阿贝成像原理与空间滤波实验教学

提出了一套新的阿贝成像原理和空间滤波实验教学方案,该方案能够较全面地实现数据测量、低通滤波、高通滤波和方向滤波.并采用改进的实验装置和测量方法进行实验,操作简单,数据准确,实验效果明显.     

液体多脉冲及二维FT-NMR实验的乘积算符描述的计算机模拟

本文报道了利用乘积算符方法分析多脉冲及二维FT-NMR实验的模拟程序PROPER-MT.该程序对分析弱耦合I_mS_n(I=1/2;S=(1)/2;1 ≤ m十n<4)自旋体系实验脉冲序列是普遍适用的;它可给出实验过程中体系任何时刻算符的解析表达式.用PROPER-MT程序对一些典型的多脉冲及二维FT-NMR实验进行了模拟,特别对多量子滤波及多自旋滤波脉冲序列进行了分析计算,得到了预期的结果.     

弗兰克-赫兹实验的计算机模拟

编制了蒙特卡罗仿真程序,并介绍了其原理.该程序可理论再现弗兰克-赫兹实验中电子与氩原子的相互作用过程,定量评估各碰撞、各种运行参量对结果的影响.该模拟程序可以用来解决学生对实验产生的疑惑,也可以为改进实验方案提供理论指导.     

用于OADM的集成声光可调谐滤波器的性能分析

利用模式耦合理论分析了声光模式转换.并对声光可调谐滤波器的滤波带宽、调谐范围、驱动功率等性能参数进行了分析计算.设计制作滤波器时,首先在保证滤波带宽的前提下,考虑调谐范围、驱动功率以及加工工艺的要求.对其应用于OADM中存在的旁瓣和串扰问题进行了初步讨论.设计完成中心波长在1.55 μm,滤波带宽为1.2 nm左右,波长调谐范围大于150 nm,低驱动功率的IAOTF.     

高能物理实验中一个在线监测程序KGeneral

KGeneral是在ROOT程序包下开发的一个高能物理实验在线监测程序.它读取KLOEGlobal程序的文件,显示KLOE实验的探测器、电子学线路、DAQ重建数据的各物理量和加速器运行状态的参数,并定时刷新,以跟踪实验当前状态和数据质量.KGeneral程序设有Custom选项,可以把用户感兴趣的图形在同一画板上显示.KGeneral程序也有纵向和横向的Slider,以便用户放大图形,更好地观察参数图形的细节.     

基于GUI的空间滤波实验的计算机模拟

分析了空间滤波实验的原理,利用Matlab软件编写了带有图形用户界面(GUI)的计算机模拟程序.该程序能够准确模拟实际实验过程,在功能上还对其进行了扩充,对于提高空间滤波实验的教学效果起到很好作用.     

光学实验计算机仿真平台的构建

运用MAILAB构建了-个光学实验仿真平台,实现了包括基础光学中干涉和衍射、信息光学中的光学图像处理以及激光实验的仿真.并利用GUI设计了人机友好的图形用户界面,最后通过mcc编译生成可脱离MATLAB环境运行的可执行文件.该平台可移植性、可扩展性强,用户可直接进行实验项目的选取,实验参数的灵活设置以及实验结果的对比分...     

上海光源储存环横向反馈系统模拟计算

在同步辐射光源中, 阻抗壁不稳定性是一个很严重的问题. 要保证储存环在高流强下正常运行, 就需要安装一套横向反馈系统. 为了了解在横向反馈作用下束流的动力学性质,建立了一套横向反馈模拟计算程序. 并用该程序模拟计算了上海光源储存环横向反馈系统在闭轨误差(COD)、束流位置探测器读数误差以及梳状滤波等条件改变下的反馈效果.     

一种通用的MRI计算机模拟软件

报道一套基于解释脉冲程序的MRI的计算机模拟软件,可适用于任意脉冲序列成象方法的计算机模拟,该软件包括成象物理模型的建立,成象物理过程的模拟,基于K空间的时域FID信号的重组,多维傅立叶交换重建图象,多维滤波反投影重建图象.图象显示等功能模块;分析了成象的物理过程的基本原理和软件的设计思想.并以GE成象和SEPI快速成象方法为例进行了模拟,实现了图象重建.     

窄带集成声光可调谐滤波器的研制

利用模式耦合理论分析了声光模式转换,并对声光可调谐滤波器的滤波带宽、调谐范围、驱动功率等性能参数进行分析计算。设计并制作出窄带集成声光可调谐滤波器(IAOTF)样品,搭建相应的IAOTF测试平台,得到中心波长在1.55μm,滤波带宽达到0.85 nm,波长调谐范围达到80 nm,驱动功率低于40mW的IAOTF。并对进一步压缩滤波带宽和旁瓣效应提出了解决途径。     

Kinetic modeling of multiphase flow based on simplified Enskog equation

A new kinetic model for multiphase flow was presented under the framework of the discrete Boltzmann method (DBM). Significantly different from the previous DBM, a bottom-up approach was adopted in this model. The effects of molecular size and repulsion potential were described by the Enskog collision model; the attraction potential was obtained through the mean-field approximation method. The molecular interactions, which result in the non-ideal equation of state and surface tension, were directly introduced as an external force term. Several typical benchmark problems, including Couette flow, two-phase coexistence curve, the Laplace law, phase separation, and the collision of two droplets, were simulated to verify the model. Especially, for two types of droplet collisions, the strengths of two non-equilibrium effects, {\overline{D}}_2^{*} and {\overline{D}}_3^{*} , defined through the second and third order non-conserved kinetic moments of (f-f^{eq}), are comparatively investigated, where f\left(f^{eq}\right)is the (equilibrium) distribution function. It is interesting to find that during the collision process, {\overline{D}}_2^{*} is always significantly larger than {\overline{D}}_3^{*}, {\overline{D}}_2^{*} can be used to identify the different stages of the collision process and to distinguish different types of collisions. The modeling method can be directly extended to a higher-order model for the case where the non-equilibrium effect is strong, and the linear constitutive law of viscous stress is no longer valid.     

Self-organized criticality in multi-pulse gamma-ray bursts

The variability in multi-pulse gamma-ray bursts(GRBs)may help to reveal the mechanism of underlying processes from the central engine.To investigate whether the self-organized criticality(SOC)phenomena exist in the prompt phase of GRBs,we statistically study the proper ties of GRBs with more than 3 pulses in each burst by fitting the distributions of several observed physical variables with a Markov Chain Monte Carlo approach,including the isotropic energy E_iso,the duration time T,and the peak count rate P of each pulse.Our sample consists of 454 pulses in 93 GRBs observed by the CGRO/BATSE satellite.The best-fitting values and uncertainties for these power-law indices of the differential frequency distributions are:α_E^d=1.54±0.09,α_T^d=1.82_-0.15^+0.14andα_P^d=2.09_-0.19^0.18,while the power-law indices in the cumulative frequency distributions are:α_E^c=1.44_-0.10^+0.08,α_T^c=1.75_-0.13^0.11andα_P^c=1.99_-0.19^+0.16.We find that these distributions are roughly consistent with the physical framework of a Fractal-Diffusive,Self^Organized Criticality(FD-SOC)system with the spatial dimension S=3 and the classical diffusionβ=1.Our results support that the jet responsible for the GRBs should be magnetically dominated and magnetic instabilities(e.g.,kink model,or tearing-model instability)lead the GRB emission region into the SOC state.     

Evolution law of Wigner function in laser process

Based on the density operator’s o perator-sum representation r ecently obtained by Fan and Hu for a laser process (Opt. Commun., 2008, 281: 5571; Opt. Commun., 2009, 282: 932; Phys. Lett. B, 2008, 22: 2435), we derive the evolution law of Wigner operator, the law is concisely expressed in the normally ordered formΔ(α,α*,t)=Tπ:exp?[-2T(a?e-(κ-g)t-α*)-(ae-(k-g)t-α)] :, where g and κ are the cavity gain and the loss, respectively, and T≡ (κ-g )(κ+g-2ge^{-2(κ-g) t})^-1. When t=0,Δ(α,α,t)→1π : exp?[-2(a?-α*)-(a-α)] :, which is the initial Wigner operator. Using this formalism the evolution law of Wigner functions in laser process can be directly obtained.     

Gluon number fluctuations and diffusive scaling effect

The diffusive scaling is studied based on pomeron loop equations in the fixed coupling case. At Y?YDS, the gluon number fluctuations become important, the geometric scaling is replaced by the diffusive scaling. In the diffusive scaling regime, the deep inelastic scattering (DIS) total scattering cross-section is a function of single variable ln?[1/(r2Qs2(X))]/DY. We show that the deep inelastic scattering experimental data lie on a single curve, which seems to indicate the existence of the diffusive scaling phenomenology in the deep inelastic scattering.     

On the entangled fractional squeezing transformation

We propose an entangled fractional squeezing transformation (EFrST) generated by using two mutually conjugate entangled state representations with the following operator: e-iα(a1?a2?+a1a2)eiπa2?a2; this transformation sharply contrasts the complex fractional Fourier transformation produced by using e-iα(a1?a2?+a2?a2)eiπa2?a2 (see Front. Phys. DOI 10.1007/s11467-014-0445-x). The EFrST is obtained by converting the triangular functions in the integration kernel of the usual fractional Fourier transformation into hyperbolic functions, i.e., tanα → tanhα and sinα → sinhα. The fractional property of the EFrST can be well described by virtue of the properties of the entangled state representations.     

Relation between gravitational mass and baryonic mass for non-rotating and rapidly rotating neutron stars

With a selected sample of neutron star(NS)equations of state(EOSs)that are consistent with the current observations and have a range of maximum masses,we investigate the relations between NS gravitational mass Mg and baryonic mass and the relations between the maximum NS mass supported through uniform rotation(Mmax)and that of nonrotating NSs(Mtov).We find that for an EOS-independent quadratic,universal transformation formula(Mb=Mg+A×M^2/g),the best-fit A value is 0.080 for non-rotating NSs,0.064 for maximally rotating NSs,and 0.073 when NSs with arbitrary rotation are considered.The residual error of the transformation is?0.1M⊙ for non-spin or maximum-spin,but is as large as?0.2M⊙ for all spins.For different EOSs,we find that the parameter A for non-rotating NSs is proportional to R^-1/1.4(where R1.4 is NS radius for 1.4M⊙ in units of km).For a particular EOS,if one adopts the best-fit parameters for different spin periods,the residual error of the transformation is smaller,which is of the order of O.O1M⊙ for the quadratic form and less than O.O1M⊙ for the cubic form(Mb=Mg+A1×M^2/g+A2×M^3/g).We also find a very tight and general correlation between the normalized mass gain due to spin △m≡(Mmax-MTOV)MTOV and the spin period normalized to the Keplerian period P,i.e.,log10 △m=(-2.74±0.05)log10 P+log10(0.20±0.01),which is independent of EOS models.These empirical relations are helpful to study NS-NS mergers with a long-lived NS merger product using multi-messenger data.The application of our results to GW170817 is discussed.     

Diverse magnetism in stable and metastable structures of CrTe

In this paper, we systematically investigated the structural and magnetic properties of CrTe by combining particle swarm optimization algorithm and first-principles calculations. By considering the electronic correlation effect, we predicted the ground-state structure of CrTe to be NiAs-type (space group P6₃/mmc) structure at ambient pressure, consistent with the experimental observation. Moreover, we found two extra meta-stable Cmcaand R\overline{3}m structures which have negative formation enthalpy and stable phonon dispersion at ambient pressure. The Cmcastructure is a layered antiferromagnetic metal. The cleaved energy of a single layer is 0.464 J/m² , indicating the possible synthesis of CrTe monolayer. The R\overline{3}m structure is a ferromagnetic half-metal. When external pressure is applied, the ground-state structure of CrTe transitions from P63/mmc structure to R\overline{3}m structure at a pressure of 34 GPa, then to R\overline{3}m structure at 42 GPa. We thought these results help to motivate experimental studies of the CrTe compounds in the application of spintronics.     

Spatial modulation of unitary impurity-induced resonances in superconducting CeCoIn5

Motivated by recent experimental progress in high-resolution scanning tunneling microscopy (STM) techniques, we investigate the local quasiparticle density of states around a unitary impurity in the heavy-fermion superconductor CeCoIn₅. Based on the T -matrix approach we obtain a sharp nearly zero-energy resonance state in the strong impurity potential scattering localized around the impurity and find qualitative differences in the spatial pattern of the tunneling conductance modulated by the nodal structure of the superconducting gap. These unique features may be used as a probe of the superconducting gap symmetry and, in combination with further STM measurements, may help to confirm the dx2−y2 pairing in CeCoIn₅ at ambient pressure.     

Subgroups of index 4 of the 2-dimensional space groups

There are 281 subgroups of index 4 for the 17 types of 2-dimension space groups: p1:7, p2:31, pm:19, pg:7, cm:11, p2mm:67, p2mg:23, p2gg:11, c2mm:31, p4:11, p4mm:31, p4gm:11, p3:4, p3m1:4, p31m:4, p6:4, p6mm:5. Every subgroup has been identified by its conventional cell disposition with respect to the conventional cell of the starting group. These subgroups may be arranged in 96 automorphism classes and 184 conjugation classes according to their starting groups.     

Conditions for ponderomotive resonances in the Kapitza–Dirac effect

By applying a nonperturbative quantum electrodynamic theory, we study ponderomotive resonances when an electron beam is scattered by a standing photon wave. Our study shows that the ponderomotive parameter u_p, the ponderomotive energy per laser-photon energy, for each of the two traveling laser modes possesses a minimum value ℏω/(mec2). Ponderomotive resonances occur only when the ratio of the laser photon energy to the electron rest-mass energy is a fraction, where the denominator is twice the square of a positive integer and the numerator is the total ponderomotive number, which is also a positive integer.