Improving Cost Estimates of Construction Projects Using Phased Cost Factors

Central to cost-based competition is the capability to accurately predict the cost of delivering a project. Most literature on cost estimation focuses on specific estimation methods as generic techniques and little attention has been paid to the unique requirements at each project stage. This note attempts to identify the critical factors for effective estimation at various stages of typical construction projects. Drawing from organization control theory and cost estimating literature, this note develops a theoretical framework that identifies the critical factors for effective cost estimation during each project phase of a conventional construction project. The underlying logic is that as a cost estimating effort progresses, both task programmability and output measurability improve. As a result, control effort will shift from input-oriented control to a combination of output and behavior control.     

Contractor Prebid Planning Principles

Planning is an essential function of project management. Yet, many small- and medium-sized contractors do a relatively poor job of operational planning. Better prebid plans will reduce costs, shorten schedules, and improve labor productivity. Unfortunately, the published literature offers little guidance for smaller contractors on what constitutes effective planning. Most papers describe planning as a macrolevel process for owners. Most emphasize scope definition for industrial projects. This paper describes a microlevel planning process for contractors. It consists of eight steps which are: (1) assess contract risks; (2) develop a preliminary execution plan; (3) develop site layout plans; (4) identify the sequences that are essential-to-success; (5) develop detailed operational plans; (6) develop proactive strategies to assure construction input into design; (7) revise the preliminary plan; and (8) communicate and enforce the plan. The entire process is illustrated with a case study project and is fully illustrated with figures which show how to integrate the work of multiple contractors, keep key resources (crews or equipment) fully engaged with no downtime, provide time buffers so the work of follow on crews can be efficiently done, expedite the schedule using multiple work stations and concurrent work, ways to communicate the work plan to the superintendent and foremen, and how to assess the feasibility of various work methods. The steps are easy to understand and implement. They will yield immediate positive results.     

An analysis of contemporary printed wiring board manufacturing environment in the USA

This article presents a comparative analysis of contemporary printed wiring assembly (PWA) batch manufacturing systems employing surface mount technology (SMT), This analysis is accomplished by reviewing a typical case study of PWA manufacturing system in the USA. A previously developed model is then applied to the system to predict the cost and performance in the production of typical PWA designs. Various modifications to the system are then proposed and evaluated. From the case study, conclusions concerning optimum manufacturing system configuration for this industry can be drawn and are presented.     

职工持股计划在中国:理论上可行,实践上慎行

在对中美两国的职工持股计划进行分析后,本文认为职工持股计划在中国,理论上可行,但在实践中 需要谨慎行事。     

Evaluation of capital cost data. part 7: Liquid waste disposal with emphasis on physical treatment

Capital cost correlations are given for oil-water separators, equalization basins, primary clarifiers, clarifiers and clarifier mechanisms, reverse osmosis unit, ultrafiltration units, gravity filters and miroscreens. Data are included for raw sewage, intermediate and recirculation pumping stations and for preliminary treatment (or bar screens, grit removal, overflow and bypass chamber and Parshall flume), for grit removal, comminution and gas stripping. The correlations are accurate to ± 30%, expressed in Canadian dollars and adjusted to a Marshall and Swift value of 1000. Details as to what components are included in the cost are given. Data are given for the labour and material costs to create a working process module. For inflation indices, a critique of the Engineering News Record, EPA small city, Marshall and Swift, Chemical Engineering and Southam inflation indices suggested that the Marshall and Swift index is most appropriate for the construction and process equipment studied here. Concerning the currency exchange, for the equipment and processes in this study, equipment costs the same whether expressed directly in US or Canadian dollars. To put the current data into perspective, several hundred sources of cost data were analyzed. The major correlations are compared, on a consistent basis, with current data.     

方管两侧同时冲孔模设计

通过对零件的工艺分析，改进了工艺方案，用一副对冲孔模完成两边同时冲孔，降低了生产成本，提高了生产效率；并介绍了该对冲孔模具的结构特点、设计思路、应注意的问题和装配工艺性。     

Studies on the response of ‘Tifblue’ and ‘Woodard’ rabbiteye blueberries to fertilizers

A field study was conducted to investigate the effects of three fertilizer placement methods and 11 fertilizer formulations on plant survival, economics of replanting, yield, and fruit size of two rabbiteye blueberry (Vaccinium ashei Reade) cultivars Tifblue and Woodard. Fertilizer rates were either mixed with the soil under plants (before planting), sidedressed, or half-rate was placed under plants with the other half sidedressed. Fertilizers at planting caused a total of 34% Woodard and 12% Tifblue plants to die as compared to 6% for Woodard and none for Tifblue when no fertilizer was applied. Fertilizer formulas 2-1-1 and 5-10-10 oxide ratios placed under Woodard plants caused 100% mortality whereas Tifblue fertilized with oxide ratios 2-2-2 and 5-10-10 under plants reached the maximum 50% mortality. Splitting fertilizer placement under the side of the plants resulted in less Woodard plant mortality (30%) than placing all the fertilizer under plants (54%). However, plant mortality for the side/under group was not different than sidedressing all fertilizer (23%). A planted hectare in this experiment consisted of 1852 Tifblue and 926 Woodard plants, providing one Woodard plant to pollinate two Tifblue plants. Based on the results obtained, the 5-10-10 fertilizer placed under plants would be expected to cause half the Tifblue (926 plants) and all the Woodard (926 plants) to be replanted. Plant costs alone was estimated to be $2315 with additional replanting costs of $93 for Tifblue and much higher for Woodard. Sidedressing 5-10-10 fertilizer eight weeks after planting would have prevented plant mortality. Placement of various fertilizers under Woodard or Tifblue plants resulted in a significant increase in plant mortality as compared to side placement of fertilizers. Yield loss due to plant mortality increased linearly with the N level of the fertilizers (ranging from 0 to 2) for both cultivars. Woodard fruit size was not affected by fertilizer placement but placing fertilizers under Tifblue plants produced smaller yields with larger fruit than sidedressed plants. Blueberry plants in a virgin acidic soil may experience no reduction in yield if fertilization is completely eliminated.     

建设工程社会成本的分析与控制

随着各地工程项目的大规模建设,其不可避免地对社会、环境以及经济系统等产生影响,其中的负面影响则形成了建设工程的社会成本．基于此,首先介绍了建设工程社会成本的概念,然后分析了其构成,主要包括工程对资源环境、交通、社会、经济等方面影响而产生的社会成本．最后,站在工程建设的角度提出了控制社会成本的措施、建议,希望能促进工程领域社会成本观念的形成和发展,真正实现工程建设、资源环境和社会的可持续发展．     

SFT中的因素作用路径与作用历史

为了描述SFT中系统或元件在不同工作环境状态下经历变化的特征,提出了因素作用路径和作用历史的概念。作用路径描述系统或元件在不同工作状态变化过程中所经历状态的集合。作用历史描述经历作用路径过程中的可积累状态量。给出使用作用路径和作用历史分析问题的步骤。列举一例子,计算在设定条件下的元件维护成本。计算作用路径分别为AB和ACB两种,作用历史中使元件故障概率等于20%的维护成本,该维护成本是通过调整使用时间t和使用温度c产生的。最后给出以实例为背景的作用历史计算方法的不足、面临的问题和可能的解决方法。     

基于絮凝技术下的薯蓣皂苷分离研究

以超声波辅助十二烷基硫酸钠水溶液萃取得到的薯蓣皂苷萃取液为研究对象,以薯蓣皂苷分离因数为评价指标,系统研究了絮凝剂种类、絮凝剂加量、体系pH值、复配条件等对薯蓣皂苷分离因数的影响.发现在最佳絮凝条件下,薯蓣皂苷的分离因数94.5%,采用该技术薯蓣皂素的得率较真空浓缩法高0.062%,该技术为实现低成本下薯蓣皂素的清洁生产奠定了基础.