步进电机在红外系统扫描机构中的应用

介绍了在红外系统中，采用步进电机作为扫描机构驱动元件，以Ｄ／Ａ数模转换器作细分方式的定频脉宽调制驱动方式，实现微机控制下的扫描机的构步距均匀稳定，满足红外系统分辨率的要求。     

一种简易可靠的射频激光调制器

采用ＰＩＮ电调衰减器、ＴＬ４９４等元件组成了射频（ＲＦ）大功率ＣＯ２激光调制器，调制频率、占空比和调制度单独可调。给出了电路的工作原理和测试结果。     

Service Load Effective Compression Flange Width in Fiber Reinforced Polymer Deck Systems Acting Compositely with Steel Stringers

This paper reports on the field study of a steel stringer-fiber reinforced polymer (FRP) deck composite bridge in Pennsylvania. The objective of the study is to assess the effective compression flange width in the FRP deck and floor systems when they act compositely with underlying steel girders at service conditions. The research results reported herein support the notion of employing a design approach, for both interior and exterior girders of a composite floor system, that is philosophically consistent with current practice related to steel girders acting compositely with concrete decking. It appears from the results presented herein that FRP decks and floors acting compositely with underlying steel girders exhibit an effective width that is close to the actual girder spacing for interior beams, and approximately one-half this value for exterior beams.     

Effect of fluoropolymer antidripping agent on the microstructure and properties of polyesters

Poly(ethylene terephthalate) (PET) is of excellent mechanical properties and melt processability and is widely used as raw material for textile fibers. However, the flame retardant properties of PET were rather poor, and both reactive and additive phosphorus- and halogen-containing compounds have been employed to enhance the reaction-to-fire properties while the meltdripping behaviour during burning hasn’t been handled properly with the flame retardants. In this work, fluoropolymer was blended with both pure PET (pPET) and reactive phosphorus-containing flame retarded copolyester (fPET), and the flame retardance and char formation and mechanical properties of the resulted pPET and fPET blends were investigated. The tensile strengths of modified pPET samples were worsen whereas those of modified fPET samples were improved at low concentrations. The initial thermal degradation in nitrogen was accelerated remarkably for the two polyesters with fluoropolymer. The oxygen indices of the all modified samples were reduced while char formation and meltdripping suppression were encouraged. The apparent melt viscosity and elasticity for the two polyesters were gained much with antidripping agent. Therefore, fluoropolymer improved char formation of the two polyesters based on the gaseous phase mechanism while the partial suppression of meltdripping behavior and the decrease of mechanical properties mainly originated from the increase of melt viscosity via fibrillation for pPET.     

Flame retardant and the degradation mechanism of high impact polystyrene/Fe-montmorillonite nanocomposites

High impact polystyrene/Fe-montmorillonite (HIPS/Fe-MMT) nanocomposites were successfully prepared by melting intercalation. The nanostructures of HIPS/Fe-MMT were testified by X-ray diffraction (XRD) and transmission electron microscope (TEM). Corresponding to pure HIPS, the thermal stability of HIPS/Fe-MMT nanocomposites was notably improved. The peaks of heat release rate (PHRR) and the mass loss rate (MLR) were significantly reduced after the formation of the HIPS/Fe-MMT nanocomposites from cone calorimetry. And nanocomposites PHRR was further lower with the increase of Fe-MMT content in the range of 1 to 5 wt%. The degradation mechanism of HIPS and HIPS/Fe-MMT nanocomposites was conducted by pyrolysis gas chromatography mass spectrometry (Py-GC-MS). And the reason of the enhancement of thermal stability maybe is that structural iron is the operative site for radical trapping in the Fe-MMT and the nanostructure enhances the interaction of the chains of the HIPS.     

燃料变化对气体燃烧器燃烧性能影响的数值模拟研究

该文以John Zink公司一种瓦斯燃烧器为几何原型,对燃烧器和稳焰旋流器附近三维复杂形状未作任何简化,生成了包括燃烧器和炉膛的结构化网格,换用甲烷、乙烷、丙烷和丁烷四种不同的气体燃料,用标准的k-ε湍流模型、k-ε-g湍流扩散燃烧模型和蒙特卡洛辐射换热模型对燃烧器内的流动及燃烧状况进行了全尺寸数值模拟,预报了燃烧器内流场和温度场,考察燃料变化对炉内温度场的影响规律及燃气射流特性参数(Re·D1)对火焰长度的影响,对进一步优化设计燃烧器、提高加热炉热效率有很好的指导意义。     

脉冲电镀的正向电流密度对深镀能力的影响

主要通过在正反向电流比、频率、脉冲宽度一定的条件下,改变正向电流密度的大小来研究其对PCB整板电镀铜深镀能力的影响。从测得的数据可知随着正向电流密度的增大,深镀能力先变大后变小,并对这个问题进行了理论分析。     

一种转移脉冲宽度可调的CCD驱动电路

本文以TCD132D线阵CCD为例,介绍了一种用循环计数器和拨码开关共同作用改变CCD转移脉冲的CCD驱动电路。该电路结构简单,工作可靠,调整方便。     

几种火焰喷焊自熔性合金层的耐磨性能

研究了不同自熔性合金粉末火焰喷焊层的显微组织与抗磨粒磨损性能，并对其磨面形貌进行了ＳＥＭ观察分析。结果表明，在Ｎｉ６０自熔性合金中加入适量的镍包ＷＣ粉末可明显提高其喷焊层的抗磨粒磨损性能。当ＷＣ的加入量为３５％（ｗｔ）左右时，该喷焊层与６０Ｓｉ２Ｍｎ调质钢相比，相对的耐磨性可提高６倍以上。     

原子吸收分光光度法测定焦锑酸钾中锑含量

比较详细地研究用火焰原子吸收分光光度法测定焦锑酸钾中锑含量的技术条件和测定方法。