• 전기학회논문지P
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• 제58권1호
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• pp.1-8
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• 2009

Recently, application of non-linear load is gradually increased. Non-linear load produces harmonic components of current during the energy conversion transition. Passive filter is used for reducing of harmonics in the user power systems. This filter, which is composed of capacitor and reactor, frequently get out of order by electrical stress. There are voltage and current increase when capacitor and reactor are applied in the user's filter systems. If increased voltage and current is above stipulated values, they have severely an influences on the life of capacitor and reactor. This paper describes that the voltage and current of capacitor used for filter is within the limits of allowable values, but reactor is beyond the limits and reveals spike voltage. Therefore this phenomenon brings about premature fault of reactor and capacitor.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1999년도 전력전자학술대회 논문집
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• pp.295-298
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• 1999

In this paper, the diode bridge-type ZVT(Zero-Voltage Transition) inverter is proposed. It consists of one auxiliary switch, three resonant inductors and six blocking diodes. So, the advantage of the proposed topology is the reduction of the auxiliary switch. The topology of the proposed ZVT inverter is analyzed with a description of the control conditions based on the load current. Therefore, this paper two control algorithms were discussed. A variable resonant pattern control algorithm by using load current feedback and a resonant period control algorithm by using resonant inductor current feedback is proposed in order to achieve the ZVT switching condition in full control range and the reducing current spike main switches cause by reverse recovery problem.

• 한국작물학회지
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• 제58권3호
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• pp.239-252
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• 2013

국산밀을 재배하는 전국 175농가를 대상으로 2년 동안 농업형질과 원맥 특성을 조사 한 결과, 간장, 수장, 경수와 이형주율은 년차간 차이를 나타내었다. 시비량이 많았던 남부지역에서 재배된 밀의 간장이 중북부 지역 보다 길었으며, 추비시기는 간장에 영향이 없었지만, 3월 중순 이후에 늦게 추비를 준 농가의 수장은 다른 농가에 비하여 길었으나 경수는 감소하였다. 추비 횟수는 농업형질에 영향을 미치지 않는 것으로 나타났다. 농업형질과 마찬가지로 원맥 특성도 연차간 변이가 있었으며, 남부지역에서 재배된 밀은 중북부지역에서 재배된 밀에 비하여 천립중이 높았으며, 리터중은 낮았으며, 전라북도는 다른 지역에 비하여 낮은 회분 함량과 높은 단백질 함량을 나타냈으며, 전라남도는 다른 지역에 비하여 높은 회분 함량을 나타내었다. 추비시기가 리터중에는 영향을 주었지만 천립중과 회분 및 단백질 함량에는 영향을 주지 않았으며, 추비 횟수도 원맥 특성에 영향이 없는 것으로 나타났다. 시비량에 따라 간장이 증가하고, 천립중과 단백질 함량이 증가하였으며, 수장과 회분함량은 시비량과 부의 상관을 나타내었다. 단백질 함량은 천립중과 정의 상관을 나타내었지만 회분 함량은 천립중 및 리터중과 부의 상관을 나타내었다. 간장이 증가할수록 천립중은 증가하고 리터중은 감소하였으며, 수장은 천립중과 부의 상관을 나타내었다. 시비량이 간장 및 원맥 특성에 영향을 미치기 때문에 품종별 용도에 맞는 밀 품종을 재배하기 위해서는 적정 시비기술에 대한 농가 지도가 필요하다. 또한, 국산 밀의 생산성 증진과 품질 향상 및 균일성 확보를 위해서는 용도별 가공적성에 적합한 품종에 대한 집단 재배단지를 조성하고 철저한 생산 관리와 체계적인 수확 후 관리 구축에 대한 종합적인 고려가 있어야 할 것이다.

• Journal of Electrical Engineering and Technology
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• 제11권6호
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• pp.1634-1644
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• 2016

In this paper, a current-fed two-inductor bi-directional DC/DC converter using resonance (CF-TIBCR) and its design method are proposed. The CF-TIBCR has characteristics of low current ripple and a high current rating because of two separated inductors. Also, it achieves zero voltage switching for all switches and zero current switching for switches of a low voltage stage by using the resonant tank. Besides, a voltage spike problem in conventional current-fed converters is solved without the need for an additional snubber or clamping circuits. As a result, the CF-TIBCR features high step-up and high efficiency. Since the proposed converter has difficulty achieving the soft-switching condition when the converter requires the low voltage transfer ratio, a method that varies the number of resonant cycles is adopted to extend the output voltage range with satisfying the soft-switching condition. The principles of the operation characteristics are presented with a theoretical analysis, and the proposed converter is verified through results of an experiment using a laboratory prototype.

• Journal of Power Electronics
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• 제16권4호
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• pp.1277-1287
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• 2016

This study proposes a novel isolated high step-up galvanic converter, which is suitable for renewable energy applications and integrates a boost converter, a coupled inductor, a charge pump capacitor cell, and an LC snubber. The proposed converter comprises an input inductor and thus features a continuous input current, which extends the life of the renewable energy chip. Furthermore, the proposed converter can achieve a high voltage gain without an extremely large duty cycle and turn ratio of the coupled inductor by using the charge pump capacitor cell. The leakage inductance energy can be recycled to the output capacitor of the boost converter via the LC snubber and then transferred to the output load. As a result, the voltage spike can be suppressed to a low voltage level. Finally, the basic operating principles and experimental results are provided to verify the effectiveness of the proposed converter.

• 한국운동역학회지
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• 제23권1호
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• pp.45-51
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• 2013

The current study developed the analysis program by employing the Polygon Clipping Algorithm to calculate the open area on the court when players try to spike a ball. The program consists of two kinds of output screen. First, on the main output screen, it is possible to calculate both blocked area by net and blockers, and opened area to avoid the blocked area when players spike the ball. Additionally, the secondary output screen shows the moving path of setter and the location of set. Main output screen indicates hitting points of spiking, blocking, and open area. Also, it is possible to analyze the movement of setter, location of set, and hitting point of attacker. The program was tested by comparing real coordinate value and location coordinate value which is operated on the program. To apply this program in the field, future study needs to develop the program that can calculate three dimensions coordinate fast by tracking the location of players or ball in real time.

• Journal of Korean Neurosurgical Society
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• 제29권9호
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• pp.1161-1170
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• 2000

Objective : The transverse hippocampal slice is one of the most commonly studied in vitro models of mammalian brain physiology. However, despite its broad usage, there has been no standardization of slice preparation techniques or recording condition. It is well known that variations in recording conditions can result in profound different effects to neuronal responses. Evoked field potentials, recorded extracellularly, were used to investigate the effects of variations in hippocampal slice preparation protocol on hypoxia responses of CA1 neurones. Material & Methods : Before hypoxic injury, hippocampal slices were incubated for 4 hours. During incubation period, the slices were placed in a incubation chamber($21^{\circ}C$) for recovery from preparation injury and then transferred to recording chamber($34^{\circ}C$) for more recovery and baseline electric recording with current stimulation(0.1Hz). Various time periods in incubation chamber and recording chamber were applied to each experimental group(group 1=60min : 180min, group 2=90min : 150min, group 3=180min : 60min, time in incubation chamber : time in recording chamber) before 10 min hypoxia produced by replacing 95% $O_2$+5% $CO_2$ mixed gas to 95% $N_2$+5% $CO_2$ gas. Calcium, Magnesium ions and several drugs effecting on glutamate receptor also were studied. Recoveries from hypoxic injury of hippocampal slices were estimated by percent recovery of population spike(PS). Statistic analysis of study were performed using paired t-test. Results : The percent recovery of PS after 10min hypoxia was considerably enhanced by increasing the period of current stimulation during incubation period before hypoxic injury. Temperature effect on the result of this experiment was also studied(group 4) but the result from this showed no statistic significance. Low magnesium ion concentration of artificial CSF(Mg-free aCSF) during incubation period enhanced the recovery of PS but low calcium (calcium-free) and high magnesium ion concentration(2mM) reduced it after hypoxic injury. L-glutamate($100{\mu}M$) and AP-5($50{\mu}M$) had no effect on the recovery of PS but CNQX($10{\mu}M$) in artificial CSF during incubation period markedly enhanced the recovery of PS. Co-treatment of AP-5($50{\mu}M$), CNQX($10{\mu}M$) and high magnesium concentration(2mM) enhanced recovery of PS in immediate following period of hypoxic injury but the effect of cotreatment after then decayed rapidly and lost statistic significance. Conclusions : Judging from above results, the condition of baseline recording is important in observing the recovery of population spike after hypoxia, and the time and the condition should be controled more strictly to obtain reliable results.

• 대한물리치료과학회지
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• 제16권4호
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• pp.29-37
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• 2009

Background: The purpose of this study was influence of change of electrical stimulation time on body regions affects on electrical current threshold. Methods: The present study is to examine the effect of silver spike point (SSP) electrical stimulation (1Hz), transcutaneous electrical nerve stimulation (TENS, 100Hz), and interferential current therapy (ICT, 50Hz) from the low back and scapulodorsal and knee joint regions on stimulation-induced current thresholds from the elderly (over sixty) people (male:72, female:91) in senior welfare center. Result: The low back region, but not scapulodorsal and knee joint region, significantly increased the TENS and ICT, but not SSP, electrical stimulation, significantly increased the time-dependent current thresholds in elderly patients. Conclusion: Therefore, these results, in part, suggest that the TENS and ICT were shown to be a more adaptable method of stimulation, and that needed of the development of senile specialized physical therapy and the utilization of senior leisure facilities such as senior welfare center the others.

• Journal of Electrical Engineering and Technology
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• 제6권2호
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• pp.239-244
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• 2011

Industrial power distribution system includes many kinds of non-linear loads, which produce the harmonics during energy conversion transition. The single-tuned passive filter is widely used to absorb the harmonics and attenuate its undesirable effect in the distribution system. However, the passive filter might be severely stressed, and sometimes even damaged, due to the absorption of harmonics. There is voltage rise on the capacitor when the single-turned harmonic filter is applied. When the capacitor voltage rose above the allowable limit, the expected life of the capacitor will considerably deteriorate. On the other hand, the reactor can experience the spike voltage even if the voltage and current of the capacitor are within the allowable limit, and this accumulated voltage stress of the reactor causes its premature fault. In this paper, we analyzed and compared the harmonic voltage and current of the reactor and capacitor in a single-tuned harmonic filter through the EMTP software and verified them with the experimental results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1989년도 하계종합학술대회 논문집
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• pp.16-20
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• 1989

In this paper, we describe the optimal driving method and magnetic flux distribution of permanent magnet which enhance torque characteristics in small-sized 3-phase brushless DC motors. The disadvantages of conventional $120^{\circ}$ constant current drive method are torque ripple, switching noise and spike voltage due to the inductance of stator coil. This shortcommings can be avoided by the switching slew-rate of driving current which is called linear voltage driving method. The aim of this study is to analyze linear voltage driving method quantatively and to determine optimal drive current waveform through computer simulation. The selection of commutation angle and slew rate of a new driving current at switching instants makes torque ripple index minimize and average torque maximize. And the validity of this new driving method was assured by Fourier analysis. Considering two dimensional nonlinear magnetic flux distribution on the permanent magnet, we suggest optimal flux distribution according to the presented driving method which improves torque characteristics.