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
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.
文摘目的:探讨“冬病夏治”全方配伍和无白芥子配伍延胡索乙素在模型家兔“肺俞”穴皮下药代动力学特征及药代动力学-药效动力学(PK-PD)模型的相关性。方法:支气管哮喘模型家兔随机分成延胡索单方组、缺白芥子组、全方组,微透析技术收集14 h穴位皮下透析液,液相色谱-质谱法(Liquid Chromatography Mass Spectrometry,LCMS)法检测方中君药延胡索主要成分延胡索乙素浓度,获得药代动力学参数;酶联免疫吸附试验(ELISA)法检测对应时间点模型动物血清中IgE水平,获得药效学参数;对药动学、药效学参数进行PK-PD模型拟合。结果:白芥子配伍后的药峰浓度(C_(max))、药时曲线下面积(AUC_(0-t))、平均滞留时间(MRT_(0-t))均显著增加(P<0.01,P<0.01,P<0.05),达峰时间(T_(max))提前(P<0.01);“浓度-时间-效应”三维曲线表明,方中有白芥子配伍时,药效出现更快、消退更慢,起效时间晚于峰浓度,具有一定滞后性。结论:动力学参数、PK-PD模型结果表明,白芥子配伍能够改变“方中君药”——延胡索的主要成分延胡索乙素穴位局部的皮下分布,促进方中君药有效成分快速吸收,延长滞留时间,在方剂中起到主药、改善其他药物分布的“双重”作用。
