Nickel‐Catalyzed Barton Decarboxylation and Giese Reactions: A Practical Take on Classic Transforms

Two named reactions of fundamental importance and paramount utility in organic synthesis have been reinvestigated, the Barton decarboxylation and Giese radical conjugate addition. N ‐hydroxyphthalimide (NHPI) based redox‐active esters were found to be convenient starting materials for simple, thermal, Ni‐catalyzed radical formation and subsequent trapping with either a hydrogen atom source (PhSiH₃) or an electron‐deficient olefin. These reactions feature operational simplicity, inexpensive reagents, and enhanced scope as evidenced by examples in the realm of peptide chemistry.     

Structural versatility and electrochemical properties of four copper(II) complexes based on 1<Emphasis Type="Italic">H</Emphasis>-indazole-3-carboxylic acid

Copper (Cu)(II) complexes were synthesized by Ind-3-COOH combined with N-containing auxiliary ligands via a combinatorial strategy involving hydrothermal and solvent-evaporation method. The synthesized complexes had the following formulas: [Cu(Ind-3-COO)₂] (1), [Cu(PHEN)(Ind-3-COO)]₂·2H₂O (2), [Cu₂(DPP)(Ind-3-COO)₂(H₂O)]·H₂O, (3) and [Cu(BPY)(Ind-3-COO)₂]·4H₂O (4). Meanwhile, the symbol abbreviations were listed as follows: Ind-3-COOH = 1H-indazole-3-carboxylic acid, 1,3-bis(4-pyridyl)propane (DPP), 1,10-phenanthroline (PHEN) and 4,4′-bipyridine (BPY). The crystalline structure and spectroscopy of each complex were characterized by single-crystal X-ray diffraction, elemental analysis, Fourier transform infrared spectroscopy and powder X-ray diffraction. The redox reactions in the complexes were then investigated by performing cyclic voltammetry under nitrogen conditions at room temperature. Two pairs of distinctive irreversible reduction potentials were identified, which could be attributed to the processes of Cu(II)–Cu(I) and Cu(I)–Cu(0).     

Monotonicity,uniqueness, and stability of traveling waves in a nonlocal reaction‐diffusion system with delay

The purpose of this paper is to study the traveling wave solutions of a nonlocal reaction‐diffusion system with delay arising from the spread of an epidemic by oral‐faecal transmission. Under monostable and quasimonotone it is well known that the system has a minimal wave speed c* of traveling wave fronts. In this paper, we first prove the monotonicity and uniqueness of traveling waves with speed c ?c _?. Then we show that the traveling wave fronts with speed c >c _? are exponentially asymptotically stable.     

Evaluation of the Hamming weights of a class of linear codes based on Gauss sums

Linear codes with a few weights have been widely investigated in recent years. In this paper, we mainly use Gauss sums to represent the Hamming weights of a class of q-ary linear codes under some certain conditions, where q is a power of a prime. The lower bound of its minimum Hamming distance is obtained. In some special cases, we evaluate the weight distributions of the linear codes by semi-primitive Gauss sums and obtain some one-weight, two-weight linear codes. It is quite interesting that we find new optimal codes achieving some bounds on linear codes. The linear codes in this paper can be used in secret sharing schemes, authentication codes and data storage systems.     

各向异性弹塑性中厚度板壳的有限元分析

本文在文献［２，３］的基础上，提出了一个解各向异性弹塑性中厚度板壳问题的有限元方法。考虑材料各向异性的特点，采用了Ｈｉｌｌ推广的Ｈｕｂｅｒ－Ｍｉｓｅｓ屈服准则；借用Ｏｗｅｎ的剪切修正系数，正确计及了叠层复合材料壳体的横向剪切效应；为了避免“自锁”现象，文中采用了９节点的Ｈｅｔｅｒｏｓｉｓ二次壳单元；特别是本文利用插值外推的思想，提出了一个带预测的弧长增量控制法，显著提高了确定变形路径的计算效率。几个数值算例表明本文给出的有限元方法对于各向异性中厚度板壳的弹塑性分析有较好的精度，尤其是对具有复杂变形路径的结构计算，收敛速度提高更快。     

复合材料层板边缘效应的准相似元解法

用准相似单元法研究了复合材料层板直边和孔边的自由边缘效应，得到了一些具有工程意义的结果。准相似单元法是相似单元法的推广，利用这一方法可以求解三维的应力集中问题，避免了求单刚时的重复计算。由于采用了按相似层求解的技术，应用准相似单元法求解应力集中问题时对计算机容量的要求大为降低     

双轴速率位置台全数字化控制系统实现

讨论了一种适用于双轴测试转台的全数字化控制系统结构。该系统采用了多单片机并行实现的主从分布式控制方法，不仅大大简化了系统硬件设计，提高了可靠性；而且其控制器完全由软件来实现，易于实现模拟电路难以实现的复杂的控制规律；同时也为在不改变硬件的前提下进一步扩展系统功能，改善系统的动、静特性提供了基础。实验表明，文中提出的全数字化控制系统结构完全能满足双轴测试转台的控制需要。     

一种复合材料梁架结构的强度可靠性分析

为解决分析复合材料框架式结构的强度可靠性问题 ,应用最小势能原理 ,设计推导了一种具有复杂剖面形状 ,考虑横向剪切 ,承受横向集中及分布载荷作用的层合梁单元。根据一具体水平梁架的实际情况 ,结合有限元处理程序中组装总体刚度矩阵的特点 ,较好地实现了层合梁之间的不完全简支连接。分析系统强度可靠性时 ,通过可调控的运行方式 ,有效解决了挑选失效模式与离散单元数目之间的关系 ,使系统可靠性的计算更合理     

隐式Newmark法分析波动问题精度的探讨

本文研究了用平均加速度的Newmark积分格式求解一维平面弹性波动问题的精度。由于平均加速度的Newmark积分格式没有振幅衰减、不产生数值阻尼,因此采用此法分析波动问题会产生较强的高频振荡,尤其是加速度的计算值误差甚大。本文对防护工程中常见的平台型荷载和升压三角形荷载作用下的波动问题,应用有限元分析的实例表明:采用有数值阻尼的Newmark积分格式是改进有限元求解波动问题的一个有效方法,可以大大地提高应力和加速度求解精度。文中推荐的有数值阻尼Newmark积分格式的积分参数(=0.9,=0.49)可供工程中土与结构动力分析时参考使用。     

The problems of nonlinear bending for orthotropic rectangular plate with four clamped edges

（黄家寅）（秦圣立）ＴＨＥＰＲＯＢＬＥＭＳＯＦＮＯＮＬＩＮＥＡＲＢＥＮＤＩＮＧＦＯＲＯＲＴＨＯＴＲＯＰＩＣＲＥＣＴＡＮＧＵＬＡＲＰＬＡＴＥＷＩＴＨＦＯＵＲＣＬＡＭＰＥＤＥＤＧＥＳ￥ＨｕａｎｇＪｉａｙｉｎ;ＱｉｎＳｈｅｎｇｌｉ（ＱｕｆｕＮｏｒｍａｌＵｎ...