Adhesives in construction: A contractor's viewpoint

The development of epoxy- and polyester-based adhesives has dramatically widened the scope of adhesive bonding in the civil engineering industry but the technology of the adhesives used has often been more appropriate to the workshop than to the construction site. There is a need for the suppliers of structural adhesives to recognize this and to develop compositions and application techniques more amenable to site use. It is equally necessary for the construction industry to make more effort to understand these materials, to take advantage of their outstanding properties, and hence to use them successfully for the construction and repair of concrete structures.     

Prediction of gas flow directions in gas assisted injection molding when cavities and runners are involved

In the prediction of gas flow-direction for gas-assisted injection molding (GAIM), the statement“Gas goes to the direction of the last area to fill with resin”, has been accepted as a correct one. When there exists more than one area to fill with resin, a mold design engineer for GAIM technologies has to determine to which direction gas goes that commercial software for GAIM (e.g., Moldflow) may be utilized for its mold design. However commercial software is generally expensive and is sometimes hard to become familiar with. As a rule of thumb, it is suggested that the resistance to the initial velocity of melt polymer at the nearest geometry to a gas injection point should be used as its criterion since gas goes in the direction of least resistance to initial resin-velocity. Neither the flow rate nor the resistance to flow rate can be a criterion in the prediction. Thus the statement“Gas goes to the direction of the least resistance to flow rates”, should be corrected to“More flow rate goes to the direction of the least resistance to flow rates.”, The rule of thumb suggested in this paper was verified by using commercial software, Moldflow, in the prediction of gas flow directions in GAIM under geometries where cavities and runners were involved. When the ratio of initial resin-velocity is so close to unity it is proposed as the adapted rule of thumb to calculate new emerging resin-velocities and resistances to resin-velocity at the first coming change of diameters in series of pipes and to compare those for upper and lower sides each other to predict the gas direction. Thus the judgment as to which point is the point where gas starts to choose a preferred direction is very important in the prediction.     

Consolidation of sand formation using freon'll gas hydrate

Freon 11 gas hydrate was used to block the pores of four size ranges of sand from 24 mesh to 60 mesh. A 50.8 mm deep bed of sand when thus “frozen” with hydrate could sustain a dfferential water pressure of at least 6895 kPa. A subcooling of about 5 to 6°C below its thermodynamic formation temperature was required to cause the hydrate to form such a plug. Once formed, the hydrate remained stable at temperatures up to its decomposition temperature. The time required for the hydrate crystal to grow to a size large enough to block the pores of the bed was about two hours. The amount of hydrate forming agent required to block the sand pores was found to be approximately that calculated from the ideal composition of the hydrate.     

绿色环保意识的趋向

随着消费者环保意识的提高,人们除了认清绿色环保能对社会和全世界起到巨大的促进作用,还认为绿色环保能够直接、积极地反映其社会地位,在某种程度上反映出消费者自己的绿色环保意识。介绍了消费者对"绿色化"的认识,对"绿色产品"的期望以及生产厂家对"绿色原料"的认证和对"可持续发展"所做的贡献。     

岩体结构面对大跨度隧道工程稳定性影响初步研究

基于对沈阳至大连（简称沈大）高速公路扩建工程韩家岭隧道区域调查和分析，研究了岩体结构面对隧道施工过程的影响，围岩失稳方式及可能遇到的问题，并提出了解决这些问题的措施。     

Long-term residual value of North Carolina and Queensland rock phosphates compared with triple superphosphate

The effectiveness of large single applications of North Carolina reactive rock phosphate, Queensland non-reactive rock phosphate, and Calciphos, were compared to the effectiveness of superphosphate in field experiments in south-western Australia for up to 11 years after application. As measured using plant yield, superphosphate was the most effective fertilizer in the year of application, and relative to freshly-applied superphosphate, the effectiveness of the superphosphate residues declined to be about 15 to 65% as effective in the year after application, and 5 to 20% as effective 9 to 10 years after application. Relative to freshly-applied superphosphate, all the rock phosphates were 10 to 30% as effective in the year of application, and the residues remained 2 to 20% as effective in the 10 years after application. The bicarbonate soil test reagent predicted a more gradual decrease in effectiveness of superphosphate of up to 70% 10 years after application. For rock phosphate, the reagent predicted effectiveness to be always lower than for superphosphate, being initially 2 to 11% as effective in the year after application, and from 10% to equally as effective 10 years later. Therefore rock phosphates are unlikely to be economic alternatives to superphosphate in the short or long term on most lateritic soils in south-western Australia.     

Fracture of mica-reinforced polypropylene: Mica concentration effect

Concepts of post-yield fracture mechanics were used to characterize the crack initiation and propagation resistances of mica-reinforced polypropylene containing different mica concentrations. Although mica addition leads to an apparently brittle composite, the crack initiation resistance is slightly increased with mica concentration up to 10 percent by weight; and significant improvement in crack propagation performance was found for polypropylene reinforced by up to 20 percent of mica in comparison to that of virgin polypropylene. The debonding of the interface between mica flakes and the matrix leads to a micro-ductility ahead of the crack tip in which the matrix is able to pull-out from mica particles and to stretch. This micro-ductility also prevents the brittle, unstable crack propagation, which is due to the coalescence of voids in pure polypropylene. Above 20 percent of mica, the reduction of the effective amount of the matrix material results in a substantial drop in the resistance to crack growth of mica-reinforced polypropylene.     

Surface crosslinking of polyethylene and adhesive joint strength

Exposure of polyethylene film to UV radiation at wavelengths of ≤2537 Å is sufficient to induce surface crosslinking and to facilitate the formation of strong adhesive joints to these surfaces with conventional adhesives. Reduction of the vapor pressure in the reaction vessel to about 1 torr apparently maximizes the efficiency of the crosslinking process. Examination of the treated films which have been exposed for times necessary to form strong adhesive joints has revealed an absence of surface oxidation. It appears that crosslinking to improve the mechanical strength of the surface region of the polyethylene is sufficient to allow the formation of strong adhesive joints.     

尿素设备腐蚀的影响因素分析及防腐措施

针对尿素生产的特点,分析了对尿素设备腐蚀的影响因素:介质温度、氨碳摩尔比、水碳摩尔比、氨基甲酸铵溶液浓度、氧含量、硫含量、氯离子含量和介质流速等。提出了正常生产和停车封塔2种情况下的防腐措施。正常生产期间要严格控制如下指标:操作温度、系统的加氧量、硫含量、氯离子含量、氨碳比和水碳比;停车期间要严格控制系统的氨碳比和水碳比,同时根据不同状况来确定停车封塔时间。     

生成兴趣的大学教学

大学教育不仅仅是教给学生课本上的知识,更重要的是教会他们学习的方法,如何去获取有用的知识,以及如何利用所学的知识去解决实际问题。如何培养大学低年级学生的学习兴趣,如果引导他们主动去学习,在化学实验课上,又如何主动细致的去完成动手部分的学习,将是我们大学教学工作中急需要改进和提高的重要部分。     

Effect of autoxidation prior to deodorization on oxidative and flavor stability of soybean oil

Summary Oxidation prior to deodorization was shown to be detrimental to the flavor and oxidative stability of soybean oil. The increase in the nonvolatile carbonyl content of freshly deodorized oils was proportional to the peroxide value of the oils before deodorization. Rate of loss of flavor and oxidative stability of the oil were related to the extent of carbonyl development. All oils, whether or not they had been submitted to any known oxidation, contained some nonvolatile carbonyls. The loss in stability was not due to a loss of the antioxidant tocopherol. Oxidized soybean oil methyl esters were shown to develop nonvolatile carbonyl compounds upon heating at deodorization temperatures. The addition of isolated methyl ester peroxide decomposition products to deodorized soybean oil reduced its flavor and oxidative stability in proportion to the amount added. The results obtained were parallel and similar to those obtained by oxidizing soybean oil prior to deodorization. Flavor deterioration and undesirable flavors were typical of aging soybean oil whether or not the oils were oxidized before deodorization or whether an equivalent amount of nonvolatile thermal decomposition products was added to the oil. These oxidatively derived, nonvolatile carbonyl materials are believed to enter into the sequence of reactions that contribute to flavor instability and quality deterioration of soybean oil. The structure of these materials is not know. This work indicates the importance of minimizing autoxidation in soybean oil particularly before deodorization to insure good oxidative and flavor stability. Presented at fall meeting, American Oil Chemists’ Society, October 20–22, 1958, Chicago, Ill. This is a laboratory of the Northern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

基于大数据分析的废旧塑料利用率算法

概述了我国废旧塑料再生利用现状及应用领域,通过大数据回归分析建立了废旧塑料利用率的算法模型,测算我国2009—2019年的废旧塑料利用率.2009—2014年,废旧塑料利用率从12.0％升至16.0％,2015—2019年略微下降.2009—2015年,塑料回收利用量持续增长,2016年,回收利用量有所下降,2017—...     

浅谈职业学院学生的挫折教育

文章探讨了职业学院开展挫折教育的必要性,教育学生正确看待挫折,充分认识挫折的积极作用,克服挫折的消极影响,培养良好的意志品质.文中主要阐述了如何培养学生对挫折的承受能力,如何培养良好的品质意识以及在当前形势下引导学生如何面对挫折.     

Glass Formation, a Contemporary View

The process of glass formation is discussed from several perspectives. Particular attention is directed to kinetic treatments of glass formation and to the question of how fast a given liquid must be cooled in order to form a glass. Specific consideration is paid to the calculation of critical cooling rates for glass formation, to the effects of nucleating heterogeneities and transients in nucleation on the critical cooling rates, to crystallization on reheating a glass, to the experimental determination of nucleation rates and barriers to crystal nucleation, and to the characteristics of materials which are most conducive to glass formation.     

Developments in coatings for military vehicles

Conclusions  The MOD operates a wide range of transportation equipment and to ensure that these systems are able to operate in a range of environments a suite of advanced coatings are needed. Environmental legislation has provided a major impetus to introduce new coatings but in addition to the introduction of materials with low solvent contents it has provided an opportunity to introduce materials with improved performance. Unique to the military environment is the need to develop new materials with specific properties to counteract electromagnetic surveillance techniques. In order to undertake this work, knowledge relating to the interaction of electromagnetic radiation with matter as well as paint technology is needed. A third driver in the pursuit of advanced coatings is the need to seek cost effective technology in an age when government departments are under pressure to provide greatest value for money.     

高效、清洁、高附加值原则指导下适度、有序发展煤化工产业

针对我国可持续发展面临的能源瓶颈,指出适度、有序发展煤化工产业是我国现有能源结构环境下的必然选择。在低碳理念指导下,提出了煤炭资源的分质利用原则、高能效利用原则、综合利用原则、因地制宜利用原则和高附加值利用原则,比较分析了煤的各种化学转化途径,阐述了含氧醇醚材料替代石油路线、煤制芳烃、煤/天然气/煤层气制备乙炔等具有前景的清洁、高效转化过程,期望为煤化工产业的健康、有序发展提供科学思路。     

煤或天然气经甲醇制低碳烯烃工艺研究新进展

由煤或天然气经甲醇制低碳烯烃工艺是解决石油资源紧张、低碳烯烃需求量越来越大等问题的有效路线。介绍了几种有代表性的经甲醇制低碳烯烃工艺,包括美国UOP/Hydro甲醇制烯烃工艺,中国科学院大连化学物理研究所的合成气经由二甲醚制低碳烯烃(SDTO)工艺,德国Lurgi公司的甲醇制丙烯工艺,以及甲醇制烯烃与AtoFina/UOP烯烃裂解的集成工艺;分析了各工艺目前达到的技术指标及最近的技术改进,关注了各工艺近几年的工业化进程。除了SDTO工艺外,其他几种工艺有望在未来几年内实现工业化。国内甲醇制低碳烯烃工艺的开发应借助于流化催化裂化成熟的工程设计经验,同时加大甲醇制烯烃工艺流化床催化剂的开发力度。     

从日本循环型社会的形成和改进中学习

近年来,中国重视了节能环保问题,提出了走可持续发展的循环经济道路。学习先进国家有关环境的立法是很有必要的。日本依据再生利用法,不断改进提高再生技术,促进有效利用循环资源,减缓了废弃物的排放。但它以扩大生产、产生大量废弃物为前提的再生利用形式不断扩大;此外,为了减少再生成本和第二次环境污染,把废弃物输出国外。本文从这几方面对日本的循环型社会形式的矛盾进行解析,并引以为戒,为建立适合中国国情的循环经济社会体制提出建议。