• Journal of Korea Society of Industrial Information Systems
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• v.20 no.5
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• pp.107-115
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• 2015

Residential building owners are turning toward renovating their existing buildings to improve old and inefficient HVAC systems. Due to the renovation, much of the added costs will inevitably be passed on to tenants by increasing rent rates. This increment often increases the vacancy rate in the buildings. To balance the interests of both owners and tenants, this paper suggested a method to determine an appropriate rental rate increment for the HVAC system renovation. A case study on residential buildings was conducted to determine a balanced point where the rental rate increment that offsets the amount tenants are willing to pay for the renovation. To calculate all costs incurred by the renovation, life-cycle cost analysis was carried out. Therefore, this paper ultimately provides a threshold value of rental rate increment such that building owners can make a reasonable decision on the HVAC system renovation.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.22 no.51
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• pp.151-161
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• 1999

For many decades, Deterministic DCF approach has been widely used to evaluate investment opportunities. Under new manufacturing conditions involving uncertainty and risk, the DCF approach is not appropriate. In DCF, Risk is incorporated in two ways: certainty equivalent method, risk adjusted discount rate. This paper proposes a determination method of the Risk Adjusted Discount Rate for economically decision making advanced manufacturing technologies. Conventional DCF techniques typically use discount rate which do not consider the difference in risk of differential investment options and periods. Due to their relative efficiency, advanced manufacturing technologies have different degree of risk. The risk differential of investments is included using $\beta$ coefficient of capital asset pricing model. The comparison between existing and proposed method investigated. The DCF model using proposed risk adjusted discount rate enable more reasonable evaluation of advanced manufacturing technologies.

• Journal of Environmental Science International
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• v.15 no.10
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• pp.975-982
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• 2006

This study has been conducted to optimum operating conditions for effective acid fermentation according to OLR(organic loading rate) in the mesophilic and thermophilic acid fermentation process. The results are summarized as follows. In order to obtain reasonable acid fermentation efficiency in performing acid fermentation of food wastes in thermophilic condition, organic loading rate was required below 20 gVS/L.d. As $SCOD_{Cr}/TKN,\;SCOD_{Cr}/T-P$ of thermophilic acid fermented food wastes In organic loading rate 20 gVS/L.d were 18.9, 73.4 respectively, it was possible to utilize as external carbon source for denitrification in sewage treatment plant after solid-liquid separation as well as co-digestion of fermented food wastes and sewage sludge.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.32 no.4
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• pp.63-71
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• 2009

The traditional portfolio optimization problem is to find an investment plan for securities with reasonable trade-off between the rate of return and the risk. The seminal work in this field is the mean-variance model by Markowitz, which is a quadratic programming problem. Since it is now computationally practical to solve the model, a number of alternative models to overcome this complexity have been proposed. In this paper, among the alternatives, we focus on the Mean Absolute Deviation (MAD) model. More specifically, we developed an algorithm to obtain an optimal portfolio from the MAD model. We showed mathematically that the algorithm can solve the problem to optimality. We tested it using the real data from the Korean Stock Market. The results coincide with our expectation that the method can solve a variety of problems in a reasonable computational time.

• IE interfaces
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• v.16 no.1
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• pp.111-116
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• 2003

Business integration has been considered as one of the most critical success factors that enable the firms to gain competitive edges. Despite this trend, it has also been found among not a few companies that the activities that should be functionally tied with are performed even independently. In this study, an integrated model of production planning and inventory has been developed. Computerization of the production planning activities is proposed and implemented. We also proposed the reasonable inventory levels of each item using historic data of the items, which are composed of safety stock from the given fill-rate, operating stock from the production patterns, and reserved stock from the production planning. This study has helped the firm to have clearer job definition of the related processes, to tightly control the inventory by setting and tracing the reasonable fill rates for every product, and to quickly respond to the market changes through the computerized production planning process.

• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.958-967
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• 2023

This work studies the defect features in a dilute FeMnNi alloy by an Object Kinetic Monte Carlo (OKMC) model based on the "grey-alloy" method. The dose rate effect is studied at 573 K in a wide range of dose rates from 10^-8 to 10^-4 displacement per atom (dpa)/s and demonstrates that the density of defect clusters rises while the average size of defect clusters decreases with increasing dose rate. However, the dose-rate effect decreases with increasing irradiation dose. The model considered two realistic mechanisms for producing <100>-type self-interstitial atom (SIA) loops and gave reasonable production ratios compared with experimental results. Our simulation shows that the proportion of <100>-type SIA loops could change obviously with the dose rate, influencing hardening prediction for various dose rates irradiation. We also investigated ways to compensate for the dose rate effect. The simulation results verified that about a 100 K temperature shift at a high dose rate of 1×10^-4 dpa/s could produce similar irradiation microstructures to a lower dose rate of 1×10^-7 dpa/s irradiation, including matrix defects and deduced solute migration events. The work brings new insight into the OKMC modeling and the dose rate effect of the Fe-based alloys.

• Journal of the Korean Geotechnical Society
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• v.15 no.6
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• pp.17-28
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• 1999

In order to analyze effects of strain rate on consolidation of natural clay, this paper presents a nonlinear elasto viscoplastic model in which viscoplastic behavior is modeled by a unique effective stress-strain-strain rate relationship (equation omitted). The predicted values using numerical analysis are compared with measured ones in several laboratory tests such as creep test, multistage load test, and relaxation test for Berthierville clay. It is possible to estimate consolidation behavior of natural clay with reasonable accuracy using the proposed nonlinear viscoplastic model.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.1
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• pp.69-76
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• 1997

This paper deals with the machinability based on turning and drilling tests. The main conclusions obtained were as follows. (1) Turning : The roughness of Machined surface decreases with the increase of the rake angle of tools, and the tool wear becomes smaller with the decrease of the rake angle. When the feed rate becomes larger, the fracture of work material in the vicinity of the cutting edge occurs on a larger scale, eventually decreasing tool wear. (2) Drilling : Considering both tool life and productivity, it is reasonable to cut with the high cutting speed and feed rate. The tool wear increases with the increase of feed rate, and the tendency of feed rate on tool wear becomes stronger at the cutting speed $\geq$30m/min.

• Journal of the Korean Society of Combustion
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• v.16 no.1
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• pp.46-51
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• 2011

Exhaust gas of an industrial furnace used at such as metallurgy or ceramic manufacturing usually contains thermal energy with high temperature which can be recycled by heat exchanger. However, when the temperature of the exhaust gas is high such as more than $1,000^{\circ}C$, ordinary metallic heat exchanger cannot fully recover the heat due to the limitation of operating temperature depending on the material property. In the present study, a compact ceramic heat exchanger of cross flow type is introduced and evaluated by heat exchange rate and operating temperature. The ceramic heat exchanger can endure the gas temperature more than $1,300^{\circ}C$, and its volumetric heat exchanging rate exceeds 1 MW/$m^3$. The experimental data is also compared with the previous numerical result which shows reasonable agreement. Meanwhile, the gas leakage rate is measured to be about 3~4%, and heat loss to environmental air is about 23~26% of the fuel energy.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.2
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• pp.67-69
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• 2006

A load composition rate estimation algorithm is developed for DSM evaluation system. The algorithm has the structure which is composed of data verification and development and can enhance the data quality Also a hourly weighting function is introduced for maintaining load shapes. The load composition rates of specific industrial customers are obtained and the results of case studies show that a reasonable load composition rate is achieved. Additionally qualify function deployment (QFD) is introduced to enhance quality and reliability of data.