接大地的双绞线负载响应简化模型

电子设备电源线一般为双绞线,由于结构特殊,在计算其受辐射负载响应时非常繁琐。很多情况下,电源线中有一条是连接大地的地线,且离地高度远大于绞线间距。针对该类双绞线受辐射时的负载响应计算问题,从Taylor模型出发,提出一种分析接地平行双线负载响应的简化模型,并推广至双绞线。该模型是将接地双绞线等效成电流为两倍的理想导电平面上的单导线模型,通过求解单线模型的BLT方程,计算其负载响应。与CST仿真结果的比较证明了该模型的有效性。     

Dynamical effects of switching a super-critical well potential on pair creation from a vacuum

The dynamical effects on electron-positron pair creation from a vacuum caused by the switching processes of a supercritical well potential are investigated in detail. The results show that only when the switching on and switching off time both increase will the final pair yield converge to the integer of embedded bound states nearly exponentially. But a single adiabatic switching on or switching off cannot lead to an integer pair yield. If the potential is turned on abruptly, associated with the discrete and embedded bound states, there is multi-frequency oscillation around the pair number's saturation. The slowly switching on can suppress the amplitude of this oscillation and reduce the final pair yield. The switching off can also reduce the final pair number in the same order of magnitude. The evolution of a single-pair number shows a robust long range correlation between particle and antiparticle. For an adiabatic switching case, the single-pair dominates the early pair creation, their upper limit value is equal to the integer, and these single-pairs will totally disentangle during the switching off.     

Thermodynamic design data for double effect absorption heat pump systems using water-lithium chloride—cooling

In this paper, thermodynamic design data are investigated for the water-lithium chloride pair and a comparative study of the water-LiCl pair with the water-LiBr pair is given, for double-effect absorption cooling systems used for the computer simulation. The computer simulation is based on mass, material and heat balance equations for each part of the system. Coefficients of performance and flow ratios for effects of different operating temperatures are investigated. It is found that the cooling COP is higher for the water-LiCl pair than for the water-LiBr pair, and FR is lower for the water-LiCl pair than for the water-LiBr pair.     

Mirror nesting of the Fermi contour and zero line of the superconducting order parameter

The superconducting order parameter that emerges owing to pairing of charge carriers with a large total momentum of the pair during screened Coulomb repulsion in a degenerate quasi-two-dimensional electronic system is determined as a function of the momentum of relative motion of the pair. In view of the kinematic constraint associated with Fermi filling, the ordered state exists in a limited domain of the momentum space, the shape and size of this domain being determined by the total momentum of the pair. The order parameter is not a constant-sign function of the momentum and reverses its sign on a certain line in a kinematically allowed domain. Superconducting instability arises for an arbitrarily small value of the repulsive interaction for certain momenta of the pair, for which the mirror nesting condition is satisfied; this results in the formation of a pair Fermi contour, i.e., the line of coincidence of segments of the Fermi contour with the isoline of the kinetic energy of relative motion of the pair. The temperature dependence of the superconducting order parameter is studied. Owing to the proximity effect in the momentum space, superconducting ordering is extended to the kinematically forbidden domain.     

Pair Events in Superluminal Optics

When an object moves faster than emissions it creates, it may appear at two positions simultaneously. The appearance or disappearance of this bifurcation is referred to as a pair event. Inherently convolved with superluminal motion, pair events have no subluminal counterparts. Common examples of superluminal motions that exhibit pair events include Cherenkov radiation, sonic booms, illumination fronts from variable light sources, and rotating beams. The minimally simple case of pair events from a single massive object is explored here: uniform linear motion. A pair event is perceived when the radial component of the object's speed toward the observer drops from superluminal to subluminal. Emission from the pair creation event will reach the observer before emission from either of the two images created. Potentially observable image pair events are described for sonic booms and Cherenkov light. To date, no detection of discrete images following a projectile pair event have ever been reported, and so the pair event nature of sonic booms and Cherenkov radiation, for example, remains unconfirmed. Recent advances in modern technology have made such pair event tracking feasible. If measured, pair events could provide important information about object distance and history.     

Anti-Chudakov effect in high-energy electron–positron pair ionization loss in thin target

The problem of electron–positron pair ionization loss on different distances from its creation point in substance is considered. It is shown that together with the Chudakov effect of pair loss reduction the opposite effect of exceeding by the pair loss of the doubled value of single electron (positron) loss may take place. It is demonstrated that for pair ionization loss in the same substance where the pair is created such effect is rather small but can enhance by the order of magnitude if consider the pair loss in thin plate situated in the direction of pair motion on some distance from this substance. It is pointed out that such effect should be most significant at relatively low pair energies of several hundreds MeV.     

Mutual-focusing of two co-propagating beams and formation of trapped spatial breather pair in saturable nonlinear media

In this paper, using parabolic equation approach, coupled propagation of two coaxially co-propagating and mutually incoherent bright cylindrical beams in saturable nonlinear medium has been investigated. Considering the coupling coefficient equal to unity (κ=1), a detailed account of formation of spatial soliton pair (i.e. both beams are stationary trapped) and spatial breather pair (i.e. width of each beam oscillates with the propagation distance) has been provided and existence of spatially trapped breather pair (i.e. average width of each breather of the pair does not change with the propagation distance) has been shown. Conditions of formation of trapped spatial breather pair and their existence line has also been revealed for arbitrary beam width ratio of the beams. It is revealed that spatial soliton pairs are just a special case of trapped breather pair. The regions (conditions) of mutual-focusing and mutual-defocusing of spatial soliton pair/breather pair have also been identified. Lastly, the law of trapped breather pair formation is proposed.     

Pair Formation of Hard Core Bosons in Flat Band Systems

Hard core bosons in a large class of one or two dimensional flat band systems have an upper critical density, below which the ground states can be described completely. At the critical density, the ground states are Wigner crystals. If one adds a particle to the system at the critical density, the ground state and the low lying multi particle states of the system can be described as a Wigner crystal with an additional pair of particles. The energy band for the pair is separated from the rest of the multi-particle spectrum. The proofs use a Gerschgorin type of argument for block diagonally dominant matrices. In certain one-dimensional or tree-like structures one can show that the pair is localised, for example in the chequerboard chain. For this one-dimensional system with periodic boundary condition the energy band for the pair is flat, the pair is localised.     

Dark-state mechanism for the long-time transfer of excitations in a donor–acceptor system

The excitation energy transfer between a donor–acceptor pair with fixed distance apart through energy exchanging with environment is investigated. The total system is modeled as two two-level systems (TLSs) interacting with many harmonic oscillators. The pair behaves coherently or incoherently, depending on whether the dipolar coupling is stronger or weaker than the TLS–environment coupling. The environmental linear dispersion relation gives an analytical solution to the pair?s probability involving all the retardation times. We found that the long-time trapping of energy within the pair is caused by the inhibiting dark-state radiative decay when two TLSs are at half a resonant wavelength.     

Entanglement of spin pairs in alternating open spin-1/2 chains with the XY Hamiltonian

We investigate entanglement of spin pairs in alternating open spin chains (s = 1/2) with spin-spin interactions (SSI) in the thermodynamic equilibrium state in an external magnetic field. The reduced density matrix of an arbitrarily chosen spin pair was calculated. The entanglement of a spin pair was evaluated with the Wootters criterion. The temperature at which the entangled state arises in the chosen pair was determined. Entanglement (concurrence) is shown to oscillate as a function of the position of a spin pair in the chain. The results demonstrate the dependence of the entanglement in arbitrarily chosen pairs of neighboring spins on the temperature, the position of the spin pair in the chain, chain length, and the ratio between the SSI constants. Qualitative explanation of these dependences is offered. The role of the terminal spins in the generation of entanglement is explained.     

The Laplace transform of the MSA pair distribution functions between macroions in an ion-dipole fluid

The Laplace transform is obtained for the pair distribution function between a pair of ions, an ion and a macroion, and a pair of macroions in an ion-dipole fluid. This fluid is a simplified model of an electrolyte with a discrete model of solvent (hard spheres with embedded point dipoles). From these results, an expression for the solvation force between macroions is obtained. This result consists of the classical DLVO result plus a series of corrections.     

Impurity pair modes in a diatomic linear chain: nearest neighbour pair

The behaviour of the impurity modes due to a pair of substitutional impurities characterized by both mass as well as force-constant changes and occupying nearest neighbour positions in a diatomic linear chain, is studied. The results are compared with those for the case of impurity pairs occupying next nearest neighbour sites discussed earlier as well as the existing three dimensional calculations of Elliott and Pfeuty. The nearest neighbour impurity pair gap and local modes can be interpreted in terms of two single impurities substituted in the two different sublattices unlike the next nearest neighbour pair modes. The inband resonant modes are totally new features characteristic of the pair. Finally, the predictions of the theory are compared with the available experimental data for Si-impurity-pair-complexes and qualitative agreement is shown.     

Structure of D Pair in Collective States of Nuclei

As a successive work a modified D pair independent of the S pair treated in our previous papers is introduced to avoid the seniority mixing problem. The structure amplitudes of this D pair and S pair are determined simultaneously and self-consistently by iteration.     

10T脉冲磁场的亥姆霍兹线圈热和力分析

亥姆霍兹线圈在产生数十T的准静态脉冲磁场的装置中得到广泛应用。以自行研制的一套用于磁压剪实验技术的脉冲磁场发生系统的亥姆霍兹线圈为研究对象,结合装置的电参数,利用有限元软件ANSYS对装置放电过程中线圈的热和力进行了仿真研究。研究结果表明,当装置在线圈中产生上升时间约1.34 ms、幅值14.37 kA的放电电流和10.7 T的磁场时,线圈中的最大温升约150℃,最大应力近0.5 GPa,铜导线中的最大应力约0.2 GPa,线圈导线变形位移小于0.05 mm。基于分析结果,在线圈制作时,选择绝缘层耐温超过200℃、抗拉强度0.5 GPa的铜导线作为线圈绕线,选择抗拉强度达5.8 GPa的柴龙纤维绕制在铜导线外层进行加固,并制作了相应结构的亥姆霍兹线圈对。利用该线圈对进行的放电实验测试结果表明,在满足设计指标的情况下,线圈对结实可靠,可重复使用。     

Structure of D Pair in Collective States of Nuclei

As a successive work a modified D pair independent of the S pair treated in our previous papers is introduced to avoid the seniority mixing problem. The structure amplitudes of this D pair and S pair are determined simultaneously and self-consistently by iteration,     

Simulation and thermodynamic design data study on double-effect absorption cooling cycle using water-LiBr-LiSCN mixture

In this study, for double-effect absorption cooling systems, a computer simulation which is based on mass, material and heat balance equations for each part of the system is described. Thermodynamic design data are investigated for the water-lithium bromide-lithium thiocyanate mixture and a comparative study of the water-LiBr-LiSCN mixture with the water-LiBr pair and the water-LiCl pair is given. The influences of component temperatures on the cooling coefficients of performance have been investigated to obtain operating condition. It is found that the cooling COP is higher for water-LiBr-LiSCN mixture than for the water-LiBr pair or for the water-LiCl pair, and the flow ratio of water-LiBr-LiSCN mixture is not higher than that of the water-LiBr pair.     

Nonlinear Excitations in Hydrogen-Bonded Chains with Anharmonic Interatomic Interactions

We discuss the nonlinear excitations and the motion of a kink soliton pair in hydrogen-bonded chains with anharmonic interatomic interactions, based on a two-component soliton model, using a direct perturbation method. The expression for the asymmetric solutions of the kink soliton pair is found because of anharmonicity, and the energy, the momentum and the effective mass of a kink pair for cubic and quartic anharmonicity are calculated, which are in good agreement with the experimental data.     

扬声器的特性不匹配对虚拟声像的影响

本文从理论和实验上探讨了扬声器的特性不匹配对重放虚拟声像的影响。结果表明,用两扬声器进行虚拟听觉重放时,在某些频率段和虚拟声像角度,两扬声器间很小的幅频特性差异或相频特性差异都足以对虚拟声像方向产生明显的影响。扬声器特性的差异对前方范围的声像影响较小,但对侧向范围的声像影响较大,因而两扬声器的特性不匹配也是导致虚拟听觉重放时侧向声像位置畸变的重要原因之一。而在实际应用中要特别注意两扬声器的特性匹配,或者要用信号处理的方法对两扬声器的特性进行校正。     

基于标记配对相干态光源的诱骗态量子密钥分配性能分析

从有效性、稳定性和可行性三个方面, 对基于标记配对相干态光源的诱骗态量子密钥分配的性能进行了全面分析. 采用四组实验数据对基于标记配对相干态光源的三强度诱骗态方案的密钥生成效率、量子比特误码率和最优信号态强度与安全传输距离之间的关系进行了仿真和分析; 考虑到光源涨落, 对方案的稳定性进行了讨论和仿真; 并对基于标记配对相干态光源设计简单易实现方案的可行性进行了分析. 结论表明: 基于标记配对相干态光源的诱骗态方案性能在安全传输距离和密钥生成效率两方面都优于现有基于弱相干态光源和预报单光子源的诱骗态方案; 在光源强度涨落相同条件下, 标记配对相干态光源的稳定性逊于预报单光子源, 而优于相干态光源. 但是标记配对相干态光源在有效性上的优势可弥补其在稳定性上的不足; 且标记配对相干态光源的双模特性为设计简单易实现的被动诱骗态方案提供了条件. 关键词： 量子光学 量子密钥分配 标记配对相干态光源 性能     

Photon pair source via two coupling single quantum emitters

We study the two coupling two-level single molecules driven by an external field as a photon pair source. The probability of emitting two photons, P2, is employed to describe the photon pair source quality in a short time, and the correlation coefficient RAB is employed to describe the photon pair source quality in a long time limit. The results demonstrate that the coupling single quantum emitters can be considered as a stable photon pair source.