This paper considers the sequencing of products in mixed model assembly lines under Just-In-Time (JIT) systems. Under JIT systems, the most important goal for the sequencing problem is to keep a constant rate of usage every part used by the systems. The sequencing problem is solved using Genetic Algorithm Genetic Algorithm is a heuristic method which can provide a near optimal solution in real time. The performance of proposed technique is compared with existing heuristic methods in terms of solution quality. Various examples are presented and experimental results are reported to demonstrate the efficiency of the technique.

This paper considers the sequencing of products in car assembly lines under Just-In-Time systems. Under Just-In-Time systems, the most important goal for the sequencing problem is to keep a constant rate of usage every part used by the systems. In this paper, tabu search technique for this problem is proposed. Tabu search is a heuristic method which can provide a near optimal solution in real time. The performance of proposed technique is compared with existing heuristic methods in terms of solution quality and computation time. Various examples are presented and experimental results are reported to demonstrate the efficiency of the technique.

Mathematical models have been developed to evaluate methane emission from landfills. The Intergovernmental Panel on Climate Change (IPCC) and the US Environmental Protection Agency (USEPA) have provided first-order decay (FOD) models to estimate methane emission from landfills. The methane generation potential (L0) and the methane generation rate constant (k) are the two primary parameters in the FOD model. A major challenge in landfill gas modeling is estimating these parameters. The IPCC recommended that every country should develop country-specific emission factors appropriate for its circumstances and characteristics. The k value represents the rate constant associated with waste decomposition. In general, there are two different approaches for estimating a k value for a landfill. One uses actual field data in comparison with modeled data. However, this approach is limited by the spatial and temporal characteristics of landfill. Another approach is to collect samples of landfilled waste and then measure their biodegradability of waste as a function of waste age. As biodegradability is a surrogate for landfilling age, lower biodegradability would be expected in order samples. The objective of this study was to determine a k value using an anaerobic test (GB21). To achieve this objective, the GB21 which is used in Germany was conducted to estimate biodegradability of waste samples, and k value was determined based on FOD equation. Waste samples were collected at a landfill located in A City, Korea. The landfill is a valley-type landfill. It received municipal solid waste from 1990 to 2010. Food and paper wastes were the major fractions, constituting about 62.9% of the total amount disposed. However, the Ministry of Environment in Korea banned direct landfilling of food wastes in 2005, since then, food waste has no longer been disposed into landfills. In this study, the landfill site was separated into four areas based on landfilling age, and four samples were collected from each area. Cumulative biogas production for the waste excavated from the landfill varied from 6.9 to 35.8 Nl/kg-Dry Matter. Cumulative biogas production for landfilling age of 1 year was 35.8 Nl/kg-DM and it decreased to 6.9 Nl/kg-DM after 14 years. The k value obtained from this study was 0.156 yr-1 and was higher than the default k prescribed by the IPCC, which is 0.09 yr-1 in boreal and temperate climates. The higher k values obtained in this study can be explained by the high proportion of food waste disposed into the studied landfill. The default k values of rapidly degrading wastes including food waste and sludge are 0.185 yr-1. In addition a higher k value will result in predictions of more methane generation in the early years after waste burial, resulting in higher estimates of uncollected methane in greenhouse gas inventories. This work contributes to understanding decomposition rate of landfilled waste by examining biodegradability determination and providing k value for landfill.

Concrete with blast furnace slag (BFS) shows varied strength development properties different from normal concrete. Therefore, a precise prediction of compressive strength using a full maturity model is desired. The purpose of this study is to predict the compressive strength of concrete with BFS by calculating the apparent activation energy (Ea) and rate constant (kT) for each BFS replacement ratio. The method of Carino Model is used in this study for predicting compressive strength of concrete with BFS.

Concrete with blast furnace slag (BFS) shows varied strength development properties different from normal concrete. Therefore, a precise prediction of compressive strength using a full maturity model is desired. The purpose of this study is to predict the compressive strength of concrete with BFS by calculating the apparent activation energy (Ea) and rate constant (kT) for each BFS replacement ratio. The method of Carino Model is used in this study for predicting compressive strength of concrete with BFS.

In this study, the decomposition of gas-phase TCE, Benzene and Toluene, in air streams by direct UV Photolysis and UV/TiO2 process was studied. For direct UV Photolysis, by regressing with computer calculation to the experimental results the value of reaction rate constant k of TCE, Toluene and Benzene in this work were determined to be 0.00392s-1, 0.00230s-1 and 0.00126s-1, respectively. And the adsorption constant K of TCE, Toluene and Benzene in this work were determined to be 0.0519mol-1 ,0.0313mol-1 and 0.0084mol-1, respectively. For UV/TiO2 system by regressing with computer calculation to the experimental results the value of reaction rate constant k of TCE, Toluene, and Benzene in this work were determined to be 5.74g/ℓ․min, 3.85g/ℓ․min, and 1.18g/ℓ․min, respectively. And the catalyst adsorption constant K of TCE, Toluene, and Benzene in this work were determined to be 0.0005m3/mg, 0.0043m3/mg and 0.0048m3/mg, respectively.