• 한국물환경학회지
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• 제22권2호
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• pp.264-270
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• 2006

In this research, volume reduction of activated sludge using electrolysis was studied to find an optimum condition using lab scale experiments. Wasted sludge was treated by electrolysis with controlling current density, chloride concentration, electrode distance, and reaction time. Volume of return sludge was reduced by 9.79% in average while maximum was 16.7%. Sludge volume reduction efficiency was affected by current density and reaction time. It was reversely proportional to the electrode distance. Especially current density was effective on the system performance significantly. Electric conductivity, salinity and COD were increased by electrolysis implying sludge disintegrated and converted to COD in part. An empirical equation for total solid removal efficiency by electrolysis was proposed by multiple linear regression analysis as: $TS_{rem}$(%) = 5.534 ${\times}$ current density (A/l) + 0.178 ${\times}$ reaction time (m) + 2.758.

• 한국물환경학회지
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• 제18권2호
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• pp.123-130
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• 2002

Bench scale experiments were carried out with two biological nutrient removal(BNR) units, A/O and $A^2O$ processes, to investigate the behavior of phosphorus in the system and to compare the characteristics of phosphorus removal in two BNR processes. To achieve this goal, COD/T-P and COD/TKN ratios of the influent was varied in the range of 23~64 and 5~24, respectively. In A/O process, influent COD/T-P ratio should be kept higher than 44mg/L to meet the final effluent T-P concentration lower than 1mg/L and in $A^2/O$ process, influent COD/T-P and COD/TKN ratios higher than 56 and 10, respectively, were required for good phosphorus release and uptake with no influence of nitrate nitrogen in return sludge. At this conditions, the rate of phosphorus release in the anaerobic basin should be kept higher than 0.1 kg S-P/kg MLVSS d In A/O process, the phosphorus content of anaerobic and aerobic sludges was increased as SRT of total system was becoming longer resulting in decreasing the difference of phosphorus content between two sludges while phosphorus release in anaerobic basin and phosphorus uptake in aerobic basin was not incident. In $A^2/O$ process, the phosphorus content of anaerobic and aerobic sludges were not increased with higher SRT of total system due to the relatively high nitrate concentration in return sludge. However, the difference of phosphorus content between anaerobic and aerobic sludges was incident when phosphorus release and uptake was observed.

• 벤처창업연구
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• 제15권4호
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• pp.17-25
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• 2020

벤처부채는 벤처의 스케일업 촉진을 위한 대표적인 자금공급 수단이다. 성장 단계에서 대규모 자금 공급이 필요한 벤처기업은 지분 희석 없이 벤처부채를 지렛대로 성장을 가속화할 수 있고, 벤처캐피탈은 투자 기업의 성장이 가속화됨으로써 신속히 투자자금을 회수할 수 있다. 은행은 벤처부채의 공급을 통해 대출에 편중된 자산운용을 다양화할 수 있고 자산수익률도 제고할 수 있다. 해외 실리콘밸리은행의 사례와 같이 벤처부채 공급을 위해서는 부채자본 공급자인 은행과 지분자본을 공급하는 벤처캐피탈의 긴밀한 협력이 전제되어야 한다. 이를 위한 시장 조성 방안으로 "신용위험 분담형 벤처대출"과 "벤처대출 풀링"을 제안한다. 전자는 모태펀드와 정책보증과 같은 정책금융기관이 벤처대출에 내재한 위험을 선별하거나 우선 인수함으로써 은행의 벤처투자 시장 참여를 촉진하며, 후자는 은행과 창업벤처전문 사모펀드가 공동으로 벤처대출을 증권화함으로써 은행의 개별적인 벤처대출 실행에 따른 부담을 감소시킨다.

• Wind and Structures
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• 제4권4호
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• pp.353-366
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• 2001

With respect to serviceability, antenna masts should be designed so that wind-induced motion will not cause unacceptable lack of transmission for broadcasting users and wireless communication. For such antenna masts with directional radio transmission the serviceability limit state is predominantly governed by the tolerable change of the broadcasting angle of the mounted antenna assembly and therefore by the tip distortion of the mast. In this paper it will be shown that refinements of the present state of design of antenna masts are possible by using the statistics of extremes applied to extreme wind situations and by consideration of the statistical and reliability requirements given by the operator such as frequency and return period of passing the serviceability limit.

• 한국환경과학회지
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• 제7권4호
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• pp.511-522
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• 1998

The two-stage numerical model was used to study the relation between three-dimensional local wind seal area for Korean peninsula. The first stave is three dimensional time-dependent local wind model which elves the wind field and vertical diffusion coefncient. The second stage is advection/duusion model which uses the results of the first stage as input data. First, wand fields on Korean peninsula for none synoptic scale wand showed typical land and sea breeze circulation, and the emitted particles were transported by sea breeze for daytime, emissions return to sea by land breeze for nighttime.

• 자원ㆍ환경경제연구
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• 제28권3호
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• pp.415-435
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• 2019

본 연구의 목적은 중서부태평양(WCPFC) 수역 우리나라 원양연승어업의 눈다랑어 생산함수를 추정하여 규모 수익을 분석하는 것이다. 분석에 있어 투입요소는 선원수, 선박톤수, 투입낚시수, 눈다랑어 자원량 그리고 산출요소는 눈다랑어 생산량으로 하는 Cobb-Douglas 형태의 생산함수를 추정하였다. 함수 추정에 앞서 투입요소 중 눈다랑어 자원량은 Bayesian State-space 모델로 추정하였다. 생산함수 추정 결과, 하우즈만 검정을 통해 고정효과 모델이 선택되었고, 선원수를 제외한 선박톤수, 투입낚시수, 눈다랑어 자원량이 눈다랑어 생산량에 직접적인 영향을 미치는 것으로 나타났다. 추정된 생산함수의 투입요소를 바탕으로 규모 수익 수준을 분석한 결과, WCPFC 수역에서 눈다랑어를 조업하는 원양연승어업은 규모 수익 체증(IRS)의 성격인 것으로 추정되었다.

• 한국병원경영학회지
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• 제4권2호
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• pp.85-105
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• 1999

The main purpose of this article is to analyze the managerial performance of small and medium-size hospitals that are specialized in certain areas of medical services. Data of 189 hospitals were obtained from the data file of Korea Institute of Health Services Management The items include general characteristics of the hospitals, fianancial reports, and utilization records. Degree of specialization is measured by concentration(Herfindahl) index, and the sample hospitals are accordingly classified into specialized and unspecialized groups, by means of cluster analysis. These groups are compared in terms of various measures of managerial performance, which include several profitability indices such as operating margin, return on assets(ROA), and return on equity(ROE). To examine the relationship between specialization and managerial performance, we estimate the regression model, where the profitability indices are used as the dependent variables and the concentration index as the independent variable, controlling for the hospital characteristics such as size, type and location. Also, we perform 'Du Pont' analysis, to investigate the basic elements that can explain the differences in profitability between specialized and unspecialized hospitals. Major findings are as follows: 1. Managerial performance is better for the specilized hospitals than the unspecilized, in all aspects of profitability(operating margin, ROA, ROE). 2. Regression analysis suggests that there is a positive, statistically significant relationship beween the degree of specialization(i.e. concentration) and hospital profitability. 3. Main reason for the higher profitability of specialized hospitals lies in lower expenses rather than higher revenue. 4. In particular, personnel and material expenses are significantly smaller for the specialized hospitals, and this result seems to stem from the efficiency of operating fewer lines of business.(some kind of 'economies of scale') 5. Specialized hospitals also have fewer employees compared with the unspecialized, especially in administrative departments, which implies their efficient personnel management.

• Applied Biological Chemistry
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• 제37권4호
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• pp.303-309
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• 1994

광합성세균을 이용한 농축산가의 소규모 가축 폐수처리공정 개발을 위한 연구의 일환으로 고농도에서 유기산의 자화율이 높은 Rhodopseudomonas palustris KK14를 사용하여 돈분폐수처리공정의 최적화를 flask-scale 및 laboratory-scale에서 실시하였다. 반연속식으로 실시한 flask-scale에서 광합성세균 반응조는 HRT 6일, 광합성세균오니량 5%(v/v), 반송오니량 10%(v/v)로 했을 때 안정된 83%의 COD 제거율 및 적절한 $4{\sim}5\;g/l$의 MLSS가 유지되었다. 산생성 반응조와 광합성세균 반응조의 working volume을 각각 5.2 l와 15 l로 scale-up한 실험실적 실험에서는 원폐수 대비 COD와 BOD의 제거율이 각각 95%와 96%를 나타냈으며 광합성세균 반응조의 COD 용적부하율 및 오니부하율은 각각 $3kg\;COD/m^3/day$와 1.1kg COD/kg MLSS/day를 유지함으로써 적당한 MLSS농도가 유지되었고 부가적으로 폐수처리가 진행되면서 악취가 제거되는 효과를 나타내었다.

• 대한족부족관절학회지
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• 제23권3호
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• pp.100-104
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• 2019

Purpose: This study examined the clinical outcomes and assessed the average time to return to play following a peroneal tendon repair in Korean athletes. Materials and Methods: Between March 2004 and February 2017, a total of 30 athletes underwent peroneal tendon repair for a peroneal tendon tear. The indications of surgical treatment were chronic pain or intractable symptoms after a previous ankle sprain affecting sports activity refractory to conservative treatment for at least six months. The patient underwent tubulization for a longitudinal tendon rupture. Peroneus longus to peroneus brevis tenodesis was performed when tendon repair was impossible due to total rupture or multiple longitudinal rupture. Results: Twenty patients not included in this study were as follows: insufficient follow-up, previous surgery, and additional bone surgery. All 10 patients had a previous ankle sprain history, tenderness and swelling on the retromalleolar area. In the 10 patient population, there were five peroneus brevis tendon tears, three peroneus longus tendon tears, one peroneus longus and brevis tendon tear, and one peroneus brevis and superior peroneal retinaculum tear. In the 10 patients, six cases of peroneal brevis tendon repair and four cases of peroneal longus to brevis tenodesis were performed. The preoperative American Orthopaedic Foot and Ankle Society score was improved from a mean of 60.6 (standard deviation [SD], 8.64) to a mean of 90.2, postoperatively (SD, 4.4; p<0.012). The preoperative visual analogue scale was improved from a mean of 5.43 (SD, 1.2) to 0.5 (SD, 0.16), postoperatively (p<0.023). The mean length of time to return to play was 12.2 weeks (range, 8~16 weeks). Conclusion: Peroneal tendon tear can occur due to sports injuries. If there is tenderness at the retromalleolar area, the surgeon should consider a peroneal tendon lesion. Surgical repair of the peroneal tendon can be an effective treatment to help athletes to return to play.

• 자원ㆍ환경경제연구
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• 제27권1호
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• pp.161-194
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• 2018

본 연구는 미국 전력산업에서 협동조합과 민영전기사업자간의 소유권 형태의 차이가 기업의 운영성과에 미치는 영향을 분석한다. 2001년부터 2014년까지의 패널데이타를 구축하여 비용함수, 이중차분법 등을 추정한 결과, 협동조합은 높은 이자비용과 제한된 자금조달 등 소유권 형태로 인해 자본이용에 제한이 있고 운영한계비용 또한 기업 규모에 따라 가파르게 증가하는 반면, 민영전기사업자의 경우 상대적으로 자유로운 자본접근성을 바탕으로 전력산업에 존재하는 규모의 경제를 잘 활용하고 있는 것으로 분석되었다. 그러나 본 연구에서 소유권 형태가 기업의 수익성에 미치는 영향은 찾지 못하였으며, 발전효율성과 소유권형태의 상관관계 또한 통계적으로 유의미하지 않은 것으로 분석되었다.