• 대한안전경영과학회지
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• 제11권1호
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• pp.121-130
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• 2009

This paper considers a six sigma project for reducing the cost copper of the cable materials in a electric wire company. The project follows a disciplined process of five macro phases: define, measure, analyze, improve, and control (DMAIC). A process map is used to identify process input variables. Three key process input variables are selected by using an input variables are selected by using an input variable evaluation table: large cable, plating, and a twisted pair. DOE is utilized for finding the optimal process conditions of the three key process input variables. The implementing result of this six sigma project is enable for reducing of the 2.8% copper materials.

• 대한자원환경지질학회:학술대회논문집
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• 대한자원환경지질학회 2003년도 춘계 학술발표회 논문집
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• pp.236-236
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• 2003

Anaerobic Fe(III)-reducing bacteria are known to be able to reduce crystalline and amorphous Fe(III) oxides. Anaerobic Fe(III)-reducing bacterial reduction can induce several kinds of secondary minerals (Fe(II) containing minerals) such as magnetite, siderite, vivianite [($Fe_{3}(PO_{4}{\cdot}2H_{2}O$], and iron sulfide (FeS) according to variety of geochemical and biological conditions. (omitted)

• Bulletin of the Korean Chemical Society
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• 제14권6호
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• pp.743-749
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• 1993

The approximate rates and stoichiometry of the reaction of excess lithium tris(dihexylamino)aluminum hydride(LTDHA) with selected organic compounds containing representative functional groups under the standardized conditions (tetrahydrofuran, 0$^{\circ}$C) were studied in order to define the reducing characteristics of the reagent for selective reductions. The reducing ability of LTDHA was also compared with those of the parent lithium aluminum hydride(LAH), lithium tris(diethylamino)aluminum hydride(LTDEA), and lithium tris(dibutylamino)aluminum hydride(LTDBA). In general, the reactivity toward organic functionalities is in order of $LAH{\gg}LTDEA{\geq}LTDBA>LTDHA$. LTDHA shows a unique reducing characteristics. Thus, the reagent reduces aldehydes, ketones, esters, epoxides, and tertiary amides readily. Anthraquinone is cleanly reduced to 9,10-dihydro-9,10-anthracenediol without hydrogen evolution, whereas p-benzoquinone in inert to LTDHA. In addition to that, disulfides are also readily reduced to thiols without hydrogen evolution. However, carboxylic acids, anhydrides, nitriles, and primary amides are reduced slowly. Especially, this reagent reduces aromatic nitriles to the corresponding aldehydes in good yields.

• Bulletin of the Korean Chemical Society
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• 제15권8호
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• pp.644-649
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• 1994

The approximate rates and stoichiometry of reaction of excess dipyrrolinoaluminum hydride (DPAH) with selected organic compounds containing representative functional groups under standardized conditions (tetrahydrofuran, 0, reagent : compound=4 : 1) were examined in order to define the characteristics of the reagent for selective reductions. The reducing ability of DPAH was also compared with that of bis(diethylamino)aluminum hydride (BEAH). The reagent appears to be stronger than BEAH, but weaker than the parent reagent in reducing strength. DPAH shows a unique reducing characteristics. Thus, the reagent reduces aldehydes, ketones, esters, acid chlorides, epoxides, and nitriles readily. In addition to that, ${\alpha},\;{\beta}$-unsaturated aldehyde is reduced to the saturated alcohol. Quinone are reduced cleanly to the corresponding 1,4-reduction products. The examination for possibility of achieving a partial reduction to aldehydes was also performed. Both primary and tertiary aromatic carboxamides are converted to aldehydes with a limiting amount of DPAH. Finally, disulfides and sulfoxides are readily reduced to thiols and sulfides, respectively.

• 대한설비공학회지:설비저널
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• 제17권4호
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• pp.395-407
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• 1988

Transient flow in a cold-water supply system for cooling the inside of a coal mining pit was numerically simulated. Properly designed and presetted pressure reducing valves control the level of pressures of the piping system at normal or emergent conditions Quasi-steady relations to simulate the valve motion are obtained and the transient performance of the valve is investigated in the present paper. The present method reasonably simulate transient phenomena in the system including the pressure reducing valve. Excessive valve motion and column separation are simulated when the flow is abruptly reduced. A calculated example of the real system is also presented. The simulation can be used for the safety-check and the guidance for design and operation in emergent cases of the system.

• Bulletin of the Korean Chemical Society
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• 제19권2호
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• pp.243-249
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• 1998

The reaction of alcohol with a solution of thexylborane (ThxBH2) in tetrahydrofuran (THF) provides a new class of mild and selective reducing agents, thexylalkoxyboranes (ThxBHOR: R=Et, i-Pr, i-Bu, s-Bu, t-Bu, Ph). In order to elucidate the effect of the alkoxy group in reduction reactions, the reducing power of ThxBHOR toward selected organic compounds containing representative functional groups under practical conditions (THF, 25°, the quantitative amount of reagent to compound) has been investigated. Generally, the reactivity of ThxBHOR is largely dependent upon the alkoxy substituent. ThxBHOR can be synthesized from a variety of alcohols, thus allowing control of the steric and electronic environment of these reagents.

• 공업화학
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• 제29권1호
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• pp.77-80
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• 2018

이온성액체를 이용하여 다양한 크기를 형성하는 은 나노입자를 합성하였다. 보다 효율적인 연구를 수행하기 위하여 통계적 방법을 이용한 실험과정 및 결과를 분석하였다. 먼저 은 입자 형성에 미치는 실험조건을 규명하기 위하여 5가지 조건, 시간, 온도, NaOH 농도, 환원제 및 이온성액체의 양의 영향을 분석하였다. 결과적으로 시간과 온도가 은 입자형성에 미치는 영향이 미미한 것으로 나타났다. 이후 나머지 3가지 인자에 대한 실험조건을 통계적으로 구성하였다. XRD 분석 결과 모든 조건에서 합성된 입자는 순수한 은 결정구조를 가지고 있었다. 합성된 은 입자의 크기를 결정하기 위하여 HR-SEM을 통해서 분석하였다. 3가지 합성조건에서는 NaOH 농도가 은 입자의 크기를 결정하는데 가장 큰 영향을 미쳤으며 환원제의 농도는 상대적으로 미비하였다. 다양한 크기를 가지는 은 입자의 합성 조건을 NaOH와 이온성액체에 대하여 통계적 방법을 이용하여 표면도와 등고선도를 제시하였다. 또한 3가지 실험조건에 따른 은 입자의 크기를 혼합물법을 이용하여 도출하였다.

• 한국도로학회논문집
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• 제17권5호
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• pp.115-122
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• 2015

PURPOSES: Recently, many local governments have applied chicanes for traffic calming to ensure environment-friendly comfortable and safe roads. However, the geometry of a chicane is designed for speed reduction using a curved portion. This study aims to improve the road geometry conditions of chicanes for reducing carbon emissions and maintaining appropriate driving speeds by considering the relationship between road geometry and carbon emissions. METHODS: This study was conducted as follows. First, carbon emissions corresponding to changing acceleration of vehicles were studied. Second, vehicle acceleration caused by the relationship between the curve radius and the straight length was studied. Accordingly, desirable conditions of curve radius and length of the straight section for reducing carbon emissions were proposed. RESULTS: The existing literature on chicanes present the minimum value of stagger length and path angle in the primary variable condition. This study suggests the maximum values of the curve radius and length of straight section in the primary variable condition. Therefore, if a vehicle's speed at a chicane is 30 km/h, this study suggests a curve radius of up to 24 m. In addition, if the vehicle's speed is 24 km/h, this study suggests a length of straight section of up to 6.6 m. These are the geometric conditions for considering the control of acceleration to the vehicle's maximum speed. CONCLUSIONS: This paper proposes an application of geometric conditions to reduce carbon emissions and maintain appropriate speeds of vehicles through a combination of curve radius and length of straight section.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2023년도 학술발표회
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• pp.48-48
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• 2023

The intensified droughts under climate change are expected to threaten stable water resource availability. Droughts exceeding the magnitude of historical variability could occur increasingly frequently under future climate conditions. It is crucial to understand how drought will evolve over time because the assumption of hydrological stationarity of the past decades would be inappropriate for future water resources management. However, the timing of the emergence of unprecedented drought conditions under climate change has rarely been examined. Here, using multimodel hydrological simulations, we investigate the changes in the frequency of hydrological drought (defined as abnormally low river discharge) under high and low greenhouse gas concentration scenarios and with existing water resources management and estimate the timing of the first emergence of unprecedented regional drought conditions that persist for over several consecutive years. This new metric enables a new quantification of the urgency of adaptation and mitigation with regard to drought under climate change. The times are detected for several sub-continental-scale regions, and three regions, namely, southwestern South America, Mediterranean Europe, and northern Africa, exhibit particularly robust and earlier critical times under the high-emission scenario. These three regions are expected to confront unprecedented conditions within the next 30 years with a high likelihood, regardless of the emission scenarios. In addition, the results obtained herein demonstrate the benefits of the lower-emission pathway in reducing the likelihood of emergence. The Paris Agreement goals are shown to be effective in reducing the likelihood to the unlikely level in most regions. Nevertheless, appropriate and prior adaptation measures are considered indispensable to when facing unprecedented drought conditions. The results of this study underscore the importance of improving drought preparedness within the considered time horizons.

• Journal of Welding and Joining
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• 제14권2호
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• pp.57-64
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• 1996

In this paper, authors are trying to find optimum spot weldig conditions to minimize indentation of the plate surface which is crucial to quality of stainless rolling stocks. At first, to derive a simple equation to estimate the depth of indentation, a simplified one-dimensional bar model is proposed and validity of the model is confirmed by experiments. And also, to find proper welding conditions giving satisfied tensile strength of the welded joint, a simple formula is derived referring to the standard spot welding conditions by AWS. Optimization problem is formulated to find welding conditions such as welding current, time and applied force which give minimum indentation and proper tensile strength of joint, and solutions are found out. According to the results, the depth of indentation can be expressed by applied electrode froces and it can be shown that an optimum applied force exists.