• Journal of Korean Society of Water and Wastewater
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• v.29 no.1
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• pp.23-31
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• 2015

Aquifer storage transfer and recovery (ASTR) is a type of managed aquifer recharge which entails injecting water into a storage well and recovering it from a different well. It has effects of natural purification when injected water passes through aquifer medium, and can be a good way of supplying water especially in a region with poor surface water quality. This study is about an on-going effort to introduce ASTR as a solution to source water problems in coastal areas. A pilot study is being conducted in the delta of the Nakdong River. A proactive management system is incorporated to ensure the water qulity in the process of drinking water process. The system is based on the Hazard Analysis and Critical Control Point (HACCP) which is a tool originated from the food industry in order to assess hazards and establish control systems for the safety of food product. In this paper, we analyze hazardous events which can occur in the entire water supply system using ASTR as a first step to the incorporation of HACCP to drinking water production process.

• Korean Journal of Organic Agriculture
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• v.12 no.2
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• pp.135-151
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• 2004

U.S. organic farming has grown rapidly-20 percent or more annually-throughout the 1990s, which kept pace with consumer demand for organically produced food. Thus certified organic acreage is the total to 235 million acres in 48 state in 2001, and SO the U.S. ranked fourth in land area managed under organic farming systems. And according to several surveys, consumer's reasons for purchasing organic food are health and nutrition, taste and environmental concerns. California and North Dakota were the top two states in 2001 for certified organic cropland; the former with mostly fruits and vegetables, and the latter with wheat, soybeans, and other crops. And the top two states for certified organic pasture were Colorado and Texas. And then several states such as Iowa and Minnesota have begun subsidizing conversion to organic farming systems as a way to capture the environmental benefits of these systems. The price of organic produce fluctuates rather broadly because of being traded by market economy principle and of demand-supply disequilibrium. Nevertheless, average price premiums for organic produce are higher than the prices for the produce under conventional farming. Future prospects for U.S. organic farming are as follows; Demand for organically grown foods is expected to continue growing at a rapid pace, as more growers convert to organic production and more processors and distributors expand organic selections in their product lines. And new processed products and new types of healthy foods are likely to appear on the market, and some new organic products will be aimed at mainstream markets.

• New & Renewable Energy
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• v.3 no.2 s.10
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• pp.24-30
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• 2007

The transient response of PEMFC (proton exchange membrane fuel cell) is important criteria in the application of PEM fuel cell to real automotive system. In this work, using a transparent unit PEM fuel cell, the transient response and cathode flooding during load change are investigated. The cell voltage is acquired according to the current density change($0.3Acm^2$ to $0.6A/cm^2$) under various stoichiometry conditions and different flooding intensities, Also the cathode gas channel images are obtained by CCD imaging system simultaneously. The different level of undershoots appeared at the moment of load changes under different cathode stoichiometries and flooding intensities. It takes about 1s that the product water comes up onto the flow channel so that oxygen supply is temporarily blocked which causes voltage loss in that "undershoot". The correlation of the dynamic behavior with stoichiometry and cathode flooding is induced from the results of these experiments.

• Journal of Sensor Science and Technology
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• v.8 no.4
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• pp.308-313
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• 1999

This paper will present an anisotropic etching in TMAH technique used in the fabrication of three-dimensional magnetic field vector sensor based on angled Hall plate structure. This sensor design relies on simultaneously detecting all magnetic field vector components using Hall plates that are imbedded into the silicon [111] sloped-surface of bulk micromachined cavity by the anisotropic etching of [100] silicon. The fabricated Hall elements has relatively improved sensitivity compare to convensional Hall elements for three-dimensional magnetic field sensing. The product sensitivity of 547V/AT at the supply current of 1.0mA was achived. The corresponding limit in the detection of magnrtic field is 0.07G that calculated by measured power spectral density(PSD) in magnetic sensor output.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.35 no.3
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• pp.204-209
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• 2012

본 논문은 전국적인 소매업체의 각 지점별 고객 수요가 불확실한 상황에서 고객 서비스 목표 수준을 충족하는 최적재고 수준을 결정하는 문제에 대해 연구하였다. 이를 위해 전국에 분포한 지점에서 물품을 판매하는 베스트바이, 월마트, 혹은 시어스와 같은 전국적인 소매업체 관점에서 사용할 수 있는 핵심 관리 지표(KPI)로서 ISR(In-Stock Ratio)를 정의하였으며, 전국적인 소매업체가 평균 ISR로 정의되는 고객 서비스 목표 수준을 충족하면서 각 지점 보유 재고의 총합을 최소화할 수 있는 최적화 모델을 수립하였다. 본 논문은 해당 모델에 항상 최적해가 존재함을 증명하고 해당 최적해를 Karush-Kuhn-Tucker 조건을 사용하여 고객 수요의 확률분포의 형태에 상관없이 일반화된 형태로 표현하였다. 또한 본 논문은 고객 수요가 정규분포와 같은 특정 확률분포를 따르는 경우에 대해 연구하였으며, 이 경우에 대한 최적 재고수준을 나타내는 식을 도출하였다. 마지막으로 본 논문에서는 상기 기술된 상황에 대한 수리적인 예제를 통하여 최적재고 수준과 확률분포 파라미터들간의 관계를 분석하였다.

• 한국태양에너지학회:학술대회논문집
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• 2011.04a
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• pp.133-137
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• 2011

Low-e glazing is classified as soft low-e glazing and hard low-e glazing. Hard low-e glazing can be temperable and its handling is comfortable because its coating film is a oxide film generated at high temperatures. But there is a fatal weakness that its insulation performance and shielding performance are lower compared to soft low-e glazing by low electrical conductivity of coating film. Soft low-e glazing is excellent because its coating film consists of Ag that is excellent electrical conductivity and it has strength that can supply various product consumers want. But soft low-e glazing has weaknesses that temperable and handling are difficult because Ag is oxidized easily. Therefore this study analyzes thermal performance of glazing by changing filling gas according to applying low-e glazing through simulation to judge performance before making sample. After this process, a comparative experimental study was done through TVS by making temperable low-e glazing.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.5
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• pp.212-217
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• 2014

Recently, the use of renewable energy has been increased due to growing concern on the energy-saving at buildings and the reduction of $CO_2$ emission. In the field of architecture, to reduce the energy consumption of heating, cooling and hot water supply, heat pump systems with renewable energy has been developed and used in various applications. However, there have been many of researches on the large-scale commercial heat pump systems, but the research and the field application of a compact heat pump system is rare. Therefore, in order to develop the compact heat pump for the small-scale residential building, this study conducted the performance test and feasibility study for a hybrid heat pump using the heat source of air, solar and ground. In the results of experiments through a trial product, the average COP of cooling mode with ground heat source was 4.75, and it of heating mode was 4.03. Furthermore, the average COP of cooling mode with air heat source was 2.60, and it of heating mode was 2.92. Finally, payback period of the system was calculated as 9.2 years.

• Nuclear Engineering and Technology
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• v.50 no.1
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• pp.126-131
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• 2018

As it is known, uranium enrichment is carried out on industrial scale by means of multistage separation facilities, i.e., separation cascades in which gas centrifuges (GCs) are connected in series and parallel. Design and construction of these facilities require significant investment. So, the problem of calculation and optimization of cascade working parameters is still relevant today. At the same time, in many cases, the minimum unit cost of a product is related to the cascade having the smallest possible number of separation elements/GCs. Also, in theoretical studies, it is often acceptable to apply as an efficiency criterion the minimum total flow to supply cascade stages instead of the abovementioned minimum unit cost or the number of separation elements. In this article, cascades with working parameter of a single GC changing from stage to stage are optimized by two of the abovementioned performance criteria and are compared. The results obtained allow us to make a conclusion about their differences.

• Transactions of Materials Processing
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• v.18 no.1
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• pp.39-44
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• 2009

This paper is concerned with forming technology of an automotive front side member part with ultra high strength steel sheet of DP980. The forming technology considered in this paper is the draw & form type, which installs the upper pad and lower pad to produce the complicated shape of ultra high strength steel sheet. In order to produce sound product, comparison between form type and draw & form type and between draw type and draw & form type are investigated by FE-analysis. FE-analysis is carried out with commercial sheet metal forming analysis S/W, DYNAFORM. It was shown from FE-analysis that the draw & form type satisfied the required specifications such as the dimensional accuracy and soundness of automotive front side member part. The effectiveness of the analytical result was verified by the experiment. From this investigation, the draw & form type is proved to be able to supply useful forming technology in forming ultra high strength steel.

• Korean Journal of Veterinary Service
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• v.27 no.2
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• pp.115-120
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• 2004

Contents of nitrites was tested in 2,290 meat products during 2000-2003, in Seoul by Diazoa method. It was detected over 40 ppm NO$_2$$\^$-/ contents in 20 hams, 7 sausages, one bacon, and one crushed meat product respectively. Also, over 20ppm nitrites was 21.8%(240/1,103) in hams, 20.7%(122/589) in sausages, 6.8%(14/205) in crushed meats, and in 6.0%(5/83) bacons respectively. In case of average contents and contents range, 0.012 g/kg, ND-0.116 g/kg in hams, 0.012 g/kg, ND-0.066 g/kg in sausages, 0.010 g/kg, 0.001-0.089 g/kg in bacons, and 0.006 g/kg, ND-0.040 g/kg in crushed meats etc. Specially, in sausages, it was increased continually by years, in not only average nitrites contents but also their contents range, also, in case of bacons, increased continually by years on only average nitrites contents. According to results, the NO$_2$$\^$-/ contents monitoring for the processed meat products must be reinforced to supply safety food for the citizens.