Aggregation arrestant pheromone of the German cockroach,Blattella germanica (L.) (Dictyoptera: Blattellidae): Isolation and structure elucidation of blattellastanoside-A and -B

The aggregation pheromone of the German cockroach,Blattella germanica, consists of attractant and arrestant, which can be detected by olfactometer and choice-chamber assay, respectively. Both were extracted from the frass-contaminated filter paper being used as a shelter. They were separated by solvent partition withn-butanol and water. The arrestant from then-butanol phase was purified by open column chromatography and then successive HPLC isolated two major arrestant components. Spectral evidence from SI-MS, HR-EI-MS, and NMR experiments with pulse techniques provided possible structures as 1-(6-chloro-4,5-epoxy-5-stigmast-3-yl)--d-glucopyranoside and 1-(6-chloro-5-hydroxy-5-stigmast-3-yl)--d-glu-copyranoside, denoted as blattellastanoside-A and blattellastanoside-B, respectively. They represented arrestant activity as median effective doses (ED₅₀) at 0.044 (A) and 3.2 (B) nmol on 1.0 cm² of Whatman No. 1 filter paper.     

Piezo- and pyroelectricity in polymer blends of poly(vinylidene fluoride)/poly(methyl methacrylate)

Compatible polymer blends of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA) can be used as suitable model systems for investigating the relationship between the physico-chemical structure of polymers and their piezo- and pyroelectric activity. The structure of PVDF/PMMA blends can be varied over a very wide range which can lead to a strong influence on the piezo- and pyroelectric activity and the corresponding coefficients d₃₁ and g₃. The values of d₃₁ and g₃ were found to vary over nearly five decades whereas the normalized coefficients $\text{d}{}_{31}\text{P}$ and $\text{g}{}_3\text{P}$ remain largely unaffected. This emphasizes the importance of the molecular processes causing the macroscopic polarization P during the poling procedure. For a given polarization P and a given temperature T the properties of the polymer matrix, however, are far less important for the values obtained for d₃₁ and g₃. The experimental results were compared with theoretical predictions based on models which were recently developed by Tashiro et al., Broadhurst et al. and by Mopsik et al.. Considering the appropriate scope of each model a good agreement between theory and experiment is observed and general contradictions have not been found.     

新企业会计准则对装备价格管理的影响及启示

与原会计准则相比,新会计准则在会计基本原则和会计要素的计量方面发生了较大的变化,新准则在内容上充实成本要素,在可操作性上更加强调规范会计信息的质量。通过对新会计准则的变化内容、特点及作用方面分析,研究其实施对装备价格管理工作的影响,探讨新会计准则环境下如何提高装备价格管理水平等问题。     

汕头市城市定位与可持续发展战略研究

城市定位就是对城市未来发展方向和发展目标的拟定,是城市规划建设的重要组成部分.文章在对城市定位的涵义理解和城市发展战略思考的基础上,分析了城市定位与城市发展战略的互动机制,提出了汕头市新时期的城市定位.同时,提出并详细探讨了基于城市定位的汕头市可持续发展战略构想.     

基于工作过程的《异步电动机运行与维护》课程改革与实践

本文按照基于工作过程的系统化课程开发方法,对《异步电动机运行与维护》课程进行了教学设计。文中系统提出了该课程的构建方法、学习情境、学习内容、实施方案和考评方法等,简要分析了改革试点实践的初步成效与不足。     

Orientation of Bi<Subscript>3.2</Subscript>La<Subscript>0.8</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript> ferroelectric thin films with different annealing schedules

Fatigue-free Bi_3.2La_0.8Ti₃O₁₂ ferroelectric thin films were successfully prepared on p-Si (100) substrates using metalorganic solution deposition process. The orientation and formation of 5-layers thin films were studied under different processing conditions using XRD. Experimental results indicate that increase in annealing time at 700 °C after preannealing for 10 min at 400 °C can remarkably increase (200)-orientation of the films derived from the precursor solutions with two contents of citric acid. Meanwhile, high content of citric acid increases the film thickness and is conducive to the a-orientation of the films with the preannealing, and low concentration of the solution is conducive to the c-orientation of the films without the preannealing.     

基于空间分布特性和局部复杂度的显著目标检测算法

目前的视觉注意显著区域检测算法,主要依赖像素间的相互对比,缺乏从全局角度对显著目标的分析理解。依据显著目标是显眼、紧凑和完整的思路,提出一种基于目标空间分布特性和局部复杂度的无监督视觉注意显著目标自动提取算法。首先根据局部区域与其多个尺度邻域的对比,得到亮度显著图;然后利用颜色信息的显眼性、空间分布和区域一致性得到颜色显著图;同时通过对方向的空间分布和局部复杂度进行多尺度分析得到方向显著图;最后通过显著值的空间分布和面积增强因子相结合的融合策略得到输入图像的显著图,根据显著区域确定感兴趣区域位置,在基础上完成目标检测。将此方法应用于各类具有不同特点的彩色图像进行仿真实验,得到较好的检测结果,表明该算法是切实可行。     

Orientation angle workspaces of planar serial three-link manipulators

This paper presents a classification on the workspaces of planar serial three-link manipulators, that is, position workspace and orientation angle workspace. Position workspace indicates the region reached by the reference point on the end-effector. Orientation angle workspace indicates a set of angle ranges by which the end-effector can reach with certain orientation for every point in the reachable position workspace. By introducing a virtual equivalent mechanism, reachable position workspace can be divided into several Grashof intervals and non-Grashof intervals. The calculation equations of orientation angle workspace are deduced in three situations according to the relationships among four link lengths in the virtual four-bar chain. Three examples are given for three kinds of relationship of link lengths. The orientation angle workspace of extended groups, that is, two of the three link lengths equal, and the orientation angle workspace when the reference point on the end-effector moves along a non-radial direction are also discussed. A program is developed to calculate orientation angle workspaces and output variation curves of orientation angle workspace and key data within the position workspace. The approach and program in this paper can be used for fast calculation and identification of the variation rule of the orientation angle workspace of any given planar serial three-link manipulator on the basis of its link parameters, and for the design of a highly dexterous serial manipulator with proposed link relations. Supported by the Natural Science Foundation of Shanxi Province (Grant No. 20041070)     

我国个人所得税功能定位问题的思考

2009年我国税改的主基调是结构性减税,对于个人所得税改革的研究成为各界普遍关注的焦点之一。文章旨在探讨个税改革的一个前提性问题,即:我国个税的功能定位问题。文章借鉴西方经验,结合我国实际认为,现阶段个税成为我国税收体系主体税种的条件尚不具备,因此,目前我国个税应以调节收入分配功能优先。     

Evaluation of processing effects in injection‐molded amorphous and crystalline thermoplastics using an excimer laser

The ablation behavior of amorphous [polystyrene (PS), polycarbonate (PC)] and crystalline [PET, glass‐filled poly(butylene terephthalate) (PBT)] polymers by 248‐nm KrF excimer laser irradiation were investigated for different injection‐molding conditions, namely, injection flow rate, injection pressure, and mold temperature, as a possible method for evaluating processing effects in the specimens. For this purpose, dumbbell‐shaped samples were injection‐molded under different sets of processing conditions, and weight loss measurements were carried out for the different injection‐molding conditions. Some of the crystalline (PET) samples were annealed at different annealing times and temperatures. For PET, the weight loss decreased with increasing mold temperature and remained insensitive to injection flow rate. Annealing time and temperature significantly reduced weight loss in PET. For PBT, the weight loss due to laser ablation decreased with increasing material packing due to pressure, and it also showed some sensitivity to flow rate variation. The major effect was seen with glass‐filled PBT samples. The weight loss decreased drastically with increasing glass fiber content. Laser ablation allowed us to observe process‐induced fiber orientation by scanning electron microscopy in PBT samples. For PS and PC, the weight loss increased with increasing injection flow rate and mold temperature and decreased with increasing injection pressure. The position near the gate showed higher ablation than the position at the end for all the conditions. A decrease in the material orientation with injection speed and mold temperature led to an increase in the weight loss, whereas an increase in the injection pressure, and consequently orientation, led to a lower weight loss for PS and PC. Higher residual stress samples showed higher weight losses. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 2006