Dimeric ortho‐palladated homoveratrylamine as an efficient homogeneous catalyst for copper‐free Sonogashira cross‐coupling reaction

The catalytic activity of ortho‐palladated [Pd{C6H2(CH2CH2NH2)‐(OMe)2,3,4}(m‐Br)]2, a complex of homoveratrylamine in the copper‐free Sonogashira coupling reaction has been investigated. This complex is a catalyst that is efficient, stable and non‐sensitive to air and moisture in the Sonogashira reaction. In this homogeneous catalytic system, various aryl halides were efficiently coupled with phenylacetylene in mostly moderate to good yields in N‐methylpyrrolidone at 100 °C under copper‐free conditions. Copyright © 2012 John Wiley & Sons, Ltd.     

Internal flow numerical simulation of a cross‐flow fan in refrigerant operating condition using user‐defined functions

In the paper, a cross‐flow fan in refrigerant operating condition is systematically simulated using user‐defined functions. Three‐dimensional simulations are acquired with Navier–Stokes equations coupled with k–ε turbulence model, and internal flow characteristics of an indoor split‐type air conditioner are obtained, which is mainly composed of cross‐flow fan and heat exchanger. It has systematically been simulated in the isothermal flow condition that the performance of cross‐flow fan may be reduced easily with dry or humid air, and in the refrigerant operating condition in which user‐defined functions are applied to the humid air, considered as a mixture of dry air and vapor. A density‐modulated function is adopted to deal with the condensation of the vapor at the heat‐transfer region approximately. The results show flow mechanism of the two gas‐phase flow, including phase‐vary process. The distribution of the parameters is not uniform at the inlet of the machine, the intensity and position of pressure and velocity vary along the axial direction of the fan, the distribution of vapor volume fraction and turbulent intensity in heat‐transfer region is obtained, and the external characteristic data of the indoor machine are obtained and analyzed. Compared with the experimental data, the calculated characteristic curves and designed parameters are on target. © British Crown Copyright 2010/MOD. Reproduced with permission. Published by John Wiley & Sons, Ltd.     

A comparison of quantitative nuclear magnetic resonance methods: internal,external, and electronic referencing

The performance of three quantitative NMR methods was compared in terms of short‐term and long‐term precision and accuracy, robustness, linear range, and general applicability. The Internal Reference method employs a reference material co‐dissolved with sample; the External Reference method employs a reference material contained in a separate solution; and the third method, known as Electronic REference To access In vivo Concentrations (ERETIC), employs an externally calibrated digital reference peak. The Internal Reference method results were the most precise and remained stable within 0.1% for at least 4 weeks. The results from the External Reference and ERETIC methods were practically equivalent to each other during this time. These methods exhibited small differences relative to the standard set by the Internal Reference method and slightly lower precision, establishing them as practical alternatives to the Internal Reference method. In contrast to the Internal Reference method, the External Reference and ERETIC methods possess several advantages that address peak overlap, flexibility of calibration, and duration of applicability. The study was designed such that each spectrum contained the information needed to compare the three methods while all other variables were kept constant. Applicability of pulse width compensation is addressed. ERETIC software compensation and minor adjustments to 90° pulse width were concluded to be unnecessary for this system. Although each of the methods was applied here to specifically calculate and compare chemical purity values, this evaluation applies generally to absolute quantitation by NMR. Copyright © 2013 John Wiley & Sons, Ltd.     

沿两条内部平行裂纹受压时材料的断裂问题

顺着平面内的平行裂纹受压材料的断裂问题并不能在线性断裂力学的框架内进行描述，Grif-fith－Irvin型或COC型的断裂判据，虽然可以用来处理经典的线性断裂力学，但对本题则完全不适用，这是因为这些压力对应力强度系数没有影响，与裂缝孔隙值也没有关系[1，2]，这一类问题只能采用新的方法，本文的第一作者曾建议过一种新方法，在这一方法中仍然使用了线性关系，但这种线性关系是从变形固体力学中的非线性方程导出的[3，4，5]．这里必须指出，这种方法曾在变形体稳定性问题中广泛地采用过。作为断裂开始的判据，我们采用了裂缝缺陷附近的局部失稳的判据，在这类情况下，我们认为是从失稳过程引发断裂过程的。     

Microwave spectrum and structure of methyl phosphonic difluoride

The rotational spectrum of methyl phosphonic difluoride has been reinvestigated using a pulsed-molecular-beam Fabry-Perot cavity microwave spectrometer. The enhanced resolution of the Fourier transform microwave (FTMW) spectrometer (compared to the original work done in a conventional Stark spectrometer) has allowed the measurement of small A-E splittings of many of the rotational transitions caused by the internal rotation of the methyl top. The barrier to internal rotation, V₃ = 676 (25) cm⁻¹, has been determined experimentally from the A-E splittings of the rotational transitions in the ground vibrational state. This barrier height is substantially lower than the previously determined value for the barrier, which was 1252 (14) cm⁻¹. High-level ab initio calculations at the MP2/aug-cc-pVTZ level predict a barrier to internal rotation of 638 cm⁻¹, in agreement with the experimentally determined value found here. The high sensitivity of the FTMW spectrometer has also permitted the measurement of the ¹³C and ¹⁸O isotopomers in natural abundance. The addition of these two isotopomers has allowed an improved structural determination.     

Surface instability of orthotropic laminated materials under compression

The piecewise-homogeneous material model and the three-dimensional linearized theory of stability with the assumption of small subcritical strains are used to study the surface buckling of orthotropic and transtropic laminates. A plane problem is formulated, and characteristic equations are derived. A solution is found for a specific transtropic material with different orientations of the isotropy axis __________ Translated from Prikladnaya Mekhanika, Vol. 42, No. 7, pp. 64–72, July 2006.     

Total internal reflection–refraction beam expander

Beam expanders being used presently have complex structure and none is perfect. A novel beam expander is proposed first. The beam expander can magnify (or decrease) the diameter of incident laser beam according to the theory of total internal reflection–refraction (TIR-R) principle. The characteristic of the beam expander was studied by using ray-tracing method and computer simulation. The beam expander can propagate a parallel laser beam along the propagation axis and would not change the propagation direction of the beam. For a nonparallel beam the Lagrange invariant (the product of diameter and divergence angle) is not constant. This beam expander would be an effective device in some applications.     

定域内对称和规范场--为杨-米尔斯场五十周年而作

文章为杨-米尔斯的历史性论文发表50年而写，扼要阐述非阿贝尔规范场理论这篇原创论文的主要思想和它的巨大影响。     

用电位差计测电流表内阻

本文提出几种利用电位差计测电流表内阻的方法和计算不确定度的公式，引做了实验验证和综合评述。