CJ18．2tex赛络纱的生产实践

阐述了赛络纺纱技术的原理,探讨了F1510细纱机改造赛络纺的方法,优选了工艺参数．试验结果表明,在相同的配棉条件下,CJ18．2tex赛络纱的条干、粗细节、强力和毛羽均优于相同线密度的传统环锭纱．     

Electrical behavior of carbon black-filled polymer composites: Effect of interaction between filler and matrix

The effect of interaction between carbon black and polymer on electrical behavior was studied using the ESR method. The polymer matrices used were HDPE, LDPE, and ethylene/vinyl acetate (EVA). Two kinds of carbon blacks (CB), high structure CSF-III and low structure FEF, were used as a conductive filler. Compared to that of the HDPE/FEF compound, the positive temperature coefficient (PTC) intensity is lower and electrical reproducibility is worse for the HDPE/CSF-III compound; however, it can be improved significantly by radiation cross-linking. On the other hand, the cross-linking has no practical effect on the PTC intensity of the LDPE/CSF-III compound while it can be achieved by mixing the compound for a longer time. The great PTC intensity was obtained in the HDPE/EVA/CSF-III compound, and it is greater than that of HDPE/CSF-III or EVA/CSF-III. We explain these results using the concept of interaction between the filler and matrix. The absorption of the polymer on the carbon black surface may be physical or chemical; the latter is caused by the free-radical reaction between the polymer and carbon black, and it can occur during the radiation or preparation process of the compound. These “bound polymers” are essentially important for materials to have a great PTC intensity and good reproducibility. © 1994 John Wiley & Sons, Inc.     

Solvent free oxidation of alcohols catalyzed by KMnO4 adsorbed on Kieselguhr

Efficient and selective oxidation of primary and secondary alcohols to the corresponding aldehydes and ketones catalyzed by potassium permanganate supported on Kieselguhr reagent under solvent free conditions are reported.     

Hand-adaptive user interface: improved gestural interaction in virtual reality

Most interactive user interfaces (UIs) for virtual reality (VR) applications are based on the traditional eye-centred UI design principle, which primarily considers the user’s visual searching efficiency and comfort, but the hand operation performance and ergonomics are relatively less considered. As a result, the hand interaction in VR is often criticized as being less efficient and precise. In this paper, the user’s arm movement features, such as the choice of the hand being used and hand interaction position, are hypothesized to influence the interaction results derived from a VR study. To verify this, we conducted a free hand target selection experiment with 24 participants. The results showed that (a) the hand choice had a significant effect on the target selection results: for a left hand interaction, the targets located in spaces to the left were selected more efficiently and accurately than those in spaces to the right; however, in a right hand interaction, the result was reversed, and (b) the free hand interactions at lower positions were more efficient and accurate than those at higher positions. Based on the above findings, this paper proposes a hand-adaptive UI technique to improve free hand interaction performance in VR. A comprehensive comparison between the hand-adaptive UI and traditional eye-centred UI was also conducted. It was shown that the hand-adaptive UI resulted in a higher interaction efficiency and a lower physical exertion and perceived task difficulty than the traditional UI.

     

Effect of fiber volume fraction on longitudinal tensile properties of SiC<Subscript>f</Subscript>/Ti-6Al-4V composites

The longitudinal tensile properties of SiC_f/Ti-6Al-4V composites with different fiber volume fractions were simulated by the Monte Carlo 2-D finite element model. The random distribution of fiber strength was expressed by the two-parameter Weibull function. Meanwhile, contact elements and birth-death elements were used to describe the interfacial sliding process after debonding and fiber breakage (or matrix cracking) respectively, which was realized by subroutine complied in ANSYS-APDL (ANSYS Parametric Design Language). The experimental results show that the yield stress and ultimate tensile strength of SiC_f/Ti-6Al-4V composites increase with increasing fiber volume fraction, while the corresponding strain of them is just on the contrary. In addition, almost the same failure mode is obtained in SiC_f/Ti-6Al-4V composites with various fiber volume fractions when the interfacial shear strength is fixed. Finally, the tensile strength predicted by finite element analysis is compared with that predicted by Global load-sharing model, Local load-sharing model and conventional rule of mixtures, thus drawing the conclusion that Local load-sharing model is very perfect for the prediction of the ultimate tensile strength.     

大跨度楼盖结构在运动荷载下的振动性能

为研究人员运动荷载下大跨度楼盖的振动特性,以内蒙古伊旗全民健身体育中心大跨度张弦梁楼盖体系为背景,采用生物力学测力平台进行人员行走、跑步、跳跃、起立等运动荷载实测和相关分析研究.考虑可能出现的各种运动荷载工况,对大跨度张弦梁楼盖区振动开展有限元分析和现场实测.分析表明:行走、跑步及跳跃荷载工况下,人员动力放大系数分别约为1.2、2.4及4.9,大跨度楼盖在人员运动荷载数值模型激励下,所得有限元分析结果与现场实测竖向加速度峰值及理论计算值吻合较好.     

基于GSM高速公路管理系统设计

本文所研究的高速公路管理系统是基于GSM模块的。本系统中的GSM模块是一款高性能模块,主控制芯片采用STC12C5A32S2系列单片机可以实现上位机控制GSM模块接、打电话及收发信息等功能。而且可以对收到的信息进行解析,并根据信息内容进行相关操作,从而实现远程控制。该系统可以将高速公路上的各个分站与主控制中心连接起来,便于控制中心对下辖的各管理所进行高速、有效、实时的管理。     

基于安全模式的采购信息系统设计

在企事业的日常工作过程中,采购采购信息系统能提高运行效率。本文基于B/S架构设计了一个高校采购信息系统,分析了系统的安全威胁,提出了基于安全模式的系统设计方法 SDMBSP,利用SDMBSP选用合适的安全模式增强了系统的安全性,取得了良好的效果。     

知识开源化背景下信息安全类课程教学改革初探

本文针对当前知识开源化的现状,结合信息安全类相关课程在北京电子科技学院授课的实际情况,以利用知识开源化所带来的优势,改善课程的教学效果、提高学生的动手实践能力为目的,研究和探讨了信息安全类部分课程的教学模式改革方式和所取得的效果。     

基于相关法的低采样率超声水表时延估计方法

针对当前超声水表中相关法时间分辨率只能达到采样周期的问题,提出了一种基于相关法的低采样率超声水表时延估计方法.首先,研究了超声水表中所能达到的最大时间延迟;其次,讨论了相关法在超声水表当中的具体应用及插值算法对于提高流量测量精度的作用;最后,利用MATLAB软件对算法进行仿真评估了实际噪声条件下算法能达到的时延估计精度并搭建流量计量系统证明算法的有效性.仿真结果表明,在超声换能器频率为1 MHz、采样频率为4 MHz的情况下,时延估计的平均绝对误差在百皮秒内.表明该算法能在较低的采样频率下实现高精度的时延估计,在时延估计精度上比传统相关法更具有优越性.