin of the manganese and valence-band oxygen hole.II.EXPERIMENTALThin Zn1−x Mn x Ofilms with x=0–0.06,120–130,and 200–250nm of thicknesses were deposited on fused silica substrates by the atmospheric barrier-torch discharge tech-nique,as it was described in Refs.16and17.The substratePHYSICAL REVIEW B81,153104͑2010͒temperature during deposition was kept at ϳ200°C.Mn content was controlled by measurements of Mn and Zn emis-sion ͑␭em =4031Åand 4810Å,respectively ͒of plasma during deposition and crosschecked by the postgown EPMA ͑JEOL JXA-733device with Kevex Delta Class V mi-croanalyser ͒analysis with accuracy Ϯ0.3%.X-ray diffrac-tion ͑XRD ͒studies were performed with a Panalytical X’PertMRD Pro diffractometer with Eulerian cradle using Cu K ␣radiation ͑␭em =1.5405Å͒in the parallel beam ge-ometry.XRD profiles were fitted with the Pearson VII func-tion by the DIFPATAN code.18Correction for instrumental broadening was performed using NIST LaB6standard and V oigt function method.19Optical absorption within the 1.2–6.5eV spectral region was measured in unpolarized light at room temperature using a Shimadzu UV-2401PC spectrophotometer.The bare silica substrate and Zn 1−x Mn x O film on silica substrate were mounted into the reference and test channel,respectively.The optical density ␣d ͑product of optical-absorption coeffi-cient and film thickness ͒was calculated without taking into account multiple reflections as ␣d =ln ͑I 0/I ͒,where I 0and I are intensities of light passed through bare substrate and film/substrate structure.III.RESULTS AND DISCUSSIONFigure 1presents XRD pattern for ZnO and Zn 0.95Mn 0.05O films,as an example.All obtained films re-vealed crystalline block structure with dominant ͑002͒orien-tation of blocks’optical C -axes aligned normal to substrate.Observed reflexes correspond to wurtzite structure evi-dencing absence of extraneous phases.Both pure and Mn-doped ZnO films appeared to be compressively strained with 0.2%of strain,s =͑a 0−a S ͒/a 0,where a 0and a S are the lattice parameters of nonstrained and strained films.The analysis reveals that the value of compressive strain is controlled pre-dominantly by stresses,but not by presence of Mn ͑at least for Mn concentrations used ͒.Figure 2presents the optical-absorption spectra for Zn 1−x Mn x O films.A wide absorption line is seen in the re-gion of the band edge ͑Fig.2͒,whose energy appears to be shifted by about 100meV to higher energies in comparison with the excitonic line in ZnO ͓ϳ3.31eV at T =300K ͑Ref.13͔͒.The line shift is very likely connected with the com-pressive strain of Zn 1−x Mn x O films mentioned above.The wide and shifted line has been observed earlier in ZnO film on sapphire substrate 20,21and was identified as a shift of the excitonic line due to compressive strain of Zn 1−x Mn x O films.21The inset represents spectra of this line obtained in ZnO at T =300K and 77.3K.It is seen that the excitonic line is narrowed,split into two components and shifted to higher energies on lowering the temperature,clearly evidenc-ing its excitonic nature.The first line is a sum of A and B excitons,the second one is the C exciton appearing due to disorientation of blocks forming the film.16Analogous tem-perature evolutions have been reported for a wide excitonic line in ZnO nanocrystals.15As the concentration of Mn impurity increases,the exci-tonic line additionally broadens and shifts to higher energies.Figure 3shows the actual Mn concentration shift of the ex-citonic line energy ប␻exc .It is seen that the increase in Mn concentration leads to not only changes in the excitonic spec-trum but also exhibits enhancement of the band-gap energy in Zn 1−x Mn x O films ͑band-gap magnitude can be estimated as E g =ប␻exc +E exc ,where E exc =60meV is the excitonic binding energy 13͒.It is known that the band-gap magnitude in ZnO-MnO system varies from 3.37eV in ZnO up to 3.8eV in MnO.22According to the theoretical analysis 8per-formed taking into account inversion of ⌫7and ⌫9valence subbands in ZnO,23,24strong coupling of manganese spin and p states of valence band leads to appearance of a positiveI n t e n s i t y (c o u n t )2θ(degree)FIG.1.XRD pattern of ZnO ͑left scale ͒and Zn 0.95Mn 0.05O ͑right scale ͒films.E n e r g y (eV)αdFIG.2.Exciton absorption spectra of compressed Zn 1−x Mn x O films:1—x =0%,2—x =1.8%,and 3—x =5%;film thickness:d =͑120–130͒nm;and T =300K.Inset shows excitonic absorption lines for compressed ZnO:1—T =300K and 4—T =77.3K.01234563.403.413.423.433.44E n e r g y (e V )X (%)FIG.3.Mn-concentration dependence of the excitonic line en-ergies for Zn 1−x Mn x O films.additive in optical absorption of Zn 1−x Mn x O at small x val-ues.The sum of two contributions at sufficiently small x results in an increase in E g magnitude.The rise of the band-gap magnitude with the admixture of the second component E g ͑x ͒has been observed in Zn 1−x Co x O ͑Ref.25͒for exci-tonic lines registered in the reflection spectra at 1.6K.The shift of the excitonic line to higher energies was observed in Zn 0.99Fe 0.01O,too.20In the case of weak d -p coupling the additive into the band gap change appeared to be negative.8In this case the band-gap value E g decreases with x for x Յ0.1,as it was found for Zn 1−x Mn x Se ͑Fig.6in Ref.14͒and for Cd 1−x Mn x S.26Therefore,the observed rise of the E g ͑x ͒value with Mn addition provides the reliable experimental proof that the strong hybridization condition U /U c Ͼ1in Zn 1−x Mn x O is fulfilled.Figure 4presents optical absorption in Zn 1−x Mn x O films recorded in the spectral region 3.1–3.3eV .It is seen that the onset of optical absorption in Zn 1−x Mn x O films emerges at lower energies than that for ZnO ones.Analogous shift had been observed earlier in the spectrum of the photoluminescence excitation over deep im-purity centers in Zn 1−x Mn x O for Ref.15.Unlike authors of Refs.11and 12,we assume that addi-tional absorption of Zn 1−x Mn x O ͑in comparison with ZnO ͒in the 3.1–3.3eV range is a result of pushing the Z-R-type states out of valence band to the forbidden gap.9The essence of this state consists of localization of the valence-band hole within the first coordination sphere on the oxygen ions as a result of strong exchange interaction of manganese and hole spins.Such electronic state is similar to the Z-R-type state originally considered for La 2CuO 4oxidesuperconductor.9This state is a singlet one,because in La 2CuO 4the spins of d 9configuration of Cu 2+ion and oxy-gen holes are equal but of opposite direction.The situation is more complex in the case of Zn 1−x Mn x O since the top of valence band is formed by three close subbands:⌫7,⌫9,and ⌫7.23,24In such case we have serious reasons to assume that not only the presence of one deep Z-R-type state is respon-sible for optical absorption in the 2.2–3.0eV spectral region.We assume the presence of another,relatively shallow Z-R-type state too,which has been split off into the gap providing additional absorption in the 3.1–3.3eV region of Zn 1−x Mn x O.Tentatively,using results 11,12,15we estimate the splitting of the second Z-R level from the valence band as 0.12–0.27eV .More reliable determination of the split energy can be performed using more sensitive methods of absorp-tion spectra, e.g.,modulation methods,which are in progress.IV .CONCLUSIONThin Zn 1−x Mn x O films ͑x =0–0.06͒have been sintered and their optical-absorption spectra were investigated.The well-pronounced excitonic absorption lines in the fundamen-tal absorption spectral regions were observed.Position of excitonic absorption lines in Zn 1−x Mn x O films shifts to higher energies with increasing Mn content.This evidences an increase in the E g magnitude with x for small values x and reliably corroborates fulfillment of the strong coupling crite-rion ͑U /U c Ͼ1͒in Zn 1−x Mn x O.The last effect leads to emer-gence of an intense optical-absorption band in the 2.2–3.0eV region due to the presence of the band-gap Z-R-type state.The additional absorption observed in the range of 3.1–3.3eV is interpreted as a result of splitting of one more Z-R-type states into the band gap.ACKNOWLEDGMENTSAuthors thank T.Dietl,V .I.Anisimov,and A.V .Lukoy-anov for useful discussions and V .Valvoda for kind assis-tance in XRD experiments.This work was supported by Czech Grants No.A V0Z10100522of A V CR,No.KJB100100703of GA A V ,No.202/09/J017of GA CR,No.KAN301370701of A V CR,and No.1M06002of MSMT CR and Russian Grants No.08-02-99080r-ofiof RFBR,PP RAS “Quantum Physics of Condensed Matter”,and State Contract No.5162.nger and H.J.Richter,Phys.Rev.146,554͑1966͒.2T.Hoshina and H.Kawai,Jpn.J.Appl.Phys.19,267͑1980͒.3F.W.Kleinlein and R.Helbig,Z.Phys.266,201͑1974͒.4R.Beaulac,P.I.Archer,and D.R.Gamelin,J.Solid State Chem.181,1582͑2008͒.5T.Fukumura,Z.Jin,A.Ohtomo,H.Koinuma,and M.Kawasaki,Appl.Phys.Lett.75,3366͑1999͒.6K.A.Kikoin and V .N.Fleurov,Transition Metal Impurities in Semiconductors:Electronic Structure and Physical Properties ͑World Scientific,Singapore,1994͒,p.349.7T.Dietl,J.Magn.Magn.Mater.272-276,1969͑2004͒.8T.Dietl,Phys.Rev.B 77,085208͑2008͒.9F.C.Zhang and T.M.Rice,Phys.Rev.B 37,3759͑1988͒.10T.Chanier,F.Virot,and R.Hayn,Phys.Rev.B 79,205204͑2009͒.11V .Shinde,T.Gujar,C.Lokhande,R.Mane,and S.-H.Han,3.1253.2500.00.40.8αdEnergy (eV)12FIG.4.Spectral dependence of the optical density ␣d in the 3.1–3.3eV spectral region for Zn 1−x Mn x O,1—ZnO;2—x =0.3–0.5%;film thickness 200–250nm;and T =300K.Mater.Chem.Phys.96,326͑2006͒.12Y.Guo,X.Cao,n,C.Zhao,X.Hue,and Y.Song,J.Phys. Chem.C112,8832͑2008͒.13Zh.L.Wang,J.Phys.:Condens.Matter16,R829͑2004͒.14R.B.Bylsma,W.M.Becker,J.Kossut,U.Debska,and D. Yoder-Short,Phys.Rev.B33,8207͑1986͒.15V.I.Sokolov,A.Ye.Yermakov,M.A.Uimin,A.A.Mysik,V.A.Pustovarov,M.V.Chukichev,and N.B.Gruzdev,J.Lumin.129,1771͑2009͒.16M.Chichina,Z.Hubichka,O.Churpita,and M.Tichy,Plasma Processes Polym.2,501͑2005͒.17Z.Hubicka,M.Cada,M.Sicha,A.Churpita,P.Pokorny,L. Soukup,and L.Jastrabík,Plasma Sources Sci.Technol.11,195͑2002͒.18http://www.xray.cz/priv/kuzel/dofplatan/19R.Kuzel,Jr.,R.Cerny,V.Valvoda,and M.Blomberg,ThinSolid Films247,64͑1994͒.20Z.Jin,T.Fukumura,M.Kaasaki,K.Ando,H.Saito,T.Skiguchi, Y.Z.Yoo,M.Murakami,Y.Matsumoto,T.Hasegawa,and H. Koinuma,Appl.Phys.Lett.78,3824͑2001͒.21J.-M.Chauveau,J.Vives,J.Zuniga-Perez,ügt,M.Teis-seire,C.Deparis,C.Morhain,and B.Vinter,Appl.Phys.Lett.93,231911͑2008͒.d and V.E.Henrich,Phys.Rev.B38,10860͑1988͒. 23K.Shindo,A.Morita,and H.Kamimura,J.Phys.Soc.Jpn.20, 2054͑1965͒.24W.Y.Liang and A.D.Yoffe,Phys.Rev.Lett.20,59͑1968͒. 25W.Pacuski,D.Ferrand,J.Gibert,C.Deparis,J.A.Gaj,P.Ko-ssacki,and C.Morhain,Phys.Rev.B73,035214͑2006͒.26M.Ikeda,K.Itoh,and H.Sato,J.Phys.Soc.Jpn.25,455͑1968͒.。

海洋测绘领域常用英语词汇

海洋测绘领域常用英语词汇

海洋测绘领域常用英语词汇001海洋测量marine survey002海洋大地测量marine geodetic survey003海底控制网submarine control network004岛陆联测island-mainland connection survey005海洋水准测量marine leveling006当地平均海面local mean sea level007日平均海面daily mean sea level008月平均海面monthly mean sea level009年平均海面yearly mean sea level010多年平均海面multi-year mean sea level011平均海面季节改正seasonal correction of mean sea level012海面地形sea surface topography013海洋测量定位marine survey positioning014光学[仪器]定位optical instrument positioning015卫星定位satellite positioning016无线电定位radio positioning017水声定位acoustic positioning018组合定位integrated positioning019圆一圆定位(又称“距离一距离定位”)range-range positioning 020双曲线定位(又称“测距差定位”)hyperbolic positioning021极坐标定位(又称“距离方位定位”)polar coordinate positioning 022差分法定位differentiation positioning023位置线line of position, LOP024位置线方程equation of LOP025位置[线交]角intersection angle of LOP026位置面surface of position,SOP027定位点间距positioning space028等角定位格网equiangular positioning grid029辐射线格网radial positioning grid030双曲线格网hyperbolic positioning grid031等距圆弧格网equilong circle arc grid032等精度[曲线]图equiaccuracy chart033岸台(又称“固定台”)base station034船台(又称“移动台”)mobile station035跟踪台track station036监测台(又称“检查台”)monitor station,check station037台链station chain038主台main station039副台slave station040相位周(又称“巷”)phase cycle,lane041相位周值(又称“巷宽”)phase cycle value,lane width042相位稳定性phase stability043相位多值性phase ambiguity044相位漂移phase drift045固定相移fixed phase drift046联测比对comparison survey047联测比对点point of comparison survey048接收中心receiving center (注:船台接收岸台发射的无线电信号的实际接收点,该点有时与天线位置不一致。

光子阻塞效应

光子阻塞效应

学号:201105774题目名称: 强耦合下的光子阻塞效应研究题目类型: 研究论文学生姓名: 董昌瑞院(系): 物理与光电工程学院专业班级: 物理11102班指导教师: 邹金花辅导教师: 邹金花时间: 2015年1月至2015年6月目录毕业论文任务书` (I)指导教师评审意见 (VIII)评阅教师评语 (IX)答辩记录及成绩评定 (X)中文摘要 (XI)外文摘要 (XII)1引言 (1)2 基础理论知识 (1)2.1 光力振子系统 (1)2.2二能级原子与光场相互作用的全量子理论 (2)2.3光场关联函数 (5)2.4 光子计数统计 (8)3 模型方程与结果分析 (10)3.1模型方程 (10)3.2 方程分析 (12)4总结与展望 (14)参考文献 (14)致谢 (16)毕业论文任务书`院(系)物理与光电工程学院专业物理班级物理11102 学生姓名董昌瑞指导教师/职称邹金花/副教授1.毕业论文(设计)题目:强耦合下的光子阻塞效应研究2.毕业论文(设计)起止时间: 2015 年1月1 日~2015 年 6月10 日3.毕业论文(设计)所需资料及原始数据(指导教师选定部分)[1] A Ridolfo, M Leib, S Savasta, M J Hartmann. Photon Blockade in the Ultrastrong CouplingRegime [J]. Phys. Rev. Lett., 2012, 109: 193602-1~193602-5[2] Jieqiao Liao, C K Law. Cooling of a mirror in cavity optomechanics with a chirped pulse [J]. Phys. Rev. A, 2011, 84: 053838-1~053838-6[3] P Komar, S D Bennett, K Stannigel, S J M Habraken, P Rabl, P Zoller, M D Lukin. Single-photon nonlinearities in two-mode optomechanics [J]. Phys. Rev. A, 2013, 87: 013839-1~013839-10[4] T Ramos, V Sudhir, K Stannigel, P Zoller, T Kippenbrg. Nonlinear quantum optomechanics viaindividual intrinsic two-level defects [J]. Phys. Rev. Lett., 2013, 110: 193602-1~193602-5 [5] G Anetsberger, O Arcizet, Q P Unterreithmeier, R Riviere, A Schliesser, E M Weig, J P Kotthaus,T Kippenberg. Near-field cavity optomechanics with nanomechanical oscillators [J]. Nat. Phys., 2009, 5: 909~914[6] S J M Habraken, W Lechner, P Zoller. Resonances in dissipative optomechanics withnanoparticles: Sorting, speed rectification, and transverse coolings [J]. Phys. Rev. A, 2013, 87: 053808-1~053808-8[7] K Qu, G S Agarwal. Fano resonances and their control in optomechanics [J]. Phys. Rev. A, 2013,87: 063813-1~063813-7[8] A Nunnenkamp, K Borkje, S M Girvin. Cooling in the single-photon strong-coupling regime ofcavity optomechanics [J]. Phys. Rev. A, 2012, 85: 051803-1~051803-4[9] Y C Liu, Y F Xiao, X S Luan, C W Wong. Dynamic Dissipative Cooling of a MechanicalResonator in Strong Coupling Optomechanics [J]. Phys. Rev. A, 2013, 110: 153606-1~153606-5[10] A Nunnekamp, K Borkie, S M Girvin. Single-photon optomechanics [J]. Phys. Rev. Lett., 2011,107: 063602-1~063602-5[11] J M Dobrindt, I Wilson-Rae, T J Kippenbeg. Parametric Normal-Mode Splitting in CavityOptomechanics [J]. Phys. Rev. Lett., 2008, 101: 263602-1~263602-4[12]樊菲菲. 光力振子与原子间量子纠缠和振子压缩的研究[D]. 华中师范大学,2014[13] 张文慧. 光机械腔系统的动力学行为[D]. 华中师范大学,2014[14]詹孝贵. 腔光机械系统中电磁诱导透明及其相关现象的理论研究[D]. 华中科技大学,20134.毕业论文(设计)应完成的主要内容在阅读大量文献的基础上,完成开题报告,并通过开题答辩。

耦合常数

耦合常数
• Through the analysis of an unknown compound, the geminal coupling constants can provide some idea about the size of the rings. In addition, the dynamic processes existing in the compound can be studied with the aid of the coupling constants.
• Imagine a benzene ring having more than one substituent. The number of isomers depends on the number of substituents. The exact location of these substituents can be easily determined by measuring the coupling constants between the protons, which are attached to the benzene ring.
• (4) n = 4. The number of bonds between the coupled protons is four. When the number of bonds between the coupled protons is greater than three, these coupUngs are called long-range couplings. Long-range couplings are observed in cyclic saturated compounds, in particular when the ring system is strained and has a bicyclic structure. Allylic coupling and meta coupling are also typical examples of long-range couplings through four bonds. Some examples of long-range couplings over four bonds are presented below.

仪器仪表常用英语词汇

仪器仪表常用英语词汇

仪器仪表常用英语词汇pH计pH meterX射线衍射仪X—ray diffractometerX射线荧光光谱仪X-ray fluorescence spectrometer力测量仪表force measuring instrument孔板orifice plate文丘里管venturi tube水表water meter加速度仪accelerometer可编程序控制器programmable controller平衡机balancing machine皮托管Pitot tube皮带秤belt weigher光线示波器light beam oscillograph光学高温计optical pyrometer光学显微镜optical microscope光谱仪器optical spectrum instrument吊车秤crane weigher地中衡platform weigher字符图形显示器character and graphic display位移测量仪表displacement measuring instrument巡迴检测装置data logger波纹管bellows长度测量工具dimensional measuring instrument长度传感器linear transducer厚度计thickness gauge差热分析仪differential thermal analyzer扇形磁场质谱计sector magnetic field mass spectrometer 料斗秤hopper weigher核磁共振波谱仪nuclear magnetic resonance spectrometer 气相色谱仪gas chromatograph浮球调节阀float adjusting valve真空计vacuum gauge动圈仪表moving—coil instrument基地式调节仪表local—mounted controller密度计densitometer液位计liquid level meter组装式仪表package system减压阀pressure reducing valve测功器dynamometer紫外和可见光分光光度计ultraviolet—visible spectrometer 顺序控制器sequence controller微处理器microprocessor温度调节仪表temperature controller煤气表gas meter节流阀throttle valve电子自动平衡仪表electronic self—balance instrument电子秤electronic weigher电子微探针electron microprobe电子显微镜electron microscope弹簧管bourdon tube数字式显示仪表digital display instrument热流计heat-flow meter热量计heat flux meter热电阻resistance temperature热电偶thermocouple膜片和膜盒diaphragm and diaphragm capsule调节阀regulating valve噪声计noise meter应变仪strain measuring instrument湿度计hygrometer声级计sound lever meter黏度计viscosimeter转矩测量仪表torque measuring instrument转速测量仪表tachometer露点仪dew—point meter变送器transmitter仪器仪表常用术语性能特性performance characteristic确定仪器仪表功能和能力的有关参数及其定量的表述.参比性能特性reference performance characteristic在参比工作条件下达到的性能特性.范围range由上、下限所限定的一个量的区间。

复杂网络的同步与控制

复杂网络的同步与控制
在比较具有相同动力学的网络的同步能力时提出最大横向lyapunov指数的区域为同步化区域c为复平面它是由孤立节点上的动力学函数耦合强度以及外耦合矩阵和内耦合矩阵函数确定的
Complex Network Synchronization and Topology
indentification 第5讲:复杂网络的动力学同步与控制
• Network Synchronization
Synchronization Theorem
• Let
0 1 2 N x1(t) x2(t) xN (t) s(t)
c2 d
be the eigenvalues of the coupling matrix A.
The synchronization state is exponentially stable,
N
xi f (xi ) aij (t)(t)x j , i 1, 2, , N j 1
如果A是常数矩阵,内联是自治的,则动力网络 是非时变的,否则是时变动力网络。
网络同步定义: 首先定义同步流形为线性子空间
M= x : xi xj ,i, j
如果当 t 时,x趋近于M,则称网络同 步. 即 对于所有的节点,在任意初始条件下
Chaos Communications
Francis C M Lau, Michael C K Tse, PolyU Centre for Chaos Control and Synchronization
Network Synchronization
同步是复杂网络的集体行为.
Synchronization Is one of the most Pervasive phenomena in the Universe

第四届冷原子会议会议安排July 5

第四届冷原子会议会议安排July 5
40
[P16]
Jing Qian(钱静)
Efficient production of polar molecular Bose–Einstein condensates via an all-optical R-type atom–molecule adiabatic passage
41
[P17]
31
[P07]
Haichao Zhang(张海潮)
Demonstration of Neutral Atom Guiding via Radio-Frequency Field
32
[P08]
Shuyu Zhou(周蜀渝)
Double-well Array Trapping Atoms Based on Binary Optics ethod
会议安排July 5, Monday
Opening Ceremony
Presider
Liang Liu(刘亮)
8:30-9:00
Yuzhu Wang(王育竹)and Chaohui Ye(叶朝辉)
Opening Remarks
Sec. A
Presider
Li You(尤力)
9:00-9:30
Jun Ye(叶军)
Xing-Dong Zhao(赵兴东)
A magical polarization orientation for canceling the dipole-dipole
interaction in ultracold Bosonic dipolar gases
42
[P18]
Cheng-ling Bian(边成玲)
46
[P22]
K. Zhang(张可烨)

Translation of Scientific and Technological Text

Translation of Scientific and Technological Text

The Study of Sociology (by Spencer 斯宾塞尔) 群学肄言 On Liberty (by John Mill 约翰﹒米勒)群已权界论 History of Politics ( by Jenks 甄克思)社会通诠 The Spirit of Laws (by Montesquieu孟德斯鸠)法意
凸透镜可以用来聚集太阳光,将一张纸片烧穿一个 洞。
(2)使用施事者作主语,转换成主动语态 The Ozone Hole often get confused in the popular press and by the general public with the problem of global warming. While there is a connection because ozone contributes to the greenhouse effect, the Ozone Hole is a separate issue. 媒体和大众经常把臭氧层空洞和全球变暖问题混为 一谈。尽管二者有联系,因为臭氧层会导致温室效 应,但臭氧层空洞却是另外一个问题。
(5)Much of the dry land of today was once covered with water. 今天的陆地曾有很大面积被水覆盖。 如果汉语的被动表达没有不幸的含义,可以 译为汉语的被动结构
3. E:多用名词化结构 C:多使用动词 The generation of heat by friction 摩擦生热 The standardization of the series 系列的标准化 You can rectify the fault if you insert a slash. Rectification of the fault can be achieved by inserting a slash. We can normally regulate the temperature by using an air conditioner. Normal regulation of the temperature can be achieved by the application of an airconditioner.

近藤效应

近藤效应

Tunable Kondo effect in a single donor atomnsbergen 1,G.C.Tettamanzi 1,J.Verduijn 1,N.Collaert 2,S.Biesemans 2,M.Blaauboer 1,and S.Rogge 11Kavli Institute of Nanoscience,Delft University of Technology,Lorentzweg 1,2628CJ Delft,The Netherlands and2InterUniversity Microelectronics Center (IMEC),Kapeldreef 75,3001Leuven,Belgium(Dated:September 30,2009)The Kondo effect has been observed in a single gate-tunable atom.The measurement device consists of a single As dopant incorporated in a Silicon nanostructure.The atomic orbitals of the dopant are tunable by the gate electric field.When they are tuned such that the ground state of the atomic system becomes a (nearly)degenerate superposition of two of the Silicon valleys,an exotic and hitherto unobserved valley Kondo effect appears.Together with the “regular”spin Kondo,the tunable valley Kondo effect allows for reversible electrical control over the symmetry of the Kondo ground state from an SU(2)-to an SU(4)-configuration.The addition of magnetic impurities to a metal leads to an anomalous increase of their resistance at low tem-perature.Although discovered in the 1930’s,it took until the 1960’s before this observation was satisfactorily ex-plained in the context of exchange interaction between the localized spin of the magnetic impurity and the de-localized conduction electrons in the metal [1].This so-called Kondo effect is now one of the most widely stud-ied phenomena in condensed-matter physics [2]and plays a mayor role in the field of nanotechnology.Kondo ef-fects on single atoms have first been observed by STM-spectroscopy and were later discovered in a variety of mesoscopic devices ranging from quantum dots and car-bon nanotubes to single molecules [3].Kondo effects,however,do not only arise from local-ized spins:in principle,the role of the electron spin can be replaced by another degree of freedom,for example or-bital momentum [4].The simultaneous presence of both a spin-and an orbital degeneracy gives rise to an exotic SU(4)-Kondo effect,where ”SU(4)”refers to the sym-metry of the corresponding Kondo ground state [5,6].SU(4)Kondo effects have received quite a lot of theoret-ical attention [6,7],but so far little experimental work exists [8].The atomic orbitals of a gated donor in Si consist of linear combinations of the sixfold degenerate valleys of the Si conduction band.The orbital-(or more specifi-cally valley)-degeneracy of the atomic ground state is tunable by the gate electric field.The valley splitting ranges from ∼1meV at high fields (where the electron is pulled towards the gate interface)to being equal to the donors valley-orbit splitting (∼10-20meV)at low fields [9,10].This tunability essentially originates from a gate-induced quantum confinement transition [10],namely from Coulombic confinement at the donor site to 2D-confinement at the gate interface.In this article we study Kondo effects on a novel exper-imental system,a single donor atom in a Silicon nano-MOSFET.The charge state of this single dopant can be tuned by the gate electrode such that a single electron (spin)is localized on the pared to quantum dots (or artificial atoms)in Silicon [11,12,13],gated dopants have a large charging energy compared to the level spac-ing due to their typically much smaller size.As a result,the orbital degree of freedom of the atom starts to play an important role in the Kondo interaction.As we will argue in this article,at high gate field,where a (near)de-generacy is created,the valley index forms a good quan-tum number and Valley Kondo [14]effects,which have not been observed before,appear.Moreover,the Valley Kondo resonance in a gated donor can be switched on and offby the gate electrode,which provides for an electri-cally controllable quantum phase transition [15]between the regular SU(2)spin-and the SU(4)-Kondo ground states.In our experiment we use wrap-around gate (FinFET)devices,see Fig.1(a),with a single Arsenic donor in the channel dominating the sub-threshold transport charac-teristics [16].Several recent experiments have shown that the fingerprint of a single dopant can be identified in low-temperature transport through small CMOS devices [16,17,18].We perform transport spectroscopy (at 4K)on a large ensemble of FinFET devices and select the few that show this fingerprint,which essentially consists of a pair of characteristic transport resonances associ-ated with the one-electron (D 0)-and two-electron (D −)-charge states of the single donor [16].From previous research we know that the valley splitting in our Fin-FET devices is typically on the order of a few meV’s.In this Report,we present several such devices that are in addition characterized by strong tunnel coupling to the source/drain contacts which allows for sufficient ex-change processes between the metallic contacts and the atom to observe Kondo effects.Fig.1b shows a zero bias differential conductance (dI SD /dV SD )trace at 4.2K as a function of gate volt-age (V G )of one of the strongly coupled FinFETs (J17).At the V G such that a donor level in the barrier is aligned with the Fermi energy in the source-drain con-tacts (E F ),electrons can tunnel via the level from source to drain (and vice versa)and we observe an increase in the dI SD /dV SD .The conductance peaks indicated bya r X i v :0909.5602v 1 [c o n d -m a t .m e s -h a l l ] 30 S e p 2009FIG.1:Coulomb blocked transport through a single donor in FinFET devices(a)Colored Scanning Electron Micrograph of a typical FinFET device.(b)Differential conductance (dI SD/dV SD)versus gate voltage at V SD=0.(D0)and(D−) indicate respectively the transport resonances of the one-and two-electron state of a single As donor located in the Fin-FET channel.Inset:Band diagram of the FinFET along the x-axis,with the(D0)charge state on resonance.(c)and(d) Colormap of the differential conductance(dI SD/dV SD)as a function of V SD and V G of samples J17and H64.The red dots indicate the(D0)resonances and data were taken at1.6 K.All the features inside the Coulomb diamonds are due to second-order chargefluctuations(see text).(D0)and(D−)are the transport resonances via the one-electron and two-electron charge states respectively.At high gate voltages(V G>450mV),the conduction band in the channel is pushed below E F and the FET channel starts to open.The D−resonance has a peculiar double peak shape which we attribute to capacitive coupling of the D−state to surrounding As atoms[19].The current between the D0and the D−charge state is suppressed by Coulomb blockade.The dI SD/dV SD around the(D0)and(D−)resonances of sample J17and sample H64are depicted in Fig.1c and Fig.1d respectively.The red dots indicate the po-sitions of the(D0)resonance and the solid black lines crossing the red dots mark the outline of its conducting region.Sample J17shows afirst excited state at inside the conducting region(+/-2mV),indicated by a solid black line,associated with the valley splitting(∆=2 mV)of the ground state[10].The black dashed lines indicate V SD=0.Inside the Coulomb diamond there is one electron localized on the single As donor and all the observable transport in this regionfinds its origin in second-order exchange processes,i.e.transport via a vir-tual state of the As atom.Sample J17exhibits three clear resonances(indicated by the dashed and dashed-dotted black lines)starting from the(D0)conducting region and running through the Coulomb diamond at-2,0and2mV. The-2mV and2mV resonances are due to a second or-der transition where an electron from the source enters one valley state,an the donor-bound electron leaves from another valley state(see Fig.2(b)).The zero bias reso-nance,however,is typically associated with spin Kondo effects,which happen within the same valley state.In sample H64,the pattern of the resonances looks much more complicated.We observe a resonance around0mV and(interrupted)resonances that shift in V SD as a func-tion of V G,indicating a gradual change of the internal level spectrum as a function of V G.We see a large in-crease in conductance where one of the resonances crosses V SD=0(at V G∼445mV,indicated by the red dashed elipsoid).Here the ground state has a full valley degen-eracy,as we will show in thefinal paragraph.There is a similar feature in sample J17at V G∼414mV in Fig.1c (see also the red cross in Fig.1b),although that is prob-ably related to a nearby defect.Because of the relative simplicity of its differential conductance pattern,we will mainly use data obtained from sample J17.In order to investigate the behavior at the degeneracy point of two valley states we use sample H64.In the following paragraphs we investigate the second-order transport in more detail,in particular its temper-ature dependence,fine-structure,magneticfield depen-dence and dependence on∆.We start by analyzing the temperature(T)dependence of sample J17.Fig.2a shows dI SD/dV SD as a function of V SD inside the Coulomb diamond(at V G=395mV) for a range of temperatures.As can be readily observed from Fig.2a,both the zero bias resonance and the two resonances at V SD=+/-∆mV are suppressed with increasing T.The inset of Fig.2a shows the maxima (dI/dV)MAX of the-2mV and0mV resonances as a function of T.We observe a logarithmic dependence on T(a hallmark sign of Kondo correlations)at both resonances,as indicated by the red line.To investigate this point further we analyze another sample(H67)which has sharper resonances and of which more temperature-dependent data were obtained,see Fig.2c.This sample also exhibits the three resonances,now at∼-1,0and +1mV,and the same strong suppression by tempera-ture.A linear background was removed for clarity.We extracted the(dI/dV)MAX of all three resonances forFIG.2:Electrical transport through a single donor atom in the Coulomb blocked region(a)Differential conductance of sample J17as a function of V SD in the Kondo regime(at V G=395mV).For clarity,the temperature traces have been offset by50nS with respect to each other.Both the resonances with-and without valley-stateflip scale similarly with increasing temperature. Inset:Conductance maxima of the resonances at V SD=-2mV and0mV as a function of temperature.(b)Schematic depiction of three(out of several)second-order processes underlying the zero bias and±∆resonances.(c)Differential conductance of sample H67as a function of V SD in the Kondo regime between0.3K and6K.A linear(and temperature independent) background on the order of1µS was removed and the traces have been offset by90nS with respect to each other for clarity.(d)The conductance maxima of the three resonances of(c)normalized to their0.3K value.The red line is afit of the data by Eq.1.all temperatures and normalized them to their respective(dI/dV)MAX at300mK.The result is plotted in Fig.2d.We again observe that all three peaks have the same(log-arithmic)dependence on temperature.This dependenceis described well by the following phenomenological rela-tionship[20](dI SD/dV SD)max (T)=(dI SD/dV SD)T 2KT2+TKs+g0(1)where TK =T K/√21/s−1,(dI SD/dV SD)is the zero-temperature conductance,s is a constant equal to0.22 [21]and g0is a constant.Here T K is the Kondo tem-perature.The red curve in Fig.2d is afit of Eq.(1)to the data.We readily observe that the datafit well and extract a T K of2.7K.The temperature scaling demon-strates that both the no valley-stateflip resonance at zero bias voltage and the valley-stateflip-resonance atfinite bias are due to Kondo-type processes.Although a few examples offinite-bias Kondo have been reported[15,22,23],the corresponding resonances (such as our±∆resonances)are typically associated with in-elastic cotunneling.Afinite bias between the leads breaks the coherence due to dissipative transitions in which electrons are transmitted from the high-potential-lead to the low-potential lead[24].These dissipative4transitions limit the lifetime of the Kondo-type processes and,if strong enough,would only allow for in-elastic events.In the supporting online text we estimate the Kondo lifetime in our system and show it is large enough to sustain thefinite-bias Kondo effects.The Kondo nature of the+/-∆mV resonances points strongly towards a Valley Kondo effect[14],where co-herent(second-order)exchange between the delocalized electrons in the contacts and the localized electron on the dopant forms a many-body singlet state that screens the valley index.Together with the more familiar spin Kondo effect,where a many-body state screens the spin index, this leads to an SU(4)-Kondo effect,where the spin and charge degree of freedom are fully entangled[8].The ob-served scaling of the+/-∆-and zero bias-resonances in our samples by a single T K is an indication that such a fourfold degenerate SU(4)-Kondo ground state has been formed.To investigate the Kondo nature of the transport fur-ther,we analyze the substructure of the resonances of sample J17,see Fig.2a.The central resonance and the V SD=-2mV each consist of three separate peaks.A sim-ilar substructure can be observed in sample H67,albeit less clear(see Fig.2c).The substructure can be explained in the context of SU(4)-Kondo in combination with a small difference between the coupling of the ground state (ΓGS)-and thefirst excited state(ΓE1)-to the leads.It has been theoretically predicted that even a small asym-metry(ϕ≡ΓE1/ΓGS∼=1)splits the Valley Kondo den-sity of states into an SU(2)-and an SU(4)-part[25].Thiswill cause both the valley-stateflip-and the no valley-stateflip resonances to split in three,where the middle peak is the SU(2)-part and the side-peaks are the SU(4)-parts.A more detailed description of the substructure can be found in the supporting online text.The split-ting between middle and side-peaks should be roughly on the order of T K[25].The measured splitting between the SU(2)-and SU(4)-parts equals about0.5meV for sample J17and0.25meV for sample H67,which thus corresponds to T K∼=6K and T K∼=3K respectively,for the latter in line with the Kondo temperature obtained from the temperature dependence.We further note that dI SD/dV SD is smaller than what we would expect for the Kondo conductance at T<T K.However,the only other study of the Kondo effect in Silicon where T K could be determined showed a similar magnitude of the Kondo signal[12].The presence of this substructure in both the valley-stateflip-,and the no valley-stateflip-Kondo resonance thus also points at a Valley Kondo effect.As a third step,we turn our attention to the magnetic field(B)dependence of the resonances.Fig.3shows a colormap plot of dI SD/dV SD for samples J17and H64 both as a function of V SD and B at300mK.The traces were again taken within the Coulomb diamond.Atfinite magneticfield,the central Kondo resonances of both de-vices split in two with a splitting of2.2-2.4mV at B=FIG.3:Colormap plot of the conductance as a function of V SD and B of sample J17at V G=395mV(a)and H64at V G=464mV(b).The central Kondo resonances split in two lines which are separated by2g∗µB B.The resonances with a valley-stateflip do not seem to split in magneticfield,a feature we associate with the different decay-time of parallel and anti-parallel spin-configurations of the doubly-occupied virtual state(see text).10T.From theoretical considerations we expect the cen-tral Valley Kondo resonance to split in two by∆B= 2g∗µB B if there is no mixing of valley index(this typical 2g∗µB B-splitting of the resonances is one of the hall-marks of the Kondo effect[24]),and to split in three (each separated by g∗µB B)if there is a certain degree of valley index mixing[14].Here,g∗is the g-factor(1.998 for As in Si)andµB is the Bohr magneton.In the case of full mixing of valley index,the valley Kondo effect is expected to vanish and only spin Kondo will remain [25].By comparing our measured magneticfield splitting (∆B)with2g∗µB B,wefind a g-factor between2.1and 2.4for all three devices.This is comparable to the result of Klein et al.who found a g-factor for electrons in SiGe quantum dots in the Kondo regime of around2.2-2.3[13]. The magneticfield dependence of the central resonance5indicates that there is no significant mixing of valley in-dex.This is an important observation as the occurrence of Valley Kondo in Si depends on the absence of mix-ing(and thus the valley index being a good quantum number in the process).The conservation of valley in-dex can be attributed to the symmetry of our system. The large2D-confinement provided by the electricfield gives strong reason to believe that the ground-andfirst excited-states,E GS and E1,consist of(linear combi-nations of)the k=(0,0,±kz)valleys(with z in the electricfield direction)[10,26].As momentum perpen-dicular to the tunneling direction(k x,see Fig.1)is con-served,also valley index is conserved in tunneling[27]. The k=(0,0,±k z)-nature of E GS and E1should be as-sociated with the absence of significant exchange interac-tion between the two states which puts them in the non-interacting limit,and thus not in the correlated Heitler-London limit where singlets and triplets are formed.We further observe that the Valley Kondo resonances with a valley-stateflip do not split in magneticfield,see Fig.3.This behavior is seen in both samples,as indicated by the black straight solid lines,and is most easily ob-served in sample J17.These valley-stateflip resonances are associated with different processes based on their evo-lution with magneticfield.The processes which involve both a valleyflip and a spinflip are expected to shift to energies±∆±g∗µB B,while those without a spin-flip stay at energies±∆[14,25].We only seem to observe the resonances at±∆,i.e.the valley-stateflip resonances without spinflip.In Ref[8],the processes with both an orbital and a spinflip also could not be observed.The authors attribute this to the broadening of the orbital-flip resonances.Here,we attribute the absence of the processes with spinflip to the difference in life-time be-tween the virtual valley state where two spins in seperate valleys are parallel(τ↑↑)and the virtual state where two spins in seperate valleys are anti-parallel(τ↑↓).In con-trast to the latter,in the parallel spin configuration the electron occupying the valley state with energy E1,can-not decay to the other valley state at E GS due to Pauli spin blockade.It wouldfirst needs toflip its spin[28].We have estimatedτ↑↑andτ↑↓in our system(see supporting online text)andfind thatτ↑↑>>h/k b T K>τ↑↓,where h/k b T K is the characteristic time-scale of the Kondo pro-cesses.Thus,the antiparallel spin configuration will have relaxed before it has a change to build up a Kondo res-onance.Based on these lifetimes,we do not expect to observe the Kondo resonances associated with both an valley-state-and a spin-flip.Finally,we investigate the degeneracy point of valley states in the Coulomb diamond of sample H64.This degeneracy point is indicated in Fig.1d by the red dashed ellipsoid.By means of the gate electrode,we can tune our system onto-or offthis degeneracy point.The gate-tunability in this sample is created by a reconfiguration of the level spectrum between the D0and D−-charge states,FIG.4:Colormap plot of I SD at V SD=0as a function of V G and B.For increasing B,a conductance peak develops around V G∼450mV at the valley degeneracy point(∆= 0),indicated by the dashed black line.Inset:Magneticfield dependence of the valley degeneracy point.The resonance is fixed at zero bias and its magnitude does not depend on the magneticfield.probably due to Coulomb interactions in the D−-states. Figure4shows a colormap plot of I SD at V SD=0as a function of V G and B(at0.3K).Note that we are thus looking at the current associated with the central Kondo resonance.At B=0,we observe an increasing I SD for higher V G as the atom’s D−-level is pushed toward E F. As B is increased,the central Kondo resonance splits and moves away from V SD=0,see Fig.3.This leads to a general decrease in I SD.However,at around V G= 450mV a peak in I SD develops,indicated by the dashed black line.The applied B-field splits offthe resonances with spin-flip,but it is the valley Kondo resonance here that stays at zero bias voltage giving rise to the local current peak.The inset of Fig.4shows the single Kondo resonance in dI SD/dV SD as a function of V SD and B.We observe that the magnitude of the resonance does not decrease significantly with magneticfield in contrast to the situation at∆=0(Fig.3b).This insensitivity of the Kondo effect to magneticfield which occurs only at∆= 0indicates the profound role of valley Kondo processes in our structure.It is noteworthy to mention that at this specific combination of V SD and V G the device can potentially work as a spin-filter[6].We acknowledge fruitful discussions with Yu.V. Nazarov,R.Joynt and S.Shiau.This project is sup-ported by the Dutch Foundation for Fundamental Re-search on Matter(FOM).6[1]Kondo,J.,Resistance Minimum in Dilute Magnetic Al-loys,Prog.Theor.Phys.3237-49(1964)[2]Hewson,A.C.,The Kondo Problem to Heavy Fermions(Cambridge Univ.Press,Cambridge,1993).[3]Wingreen N.S.,The Kondo effect in novel systems,Mat.Science Eng.B842225(2001)and references therein.[4]Cox,D.L.,Zawadowski,A.,Exotic Kondo effects in met-als:magnetic ions in a crystalline electricfield and tun-neling centers,Adv.Phys.47,599-942(1998)[5]Inoshita,T.,Shimizu, A.,Kuramoto,Y.,Sakaki,H.,Correlated electron transport through a quantum dot: the multiple-level effect.Phys.Rev.B48,14725-14728 (1993)[6]Borda,L.Zar´a nd,G.,Hofstetter,W.,Halperin,B.I.andvon Delft,J.,SU(4)Fermi Liquid State and Spin Filter-ing in a Double Quantum Dot System,Phys.Rev.Lett.90,026602(2003)[7]Zar´a nd,G.,Orbitalfluctuations and strong correlationsin quantum dots,Philosophical Magazine,86,2043-2072 (2006)[8]Jarillo-Herrero,P.,Kong,J.,van der Zant H.S.J.,Dekker,C.,Kouwenhoven,L.P.,De Franceschi,S.,Or-bital Kondo effect in carbon nanotubes,Nature434,484 (2005)[9]Martins,A.S.,Capaz,R.B.and Koiller,B.,Electric-fieldcontrol and adiabatic evolution of shallow donor impuri-ties in silicon,Phys.Rev.B69,085320(2004)[10]Lansbergen,G.P.et al.,Gate induced quantum confine-ment transition of a single dopant atom in a Si FinFET, Nature Physics4,656(2008)[11]Rokhinson,L.P.,Guo,L.J.,Chou,S.Y.,Tsui, D.C.,Kondo-like zero-bias anomaly in electronic transport through an ultrasmall Si quantum dot,Phys.Rev.B60, R16319-R16321(1999)[12]Specht,M.,Sanquer,M.,Deleonibus,S.,Gullegan G.,Signature of Kondo effect in silicon quantum dots,Eur.Phys.J.B26,503-508(2002)[13]Klein,L.J.,Savage, D.E.,Eriksson,M.A.,Coulombblockade and Kondo effect in a few-electron silicon/silicon-germanium quantum dot,Appl.Phys.Lett.90,033103(2007)[14]Shiau,S.,Chutia,S.and Joynt,R.,Valley Kondo effectin silicon quantum dots,Phys.Rev.B75,195345(2007) [15]Roch,N.,Florens,S.,Bouchiat,V.,Wernsdirfer,W.,Balestro, F.,Quantum phase transistion in a single molecule quantum dot,Nature453,633(2008)[16]Sellier,H.et al.,Transport Spectroscopy of a SingleDopant in a Gated Silicon Nanowire,Phys.Rev.Lett.97,206805(2006)[17]Calvet,L.E.,Wheeler,R.G.and Reed,M.A.,Observa-tion of the Linear Stark Effect in a Single Acceptor in Si, Phys.Rev.Lett.98,096805(2007)[18]Hofheinz,M.et al.,Individual charge traps in siliconnanowires,Eur.Phys.J.B54,299307(2006)[19]Pierre,M.,Hofheinz,M.,Jehl,X.,Sanquer,M.,Molas,G.,Vinet,M.,Deleonibus S.,Offset charges acting as ex-cited states in quantum dots spectroscopy,Eur.Phys.J.B70,475-481(2009)[20]Goldhaber-Gordon,D.,Gres,J.,Kastner,M.A.,Shtrik-man,H.,Mahalu, D.,Meirav,U.,From the Kondo Regime to the Mixed-Valence Regime in a Single-Electron Transistor,Phys.Rev.Lett.81,5225(1998) [21]Although the value of s=0.22stems from SU(2)spinKondo processes,it is valid for SU(4)-Kondo systems as well[8,25].[22]Paaske,J.,Rosch,A.,W¨o lfle,P.,Mason,N.,Marcus,C.M.,Nyg˙ard,Non-equilibrium singlet-triplet Kondo ef-fect in carbon nanotubes,Nature Physics2,460(2006) [23]Osorio, E.A.et al.,Electronic Excitations of a SingleMolecule Contacted in a Three-Terminal Configuration, Nanoletters7,3336-3342(2007)[24]Meir,Y.,Wingreen,N.S.,Lee,P.A.,Low-TemperatureTransport Through a Quantum Dot:The Anderson Model Out of Equilibrium,Phys.Rev.Lett.70,2601 (1993)[25]Lim,J.S.,Choi,M-S,Choi,M.Y.,L´o pez,R.,Aguado,R.,Kondo effects in carbon nanotubes:From SU(4)to SU(2)symmetry,Phys.Rev.B74,205119(2006) [26]Hada,Y.,Eto,M.,Electronic states in silicon quan-tum dots:Multivalley artificial atoms,Phys.Rev.B68, 155322(2003)[27]Eto,M.,Hada,Y.,Kondo Effect in Silicon QuantumDots with Valley Degeneracy,AIP Conf.Proc.850,1382-1383(2006)[28]A comparable process in the direct transport throughSi/SiGe double dots(Lifetime Enhanced Transport)has been recently proposed[29].[29]Shaji,N.et.al.,Spin blockade and lifetime-enhancedtransport in a few-electron Si/SiGe double quantum dot, Nature Physics4,540(2008)7Supporting InformationFinFET DevicesThe FinFETs used in this study consist of a silicon nanowire connected to large contacts etched in a60nm layer of p-type Silicon On Insulator.The wire is covered with a nitrided oxide(1.4nm equivalent SiO2thickness) and a narrow poly-crystalline silicon wire is deposited perpendicularly on top to form a gate on three faces.Ion implantation over the entire surface forms n-type degen-erate source,drain,and gate electrodes while the channel protected by the gate remains p-type,see Fig.1a of the main article.The conventional operation of this n-p-n field effect transistor is to apply a positive gate voltage to create an inversion in the channel and allow a current toflow.Unintentionally,there are As donors present be-low the Si/SiO2interface that show up in the transport characteristics[1].Relation between∆and T KThe information obtained on T K in the main article allows us to investigate the relation between the splitting (∆)of the ground(E GS)-andfirst excited(E1)-state and T K.It is expected that T K decreases as∆increases, since a high∆freezes out valley-statefluctuations.The relationship between T K of an SU(4)system and∆was calculated by Eto[2]in a poor mans scaling approach ask B T K(∆) B K =k B T K(∆=0)ϕ(2)whereϕ=ΓE1/ΓGS,withΓE1andΓGS the lifetimes of E1and E GS respectively.Due to the small∆com-pared to the barrier height between the atom and the source/drain contact,we expectϕ∼1.Together with ∆=1meV and T K∼2.7K(for sample H67)and∆=2meV and T K∼6K(for sample J17),Eq.2yields k B T K(∆)/k B T K(∆=0)=0.4and k B T K(∆)/k B T K(∆= 0)=0.3respectively.We can thus conclude that the rela-tively high∆,which separates E GS and E1well in energy, will certainly quench valley-statefluctuations to a certain degree but is not expected to reduce T K to a level that Valley effects become obscured.Valley Kondo density of statesHere,we explain in some more detail the relation be-tween the density of states induced by the Kondo effects and the resulting current.The Kondo density of states (DOS)has three main peaks,see Fig.1a.A central peak at E F=0due to processes without valley-stateflip and two peaks at E F=±∆due to processes with valley-state flip,as explained in the main text.Even a small asym-metry(ϕclose to1)will split the Valley Kondo DOS into an SU(2)-and an SU(4)-part[3],indicated in Fig1b in black and red respectively.The SU(2)-part is positioned at E F=0or E F=±∆,while the SU(4)-part will be shifted to slightly higher positive energy(on the order of T K).A voltage bias applied between the source and FIG.1:(a)dI SD/dV SD as a function of V SD in the Kondo regime(at395mV G)of sample J17.The substructure in the Kondo resonances is the result of a small difference between ΓE1andΓGS.This splits the peaks into a(central)SU(2)-part (black arrows)and two SU(4)-peaks(red arrows).(b)Density of states in the channel as a result ofϕ(=ΓE1/ΓGS)<1and applied V SD.drain leads results in the Kondo peaks to split,leaving a copy of the original structure in the DOS now at the E F of each lead,which is schematically indicated in Fig.1b by a separate DOS associated with each contact.The current density depends directly on the density of states present within the bias window defined by source/drain (indicated by the gray area in Fig1b)[4].The splitting between SU(2)-and SU(4)-processes will thus lead to a three-peak structure as a function of V SD.Figure.1a has a few more noteworthy features.The zero-bias resonance is not positioned exactly at V SD=0, as can also be observed in the transport data(Fig1c of the main article)where it is a few hundredµeV above the Fermi energy near the D0charge state and a few hundredµeV below the Fermi energy near the D−charge state.This feature is also known to arise in the Kondo strong coupling limit[5,6].We further observe that the resonances at V SD=+/-2mV differ substantially in magnitude.This asymmetry between the two side-peaks can actually be expected from SU(4)Kondo sys-tems where∆is of the same order as(but of course al-ways smaller than)the energy spacing between E GS and。

车辆强电磁脉冲条件下的分层防护及验证方法探讨

车辆强电磁脉冲条件下的分层防护及验证方法探讨

车辆强电磁脉冲条件下的分层防护及验证方法探讨聂秀丽;赵晓凡【摘要】目的提高地面整车装备在强电磁脉冲环境中的生存能力,研究高场强条件下的分层电磁防护技术.方法研究强电磁脉冲干扰的车辆耦合途径,在综合考虑车辆生存能力、功能任务、费效比等因素的前提下,探讨从元器件级、设备分系统级、整车级进行电磁防护的方法,并提出验证方法.结果提出了基于分层的电磁防护措施,探讨了外部射频电磁环境适应性测试和电缆束瞬态传导敏感度测试等验证方法.结论要提高地面整车装备在强电磁脉冲环境中的生存能力,应当继续研究强干扰条件下的分层电磁防护技术,并通过整车试验进行防护效能验证.%Objective Improve the ground equipment in strong electromagnetic pulse of the environment of survival ability, the high field strength under the condition of stratified electromagnetic protection technology.Methods The vehicle coupling way to the strong electromagnetic pulse interference, in consideration of vehicle survivability, functional task, under the premise of factors such as cost effectiveness, discussed from levels of components, equipment subsystem, the vehicle level method for electromagnetic shielding, and validation method is put forward.Results Is proposed based on hierarchical electromagnetic protection measures, this paper discusses the external electromagnetic environment adaptability test and the cable of the radio beam transient conduction sensitivity test validation method,etc.Conclusion To improve the ground equipment in strong elec-tromagnetic pulse of the environment of survival ability, should continue to study under the condition of strong interference hi-erarchicalelectromagnetic protection technology, and through the vehicle test verifies the protective effectiveness..【期刊名称】《装备环境工程》【年(卷),期】2017(014)004【总页数】6页(P36-41)【关键词】强脉冲干扰;耦合;电磁防护;整车验证【作者】聂秀丽;赵晓凡【作者单位】中国北方车辆研究所,北京 100072;中国北方车辆研究所,北京100072【正文语种】中文【中图分类】TJ811未来战争是信息化条件下的局部高科技战争,相当多信息装备的战技指标都是通过大功率辐射来实现的。

一种采用双pid串级控制的双轮自平衡车的研制

一种采用双pid串级控制的双轮自平衡车的研制

摘 要一种采用双PID串级控制的双轮自平衡车的研制双轮自平衡车因其动力学系统同时具有多变量,非线性,不稳定,强耦合等特性,在研究各种控制方法等方面是较为领先的领域,所以双轮自平衡车的发展引起了人们广泛的关注。

双轮自平衡车可以用倒立摆模型进行分析,因其系统极其不稳定,务必要用强效巧妙的控制方法才能维持其稳定。

系统整体上主要由姿态传感子系统、CPU处理子系统、驱动子系统三部分构建而成,其中获取精确的姿态信息以及将获得数据进行融合和处理的算法决定了自平衡车的优劣。

其原理是自平衡车通过姿态传感器(MPU6050)高频率实时检测运行情况,将所采集的俯仰角和角度及加速度变化率传输给CPU,经由CPU融合处理并输出调整姿态的指令,从而驱动电动机使两个轮的转速发生相应的改变,实现车体平衡以及加速和减速的目的。

本文研制了一种采用双PID串级控制的双轮自平衡车,系统以STM32最小系统为核心板,采用运动处理传感器MPU6050实时检测角速度以及角度,并通过互补滤波的方式进行数据融合,用于减小传感信号温度漂移的影响,同时使自平衡车即使受到很大的外界干扰(如推拉、震动、颠簸等)也能够快速进行调整。

系统通过串级PID(Proportion Integration Differentiation)算法进行车体的控制,通过PD(Proportion Differentiation)控制使得车身能够直立运行,通过安装在直流电机上的测速码盘实时反馈电机转速和方向,并通过PI(Proportion Integration)控制来控制车身的速度。

该双轮自平衡车运用TB6612FNG电机驱动系统,调节PWM输出的占空比来改变电机的转速。

系统通过LM2940以及ASM1117子系统作为电源驱动,准确的转换电压并对STM32和电机供电。

最后对系统进行控制参数的调整和优化,最终实现让双轮自平衡车直立平衡运行的目标。

关键词:双轮平衡车,PID控制,互补滤波,姿态检测ABSTRACTDeveloping of a dual-wheel self-balancing vehicle using double PID cascade controlThe dual-wheeled self-balancing vehicle is a leading field in the research of various control methods because of its dynamic system of multi-variable, nonlinear, unstable and strong coupling, so the development of self-balancing two-wheeled vehicles has attracted widespread attention.The dual-wheel self-balancing vehicle can be analyzed by using inverted pendulum model. The system is extremely unstable, so it is important to use a effective method to maintain its stability. The system is mainly composed of three parts: attitude sensing subsystem, CPU processing subsystem and driving subsystem. The accurate attitude information and the algorithm which gets the data to be fused and processed determine the performance of self-balancing vehicle. The self-balancing vehicle detects operating conditions through the real-time high-frequency sensor (MPU6050), the collected pitch angle and acceleration rate of change is transmitted to the CPU, CPU fusion processing and output adjustment attitude commands, which drive the motor to make two wheels' speed change to achieve the purpose of acceleration, deceleration and balancing the body.In this paper, a dual-wheel self-balancing vehicle using double PID cascade control is developed. Using STM32 as the cord board and motion detection sensor(MPU6050)detects angular velocity and angle in real time. And performing data fusion by complement filter to reduce the influence of the temperature drift of the sensing signal. At the same time, even if the self-balancing vehicle suffers from great external interference (Push and pull, vibration, bump, etc.) can also be quickly adjusted. The system controls the vehicle body through the Proportion Integration Differentiation (PID) algorithm. By the control of PD (Proportion Differentiation), the vehicle body can be erected. The speed and direction of the motor are fed back in real time by the speed encoder installed on the DC motor. And using the control of Proportion Integration(PI) to control the body speed. The TB6612FNG driving system of motor is used in the self-balancing dual-wheel vehicle, and the motor speed is changed by adjusting the PWM output duty cycle. The system is powered by the LM2940 and the ASM1117 subsystem, which can convert voltage accurately, power theSTM32 and the motor. Finally, two-wheeled self-balancing vehicle upright balance operation is achieved by adjusting and optimizing the control parameters.Keywords:a auto-balancing vehicle with two wheels, PID control, Complementary filter, attitude detection目 录摘 要 (I)ABSTRACT (II)第一章 绪论 (1)1.1研究背景及意义 (1)1.2国内外研究现状 (1)1.2.1国外现状 (1)1.2.2国内现状 (5)1.3本文主要内容及章节内容 (6)第二章 平衡车系统原理分析 (7)2.1控制系统任务分析 (7)2.2平衡车数学模型 (8)2.2.1 平衡车的受力分析 (8)2.2.2平衡车的运动微分方程 (11)2.3 串级PID在平衡控制和速度控制中的应用 (12)2.3.1 PID算法简介 (12)2.3.2 PID算法在平衡控制中的应用原理 (14)2.3.3 PID算法在速度控制中的应用原理 (14)2.3.4 串级PID的原理及在系统中的应用 (15)2.4基于互补滤波的数据融合 (16)2.5本章小结 (16)第三章 系统硬件电路设计 (17)3.1 单片机最小系统STM32F103C8T6 (18)3.2系统电源模块 (19)3.3 运动处理传感器模块 (20)3.4电机驱动电路 (21)3.5编码器电路 (23)3.6底板综合设计 (24)3.7系统遥控电路设计 (26)3.7.1 单片机STC89C52 (26)3.7.2 无线收发器模块NRF24L01 (27)3.7.3 液晶显示模块12864 (28)3.8本章总结 (29)第四章 系统软件程序设计 (30)4.1主程序框架与初始化 (30)4.2 数据采集 (32)4.2.1.输入信号采集函数 (32)4.2.2.捕获电机脉冲函数 (32)4.3互补滤波数据融合算法 (33)4.4 串级PID控制 (33)4.4.1直立PD控制 (33)4.4.2速度PI控制 (34)4.5电机PWM输出 (36)4.6程序优化 (37)4.7本章小结 (37)第五章 系统调试 (38)5.1系统开发平台 (38)5.2姿态检测系统调试 (39)5.3控制系统PID参数的整定 (41)5.3.1直立PD控制参数调试 (41)5.3.2速度PI控制参数调试 (41)5.4本章小结 (42)第六章 总结与展望 (43)6.1总结 (43)6.2展望 (43)参考文献 (44)作者简介及攻读硕士期间发表的论文 (46)致 谢 (47)第一章 绪论1.1研究背景及意义近年来,双轮自平衡车的发展势头迅猛主要有以下两个原因,其一是它的实用性很强,可以应用到绝大多数领域,其二是支撑搭建双轮自平衡车的理论体系逐渐完善,技术手段日益先进,如数据获取更简单有效,数据处理更科学精确。

迁移率散射机理

迁移率散射机理
The mobility in UTBB-FDSOI devices is actually limited by a complex interplay between carrier–phonons interactions, front interface roughness (FSR) and back interface roughness (BSR) , remote Coulomb scattering (RCS) , and possibly remote phonon scattering (RPS) . The strength of most of these mechanisms depends a lot on the applied front and back gate bias voltages.
Thickness of BOX and Ground Plane
Id(Vg) characteristics
Quantum Modeling of the Carrier Mobility in FDSOI Devices
Computed the elecctron and hole mobilities in ultrathin body and buried oxide, fully depleted silicon on insulator devices with various high-k metal gate-stacks using nonequilibrium Green's functions(NEFG).
These results show that FDSOI devices are a foremost tool to sort out the different scattering mechanisms in Si devices, and that NEGF can provide valuable inputs to technology computer aided design.

多参数迭代的船用二回路系统热平衡计算方法

多参数迭代的船用二回路系统热平衡计算方法

多参数迭代的船用二回路系统热平衡计算方法崔佳林;杨自春;张磊【摘要】According to types of equipment and operation characteristics of Marine nuclear power plant, the method of steam consumption computing of main secondary circuit equipment is given. A multi-parameter iteration heat balance com-puting model is established on the basis of considering practical features such as multi-equipment, multi-mode and strong coupling of secondary circuit. The known parameters are used to verify the established heat balance model and the comput-ing precision. The steam and water flow rate and the matching feature of peculiar equipment of nuclear power plant under three typical operating conditions are analyzed, and the efficiency of power plant under different operating conditions is achieved. Through the research result of secondary circuit, technology references are provided for the study of variable oper-ation and design optimization.%针对船用核动力装置的设备类型和运行特点,给出了二回路系统主要设备耗汽量计算方法.考虑二回路系统设备繁多、工况多变、耦合性强等实际特点,建立了基于多参数迭代法的热平衡计算模型.利用已知参数验证所建立热平衡模型和编制程序的计算精度.分析了3种典型工况下核动力装置特有设备的汽水流量及状态参数的匹配特性,得出了不同工况下的装置效率.相应研究成果可为船用核动力二回路系统的变工况运行研究和设计优化提供技术借鉴和参考.【期刊名称】《舰船科学技术》【年(卷),期】2018(040)006【总页数】6页(P79-83,109)【关键词】核动力;二回路;热平衡;多参数迭代方法【作者】崔佳林;杨自春;张磊【作者单位】海军工程大学动力工程学院舰船高温结构复合材料研究室,湖北武汉 430033;海军工程大学动力工程学院舰船高温结构复合材料研究室,湖北武汉430033;海军工程大学动力工程学院舰船高温结构复合材料研究室,湖北武汉430033【正文语种】中文【中图分类】U664.150 引言船用核动力二回路系统承担着将一回路释放的热能转换为机械能和电能的任务[1]。

  1. 1、下载文档前请自行甄别文档内容的完整性,平台不提供额外的编辑、内容补充、找答案等附加服务。
  2. 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
  3. 3、如文档侵犯您的权益,请联系客服反馈,我们会尽快为您处理(人工客服工作时间:9:00-18:30)。

a r X i v :0708.3296v 1 [c o n d -m a t .m t r l -s c i ] 24 A u g 2007Observation of strong-coupling effects in a diluted magnetic semiconductor Ga 1-x Fe x NW.Pacuski,1,2,∗P.Kossacki,1D.Ferrand,2A.Golnik,1J.Cibert,2M.Wegscheider,3A.Navarro-Quezada,3A.Bonanni,3M.Kiecana,4M.Sawicki,4and T.Dietl 4,5,61Institute of Experimental Physics,Warsaw University,Ho˙z a 69,PL-00-681Warszawa,Poland 2Institut N´e el/CNRS-Universit´e J.Fourier,Boˆıte Postale 166,F-38042Grenoble Cedex 9,France3Institute for Semiconductor and Solid State Physics,Johannes Kepler University,Altenbergerstrasse 69,A-4040,Linz,Austria4Institute of Physics,Polish Academy of Sciences,al.Lotnik´o w 32/46,PL 02-668Warszawa,Poland5ERATO Semiconductor Spintronics Project of Japan Science and Technology Agency,al.Lotnik´o w 32/46,PL 02-668Warszawa,Poland6Institute of Theoretical Physics,Warsaw University,ul.Ho˙z a 69,PL-00-681Warszawa,Poland A direct observation of the giant Zeeman splitting of the free excitons in Ga 1-x Fe x N is reported.The magnetooptical and magnetization data imply the ferromagnetic sign and a reduced magnitude of the effective p -d exchange energy governing the interaction between Fe 3+ions and holes in GaN,N 0β(app)=+0.5±0.2eV.This finding corroborates the recent suggestion that the strong p -d hybridization specific to nitrides and oxides leads to significant renormalization of the valence band exchange splitting.PACS numbers:75.50.Pp,75.30.Hx,78.20.Ls,71.35.JiA strong hybridization between anion p states and open d shells of transition metals (TM)is known to ac-count for spin-dependent properties of magnetic isola-tors,semiconductors,and superconductors,such as an-tiferromagnetic superexchange,hole-mediated Zener fer-romagnetism,and the contribution of spin fluctuations to Cooper pairing.Furthermore,the corresponding ex-change splitting of the bands gives rise to giant mag-netooptical and magnetotransport phenomena,a finger-print of purposeful spintronic materials.Studies of the p -d exchange interaction have been particularly reward-ing in the case of Mn-based II-VI dilute magnetic semi-conductors (DMS)such as (Cd,Mn)Te [1,2].In these systems,Mn is an isoelectronic impurity with a simple d 5configuration,allowing a straightforward,quantitative determination of the p -d exchange integral βfrom the so-called giant Zeeman effect of the exciton:using the vir-tual crystal (VCA)and molecular-field approximations (MFA),one calculates a contribution to the spin split-tings proportional to the Mn magnetization and to N 0|β|,where N 0is the cation density.At the same time,the de-termination by photoemission spectroscopy [3],and the computation [4,5],of band structure parameters demon-strated that the antiferromagnetic p -d exchange results indeed from p -d hybridization.According to the above insight,in II-VI oxides and III-V nitrides,a small bond length and,thus,strong p -d hybridization,should result in particularly large val-ues of N 0|β|,a prediction supported by photoemission experiments [6].Surprisingly,however,some of the present authors found abnormally small exciton split-tings in (Zn,Co)O [7],(Zn,Mn)O [8],and (Ga,Mn)N [9].Prompted by this contradiction,one of us suggested [10]that due to the strong p -d coupling,oxides and nitridesform an outstanding class of DMS,in which VCA breaks down,making the apparent exchange splitting N 0β(app)small and of opposite sign.Importantly,the system bears some similarity with semiconductor alloys such as Ga(As,N),so that experimental and theoretical studies of the valence band exchange splitting in the strong cou-pling limit may significantly improve our understanding of these important alloys.To check the above model,we have carried out high-resolution studies of magnetization and magnetoreflec-tivity in the free exciton region for (Ga,Fe)N epitaxial layers,thoroughly characterized previously [11].Since in GaN,in contrast to ZnO,the actual ordering of valence subbands is settled,the sign of N 0β(app)can be unam-biguously determined from polarization-resolved magne-tooptical spectra.Furthermore,unlike Mn,Fe in GaN is an isoelectronic impurity with the simple d 5configu-ration [11,12],allowing a straightforward interpretation of the data.Our results lead to a value of N 0β(app)=+0.5±0.2eV,which provides an important experimental support for the theory [10].The 0.7µm thick layers of Ga 1-x Fe x N were grown [11]by metalorganic vapor phase epitaxy (MOVPE),on [0001]sapphire substrates with a 1µm thick,wide-band gap (Ga,Al)N buffer layer,which is transparent in the free exciton region of Ga 1-x Fe x N.The Fe flow rate was adjusted to keep the Fe content well below 0.4%,which is the solubility limit of Fe in GaN under our growth condi-tions.According to detailed luminescence,electron para-magnetic resonance,and magnetic susceptibility studies [11],in this range the Fe ions assume mostly the ex-pected Fe 3+charge state corresponding to the d 5con-figuration,for which the spin polarization as a function of temperature T and magnetic field B is determined2Magnetic Field (T)R e d s h i f t o f e x c i t o n A (m e V )Μa g n e t i z a t i o n ( e m u /c m 3)Magnetic Field (T)Μa g n e t i z a t i o n d i f f e r e n c e ( e m u /c m 3)FIG.1:(color online)(a)Difference between magnetizations measured (symbols)at 1.8and 5K.Same difference,com-puted (solid line)using the Brillouin function for S =5/2and treating the Fe concentration x as the only fitting pa-rameter.(b)Comparison between the computed magnetiza-tion (solid lines,right axis)and the redshift of exciton A in σ−polarization (symbols,left axis)for the 0.21%sample at three temperatures.The spectra are shown in Fig.2(a).by the Brillouin function B S (T,B )with spin S =5/2and Land´e factor g F e 3+=2.0.This is confirmed by our magnetooptical data shown in Fig.1,which scale with B 5/2(T,B ).For the reported samples,we determine Fe content 0.11±0.02%and 0.21±0.02%by fitting the differ-ence in magnetization values measured at 1.8and 5.0K up to 5T in a high-field SQUID magnetometer,Fig.1(a).Magneto-reflectivity spectra were collected in the Fara-day configuration (propagation of light and magnetic field along the normal to the sample,which is the c -axis of the wurtzite structure),and the light helicity σ±de-fined with respect to the magnetic field direction.Owing to the high quality of the layers,either two,or the three,free excitons of GaN [13],A ,B ,C ,are resolved,and their Zeeman shifts are visible in the spectra (Fig.2).In σ−polarization,the A −B splitting increases and the B −C splitting decreases with the field.Opposite shifts are observed in σ+.Since these shifts are entirely differ-ent from those observed in pure GaN [13],and related to the magnetization [Fig.1(b)],we conclude that the Fe ions create a ”giant Zeeman effect”in (Ga,Fe)N.Re-markably,however,the shift observed for A exciton is opposite in sign and significantly smaller at given x than in other wurtzite DMS with d 5ions such as (Cd,Mn)Se [14].We now describe the methodology that we employed to extract the values of the apparent p -d exchange en-ergy N 0β(app)for the valence band and the apparent s -d exchange energy N 0α(app)for the conduction band,from the reflectivity spectra.It involves two major steps.First,we calculate the reflection coefficients as a function of the photon energy,using a polariton model which in-corporates the ground states of excitons A and B [7],but also exciton C ,excited states of excitons,and the continuum.Second,the field dependence of the exciton energies is calculated taking into account the essential features of the exciton physics in wide-band gap wurtzite DMS [7,9].The starting point of the polariton model is the di-electric function ǫ(ω,k )containing polariton poles corre-sponding to excitons A and B [7,15]:by solving ana-lytically Eq.3of Ref.15,we obtain the refractive index and then the reflection coefficient to be compared to ex-perimental spectra.However,we replace the background dielectric function ǫ∗0by the residual dielectric function ǫ∗(ω),which takes into account additional contributions which are expected to exhibit no significant polariton ef-fect [16]:exciton C ,excited states of A ,B and C [16]which are optically active (S -states),and transitions to the continuum of unbound states [17].Henceǫ∗(ω)=ǫ∗0+4πα0CωCn 3ωn,j33497349934863488P h o t o n E n e r g y (m e V )Magnetic Field (T)P h o t o n E n e r g y (m e V )3517R e f l e c t i v i t yPhoton Energy ( meV )R e f l e c t i v i t yFIG.2:(color online)Reflectivity of Ga 1-x Fe x N in Faraday configuration at 1.6K for x =0.21%(a)and 0.11%(c)where particularly well resolved excitons A ,B ,and C are visible in σ−polarization.(b,d)Field-induced exciton shifts of the exci-tons determined from the polariton model (points)compared to the expectations of the exciton model (solid lines).The de-termined values of the exciton and exchange parameters are shown in Table I.Effects linear in the magnetic field are taken into account by the standard Zeeman hamiltonian H Z [13,21],param-eterized by the effective Land´e factor g e =1.95for the electrons and the relevant Luttinger effective parameter ˜κ=−0.36that describes the splitting of all three valence subbands [13].The diamagnetic shift is described by a single term quadratic in the magnetic field,H diam =dB 2,where d =1.8µeV/T 2[13].Finally,H (app)sp −d is the ex-change interaction between Fe ions and carriers in the extended states from which the excitons are formed.We use the standard form of the s ,p -d hamiltonian [1,2,14],which is proportional to the scalar product of the car-rier spin and the magnetization.However,being aware that these splittings can have a different meaning from the usual one [10,24],we use effective quantities α(app)and β(app).The field dependence of the exciton energies,calculated with the values of fitting parameters collected in Table I,is compared with the experimental results in Fig.2(b,d).The detailed analysis of this hamiltonian [9]shows thatxN 0(β(app)−α(app))N 0(β(app)+α(app))E A˜∆1∆24ies carried out in our labs,which lead systematically to N0β=−1.4±0.5eV[2].However,it has been recently remarked[10]that for an appropriately strong TM potential,like the one expected for oxides and nitrides,the TM ion can bind a hole–a trend which was already suggested by strong deviations from the VCA in(Cd,Mn)S[25]and by the analysis of ab-initio calculations[26].A summation of infinite series of relevant self-energy diagrams demonstrates that in such a situation,the spin splitting of extended states involved in the optical transitions remains proportional to magne-tization of the localized spins,but the apparent exchange energy becomes significantly renormalized[10].In fact, for the expected coupling strength,the theory predicts −1<β(app)/β<0,as observed here for(Ga,Fe)N.A fruitful comparison can be made with the modifica-tion of the conduction band of GaAs induced by a slight doping with Nitrogen[27].When a hydrostatic pressure is applied,the Nitrogen isoelectronic centers create local-ized states,which are observed in photoluminescence,but also extended states(the so-called E+states)to which the oscillator strength is transferred so that they are ob-served in reflectivity;moreover,these optically active states exhibit an anticrossing with the localized states, and the strength of the anticrossing increases with the Nitrogen density.As a result,the transition to these E+ states exhibits a shift to high energy when the density of low energy states increases.In a DMS with a large value of N0|β|,only the TM impurities with the right spin ori-entation(antiparallel to the hole spin)are expected to form a localizing center[10,25]:hence the giant Zeeman shift in(Ga,Fe)N can be understood as resulting from a similar anticrossing but in this case the density of rel-evant localized centers is additionally controlled by the field-induced orientation of the localized spins.In conclusion,giant Zeeman splitting has been ob-served by magnetoreflectivity for the A,B,and C ex-citons in Ga1−x Fe x N.The spectra are well described by the exciton model valid for DMS with the wurtzite struc-ture.The determined sign and magnitude of the appar-ent p-d exchange energy N0β(app)=+0.5±0.2eV con-stitutes an important verification of a recent theory[10], which describes the effects of the p-d interaction circum-venting the virtual-crystal and molecular-field approxi-mations that break down in nitrides and oxides.In these systems,TM ions bind holes,precluding in this way the occurrence of carrier-mediated ferromagnetism in p-type materials.However,at sufficiently high hole densities,an insulator-to-metal transition is expected.In the metallic phase,many-body screening of local potentials annihi-lates bound rge spin-splitting and robust fer-romagnetism are expected in this regime[28,29].This work was supported by Polish Ministry of Science and Higher Education(project N20200631/0153),by the Austrian Fonds zur F¨o rderung der wissenschaftlichen Forschung-FWF(projects P17169-N08and N107-NAN)and by the French Ministry of Foreign Affairs.∗Electronic address:Wojciech.Pacuski@.pl[1]J.K.Furdyna and J.Kossut,eds.,Diluted MagneticSemiconductors,vol.25of Semiconductors and Semimet-als(Academic Press,New York,1988).[2]P.Kacman,Semicond.Sci.Technol.16,R25(2001),andreferences cited therein.[3]T.Mizokawa,T.Nambu,A.Fujimori,T.Fukumura,andM.Kawasaki,Phys.Rev.B65,085209(2002).[4]A.Zunger,Solid State Phys.vol.39,275(1986).[5]rson,K.C.Hass,E.Ehrenreich,and A.E.Carls-son,Phys.Rev.B37,4137(1988).[6]J.I.Hwang,Y.Ishida,M.Kobayashi,H.Hirata,K.Takubo,T.Mizokawa, A.Fujimori,J.Okamoto, K.Mamiya,Y.Saito,et al.,Phys.Rev.B72,085216 (2005).[7]W.Pacuski,D.Ferrand,J.Cibert,C.Deparis,J.A.Gaj,P.Kossacki,C.Morhain,Phys.Rev.B73,035214(2006).[8]E.Prze´z dziecka,E.Kami´n ska,M.Kiecana,M.Sawicki,L.K l opotowski,W.Pacuski,and J.Kossut,Solid State Commun.139,541(2006).[9]W.Pacuski,D.Ferrand,J.Cibert,J.A.Gaj,A.Golnik,P.Kossacki,S.Marcet,E.Sarigiannidou,and H.Mari-ette,cond–mat/0703041.[10]T.Dietl,cond-mat/0703278.[11]A.Bonanni,M.Kiecana,C.Simbrunner,T.Li,M.Saw-icki,M.Wegscheider,M.Quast,H.Przybyli´n ska,A.Navarro-Quezada,R.Jakie l a,et al.,Phys.Rev.B75,125210(2007).[12]E.Malguth,A.Hoffmann,W.Gehlhoff,O.Gelhausen,M.R.Phillips,and X.Xu,Phys.Rev.B74,165202 (2006),and references cited therein.[13]R.St¸e pniewski,M.Potemski,A.Wysmo l ek,K.Paku l a,J.M.Baranowski,J. L usakowski,I.Grzegory, S.Porowski,G.Martinez,and P.Wyder,Phys.Rev.B 60,4438(1999).[14]M.Arciszewska and M.Nawrocki,J.Phys.Chem.Solids47,309(1986).[15]gois,Phys.Rev.B16,1699(1977).[16]R.St¸e pniewski,K.P.Korona,A.Wysmo l ek,J.M.Bara-nowski,K.Paku l a,M.Potemski,G.Martinez,I.Grze-gory,and S.Porowski,Phys.Rev.B56,15151(1997).[17]C.Tanguy,Phys.Rev.Lett.75,4090(1995).[18]K.Kornitzer,T.Ebner,M.Grehl,K.Thonke,R.Sauer,C.Kirchner,V.Schwegler,M.Kamp,M.Leszczynski,I.Grzegory,et al.,Phys.Stat.Sol.B216,5(1999).[19]R.Le Toullec,N.Piccioli,and J.C.Chervin,Phys.Rev.B22,6162(1980).[20]B.Sermage,S.Petiot,C.Tanguy,Le Si Dang,and R.Andr´e,J.Appl.Phys.83,7903(1998).[21]G.L.Bir and G.E.Pikus,in Symmetry and Strain-Induced Effects in Semiconductors(Halsted,Jerusalem, 1974).[22]B.Gil,O.Briot,and R.L.Aulombard,Phys.Rev.B52,R17028(1995).[23]M.Julier,J.Campo,B.Gil,scaray,S.Nakamura,Phys.Rev.B57,R6791(1998).[24]C.´Sliwa and T.Dietl,cond-mat/0707.3542.[25]C.Benoˆıt`a la Guillaume,D.Scalbert,and T.Dietl,Phys.5Rev.B46,9853(1992).[26]R.Bouzerar,G.Bouzerar,and T.Ziman,Europhys.Lett.78,67003(2007).[27]J.Wu,W.Shan,and W Walukiewicz,Semicond.Sci.Technol.17,860(2002),and references cited therein.[28]T.Dietl,F.Matsukura,and H.Ohno,Phys.Rev.B66,033203(2002).[29]F.Popescu,C.S¸en,E.Dagotto,and A.Moreo,cond-mat/0705.0309,and references cited therein.。

相关文档
最新文档