基于可拓理论的数控代码转换系统的研究

为了解决ISO6983标准的数控(NC)代码共享问题,研究了一种基于可拓理论的数控代码转换系统.系统的信息定制模块根据机床基本性质、程序格式、代码功能复合元模型,完成对应信息的存储;系统的核问题求解模块负责代码功能参数的转换、代码功能的分解和程序格式的转换;系统的源系统代码输入模块通过运动变换矩阵完成机床类型的选择、代码的输入和代码的词法语法分析;系统的中间文件生成模块根据STEP标准的生成中间文件;系统的目标系统代码生成模块对代码进行最优选择和转换.系统的性能取决于三个复合元和核问题解的的完备性.     

聚丁二酸丁二醇酯的扩链改性及共混研究

采用扩链剂2,4-甲苯二异氰酸酯（TDI）、2,2′-双（2-恶唑啉）（BOZ）以及新型扩链剂ADR-4370对聚丁二酸丁二醇酯（PBS）进行扩链,对比研究3种扩链剂对PBS性能的影响。采用聚乳酸（PLA）与PBS共混,选择最佳配比以及合适的共混工艺。结果表明,新型扩链剂ADR-4370可以良好的改善PBS的加工性能和机械性能,m（PBS）/m（PLA）最佳配比为70：30,在共混同时进行扩链比扩链后再共混可以更好的提高PBS/PLA的性能。     

PBS基降解塑料的共混与就地增容扩链改性研究

采用扩链剂2,4甲苯二异氰酸酯(TDI)、2,2'-双(2-恶唑啉)(BOZ)以及新型扩链剂ADR-4370对聚丁二酸丁二醇酯(PBS)进行扩链,研究了三种扩链剂对PBS性能的影响。采用聚乳酸(PLA)与PBS共混,选择最佳配比以及合适的共混工艺。结果表明:新型扩链剂ADR-4370可以明显改善PBS的加工性能和力学性能,PBS/PLA最佳配比为70:30,在共混同时进行就地增容扩链改性可以更好地提高PBS/PLA的性能。     

Evaluation of grounded isometric interface for whole‐body navigation in virtual environments

Whole‐body interaction is an effective way to promote the level of presence and immersion in virtual reality systems. In this paper, we introduce “G‐Bar,” a grounded isometric interaction device that naturally induces whole‐body interaction without complicated sensing and active haptic feedback apparatus. G‐Bar takes advantage of the significant passive reaction force feedback sensed throughout the body to produce an enhanced level of presence/immersion and possibly even task performance. For detailed investigation in the contributing factors, two experiments were carried out to assess the comparative effectiveness of G‐Bar to the following: (1) grounded but isotonic device (with force feedback and without); and (2) nongrounded handheld devices (both isotonic and isometric). The results showed that the G‐Bar induced significantly higher presence and competitive task performance (fixed velocity navigation) than the isotonic (grounded or handheld) and nongrounded isometric interfaces. Compared with the grounded isometric device with active force feedback, G‐Bar produced competitive performance. In particular, the analysis of the subjective evaluation revealed a high correlation between the level of presence and whole‐body interaction. On the other hand, whole‐body experience was not induced as much with just the active force‐feedback devices. Thus, for appropriate tasks, the grounded isometric interface can be a viable alternative to expensive and mechanically limiting active force‐feedback devices in enhancing user experience. Copyright © 2013 John Wiley & Sons, Ltd.     

多场景MPLS标签交换实现方法

MPLS标签交换是目前IP通信网络中使用广泛的一项技术,其固定的标签格式虽然大大加速了转发引擎交换速度,承载了一定的QoS信息,但其针对特殊领域、特殊用途的标准制定、实现途径却无能为力,在一定程度上制约了其更加广泛且有效的应用。从标准MPLS标签头的角度出发,分析了当前MPLS交换体制的不足,借鉴IPV6的思想,提出一种通过扩展标签头格式和转发表的方法,解决提出的MPLS扩展性问题。     

LEMD端点延拓方法及其在微震信号降噪中的应用

针对非平稳的微震信号,采用经验模态分解(Empirical Mode Decomposition,EMD)方法对其滤波、消噪。但该方法在应用中存在严重的端点效应,会影响分解结果。为了改善端点效应,针对微震信号低频特点,提出了基于LMS自适应滤波器对微震数据端点处进行波形延拓的方法。LMS自适应滤波器经过信号内部的数据训练后从端点处向左右延拓波形,延拓过程中生成符合内部信号趋势的极小值和极大值,波形的延拓长度由延拓算法自适应决定。在EMD对信号分解过程中得到前一层模态分量后均再次对剩余信号进行延拓,进而进行下一层分解,以此修正插值算法带来的误差。最后根据信号频率特点对得到的模态分量有选择的重构,达到降噪的目的。利用仿真数据和煤矿微震监测数据对LMS自适应延拓法进行了验证,结果表明该方法能够明显减小经验模式分解的端点效应,特别对低频的微震信号有很好效果。     

Shelf Life and Sensory Characteristics of Baby Spinach Subjected to Electron Beam Irradiation

Abstract: The use of ionizing radiation for the control of foodborne pathogens and extending the shelf life of fresh iceberg lettuce and fresh spinach has recently been approved by the U.S. Food and Drug Administration. The efficacy of electron beam irradiation for controlling foodborne pathogens has been reported. For this experiment, the effectiveness of electron beam irradiation on the microbiological and sensory characteristics of fresh spinach was studied. Total aerobic plate counts were reduced by 2.6 and 3.2 log CFU/g at 0.7 and 1.4 kGy, respectively. Lactic acid bacteria were reduced at both doses of e-beam but grew slowly over the 35 d of the experiment. Yeasts and molds were not reduced in samples exposed to 0.7 kGy whereas 1.4 kGy significantly reduced microbial counts. Gas compositions (O₂ and CO₂) were significantly different than controls. Oxygen levels inside the spinach sample bags decreased over time; however, O₂ levels did not drop below 1% that can induce anaerobic fermentation. CO₂ levels for all treatments increased through day 4; yet 7 d after irradiation, CO₂ level differences were not significant in both control and irradiated samples. Irradiation dose did not affect the basic tastes, aromatics, or mouth feels of fresh spinach, however; hardness attributes decreased as irradiated dose increased and slimy attributes of fresh spinach were higher in control samples compared to irradiated samples.     

A novel method to investigate tensile properties of woven fabrics in all-direction

In this research, we propose a new method and instrument to measure load-extension curve of the fabric samples under all-directional extension. Using this method, fabric sample is loaded under extension in the warp, weft, and all other directions in between. Using this new method, we introduced a comprehensive tensile modulus which is affected by the fabric structures and densities. For this purpose different structures i.e. plain, Twill 2/2, Twill 1/3, and Twill 1/7 were produced with different densities. Then these samples were tested under the new method. Our results are then compared to those one would obtain under uniaxial tests, by performing independent uniaxial tests. It is shown that under all-directional test lowering the weft density decreases the tensile comprehensive modulus. Furthermore, a reduction in the floating yarns in the fabric structure decreases the tensile comprehensive modulus. It was found that among the samples tested here, plain fabric and Twill 1/7, respectively, possess the maximum and minimum comprehensive modulus. A similar trend was also observed through independent uniaxial extension, in warp or weft direction, test.     

On practical construction of electronically controllable compact current amplifier based on commercially available elements and its application

This paper presents a new concept of a current amplifier (CA) with electronically adjustable features (input resistance and current gain) implemented using commercially available devices. Several variations of basic structure are studied, described and the selected solutions verified by PSpice simulations and, moreover, also by lab experiments. Saving one discrete active device in comparison to already known similar topologies of single-input and single-output version (CA-SISO) is significant benefit whereas all other qualitative features remain very similar to previously reported ones. Simple modification of CA concept to multiple-output version (CA-SIMO), having independent adjustable current gain in each of output branches, is easily available. Experimental tests of features of discussed concepts yield adjustability range of input resistance from 100 Ω to more than 10 kΩ and current gain adjusting from 0.1 to 3.5 with bandwidth (−3 dB) of CA transfer response up to 16 MHz. As an example of application, proposed CA was successfully implemented in quadrature oscillator with a very wide tunability range from 29 kHz to 4.94 MHz. It was achieved by electronic control of several adjustable parameters of proposed CA.