悬浮液进样-火焰原子吸收光谱法测定茶叶中的微量铬

将茶叶悬浮于琼脂胶体中制成悬浮液 ,直接喷入空气 -乙炔火焰 ,用火焰原子吸收光谱法测定茶叶中的微量铬 ,方法简便、快速、灵敏度和精密度高、测定结果与用灰化法处理样品一致 ,检验表明 ,两种样品前处理方法之间无显著性差异。相对标准偏差为 3.4 %～ 6 .1% ,加标回收率为 95 .7%～ 10 3.8 %。     

Air sampling of volatile sex pheromone components in a closed jar

A cotton wool plug, used as the source for pheromone release, was placed in closed 1-quart Mason jars, either at the mouth or at the rear of the jar. Air sampling of the two components of the sex pheromone (total 2.2 mg at the source) of the almond moth (Ephestia cautella) female showed that the saturation period near the source in still air was 20–22 hr and that far from the source was 40–50 hr, reaching a level of less than 1 ng/ml air. The ratio between the components (Z,E)-9,12-tetradecadienyl acetate, designated D, and (Z)-9-tetradecenyl acetate designated M, in the air was close to the original ratio for both sampling sites, albeit somewhat richer in the more volatile (Z)-9-tetradecenyl acetate (source 77.023.0 DM, air 73.0– 74.327.0–25.7; source 80.119.9, air 77.622.4; source 25.174.9, air 23.976. 1 DM). The total amount of pheromone per milliliter of air was two to three times larger near the source than far from it at the early stages of the evaporation and saturation process. When the amount of pheromone applied to the source was tripled (7 mg), the amount far from the source was almost tripled, or the saturation time was cut by factor of two to three.     

面向综合集成研讨环境的主动信息获取方法*

针对在综合集成研讨环境中,由于存在时间压力,传统的网络信息获取方法难以直接使用,提出了一种面向综合集成研讨环境的主动信息获取方法。该方法将领域词条与通用词条相结合,从发言文本流中实时提取话题,并在话题发生变化时自动生成检索词送入搜索引擎进行检索,再通过多个用户之间的协作推荐实现对重要检索结果的筛选。实验结果表明,这种方法可为综合集成研讨系统的用户提供及时、准确、上下文相关的信息服务。     

一种交流调速的高精度采样系统设计

基于TMS320F2812内部自带ADC模块的优缺点分析,探讨扩展ADS8365的高精度采样系统设计,以求提高整个系统的测量和控制精度,实现数字化变频调速系统中对多路电压、电流、转速等信号的高精度采样.讨论了影响TMS320F2812芯片A/D转换器精度的原因,给出了ADS8365芯片进行电流信号采样的电路设计,并通过仿真和实际电路实验说明了电路设计的有效性.相比于TMS320F2812的单端采样,基于ADS8365的采样电路具有采样精度高、速度快、同步性好、失真小、抗干扰强,同时能够较好的抑制温漂和热噪声等明显优势.将该采样电路应用于本交流调速系统中,不仅可以大大提高系统的采样精度,增加系统的抗干扰性,也便于系统工况的实时分析,进行合理控制及实时保护.     

蚁群优化算法在求解随机组合优化问题中的应用综述*

不确定条件下的优化问题更贴近真实世界环境,因而日益受到广泛关注。综述了蚁群优化在求解一组不确定条件下的组合优化问题,即随机组合优化问题方面的应用。首先介绍了不确定条件下组合优化问题的概念分类模型,给出了随机组合优化问题的一般定义;然后指出了其与求解传统确定性组合优化问题的不同之处,即目标函数的计算存在不确定性,并详细论述了目前解决方法的进展;最后分析了该领域值得重点关注的几个研究方向,并对其未来发展进行了展望。     

适用于有源电力滤波器的锁相环倍频电路

在有源电力滤波器（APF）设计过程中,需要实时检测谐波指令电流,基于锁相环倍频原理设计了一种基于硬件锁相环的同步采样方法,即锁相环倍频电路,实验结果表明：该锁相环电路能实现实时跟踪,且稳定可靠。     

Asynchronous rotation scan for synthetic aperture interferometric radiometer

Synthetic aperture interferometric technique has wide applications in optics, radio astronomy and microwave remote sensing areas. With the increasing demands of high resolution imaging observation, a new time-sharing sampling scheme of asynchronous rotation scan is proposed to meet the technical challenge of achieving a large equivalent aperture and overcome the operating barriers of space borne application. This configuration is basically composed by two asynchronously and concentrically rotating antenna groups, whose revolving radii and speeds are different. The synthetic aperture system with asynchronous rotation scanning scheme can effectively solve the trade-off problem of system complexity, and greatly simplify the system hardware at the cost of sacrificing a certain time resolution. The basic rules and design methods of asynchronous rotation scan are investigated The Gridding method is introduced to inverse the spiral sampling data for image reconstruction. The potential applications of geostationary orbit (GEO) earth observation and solar polar orbit (SPO) plasma cloud observation are explored with numerical simulations to validate the significance and feasibility of this new imaging configuration. Supported by the National Natural Science Foundation of China (Grant No. 40574070, 40671121, 40701100 and 40801136) and the National High-Tech Research Program of China (“863” Program) (Grant No. 2006AA12Z141)     

基于目标跟踪的粒子群粒子滤波算法研究

针对粒子滤波方法在重采样阶段容易造成样本有效性和多样性的损失,导致了样本贫化问题,提出了一种改进的粒子滤波算法.算法将粒子群优化思想引入粒子滤波中,在粒子采样过程前先利用粒子群算法进行优化.粒子群算法将最新观测值融合到粒子进化公式中,大部分粒子经过粒子群优化后,朝着后验概率分布比较密集的区域运动,聚集在最优粒子附近,使粒子的权值被提高,避免了在重新采样过程中被舍弃,进而缓解了样本被贫化问题.目标跟踪系统中的位置估计由于物体运动具有突然性,很难准确估计.采用非线性目标跟踪模型和分时恒定值模型分别研究改进粒子滤波算法对误差均方值的影响.仿真结果表明改进算法与常规粒子滤波算法和扩展卡曼滤波算法相比,更加有效地降低变量的误差均方值,从而提高了滤波性能.     

Gaussian sampling of lattices for cryptographic applications

Gaussian sampling is the major class of algorithms for solving the close vector problem(CVP)of lattices.In this paper we present a novel Gaussian sampling algorithm,which has the same cryptographic applications with original Gaussian sampling algorithms.Our novel Gaussian sampling algorithm has smaller deviations,meaning smaller space sizes of lattice based public-key ciphers.The shape of our novel algorithm is almost repeated implementations of original algorithm,with random repeating times.Major result is that the deviation can be reduced to 0.64～0.75 of that of original Gaussian sampling algorithm without clearly increasing the average time cost.     

机械电器产品检验抽样方法探讨

根据机电产品生产特点,对稳定生产状态下的生产条件进行细分,提出不同生产条件下的生产质量验收抽样方法。