The Effect of Comonomers on the Foaming Characteristics of Polypropylene

In the process of polypropylene (PP) polymerization, different kinds of PP are produced depending on the differences in the structural changes with the arrangement of comonomers. Each kind of PP has distinct properties, which arise from differences in the fundamental chain bonding structure of each polymer and affect not only the mechanical properties but also the foaming characteristics of each resin. Therefore, the fundamental foaming characteristics require experimental investigation. We examined the effects of PP polymerization on the foaming rate and solubility in the microcellular foaming process.     

Characteristics of the Skin Layers of Microcellular Injection Molded Parts

The cross-section of products made with the microcellular injection molding process shows the skin layer and the core region where the formation of pores takes place. The cell size, cell density, and cell morphology were found to depend on pressure drop rate, viscosity, cell growth period, and cell coalescence. However, research on the actual mechanisms of the skin layer is rare.

Cell morphology and skin layer are of importance as a factor influencing the density and strength of microcellular injection molded parts. Especially, as size of the injection molded parts becomes large, the skin layer size changes, resulting in variation of the foaming rate. Therefore, there is the need to study factors that influence the formation of the skin layer and its thickness.

This research proposes a hypothesis on the mechanism of the skin layer formation in microcellular injection molding process and addresses factors influencing skin layer thickness. In addition, the experimental design method was utilized to identify the factors, and the variation in physical properties with skin layer thickness was reported.     

机构与控制的协同设计

提出凸轮、连杆等传统机构与电、气、液等控制系统协同工作的理念,列举机构与控制协同系统的构成类型及应用领域,分析机构与控制的协同设计方法,指出机构与控制协同设计理论的研究内容并评述其科学意义及工程价值。     

A study of fatigue mesoscopic elasto-plastic properties of a nickel-base superalloy by instrumented microindentation measurements

In this study the fatigue mesoscopic elasto-plastic properties of nickel-base superalloy GH4145/SQ were investigated using the instrumented microindentation testing coupled with the analytic calculation. The indentation characteristic parameters of low-cycle fatigue specimens, such as the indentation curvature (C), the maximum penetration depth (h_max), the initial unloading slope (S), the residual depth of penetration (h_r), the recovered elastic work (W_e) and the residual plastic work (W_p), were determined from the experimental load–penetration depth (P–h) curves, and the fatigue mesoscopic elasto-plastic properties (E, σ_y and n) were estimated using a well-developed analysis algorithm proposed by Dao et al. The distribution patterns of the fatigue mesoscopic mechanical properties were further verified in a statistical sense. The dependence of the fatigue mesoscopic elasto-plastic properties upon the imposed strain amplitude was discussed preliminarily in terms of microstructural examinations of fatigue failure specimens.     

工程布局CAD系统设计与实现

针对工程布局设计的复杂性,提出了开放式的工程布局设计CAD系统的结构框架,讨论了实现该系统的关键方法,包括自动化设计进程建模、基于功能特征的待布物和布局空间几何近似建模、布局知识和布局约束的表达、布局方法应用.基于该系统框架,实现了计算机辅助工程布局设计原型系统,并以车辆动力舱布局设计为背景,对原型系统的有效性进行了验证.     

专用GPS车辆监控系统的设计与实现

描述了一个利用GPS、WebGIS、数传电台、RFID以及计算机网络等技术建立起来的专用GPS车辆监控系统,用于帮助海关监控运输途中的转关货物.详细阐述了工作流程、系统结构和关键技术,包括WebGIS、轨迹绘制、偏离路线判定、电台数据加密、电台调度、车载单元安全设计和车辆目标分组,分析了系统负载和应用效果.     

空中华西村复杂超限高层结构设计

空中华西村将一栋高316.5m钢筋混凝土中央筒体与三栋高252.6m的钢-混凝土组合结构外围塔体通过五道环向连体及径向连体连为一体,中央筒顶部支撑一个4层高的大型球体。整个结构属复杂超限高层建筑。设计中采用基于性能的抗震设计方法,利用多种分析手段验证不同水准下结构的抗震性能,重点解决了复杂连体、顶部收进、软土地基上的桩筏基础设计等问题。在大量分析计算的基础上,提出了相应的超限设计措施,使得结构能够更好地实现预定的性能目标。目前,工程已顺利通过超限设计审查,施工正在进行中。     

Study of nanoscale photopolymerized fullerene clusters in solution droplets using an ultrasonic nebulizer unit

In a designed and developed ultrasonic nebulizer system for obtaining macroscopic-quantity photopolymerized fullerene (C60) clusters, a C60 solution was vaporized to several micro-sized droplets in vacuum, resulting in the formation of C60 aggregates by evaporating the solvent (toluene). The system was invented to produce nanoscale photopolymerized carbon clusters through the irradiation of ultraviolet (UV) light on the C60 aggregates in vacuum. The products, photopolymerized C60 clusters obtained from the system using UV-visible (UV-Vis) absorption and high-performance (or high-pressure) liquid chromatography (HPLC) spectra, were characterized. Compared with the non-irradiating C60 solution, the UV-Vis absorption spectrum of the irradiated C60 solution was drastically decreased, especially at lambda = 335 nm and in the visible region from lambda = 450-650 nm. As such, the UV-Vis absorption spectra provide information about the polymerization of C60 molecules. These photopolymerized C60 clusters can be detected as having a heavy molecular mass order through the HPLC system, and the C60 and photopolymerized C60 cluster can be extracted from the trapped solution on the molecular mass. Although there is a possibility that the products include various forms of C60 clusters, the results suggest that the products obtained from the system using a vaporizer establish a new method of obtaining macroscopic-quantity C60 clusters.     

Uncertainty Analysis of Mound Monitoring for Recharged Water from Surface Spreading Basins

This study has conceptually reviewed issues related to implementation of a groundwater mound monitoring well (GMMW) for monitoring recharged water from a surface spreading basin with emphasis on uncertain hydrogeological conditions. For this, we selected a recharge site in the City of Mesa, Ariz., that is characterized with near-surface clay lenses of low permeability. A geostatistical simulation technique was used for generating hydrogeological fields under the recharge basin, using soil boring logs and historical hydrological data. More than 50 hydrogeological fields were generated and used for modeling. Five scenarios were formulated with varying parameter values and different initial and boundary conditions, and each scenario was evaluated with the 50 hydrogeological fields generated. Results of this study indicate that travel times to the mound may vary by over one order of magnitude and the use of a GMMW will only be practical for regulatory compliance in a homogeneous system.     

Approaches for obtaining sperm in patients with male factor infertility

OBJECTIVE: To describe methods of sperm retrieval for intracytoplasmic sperm injection (ICSI) in patients with male factor infertility and to review the clinical results using sperm from the different sources. DESIGN: The literature on sperm-obtaining methods and ICSI was reviewed. Studies related to this topic were identified through MEDLINE. RESULTS(S): This review describes the evolution of sperm retrieval methods. Sperm can be obtained by microepididymal sperm aspiration (MESA), percutaneous sperm aspiration (PESA), and testicular sperm extraction (TESE), from patients with congenital absence of the vas deferens or acquired vas obstruction. When ICSI is performed with ejaculated, epididymal, or testicular sperm, good fertilization and pregnancy rates are achieved without significant differences among the various sperm sources. The original percutaneous sperm aspiration method has been modified slightly and yields successful results. CONCLUSION(S): Viable pregnancies can be achieved with ICSI by using not only ejaculated sperm, but also epididymal and testicular sperm. Microepididymal sperm aspiration, percutaneous sperm aspiration, modified percutaneous sperm aspiration, and testicular sperm extraction can be considered standard procedures to treat male factor infertility.