Design of undercuts and dipole stabilizer rods for the CPHS RFQ accelerator

As part of the design and machining of the RFQ accelerator in the Compact Pulsed Hadron Source (CPHS) project at Tsinghua University, the design process of the undercuts and dipole stabilizer rods is presented in this paper. In particular, the relationship between the inter-vane voltage slope and the local frequency of the undercut section is described quantitatively. With the identification of modes existing in the cavity, the specific parameters are optimized by the SUPERFISH and MAFIA codes. In addition, the water-cooling requirement of the dipole stabilizer rods is briefly discussed.     

Electrodeposition Techniques for Carbon Rod Flameless Atomic Absorption Analysis

Abstract

Two techniques involving electrodeposition of Cu on a carbon rod (CR) prior to atomic absorption (AA) analysis are described. The in situ technique involves electrodeposition from ul samples contained in the well of the CR in an attempt to decrease matrix effects. The bulk electrolysis technique allows preconcentration of Cu on the CR from very dilute metal ion solutions. Analysis of Cu in solutions as dilute as 1.6 × 10^?10 M (70 ml volume) appears possible.     

A high-power high-stability Q-switched green laser with intracavity frequency doubling using a diode-pumped composite ceramic Nd：YAG laser

We successfully obtain a high-average-power high-stability Q-switched green laser based on diode-side-pumped composite ceramic Nd:YAG in a straight plano-concave cavity. The temperature distribution in composite ceramic Nd:YAG crystal is numerically analyzed and compared with that of conventional Nd:YAG crystal. By using a composite ceramic Nd:YAG rod and a type-II high gray track resistance KTP (HGTR-KTP) crystal, a green laser with an average output power of 165 W is obtained at a repetition rate of 25 kHz, with a diode-to-green optical conversion of 14.68%, and a pulse width of 162 ns. To the best of our knowledge, both the output power and optical-to-optical efficiency are the highest values for green laser systems with intracavity frequency doubling of this novel composite ceramic Nd:YAG laser to date. The power fluctuation at around 160 W is lower than 0.3% in 2.5 hours.     

共晶基陶瓷复合材料的强度模型

根据细观结构内界面的强约束特性,通过纤维-基体内界面切应力确定了共晶陶瓷棒体的细观应力场.然后分析了两相界面处位错塞积产生的应力集中,获得基体内的最大应力,当最大拉应力等于基体理论断裂强度时,得到共晶棒体的断裂强度的解析表达式.考虑共晶陶瓷棒体长度和方位的随机性,根据概率理论得到共晶陶瓷基复合材料的宏观强度的理论模型.结果表明复合材料的宏观强度与亚微米纤维的直径和长度、以及亚微米纤维、基体、共晶陶瓷棒体的弹性常数有关.理论与实验结果十分接近,说明文中理论模型是合理的,同时证明了共晶界面对陶瓷复合材料的重要影响.     

Variational principle for a special Cosserat rod

In this paper, we describe the nonlinear models of a rod in three-dimensional space based on the Cosserat theory. Using the pseudo-rigid body method and variational principle, we obtain the motion equations of a Cosserat rod including shear deformations.     

可控旋转离散杆空间运动分析

基于理想爆轰假设和刚体运动学原理,建立了可控旋转离散杆空间运动模型。对不同尺寸、斜角的杆条进行空间运动状态分析,并和试验结果进行比较,结果表明该模型能较好地描述可控旋转离散杆空间运动状态,为可控旋转离散杆战斗部的设计提供参考。     

Nonlinear creep and ductile creep rupture of perfectly elastoplastic rods under tension

The paper is concerned with the problem of predicting nonlinear creep strains and time to ductile rupture of prismatic rods under constant tension. The material of the rod is assumed isotropic, homogeneous, and perfectly plastic. The problem is solved using models that take into account the change in the geometry of the rod during creep, the finiteness of the creep strains, and the effect of the initial and actual elastic strains. The conditions whereby the characteristic dimension of the rod tends to infinity and the accumulated and real strains in the viscous flow are limited are used as a failure criterion. The calculated results are compared with experimental data for a number of steels and alloys to formulate the conditions for the ductile rupture and embrittlement of metallic materials under uniaxial creep __________ Translated from Prikladnaya Mekhanika, Vol. 44, No. 4, pp. 120–133, April 2008.     

变截面弹性直杆纵振动分析的小波——DQ法

在经典微分求积(DQ)法基础上, 根据多分辨分析理论, 以尺度函数为基础构造插 值基函数, 形成了新的微分方程边值问题的求解方法------小波--DQ法, 并应用该方法分析了变截面弹性直杆的纵振动问题, 给出了其频率方程, 计算出了不同参数下固 支--固支, 自由--自由楔形直杆和锥形直杆的固有频率, 数值结果表明该方法是一个简单易行高精度的方法, 该方法可以推广应用于其他力学问题的数值分析.     

杆的初应力及识别

提出用数值特征描写杆中初应力的方法,建立初应力位形上的小变形动力学方程,由此讨论初应力对杆小变形力学行为的影响与用受初应力影响的附加变形来识别和测定初应力的数值特征的途径。     

Phase‐separated,conducting composites from polyaniline and benzobisthiazole rigid‐rod polymer

As an alternative method for processing polyaniline (PANI) from its conducting (protonated) state, vacuum casting of PANI from a methanesulfonic acid (MSA) solution provided films with electrical conductivity values of about 130–150 S/cm. In addition, we similarly prepared blended films of PANI · MSA and poly(p‐phenylene benzobisthiazole) (PBZT). This process eliminated the need for a subsequent protonation step and had the additional advantage that the conjugated PBZT may provide alternative conducting pathways. Conductivity values of the composite films ranged from 100 pS/cm to 124 S/cm, and the films displayed critical concentration behavior with a PANI threshold concentration of 2.75% and a critical exponent of 4. Transmission electron micrographs displayed phase‐separated regions with PANI forming a continuous network at high concentrations. Thermogravimetric analysis results demonstrated the thermal and thermooxidative stability advantage of the blends due to the PBZT component. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2539–2548, 2001