• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.1159-1160
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• 2006

As the grid-connected photovoltaic power conditioning systems (PVPCS) are installed in many residential areas, this has raised potential problems of network protection on electrical power system. One of the numerous problems is an Island phenomenon. There has been an argument that because the probability of islanding is extremely low it may be a non-issue in practice. However, there are three counter-arguments: First, the low probability of islanding is based on the assumption of 100% power matching between the PVPCS and the islanded local loads. In fact, an island can be easily formed even without 100% power matching (the power mismatch could be up to 30% if only traditional protections are used, e.g. under/over voltage/frequency). The 30% power-mismatch condition will drastically increase the islanding probability. Second, even with a larger power mismatch, the time for voltage or frequency to deviate sufficient to cause a trip, plus the time required to execute the trip (particularly if conventional switchgear is required to operate), can easily be greater than the typical re-close time on the distribution circuit. And, third, the low-probability argument is based on the study of PVPCS. Especially, if the output power of PVPCS equals to power consumption of local loads, it is very difficult for the PVPCS to sustain the voltage and frequency in an island. Unintentional islanding of PVPCS may result in power-quality issues, interference to grid-protection devices, equipment damage, and even personnel safety hazards. So the verification of anti-islanding performance is strongly needed. In this paper, the authors propose the improved RPV method through considering power quality and anti-islanding capacity of grid-connected three-phase PVPCS in IEEE Std 1547 ("Standard for Interconnecting Distributed Resources to Electric Power Systems"). And the simulation and experimental results are verified.

• 융합신호처리학회논문지
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• 제20권2호
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• pp.111-117
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• 2019

전자기 유도형 무선전력전송에서는 송신 코일과 수신 코일의 상대적 위치에 따른 자기장 분포와 동력 전달 효율이 매우 중요하다. 본 연구는 ECG 센서를 사용한 HFSS 시뮬레이션 결과를 실제 측정 결과와 비교하였다. 시뮬레이션 결과 송신 코일과 수신 코일 간의 정렬이 어느 정도 변경 되더라도 전송효율은 비교적 안정적으로 유지 될 수 있음이 나타났다. 수신 코일의 중심이 송신 코일의 중심과 완벽하게 일치하면 전송효율이 최대가 되며, 수신 코일의 중심이 송신 코일의 중심으로부터 ± 10mm 내의 이동은 전송효율의 감소가 크지 않음을 확인 하였으며, 무선 전력 전송 시스템의 성능이 크게 저하되지 않는 것으로 확인 되었다. 본 결과는 이식형 센서를 위한 무선 전력의 활용에서 무선 전송의 표준화 된 적용 방법을 제안한다. 이를 통해 이식형 임플란트의 개발에 있어 무선전력전송에 대한 기준을 제시하고, 관련 디바이스의 개발에 적용 할 수 있을 것으로 판단된다.

• 한국콘텐츠학회논문지
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• 제15권5호
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• pp.168-178
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• 2015

규제의 적용이나 조세의 부과와 같은 강제성을 수반하는 행위가 아닌 국가와의 대등한 관계에서 이루어지는 계약에서 왜 이런 특별한 규칙이 필요한 것일까? 규칙은 사인 간의 계약을 다루는 규칙에 비해 어떤 차이가 있으며 그 차이는 무엇 때문에 발생하는 것일까? 국가와의 계약은 사인 간의 계약과는 달리 대등한 당사자 사이의 효력을 갖는 것이라 하더라도, 계약당사자와 계약의 효력부담자가 다른 구조적 성격으로 인해 민간경제 주체끼리의 계약과는 다른 다양한 특이성이 존재한다. 즉 국가와의 계약에서는 대리인인 정부의 기회주의적 행위를 통제하기 위한 규칙들이 매우 구체적으로 사전적으로 존재하고 있는 것이다. 이를 통해, 국가와의 관계는 그것이 설령 강행성의 영역이 아닌 사적계약의 영역이라 하더라도 차이가 날 수밖에 없다는 사실을 확인 할 수 있다. 대리인 정부는 위임자인 국가의 이해와 다른 판단과 결정을 내리는 기회주의적 행위를 보일 가능성이 늘 존재하기에 이에 대한 사전통제 장치가 필요하기 때문이다.

• Animal Bioscience
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• 제35권1호
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• pp.105-114
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• 2022

Objective: This work was carried out to evaluate the effect of pasture (PA) feeding on buffalo meat quality compared with buffaloes reared intensively with the use of corn silage as a forage base or alternatively with polyphite meadow hay (PH). Methods: Thirty Mediterranean bull buffaloes were distributed into three experimental diet groups: maize silage (MS), PH, and PA. The animals were slaughtered at a live weight of 250 kg, and carcass and meat quality were evaluated. After 7 days of ageing, physical and chemical parameters of longissimus thoracis muscle were determined. To evaluate lipid oxidation the thiobarbituric acid reactive substances was tested at 7 and 14 days, and also the fatty acid profile was recorded by gas chromatography. Results: The PA group, even if it showed carcass parameters lower than those of the silage maize group, reported a good meat percentage (60.59% vs 58.46%, respectively) and lower fat percentage (p<0.001). PA-fed animals showed meat redness, and even if only on raw meat, shear force was higher than the others. Low values of conjugate linoleic acid, polyunsaturated fatty acids, and n-3 were reported in the silage maize group. Principal component analysis (PCA) clearly showed the influence of different diets on meat quality, and PCA1 and PCA2 explained 82% of the variability. Conclusion: Buffaloes reared on PA had meat with high nutritional value even if they showed poor carcass performance compared to the animals fed on MS. Buffaloes fed on polyphite hay were in an intermediate position, similar to grazing animals, according to the same nutritional determinations.

• 기술사
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• 제45권1호
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• pp.42-44
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• 2012

Recently human beings are experiencing fatal matters of environmental harm from enormous demolished concrete, even though waste concrete can get much more market value if recycled. The problem is that demolished concrete can not find the place where it can be used more economically and efficiently, but eventually can be spent worthlessly for landfill or road basement. Up to now, we can barely find the right place matching for structural performance in construction site with recycled concrete, even more, can not find another place to recycle this tremendous waste concrete. in addition it needs recycling information system between demanders and suppliers managed by government and other.

• 대한수학회논문집
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• 제13권1호
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• pp.61-72
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• 1998

It has been known that if T and S are even Kakutani equivalent, then there exists U such that T and U are $\alpha$-equivalent and S and U are $\beta$-equivalent where $\alpha$ and $\beta$ are irrationally related. In this paper we give a complete discrete proof of this theorem without using R-actions.

• 충청수학회지
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• 제36권3호
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• pp.181-194
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• 2023

Let GR(2^m, r) be a Galois ring with even characteristic. We are interested in the existence of MDS(Maximum Distance Separable) self-dual codes over GR(2^m, r). In this paper, we prove that there exists an MDS self-dual code over GR(2^m, r) with parameters [n, n/2, n/2 + 1] if (n - 1) | (2^r - 1) and 8 | n.

• 대한수학회보
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• 제57권2호
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• pp.371-381
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• 2020

A ring R is called right pure-injective if it is injective with respect to pure exact sequences. According to a well known result of L. Melkersson, every commutative Artinian ring is pure-injective, but the converse is not true, even if R is a commutative Noetherian local ring. In this paper, a series of conditions under which right pure-injective rings are either right Artinian rings or quasi-Frobenius rings are given. Also, some of our results extend previously known results for quasi-Frobenius rings.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.696-702
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• 2007

The purpose of this paper is to analyze cost-effectiveness of a train simulators. The cost-effectiveness of training program is assessed by multiplying transfer effectiveness ration(TER) by training cost ration(TCR). If their product is less than one, the program is not cost effective. Even if a program is not cost effective, however, safety considerations may be important to consider.

• Journal of Mechanical Science and Technology
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• 제20권5호
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• pp.643-651
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• 2006

The theory for a novel fault-tolerant 4-active-pole homopolar magnetic bearing is developed. If any one coil of the four coils in the bearing actuator fail, the remaining three coil currents change via an optimal distribution matrix such that the same opposing pole, C-core type, control fluxes as those of the un-failed bearing are produced. The hompolar magnetic bearing thus provides unaltered magnetic forces without any loss of the bearing load capacity even if any one coil suddenly fails. Numerical examples are provided to illustrate the novel fault-tolerant, 4-active pole homopolar magnetic bearings.