行波管周期永磁聚焦系统模拟软件的研制

 通过对行波管周期永磁聚焦系统(PPM)的理论分析,开发了2维模拟软件UESTC_PPM。该软件主要用于模拟轴对称的永磁结构,在圆柱坐标系下,采用有限差分的方法迭代求解磁钢内外任意位置处的磁感应强度分布。模拟了单磁环结构以及单周期结构,将结果与Ansoft Maxwell 3D的模拟结果进行了对比,结果表明：轴上、轴向以及径向磁感应强度的分布图均很接近,但UESTC_PPM软件耗时较短,验证了UESTC_PPM的正确性,并具有一定的精确度。     

丙酮分子n→π*跃迁光谱的平均溶剂静电势/分子动力学方法研究

采用量子力学/分子动力学方法研究了具体溶剂分子结构对溶质光谱行为的静电影响. 通过拟合溶质所处外电场和引入溶剂分子极化率, 考虑了溶质溶剂分子之间的相互极化效应, 得到合理的溶质和溶剂分子的电荷分布. 经过严格推导发现, 在传统的显溶剂模型中, 平衡和非平衡溶剂化能表达式均未考虑溶剂分子永久偶极弹簧能的贡献. 因此, 在正确计算永久偶极弹簧能的基础上, 重新建立了溶剂化能的表达式和新的吸收/发射光谱移动公式. 采用修改后的ASEP/MD程序, 计算得到了与实验值比较吻合的丙酮在水溶液中n→π*跃迁的光谱移动值, 验证了新公式的合理性.     

Towards the development of a fossil bone geochemical standard: an inter-laboratory study

Ten international laboratories participated in an inter-laboratory comparison of a fossil bone composite with the objective of producing a matrix and structure-matched reference material for studies of the bio-mineralization of ancient fossil bone. We report the major and trace element compositions of the fossil bone composite, using in-situ method as well as various wet chemical digestion techniques.For major element concentrations, the intra-laboratory analytical precision (%RSD_r) ranges from 7 to 18%, with higher percentages for Ti and K. The %RSD_r are smaller than the inter-laboratory analytical precision (%RSD_R; <15-30%). Trace element concentrations vary by ∼5 orders of magnitude (0.1 mg kg⁻¹ for Th to 10,000 mg kg⁻¹ for Ba). The intra-laboratory analytical precision %RSD_r varies between 8 and 45%. The reproducibility values (%RSD_R) range from 13 to <50%, although extreme value >100% was found for the high field strength elements (Hf, Th, Zr, Nb). The rare earth element (REE) concentrations, which vary over 3 orders of magnitude, have %RSD_r and %RSD_R values at 8-15% and 20-32%, respectively. However, the REE patterns (which are very important for paleo-environmental, taphonomic and paleo-oceanographic analyses) are much more consistent.These data suggest that the complex and unpredictable nature of the mineralogical and chemical composition of fossil bone makes it difficult to set-up and calibrate analytical instruments using conventional standards, and may result in non-spectral matrix effects. We propose an analytical protocol that can be employed in future inter-laboratory studies to produce a certified fossil bone geochemical standard.     

新一代永磁型磁共振成像系统及其医学应用

简述了世界磁共振成像技术的发展趋势,分析了永磁型共振成像系统的常见不足及其产生的物理原因,据此,提出了解决这些问题的方法,同时,介绍了解决这些问题之后开发出的新一代永磁型磁振成像系统Ｏｐｅｎ Ｍａｒｋ２０００的特点及其在医学上的应用。     

Exact Recursive Calculation of Circulant Permanents: A Band of Different Diagonals inside a Uniform Matrix

We present a finite-order system of recurrence relations for the permanent of circulant matrices containing a band of k any-value diagonals on top of a uniform matrix (for k=1,2 and 3) and the method for deriving such recurrence relations, which is based on the permanents of the matrices with defects. The proposed system of linear recurrence equations with variable coefficients provides a powerful tool for the analysis of the circulant permanents, their fast, linear-time computing; and finding their asymptotics in a large-matrix-size limit. The latter problem is an open fundamental problem. Its solution would be tremendously important for a unified analysis of a wide range of the nature’s ♯P-hard problems, including problems in the physics of many-body systems, critical phenomena, quantum computing, quantum field theory, theory of chaos, fractals, theory of graphs, number theory, combinatorics, cryptography, etc.     

插入式永磁低速同步电机非奇异终端滑模观测器设计

提出一种以d-q同步旋转坐标系下, 电流为观测对象的插入式永磁同步电机的非奇异高阶终端滑模观测器, 用来获得高性能矢量控制系统所必需的电机转子位置及速度信息. 采用非奇异终端滑模控制, 提高了观测器的动态响应速度及鲁棒性, 利用高阶滑模控制技术的特性, 有效地抑制了传统滑模控制的抖振现象. 同时给出了转速环及电流环调节器的参数设计方法, 转速环调节器采用积分反馈算法, 电流环调节器使用前馈解耦内模控制技术 ,参数在线调整简单. 将该算法应用到2 MW永磁同步低速电机无传感器控制系统中, 实验结果表明, 该方法能够准确计算出电机的位置和速度, 使系统具有良好的稳态精度和动态性能.     

Gelation in Multiple Link System

The critical point theory is generalized to include gelation in multilink system with f functional units and J junction points. The equations derived include, as special cases, the cyclotrimerization model of J = 3, and the R–A_f model of J = 2. The theory is applied to the recent observation of the cyclotrimerization of bisphenol‐A dicyanate. The theoretical prediction agrees exactly with the Stutz‐Simak observation, D_c = 0.504, and accords with the Georjon‐Galy‐Pascault observation, giving a confirmation of the physical soundness of the theory. Under the smoothness assumption, we derive post‐gelation relationships with loop formation, the result suggesting the formation of permanent sol molecules that resist being absorbed into gel phase throughout an entire reaction process.

Representation of binary branching.     

A compact permanent‐magnet system for measuring magnetic circular dichroism in resonant inelastic soft X‐ray scattering

A compact and portable magnet system for measuring magnetic dichroism in resonant inelastic soft X‐ray scattering (SX‐RIXS) has been developed at the beamline BL07LSU in SPring‐8. A magnetic circuit composed of Nd–Fe–B permanent magnets, which realised ～0.25 T at the center of an 11 mm gap, was rotatable around the axis perpendicular to the X‐ray scattering plane. Using the system, a SX‐RIXS spectrum was obtained under the application of the magnetic field at an angle parallel, nearly 45° or perpendicular to the incident X‐rays. A dedicated sample stage was also designed to be as compact as possible, making it possible to perform SX‐RIXS measurements at arbitrary incident angles by rotating the sample stage in the gap between the magnetic poles. This system enables facile studies of magnetic dichroism in SX‐RIXS for various experimental geometries of the sample and the magnetic field. A brief demonstration of the application is presented.     

Design of a new compact THz source based on Smith-Purcell radiation

In recent years, people are dedicated to the research work of finding compact THz sources with high emission power. Smith-Purcell radiation is qualified for the possibility of coherent enhancement due to the effect of FEL mechanism. The compact experiment device is expected to produce hundreds mW level THz ray. The electron beam with good quality is provided under the optimized design of the electron gun. Besides, the grating is designed as an oscillator without any external feedbacks. While the beam passes through the grating surface, the beam bunching will be strong and the second harmonics enhancement will be evident, as is seen from the simulation results.