The literature mentions multiple factors that can affect the accuracy of estimating the project duration in highway construction,such as weather,location,and soil conditions.However,there are other factors that have n...The literature mentions multiple factors that can affect the accuracy of estimating the project duration in highway construction,such as weather,location,and soil conditions.However,there are other factors that have not been explored,yet they can have significant impact on the accuracy of the project time estimate.Recently,TxDOT raised a concern regarding the importance of the proper estimating of the lead/lag times in project schedules.These lead/lag times are often determined based on the engineer’s experience.However,inaccurate estimates of the lead/lag time can result in unrealistic project durations.In order to investigate this claim,the study utilizes four time sensitivity measures(TSM),namely the Criticality Index(CI),Significance Index(SI),Cruciality Index(CRI),and the Schedule Sensitivity Index(SSI)to statistically analyze and draw conclusions regarding the impact of the lead/lag time estimates on the total duration in highway projects.An Excel-based scheduling software was developed with Monte Carlo simulation capabilities to calculate these TSM.The results from this paper show that the variability of some lead/lag times can significantly impact the accuracy of the estimated total project duration.It was concluded that the current practices used for estimating the lead/lag times are insufficient.As such,it is recommended to utilize more robust methods,such as the time sensitivity measures,to accurately estimate the lead/lad times in the projects scheduled.展开更多
The study was carried out in a lead company inside Alexandria which exists in a residential area. Different sites have been selected inside the Department of Lead Improvement to measure TSP, PM10, and heavy lead durin...The study was carried out in a lead company inside Alexandria which exists in a residential area. Different sites have been selected inside the Department of Lead Improvement to measure TSP, PM10, and heavy lead during the melting process which takes place inside big alloying kettles and from the stack emissions. After that, the company made evaluation of the old factory and decision makers decided to make development for this factory through buying a complete unit for treatment with a special filter to make abatement for the level of emission especially for lead. The aim of this work is: 1) Put a plan for monitoring the level of different pollution after modification and to calculate the percentage of decrease (efficiency) of the new control unit through concentration of TSP, PM10, and lead through different processes;2) Install a new filter to abate the different air pollutants such as TSP, PM10, and lead. Total Suspended Particulate (TSP) and Respiratory dust (PM10) measured by using Volume sampler and Air mitrix. Lead was measured by the digestion of the samples with a mixture of hydrochloric and nitric acids and using Atomic Absorption Spectropho- tometer. Results of measuring TSP, PM10, Lead in working environment, and lead inside stack before and after installation of the new filter showed percentage of decrease from 22% to 120%, 33% to 160%, 26% to 102%, and 51% to 56.5% respectively.展开更多
文摘The literature mentions multiple factors that can affect the accuracy of estimating the project duration in highway construction,such as weather,location,and soil conditions.However,there are other factors that have not been explored,yet they can have significant impact on the accuracy of the project time estimate.Recently,TxDOT raised a concern regarding the importance of the proper estimating of the lead/lag times in project schedules.These lead/lag times are often determined based on the engineer’s experience.However,inaccurate estimates of the lead/lag time can result in unrealistic project durations.In order to investigate this claim,the study utilizes four time sensitivity measures(TSM),namely the Criticality Index(CI),Significance Index(SI),Cruciality Index(CRI),and the Schedule Sensitivity Index(SSI)to statistically analyze and draw conclusions regarding the impact of the lead/lag time estimates on the total duration in highway projects.An Excel-based scheduling software was developed with Monte Carlo simulation capabilities to calculate these TSM.The results from this paper show that the variability of some lead/lag times can significantly impact the accuracy of the estimated total project duration.It was concluded that the current practices used for estimating the lead/lag times are insufficient.As such,it is recommended to utilize more robust methods,such as the time sensitivity measures,to accurately estimate the lead/lad times in the projects scheduled.
文摘The study was carried out in a lead company inside Alexandria which exists in a residential area. Different sites have been selected inside the Department of Lead Improvement to measure TSP, PM10, and heavy lead during the melting process which takes place inside big alloying kettles and from the stack emissions. After that, the company made evaluation of the old factory and decision makers decided to make development for this factory through buying a complete unit for treatment with a special filter to make abatement for the level of emission especially for lead. The aim of this work is: 1) Put a plan for monitoring the level of different pollution after modification and to calculate the percentage of decrease (efficiency) of the new control unit through concentration of TSP, PM10, and lead through different processes;2) Install a new filter to abate the different air pollutants such as TSP, PM10, and lead. Total Suspended Particulate (TSP) and Respiratory dust (PM10) measured by using Volume sampler and Air mitrix. Lead was measured by the digestion of the samples with a mixture of hydrochloric and nitric acids and using Atomic Absorption Spectropho- tometer. Results of measuring TSP, PM10, Lead in working environment, and lead inside stack before and after installation of the new filter showed percentage of decrease from 22% to 120%, 33% to 160%, 26% to 102%, and 51% to 56.5% respectively.
