汽车后市场准入门槛亟需设防

任何市场都是有规则的,没有标准的市场是短暂的.经销商要有一个好的经营环境,必须把这个门槛设好. 汽车后市场还需要准入门槛? 李庆云现任天津环渤海汽车城董事长并身兼天津市交易市场协会会长,在没有跨进汽车行业之前,一直觉得这样的问题多余:哪个行业没有准入门槛?等自己在天津建立环渤海汽车城之后,才意识到,中国的汽车后市场是多么需要"设防".     

注射成型塑化过程的可视化实验研究

利用自行开发的可视化实验装置对注射成型的塑化过程进行了系统的观察,着重讨论了不同的工艺条件对塑化性能的影响,同时借助示踪粒子对塑化过程的重要参数——固相速度进行了测量。实验所取得的数据为注射成型熔融模型的建立和对模型的验证提供了依据,同时也是注射螺杆优化设计的基础数据。     

Cr(Ⅵ)氧化鸡冠花红的褪色反应及其应用

在90℃的水浴加热条件下,C r(Ⅵ)能氧化鸡冠花红使其显著褪色,且褪色程度(ΔA与C r(Ⅵ)的量在一定范围内成正比关系,据此,建立了测定C r(Ⅵ)的新方法。线性范围为0~10μg/mL,表观摩尔吸光系数为2.2×104L/(m o l.cm)。方法用于镀铬溶液和铬酸钝化液中C r(Ⅵ)和C r(Ⅲ)的测定,结果满意。     

金属镍电沉积中枝晶分形生长的研究

将分形几何与电化学原理相结合,通过改进的有限扩散凝聚模型(diffusion-limited aggregation,DLA),采用基于Microsoft Visual C 6.0的Open GL编程,对点电极为阴极进行二维电沉积时沉积产物的形貌进行了模拟.以环形金属镍为阳极,石墨为阴极,用自行设计的试验设备制备了二维的金属镍枝晶以验证模拟结果.结果表明,在保持电压恒定的条件下,镍沉积层的形貌特征为具有分形结构的枝晶,这与采用DLA模型模拟所得的二维枝晶形貌具有相似性,表明该模型对枝晶电沉积的实验研究具有很好的指导意义.     

数字水准仪的测量原理及测试精度分析

在电子水准仪的3种读数原理(相位法、相关法、几何法)中主要介绍了几何法,结合索佳电子水准仪SDL30M在实验场进行了视距长度测量、调焦质量、标尺前后左右倾斜和遮挡程度试验,并利用已有实验场进行了水准测量的对比实验,分析了上述实验结果,得到了以下几点结论:1)仪器实测精度与标称精度基本相符。2)视距测量误差与视距长度成正比,基本呈线形关系,100 m的视距长度误差一般不会达10 cm。3)调焦质量对观测成果(中丝读数)影响很小,但数据显示时间会相应延迟。4)在2°范围内标尺左右倾斜影响较小,一般在1 mm以内,超过2°误差迅速增大;标尺前后倾斜在2°范围影响较小,读数误差一般在0.2 mm以内,超过2°误差迅速增大。5)遮挡容许程度与距离有关,距离越近,容许遮挡率越低;距离越远,遮挡率越大。6)对某水准网对比测量表明采用该仪器完全可以满足工程二等水准测量要求,而且精度高、速度快。     

环保型木器涂料

介绍水性和紫外光固化两类环保型木器涂料及其研究进展。水性木器涂料主要为丙烯酸酯与聚氨酯两大类，其研究进展集中表现为乳液改性，包括自交联、共混共聚、微乳液等；紫外光固化木器涂料包括其光固化树脂、活性稀释剂和光引发剂的功能及进展；指出研究新型乳液以提高水性木器涂料涂膜的表面性能，开发新型原材料以降低紫外光固化木器涂料的成本、扩大适应范围将成为今后环保型木器涂料的研究重点。     

Properties of poly(n‐butyl methacrylate) prepared by reverse atom transfer radical polymerization in an aqueous dispersed system

Reverse atom transfer radical polymerization (ATRP) of n‐butyl methacrylate (BMA) in waterborne media using Cu(II) complexes with azo initiators (i.e., reverse ATRP) was conducted. The influence of several factors, such as surfactant, catalyst, and reaction time, on the stability of the emulsion, the particle size, the morphology of the emulsion particles, and the control of the polymerization was investigated. The results showed great differences between ATRP and conventional emulsion polymerization, especially the nucleation mechanism and the kinetics. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1542–1547, 2003     

五种化合物临界温度和临界压力的测定

The critical properties of five compounds,including propanal,butanal,1-pentanal,2-methel butanal and trimer of ethanal,were determined for the first time by a new capillary quick-flow method. The apparatus was improved with a capillary tube and checked with hexane and 1-heptene as standard reagents. The experimental results proved that the determination of critical properties by quick-flow method with a capillary tube apparatus was successful.     

激光诱导二甲基二乙氧基硅烷气相合成碳化硅超细粉

本工作首次采用有机硅试剂二甲基二乙氧基硅烷为反应物，进行了激光导气相反应，制备出平均粒径为４０ｎｍ的非晶ＳｉＣ粉末，粉末中Ｃ／Ｓｉ比随反应气流量的变化而变化。非晶ＳｉＣ粉末在１８７３Ｋ，氮气中退火１ｈ后转变为β－ＳｉＣ及α－ＳｉＣ，同时，粉末中部分氧杂质及自由碳脱出粉末。     

Perylene derivative sensitized multi-walled carbon nanotube thin film

Perylene-sensitized multi-walled carbon nanotubes (PV-MWNT) have been prepared by a π-stacking between nanotubes and perylene derivatives, N,N′-diphenyl glyoxaline-3,4,9,10-perylene tetracarboxylic acid diacidamide (PV). The resultant nanocomposites have been characterized by transmission electron microscope (TEM), UV-vis absorption, photoluminescence (PL) and photocurrent spectra. Long range ordering can be observed in the form of PV-MWNT via π-stacking by TEM. Red-shift in the optical spectra consisting of the UV-vis absorption and PL spectra with the attraction of PV on the surface of the MWNTs were observed. The evident quenching in PL spectra of PV-MWNT was ascribed to the absorption and transfer of recombination energy by MWNT. Photosensitivity spectra demonstrated an increasing photocurrent in the ultraviolet region and a broadening photosensitivity in the red spectral region for solar cells based on PV-MWNT.