高速线材轧机Ф410mm离心铸造复合球墨铸铁轧辊的研制

介绍了高速线材轧机Ф410mm离心铸造复合球墨铸铁轧辊的试制过程。着重论述了材质选择、球化孕育处理和离心铸造工艺参数控制等问题。试制的轧辊在马鞍山钢铁公司高速线材轧机上使用，轧制量达到了国外设计要求和进口轧辊水平。     

Φ840 mm自动轧管机回送辊的研制

介绍了Φ840mm自动轧管机回送辊的工况条件,该轧辊成分选择原则、铸造工艺、球化孕育处理工艺等。研制出的自动轧管机回送辊综合指标符合GB/T1504—91标准,轧辊的强韧性、耐磨性好,达到同类产品较好水平。     

高速线材轧机φ410mm离心铸造复合球墨铸铁轧辊的研制

介绍了高速线材轧机φ410 mm离心铸造复合球墨铸铁轧辊的试制过程。着重论述了材质选择、球化孕育处理和离心铸造工艺参数控制等问题。试制的轧辊在马鞍山钢铁公司高速线材轧机上使用,轧制量达到了国外设计要求和进口轧辊水平。     

轻稀土镁复合球化、孕育处理工艺在轧辊生产中的应用

叙述生产轧辊类超厚大断面球墨铸铁件所用的轻稀土镁球化剂、孕育剂和复合球化、孕育处理过程及其对原铁水的要求,同时介绍了所生产轧辊的组织、性能和良好的使用效果。     

球墨铸铁轧辊的石墨形态及其对抗拉强度的影响

轧辊系特大断面铸件,铸后冷却速度缓慢,不易得到球状石墨。但是,严格控制铁水的化学成分,合适的碳当量(K=3.4～3.8),采用纯镁做球化剂,合适的镁处理温度,缩短处理后到浇注的时间,可以防止球化衰退,获得球化良好的特大断面轧辊。对石墨形态的观察和统计表明,石墨的球化率高且分布均匀时,可以提高轧辊的强度。例如,型钢轧辊平均球化率在89%时,其抗拉强度大于350MPa。     

铸造球铁轧辊中心双冷却的试验研究

本文介绍了球铁轧辊铸造时中心采用两种冷却介质双冷却的工装特点、轧辊断面的石墨和基体的变化特点及机械性能变化的规律。同时对改善特厚大断面的球铁铸件中心的球化和性能做了分析。     

提高石墨钢轧辊石墨等级工艺改进

石墨钢轧辊是在半钢轧辊材质的基础上通过控制石墨化元素和碳化物形成元素的含量及相应比例,在钢液中添加适量的孕育合金和球化剂进行孕育和球化,使轧辊在凝固过程中形成球状或团状石墨,组织中含有少量游离石墨。本文通过多年的生产实现和不断摸索,为如何提高石墨钢轧辊石墨球化等级和轧辊使用性能提供参考依据。     

CrMoVTi稀土镁球铁轧辊

为实现冶金部轧辊分区供应的规划、省冶金局于1979年6月给我厂下达了“钒钛铸铁轧辊”的科研压务。根据国内外轧辊生产“球铁化”、“合金化”的发展方向,我们研制成功了CrMoVTi稀土镁球铁轧辊。攀钢公司的VTi生铁不但是冶炼优质VTi低合金钢的极佳材料、也是机器制造业用于制造高质量耐磨铸铁的优质原生铁。因     

稀土镁铬钼球铁轧辊的研制

轧辊质量的好坏直接关系到轧板轧材的质量和产量。而球铁轧辊在轧辊中占着重要的比例,它与铸钢轧辊相比,具有较好的耐磨性、消振性和低的缺口敏感性;在采用合金化等条件下,可以获得良好的机械性能。中型以上的轧辊实际上是属于特大截面的铸件,而大多数辊子需开槽孔深50～150毫米;同时由于合金钢板材生产比例不断增大,故对球铁轧辊的质量提出更高的要求。因此如何获得球化良好,耐磨性高且磨损均匀,抗拉强度也好,是轧辊质量好坏的关键所在。过去生产球铁轧辊时主要用镁作球化剂,因而疏     

KWA1000轧辊磨床数控化改造

介绍了对KWA1000数控轧辊旧磨床进行的数控化设计及改造，通过改造达到了同类型轧辊数控磨床的精度要求。     

Rapid Bridge Replacement under Emergency Situation: Case Study

The terrorist attack on September 11, 2001, and subsequent potential threats to the United States transportation systems have presented an urgent need to elevate the security of the transportation infrastructure and to develop emergency response plans to quickly react to the possible consequences of an extreme event. Highway bridges, as critical components of the nation’s transportation network, have been brought to closer attention by government agencies. A research project was conducted to identify strategies and technologies to restore the use of a damaged bridge quickly. One of the tasks associated with the research was to perform several case studies of previous bridge replacements following extreme events. These events include explosion and fire caused by vehicle impact, vessel collision with a bridge, and damage caused by flood and earthquake. By studying the cases, the research team seeks to identify and expand on lessons learned and address which actions did and did not work well given the circumstances of the incident. These lessons have great value to the people who need to develop and implement an emergency response plan.     

NJTxtr—A Computer Program Based on LASER to Monitor Asphalt Segregation

Abstract: This paper describes the research funded by the New Jersey Department of Transportation to develop an automated technology to monitor segregation during construction of hot-mix asphalt concrete pavements. A Laser-based system was used to measure surface texture and to detect segregation. Two segregated test sections and a control test section were tested to evaluate the applicability of Laser texture method to detect and quantify segregation. Laser texture data were gathered from all three sections. Ratios of texture in segregated areas to that in nonsegregated areas were set as the basis for detection of different levels of segregation. By combining the level of segregation and extent of segregation, an AREA index was developed to determine the acceptability of a pavement section. Based on AREA index, pay adjustment factors were proposed to reduce the payment to account for loss of pavement life due to segregation. Further remedial actions were proposed to correct segregated pavement sections with acceptable AREA index. Based on the above concepts, Windows-based computer program NJTxtr was developed to detect and quantify segregation. This computer program uses the Laser-equipment-collected pavement texture data and determines whether the pavement section is acceptable or unacceptable based on the level of segregation within a pavement section, and provides bonus or penalties to the contractor. The paper describes a novel technology using laser and associated software for construction quality control of asphalt concrete pavements. The proposed methodology was applied to detect segregation in an interstate highway section in New Jersey, and this section was repaved based on visual observation and recommendation from this study.     

Probability of Project Completion Using Stochastic Project Scheduling Simulation

This paper introduces a software, Stochastic Project Scheduling Simulation (SPSS), developed to measure the probability to complete a project in a certain time specified by the user. To deliver a project by a completion date committed to in a contract, a number of activities need to be carried out. The time that an entire project takes to complete and the activities that determine total project duration are always questionable because of the randomness and stochastic nature of the activities’ durations. Predicting a project completion probability is valuable, particularly at the time of bidding. The SPSS finds the longest path in a network and runs the network a number of times specified by the user and calculates the stochastic probability to complete the project in the specified time. The SPSS can be used by a contractor: (1) to predict the probability to deliver the project in a given time frame and (2) to assess its capabilities to meet the contractual requirement before bidding. The SPSS can also be used by a construction owner to quantify and analyze the risks involved in the schedule. The benefits of the tool to researchers are: (1) to solve program evaluation and review technique problems; (2) to complement Monte Carlo simulation by applying the concept of project network modeling and scheduling with probabilistic and stochastic activities via a web based Java Simulation which is operateable over the Internet, and (3) to open a way to compare a project network having different distribution functions.     

Reconciliation of Owner and Contractor Views in Heavy Construction Projects

Delay and loss of productivity are the two main types of damage experienced by the contractor when the owner issues a change order. Courts have recognized critical path method schedule analysis as the preferred method of identifying and quantifying critical delays. As for the inefficiency damages, there is no direct way of measuring inefficiency due to its qualitative nature and the difficulty of linking the cause of the productivity loss to the damage. Most of the scholarly work published in this area was based on data supplied by the contractors; and that explains why there are discrepancies between what the contractor asks for and what the owner believes the contractor is entitled to. This study addresses the need for a statistical model to quantify the productivity loss from verifiable site data such as owner’s daily reports, change orders, drawings, and specifications, rather than rely solely on contractor surveys. A model is developed and validated to quantify the productivity loss in pipe work in roadway projects due to the change orders. The productivity loss study analyzed two sets of data that include: (1) variables that predict which of the two parties, the owner and the contractor, contributed to the productivity loss; and (2) variables that predict, from the legal viewpoint, productivity losses which only the owner is responsible for. The study showed the difference between what the contractor asked for and what he/she is actually entitled to. This model can be used by both the owner and the contractor to quantify the productivity loss due to change orders, and to offer an objective approach to reconcile their differences. This study concludes with an example to demonstrate the use of the model.     

Report of the Treasurer: 1980: Onward, financially and morally.

APA is in very good shape financially as a result of procedures and attitudes within the Council of Representatives and elsewhere in the Association's governance. We are able to maintain a balanced budget and to enjoy surpluses--though we can be certain that this will not continue forever--and at the same time to be reasonably solicitous of personal and social needs of the disadvantaged in our midst. At a time when the federal government finds it necessary to abandon or drastically cut programs to help the voiceless and other victims of our society, it is heartening to note that in our small way we psychologists are able to walk both sides of the street, that is, to help those who need our help, but to do so without imperiling our financial solvency. Despite spiraling inflation, the Association continues to produce a surplus from operations, as mandated by the Council of Representatives, while being responsive to the needs of the membership in a swiftly changing environment. In addition to the goal of building our reserves, we are dedicated to the continuation of all existing APA programs in our constant attempts to advance psychology as a science and profession and as a means of promoting human welfare. Financial statements for 1979-1981 are provided. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Compatibility with Jet A-1 of a GCL Subjected to Freeze–Thaw Cycles

Needle-punched geosynthetic clay liner (GCL) specimens subjected to 0, 5, and 12 freeze–thaw cycles in the laboratory, and GCL specimens recovered from a composite barrier wall in the Canadian Arctic after 1 and 3 years were examined to assess the hydraulic conductivity/permeability with respect to both deionized deaired water and Jet A-l. The GCL specimens recovered from the field after 3 years had a hydraulic conductivity with respect to water that was approximately 30% less than that of the GCL specimens subjected to 12 initial freeze–thaw cycles in the laboratory, suggesting that the laboratory conditions are more severe than field conditions. The combined effects of both the freeze–thaw cycles and Jet A-l permeation increased the permeability. This increase is attributed to the creation of macropores in the GCL due to freezing and to an expansion of free-pore space due to contraction of the double layer caused by permeation of Jet A-l. Although there was an increase in permeability due to the combined effect of freeze–thaw and permeation by Jet A-l, the effect was relatively small and the results suggest that the GCL continued to exhibit good performance as a hydraulic barrier when subject to extreme climatic conditions and hydrocarbons both in the laboratory and in the field.     

Large Membrane Roof Analysis: Nonlinear Modeling of Structures, Connectors, and Experimental Evidences

This work discusses the numerical and physical models developed for the design of a membrane roof for the Baptist Church of Fortaleza as well as the fabrication and construction of the actual membrane, comparing results of the models with those of the real structure. The roof area amounts to about 2,900?m2, a national record for flexible border membranes and, to the writers’ knowledge, the first case of a fully computer-assisted design process within Brazil. The paper initially outlines procedures to form finding, stress analysis, and patterning, and then focuses on the physical models developed to validate them. Finally, construction of the actual membrane is described, and comparison is made with the previous numerical and physical models. Determination of the mechanical properties of the fabrics used to construct the membrane is also briefly discussed. Additionally, analyses of the geometric configuration and definition of the structural response of typical connectors of such a tension structure, collecting and distributing stresses coming from sails and anchoring cables and elements acting to transfer loads to the foundations, are developed. Unilateral contact is considered to develop among the aforementioned connector and the cable/rings welded to the slabs and the redance, imposing localized directional variations to the cable; furthermore, geometric (large strains) and material nonlinearities are accounted for.     

Measuring Performance for Building Maintenance Providers

A building maintenance scheme was introduced in Hong Kong Housing Authority in January 2006 which employed contractors to provide inspection inside the public housing tenants’ units and arranged necessary repair works. This study aims to assess the contractor service quality performance. A method of assessment is devised based on the SERVQUAL approach to measure the public housing owner’s frontline representatives’ expectations and perceptions of the contractors’ performance. The outcome indicates that the deficiencies of service quality variables are related to the willingness of the contractors to provide prompt responses to requests from the tenants or the owner’s frontline representatives, and the availability of sufficient resources to perform the promised service dependably and accurately in terms of time, cost, and quality. The outcome of this study helps to identify the weaknesses of the contractors and allows them to properly allocate resources to those urgently needed variables. The implications from this study are considered and recommendations for industrial practices and further research are made.     

Effects of Surfactant Addition on Dewatering of Alum Sludges

In Taiwan, surfactants are frequently used in the flotation process to aid in solid/liquid separation. Their effect on the dewatering of alum sludge was investigated. Various amounts of cationic and anionic surfactants were added to sludge samples, and the dewatering characteristics of the sludge and the water content of sludge cakes were evaluated. Both surfactants improved the dewatering of the sludge by lowering the specific resistance to filtration, decreasing the bound water content, and increasing the dewatering rate of the sludge. Different combinations of anionic and cationic surfactants and polyelectrolytes were also experimented on to study the effect of surfactant addition on the dewatering characteristics of polyelectrolyte-conditioned sludge. Experimental results indicated that both cationic and anionic surfactants adversely affected the dewatering of the conditioned sludge. The addition of surfactant to the oppositely charged polyelectrolyte proved to be most detrimental to sludge dewatering due to the precipitation between surfactant and polyelectrolyte. The addition of cationic surfactant to the cationic polyelectrolyte-conditioned sludge had the least effect.