Entanglement entropy in a one-dimensional disordered interacting system: the role of localization

The properties of the entanglement entropy (EE) in one-dimensional disordered interacting systems are studied. Anderson localization leaves a clear signature on the average EE, as it saturates on the length scale exceeding the localization length. This is verified by numerically calculating the EE for an ensemble of disordered realizations using the density matrix renormalization group method. A heuristic expression describing the dependence of the EE on the localization length, which takes into account finite-size effects, is proposed. This is used to extract the localization length as a function of the interaction strength. The localization length dependence on the interaction fits nicely with the expectations.     

部分空间和部分光谱相干高斯-谢尔模型脉冲光束在自由空间中的光谱和时间特性

 对部分空间和部分光谱相干２维高斯-谢尔模型脉冲光束在自由空间传输的光谱和时间特性做了详细的数值研究。结果表明,部分空间和部分光谱相干高斯-谢尔模型脉冲光束在自由空间传输中发生了光谱移动,光谱移动与场点位置、空间相关长度和时间相干长度有关。在轴上,光谱出现蓝移,相对光谱移动随传输距离的增加而增大,随空间相关长度和时间相干长度的增加而减小,并逐渐趋于一定值。在轴外,光谱出现蓝移和红移,并与空间相关长度和时间相干长度有关。脉冲时间波形不变,对所得主要结果做了物理解释。     

On the attached length of orifices

The attached length of orifices in reactive mufflers has been estimated based on numerical calculations by the finite-element method. The numerical results for a diaphragm in a duct are compared with the theoretical data obtained by Rayleigh, Fock, Karal, and Ingard. The dependence of the attached length on the diaphragm thickness is given. The results obtained are generalized for the case in which the orifice is a Helmholtz resonator neck. The effect of the resonator length on the attached length of the neck is analyzed.     

高斯-谢尔模光束在大气湍流中传输的相干特性研究

文章分析了高斯-谢尔光束在大气湍流中传输时相干长度的变化, 并与真空传输做比较, 真空传输相干长度的变化只与光源参数有关, 大气湍流中传输相干长度的变化受光源参数和湍流的共同影响. 真空传输光束扩展造成相干长度增大; 大气湍流中, 传输距离较短时, 相干长度由于光源扩展而增加, 当传输距离较大时, 湍流效应增强引起相干长度下降. 因此, 单纯从相干长度方面分析大气湍流带来的影响不够完备. 为排除光源扩展影响, 利用相干长度与光斑尺度的比值进行分析, 发现大气湍流会造成比值的下降. 在数值仿真的基础上对上述结果给出了解释. 关键词： 部分相干 大气湍流 高斯-谢尔模 光束扩展     

发射光学系统分析

 采用矩阵光学方法导出了发射光学系统的传输变换矩阵和具有两级扩束系统的发射系统的调焦公式,研究了输入激光不是平行光时远场焦点位置的变化和一级扩束系统焦距变化对系统焦距的影响。     

基于微观结构的Cu互连电迁移失效研究

提出了一种基于微观晶粒尺寸分布的Cu互连电迁移失效寿命模型. 结合透射电子显微镜和统计失效分析技术, 研究了Cu互连电迁移失效尺寸缩小和临界长度效应及其物理机制. 研究表明, 当互连线宽度减小, 其平均晶粒尺寸下降并导致互连电迁移寿命降低. 小于临界长度的互连线无法提供足够的空位使得铜晶粒耗尽而发生失效. 当互连长度大于该临界长度时, 在整个电迁移测试时间内, 部分体积较小的阴极端铜晶粒出现耗尽情况. 随着互连长度的增加该失效比例迅速增大, 电迁移失效寿命减小. 当互连长度远大于扩散长度时, 失效时间主要取决于铜晶粒的尺寸, 且失效寿命和比例随晶粒尺寸变化呈现饱和的波动状态. 关键词： Cu 互连 电迁移 微观结构     

Length distribution of stiff, self-assembled polymers at thermal equilibrium

We investigate the length distribution of self-assembled, long and stiff polymers at thermal equilibrium. Our analysis is based on calculating the partition functions of stiff polymers of variable lengths in the elastic regime. Our conclusion is that the length distribution of this self-assembled system follows closely the exponential distribution, except at the short length limit. We then discuss the implications of our results on the experimentally observed length distributions in amyloid fibrils.     

Mode hopping in single-mode microchip Nd：YAG lasers induced by optical feedback

The mode hopping phenomenon induced by optical feedback in single-mode microchip Nd：YAG lasers is presented. With optical feedback, mode hopping strongly depends on two factors： the ratio of external cavity length to intra-cavity length, and initial gains of the two hopping modes, When external cavity length equals an integral multiple of intracavity length, there is almost no mode hopping. However, if the external cavity length does not equal an integral multiple of intra-cavity length, mode hopping occurs. The ratio of external cavity length to intra-cavity length determines the position of two-mode hopping, The initial gains of the two hopping modes determine the corresponding peak values and oscillating periods of them in the intensity modulation curves.     

Endoscopy system for length measurement by manual pointing with an electromagnetic tracking sensor

We propose a practical and simple measurement function of three dimensional (3D) length for endoscopy based on triangulation using manually pointed correspondences. This system is a novel combination of conventional methods. 3D length information is useful for many medical purposes and the burden of manual procedures can be reduced by focusing on length. We employed a novel combination for length measurement, that is, a monocular endoscope with an electromagnetic tracking sensor. The proposed method can measure the length without any equipment for light projection and changing the current procedure of endoscopy. Our method is made more robust and reliable than the automatic correspondence techniques through the best use of the expertise of endoscopists. We developed a prototype system and evaluated its accuracy. From experimental results, we showed that the proposed method can measure the 3D length of static objects accurately as long as the measurement geometry is suitable.     

Influence of channel length on discharge performance of anode layer Hall thruster studied by particle-in-cell simulation

Hall thruster has the advantages of simple structure, high specific impulse, high efficiency, and long service life, and so on. It is suitable for spacecraft attitude control, North and South position keeping, and other track tasks. The anode layer Hall thruster is a kind of Hall thruster. The thruster has a longer anode area and a relatively short discharge channel.In this paper, the effect of the channel length on the performance of the anode layer Hall thruster is simulated by the PIC simulation method. The simulation results show that the change of the channel length has significant effect on the plasma parameters, such as potential and plasma density and so on. The ionization region mainly concentrates at the hollow anode outlet position, and can gradually move toward the channel outlet as the channel length decreases. The collision between the ions and the wall increases with the channel length increasing. So the proper shortening of the channel length can increase the life of the thruster. Besides, the results show that there is a best choice of the channel length for obtaining the best performance. In this paper, thruster has the best performance under a channel length of 5 mm.     

On the thermodynamics of relativistic ideal gases in the presence of a maximal length

We investigate the thermostatistics of relativistic ideal gases within the recently proposed deformed Heisenberg algebra (Perivolaropoulos, 2017), which includes a maximal length. By using the semiclassical method, the generalized canonical partition function is established and the modified thermodynamic functions are then calculated. It is explicitly shown that the maximal length, unlike the minimal length, modifies the equation of state of relativistic ideal gases. Furthermore, the ultrarelativistic and nonrelativistic regimes are discussed. In contrast to the minimal length corrections, the maximal length corrections do not depend on the considered regime. Such a result confirms that the effects of the maximal length and those of the minimal length are fundamentally different.     

Polarization decorrelation in optical fibers with randomly varying elliptical birefringence

Polarization decorrelation in single-mode fibers with randomly varying elliptical birefringence is studied. It is found that the effects of ellipticity on the polarization decorrelation length depend on the relative sizes of the beat length and the autocorrelation length of the birefringence fluctuations in the fiber. However, the evolution of the differential group delay remains unaffected by ellipticity.     

Scaling Behaviour of Diffusion Limited Aggregation with Linear Seed

We present a computer model of diffusion limited aggregation with linear seed. The clusters with varying linear seed lengths are simulated, and their pattern structure, fractal dimension and multifractal spectrum are obtained. The simulation results show that the linear seed length has little effect on the pattern structure of the aggregation clusters if its length is comparatively shorter. With its increasing, the linear seed length has stronger effects on the pattern structure, while the dimension D f decreases. When the linear seed length is larger, the corresponding pattern structure is cross alike. The larger the linear seed length is, the more obvious the cross-like structure with more particles clustering at the two ends of the linear seed and along the vertical direction to the centre of the linear seed. Furthermore, the multifractal spectra curve becomes lower and the range of singularity narrower. The longer the length of a linear seed is, the less irregular and nonuniform the pattern becomes.     

Relay propagation of partially coherent flattened Gaussian beam in turbulent atmosphere

Relay propagation of partially coherent flattened Gaussian–Schell beam in turbulent atmosphere has been studied. The analytical expresses of average intensity distribution at target are derived. The effects of spatial correlation length of initial and relay beam on the average intensity are analyzed in details. Study shows that the effects of the variation of spatial correlation length of relay beam are much larger than that of initial beam. The effects of spatial correlation length on relay propagation become smaller and smaller with the increase of structure constant. When the spatial correlation length is large and turbulence is strong, the effects of the variation of spatial correlation length on relay propagation are so small that can be neglected.     

非均匀地表空气动力学有效粗糙度的统计特征

利用基于大气边界层Monin-Obukhov相似理论、通量守恒和质量守恒原理设计的非均匀地表空气动力学有效粗糙度计算方案, 研究了3种不同地表类型情况下有效粗糙度的统计特征, 并分析了大气层结稳定度和粗糙变率对有效粗糙度的影响. 结果表明, 有效粗糙度总是大于面积加权平均粗糙度, 大部分情况下有效拖曳系数比平均拖曳系数大10%以上; 有效粗糙度虽然和大气层结稳定度有关, 但对粗糙变率更敏感, 粗糙变率加倍将使有效粗糙度相对变化百分比达到加倍前的4倍, 有效拖曳系数相对变化百分比达到加倍前的3倍. 因此, 非均匀下垫面的数值模式中, 不能简单地采用面积加权平均粗糙度, 需要采用能表示下垫面非均匀性综合效应的有效粗糙度. 关键词： 非均匀性 有效粗糙度 粗糙变率 层结稳定度     

激光陀螺腔长控制机构研究与改进

腔长控制机构在激光陀螺中通过控制腔长来保证激光陀螺工作光束的频率稳定,其对激光陀螺性能的提高有着重要意义。针对激光陀螺工作过程中,传统腔长控制机构的控制镜扭偏导致光束在腔中的位置偏移毛细孔的中心位置,引起腔内的散射、损耗发生变化从而影响陀螺性能及精度的问题,对激光陀螺腔长控制机构进行了研究,并设计了一种新的腔长控制机构以减小控制镜的扭偏对陀螺产生的影响。利用有限元分析法对新腔长控制机构进行了优化设计和仿真。试验表明,新的腔长控制机构减小了控制镜的扭偏,使得激光陀螺的零偏稳定性由0.7/h提高至0.3/h。     

衰荡腔测量中的腔参数选择

 基于谐振腔失调灵敏度参量随腔长的变化关系,提出了一种衰荡腔,它是由共焦腔将腔长缩短为原来的0.73得到的稳定腔。根据光束传输规律和失调腔矩阵方法,以及光腔衰荡法测量原理和曲线拟合方法,建立了腔长、腔镜角度失调下光腔衰荡法的反射率测量模型。通过数值模拟,研究了这种稳定衰荡腔中,腔微小失调对反射率测量结果的影响,并与相同失调情况下共焦衰荡腔的测量结果进行了对比分析。结果表明,这种稳定腔用作衰荡腔,测量结果受腔镜角度失调影响较大,而受腔长失调影响小;其长度较短,便于工程应用;衍射损耗较小,测量精度高。     

Planck length as the lower bound to all physical length scales

The effect of quantum fluctuations of gravity on the measurement of proper distances is considered. It is shown that, when the length scales are of the order of Planck length, the concept of a unique distance between points ceases to exist. It is also shown that the quantum expectation value of the proper length is bounded from below by Planck length in any space-time.This essay received the fifth award from the Gravity Research Foundation for the year 1984-Ed.     

The role of crystallographic angle in characterizing and modeling apatite fission-track length data

Recent experimental work on apatite fission-track length measurement has documented a number of factors that can exert a considerable influence on determinations of mean length. The principal source of length variation is anisotropy of annealing and etching behavior with respect to crystallographic angle. Procedural and environmental factors that influence which angular populations are preferentially sampled during measurement lead to variations in mean length that exceed standard statistical predictions. This paper evaluates the possibility of using c-axis projection to remove angular effects, and thus make length data more reproducible and informative.     

Relation of single-pulse characteristics to length of active rod

The population inversion as a function of rod length is examined for ruby and neodymium glass. The stored energy per unit length falls first on account of noise and then from oscillation due to reflection from the ends; this causes a maximum in the relation of radiated power to length. Estimates are given for the maximal stored energy, the optimum length, the maximum power output, and the limiting pulse length.