• 대한산업공학회지
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• 제33권3호
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• pp.373-380
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• 2007

In this paper, we consider a new lot-sizing and scheduling problem (LSSP) that minimizes the sum of production cost, setup cost and inventory cost. Setup carry-over and overlapping as well as demand splitting are considered. Also, maximum number of setups for each time period is not limited. For this LSSP, we have formulated a mixed integer programming (MIP) model, of which the size does not increase even if we divide a time period into a number of micro time periods. Also, we have developed an efficient heuristic algorithm by combining decomposition scheme with local search procedure. Test results show that the developed heuristic algorithm finds good quality (in practice, even better) feasible solutions using far less computation time compared with the CPLEX, a competitive MIP solver.

• Nuclear Engineering and Technology
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• 제39권1호
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• pp.85-94
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• 2007

The Korean nuclear fuel cycle was modeled by the dynamic analysis method, which was applied to the once-through and alternative fuel cycles. First, the once-through fuel cycle was analyzed based on the Korean nuclear power plant construction plan up to 2015 and a postulated nuclear demand growth rate of zero after 2015. Second, alternative fuel cycles including the direct use of spent pressurized water reactor fuel in Canada deuterium uranium reactors (DUPIC), a sodium-cooled fast reactor and an accelerator driven system were assessed and the results were compared with those of the once-through fuel cycle. The once-through fuel cycle calculation showed that the nuclear power demand would be 25 GWe and the amount of the spent fuel will be ${\sim}65000$ tons by 2100. The alternative fuel cycle analyses showed that the spent fuel inventory could be reduced by more than 30% and 90% through the DUPIC and fast reactor fuel cycles, respectively, when compared with the once-through fuel cycle. The results of this study indicate that both spent fuel and uranium resources can be effectively managed if alternative reactor systems are timely implemented along with the existing reactors.

• Nuclear Engineering and Technology
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• 제50권6호
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• pp.815-819
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• 2018

In this study, criticality safety assessments of the potential for storing transuranic element (TRU) ingots via a pyroprocess were evaluated to determine the appropriate TRU storage design parameters, in this case the ratio of the TRU ingot height to the radius and the number of TRU ingot canisters stacked within a container. Various accident situations were modeled over a modeling period of 5 years for a cumulative inventory of TRU ingots with various water densities in submerged containers and with various pitches between the containers in the facility. Under these combinations, we calculated the threshold of TRU height and radius ratio depending on the number of canisters in a container to keep the stored TRU in a subcritical state. The ratio of the TRU ingot height to radius should not exceed 4.5, 1.1, 0.5, 0.3, and 0.2 for two, three, four, five, and six levels of stacked canisters in a container, respectively.

• 한국지형학회지
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• 제23권2호
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• pp.109-125
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• 2016

This study aims to identify the landslide susceptible zones of Boeun area and provide reliable landslide susceptibility maps by applying different modeling methods. Aerial photographs and field survey on the Boeun area identified landslide inventory map that consists of 388 landslide locations. A total ofseven landslide causative factors (elevation, slope angle, slope aspect, geology, soil, forest and land-use) were extracted from the database and then converted into raster. Landslide causative factors were provided to investigate about the spatial relationship between each factor and landslide occurrence by using fuzzy set and logistic regression model. Fuzzy membership value and logistic regression coefficient were employed to determine each factor's rating for landslide susceptibility mapping. Then, the landslide susceptibility maps were compared and validated by cross validation technique. In the cross validation process, 50% of observed landslides were selected randomly by Excel and two success rate curves (SRC) were generated for each landslide susceptibility map. The result demonstrates the 84.34% and 83.29% accuracy ratio for logistic regression model and fuzzy set model respectively. It means that both models were very reliable and reasonable methods for landslide susceptibility analysis.

• Nuclear Engineering and Technology
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• 제39권4호
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• pp.327-336
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• 2007

The influence of density differences on the mixing of the primary loop inventory and the Emergency Core Cooling (ECC) water in the downcomer of a Pressurised Water Reactor (PWR) was analyzed at the ROssendorf COolant Mixing (ROCOM) test facility. ROCOM is a 1:5 scaled model of a German PWR, and has been designed for coolant mixing studies. It is equipped with advanced instrumentation, which delivers high-resolution information for temperature or boron concentration fields. This paper presents a ROCOM experiment in which water with higher density was injected into a cold leg of the reactor model. Wire-mesh sensors measuring the tracer concentration were installed in the cold leg and upper and lower part of the downcomer. The experiment was run with 5% of the design flow rate in one loop and 10% density difference between the ECC and loop water especially for the validation of the Computational Fluid Dynamics (CFD) software ANSYS CFX. A mesh with two million control volumes was used for the calculations. The effects of turbulence on the mean flow were modelled with a Reynolds stress turbulence model. The results of the experiment and of the numerical calculations show that mixing is dominated by buoyancy effects: At higher mass flow rates (close to nominal conditions) the injected slug propagates in the circumferential direction around the core barrel. Buoyancy effects reduce this circumferential propagation. Therefore, density effects play an important role during natural convection with ECC injection in PWRs. ANSYS CFX was able to predict the observed flow patterns and mixing phenomena quite well.

• 한국정보시스템학회지:정보시스템연구
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• 제30권2호
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• pp.105-126
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• 2021

Purpose The purpose of this study is to implement a optimal machine learning model about the cancellation prediction performance in car sales business. It is to apply the data set of accumulated contract, cancellation, and sales information in sales support system(SFA) which is commonly used for sales, customers and inventory management by imported car dealers, to several machine learning models and predict performance of cancellation. Design/methodology/approach This study extracts 29,073 contracts, cancellations, and sales data from 2015 to 2020 accumulated in the sales support system(SFA) for imported car dealers and uses the analysis program Python Jupiter notebook in order to perform data pre-processing, verification, and modeling that is applying and learning to Machine learning model after then the final result was predicted using new data. Findings This study confirmed that cancellation prediction is possible by applying car purchase contract information to machine learning models. It proved the possibility of developing and utilizing a generalized predictive model by using data of imported car sales system with machine learning technology. It can reduce and prevent the sales failure as caring the potential lost customer intensively and it lead to increase sales revenue by predicting the cancellation possibility of individual customers.

• The Journal of Asian Finance, Economics and Business
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• 제9권5호
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• pp.465-474
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• 2022

Using structural equation modeling, the study aims to investigate the causal relationship between working capital policies and working capital indicators on firm performance, including profitability and market value (SEM). The samples of 381 firms were selected from various industries listed on the Stock Exchange of Thailand (SET) from 2016 to 2020. The results showed that 1) there is an effect of working capital policies on profitability and market value; 2) there is an effect of working capital indicators on profitability and market value and 3) there is the effect of profitability on market value. From the results, it is suggested that conservative working capital investment policy (CIP) and conservative working capital financing policy (CFP) affect a company's performance in the Thailand context. In addition, shortening the cash conversion cycle (CCC) should be applied in management to increase profitability by reducing the receivables collection period (RCP) and inventory conversion period (ICP) while increasing the payables deferral period (PDP). The practical implications of the study provide the evidence that meeting the dues according to short CCC management can represent healthy liquidity in cash flow that helps gain investor confidence and the investment interest that further increases the market value.

• Geomechanics and Engineering
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• 제37권2호
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• pp.135-147
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• 2024

A GIS-based landslide susceptibility mapping (LSM) was carried out using frequency ratio (FR), modified frequency ratio (M-FR), analytic hierarchy process (AHP), and modified analytic hierarchy process (M-AHP) methods to identify and delineate the potential failure zones along the Halong - Vandon expressway. The thematic layers of various landslide causative factors were generated for modeling in GIS, including geology, rainfall, distance to fault, distance to road, slope, aspect, landuse, density of landslide, vertical relief, and horizontal relief. In addition, a landslide inventory along the road network was prepared using data provided by the management department during the course of construction and operation from 2017 to 2019, when many landslides were documented. The validation results showed that the M-FR method had the highest AUC value (AUC = 0.971), which was followed by the FR method with AUC = 0.961. The AUC values were 0.939 and 0.892 for the M-AHP and AHP methods, respectively. The generated LSM obtained from M-FR method classified the study area into five susceptibility classes: very low (0), low (0-1), moderate (1-2), high (2-3), and very high (3-4) classes, which could be useful for various stakeholders like planners, engineers, designers, and local public for future construction and maintenance in the study area.

• 한국토양비료학회지
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• 제43권2호
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• pp.237-241
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• 2010

전 세계적으로 지구온난화의 원인인 대기 중 온실가스 농도를 감축하는 여러 정책들이 모든 산업을 망라하여 추진되고 있다. 식량안보라는 특수성은 있지만, 농업도 예외는 아니다. 이런 취지에서 최근에 농산물의 전체 생산과정에서 발생하는 탄소배출량을 산정하고, 이를 토대로 탄소배출량이 적은 농산물 생산방식을 도입하고자 하는 요구가 증가하고 있다. LCA 도구를 농업분야의 환경평가에 적용한 해외 연구 사례들을 살펴보면, 스위스는 Ecoinvent가 주축이 되어 농작물, 농업기반시설, 농자재, 농기계 등 농축산 전반에 대한 LCI D/B를 구축하여 제공하고 있고, 우리와 농업시스템이 유사한 일본은 산업연관분석을 이용하여 농업을 위한 Top-down 방식의 LCA 수행 방법론을 개발하였으며, 이를 농작물 생산 방식에 따라 평가하고 농업분야에 대한 영향평가 방법론과 가중치를 개발하였다. 반면에 국내의 LCA를 통한 농업환경영향평가는 출발 단계에 있다. 따라서 농업환경에 있어 주요 인자인 비료 및 농약에 대한 환경영향을 평가하고 이를 위한 국내 비료와 농약의 흐름 모델링, 방법론 개발이 요구되며, 국내 농업 시스템을 반영한 기타 농자재, 농기계 및 농업기반시설에 대한 환경영향평가 역시 수행되어야 한다.

• 한국대기환경학회지
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• 제33권5호
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• pp.497-514
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• 2017

This study quantitatively analyzes the effects of emission inventory choices on the simulated particulate matter (PM) concentrations and the domestic/foreign contributions in the Seoul Metropolitan Area (SMA) with an air quality forecasting system. The forecasting system is composed of Weather Research and Forecasting (WRF)-Sparse Matrix Operator Kernel Emissions (SMOKE)-Community Multi-Scale Air Quality (CMAQ). Different domestic and foreign emission inventories were selectively adopted to set up four sets of emissions inputs for air quality simulations in this study. All modeling cases showed that model performance statistics satisfied the criteria levels (correlation coefficient >0.7, fractional error <50%) suggested by previous studies. Notwithstanding the apparently good model performance of total PM concentrations by all emission cases, annual average concentrations of simulated total PM concentrations varied up to $20{\mu}g/m^3$ (160%) depending on the combination of emission inventories. In detail, the difference in simulated annual average concentrations of the primary PM coarse (PMC) was up to $25.2{\mu}g/m^3$ (6.5 times) compared with other cases. Furthermore, model performance analyses on PM species showed that the difference in the simulated primary PMC led to gross model overestimation in general, which indicates that the primary PMC emissions need to be improved. The contribution analysis using model direct outputs indicated that the domestic contributions to the annual average PM concentrations in the SMA vary from 44% to 67%. To account for the uncertainty of the simulated concentration, the contribution correction factor method proposed by Bae et al. (2017) was applied, which resulted in converged contributions(from 48% to 57%). We believe this study shows that it is necessary to improve the simulated concentrations of PM components in order to enhance the accuracy of the forecasting model. It is deemed that these improvements will provide more accurate contribution results.