Detection of schedule delay risk of empirical construction projects

In Ethiopian construction projects, schedule delay risk is a predominant issue because it is not properly addressed. Although several studies have been focused on the various effects of risk in construction projects, limited efforts have been made to investigate the typical and the overall schedule delay risk. In this study, our aim is to detect the typical and overall schedule delay risk throughout the construction project lifecycle, which consists of the pre-construction, construction, and post-construction stages, and compare the stages with each other. Common criteria, sub-criteria, and attributes were developed for all alternatives for the purpose of making a risk decision. The methodology that was followed integrated the multiplecriteria decision-making(MCDM) model of fuzzy analytic hierarchy process comprehensive evaluation(FAHPCE)and the relative important index(RII). Data were collected from 77 participants, who were selected through purposive sampling from different contracting organizations in Ethiopian construction projects by means of questionnaires that were distributed to experienced experts. The findings showed that there is a typical delay risk either in the type or in the level of the different construction activities.Consequently, the most influenced alternative is the construction stage because of the high-risk responsibility,resource, and contract condition related criteria. The postconstruction stage was the second most influenced stage because of the high-risk responsibility-related criteria. The pre-constructed stage was the least influenced stage that consist high-risk criteria of responsibility, resource, and contract condition related. These differences provided noteworthy information about risk mitigation in construction projects by identifying the exact risk level on specific activity to make appropriate decision.

Controlling the Risk of Construction Delay in the Middle East： State-of-the-Art Review

The financial crisis in late 2008 arrested economic development in the construction sector in the Middle East, with the result that investors＇ confidence in the sector is severely depressed. Delays constitute one of the highest impediments to project success. In this respect, the traditional management is no longer sufficient for construction project success. The objective of this study is to conduct a literature review to identify additional effective measures for controlling the potential delays risks in construction projects in order to maximize the opportunities for success in those projects. Thirty-six scholarly articles published between 2000 and 2011 are reviewed to identify related MDRC （measures for delays risks control）. This survey reveals that 60% of the studies are related to decision-making, performance, risk management variations and poor management knowledge of stakeholders and that 20% of these studies are undertaken in the Middle East. A further 25% of the studies are related to the lack of financial risk by stakeholders, and of these 14% are in the Middle East. A knowledge gap is identified in terms of project performance, stakeholder management and risk management, which are seen as significant measures of success in controlling project delay.

A Class of Delayed Renewal Risk Processes with a Threshold Dividend Strategy

This paper considers a class of delayed renewal risk processes with a threshold dividend strategy. The main result is an expression of the Gerber-Shiu expected discounted penalty function in the delayed renewal risk model in terms of the corresponding Cerber-Shiu function in the ordinary renewal model. Subsequently, this relationship is considered in more detail in both the stationary renewal risk model and the ruin probability.

Extension of Some Classical Results on Ruin Probability to Delayed Renewal Model

Embrechts and Veraverbeke investigated the renewal risk model and gave a tail equivalence relationship of the ruin probabilities (?)(x) under the assumption that the claim size is heavy-tailed, which is regarded as a classical result in the context of extremal value theory. In this note we extend this result to the delayed renewal risk model.

Method to assess component contribution to toxicity of complex mixtures： Assessment of puberty acquisition in rats exposed to disinfection byproducts

A method based on regression modeling was developed to discern the contribution of component chemicals to the toxicity of highly complex, environmentally realistic mixtures of disinfection byproducts（DBPs）. Chemical disinfection of drinking water forms DBP mixtures.Because of concerns about possible reproductive and developmental toxicity, a whole mixture（WM） of DBPs produced by chlorination of a water concentrate was administered as drinking water to Sprague–Dawley（S–D） rats in a multigenerational study. Age of puberty acquisition,i.e., preputial separation（PPS） and vaginal opening（VO）, was examined in male and female offspring, respectively. When compared to controls, a slight, but statistically significant delay in puberty acquisition was observed in females but not in males. WM-induced differences in the age at puberty acquisition were compared to those reported in S–D rats administered either a defined mixture（DM） of nine regulated DBPs or individual DBPs. Regression models were developed using individual animal data on age at PPS or VO from the DM study. Puberty acquisition data reported in the WM and individual DBP studies were then compared with the DM models. The delay in puberty acquisition observed in the WM-treated female rats could not be distinguished from delays predicted by the DM regression model, suggesting that the nine regulated DBPs in the DM might account for much of the delay observed in the WM. This method is applicable to mixtures of other types of chemicals and other endpoints.