MA制备GdSiGeDy合金系室温磁制冷性能研究

机械合金化(MA)是一种材料固态非平衡加工新技术.本文主要探讨稀土元素Dy在机械合金化工艺条件下对磁制冷合金GdSiGe磁熵变的影响,发现用机械合金化制备的GdSiGeDy合金系室温磁制冷材料不仅有光滑的磁熵变曲线,而且研究表明,由于元素Dy的加入在磁熵变达到单质Gd的两倍情况下大量减少使用昂贵元素Ge的结果,具有明显经济效益.     

考虑冷变形加工硬化的翻边力理论计算

在分析现有计算公式存在不足的基础上,根据翻边变形区材料的应力应变特点,考虑了冷变形加工硬化(取幂函数硬化规律)和变形区材料厚度变化(翻边为变薄)两个因素的影响,利用金属塑性成形问题求解理论中的主应力法,推导和提出了圆孔翻边力计算的一个新公式.通过用钢板(SPCC)和铜板(T1)进行了翻边工艺试验的验证,并与经验公式和现有理论公式的计算结果进行了比较,表明新公式计算结果能接近于实际,且原理上更为科学合理.     

Zonal disintegration phenomenon in enclosing rock mass surrounding deep tunnels -- Elasto-plastic analysis of stress field of enclosing rock mass

The zonal disintegration phenomenon (ZDP) is a typical phenomenon in deep block rock masses. In order to investigate the mechanism of ZDP, an improved non-linear Hock-Brown strength criterion and a bi-linear constitutive model of rock mass were used to analyze the elasto-plastic stress field of the enclosing rock mass around a deep round tunnel. The radius of the plastic region and stress of the enclosing rock mass were obtained by introducing dimensionless parameters of radial distance. The results show that tunneling in deep rock mass causes a maximum stress zone to appear in the vicinity of the boundary of the elastic and the plas-tic zone in the surrounding rock mass. Under the compression of a large tangential force and a small radial force, the rock mass in the maximum stress zone was in an approximate uniaxial loading state, which could lead to a split failure in the rock mass.     

Investigation on the electrocatalytic characteristics of SnO_2 electrodes with nanocoating prepared by electrodeposition method

SnO2 electrodes have many advantages in the degradation of toxic or bio-refractory organic wastewater,and SnO2 is a kind of anode material which has the potential to be widely used.Electrocatalytic effi-ciency and service life of Ti\SnO2 electrodes are key factors that can influence its applications.In order to enhance the electrocatalytic characteristics of Ti\SnO2 electrodes,a type of electrocatalytic electrode with nanocoating was prepared by direct current(DC)electrodeposition method and thermal oxidati...     

陶瓷原料中二氧化硅分析方法的对比与选择

本文综合各种文献 ,对陶瓷原料中SiO2 的各种分析方法的优缺点 ,使用条件 ,应用侧重点进行了比较与评述     

Reprint of “Suppressing propylene carbonate decomposition by coating graphite electrode foil with silver”

A method has been developed to suppress the decomposition of propylene carbonate (PC) by coating graphite electrode foil with a layer of silver. Results from electrochemical impedance measurements show that the Ag-coated graphite electrode presents lower charge transfer resistance and faster diffusion of lithium ions in comparison with the virginal one. Cyclic voltammograms and discharge-charge measurements suggest that the decomposition of propylene carbonate and co-intercalation of solvated lithium ions are prevented, and lithium ions can reversibly intercalate into and deintercalate from the Ag-coated graphite electrode. These results indicate that Ag-coating is a good way to improve the electrochemical performance of graphitic carbon in PC-based electrolyte solutions.     

基于深度学习的集群式供应链应急物资需求预测研究

在突发事件和大数据情景下,建立基于数据流模糊C均值聚类算法的集群式供应链应急物资需求重要度决策算法,有助于辨识集群式供应链子系统应急物资需求的重要程度。针对集群式供应链中各子供应链之间的耦合特性和预测指标的快速变化数据流特征,提出基于长短期记忆网络的集群式供应链应急物资需求动态预测算法,提取集群式供应链多个子系统应急物资需求参数的时序特征,动态地、分布地对互联大系统的应急物资需求不确定性进行系统辨识估计。仿真实验结果表明了基于长短期记忆网络的集群式供应链互联大系统应急物资需求动态预测算法的可行性和精确性。     

A free space frequency‐time‐domain technique for electromagnetic characterization of materials using reflection‐based measurement

In this report, a free space frequency‐time‐domain technique is presented for characterizing the electrical properties and thickness of the sample using multiple reflections and fabry‐perot resonance phenomenon. The retrieval of constitutive electromagnetic parameters of the sample has been carried out by comparing the measured reflection coefficient data from the sample at two different incident angles. The relative permittivity as well as relative permeability along with the thickness of different samples viz., beryllia, silicon, and plexiglass have been evaluated with high accuracy in the frequency range 1 to 15 GHz. The method is also experimentally validated by successfully reconstructing the unknown material properties of two different samples. The unique advantage of this method lies in non‐requirement of any prior knowledge of the sample's thickness for measuring the complex relative dielectric constant as well as relative permeability of the sample. To determine the electromagnetic properties of the sample, the sole knowledge of reflection coefficient data are needed. Moreover, the method does not involve any additional measurement for the reference calibration. The simple, cost‐effective proposed scheme is quite useful in many applications like accurate determination of signal strength in indoor wireless communication, through wall imaging, food industry, and so on.     

Probabilistic and interval reliability design of the composite pressure vessel

Considering the randomness or interval character of physical parameters and applied loads of composite pressure vessels (COPV), the COPV reliability-analyzing model is built. And then the computational expressions for the mean value, standard deviation and deviation of fiber stress are deduced by the random factor method. The probabilistic and interval reliability designs on COPV are implemented by utilizing the probabilistic method and interval method combined with the improved particle swarm optimization (PSO) algorithm, respectively. The influence of fluctuation of structure uncertain parameters on COPV design thickness is inspected. Finally, examples are given to demonstrate that both probabilistic and interval reliability methods can satisfy the safety requirement and both are of higher rationality than the traditional safety factor method. And probabilistic method has a lower relative error but a higher computational complexity contrasted with the interval method.     

Dynamic buffering performance of the honeycomb paperboard filled with polyurethane

A new kind of composite buffering material was made by filling the voids of honeycomb paperboard with polyurethane. Drop tests were performed to evaluate the dynamic energy absorption capacity of the material. Based on the tests results, we analyzed the mechanical behaviors of the material under different conditions and obtained the inherent influencing laws of some factors on the material＇s dynamic buffering performance. It was shown that the dynamic buffering performance varied directly with impact velocity, and inversely with the void diameter, thickness and buffeting area of the composite material.