• 제어로봇시스템학회논문지
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• 제7권10호
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• pp.867-873
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• 2001

The purpose of this study is to find analytic solution of determining the optimal capacity (lot-size) of multiproduct acyclic multistage production and inventory system to meet the finished product demand under the constraint of finite intermediate storage. Intermediate storage is a practical way to mitigate the material flow imbalance through the line of supply and demand chain. However, the cost of constructing and operating storage facilities is becoming substantial because of increasing land value, environmental and safety concern. Therefore, reasonable decision-making about the capacity of processes and storage units is an important subject for industries. The industrial solution for this subject is to use the classical economic lot sizing method, EOQ/EPQ(Economic Order Quantity/Economic Production Quantity) model, incorporated with practical experience. But EOQ/EPQ model is not suitable for the chemical plant design with highly interlinked processes and storage units because it is developed based on single product and single stage. This study overcomes the limitation of the classical lot sizing method. The superstructure of the plant consists of the network of serially and/or parallelly interlinked non-continuous processes and storage units. The processes transform a set of feedstock materials into another set of products with constant conversion factors. A novel production and inventory analysis method, PSW(Periodic Square Wave) model, is applied to describe the detail material flows among equipments. The objective function of this study is minimizing the total cost composed of setup and inventory holding cost. The advantage of PSW model comes from the fact that the model provides a set of simple analytic solutions in spite of realistic description of the material flows between processes and storage units. the resulting simple analytic solution can greatly enhance the proper and quick investment decision for the preliminary plant design problem confronted with economic situation.

• 에너지공학
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• 제21권1호
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• pp.68-74
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• 2012

국내 석탄화력발전소의 아역청탄과 역청탄의 혼소는 일반화되어 있으며 아역청탄의 비율이 무게 기준으로 50%가 넘는 경우도 있다. 저급탄인 아역청탄의 혼소 비율이 높아짐에 따라 연소 부산물인 비회에서 미연물질이 다량 발생하고 있으며 이는 콘크리트 혼화제로서의 비회 재활용을 가로막는 중요한 인자로 작용하고 있다. 본 연구에서는 아역청탄 혼소율이 높은 국내 500MW 표준 석탄화력발전소에서 미연물질이 포함된 비회를 입수하여 이에 대한 분석을 수행하였다. 이러한 미연물질은 석탄의 열분해 생성물인 검댕(soot)인 것으로 나타났으며 실제 석탄화력발전소에서 사용하고 있는 석탄과 혼탄의 성상 데이터와 CPD모델을 사용하여 혼탄별 검댕(soot)의 발생가능성을 분석하였다.

• 유기물자원화
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• 제25권1호
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• pp.5-13
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• 2017

기존 국내 여과판의 재질은 주로 polypropylene 소재의 여과판을 사용하였으며 그 이유는 성형성이 좋고, 가격이 저렴하며 매우 보편적으로 보급된 소재이기 때문이다. 그러나 고압에 의해 한번 뒤틀려진 polypropylene 소재 여과판은 재사용이 어려우며 가압형 고액분리모듈의 연속 운전에 문제를 야기할 수 있다. 따라서 기존 polypropylene 소재보다 성능이 뛰어난 TPU(Thermoplastic Poly Urethane) 소재개발을 위해 새로운 소재에 대해 설계된 여과판의 구조적 안정성을 해석적 기법을 통해 예측하였다. 20 bar의 압력하중 하에서 TPU를 적용한 여과판은 최대 변형량이 27.85 MPa로 나타났으며 이 값은 TPU 응력-변형률(Stress-Strain) 한계치 이하 값으로 여과판 재질에 대한 구조적 안정성을 확보하였다.

• 한국추진공학회지
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• 제20권1호
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• pp.8-13
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• 2016

연소충격완화부품은 폴리우레탄과 같은 완화소재를 사용하여 진동을 격리함으로써 추진기관이나 화공품 연소로 발생한 충격에 의해 로켓의 전자장비가 작동하지 않는 것을 방지하기 위해 사용한다. 연소충격완화부품의 성능은 굽힘 고유진동수와 전달률을 측정하여 판단할 수 있다. 본 연구를 통해 동일한 추진기관의 해외 연구결과를 통한 기준 모델의 실험 결과를 바탕으로 굽힘 고유진동수와 전달률에 대한 설계요구조건을 수립하였으며, 충분한 충격완화특성을 가지는 완화소재를 개발하여 새로운 로켓에 적합한 연소충격완화부품을 개발하였다. 본 연구는 완화소재 및 성능 측정 방법을 이용하여 연소충격완화부품을 개발하기 위해 사용할 수 있다.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2012년도 전기공동학술대회 논문집
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• pp.173-173
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• 2012

Duplex STS는 응력부식 저항이 큰 페라이트상과 우수한 내식성을 제공하는 오스테나이트상이 미세하게 1:1로 결합하여 강도가 오스테나이트 STS 보다 최소 1.7배 이상 높을 뿐 아니라 공식(pitting)과 응력부식 저항성이 우수해 최근에 주목받고 있는 고내식 고강도 재료이다. STS의 내식성을 평가하는 여러 지수 중 Pitting에 대한 내식성을 평가하는 지수로서 PREN (Pitting Resistance Equivalent Number)이 있다. PREN =%Cr + 3.3%(Mo + 0.5%W) + 16%N PREN이 30 이상이면 해안지역에서 사용가능하나, PREN이 40 이상인 경우에는 원자력발전소, 탈황 설비, 해수설비 및 화학Plant 등 고내식 환경에서 주로 사용가능하다. PREN이 40 이상인 Super Duplex STS은 다량의 Mo와 N을 첨가하여 만든 제품으로, 최근 10여 년 동안 해수 냉각 설비, 해수 담수화 설비, 탈황 설비, 석유화학 설비 및 원전용 CASK 등의 다양한 분야에 그 사용량이 꾸준히 증가하고 있는 상황이다. 본 연구에서는 Super Duplex STS의 TIG용접에서 실드가스 중의 $N_2$의 첨가가 PREN에 미치는 영향을 검토하였다. 실드가스 중 $N_2$가 용접금속으로 침입하는 메커니즘을 규명하고, 용접조건 변화에 따른 용접금속 내 N의 함량을 측정하여 PREN을 계산하고, 용접금속의 기계적 특성과 미세조직을 검토하였다.

• Journal of Microbiology and Biotechnology
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• 제30권9호
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• pp.1310-1320
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• 2020

Low-quality soil for land reuse is a crucial problem in vegetation quality and especially to waste disposal sites in mining areas. It is necessary to find suitable materials to improve the soil quality and especially to increase soil microbial diversity and activity. In this study, pot experiments were conducted to investigate the effect of a mixed material of humic acid, super absorbent polymer and biochar on low-quality soil indexes and the microbial community response. The indexes included soil physicochemical properties and the corresponding plant growth. The results showed that the mixed material could improve chemical properties and physical structure of soil by increasing the bulk density, porosity, macro aggregate, and promote the mineralization of nutrient elements in soil. The best performance was achieved by adding 3 g·kg^-1 super absorbent polymer, 3 g·kg^-1 humic acid, and 10 g·kg^-1 biochar to soil with plant total nitrogen, dry weight and height increased by 85.18%, 266.41% and 74.06%, respectively. Physicochemical properties caused changes in soil microbial diversity. Acidobacteria, Bacteroidetes, Chloroflexi, Cyanobacteria, Firmicutes, Nitrospirae, Planctomycetes, and Proteobacteria were significantly positively correlated with most of the physical, chemical and plant indicators. Actinobacteria and Armatimonadetes were significantly negatively correlated with most measurement factors. Therefore, this study can contribute to improving the understanding of low-quality soil and how it affects soil microbial functions and sustainability.

• 한국약용작물학회지
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• 제26권4호
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• pp.296-301
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• 2018

Background: The objective of this study was to investigate the effect of packaging material on the growth of rootstock of Liriope platyphylla. Methods and Results: This study examined the effects of two types of packaging material, LDPE (low density polyethylene) and functional film on the growth of the tubers of L. platyphylla, at $5^{\circ}C$. During the 16-weeks of storage period, the ratio of loss and decay of the tubers was examined at intervals of 4, 8, and 16 weeks to detect the quality of the plant. After 16 weeks of storage, the treated tubers were own. Subsequently, plant height and the number of leaves were recorded. The results revealed that functional film at $5^{\circ}C$ was the ideal material for the storage of L. platyphylla tubers. The rate of loss was the highest (57.42%) with a onion net and the lowest (22.12%) with a functional film. Similarly, the rate of tuber decay was highest (8.20%) using onion net and the least (4.60%) when the functional film was used. Conclusions: Thus, the use of the functional film proved to be the most effective in the storage of L. platyphylla tubers when compared with the LDPE.

• 한국해양공학회지
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• 제33권4호
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• pp.340-349
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• 2019

In the case of a fire accident on a ship or an offshore plant, the design of the bulkhead penetration piece must be verified via a fire test procedure (FTP), as specified by the Maritime Safety Committee (MSC). The purpose of this study is to verify both the numerical analysis results and the design specifications for penetration pieces that could be applied to the A60 class bulkhead division. In this study, the FTP was carried out in accordance with the test procedure prescribed in the MSC regulation. In order to review the fire resistance performance according to the material type, bulkhead penetration pieces for the FTP were made from brass, carbon steel for machine structures (S45C), and austenite stainless steel (SUS316). In addition, spray-type insulation and mechanical fastener-type insulation were applied to investigate the fire resistance performance according to the type of insulation. To verify the heat transfer numerical analysis results for the A60 class bulkhead penetrating piece from this test study, the design specifications of the penetrating piece material and the insulation type applicable to a ship and an offshore plant were identified.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1859-1864
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• 2004

An effective methodology is reported for the optimal design of multisite batch production/transportation and storage networks under uncertain demand forecasting. We assume that any given storage unit can store one material type which can be purchased from suppliers, internally produced, internally consumed, transported to or from other plant sites and/or sold to customers. We further assume that a storage unit is connected to all processing and transportation stages that consume/produce or move the material to which that storage unit is dedicated. Each processing stage transforms a set of feedstock materials or intermediates into a set of products with constant conversion factors. A batch transportation process can transfer one material or multiple materials at once between plant sites. The objective for optimization is to minimize the probability averaged total cost composed of raw material procurement, processing setup, transportation setup and inventory holding costs as well as the capital costs of processing stages and storage units. A novel production and inventory analysis formulation, the PSW(Periodic Square Wave) model, provides useful expressions for the upper/lower bounds and average level of the storage inventory. The expressions for the Kuhn-Tucker conditions of the optimization problem can be reduced to two sub-problems. The first yields analytical solutions for determining lot sizes while the second is a separable concave minimization network flow subproblem whose solution yields the average material flow rates through the networks for the given demand forecast scenario. The result of this study will contribute to the optimal design and operation of large-scale supply chain system.

• Natural Product Sciences
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• 제18권3호
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• pp.177-182
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• 2012

Oxidative stress potentially induces neurotoxicity which is believed to underlie several major age-related diseases of the central nervous system. This study sought to identify the cytoprotective effects of sixty-nine Cambodian plants against glutamate-induced cell death. Cultured HT22 cells were applied as an in vitro model, and neurotoxicity was induced in these neuronal cells by exposure to a determined concentration of glutamate. Sixty-nine plant sources, as Cambodia's indigenous species, were purchased from O'reusey Market, Phnom Penh, and extracted with ethanol. These extracts were screened for cytoprotective effects against glutamate-triggered neurotoxicity in HT22 cells at concentrations of 100 and 300 ${\mu}g/ml$. Of these, eight ethanol extracts, bark of Anacardium occidentale, bark and sapwood of Bauhinia pulla, flowers of Borassus flabellifer, stems and leaves of Coix lacryma-jobi, bark and sapwood of Diospyros nitida, sapwood of Dipterocarpus obtusifolius, stems of Oryza rufipogon, and fruits of Phyllanthus emblica, showed significant cytoprotective effects against glutamate-induced cell damage and degeneration in HT22 cells.