Universal function for the brilliance of undulator radiation considering the energy spread effect

Angular and spatial profiles of undulator radiation have been investigated to derive a universal function that evaluates the brilliance of undulator radiation and takes into account the effects of electron beam emittance and energy spread. It has been found that the effects of energy spread on the angular divergence and source size can be expressed by simple analytic expressions, and a universal brilliance function has been derived by convolution with the electron beam distribution functions. Comparisons with numerical results have been carried out to show the validity and applicability of the universal function.     

太阳爆发日珥内双向喷流事件的紫外光谱研究

太阳双向喷流事件是过渡区重要的小尺度现象之一。双向喷流事件的光谱特征是强的展宽和非高斯形状。当双向喷流事件发生时,光谱像的红、蓝两翼分别或者同时明显增强,其相应的多普勒速度可达100 km·s-1以上。双向喷流事件的平均尺度约1 800 km, 寿命约60 s。双向喷流事件出现在磁对消区附近,且其速度与当地的阿尔芬速度相当,普遍认为其产生机制为小尺度快速磁重联。对其系统、全面地研究始于SOHO时代。SOHO/SUMER具有高时空和谱分辨率、宽的谱线覆盖,其观测的光谱数据为探究双向喷流事件提供了有力的光谱学诊断工具。双向喷流事件及其他过渡区小尺度现象的相互联系已被广泛研究,但双向喷流事件与日珥及其精细结构的关系研究还很少。文章通过SOHO/SUMER的Si Ⅲ谱线的定点观测,再现了爆发日珥演化的强度﹑多普勒速度和宽度演化图。通过Si Ⅲ谱线分析,找出宽度大于三个标准偏差的Si Ⅲ谱线,然后进行视像筛选出双向喷流事件,最终在爆发日珥中诊断出多个双向喷流事件,且大多数的双向喷流事件以准周期20 min重复出现在爆发日珥的中心区域。通过讨论,认为日珥中心磁流管之间的磁重联导致了双向喷流事件的重复出现,双向喷流事件产生的高速等离子体流可能是日面物质抛射的一部分,或是跟随日面物质抛射的太阳风的一部分。     

Mesure des forces d'oscillateur par absorption dans un jet atomique—II. force d'oscillateur de la transition 1P1-1S0 du zinc (λ = 2139 Å)

The oscillator strength of the ultraviolet resonance line of ZnI ($\text{λ = 2139}\text{A}\text{?}$) has been measured by observing the absorption of this line in an atomic beam whose density was directly determined. Experimental profiles of the absorbed line are compared with calculated profiles obtained by convolution with the Fabry-Perot apparatus function. The absolute ?-value of the ZnI line (λ 2139 Å) was found to be 1·45. This result is compared with those of other investigations.     

一种求解锂离子电池单粒子模型液相扩散方程的新方法

电解液中的锂离子浓度表达是锂离子电池电化学模型求解的基本任务之一.为了平衡单粒子模型的液相动态性能和计算效率,假设反应仅发生在集电极和电解质界面上,为此,提出一种基于液相扩散方程无穷级数解析解的界面浓度求解新方法.在恒流工况下,利用数列单调收敛准则将解析解转化为一个收敛和函数.在动态工况下,将该解析解简化为输入与和函数的无限离散卷积.利用和函数随时间单调衰减并收敛至零的特性对其进行截断,从而得到有限离散卷积求解算法.对比专业有限元分析软件,该方法在恒流工况和动态工况下均能以较少的计算时间获得相当好的精度.而且,该方法仅有一个配置参数.因此,所提方法将有效减小应用于实时电池管理系统上的电化学模型计算负担.     

一种求解锂离子电池单粒子模型液相扩散方程的新方法

电解液中的锂离子浓度表达是锂离子电池电化学模型求解的基本任务之一.为了平衡单粒子模型的液相动态性能和计算效率,假设反应仅发生在集电极和电解质界面上,为此,提出一种基于液相扩散方程无穷级数解析解的界面浓度求解新方法.在恒流工况下,利用数列单调收敛准则将解析解转化为一个收敛和函数.在动态工况下,将该解析解简化为输入与和函数的无限离散卷积.利用和函数随时间单调衰减并收敛至零的特性对其进行截断,从而得到有限离散卷积求解算法.对比专业有限元分析软件,该方法在恒流工况和动态工况下均能以较少的计算时间获得相当好的精度.而且,该方法仅有一个配置参数.因此,所提方法将有效减小应用于实时电池管理系统上的电化学模型计算负担.     

Broadening of resonance profiles

There are many cases in experimental physics where narrow resonances are observed under conditions in which they are broadening by an apparatus function. In the present work we give data to help in determining parameters for resonances under these circumstances. Two separate apparatus functions are assumed, namely those with Gaussian and triangular shapes, and the results are presented for the convolution of these shapes with various resonance profiles.     

太阳极区冕洞内小尺度结构的紫外光谱研究

SOHO/SUMER太阳紫外光谱仪的N Ⅳ谱线观测到太阳南极区冕洞内存在许多小尺度结构,其空间尺度约1～几角秒,寿命尺度约1～几min。小尺度结构沿狭缝方向呈条状,视向多普勒速度可至几十km·s-1。在有的南极区冕洞区域内,小尺度结构的视向多普勒速度呈红、蓝移准周期性交错分布,持续时间长达100 min。部分小尺度结构在同一观测窗口的高温Ne ⅤⅢ谱线还可清晰显现。有的小尺度结构在Ne ⅤⅢ速度演化图的时间和位置与N Ⅳ 谱线速度图基本一致,但它们在Ne ⅤⅢ速度演化图中更延展和弥散。N Ⅳ紫外光谱显示部分小尺度结构谱线呈现非高斯形状,谱线两翼速度可达150 km·s-1,与太阳过渡区爆发事件的光谱特征相似。太阳过渡区爆发事件常出现在宁静区,SOHO/SUMER太阳紫外光谱仪的N Ⅳ谱线显示在南极区冕洞也可产生爆发事件,且具有较强的动力学特征。     

Correction of temperature influence on the wind retrieval from a mobile Rayleigh Doppler lidar

A mobile Rayleigh Doppler lidar based on double-edge technique is implemented for simultaneously observing wind and temperature at heights of 15 km-60 km away from ground.Before the inversion of the Doppler shift due to wind,the Rayleigh response function should be calculated,which is a convolution of the laser spectrum,Rayleigh backscattering function,and the transmission function of the Fabry-Perot interferometer used as the frequency discriminator in the lidar.An analysis of the influence of the temperature on the accuracy of the Une-of-sight winds shows that real-time temperature profiles are needed because the bandwidth of the Rayleigh backscattering function is temperature-dependent.An integration method is employed in the inversion of the temperature,where the convergence of this method and the high signal-to-noise ratio below 60 km ensure the accuracy and precision of the temperature profiles inverted.Then,real-time and on-site temperature profiles are applied to correct the wind instead of using temperature profiles from a numerical prediction system or atmosphere model.The corrected wind profiles show satisfactory agreement with the wind profiles acquired from radiosondes,proving the reliability of the method.     

A two-temperature model of optical excitation of acoustic waves in conductors

A two-temperature model of optical excitation of acoustic pulses in conductors has been developed. According to this model, the energy of light at first is absorbed by free carriers and only then is the optical pulse energy transferred to long-wavelength phonons of the conductor lattice. It is shown that the shape of the acoustic pulse excited by a laser in conductors can be presented as a convolution of the laser pulse envelope and the transfer function. An analytical dependence of the transfer function on time is derived.     

Understanding how both the partitions of a bipartite network affect its one-mode projection

It is a well-known fact that the degree distribution (DD) of the nodes in a partition of a bipartite network influences the DD of its one-mode projection on that partition. However, there are no studies exploring the effect of the DD of the other partition on the one-mode projection. In this article, we show that the DD of the other partition, in fact, has a very strong influence on the DD of the one-mode projection. We establish this fact by deriving the exact or approximate closed-forms of the DD of the one-mode projection through the application of generating function formalism followed by the method of iterative convolution. The results are cross-validated through appropriate simulations.     

Influence of spectral resolution on absorption-line profiles

The convolution of the instrumental function with the initial line profile resulting in the observed intensity distribution has been analyzed by computer studies. Detailed information about its influence on half-width and total absorption is obtained for a wide range of characteristic parameters.     

Theory of vibronic optical spectra of impurity centers with violation of the Condon approximation

Expressions for non-Condon generating functions of absorption and luminescence of optical centers in crystals at zero temperature have been obtained in the adiabatic approximation. A solution to the Schrödinger equation for an electronic subsystem has been considered to the first order of the perturbation theory for a vibronic interaction linear in normal coordinates of the vibrational subsystem. The non-Condon form function of the optical transition has been obtained in the form of a convolution operator acting on the normalized Condon form function. It has been proved that, if the optical transition is forbidden in the Condon approximation due to symmetry, the non-Condon form function does not contain a zero-phonon line and the non-Condon form functions of absorption and luminescence are symmetric.     

Single exposure photography applied to a slow flow field

A speckle photography technique has been applied to measuring the velocity profiles of laminar and turbulent flow through pipes of circular cross-section. A single exposure photography technique has been used to visualize slow fluid flow. The fluids used were seeded with tracer particles whose size range from 20 to about 120 μm in diameter. A mathematical expression representing the recorded intensity is presented. A single exposure with a long exposure time was taken on a holographic film material. The recorded intensity was represented by the convolution product of the image formed and a rectangular function representing a one-dimensional continuous motion. The analysis shows that the intensity distribution of the Fourier spectrum of the diffracted image follows a sinc² function on a noise background representing the scattered light of the tracer particles.     

Faceting and stability of smectic A droplets on a solid substrate

It is shown that a smectic A droplet deposited on a solid substrate treated for strong homeotropic anchoring is faceted at the top in spite of the fact that there are no steps at the free surface, but instead edge dislocations in the bulk. The radius of the facet and the full profile of the curved part of the droplet are determined as a function of the temperature in the vicinity of a nematic-smectic A phase transition. It is shown that the observed profiles do not correspond to the actual equilibrium shape, but to metastable configurations close to their point of marginal stability. In addition, we predict that the profiles must be different for a given temperature depending on whether the droplet has been heated or cooled down to reach this temperature. Finally, we discuss the problem of the formation of giant dislocations in big droplets (Grandjean terraces).     

Ab-initio study of phase transition and momentum density in PbTe

In this article, the high-pressure structural phase transition and electron momentum density in PbTe have been studied by means of first-principles total energy calculations which are based on the linear combination of atomic orbitals method within generalized gradient approximation. It is observed that the stable phase of PbTe is rocksalt (B1) type and it transforms to an orthorhombic Pnma (B27, FeB type) structure at 6.77?GPa. Further, structural phase transition from the Pnma phase to the cesium chloride (B2) phase has been observed at 13.04?GPa. The anisotropies in theoretical directional Compton profiles indicate larger occupied states along the [100] direction. On the basis of equal-valence-electron-density profiles, it is found that PbTe shows less ionicity as compared to PbS and PbSe.     

Modeling the nadiral low-frequency pulse return of one-dimensionally rough surfaces

Measurements of radar pulse return waveforms are known to provide information on properties of the observed surface, and are commonly used in oceanographic altimetry. In such applications, the convolution model (also called the “Brown model”) is widely applied for waveform analysis. This model describes pulse return waveforms as a multiple convolution of the “flat surface impulse response”, the surface's height probability density function, and the radar's point target response. The flat surface impulse response is typically determined by an integration of scattering contributions from incremental surface elements weighted by a geometrical optics (GO) prediction of the normalized radar cross-section of the elemental surfaces.

Recent interest in the analysis of pulse return waveforms at VHF and lower frequencies for ice sheet sensing applications motivate reconsideration of the convolution model. While the ultimate goal of this effort is the development of a model to be utilized for interpreting VHF radar measurements over ice sheets, it is important first to establish the validity of the convolution model for these applications. Such an investigation, which involves the comparison of convolution model predictions with those of a method that does not require a separation of surface length-scales into “elemental” and large-scale regions, is most easily performed for one-dimensional surfaces.

This paper describes a derivation of the convolution model for one-dimensionally rough surfaces that is applicable at low frequencies, primarily through the replacement of GO surface scattering coefficients with those of a physical optics theory. The method is validated by comparing its predictions with a Monte Carlo physical optics approach. Results show the convolution model to provide reasonable estimates of the pulse return waveform, so that a similar method can be utilized to develop a convolution model for two-dimensional surface pulse return waveforms in ice-sheet sensing applications. The results also suggest the possibility of retrieving surface profile statistical information from waveform measurements.     

A system for simulating room acoustical environments for one’s own voice

The real-time simulation of room acoustical environments for one’s own voice using generic software has been difficult until very recently due to the computational load involved: requiring real-time convolution of a person’s voice with a potentially large number of long room impulse responses. This paper describes a software-based solution that accomplishes real-time convolution with head-tracking to simulate the effect of room acoustical environments on the sound of one’s own voice, using binaural technology. Actual rooms are characterized by measuring the room impulse response from the mouth to ears of the same head (oral binaural room impulse response, OBRIR). By repeating this process at 2° yaw increments for a given head position, the rooms are binaurally scanned around a given position to obtain a collection of OBRIRs, which is then used by the software-based simulation system. In the simulated rooms, a person equipped with a near-mouth microphone and near-ear loudspeakers can speak or sing and hear their voice, as it would sound in the recorded rooms, while physically being in an anechoic room. By continually updating the person’s head orientation using head-tracking, the corresponding OBRIR is chosen for convolution with their voice. The system described in this paper achieves the low latency that is required to simulate nearby reflections, and it can perform convolution with long room impulse responses.     

New definition for the hadronic contribution to the muon anomalous magnetic moment

A new definition is proposed for the hadronic contribution to the muon anomalous magnetic moment that is based on the inclusion of the effects of vacuum polarization by leptons into the cross section for one-photon annihilation of a lepton pair into hadrons. The formula for the hadronic contribution includes the convolution of the measured cross section for annihilation into hadrons with a certain standard function. This remark concerns radiative correction to this function. A particular form has been proposed for this correction. It has been shown that the use of the new function makes it possible to reduce the uncertainty in such contributions due to radiative correctioins to δa _h/a _h ～ 10^?4.     

应用一维变分法反演GPS掩星大气温湿廓线

GPS掩星观测的折射率是大气温度、湿度状态的函数, 应用一维变分方法 (1DVAR) 可以从折射率资料中同时反演出大气温、湿度廓线, 利用COSMIC 2011年中国区域掩星观测数据对这一方法进行了测试, 背景场采用ECMWF大气廓线, 反演结果与相匹配的探空观测有较好一致性. 重点研究了一维变分反演方法中非理想气体效应 (non-ideal effect) 对温度、湿度反演误差的影响, 不同月份的比较结果表明, 非理想气体效应对掩星反演大气廓线是一种系统性影响, 考虑这一效应可对温度反演改进0.1 K的偏差 (bias), 对比湿可改进约0.5%偏差. 掩星资料作为数值天气预报资料同化中少数无需偏差改正的卫星遥感资料, 非理想气体效应改正是无疑是非常重要的, 此外, 考虑这一效应对掩星资料的气候应用也有重要价值. 关键词： 一维变分 掩星 非理想气体效应     

Single scattering profile from small-angle scattering data affected by multiple scattering: use of a basis function set

Present work involves extraction of single-scattering profile from small-angle scattering data, affected by multiple scattering, using an existing model-independent algorithm [Mazumder et al., Physica B 241–243, 1222 (1998), Mazumder et al., J. Appl. Crystallogr. 36, 840 (2003)]. It is shown that implementation of the algorithm becomes effective by representing the multiple scattering profiles in terms of a set of basis function whose form of Hankel transformed pair is known analytically. In the present paper, the methodology has been presented by introducing a Gaussian basis set and has been tested for various simulated profiles. The performance of this methodology has also been tested for scattering profiles having complex internal features and moderate statistical noise. Subsequently, the same has been applied for experimental small-angle neutron scattering data.