焊接设备中计算机控制系统的抗干扰

本文分析提出焊接设备中影响计算机控制系统的几种主要干扰。结合实际工作,提出了解决的措施和方法。     

C JDBC：可扩展的数据库集群中间件

多层软件结构中已经成功地应用了集群,但在后台数据库上还缺乏这种工具,所以当数据库层出现瓶颈时,就得在硬件上花费高额的费用.开源数据库集群中间件--C-JDBC解决了上述问题.它通过JDBC接口引进了一个虚拟数据库,只要基于拥有JDBC驱动的数据库上面的应用程序,程序无须任何改动就能运行.C-JDBC具有灵活的体系结构,支持大型复杂的数据库集群体系结构,为数据库集群提供的高性能、强容错能力、易用的平台.     

基于FPGA的无线接入点硬件平台的设计与实现*

基于认证、安全及QoS等方面的研究需要,提出了基于FPGA的HostAP设计方案,并搭建了无线接入点的硬件平台,在此平台上进行了硬件的裁减与集成;设计和实现了无线接入点的硬件电路,完成了无线接入点的高速PCB布局布线.在PCB布局布线的过程中,重点解决了高速印制电路板设计中的传输线效应问题,最后进行了实际的系统测试.     

An Analytical Model Including Interface Traps and Temperature Effects in Negative Capacitance Double Gate Field Effect Transistor

Silicon - In this paper, an analytical model for negative capacitance double gate field effect transistor (NC-DG-FET) is proposed. This model includes interface traps and temperature effects, which...     

Mold-filling characteristics of AZ91 magnesium alloy in the low-pressure expendable pattern casting process

The magnesium (Mg) alloy low-pressure expendable pattern casting (EPC) process is a newly developed casting technique combining the advantages of both EPC and low-pressure casting. In this article, metal filling and the effect of the flow quantity of inert gas on the filling rate in the low-pressure EPC process are investigated. The results showed that the molten Mg alloy filled the mold cavity with a convex front laminar flow and the metal-filling rate increased significantly with increasing flow quantity when flow quantity was below a critical value. However, once the flow quantity exceeded a critical value, the filling rate increased slightly. The influence of the flow quantity of inert gas on melt-filling rate reveals that the mold fill is controlled by flow quantity for a lower filling rate, and, subsequently, controlled by the evaporation of polystyrene and the evaporation products for higher metal velocity. Meanwhile, the experimental results showed that the melt-filling rate significantly affected the flow profile, and the filling procedure for the Mg alloy in the low-pressure EPC process. A slower melt-filling rate could lead to misrun defects, whereas a higher filling rate results in folds, blisters, and porosity. The optimized filling rate with Mg alloy casting is 140 to 170 mm/s in low-pressure EPC.     

Rheology of poly(vinyl chloride) blends

PVC/EVA blends were studied with an extrusion plastometer in order to examine the effect of EVA on the processability of PVC. The melt flow of PVC/EVA blends containing from 4 to 30 weight percent EVA follows a simple power law between 160 and 180°C. EVA reduced the melt viscosity and enhanced processability. Blends of PVC and EVA were morphologically incompatible. The molecular weight of extruded PVC in the blends was unchanged.     

Electron Emission from Barium Strontium Titanate Ceramics

This paper focuses on understanding the influence of materials' properties on the ferroelectric electron emission. Ferroelectric ( x =1.0 and 0.8) and paraelectric ( x =0.67 and 0.5) compositions of barium strontium titanate (Ba _x Sr_{(1− x )}TiO₃) system were chosen for study based on their different ferroelectric and dielectric properties. Similar emission current waveforms were obtained from four compositions with negative triggering voltage applied to the rear electrode of the samples. It was difficult to explain the experimental results using the spontaneous polarization-switching model. The mechanism of electron emission from Ba _x Sr_{(1− x )}TiO₃ ceramics was ascertained to surface plasma emission.     

Analytical melting model for extrusion: Stress of fully compacted solid polymers

Our laboratory recently published several analytical equations that can be used to predict the melting rate of fully compacted solid polymers sliding on a heated metal surface, modeling the melting mechanism inside an extruder. These equations were obtained by seeking asymptotic solutions to the differential equations describing the melting mechanism, temperature, and shear-dependent viscosity of polymer melts. Following the same asymptotic approach, we successfully developed accompanying analytical equations for predicting the stress required to slide fully compacted solid polymers on a heated metal surface. The accuracy of these analytical stress equations was found to be reasonable, although not fully satisfactory, by comparing their predictions to the experimentally measured values. The accuracy of the stress calculation is directly related to the accuracy of the viscosity values at high shear rates. The consideration of the temperature and shear dependencies of melt viscosity is most important for accurate prediction of the stress, just as it is for the melting rate. The stress not only depends on the melt rheological properties of the polymer but also on the thermodynamic properties.     

丝状真菌纤维素酶合成机制的研究

丝状真菌产生的纤维素酶被认为是最有应用前景的,但就目前酶生产效率来看,离实际应用还有很大的差距,需要对酶的合成调节机制有更为全面和深刻的了解。纤维素酶的生物合成受诱导和阻遏双重控制,酶的生产既有赖于低廉的保持一定浓度诱导物的存在,又必须清除分解代谢产物对酶合成的阻遏,其中的详细机制有待进一步的阐明。真菌纤维素酶的分泌也是相当复杂的,在酶的分泌过程中,酶会发生例如糖基化等一系列变化。提高纤维素酶的活力测定方法的准确性,使其进一步规范化,是研究纤维素酶工作的另外一个重要的领域。随着现代生物学朝着分子水平的不断发展,分子生物学的许多方法也越来越多地被应用于纤维素酶的研究中,并取得了重要进展。对真菌纤维素酶合成调节机制的深入研究,将为提高纤维素酶产量,推动应用工作的发展打下理论基础。