复杂环境下钢砼支撑爆破拆除

介绍了在周围环境苛刻的条件下,采用爆破方法拆除钢筋混凝土支撑的成功实例。给出了爆破方案的设计、参数的选取、爆破网路的连接、安全防护措施。为今后在环境复杂的条件下进行控制爆破拆除支撑积累了经验。     

独立钢支撑工具化水平模板支撑体系施工技术

采用合理、先进的模板及支撑体系配置方案,以降低模板、架料的投入成本,是确保项目预期收益实现的一个重要手段.天津嘉里中心采用了一种承载力大、稳定性高、用钢量少,周转次数多、适用性强的独立钢支撑工具化水平模板支撑体系.它不仅明显地降低了施工成本、提高了施工效率,同时也符合国家当前极力倡导的低碳经济和绿色施工的要求,增强企业在市场中的竞争力.     

硅胶负载型烯烃聚合催化剂的研究Ⅰ载体硅胶的宏观形态及热活化的影响

聚烯烃催化剂载体粒子的宏观形态在聚合过程中控制着聚合物产品粒子的宏观形态，并影响聚合催化剂的催化性能和聚合物产品性能。本文通过对催化剂载体Ｔ－１型硅胶宏观形态及其受热活化影响的研究，发现了活化过程中硅胶粒子存在着破碎和聚结现象。破碎粒子主要是粒径８０μｍ以上的大粒子，聚结粒子主要是１０μｍ以下的小粒子。还阐明了硅胶活化过程中，粒子的破碎、聚结以及硅胶粒子的流动分散性能、粒径分布、平均粒径、比表面积、孔体积、孔径的变化机制和规律     

New supports for enzyme immobilization based on copolymers of vinylene carbonate and β‐hydroxyethylene acrylate

Vinylene carbonate (VCA), β‐hydroxyethylene acrylate, and N,N′‐methylene bisacrylamide were dissolved in water, and the aqueous solutions were copolymerized via reverse‐phase suspension copolymerization in paraffin oil. A series of hydrophilic and beaded supports containing reactive cyclic carbonate groups for enzyme immobilization were obtained. The supports were examined by coupling with trypsin, and the results showed that the amount of enzymes coupled to the supports and the specific activity of the immobilized trypsin were related to the content of VCA structure units and the reaction time. Meanwhile, the optimal pH and temperature, as well as the Michaelis–Menten constant K_m, for both native and immobilized trypsin were measured. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 94–102, 2002     

Acoustic emission and fracture behavior of GFRP woven laminates at cryogenic temperatures

This paper describes an experimental and analytical study on fracture and damage behavior of GFRP woven laminates at cryogenic temperatures. CT (compact tension) tests were carried out at room temperature, liquid nitrogen temperature (77 K) and liquid helium temperature (4 K) to evaluate the critical values of the fracture mechanics parameters. During the CT tests, AE (acoustic emission) method was implemented. AE signals can identify the critical load at which gross failure occurs. A FEA (finite element analysis) was also applied to calculate the fracture mechanics parameters. The failure criteria (Hoffman criterion and maximum strain criterion) or the damage variable based on the continuum damage mechanics was incorporated into the model to interpret the experimental measurements and to study the damage distributions within the specimen. Several methods of calculating J-integral are discussed.     

球形MgCl_2负载Ziegler-Natta催化剂的制备及内给电子体作用机理的研究

应用低速搅拌法制备了球形MgCl2·nEtOH载体,Ticl4处理两次,氩气鼓泡法较好地控制了催化剂的颗粒形态,将所制得的球形催化剂催化丙烯聚合得到颗粒形态较好的球形聚丙烯颗粒。研究表明,内给电子体参与活性中心的形成,影响聚合物的规整性,并提出了可能的作用机理。     

炭担体结构和表面改性对镍催化甲醇气相羰基化的影响

考察了各种炭担体的结构和表面改性对甲醇气相羰基化的影响。利用ＢＥＴ、碱滴定、ＸＰＳ、ＴＧ、ＸＲＤ等方法对担体和催化剂进行了表征。比较了不同催化剂活性随时间的变化。结果表明，羰基化活性与担体表面积无一定关系，与孔结构关系密切。氧化碳负载的催化剂，Ｎｉ还原受到抑制，诱导期较长，但活性稳定性较好，还原碳负载的催化剂则与之相反。     

Surface photochemistry: efficient photocatalysis by CdS supported on a solid surface

The photocatalytic efficiency of a series of CdS samples: (i) a colloidal solution in aqueous CH₃CN; (ii) suspensions of (a) supported colloidal particles, (b) bulk CdS, and (c) commercial powders, was compared with respect to stilbenec-t isomerization. The samples of type (ii a), prepared from cadmium chloride and H₂S showed a high photocatalytic activity, attributable to the combined effects of the catalyst particle size and the presence of chloride ions. Increased activity over the commercial sample was also shown in the conversion of hexamethyl(dewar)benzene to hexamethylbenzene, and in the cleavage of anthracene dimer. It has been found that bulk CdS is activated by grinding with < 10% of certain metal chlorides and bromides.     

载体酸碱性对钒基催化剂丙烷氧化脱氢性能的影响及其IR和EPR研究

应用ＩＲ和低温ＥＰＲ等方法研究了载体酸碱性对钒基催化剂丙烷氧化脱氢性能的影响。从ＶＳｎＯ、ＶＳｉＯ、ＶＴｉＯ、ＶＡｌＯ到ＶＭｇＯ，随着载体的碱性增强，丙烷转化率和丙烯选择性均提高，然而从ＶＭｇＯ、ＶＣａＯ、ＶＳ－ｒＯ到ＶＢａＯ，随着载体碱性的进一步增强，丙烯选择性仍提高，但丙烷转化率显著降低。这些结果表明，只有适度增强催化剂的碱性，才有利于生成Ｖ４＋离子，减少表面碳酸盐的生成，并缩短脱氢中间体在催化剂上的停留时间和促进丙烯的脱附，减少Ｃ－Ｃ键断裂和转化为ＣＯｘ的机会，从而有利于丙烷氧化脱氢生成丙烯。     

组合式基坑支护结构在基坑施工中的运用

通过一项大型工程组合式基坑支护结构基坑支护的实例,根据不同的场地特点及地质情况,针对不同情况采取因地制宜的围护施工技术。