自然冷源在家用冰箱系统应用及性能分析

空气自然冷源已逐渐用于制冷系统中,引入自然冷源能提高冷凝器出口过冷度,或将自然冷源冷却载冷剂经节流直接引入蒸发器,可有效提高系统COP;基于国内冬春季温度≤5℃的自然冷源分布状况,设计了一种引入自然冷源用于家用冰箱的新型制冷系统,并建立热力学计算模型,分析了不同自然冷源工况时冷凝器过冷度在0、5、10、15℃下的系统COP、压缩机指示功率、系统耗电量及冷凝器热负荷,经计算,冬春季时与传统家用冰箱制冷系统相比,系统COP提高了12%,日均系统耗电量节约0.48kWh。     

A convenient cyclopropanation process of oxindoles via bromoethylsulfonium salt

A practical convenient conversion of oxindoles into the corresponding spirocyclopropyl oxindoles is achieved efficiently using bromoethylsulfonium salt, which is easily prepared on a large scale and is stable crystalline. This reaction of bromoethylsulfonium salt with different substituted unprotected oxindoles proceeded under mild condition and provided moderate yields.     

Synthesis and properties of 5,10,15,20‐tetra[(4‐alkoxy‐3‐ethyloxy)phenyl]porphyrin hydroxylanthanide liquid crystal complexes

Twelve 5, 10, 15, 20‐tetra[(4‐alkoxy‐3‐ethyloxy)phenyl]porphyrin hydroxylanthanide complexes Ln[(C _n OEOP)₄P](OH) (n?=?12, 14, 16;Ln?=?Tb, Dy, Er, Yb) and three ligands have been synthesized and their composition, structure and spectral properties studied. Their liquid crystalline behaviour is also presented. Differential scanning calorimetry and polarizing optical microscopy reveal that all exhibit a discotic liquid crystalline phase. X‐ray diffraction shows that the mesophase is a hexagonal columnar, Col_h. The lanthanide ion, which is coordinated to the four nitrogen atoms of the porphyrin and to the oxygen atom of the hydroxyl group, is out of the porphyrin molecular plane. All the complexes are stable below 200°C and undergo complete decomposition at 800°C. The fluorescence quantum yields of the lanthanide complexes are much lower than those of the corresponding ligands. The electrochemical studies show that the redox potentials do not change on varying the chain length.     

Direct observation of Cu interphase precipitation in continuous cooling transformation by atom probe tomography

Atom probe tomography (APT) combined with electron back scatter diffraction and transmission electronic microscopy (TEM) is utilized to characterize the nature of copper precipitation during austenite–ferrite transformation in a continuous cooling high-strength low-alloy steel. The copper precipitation manners in association with the austenite decomposition kinetics are studied. The prevailing microstructure of the continuous cooling steel consists of acicular ferrite (AF), which is formed at an intermediate cooling rate of 10?°C/s. Besides, a limited volume of polygonal ferrite (PF) because of fast cooling rate and a trace of retained austenite are detected. Numerous copper-rich phase is found by TEM observation both in highly dislocated AF and dislocation-free PF. Generally, the copper-rich precipitates have comparatively large sizes and are considered to be formed by interphase precipitation during austenite–ferrite transformation. A high number density of nanometre sized copper-rich clusters that are lack of diffraction contrast in conventional TEM observation are detected by APT. These smaller copper-rich clusters, which are usually located between the linear-arranged copper-rich precipitates, are considered to be formed from supersaturated solid solution after the cessation of austenite–ferrite transformation. That means an ageing reaction for Cu precipitation occurs during continuous cooling transformation. The copper-rich precipitates and clusters are both rich in nickel, manganese and iron.     

Particle identification using artificial neural networks at BESⅢ

A multilayered perceptrons' neural network technique has been applied in the particle identification at BESⅢ. The networks are trained in each sub-detector level. The NN output of sub-detectors can be sent to a sequential network or be constructed as PDFs for a likelihood. Good muon-ID, electron-ID and hadron-ID are obtained from the networks by using the simulated Monte Carlo samples.     

Synthesis of Novel C2-Symmetrical Bidentate Phosphoramidite Ligands for Rh-catalyzed Asymmetric Hydrogenation of β-（Acylamino）acrylates

Enantiomerically pure β-amino acids and their derivatives are especially attractive due to their vital importance for biochemical and medicinal applications1. One of the most convenient paths to β-amino acids involves the asymmetric hydrogenation of the…     

机械臂运动路径设计问题

针对机械臂运动的逆问题,提出了无障碍空间的牛顿迭代算法.并对牛顿迭代法进行了改进,建立了有障碍空间中避碰问题的一般模型,并对问题进行了求解.对于求出的机械臂指尖的姿态,先采用最大步长调整,再对剩余部分采用一次微调的方法生成指令序列,使生成的序列尽可能的短.针对具体问题①,给出了达到目标点的一个指令序列,步数为89步,精度为0.179mm;对于问题②,离散化裂纹,应用大步长调整的牛顿迭代法,给出了一个运动序列,实现了避碰焊接,各点的平均精度达到0.188mm,并对最低点附近在1mm误差范围内不可达到的区域进行了讨论,用解析和仿真的方法证明和验证了最低点不可达;对于问题③,改进了避碰问题的一般模型和算法,用试探法实现了四个焊接点的无碰焊接,并对圆台内表面在1mm误差范围内不可焊接的区域进行了分析.     

面向对象的BESⅢ探测器模拟系统

BESⅢ探测器的模拟软件包BOOST, 是基于Geant4开发的面向对象的模拟软件. BOOST全面地模拟了BESⅢ探测器的物质和几何结构, 给出了粒子在各个子探测器中的击中信息, 以ASCII码文件的形式输出原始数据和MC truth信息可供重建软件开发和物理分析使用, 初步结果显示BOOST的模拟是合理的.     

机械臂运动路径设计问题

主要运用最优化的思想对机械臂运动路径的设计问题进行了讨论.首先利用空间几何知识,得出了机械臂末端的空间位置与各关节角度间的关系,然后就不同问题进行具体分析后分别建立了最优化模型并设计了相应算法,根据模型和算法并采用逐步缩小搜索范围等方法对各个问题进行了求解.最后,从提高机械臂灵活性和扩大其适用范围方面提出了改进建议.