高技术产品用无源元件与中国钽工业发展

世界高技术产品市场总体看呈增长趋势，预计2020年销售额将比2000年翻一番。以高技术产品为主要应用领域的电阻、电容、电感等无源元件，也将随着高技术产业的发展呈现出良好的市场前景，但是钽电容器市场近几年表现出骤涨急落的发展态势。由于钽电容器产能过剩，且面临着被替代的威协，因此价格将无法返回到2000年以前的水平，并呈现整体持续走低的趋势。中国的钽工业发展应注重提高企业自身的综合竞争力，加强企业间的沟通、交流与合作，维护我国钽工业的整体利益，增强环保意识，做好国外转移到我国的初级产品和低端产品生产的环保工作。     

火焰原子吸收光谱法测定电缆绝缘护套中的铅

提出了用空气—乙炔原子吸收光谱法测定电缆绝缘护套中的铅含量。铅在0.00~11.00μg.ml-1(r=0.9991)范围内有良好的线性关系。本法的RSD≤3.17%,回收率在97.2%~103.2%之间。     

Cable-direct-driven-robot (CDDR) with a 3-link passive serial support

Cable-direct-driven-robots (CDDRs) provided with a passive serial support represent an interesting and rising evolution of planar cable robots. The paper is devoted to present and analyze a novel CDDR robot. The robot consists in a fully actuated CDDR supported against loading normal to the motion plane with a 3-link passive planar serial manipulator. This hybrid structure combines positive features of both parallel and serial architectures, and prevents out-of-plane movements without the necessity for the robot to be supported on the motion plane. The adoption of a 3-link serial manipulator ensures a greater workspace area compared with similar structures that adopt a smaller number of links, and improves specific characteristics of their dynamics. Nevertheless undesired oscillations may occur since the serial manipulator is underconstrained. For this reason damping elements are inserted in the structure. Simulation examples are presented to demonstrate the novel CDDR concept and its dynamics. In addition, a strategy to select proper values of damping coefficients is presented.     

均匀橡胶弹性体隔声量的理论计算

由于材料在水声介质中的隔声性能的测试方法和测试设备较复杂，目前还没有在水声介质中的隔声量的标准测试方法。笔者从理论上研究了材料在水声介质中的隔声性能(隔声量)的计算方法，利用该方法计算了所合成的材料在不同厚度下的隔声量。计算结果表明：随着厚度的增加，材料的隔声量增加，但在低频下，当厚度增加到40mm以后，隔声量随厚度的增加而变化得很缓慢，在低频下不符合厚度每增加一倍，隔声量增加6dB这一规律。     

银杏内酯A和B的分离纯化研究

In this paper a simple preparative method for isolation and purification of ginkgolides A and B was developed,As starting material,a commercially available standardized ginkgo extract (EGb761,containing 24% flavonoid and 6% terpene trilactones) was used,After a pretreatment step,optimized by the uniform design method ,the concentrated intermediate extract with high content of GA and gb( 90%) was separated into the individual terpenes by preparative liquid chromatography eluted with petroleum ether-ethylacetate,Analysis of products was carried out by means of HPLC-ELSD(evaporative light -scattering detector),The results show that ginkgolides A and B are obtained in higher yield and better purity.     

A molecular level mechanism ofn-butane oxidation to maleic anhydride over vanadyl pyrophosphate

A molecular level mechanism is proposed for the highly selective 14-e^– oxidative transformation ofn-butane to maleic anhydride on the surface of vanadyl pyrophosphate. The mechanism suggests that the dimeric active sites assume at any given time, one of four possible interconvertible states which differ from each other in the number of available oxygen atoms and the formal oxidation states of the individual vanadium atoms. The relative ratios of active sites in each of the four possible states are dictated by the reaction conditions, the redox properties of the reacting gases and the structure of the vanadyl pyrophosphate active surface. A crucial feature of the mechanism is a pseudo-ozonide surface species formed by the interaction of a chemisorbed dioxygen molecule and an adjacent metal-oxo group. This unusual species is responsible for the initial activation of then-butane, which occurs when the chemisorbed dioxygen abstracts an H-atom from the alkane and the adjacent metal-oxo group reacts with the incipient alkyl radical to form an alkoxy group. The proposed mechanism is entirely consistent with literature reports describing the behaviour of (VO)₂P₂O₇ in flow, pulse and TAP reactors.     

一种反激式双输出DC/DC变换器的设计与实现

针对市场上DC/DC开关电源高压输出时,输出电压纹波较大问题,介绍了一种±50 V双输出DC/DC开关电源的设计方法及测试结果。该电路采用电流控制型PWM控制芯片,工作于反激模式。输入输出通过光耦实现隔离。该DC/DC变换器具有带负载能力强、纹波低、输出电压高等特点,可为电子设备提供稳定的供电电压。     

基于带缓冲的双通道开关技术的网络隔离器设计

在对网络隔离技术进行分析的基础上,研究利用网络隔离技术来解决网络安全问题。目前的网络隔离产品大多是采用基于硬件的开关控制,受限于现有硬件技术条件,并且厂家要根据不同用户要求而开发生产针对特定应用的网闸,不能方便地同时支持多种应用。提出了一种改进的安全隔离网闸实现方案。重点是模块化和软件方式实现开关技术,采用独立的软件开关控制和模块化设计,解决了现有物理隔离网闸产品在硬件开关控制和所支持应用上的限制,这种采用软件实现开关功能的方式避免基于现有硬件技术的可用性和寿命时间的限制。     

Possible effects of site isolation in antimony oxide-modified vanadia/titania catalysts for selective oxidation of o-xylene

Titania-supported vanadia catalysts were modified by addition of antimony oxide for application in o-xylene selective oxidation to phthalic anhydride. It was shown that active and selective catalysts can be prepared by ball-milling mixtures of powders of TiO₂, V₂O₅and Sb₂O₃followed by calcination. X-ray photoelectron spectroscopy proves the formation of highly dispersed overlayers of vanadium oxide and antimony oxide, in which V⁵⁺is partially reduced to lower oxidation states and Sb³⁺is partially oxidized to Sb⁵⁺. Antimony oxide segregated into the outermost surface layers. It is therefore inferred that the presence of the antimony oxide modifier spatially separates V–O species and leads to site isolation which may be responsible for the positive effect of the modifier for the catalyst's selectivity.     

被动桩中土拱形成机理的平面有限元分析

国内外对被动桩中土拱形成机理的研究比较少,尤其针对不同土性土体中这类问题的对比研究更是少见。借助平面有限元数值方法,对粘性土与无粘性土中被动桩间的土拱形成机理作了研究和对比分析,并讨论了土拱形成过程与土拱效应随土体参数如粘聚力、内摩擦角、弹性模量、剪胀角、泊松比、桩土接触特征的变化规律。研究表明:土性不同时,土拱形成过程中桩周土体的受力和破坏形式不同;剪胀角、泊松比、桩土接触特征对桩间土拱形成机理和效应影响明显。