• 한국도서관정보학회지
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• 제37권4호
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• pp.3-20
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• 2006

현하 한국대학생들의 독서율이 점차 저하되고 있다. 독서부진의 제반 요인을 여러 부분에서 진단, 고찰하고, 독서저해요인을 추출함으로써 독서생활을 조장하고 독서율을 향상시키는 방안을 강구하고자 한다. 특히 본 연구에서는 대학생들의 독서철학 확립을 위한 논의를 정리하고, 또한 대학생 독서부진 해결을 위한 교육제도적 방안으로서 독서학점부과제도 또는 독서인증제도의 필요성을 강조하고자 한다.

• 대한기계학회논문집B
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• 제26권5호
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• pp.733-741
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• 2002

If a part of the poor solution from the absorber outlet is recirculated to the absorber inlet, the solution temperature at the solution spray pump can be reduced, and the solution flow rate in the absorber is increased. We have performed the experiments on the influences of the absorption chiller performance according to the ratio of the recirculation, defined as the ratio of the recirculation flow rate to the total solution flow rate at the absorber outlet. As increasing the ratio of the recirculation, the absorption capacity of the solution can be deteriorated. On the other hand, due to the increasing flow rate, the heat transfer rate can be enhanced. As a result, the performance of the absorber and the cooling capacity of the absorption chiller have nothing to do with the recirculation ratio, and the lifetime of the spray pump will be maintained.

• 한국염색가공학회지
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• 제12권1호
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• pp.12-16
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• 2000

Silk and cotton fabrics were dyed with Parmelia tinctorium that is a kind of lichen. Dyeing solution was prepared by fermentation in aqueous ammonia solution. The effects of pH and temperature in dyebath on dyeability were investigated. The maximum K/S value of each dyed fabrics was showed in 480nm. Silk fabrics showed better dyeability than cotton. Silk fabrics dyed well in acidic or neutral dyebath at $80^\circ{C}$ and cotton fabrics in neutral dyebath at $50^\circ{C}$. Both of silk and cotton fabrics showed poor dyeability in basic dyebath because of colouring anionic groups in lichen. The Munsell values of dyed silk fabrics were appeared in R(red) range, and them of cotton fabrics in YR(yellow-red) range. Light fastnesses of dyed fabrics were as poor as 2 or 2-3 grades. Also, Laundering fastnesses of dyed silk fabrics were as poor as 2 grade and those of cotton fabrics were 3 or 3-4 grades. But dry-cleaning fastnesses of all dyed fabrics were good.

• Industrial Engineering and Management Systems
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• 제6권2호
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• pp.136-145
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• 2007

The selection of suppliers and the determination of order quantities to be placed with those suppliers are important decisions in a supply chain. In this research, a non-linear mixed integer programming model is presented to select suppliers and determine the order quantities. The model considers the purchasing cost which takes into account quantity discount, the cost of transportation, the fixed cost for establishing suppliers, the cost for holding inventory, and the cost of receiving poor quality parts. The capacity constraints for suppliers, quality and lead-time requirements for the parts are also taken into account in the model. Since the purchasing cost, which is a decreasing step function of order quantities, introduces discontinuities to the non-linear objective function, it is not easy to employ traditional optimization methods. Thus, a heuristic algorithm, called particle swarm optimization (PSO), is used to find the (near) optimal solution. However, PSO usually generates initial solutions randomly. To improve the PSO solution quality, a heuristic procedure is proposed to find an initial solution based on the average unit cost including transportation, purchasing, inventory, and poor quality part cost. The results show that PSO with the proposed initial solution heuristic provides better solutions than those with PSO algorithm only.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.534-539
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• 2007

The objectives of the present work is to investigate the influence of the solution cooled absorber(SCA), refrigerant drain heat exchanger(RSX), exhaust gas/solution heat exchanger(ESX) and high efficiency solution heat exchanger on COP for a double-effect series-flow absorption chiller. A simulation program has been prepared for the cycle analysis of absorption chillers. As a result, Solution heat exchangers(LSX, HSX) are a most effective element for the COP than the others. In spite of the poor contribution to COP, SCA make a rule to reduce the crystallization phenomena of LiBr solution at solution heat exchanger. And the optimum solution split ratio are varied with the relative size of RSX and LSX.

• 설비공학논문집
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• 제20권10호
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• pp.662-668
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• 2008

The objectives of the present work are to investigate the influence of the solution cooled absorber(SCA), refrigerant drain heat exchanger(RSX), exhaust gas/solution heat exchanger(ESX) and high efficiency solution heat exchanger on COP for a double-effect series-flow absorption chiller. A simulation program has been prepared for the cycle analysis of absorption chillers. As a result, solution heat exchangers(LSX, HSX) are the most effective element for the COP than the others. In spite of the poor contribution to COP, SCA plays an important role to reduce the crystallization phenomena of LiBr solution at solution heat exchanger. And the optimum solution split ratio varies with the relative size of RSX and LSX.

• 대한수학회보
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• 제48권4호
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• pp.737-757
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• 2011

This work is concerned with an optimal selling rule for a large position of stock in a market. Selling a large block of stock in a short period typically depresses the market, which would result in a poor filling price. In addition, the large selling intensity makes the regime more likely to be poor state in the market. In this paper, regime switching and depressing terms associated with selling intensity are considered on a set of geometric Brownian models to capture movements of underlying asset. We also consider the liquidation strategy to sell much smaller number of shares in a long period. The goal is to maximize the overall return under state constraints. The corresponding value function with the selling strategy is shown to be a unique viscosity solution to the associated HJB equations. Optimal liquidation rules are characterized by a finite difference method. A numerical example is given to illustrate the result.

• 대한화학회지
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• 제16권1호
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• pp.50-55
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• 1972

The mechanical degradation of $poly(\alpha-methyl$ styrene) in several mixed solvents (chlorobenzene-n-butyl alcohol, chlorobenzene-sec-butyl alcohol, chlorobenzene-Kerosene, chlorobenzene-methylketone) was studied using the capillary flow method. The velocity constant of scission reaction (K) and the limited degree of polymerization (g) were compared at the same value of [${\eta}$], which is considered as the parameter of molecular dimension of polymers in solution. As results, (K) did not change much, even if the species and the volume fraction of poor(non-) solvents changed, while the value of (g) changed according to the species of poor (non-) solvents and the value of [${\eta}$] these results were discussed.

• International Journal of Advanced Culture Technology
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• 제11권1호
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• pp.395-402
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• 2023

The implementation of a hybrid network utilizing Power Line Communication (PLC) and Wi-Fi technologies has been demonstrated to improve signal strength and coverage in areas with poor connectivity due to internet shadow areas. In this study we strategically positioned Wi-Fi relays and utilized the capabilities of PLC technology to significantly improve signal strength and coverage in areas with poor connectivity. We also analyzed the effects of metallic obstacles on Wi-Fi signal propagation and proposed a solution to strengthen the signal enough to pass through them. Our experiment demonstrated the feasibility and potential of using this hybrid network in industrial scenarios for real-time data transmission. Overall, the results suggest that the use of PLC and Wi-Fi hybrid networks can be a cost-effective and efficient solution for overcoming internet connectivity challenges and has the potential to provide high-speed internet access to areas with unreliable signals.

• 한국수소및신에너지학회논문집
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• 제8권4호
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• pp.161-171
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• 1997

$AB_2$ type Zr-based Laves phase alloys have been studied for potential application as negative electrode in Ni/MH batteries. However, They have a serious disadvantage of poor activation behavior in KOH solution. In this work, a new method of alloy design method was tried for improving Zr-based alloy activation. this method has focused on phase controlling to make multi-phase microstructure. In the case of multi-phase Zr-V-Mn-Ni shows good performance in activation, but activation mechanism has not been known. So, we were in search of elucidating this mechanism, Using morphological and electrochemical analysis, we could find that surface morphology and electocatalytic activity of the alloy change during immersion in KOH solution. V-rich second phases are selectively corroded and dissolved and then become Ni-rich phases. Resulting from these surface reaction in KOH solution, self-hydrogen charging occurs through Ni-rich phase. However, the alloy has poor cyclic durability because of such a corrosion mechanism. Therefore, finally we developed durable alloys by substitution of other alloying element.