A 21st century technique for food control: Electronic noses

This work examines the main features of modern electronic noses (e-noses) and their most important applications in food control in this new century. The three components of an electronic nose (sample handling system, detection system, and data processing system) are described. Special attention is devoted to the promising mass spectrometry based e-noses, due to their advantages over the more classical gas sensors. Applications described include process monitoring, shelf-life investigation, freshness evaluation, authenticity assessment, as well as other general aspects of the utilization of electronic noses in food control. Finally, some interesting remarks concerning the strengths and weaknesses of electronic noses in food control are also mentioned.     

基于SOS和LTD技术的高重复频率脉冲发生器

提出了磁饱和直线变压器驱动源(LTD)泵浦半导体断路开关(SOS)产生高重复频率短脉冲的技术路线。利用LTD初次级线圈为单匝同轴结构和磁芯可饱和的特点,实现快速反向泵浦SOS,通过多级LTD模块叠加获得高电压输出。采用射频金属氧化物场效应晶体管(RF MOSFET)作为LTD初级电路的主开关,将SOS正向泵浦电流脉冲时间降至数十ns,泵浦电流脉冲重复频率最高可达MHz。最终研制出一台基于SOS的10级磁饱和LTD型脉冲发生器,输出电压约11kV,电流220A,脉冲宽度约2ns,重复频率为20kHz。实验验证了磁饱和直线脉冲变压器泵浦SOS产生高重复频率短脉冲的技术路线可行。     

全弹性平面运动机器人的高精度运动控制和振动抑制算法研究

为实现对基座、关节和臂均存在弹性的空间机器人运动高精度控制及多重振动抑制,建立了基座、关节和臂全弹性空间机器人动力学模型,并采用运动有限维PD重复学习控制及振动同步抑制方案进行研究.首先,利用线性弹簧、扭转弹簧和欧拉-伯努力梁理论,假设模态法和动量守恒定律,采用拉格朗日方程建立了弹性基座、柔性关节和柔性臂空间机器人动力...     

Stable second‐order nonlinear optical poly(amide–imide)/inorganic materials via simultaneous sequential self‐repetitive reaction and sol–gel process

A series of thermally stable organic/inorganic second‐order nonlinear optical (NLO) composites via sequential self‐repetitive reaction (SSRR) and sol–gel process has been developed. This SSRR is based on carbodiimide (CDI) chemistry. The difunctional azo chromophores (2,4‐diamino‐4′‐(4‐ nitrophenyl‐diazenyl)azobenzene (DNDA)) was reacted with excessive amount of 4, 4′‐methylene‐ diphenylisocyanate (MDI) to form poly‐CDI, and subsequently trimellitic anhydride (TMA) was added to obtain poly(N‐acylurea). The organic/inorganic composites containing prepolymer of phenyltriethoxysilane (PTEOS) and poly(N‐acylurea) in different weight ratios (10:90, 30:70, 50:50, 70:30, 90:10 wt%) were prepared, respectively. The moderate glass transition temperature (T_g) characteristic of the poly(N‐acylurea) allows the NLO‐active polymer to achieve high poling efficiency. After in situ poling and curing process, the T_gs of the composites were elevated, and higher than that of the pristine poly(amide–imide) sample. Electro‐optical (EO) coefficients (r₃₃) of about 5.5 ～ 18.0 pm/V at 830 nm were obtained. Excellent temporal stability at 100°C, and waveguide characteristics (3.1–4.2 dB/cm at 830 nm) were also obtained for these composites. Copyright © 2008 John Wiley & Sons, Ltd.     

Simultaneous repetitive motion planning of two redundant robot arms for acceleration-level cooperative manipulation

This Letter proposes a novel simultaneous repetitive motion planning (SRMP) scheme of two redundant robot arms for cooperative manipulation. To remedy the joint-angle drift phenomenon, two SRMP subschemes are exploited at the joint-acceleration level. The subschemes are then simultaneously reformulated as two quadratic programs (QPs), which are finally unified into a QP problem solving. Theoretical analysis and computer simulation based on two three-link robot arms both substantiate the feasibility and effectiveness of the proposed SRMP scheme.     

LOB中基于工期决定因素分析的资源均衡算法研究

资源均衡是重复性项目中的经典调度问题,本文提出一种新的基于平衡线法(line of balance,LOB)的资源均衡方法。首先,本文提出LOB中关键路线的确定方法,确定关键路线及关键工序类型。而后,本文分析项目总工期的决定因素,对不同类型关键工序的特性及其与总工期、资源调整之间的关系进行了研究,论证了在LOB的资源均衡问题中,由于逆关键工序、点关键工序这些特殊工序的存在,可以在保证项目总工期不变的前提下,通过同时调整关键工序和非关键工序实现资源优化。按照这一思路,论文设计了LOB中资源均衡的遗传算法。算例分析表明该资源均衡算法的优化性能。本文提出的资源均衡思路和算法能帮助项目计划人员拓展资源优化空间,达到更好的资源均衡效果。     

磁绝缘线振荡器重复频率运行真空系统优化

为改善一种L波段磁绝缘线振荡器（MILO）重复频率运行时的真空环境,建立了器件在分子流下的抽气模型,采用Monte-Carlo方法对阴极脉冲放气后的瞬态抽气过程进行了模拟计算,获得了不同时刻气体分子在MILO内部的3维分布情况,并据此提出了一种分布式抽气方案,即在MILO靠近气源的微波传输区增加一抽气单元,以缩短脉冲间隔内的抽气时间。在Torch-01调制器上开展了MILO分布式抽气的实验验证,结果显示,分布式抽气时的气压下降特征时间为单泵的0.22倍,与模拟结果基本一致;初步的重复频率测试也表明分布式抽气能够缩短脉冲串间隔内的抽气时间以保持器件运行时的真空水平。在所给实验条件下,从真空的角度,分布式抽气能够使MILO有效运行的重复频率数提升至单泵抽气时的5倍。     

紧凑型重复频率高压纳秒脉冲电源及其仿真模型

纳秒脉冲等离子体在诸多实际的工程应用中依赖于小型化且可靠的纳秒脉冲电源实现。设计了一种紧凑型全固态高压纳秒脉冲电源,该电源主要由直流电源部分、绝缘栅双极晶体管及其驱动控制电路、可饱和脉冲变压器、磁脉冲压缩网络等组成。通过理论计算分析、PSpice电路仿真以及实验研究表明,其最终可以在800 的输出负载阻抗上获得幅值40 kV、脉冲宽度100 ns左右、脉冲上升沿约50 ns的高电压脉冲,重复频率最高可达5 kHz。     

40GW重复频率脉冲驱动源研制进展

40 GW重复频率脉冲驱动源是应高功率微波技术发展等需求而设计的一台基于Tesla变压器技术的重复频率脉冲功率装置。40 GW驱动源设计输出功率40 GW,脉宽60 ns,重复频率1~50 Hz,输出功率及重复频率工作状态在一定范围内可调。介绍了40 GW高功率重复频率脉冲驱动源的系统构成、电气及结构参数的确定方法、关键部件的工程工艺技术,并分析了关键绝缘部件的电场分布。已完成驱动源安装并进行了实验调试,其主要单元Tesla变压器的能量效率达到70%,驱动源单次工作状态下输出功率大于40 GW;50Hz重复频率工作状态下,输出功率20.6 GW,系统工作稳定可靠。     

一种重复频率的高功率脉冲发生器

 介绍了一种由Tesla变压器和同轴脉冲形成线组成的高功率、高重复频率的脉冲发生器，其特点是结构紧凑，容易实现小型化。简述了该发生器的结构，论述了基本原理和特性，分析了应用前景。