• 대한전기학회논문지:전력기술부문A
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• 제52권9호
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• pp.513-520
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• 2003

Service restoration is an emergency control in distribution constrol centers to restore out-of-service area as soon as possible when a fault occurs in distribution networks. therefore, it requires fast computation time and high quality solutions for load balancing. In this paper. a load balance index and heuristic guided best-first search are proposed for these problem. The proposed algorithm consists of two parts. One is to set up a decision tree to represent the various switching operations available. Another is to identify the most effective the set of switches using proposed search technique and a load balance index. Test results on the KEPCO's 108 bus distribution system show that the performance is efficient and robust.

• The Journal of Korean Physical Therapy
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• 제17권3호
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• pp.413-420
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• 2005

The purpose of this study was to determine differences of balance performance to upright standing, forward bending posture, and sudden load during forward bending posture in subjects with and without a history of low back pain. A study was conducted on 8 subjects with low back pain and 13 healthy subjects. Dynamic Balance System was used to measure the postural sway index, left-right sway index, and anterior-posterior sway index on balance performance. There were no differences between subject groups on balance performance during upright standing. Balance performance was increased in forward bending posture and decreased in sudden load during forward bending posture in subjects with low back pain. These results suggest that subjects with low back pain demonstrated increased activity and decreased reaction times of trunk muscles.

• 대한전기학회논문지:전력기술부문A
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• 제51권5호
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• pp.217-224
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• 2002

This paper presents an algorithm to obtain an approximate optimal solution for the service restoration and load balancing of large scale radial distribution system in a real-time operation environment. Since the problem is formulated as a combinatorial optimization problem, it is difficult to solve a large-scale combinatorial optimization problem accurately within the reasonable computation time. Therefore, in order to find an approximate optimal solution quickly, the authors proposed an algorithm which combines optimization technique called cyclic best-first search with heuristic based feeder loadings balance index for computational efficiency and robust performance. To demonstrate the validity of the proposed algorithm, numerical calculations are carried out the KEPCO's 108 bus distribution system.

• Environmental Engineering Research
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• 제23권2호
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• pp.150-158
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• 2018

The deteriorating role of Nakdong River due to the Four Major Rivers Project has caused a series of problems, including water pollution, drying streams, aggravation of the hydroecology. Geumho River and Gyeongseong-cheon had a higher concentration index and is believed to impact the water quality of the main stream. The influence index of Geumho River and Nam River between 2015 and 2016, which have a large amount of discharge, was the highest among the tributaries in terms of the load material balance. Showing the highest average concentration and average load in the index assessment, Geumho River is believed to require an intensive management for improving the water quality of the main stream. Furthermore, when the cumulative percentage of the average concentration and average load was compared based on the water quality improvement of the tributaries mixed to Nakdong River, which was set to 60%, Geumho River, Nam River, Topyeong-cheon, and Cha-cheon, which showed the highest ratio in that order, were determined to require a water quality management program as a priority.

• 환경생물
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• 제37권4호
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• pp.554-567
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• 2019

최근 농경지 투입양분으로 인한 환경영향의 우려와 함께 하천 등으로 유출되는 양분의 오염부하 관리가 요구되고 있다. 이에 정부는 국내 농지의 양분 과잉 투입 문제를 해결하기 위해 농경지의 양분관리 목표를 설정하여 관리하는 양분관리제도의 도입을 추진하고 있다. 본 연구는 국내 합리적인 양분관리제도 도입을 위한 양분관리 지표 기준을 설정하고자 도 단위의 양분부하와 양분수지 지표를 분석하고 지표별 특성을 비교 검토하였다. 도 단위 질소와 인성분의 양분부하와 양분수지 분석에서 지역별 양분부하 순위와 양분수지 순위가 다르게 나타나, 지역의 양분수준을 평가하는데 있어 양분부하와 양분수지의 두 지표는 서로 상이한 지표 값을 도출하는 것으로 나타났다. 양분부하와 양분수지 간의 상관관계 분석에서 질소성분의 경우 상관관계 계수(r)는 0.2504로서 5% 유의수준에서 통계적 유의성이 없었으며, 인성분의 경우 상관관계 계수(r)가 0.7375로서 5% 유의수준에서 통계적 유의성이 인정되었다. 따라서 양분관리 지표활용에 있어 인성분의 경우 양분부하와 양분수지 간의 상호 호환성이 나타났으나, 질소 성분의 경우 양분부하와 양분수지 간의 상호 호환성이 없는 것으로 나타났다. 따라서 지역의 양분관리 지표로서 농업환경 특성을 반영하는 양분수지 지표의 활용이 합리적인 것으로 평가되었다.

• 조명전기설비학회논문지
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• 제18권5호
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• pp.162-168
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• 2004

정전복구 문제는 배전계통에서 고장이 발생한 겨우 사고 구간 이후의 비 고장 정전구간내의 부하를 적절한 스위칭을 통하여 인접된 건전피더로 빠른 시간 내에 절체 시키는 것이며 이때 방사상 선로구성, 전압, 전류 등의 제약조건들이 만족되어야 한다. 본 논문에서는 건전피더들이 고장 발생 직후 계통으로 공급하여야 할 부하의 총량을 규정하는 함수와 순환적 최적우선탐색을 이용하여 사고 발생 시 단지 정전의 복구뿐만 아니라 부하의 균등화까지도 함께 수행되는 효율적인 정전복구 알고리즘을 제시한다. 제시되는 알고리즘은 건전피더들이 고장 발생 직후 계통으로 공급하여야 할 부하의 총량을 규정하는 함수로부터 각 피더들이 공급하여야 할 목표치를 제안하고 또한 지수의 목적 값을 만족하는 스위칭을 찾기 위하여 순환적 최적우선 탐색법을 이용한다. 본 논문에서는 제시한 알고리즘을 실제로 서울의 K지사에서 윤용하고 있는 108모선에 적용하여 결과를 도출 했으며 그 결과 제안된 알고리즘을 이용할 경우에 적은 탐색 횟수로 정전이 복구됨과 동시에 건전 선로간의 부하가 균등화되었음을 입증하였다.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제8권2호
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• pp.183-194
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• 2002

이기종 워크스테이션 클러스터링은 응용 프로그램의 병렬 처리에 유용하며 비용 측면에서 효과적이다. 이기종 워크스테이션 클러스터링 환경에서 총작업반환시간을 최소화하기 위해서는 부하 균형 시스템이 필요하다. 기존의 부하 균형 방식은 각 워크스테이션의 처리능력에 가중치를 미리 부여하여 작업을 분배하는 정적방식이거나, 각 워크스테이션의 상대적 처리능력을 얻기 위해서 성능 테스트 프로그램을 수행하는 동적 방식이 있다. 수행되는 응용 프로그램과는 관계없는 성능 테스트 프로그램은 계산시간을 소비하고 총작업반환시간을 지연시킨다. 이 논문은 상대적 부하 색인에 기초한 효과적 작업 분배 방식과 작업 이주 방식을 제안하였으며 이기종 워크스테이션 클러스터 환경에서 부하 균형 시스스템을 설계 구현하였다. 이 논문에서 제안한 방식의 총작업반환시간을 실험을 통하여 부하 균형을 하지 않은 라운드 로빈 방식의 총작업반환시간과 성능 테스트 프로그램에 의한 부하 균형 방식의 총작업반환시간과 비교하였다. 실험 결과는 비교한 방식보다 제안 방식의 결과가 우수함을 보였다.

• Journal of Power Electronics
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• 제17권1호
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• pp.222-231
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• 2017

In this paper, a new architecture for a cost-effective power conditioning systems (PCS) using a single-sourced asymmetric cascaded H-bridge multilevel inverter (MLI) for photovoltaic (PV) applications is proposed. The asymmetric MLI topology has a reduced number of parts compared to the symmetrical type for the same number of voltage level. However, the modulation index threshold related to the drop in the number of levels of the inverter output is higher than that of the symmetrical MLI. This problem results in a modulation index limitation which is relatively higher than that of the symmetrical MLI. Hence, an extra voltage pre-regulator becomes a necessary component in the PCS under a wide operating bias variation. In addition to pre-stage voltage regulation for the constant MLI dc-links, another auxiliary pre-regulator should provide isolation and voltage balance among the multiple H-bridge cells in the asymmetrical MLI as well as the symmetrical ones. The proposed PCS uses a single-ended DC-DC converter topology with a coupled inductor and charge-pump circuit to satisfy all of the aforementioned requirements. Since the proposed integrated-type voltage pre-regulator circuit uses only a single MOSFET switch and a single magnetic component, the size and cost of the PCS is an optimal trade-off. In addition, the voltage balance between the separate H-bridge cells is automatically maintained by the number of turns in the coupled inductor transformer regardless of the duty cycle, which eliminates the need for an extra voltage regulator for the auxiliary H-bridge in MLIs. The voltage balance is also maintained under the discontinuous conduction mode (DCM). Thus, the PCS is also operational during light load conditions. The proposed architecture can apply the module-integrated converter (MIC) concept to perform distributed MPPT. The proposed architecture is analyzed and verified for a 7-level asymmetric MLI, using simulation results and a hardware implementation.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.1019-1020
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• 2006

The proposed algorithm consists of two parts. One is to set up a decision tree to represent the various switching operations available. Another is to identify the most effective the set of switches using proposed search technique and a feeder load balance index. Test results on the KEPCO's 108 bus distribution system show that the performance is efficient and robust

• 대한기계학회논문집B
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• 제33권5호
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• pp.358-364
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• 2009

This paper is to investigate the influence of driving patterns of slow and high speed vehicles on the performance of continuously regenerating diesel particulate filter(DPF) system matched with operating conditions in field application. The DPF performance test for field application was carried out for two identical DPFs installed to slow and high speed vehicles. A slow speed vehicle was selected among local buses which have driving patterns to repeat running and stop frequently, while a high speed vehicle was prepared to have long route of high speed over 60km/h like inter-city buses. In this test, the regeneration performance on the DPF of slow speed vehicle deteriorated because of high soot load index(SLI) in spite of same balance point temperature(BPT) distribution for high speed vehicle. The DPF of slow speed vehicle melted in the end because the rapid increase of back pressure caused high temperature over $1200^{\circ}C$ in the ceramic wall of DPF. The PM components like ash collected to the filter in the DPF were analyzed in order to investigate the cause of the defect and provide an operation performance of DPF system. In the result of the analysis, high levels of lubrication oil ash(Ca, Mg, P, Zn) were detected.