• Proceedings of the KIEE Conference
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• 2006.07b
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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.

• Journal of the Institute of Convergence Signal Processing
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• v.20 no.2
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• pp.111-117
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• 2019

We investigated the variations in the magnetic-field distribution and power transmission efficiency, resulting from changes in the relative positions of the transmitting and receiving coils, for electromagnetic-induction-type wireless power transmission using an elliptical receive coil. Results of simulations using a high-frequency structure simulator were compared to actual measurement results. The simulations showed that the transmission efficiency could be maintained relatively stable even if the alignment between the transmitting and receiving coils was changed to some extent. When the centre of the receiving coil was perfectly aligned with the centre of the transmitting coil, the transmission efficiency was the maximum; however, the degree of decrease in the transmission efficiency was small even if the centre of the receiving coil moved by ± 10mm from the centre of the transmitting coil. Therefore, it is expected that the performance of the wireless power transmission system will not be degraded significantly even if perfect alignment is not maintained. The results suggested a standardized application method of wireless transmission in the utilization of wireless power for implantable sensors.

• The Journal of the Korea Contents Association
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• v.15 no.5
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• pp.168-178
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• 2015

Besides the imposition of taxes and mandatory actions, why in a special rules needed in the contract between state and civilians. The contract between the state and civilian are unlike with civilian's contract in the comparable effect, even if the effect of the agreement and the parties bear the structural nature of the self-other agreement between private economic actors and there are a variety of different specificity. In other words, the agents of the contract with the state government for control of opportunistic behavior are very specific rules exist. Through this, even if it is the relationship between state and non-mandatory private realms of the contract, even if the area forced me to the fact that the difference can be confirmed. Representative of the government of the country to understand the delegate decisions and judgments and other opportunistic behavior always seem to exist on the possibility of such devices for the pre-control needed.

• Animal Bioscience
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• v.35 no.1
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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.

• Journal of the Korean Professional Engineers Association
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• v.45 no.1
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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.

• Communications of the Korean Mathematical Society
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• v.13 no.1
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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.

• Journal of the Chungcheong Mathematical Society
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• v.36 no.3
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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.

• Bulletin of the Korean Mathematical Society
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• v.57 no.2
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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.

• Proceedings of the KSR Conference
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• 2007.11a
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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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• v.20 no.5
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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.