• 태양에너지
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• 제19권3호
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• pp.63-73
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• 1999

Ice storage systems are used to shift the peak load in day time into night time in summer. This paper describes a system simulation of partial ice storage system composed of an encapsulated ice storage tank, a screw compressor chiller, a heat exchanger, and a brine pump. For the system simulation, a one-dimensional model of ice storage tank is developed and validated by comparison with the performance data from measurements of an ice storage tank installed at a building. The control strategies considered in this study are chiller priority and storage priority being used commercially. The system is simulated with design cooling load of 600 RT peak load in design day and with off-design day cooling load, and the electric energy costs of the two control strategies for the same system size are compared. As a result of calculation, the energy consumption in a week for storage priority is higher than that for chiller priority control. However due to lower cost of night electric charge rate, energy cost for storage priority control is lower than chiller priority.

• Industrial Engineering and Management Systems
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• 제13권2호
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• pp.231-249
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• 2014

This paper discusses a green supply chain with a manufacturer and a collection trader, and it proposes an optimal production planning for remanufacturing of parts in used products with quality classification errors made by the collection trader. When a manufacturer accepts an order for parts from a retailer and procures used products from a collection trader, the collection trader might have some quality classification errors due to the lack of equipment or expert knowledge regarding quality classification. After procurement of used products, the manufacturer inspects if there are any classification errors. If errors are detected, the manufacturer reclassifies the misclassified (overestimated) used products at a cost. Accordingly, the manufacturer decides to remanufacture from the higher-quality used products based on a remanufacturing ratio or produce parts from new materials. This paper develops a mathematical model to find how quality classification errors affect the optimal decisions for a lower limit of procurement quality of used products and a remanufacturing ratio under the lower limit and the expected profit of the manufacturer. Numerical analysis investigates how quality of used products, the reclassification cost and the remanufacturing cost of used products affect the optimal production planning and the expected profit of a manufacturer.

• 응용통계연구
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• 제27권2호
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• pp.211-226
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• 2014

국민연금 노령연금 수급자를 대상으로 소득계층별 차별 사망력과 기대여명을 산출하고, 그 결과를 반영하여 노령 연금 수급자의 수급부담구조를 분석하였다. 분석을 위해 노령연금 수급자의 소득계층에 대한 구분은 생애평균소득을 기준으로 3분위로 세분화하였으며, 사망확률 추정을 위해서 사용된 함수는 고연령 사망확률 추정에 주로 사용되는 gompertz모형을 사용하였다. 산출된 기대여명을 이용하여 소득계층별로 생애 총 연금급여액 규모를 추정함으로서 수익비, 내부수익률 및 후세대 부담전가량 분석의 정확성을 높이는데 기여하였다. 기대여명 추정 결과 60세 남자의 기대여명은 약 23.10년이며, 소득계층별로는 21.69~24.63년의 차이를 보이고 있다. 60세 여자의 기대여명은 약 28.84년이며, 소득계층별로는 27.63~29.81년의 차이를 보이고 있다. 즉 하위소득계층의 기대여명의 경우 소득계층을 통합한 경우의 기대여명보다 1.21~1.41년 낮게 추정되었으며, 상위 소득계층의 경우에는 0.97~1.53년 높게 추정되었다. 산출된 기대여명을 사용하여 수익비를 분석한 결과 하위 소득계층의 경우 약 2.68~4.83% 낮게 분석되었으며 상위 소득계층의 경우에는 2.07~4.98% 높게 분석되었다. 내부수익률은 하위 소득계층의 경우 약 0.00~0.74% 낮고 상위 소득계층의 경우에는 0.03~1.73% 높게 분석되었으며, 후세대 부담전가량은 하위 소득계층의 경우 약 3.00~5.74% 낮고 상위 소득계층의 경우에는 2.53~9.68% 높게 분석되었다. 분석 결과는 노령연금 수급자에 대한 소득계층별 기대여명 추정을 통해 나타난 수급부담구조 분석의 결과로서, 기존의 소득계층별 기대여명을 고려하지 않은 시뮬레이션 분석과는 차별성이 있으며, 소득재분배 효과가 있는 국민연금 노령연금 수급자의 수급 부담구조분석 결과에 대한 대표성을 지닌다.

• Fisheries and Aquatic Sciences
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• 제1권2호
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• pp.255-259
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• 1998

This study was designed to evaluate the economic analysis of channel catfish production in 1998 based on fish value and total feed cost. Catfish received higher protein feeds with lesser amount based on the dietary protein levels, but received the constant total protein input for all treatments. Weight gain per pond for treatment 1 $(28\%\;protein,\;100\%\;of\;satiation)$ was higher (P<0.10) than for treatment 3 $(36\%\;protein,\;77.8\%\;of\;satiation)$, but not significantly higher than for treatment 2 $(32\%\;protein,\;87.5\%\;of\;satiation)$ at constant DE. At constant DE/P (treatments 4, 2 and 5), weight gain per pond for treatment 5 $(36\%\;protein,\;77.8\%\;of\;satiation)$ was lower (P<0.10) than for treatment 2, but not significantly lower than for treatment 4 $(28\%\;protein,\;100\%\;of\;satiation)$. At constant DE, feed conversion slightly improved as dietary protein level increased from $28\%\;to\;32\%$ and feed allowance decreased by $12.5\%$, but did not improve further as dietary protein level increased from $28\%\;to\;36\%$ and feed allowance decreased by $22.2\%$. At constant DE/P, feed conversion improved as dietary protein level increased from $28\%\;to\;32\%$ increased and feed allowance decreased by $12.5\%$, but did not improve as dietary protein level increased from $28\%\;to\;36\%$ and feed allowance decreased by $22.2\%$ Total feed cost for treatment 1 was slightly, but not significantly higher than for treatments 2 and 3 at constant DE. At constant DE/P, total feed cost for treatment 5 was higher (P<0.05) than for treatment 2, but not significantly higher than for treatment 4. Total value of fish ($ /ha) produced for treatment 1 was highest and lowest was for treatment 5. Return above feed cost was highest for treatment 1 and nearly the same as treatment 2. Return over feed cost for treatments 3 and 4 were slightly lower than for treatments 1 and 2. Economic analysis showed that feeding fish the diet containing $28\%$ protein and 3.08 kcal/g DE to satiation and the diet containing $32\%$ protein and 3.08 kcal/g DE to $87.5\%$ of satiation produced the highest profit to farmer.

• Journal of Power Electronics
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• 제6권4호
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• pp.298-306
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• 2006

A high efficiency and low cost sustain driver for a plasma display panel (PDP) utilizing a current pumping method is proposed. The main concept of the proposed circuit is using the current source to charge and discharge the panel. As a result, all power switches can achieve zero voltage switching (ZVS) and every auxiliary switch can also achieve zero current switching (ZCS). Since the inductor current can compensate for the discharge current, the current stress of all the power switches can be reduced considerably. Furthermore, it has features such as a simpler structure, less mass, lower cost, and lower electromagnetic interference than in previous circuits.

• Asian-Australasian Journal of Animal Sciences
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• 제20권11호
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• pp.1777-1782
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• 2007

Beef producers are trying to produce not only better quality but also greater quantity of beef in order to meet the preferences of some consumers at a lower cost. This can be accomplished if we understand the factors regulating lipid deposition in intramuscular adipose tissue and the tenderness of meat. Propylene glycol (PG) might be used as a precursor of intramuscular fat synthesis especially in the late period of fattening because adipose tissue in ruminants is thought to mature sequentially in abdominal, intermuscular, subcutaneous and intramuscular depots. The action of cholecalciferol supplementation has been verified in producing more tender meat through the enhancement of calpain activity over the postmortem ageing period. A synergistic effect can be expected if the dietary cation and anion difference (DCAD) technique is used in combination with dietary supplementation of cholecalciferol. In another approach, the optimization of hormonal implant use also may provide similarly marbled beef at a much lower cost.

• East Asian Economic Review
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• 제21권2호
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• pp.167-197
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• 2017

I build a small open economy (SOE) dynamic stochastic general equilibrium (DSGE) model to investigate the effect of a heterogeneous wage contract between regular and temporary workers on a macroeconomic volatility in a financially fragile economy. The imperfect financial market condition is captured by a quadratic financial adjustment cost for borrowing foreign assets, and the labor market friction is captured by a Nash bargaining process which is only available to the regular workers when they negotiate their wages with the firms while the temporary workers are given their wage which simply equals the marginal cost. As a result of impulse responsesto a domestic productivity shock, the higher elasticity of substitution between two types of workers and the lower weight on the regular workers in the firm's production process induce the higher volatilities in most variables. This is reasoned that the higher substitutability creates more volatile wage determination process while the lower share of the regular workers weakens their Nash bargaining power in the contract process.

• 한국경영과학회지
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• 제36권2호
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• pp.1-14
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• 2011

In this paper, we deal with an access network design problem of fiber-to-the-home passive optical network (FTTH-PON). The FTTH-PON network design problem seeks to minimize the total cost of optical splitters and cables that provide optical connectivity between central office and subscribers. We develop a flow-based mixed integer programming (MIP) model with nonlinear link cost. By developing valid inequalities and preprocessing rules, we enhance the strength of the proposed MIP model in generating tight lower bounds for the problem. We develop an effective Tabu Search (TS) heuristic algorithm that provides good quality feasible solutions to the problem. Computational results demonstrate that the valid inequalities and preprocessing rules are effective for improving the LP-relaxation lower bound and TS algorithm finds good quality solutions within reasonable time bounds.

• Design & Manufacturing
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• 제7권1호
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• pp.40-44
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• 2013

My company develops, manufactures injection mold and produces thin-walled cosmetics and food containers. Without high quality and low production cost, it is hard to compete in the market. To be competitive, a company has to utilize mold with as many cavities as possible to lower manufacturing cost. Eject plate abrasion and deformation cut down mold lifespan, troubles during injection lower productivity and foreign substances in molds cause abrasion. This study focuses on how to improve mold life and productivity, and to slow down mold abrasion.

• Journal of Information Display
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• 제7권4호
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• pp.24-26
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• 2006

We have developed a new driving method named TROPHY(Talented Role-playing Technology with Dual Polarity sustainer in Hybrid Mono board). In this method, the sustain voltage is partially compared to the conventional method and the number of power sources is reduced by voltage level unification during the reset, address and sustain period. The hybrid mono board was especially developed to implement those technologies. Through this, we can lower the cost with the TROPHY compared to the conventional one. It is a suitable technology to improve the reliability of circuit and image sticking problem. We can also reduce the number of driving boards and the EMI problem compared with those of the conventional method.