Impact of Overmanning on Mechanical and Sheet Metal Labor Productivity

This paper details the impacts of overmanning on labor productivity for labor-intensive trades, namely mechanical and sheet metal contractors. Overmanning, as used in the following research, is defined as an increase of the peak number of workers of the same trade over the actual average manpower used throughout the project. The paper begins by reviewing literature on the effects of overmanning on labor productivity. Via a survey to various contractors, data were collected from 54 mechanical and sheet metal projects located across the United States. Various statistical analysis techniques are then performed to determine quantitative relationship between overmanning and labor productivity. These techniques include the stepwise method, T-test, P-value tests, analysis of variance, and multiple regression analysis. The results indicate a 0–41% loss of productivity depending on the level of overmanning and the peak project manpower. Cross-validation is performed to validate the final model. Finally, a case study is provided to demonstrate the application of the model.     

Improving Employees’ Work-Life Balance in the Construction Industry: Project Alliance Case Study

Work-life conflict has a damaging effect on job satisfaction, organizational commitment, productivity turnover, and absenteeism. On an individual level, work-life conflict is associated with employee burnout, mental health issues, substance abuse, and diminished family functioning. Thus, work-life balance is an important issue to the construction industry, in terms of both organizational effectiveness and occupational health. Long and inflexible work hours are the most consistent predictor of work-life conflict among construction employees, particularly those working on-site or in a project office. There is considerable resistance to the adoption of new ways of scheduling work within the industry. This paper describes the post hoc evaluation of a compressed work week (reducing the length of the working week, but increasing the length of the working day) in a case study project alliance in Queensland, Australia. Quantitative and qualitative data are presented to demonstrate the beneficial impact of the initiative on employees’ work-life balance. The evaluation provides prima facie evidence that alternative work schedules can improve construction employees’ work-life balance, creating benefits for construction employees and organizations. The paper concludes that project alliances provide an ideal environment in which work-life balance initiatives can help to create high-performance work systems in the construction sector.     

Delay Time Analysis in Microtunneling Projects

Delay in microtunneling projects is a complex multivariate problem. Delay in microtunneling is defined as the nonworking time of a microtunneling project due to any reason other than scheduled stops. There are many reasons for delay such as mechanical failure of system components, leakage of hydraulic hoses, blockage of slurry pipes, and waiting time for excavated materials hauling equipment. Delay time increases the project duration and consequently the project cost. Delay data were collected from 35 microtunneling projects. Collected delay data were delay duration, delay reason, time, and location from the start to the stopping point. Five categories of delay causes were used in the analysis. Prediction of delay time will enhance the estimation accuracy of microtunneling project duration. A predictive model using a probabilistic approach was selected to represent the delay time. Based on data characteristics, a Weibull distribution was determined to best represent the overall delay duration in microtunneling projects. Using “regression with life data,” expected overall delay in a microtunneling project could be predicted as a function of driven length. The model will help contractors to estimate total project time with reasonable accuracy. Knowing the anticipated delay time will allow contractors to have a point of comparison for actual performance.     

Bioconversion of barley straw and corn stover to butanol (a biofuel) in integrated fermentation and simultaneous product recovery bioreactors

In these studies concentrated sugar solutions of barley straw and corn stover hydrolysates were fermented using Clostridium beijerinckii P260 with simultaneous product recovery and compared with the performance of a control glucose batch fermentation process. The control glucose batch fermentation resulted in the production of 23.25 g L⁻¹ ABE from 55.7 g L⁻¹ glucose solution resulting in an ABE productivity and yield of 0.33 g L⁻¹ h⁻¹ and 0.42, respectively. The control reactor (I) was started with 62.5 g L⁻¹ initial glucose and the culture left 6.8 g L⁻¹ unused sugar due to butanol toxicity resulting in incomplete sugar utilization. Barley straw (BS) hydrolysate sugars (90.3 g L⁻¹) resulted in the production of 47.20 g L⁻¹ ABE with a productivity of 0.60 g L⁻¹ h⁻¹ and a yield of 0.42. Fermentation of corn stover (CS) hydrolysate sugars (93.1 g L⁻¹) produced 50.14 g L⁻¹ ABE with a yield of 0.43 and a productivity of 0.70 g L⁻¹ h⁻¹. These productivities are 182–212% higher than the control run. The culture was able to use 99.4–100% sugars (CS & BS respectively) present in these hydrolysates and improve productivities which were possible due to simultaneous product removal. Use of >100 g L⁻¹ hydrolysate sugars was not considered as it would have been toxic to the culture in the integrated (simultaneous fermentation and recovery) process.     

就业中心与城市发展

理论和实证研究表明，工业的空间分布对城市经济与城市效率密切相关。就业与城市经济增长的关系表现在：（1）劳动生产率和要素的生产率一般与就业密度和城市规模成正比，这与大城市相对高的工资相一致；（2）工业行业的多样化也促进城市经济的发展；（3）工业就业集中有利于提高生产率，域市企业的数量，工业产量和专利的产生；（4）就业的空间集聚在很大程度上影响域市交通投资和成本。     

一种用于电镀成本核算及资源优化的计算方法

以几种常见的电镀线生产设备为例,介绍了一种可以广泛应用于PCB生产过程中水平及类水平设备的生产时间计算方法,以此精确计算出产品在生产过程中所消耗的设备折旧成本,为销售人员报价提供参考。推导出同时适用于不同生产批量大小的产能计算公式,为生产管理提供理论依据,以达到资源优化,提高设备利用率,降低成本的目的。     

Fast conching for milk chocolate

The objective of the study was to shorten the conventional conching process for milk chocolate, which still takes many hours, in order to increase productivity. Due to recent findings and to progress made in raw material treatment, a hypothesis was proposed: that flavour development in the conch could be less important for milk chocolate than it certainly is for dark chocolate. Other functions of conching, like water removal and fat covering of particles, could be achieved faster by using drier raw materials and by machines applying more shear force. For the experiments, a conventional process (taking 5 hours) was condensed into 30–90 minutes. In screening trials various flake pre-drying techniques were also tested. Samples produced were analysed for particle size and flow properties, as well as by a trained sensory panel. Results from the experimental design showed best results at 60–90 minutes conching time. Probably the procedures for flake pre-drying had little or no influence under the conditions used. Verification trials compared the fast conching procedure to the standard process using two different recipes. No relevant differences in physical or sensory properties were found between samples from standard and 90-minute-fast-conching, proving that under favourable conditions conching times for milk chocolates can be drastically reduced without negative impact on product properties and perception.     

Formalisms for query capture and data source identification to support data fusion for construction productivity monitoring

Productivity monitoring, which involves frequent monitoring and analysis of on-going construction activities, helps in assessing a project's performance and in enabling identification of opportunities for improvement. It often involves finding answers for dynamic user queries that require data to be fused from different combinations of heterogeneous data sources having different levels of detail, representations and reference systems. Digital elements of these sources are expanding exponentially, and yet fusing and processing them manually remains a challenging problem. In this paper, the authors present a formal approach for capturing dynamic user queries and identifying applicable sets of data sources from a given set of available data sources to answer such queries. This approach is an important step to enable automated and efficient multi-source data fusion.     

多层合采气井产能指示曲线异常的原因与校正方法

多层合采气井产能试井解释过程中,产能指示曲线容易出现异常情况,有可能导致气井的产能方程和无阻流量无法求取。为了弄清上述异常的产生原因,建立了考虑储层渗流和井筒变质量流耦合的全井段计算模型,用以计算多产层气藏的产气剖面和井筒压力分布;基于对不同产量条件下的气井产气剖面与井筒压力分布特征的分析,剖析了多层合采气井产能指示曲线出现异常的根本原因,提出了校正方法并进行了实例验证。研究结果表明:(1)造成多层合采气井产能指示曲线异常的原因一方面是多层段的井筒中为变质量管流,流压梯度随井深增加逐渐变小,采用压力计所处位置以上的流压梯度折算储层中部的流压高于实际值,另一方面是由于短时关井后多产层段的压力未达到平衡,使测得的静压高于长时间关井各层压力平衡后的静压;(2)多层合采气井产能试井解释的流压宜采用储层顶部以上200 m以内位置处压力计所测得的压力进行折算,并且需采用井筒压力平衡后的静压值;(3)算例和实例均验证了所建模型的可靠性、异常原因分析的合理性和校正方法的正确性。结论认为,该研究成果为多层合采气井的产能评价提供了技术支撑。