Optimization Model for Earth-Rock Allocation System in Large-Scale Hydraulic Engineering and Application in Shuibuya Project
Much importance is attached to the earth-rock allocation problem in the construction of many large-scale hydraulic engineering. Based on systemic view, the paper analyses the composition of the system and mutual relations among the elements. According to the analysis work, a linear programming model is constituted to optimize the operation of earth-rock allocation system to minimize the cost of the system. And the optimization model is put into operation in Shuibuya project in China. The calculating results by the model are economical and feasible in project construction
Further development of integer programming in earthwork optimization
The objective of existing linear programming methods of earthwork-system optimization in road construction has been either minimizing the cost or maximizing profit, generally without considering the project duration. This paper develops a linear programming model incorporating the project duration. The model attempts to optimize a comprehensive earthmoving system in road construction by comparing alternative fleets (from available fleets) to provide an optimum material distribution and appropriate plant fleets to complete a project within the specified time. The situations where different degrees of compaction, availability of various soil strata at cut sections and borrow pits, and selection of borrow/disposal sites are also incorporated. Among the possible extensions, equipment sharing between fleets and sequence of operations present at cut and fill sections are examined. The validity of the model is demonstrated by applying it to a numerical example, providing additional tools to the management such as the minimum project-completion time, the cheapest project cost and corresponding duration achievable with available resources.
Pharmacokinetics of Mivacurium Isomers and Their Metabolites in Healthy Volunteers after Intravenous Bolus Administration
Background Previous studies report the pharmacokinetics of mivacurium isomers after an infusion using venous blood sampling. Although the extent of the mivacurium arterial‐venous gradient is not known, the sampling site is likely to influence mivacurium pharmacokinetic parameters because the drug is rapidly metabolized as it traverses the circulation. The objectives of this study were (1) to determine the pharmacokinetics of mivacurium isomers in healthy persons after intravenous bolus administration using intensive arterial blood sampling, and (2) to characterize the formation and elimination of mivacurium metabolites in human plasma. Methods Eight persons classified as American Society of Anesthesiologists physical status 1 or 2 who were scheduled to undergo elective surgery under balanced anesthesia received 0.15 mg/kg mivacurium chloride as an intravenous bolus. Arterial blood samples were collected every 10 s during the first 2 min and at frequent intervals for 4 h thereafter. Plasma concentrations of mivacurium isomers and their metabolites were determined by two stereoselective high‐performance liquid chromatographic methods coupled with fluorometric detection and noncompartmental pharmacokinetic parameters. Results Mean elimination half‐lives of the trans‐trans, cis‐trans, and cis‐cis isomers were 2.4, 2, and 28.5 min, respectively, with corresponding mean plasma clearances of 29.2, 45.7, and 6.7 ml [center dot] min‐1 [center dot] kg‐1. The volumes of distribution at steady state of the trans‐trans, cis‐trans, and cis‐cis isomers were 0.047, 0.054, and 0.189 l/kg, respectively. Plasma concentrations of monoester and alcohol metabolites peaked 25 s (median) after mivacurium injection, with half‐lives in the range of 90 min, except for the cis alcohol metabolite, which was only negligibly and transiently formed. Conclusions Substantial hydrolysis of mivacurium isomers by cholinesterases was confirmed by the rapid appearance of mivacurium metabolites in plasma. The intensive arterial sampling proved to be critical for the trans‐trans and cis‐trans isomers because the area under the curve between 0 and 2 min accounted for 75% and 86% of the total, respectively.