• 한국축산시설환경학회지
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• 제15권2호
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• pp.155-160
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• 2009

본 연구는 양돈분뇨를 이용하여 생물, 화학, 물리적 공정을 연계하여 각 공정별로 자원화 할 수 있도록 다중 분획 자원화 공정(MPAD) 기술을 개발하고 이를 현장 적용하였으며 공정별로 생산된 생산물의 비료이용 가능성에 대해 검토하였다. 특히 석회고형화 장치에서 생산된 석회처리고형물의 생산공정을 통해 자원순환형 토양개량재로서의 가능성을 살펴볼 수 있었다. 우리나라의 토양은 강원도의 영월, 정선, 충청북도의 단양, 경상북도의 문경 지역 등 일부 석회암지대를 제외하면 거의 모든 토양이 산성토양이다. 또한, 광산활동을 하고 있는 지역에서는 그 특성상 광미나 산성광산 폐수 등으로 인해 토양산성화 등의 오염이 여타지역과 비교해 매우 심각하게 발생하고 있는 실정이다. 산성폐수나 침출수를 처리할 때에는 일반적으로 중화법이 널리 사용되고 있다. 이를 위해 석회질의 alkalinity가 높은 화합물이 사용되고 있는 것으로 알려져 있으며, 산림복원이나 토양개량의 경우에도 복토재나 비료에 석회처리를 하여 오염토양을 복원하는 방법을 사용하고 있다. 석회처리고형물은 기존의 일반 퇴비에 비해 유기물과 다량의 석회질이 포함되어 있고, 다양한 크기의 펠렛으로 생산 할 수 있다. 따라서 훨씬 고품질의 퇴비를 경지에 환원할 수 있을 뿐만 아니라, 산성오염 토양 및 광해지역에서의 토양개량재로서도 그 가능성이 기대된다.

• 소성∙가공
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• 제16권2호
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• pp.126-131
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• 2007

Voids in a large rotor are formed in solidification process of a cast ingot. The voids have to be eliminated from the rotor by a forming process, because they would became stress-intensity factors which suddenly fracture the rotor in the operation. Previous studies on void-elimination of a large rotor have mainly focused on finding the process variables affecting the void-closure. But the study on the amount of void closure in a large rotor has been very rare. This study was performed to obtain an equation which predicts the amount of void-closure in a forging process of a large rotor and to evaluate the availability of the void-closure equation through finite element analyses. Firstly, 2D FE analysis was carried out to find effects of time integral of hydrostatic stress and effective strain on void volume rate of a large rotor in the upsetting process for various diameters and shapes of void, and material temperature. From the 2D FE analysis, we found that effective strain was suitable for predicting the void-closure of a large rotor, because there was a constant relationship between void volume rate and effective strain. And a void-closure equation was proposed fur predicting void-closure of a large rotor in the upsetting process. Finally, ken the 3D FE analysis, the proposed void-closure equation was verified to be useful for upsetting and cogging processes.

• 한국정밀공학회지
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• 제18권8호
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• pp.54-63
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• 2001

Rapid Prototyping(RP) techniques have their unique characteristics according to the working principles: stair-stepped surface of a part due to layer-by-layer stacking, low build speed caused by point-by-point or line-by-line solidification to build one layer, and additional posts processing to improve surface roughness, so high cost is required to introduce and to maintain the RP apparatus. The objective of this study is to develop a new RP process, Variable Lamination Manufacturing by using expandable polystyrene foam sheet as part material(VLM-S), and to design an apparatus for implementation of the process. So, the process parameters and design criterions of the apparatus were defined and the techniques were proposed to satisfy the design criterion. Based on the results, a knob-shape, pyramid shape. and a solid block were fabricated on the apparatus in which unit shape part(USP) was generated for building each layer.

• 재활간호학회지
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• 제5권2호
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• pp.217-225
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• 2002

Purpose : This research is aimed at developing a substantive theory related to the experience of adjustmented hemodialysis patients by identifying and analyzing the nature, process, and types of adjustment experienced by them. For this purpose, this study takes a grounded theory approach. Method : Data were collected from April, 2002 through September, 2002 through in-depth interviews and close observations of eleven hemodialysis patients who have experienced adjustment. With their consent, the interviews were recorded by audio tapes and later transcribed. Observation memos were also prepared on the subjects' behavior during the interviews. Data collection continued until saturated. The data were analyzed into concepts, subcategories, and categories with the open coding process. The axial coding was done to identify the relationships of the concepts and categories. And the selective coding was done to develop a core category, which is the central phenomenon of the hemodialysis patients who experienced adjustment. Result : This process resulted in 88 concepts, which may be grouped into 24 subcategories and 6 core categories. The 6 categories, in fact, depict the process of changes the patients experience from the sense of crisis, self-control, new life meaning, support system, coping ability, and quality of life improvement. And its core is self-control, which encompasses the dynamic stages from recognition, change attempts, belief solidification, and empowerment. Conclusion : The results of the research offer the following implications. First, research on adjustment is a formative stage in nursing, it is imperative for nursing researchers to develop them, which may be more relevant to nursing. Second, it is important to develop nursing intervention techniques that may be most effective in adjustment of hemodialysis patients and at the same time for each stage of changes taking place in adjustmented hemodialysis patients.

• 한국결정성장학회지
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• 제15권6호
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• pp.229-233
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• 2005

Novel process was tried to obtain micro-porous ceramic body containing continuous pore channel. $MgAl_2O_4/MgO$ eutectic fibers and rods have been grown successfully by the micro-pulling-down method, and the microstructures and optical characterizations of grown crystals were performed. $MgAl_2O_4/MgO$ eutectic fibers of $0.3{\sim}1mm$ in diameter and about 500 mm in length, and the rods having 5 mm in diameter with approximately 60 mm in length have been grown with the $6{\sim}120mm/hr$ of growth speed. The eutectic fibers showed homogeneous microstructure in which MgO fiber aligned to the growth direction in the $MgAl_2O_4$ (spinel) matrix. The grown crystals looked semitransparency under naked eyes. Optical and orientational characterizations were performed. The second phase of MgO (periclase) was easily removed by selective etching with hydrochloric acid, and then porous bodies were obtained.

• 한국재료학회지
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• 제6권1호
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• pp.12-21
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• 1996

AI-1wt%Si합금을 대상으로하여 가열주형을 이용한 수평식연속주조법에 의해 경면에면서 일방향고조직을 가진 주괴를 얻기위한 주조조건을 조사하였으며, 일방향응고된 주괴를 이용하여 신선가공하였을 경우의 다이스배열과 작업조건, 연속주조조건과 신선가공시의 단선율과의 관계를 검토하였다. 그 결과, 직경 8mm 및 4mm 주괴 모두 공정 Si상이 비교적 균일하게 분포되어 있음을 확인할 수 있었고, 이들 주괴를 중간소둔없이 20$\mu\textrm{m}$까지의 초극세선가공이 가능했다. 본 연구에서 실시한 극세선의 신선가공중에 발생한 단선은 신선가공중의 작업조건의 불충분에 기인하는 것으로 사료되었다. 따라서, 본 연구에서 얻어진 일방향응고주괴는 극세선제조에 매우 우수한 원소재임을 보여주었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.246-251
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• 2001

Solid-liquid phase change (i.e. melting or solidification) occurs in a number of situations of practical interest. Some common examples include the melting of edible oil, metallurgical process such as casting and welding, and materials science applications such as crystal growth. Therefore, due to the practical importance of the subject, there have been a large number of experimental and numerical studies of problems involving phase change during the past few decades. Also, this study presented the effective way to enhance phase change heat transfer.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 춘계학술발표대회 논문집
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• pp.195-198
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• 2000

The process of squeeze casting for metal matrix composites (MMCs) has been simulated numerically by using finite difference method. The governing equations to describe fluid flow through porous medium and heat transfer are applied to two dimensional model which is similar to a real system. A computational code has been developed to solve this problem. The influence on infiltration kinetics and solidification time of several parameters is investigated. Cooling curves and temperature distribution with time and position is also shown. The result can be used to design the squeeze casting for MMCs.

• 대한기계학회논문집
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• 제15권2호
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• pp.567-574
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• 1991

In this study thermal stress generated in three ingot moulds(GC25) during the solidification process of aluminum were analyzed by the two-dimensional thermo-elasto-plastic theory. In temperature analysis, all of the three models are shown steep temperature rising each case in initial stage of cooling. In thermal stress analysis, all of three models took compressible stress on inside wall of the mould, and tensible along with on out side. Model 2 take place less compressible, tensible stress then model 1. But model 3. have similar as thermal stress as model 2. The analysis will made one possible to calculate an optimum mould shape whose thermal stress gradient becomes minimum.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1993년도 추계학술대회 논문집
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• pp.518-523
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• 1993

A computer program has been developed for analyzing the two-dimensional unsteady conservation equations for transport phenomena in the ool region of direct rolling with semi-solid metal in order to describe the velocity and temperature, and the solidification process of the semi-solid metal. The energy equations of cooling roll is solved simultaneously with semi-solid metal in order consider heat transfer through the cooling roll. The FDM(finite difference method) and FEM(finite element method) are used in region of pool and roll, respsctively, to reduce computing time and to improve accuracy of calculation. In the present study, influence of solid fraction and casting speed are investigated in a point of view of strip formability with semi-solid metal.