A simple but realistic model for laser cladding

A model which takes into account the main phenomena occurring during the laser-cladding process is proposed. For a given laser power, beam radius, powder jet geometry, and clad height, this model evaluates two other processing parameters, namely, the laser-beam velocity and the powder feed rate. It considers the interactions between the powder particles, the laser beam, and the molten pool. The laser power reaching the surface of the workpiece is estimated and, assuming this power is used to remelt the substrate with the clad having been predeposited, the melt-pool shape is computed using a three-dimensional (3-D) analytical model, which produces mmediate results, even on personal computers. The predictions obtained with this numerical model are in good agreement with experimental results. Processing engineers may therefore use this model to choose the correct processing parameters and to establish cladding maps. Formerly Postdoctoral Fellow, Physical Metallurgy Laboratory.     

冷作磨具钢Cr12MoV磨削温度场的仿真

针对冷作磨具钢Cr12MoV进行了磨削温度场的研究,并依据建立的有限元仿真模型,对扩径头外扇形块模型进行了磨削温度场的仿真,实现了扇形块磨削温度场的预测,为研究磨削参数对磨削温度的影响提供了理论依据。     

论高等工科院校学生的敬业教育

良好的敬业教育是高等工科院校为社会主义现代化建设培养高素质工程人才的有力保证,学校应该从职业感知、品质培养和实践磨练三个方面来切实加强学生敬业精神的培养工作。     

Influence of the Composition of Electrolyte for Hard Anodizing of Aluminum on the Characteristics of Oxide Layer

Materials Science - The procedure of hard anodizing is carried out at a temperature of (– 4)–0°C for 60 min. A 20% aqueous solution of H2SO4 is used as the base electrolyte. In the...     

Automatic Detection and Repair Recommendation for Missing Checks

Missing checks for untrusted inputs used in security-sensitive operations is one of the major causes of various vulnerabilities. Efficiently detecting and repairing missing checks are essential for prognosticating potential vulnerabilities and improving code reliability. We propose a systematic static analysis approach to detect missing checks for manipulable data used in security-sensitive operations of C/C++ programs and recommend repair references. First, customized securitysensitive operations are located by lightweight static analysis. Then, the assailability of sensitive data used in securitysensitive operations is determined via taint analysis. And, the existence and the risk degree of missing checks are assessed. Finally, the repair references for high-risk missing checks are recommended. We implemented the approach into an automated and cross-platform tool named Vanguard based on Clang/LLVM 3.6.0. Large-scale experimental evaluation on open-source projects has shown its effectiveness and efficiency. Furthermore, Vanguard has helped us uncover five known vulnerabilities and 12 new bugs.     

Fractographic Signs of Gigacycle Fatigue and Hydrogenation of Heat-Resistant Steels after Long-Term Operation

Materials Science - We study the structure and distribution of hydrogen in 16GNM steel after its long-term (～28???104?h) operation in the body of a drum-boiler after a...     

Evaluation of Humidity Correction Factor of Disruptive Discharge Voltage of Standard Sphere Air Gaps

The humidity correction method prescribed in the existing IEC standard is based on experimental data obtained under absolute humidity between 5 and 12 g/m³. A discussion on the humidity correction method is needed for higher absolute humidity regions, which is experienced during summer in Japan, and also throughout the year in tropical countries. The effect of absolute humidity on disruptive discharge voltages of standard sphere air gaps has been studied experimentally for several years under conditions of natural humidity, between 2 and 22 g/m³. In the cases of a.c. and lightning impulse voltage application, it was found that the existing IEC humidity correction method seems to be proper for most of the gap spacings studied under absolute humidity up to 22 g/m³. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

我国物流企业适应电子商务的关键：物流再构造

介绍了电子商务时代物流的新特点、新模式,并结合我国物流的实际提出了物流企业适应电子商务需要的应对措施,即物流再构造。     

Influence of Hydrogenation on the Character of Fracture of Nitinol Alloy in Tension

Materials Science - We establish the macro- and microfractographic features of the tensile fracture of cylindrical specimens made of nitinol (Ni–Ti alloy) at room temperature and at 0°C...     

Diagnostics of the Engineering State of Steam Pipelines of Thermal Power Plants by the Hardness and Crack Resistance of Steel

Materials Science - We propose a nondestructive method for the diagnostics of the current state of heat-resistant steels after long-term operation in the steam pipelines of thermal power plants...