Degradability and antigen-release characteristics of polyester microspheres prepared from polymer blends

Biodegradable microspheres were prepared to function as a depot system for the controlled release of a model protein antigen bovine serum albumin (BSA). As an approach to achieve its controlled release, microspheres were fabricated blending a high-molecular-weight poly-d,l-lactide-co-glycolide (M_w = 61,000) with a low-molecular-weight poly-d,l-lactic acid (M_w = 2000, PLA2000). The effects of PLA2000 on microsphere degradability and release characteristics of BSA from microspheres were investigated. On the basis of the pH change in microsphere suspensions and water uptake of microspheres, the kinetics of microsphere degradation was derived to describe the rate of formation of hydrogen ions due to hydrolysis of ester linkages of polymers. It substantiated that PLA2000-containing microspheres were subject to controlled degradation that was necessary to achieve continuous release profiles of the antigen. Immunization of rabbits by subcutaneous injection of BSA-containing microspheres enhanced the antigenicity of BSA, and significantly increased the duration of humoral immune responses. © 1995 John Wiley & Sons, Inc.     

焊丝熔化率公式研究

通过大量试验对碳钢焊丝，不锈钢焊丝和铝合金焊丝的熔化率进行了测定，应用半理论公式和试验相结合的方法测定和计算上述各种材料的焊丝熔化率中电阻阻热和电弧热所占的比例，对保护气体的影响进行了试验研究，测定了各种材料的焊丝熔化率公式中的有在常数，并对该 实用性进行了分析。     

Flame retardant epoxy polymers using phosphorus‐containing polyalkylene amines as curing agents

Two series of novel phosphorus‐containing poly(alkylene) amines with or without aromatic groups were synthesized via reacting phosphoryl chloride derivatives with commercially available polyetheramines, ethylenediamine and N‐phenyl‐1,4‐phenylenediamine, respectively. Chemical structures of the amines were characterized with FTIR, NMR, P (phosphorus) content measurement, and amine content titration. These amines were then utilized as curing agents to react with diglycidyl ether of bisphenol A for preparing phosphorus containing epoxy polymers. The introduction of soft ? P? O? linkage, polyalkyene, and hard aromatic group into the backbones of the synthesized phosphorus‐containing amine (PCA) provides epoxy resins with tunable flexibility. Thermal analysis of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) reveals that these resulted epoxy resins possess moderate T_g's and thermal stability. Furthermore, high char yields in TGA and high limited oxygen index (LOI) values indicate that these phosphorus‐containing epoxy (PCE) resins are capable of exhibiting excellent flame retardant properties. These polymers can be potentially utilized in flame retardant epoxy coatings and other applications. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3526–3538, 2001     

A two‐stage receiver with soft interference cancellation for space–time block code and spatial multiplexing combined systems

This paper presents a new space–time two‐stage receiver with the assistance of soft information for the Alamouti space–time block code (STBC) and spatially multiplexing (SM) combined multiple‐input multiple‐output (MIMO) systems, which possess both the advantages of high diversity gain and high data rates to entail the next generation wireless communication systems. The first stage of the receiver, utilizing the inherent structure of the STBC, consists of a bank of soft generalized sidelobe canceller (GSC)‐based detectors, each for every STBC block, and intends to yield a more precise initial estimate of the transmitted symbols. In the second stage, the groupwise detection is conducted successively by using the matched filters (MFs) to simultaneously detect the two consecutive symbols in one STBC block with the removal of the soft interferences in between. Since the interferences have been faithfully reproduced and thoroughly annihilated, the new receiver can yield accurate symbol detection even with simple MFs. Moreover, some extreme cases regarding the soft information employed in the new receiver and its extension to the multiuser (MU) MIMO downlink are addressed as well. Conducted simulations show that the developed receiver, with modest computational load, can provide superior performance compared with pervious works, especially in the MU MIMO downlink. Copyright © 2010 John Wiley & Sons, Ltd.     

镂空结构氧化镍微球的制备及性质研究

通过水热合成法,以葡萄糖酸钠与硝酸镍为起始原料,一步法制备了前驱体碳杂Ni(OH)2复合微球(C-Ni(OH)2)。然后以制得的C-Ni(OH)2微球前驱体,在空气氛围下进行焙烧,制备出镂空结构NiO微球。通过场发射扫描电镜(FE-SEM)、X-射线衍射(XRD)、X-射线能谱(EDS)和氮气吸附脱附(EBT)等实验方法对其进行了分析,结果表明该微球主要是由几十个纳米的颗粒结合而成。由于前驱体为碳杂Ni(OH)2复合微球,氢氧化镍不仅存在于该微球的表面,而是存在于整个微球中,所以导致了部分焙烧出的NiO空心球出现了特殊的"球套球"的结构。     

The effect of cobalt precursors on NO oxidation over supported cobalt oxide catalysts

The effect of cobalt precursors such as cobalt acetate and cobalt nitrate on NO oxidation was examined over cobalt oxides supported on various supports such as SiO₂, ZrO₂, and CeO₂. The N₂ physisorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature-programmed reduction with H₂ (H₂-TPR), NO chemisorptions, and temperature-programmed oxidation (TPO) with mass spectroscopy were conducted to characterize catalysts. The NO uptake as well as the catalytic activity for NO oxidation was dependent on the kinds of cobalt precursors and supports for supported cobalt oxides catalysts. Among tested catalysts, Co₃O₄/CeO₂ prepared from cobalt acetate showed the highest catalytic activity. The catalytic activity generally increased with the amount of chemisorbed NO. Reversible deactivation was observed over Co₃O₄/CeO₂ in the presence of H₂O. On the other hand, irreversible deactivation occurred over the same catalyst even in the presence of 5 ppm SO₂ in a feed. The strongly adsorbed SO₂ can prohibit NO from adsorbing on the active sites and also can prevent formed NO₂ from desorbing off the catalyst surface. The formation of SO₃ cannot be observed from the chemisorbed SO₂ on Co₃O₄/CeO₂ during TPO.     

NO oxidation over supported cobalt oxide catalysts

NO oxidation was conducted over cobalt oxides supported on various supports such as SiO₂, ZrO₂, TiO₂, and CeO₂. The N₂ physisorption, an inductively coupled plasma-atomic emission spectroscopy (ICP-AES), X-ray diffraction (XRD), NO chemisorptions, the temperature-programmed desorption (TPD) with a mass spectroscopy after NO or CO chemisorptions were conducted to characterize catalysts. Among tested catalysts, Co₃O₄ supported on ceria with a high surface area showed the highest catalytic activity. This catalyst showed superior catalytic activity to unsupported Co₃O₄ with a high surface area and 1 wt% Pt/γ-Al₂O₃. For ceria-supported Co₃O₄, the catalytic activity, the NO uptake at 298 K and the dispersion of Co₃O₄ increased with increasing the surface area of CeO₂. The active participation of the lattice oxygen in NO oxidation could not be observed. On the other hand, the lattice oxygen participated in the CO oxidation over the same catalyst. The deactivation was observed over Co₃O₄/CeO₂ and 1 wt% Pt/γ-Al₂O₃ in the presence of SO₂ in a feed. 1 wt% Pt/γ-Al₂O₃ was deactivated by SO₂ more rapidly compared with Co₃O₄/CeO₂.     

火炮磁流变阻尼器结构设计与优化

以火炮反后坐系统为对象,研究冲击载荷下磁流变阻尼器(Magneto-rheological Damper,MRD)的结构设计与优化.以冲击缓冲控制过程中需要的最大阻尼力为基本设计目标,设计了MRD的基本结构,进行磁路分析,得到了满足基本设计要求的阻尼器.在此基础上以最大可调系数和最小结构体积为优化目标,提出相应的设计变量和约束条件,用MATLAB实现结构的优化设计,并用ANSYS进行了具有磁场约束的结构优化.优化设计的结果表明,两种优化设计均能提高可调系数和减小结构体积,但MATLAB优化后的磁路性能并不十分理想,而ANSYS优化结果具有较好的综合性能.     

钢骨混凝土结构设计规程(YB9082-97)讲座 第一讲 总则及应用

针对钢骨混凝土结构的特点、性能及材料和规程ＹＢ９０８２－９１对钢骨混凝土在高层建筑 中的类型、布置、计算及设计等所作的规定作了简要介绍。     

Morphology,thermal and mechanical properties of the polyhedral oligomeric silsesquioxane side‐chain epoxy hybrid material

The side‐chain polyhedral oligomeric silsesquioxane (POSS)‐type epoxy (IPEP) hybrid material was synthesized, and the particle sizes of the POSS segment were less than 5 nm and which particles dispersed uniformly. The 3D AFM microphotograph of the IPEP/DGEBA (diglycidyl ether of bisphenol A) hybrid material exhibited the unique “island” shape, and their XRD pattern displayed amorphous halo structure. The POSS segments of the IPEP could improve the thermal degradation activation energies. Additionally, introduction of the IPEP into the DGEBA could improve the char yield and provide the antioxidation property in the air atmosphere. The char yields of the IPEP/DGEBA hybrid materials could improve from 14.48 to 19.21% and from 0.18 to 1.17% in the nitrogen and air atmospheres, respectively. The IPEP segments could also improve the hardness when the IPEP contents of the IPEP/DGEBA hybrid materials were less than 50 wt %. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010