• Advances in environmental research
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• 제12권1호
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• pp.17-40
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• 2023

This article presents studies of the adsorption process in a continuous system of fluoride solutions at a concentration of 30 mg/L using a bone char packed in fixed-bed columns, as well as regeneration studies in the same system using HNO₃, HCl and NaOH at 0.01, 0.1 and 1 M. The Thomas Model, Artificial Neural Networks (ANNs), Numerical Integration and Mass Transfer Zone were used for the modeling of asyemmetrical breakthrough curves obtained from the fluoride adsorption on bone char. The maximum adsorption capacity of the breakthrough curves was estimated, and various design parameters of the columns were obtained for the different operating conditions. Results showed that an improvement in the modeling capabilities of the Thomas model can be obtained using ANNs. Moreover, ANNs are useful for determining reasonable and accurate design parameters of packed-bed adsorption columns. This modeling approach can be useful for the process system engineering of dynamic adsorption systems involved in the field of water treatment and purification. It is important to highlight that the obtained results indicate that, when using HCl or HNO₃ at a concentration of 0.1 M, a large number of adsorption-desorption cycles are obtained and, therefore, the highest values of adsorption capacity, which leads to a reduction in operation costs.

• 의료ㆍ복지 건축 : 한국의료복지건축학회 논문집
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• 제25권4호
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• pp.93-104
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• 2019

Purpose: To establish the building guidelines and to analyze the function of Regional Public Hospitals, the survey was conducted primarily on the current status focusing on the location and relationship of the department, area composition ratio, area per bed, and area per operating room. Methods: The research methods of this paper are as follows. 1) A literature survey on the function of the operating and related departments, 2) A drawing analysis for spatial composition and net area calculation. Results: The area of the Operation Department in the Regional Public Hospitals with 200 to 300 beds are as follows. Area ratio: 3.35%, area per Bed: 2.53㎡/bed, the number of beds per operating room: 64.37bed, area per operating room: 146.46㎡/n, area per operating room by plan type: integration corridor 133.84㎡/n, separation corridor 184.82㎡/n. Implications: This paper analyzed data on the current state of Operation Departments for setting up the function and role for the Regional Public Hospital. In the future, it is also required to provide size that takes into account user behavior and the user's psychological aspect in order to suggest appropriate area.

• 태양에너지
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• 제14권2호
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• pp.91-101
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• 1994

[ $Ca(OH)_2/CaO$ ]계 가역반응 싸이클을 이용하는 화학축열에서 열전도도가 낮은 고체입자 충전층의 전열성능을 개선하여 축열장치의 효율을 높이고자 한다. 본 연구에서는 반응기내의 CaO 입자 충전층의 전열성능 향상을 도모하기 위해 반응기 속에 구리판으로 된 전열핀을 설치하고 수화발열 반응시의 방열특성을 조사 하였다. 이 때 반응조건의 변화에 따른 반응층내의 온도 분포를 조사하고 전열촉진 효과에 대해 검토하였다. 그 결과 구리판 전열핀의 방열촉진 효과로 인하여 수화발열반응의 방열시간이 전열핀을 사용하지 않은 때보다 1/2 이상 단축되었으며, 방열시간은 전열핀의 매수에 가장 많은 영향을 받았다.

• Korean Chemical Engineering Research
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• 제58권2호
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• pp.307-312
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• 2020

최근 대기압이하 진공 압력 상태에서 운전되는 유동층 반응기는 진공건조 공정이나 플라즈마 화학증착과 같이 감압 유동화가 요구되기에 관심이 증대되어 왔다. 그러나 대기압 이하에서 운전되는 유동층의 수력학적 특성 연구는 많이 연구되지 않았다. 본 연구에서는 대기압 이하에서 운전하는 유동층의 압력강하를 층내 압력을 1.33 에서 101.3kPa 까지 변화시키며 측정하였다. 유동층의 운전 압력이 진공인 상태에서는 최소유동화속도가 압력이 감소함에 따라 증가하며, 이는 기체 밀도와 평균 자유경로 변화와 같은 slip 흐름에 의한 변화이다. 또한 기존의 상압 상태에서 운전되는 유동층의 최소유동화속도 상관식과 비교함으로써 압력 감소에 따른 slip 흐름의 영향 뚜렷하게 나타남을 가리키는 임계 Knudsen 수를 결정하였다. 이로부터 slip 흐름이 주도하기 시작하는 임계 압력을 실험적으로 결정하였다.

• 한국조경학회지
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• 제34권3호
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• pp.79-90
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• 2006

Tamarix chinenis blooms twice a you and its flowers, branches and leaves make the adjustment of tree shape. Propagation methods and growth characteristics of T. chinensis were studied in order to ascertain its potential use as one of vegetation resources for coast forestation and landscaping. The study results indicated that 1 or 2 you old hard wood cuttings showed higher rooting ratio than greenwood or semi hard wood cuttings. One to one mixture between vermiculite and pearlite appeared to be the best for bed soil, and sea sand and silt(loess) mixture was the next. Sea sand and granitic soil followed after. In terms of seasonal differences, spring cuttings showed the best rooting ratio, root number, and root length. Fall cuttings followed after spring cutting, and summer cuttings showed worst results regarding rooting ratio, root number, and root length. The best rooting promotion effects of growth regulators were observed with sea sand bed soils. There was no significant difference among growth regulators in terms of rooting and shoot growth. Low concentration below 100 ppm of growth regulators was enough for rooting promotion effect. In general, the number and mean length of roots and shoots were showed the excellent records in the sites with high rooting ratio. The study result strongly showed that T. chinensis can be considered as a suitable tree for coast forestation and landscaping because of its easy cutting propagation and rapid growth on saline lands.

• 한국병원경영학회지
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• 제14권2호
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• pp.1-20
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• 2009

The purpose of this study is to find the determinant variables to make profitability in regional public hospitals. The data come from financial statements and annual reports of 34 regional public hospitals for five years (from year 2003 to year 2007). The T or F-test and hierarchical multiple regression analysis are used. The dependant variables are the profitability indicators, ordinary income to total asset and operating margin to gross revenue, and the independent variables are general characteristics, diagnosis and treatment patterns, financial and public benefits. The findings of this study are summarized as follows. First, Variables affecting the profitability indexes revealed from DEA results is the bed occupancy rate, number of hospitalized patients to outpatients, ratio of first medical examination for outpatients, number of daily patients per medical specialist, labor cost per patient and managerial expenses per patient. Second, the ordinary income to total asset representing the asset usage performance is affected by the average hospitalized days, bed occupancy rate, labor cost per patient and ratio of patients with medical insurance coverage. Third, the operating martin to gross revenue obtained from the actual operations of hospitals has its significance with the bed occupancy rate, number of hospitalized patients to outpatients, managerial expenses per patient and public benefit indicator. This study has some restriction not to use pannel data analysis, although it used data for five years. Accordingly, various additional studies should be done to supplement such problems.

• 한국산학기술학회논문지
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• 제7권6호
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• pp.1264-1270
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• 2006

본 연구에서는 달천 하류의 수리적 특성 및 유사론적 특성을 파악하기 위해 준2차원 모형인 GSTARS 2.1 모형을 적용하였다. GSTARS 2.1 모형에 포함된 Meyer-Peter와 Muller공식, Acker와 White's공식, Engelund와 Hanson공식 그리고 Yang공식의 네 가지 유사이송공식을 1984년부터 1992년까지의 하상단면에 대해 모의하였으며, 그 결과 Meyer-Peter와 Muller공식이 실측치에 근사한 것으로 나타났다. 정량적인 비교에서 각 단면별로 92년 실측치보다 모형에 의한 계산치가 하상변동량이 약간 과소로 산정되었다. Meyer-Peter와 Muller공식을 적용하여 유관 개수에 따른 하상변동의 효과를 분석하였다.

• 한국해양학회지:바다
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• 제18권4호
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• pp.227-233
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• 2013

경남 통영시 민양 잘피밭에 서식하는 어류의 종조성 및 계절 변동을 조사하기 위해 2011년 5월부터 2012년 4월까지 예인망(surf net)을 이용하여 매월 어류를 채집하였다. 조사기간 동안 총 25종 3,880개체 3,145.1 g의 어류가 채집되었다. 조사기간 동안 채집된 어류는 대부분 소형어나 유어들이었고, 그 중 우점종은 1,970개체가 채집된 살망둑(Gymnogobius heptacanthus)이였으며, 그물코쥐치(Rudarius ercodes), 베도라치(Pholis nebulosa), 별망둑(Chaenogobius gulosus), 날망둑(Gymnogobius castaneus) 순으로 채집되어 총 개체수의 89.1%를 차지하였다. 잘피밭 출현 어류는 수온이 대체적으로 높은 6-9월 사이 다수의 개체가 출현하였고, 수온이 낮은 1-2월에 개체수와 종수가 적게 나타나 수온의 영향을 받고 있는 것으로 보인다. 한편, 종 다양도지수(H')는 2012년 4월이 가장 높게 나타났다.

• 한국환경과학회지
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• 제20권5호
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• pp.555-564
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• 2011

This study examines the potential restoration of abandoned channels of the Mangyeong River in South Korea. To analyze the morphological changes and equilibrium conditions, a flow duration analysis was performed to obtain the discharge of 255 m3/s with a recurrence interval of 1.5 year. It is a gravel-bed stream with a median bed diameter of 36 mm. The reach-averaged results using HEC-RAS showed that the top width is 244 m, the mean flow depth is 1.11 m, the width/depth ratio is very high at 277, the channel velocity is 1.18 m/s, and the Froude number is also high at 0.42. The hydraulic parameters vary in the vicinity of the three sills which control the bed elevation. The total sediment load is 6,500 tons per day and the equivalent sediment concentration is 240 mg/l. The Engelund-Hansen method was closer to the field measurements than any other method. The bed material coarser than 33 mm will not move. The methods of Julien-Wargadalam and Lacey gave an equilibrium channel width of 83 m and 77 m respectively, which demonstrates that the Mangyeong River is currently very wide and shallow. The planform geometry for the Mangyeong River is definitely straight with a sinuosity as low as 1.03. The thalweg and mean bed elevation profiles were analyzed using field measurements in 1976, 1993 and 2009. The measured profiles indicated that the channel has degraded about 2 m since 1976. The coarse gravel material and large width-depth ratio increase the stability of the bed material in this reach.

• 한국수자원학회논문집
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• 제33권6호
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• pp.711-723
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• 2000

현재 사용되고 있는 소류사량 산정식들은 형식의 다양함과 관련변수들의 불일치로 각 공식의 특징을 파악하기 힘들며 사용된 관측자료가 다르기 때문에 상대적인 비교가 어렵다. 한편 산정식의 유도과정에서 사용되는 기본적인 가정들의 개선여지가 많은 것으로 판단된다. 이러한 문제점들을 해결하기 위하여 소류사량과 직접적으로 관련된 여러 무차원수들을 제시하고 그들간의 관계식을 도출하였으며 가장 적합하다고 판단되는 무차원수를 도입하여 형식의 통일을 기하였다. van Rijn이 제시한 관계식을 보다 간단한 형식으로 도출하여 새로운 소류사량 산정식을 개발하였다. Brownlie(1981)가 수집 정리한 관측자료와 개발식을 대비하여 경험 계수의 적합한 수치를 도출하였으며 광범위한 조건에서 유효하고 정밀도가 높은 조정식을 개발하였다.