• Structural Engineering and Mechanics
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• 제28권1호
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• pp.89-105
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• 2008

The paper presents a study on the effects of soil-structure-interaction (SSI) on the performance of the compliant liquid column damper (CLCD) for the seismic vibration control of short period structures. The frequency-domain formulation for the input-output relation of a flexible-base structure with CLCD has been derived. The superstructure has been modeled as a linear, single degreeof-freedom (SDOF) system. The foundation has been considered to be attached to the underlying soil medium through linear springs and viscous dashpots, the properties of which have been represented by complex valued impedance functions. By using a standard equivalent linearization technique, the nonlinear orifice damping of the CLCD has been replaced by equivalent linear viscous damping. A numerical stochastic study has been carried out to study the functioning of the CLCD for varying degrees of SSI. Comparison of the damper performance when it is tuned to the fixed-base structural frequency and when tuned to the flexible-base structural frequency has been made. The effects of SSI on the optimal value of the orifice damping coefficient of the damper has also been studied. A more convenient approach for designing the damper while considering SSI, by using an established model of a replacement oscillator for the structure-soil system has also been presented. Finally, a simulation study, using a recorded accelerogram, has been carried out on the CLCD performance for the flexible-base structure.

• 한국간호교육학회지
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• 제20권2호
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• pp.321-331
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• 2014

Purpose: The purpose of this study was to investigate the effects of case management service for hypertensive elderly patients through the customized visiting home health care program. Method: Non-equivalent control group pretest-posttest design was employed. Data were collected from April 2007 to January 2009. Among a total of fifty subjects, 25 subjects were belonged to the case management group and the others were belonged to the general management group. Results: 1) In experimental group, significant increasing rate of number of people within normal blood pressure by time, but no significant increasing rate of number of people within normal blood neutral fat, total cholesterol, HDL, & LDL. 2) In experimental group, the score of knowledge about disease and healthy life practice were increased on 8 week period but decreased on follow up period. Number of people within normal blood HDL and mean score of healthy life practice were significantly higher than control group on follow up period. Conclusion: Case management service was effective on controlling blood pressure but partly effective on blood lipid, knowledge about disease, and healthy life practice in hypertensive patients. Further study is needed to conduct a periodic re-evaluation of the effect of case management and to verify an optimal interval to provide the case management service.

• 대한전자공학회논문지TC
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• 제49권2호
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• pp.1-8
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• 2012

본 논문에서는 인지 무선 시스템에서의 새로운 프레임 길이 제어 방법을 제안한다. 제안된 방법에서는 유휴 기간 동안 시간이 지남에 따라 일차 사용자 패킷이 도착할 확률이 지속적으로 증가하는 특성을 이용한다. 증가하는 일차 사용자 패킷 도착확률에 따라 이차 사용자의 프레임 길이를 줄이면, 스펙트럼 센싱은 시간이 지남에 따라 더 자주 실행되며 일차 사용자의 도착 유무는 더욱 빠르게 검출될 수 있다. 간섭 제한량을 만족시키는 조건 하에 이차 사용자의 전송률을 극대화하는 최적의 프레임 길이를 구한다. 또한, 이러한 프레임 길이 제어 방법을 사용하였을 때의 상당량의 전송률 향상이 있음을 보인다.

• 한국멀티미디어학회논문지
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• 제12권3호
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• pp.436-444
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• 2009

최근 들어 센서 네트워크에 대한 관심이 증가됨에 따라서 다양한 분야에서 이를 활용한 연구가 이루어지고 있다. 본 논문에서는 센서 네트워크 기반 강의실 제어 시스템을 제안하고 구현한다. 강사의 강의 이력 정보를 센서 네트워크를 통하여 수집하고, 이 정보를 활용하여 강사가 강의실에 들어갈 때 강의실 내 PC, 빔 프로젝터, 전등 등을 강의에 적합한 형태로 제어해 주면 효과적인 강의 진행이 가능하다. 본 논문에서 제안한 강의실 제어 시스템이 효과적으로 동작할 수 있도록 센서 네트워크를 구축하고 성능 실험을 한다. 이를 통하여 강의실에 설치한 센서 노드의 메시지 발생 주기와, 센서 노드 간 통신이 원활하게 이루어질 수 있도록 강의실 내 배치된 센서 노드의 수를 최적화할 수 있는 값을 구하였다.

• 대한토목학회논문집
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• 제38권6호
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• pp.793-800
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• 2018

본 연구는 최근 빈번히 발생하는 홍수재해에 대비하고 안정적인 치수대책 수립을 위하여 공학적 판단에 근거한 하천의 적정 설계빈도 결정방안을 제시하였다. 지방하천의 설계빈도는 하천의 중요도 및 지역특성에 따라 최소 50년부터 최대 200년까지 설정되고 있으나, 적용범위가 넓어 하천의 지형적, 치수적 특성을 제대로 반영하지 못하는 실정이다. 본 연구에서는 지방하천의 적정 설계빈도를 결정하기 위하여 7개의 평가인자(시가화 침수면적, 유역면적, 형상계수, 하도경사, 수계 및 하천차수, 배수영향구간, 이상강우 발생빈도)에 대하여 베이즈 이론을 적용하여 가중치를 산정하였다. 또한, 기후변화를 고려한 홍수피해잠재능을 산정하였고, 시군구별 잠재능을 구분하여 적정 설계빈도를 결정하였다. 충청남도 382개 지방하천에 대하여 현행 설계빈도의 적정성을 평가하였다. 382개의 현행 하천설계빈도보다 상향되는 하천은 65개 하천으로 상대적으로 시가화 침수면적이 크게 산정되고 홍수피해잠재능이 큰 지역의 하천이며, 하향되는 하천은 169개로 분석되었다.

• Journal of Astronomy and Space Sciences
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• 제38권4호
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• pp.217-227
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• 2021

In this study, we describe an analytical process for designing a low Earth orbit constellation for discontinuous regional coverage, to be used for a surveillance and reconnaissance space mission. The objective of this study was to configure a satellite constellation that targeted multiple areas near the Korean Peninsula. The constellation design forms part of a discontinuous regional coverage problem with a minimum revisit time. We first introduced an optimal inclination search algorithm to calculate the orbital inclination that maximizes the geometrical coverage of single or multiple ground targets. The common ground track (CGT) constellation pattern with a repeating period of one nodal day was then used to construct the rest of the orbital elements of the constellation. Combining these results, we present an analytical design process that users can directly apply to their own situation. For Seoul, for example, 39.0° was determined as the optimal orbital inclination, and the maximum and average revisit times were 58.1 min and 27.9 min for a 20-satellite constellation, and 42.5 min and 19.7 min for a 30-satellite CGT constellation, respectively. This study also compares the revisit times of the proposed method with those of a traditional Walker-Delta constellation under three inclination conditions: optimal inclination, restricted inclination by launch trajectories from the Korean Peninsula, and inclination for the sun-synchronous orbit. A comparison showed that the CGT constellation had the shortest revisit times with a non-optimal inclination condition. The results of this analysis can serve as a reference for determining the appropriate constellation pattern for a given inclination condition.

• 한국환경과학회지
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• 제22권10호
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• pp.1353-1361
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• 2013

The objectives of this paper are the characterization of the pretreatment of wastewater by microfiltration (MF) membranes for river maintenance and water recycling. This is done by investigation of the proper coagulation conditions, such as the types and doses of coagulants, mixing conditions (velocity gradients and mixing periods), pH, etc., using jar tests. The effluent water from a pore control fiber (PCF) filter located after the secondary clarifier at Kang-byeon Sewage Treatment Plant (K-STP) was used in these experiments. Two established coagulants, aluminum sulfate (Alum) and poly aluminum chloride (PAC), which are commonly used in sewage treatment plants to treat drinking water, were used in this research. The results indicate that the optimal coagulation velocity gradients (G) and agitation period (T) for both Alum and PAC were 200-250 $s^{-1}$ and 5 min respectively, but the coagulation efficiencies for both Alum and PAC were lower at low values of G and T. For a 60 min filtration period on the MF, the flux efficiencies ($J/J_0$ (%)) at the K-STP effluent that were coagulated by PAC and Alum were 92.9 % and 79.9 %, respectively, under the same coagulation conditions. It is concluded that an enhanced membrane process is possible by effective filtration of effluent at the K-STP using the coagulation-membrane separation process.

• 한국식품조리과학회지
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• 제10권4호
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• pp.315-321
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• 1994

The addition of green tea to kimchi making for extanding the optimum edible period was studied. The equality and sensory characteristics of green tea added kimchi were evaluated. The acidity, lactic acid and acetic acid contents of green tea added kimchi showed lower than that of control kimchi but reducing sugar and vitamin C contents was higher. The duration of optimum edible periods of green tea added kimchi lasted two more weeks. While the optimum pH of kimchi for eating lasted, the sensory pannel score for sour taste of green tea added kimchi was lower than that of control but the scores for overall quality and hardness were higher. Especially, the sour taste score between two groups were significantly different(p<0.05). There was no differences in texture determined by Penetrometer between green tea added kimchi and control kimchi until the fermentation reached the optimal condition for eating. After that period, the degree of degradation of texture was much delayed in green tea added kimchi.

• 물과 미래
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• 제29권1호
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• pp.235-248
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• 1996

홍수기중의 홍수조절과 이수의 서로 상반된 목적을 다루기 위해 예비방류 방안을 제안하였다. 예비방류 방안은 홍수조절목적의 가변제한수위와 이수목적의 최소확보 저수위를 고려하는 경우에, 홍수예측과 하류 조절점에서의 유량으로부터 저수지의 최적방류량을 결정하는데 이용할 수 있다. 본 모형은 대청과 충주다목적 댐을 대상으로 모의운영하였다. 예비방류의 시기와 크기를 결정하는 절차를 설명하고, 또한 과거의 홍수사상을 토대로 그 효과에 대해서도 검토하였다. 모의운영한 결과에 의하면 예비방류 방식의 조절방안은 단일 다목적 저수지의 홍수기중 최적 운영계획을 수립하는데 효율적이며, 아울러 실제의 홍수시에는 실시간 운영과 병행하여 이용할 수 있다.

• Journal of Electrical Engineering and Technology
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• 제5권4호
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• pp.530-537
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• 2010

By development of renewable energy and more efficient facilities in an increasingly deregulated electricity market, the operation cost of distributed generation (DG) is becoming more competitive. International environmental regulations of the leaking carbon become effective to reinforce global efforts for a low-carbon paradigm. Through increased DG, operators of DG are able to supply electric power to customers who are connected directly to DG as well as loads that are connected to entire network. In this situation, a community energy system (CES) with DGs is a new participant in the energy market. DG's purchase price from the market is different from the DG's sales price to the market due to transmission service charges and other costs. Therefore, CES who owns DGs has to control the produced electric power per hourly period in order to maximize profit. Considering the international environment regulations, CE will be an important element to decide the marginal cost of generators as well as the classified fuel unit cost and unit's efficiency. This paper introduces the optimal operation of CES's DG connected to the distribution network considering CE. The purpose of optimization is to maximize the profit of CES. A Particle Swarm Optimization (PSO) will be used to solve this complicated problem. The optimal operation of DG represented in this paper would guide CES and system operators in determining the decision making criteria.