• Journal of Power Electronics
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• 제19권1호
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• pp.278-287
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• 2019

In this study, a zero-crossing spike current issue in a totem-pole bridgeless power factor correction (PFC) converter is comprehensively investigated for the first time. Spike current occurs when input voltage crosses zero, becomes a noise source, and causes severe common mode emission issues. A generation mechanism for electromagnetic interference (EMI) is presented to investigate the EMI problem caused by zero-crossing issue, and a noise spectrum due to this issue is predicted by a theoretical analysis based on the Fourier coefficient of an approximate spike current waveform. Furthermore, a noise reduction method is proposed and then improved to reduce the spike current. Experimental measurements are implemented on a GaN-based totem-pole bridgeless PFC converter, and the spike current can be effectively suppressed through the proposed method. Furthermore, the noise spectrums measured without and with the reduced zero-crossing spike current are compared. Experimental results validate the analysis of the noise spectrum caused by the zero-crossing spike current issue.

• 복식
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• 제38권
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• pp.359-368
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• 1998

Bee-chy is the name of a bird as well as of a jade. This study is about Bee-chy-mo which only Royalty had used in the Shilla period. Bee-chy is a bird which belongs to Alcedinid-ae, and is called as“Ruddy Kingfish”,“Black-capped Kignfish”,“Common Kingfish”. It is distributed all over the world only except for the South Pole. The colors of Black-capped Kingfish and Common Kingfish's feathers are bright green or deep blue. The feather was so beautiful that people already used it in ancient China. Feather garments as well as decorations with Kingfish feathers were popularized in Tang period. Bee-chy-mo was used by attaching Kingfish feathers to decorations or weaving clothes with Kingfish feathers.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.834-839
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• 2007

This paper investigates the distortion of magnetic field of a brushless DC (BLDC) motor due to deformed rubber magnet. Global or local deformation of rubber magnet in the BLDC motor is mathematically modeled by using the Fourier series. Distorted magnetic field is calculated by using the finite element method, and unbalanced magnetic force are calculated by using the Maxwell stress tensor. The first harmonic deformation in the global deformation of rubber magnet generates the first harmonic driving frequency of the unbalanced magnetic force, and the rest harmonic deformations of rubber magnet except the harmonic deformation with multiple of common divisor of pole and slot introduces the driving frequencies with multiple of slot number ${\pm}1$ to the unbalanced magnetic force. However, the harmonic deformation with multiple of common divisor of pole and slot does not generate unbalanced magnetic force due to the rotational symmetry. When the rubber magnet is locally deformed, the unbalanced magnetic force has the first harmonic driving frequency and the driving frequencies with multiples of slot number ${\pm}1$.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 B
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• pp.626-628
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• 1992

GCB(Gas Circuit Breaker) and GIS(Gas Insulated Switchgear) using $SF_6$ are worldwidely applied over 72.5KV classes. It Is known that $SF_6$ gas has the most superior characteristics among the extingushing and insulating media. Our Company has produced GCB and GIS from early 1980's and at present, we are producing 362KV 40KA class which is the highest voltage in our country. According to change KEPCO's standards (ESB standards), our company has redeveloped and tested for all productions type from 1989. During redeveloping, we largely contribute raise reliability of power system, through all the more improvement for performance and quality of manufactures. One of them, we developed 170KV 50KA GCB with common three-pole operating mechanism and sucessfully completed test of KERI under KEPCO presence, at first in our country. Thus, we announce the outline of it.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2015년도 전력전자학술대회 논문집
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• pp.311-312
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• 2015

본 논문에서는 Unipolar PWM 스위칭 (Totem pole) 방법을 사용하는 단상인버터에서 나타나는 common mode noise를 저감시키는 스위칭 방법을 제안한다. 제안하는 방법은 출력전압의 중성점(N)을 입력전압 양단에 항상 고정하도록 스위칭을 하여 Common Mode Noise를 저감했다. 이를 Matlab Simulink를 사용한 모의해석과 실험을 통하여 Noise의 원인과 효과를 입증하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.440-442
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• 2004

The ground resistance of middle scale ground pole was measured by using the 'fall of potential method' suggested by IEEE However, the measured resistance value was lower than the minimum value required To solve this problem. ground pole was set to be used commonly. In this research. ground resistance was measured using the newly suggested method and the results were analyzed to see if they satisfied the domestic regulation The results of this research will be applied to the management works as well as the establishment of new plan.

• 대한두경부종양학회지
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• 제38권1호
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• pp.65-68
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• 2022

Thyroglossal duct cyst (TGDC) is the most common congenital cyst in the neck and usually presents in children. It is most commonly located at the infrahyoid level. However, intrathyroid TGDC in the adult is extremely rare and its pathogenesis remains unclear. Curiously, an intrathyroid TGDC was found on the lateral aspect of the inferior pole of the thyroid gland. Given the unique position of this lesion, and its capacity to stimulate other nodules in the thyroid, it should be differentiated from other lateral neck masses, such as: thymic cysts, branchial cleft cysts, cystic hygroma, lipomas, lymphadenopathies, cervical teratomas, and lymphomas. In this case, a separate cystic mass was found in the right inferior pole of the thyroid gland and extended to the mediastinum. We confirmed it as TGDC by pathology and histological examination.

• Childhood Kidney Diseases
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• 제4권2호
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• pp.170-174
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• 2000

신우요관이행부 폐색에 의한 신생아 편측수신증의 치료가 여전히 논란의 여지가 있는 상황에서 완전 중복요관에 동반한 하극 신우요관이행부의 폐색이 있는 경우 조기에 수술요법으로 치료한 사례가 있어 이를 소개하고자 하였다. 본 증례의 환아들은 산전초음파에서 편측수신증이 있음을 알았고 출생후 정확한 진단과정을 통해 편측 신하극 신우요관이행부 폐색을 동반한 완전 중복요관을 진단받았다. 환아들은 신상극의 신실질은 정상 소견이었지만 신하극의 수신증이 SFU 등급 IV로 심하여 각각 생후 약 1개월과 4개월째 신우요관문합술을 시행받았다. 술후 추적관찰에서 두 환아 모두 합병증없이 회복되었고 환측 신장의 모양 및 기능이 현저히 호전된 결과를 보였다.

• 수산해양교육연구
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• 제12권2호
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• pp.142-151
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• 2000

The studies on the electronic control fuel injection system for a DI diesel engine have done for reducing the exhaust emission and improving fuel consumption. The electronic control fuel injection system is classified into a common rail system, a unit injector system and a high pressure injection system. The characteristics of these systems are largely depends on the operating characteristics of its solenoid that have high speed on-off operation. In order to improve these characteristics of fuel injection system, it is necessary to design the optimal shape of solenoid and select the input method of its power source. It was proposed HELENOID, COLENOID, DISOLE, and Multipole Solenoid in the studies of design for the optimal shape of solenoid. The studies on the energizing method, input method for power of solenoid were dealt with the conventional energizing method, the chopping method and the pre-energizing method. In order to find out the high response characteristics of solenoid, it is necessary to test the performance of optimally designed solenoid with a new energizing method. In this paper, the solenoid of multi-pole type with plat armature and its power control unit to control input current by the chopping method designed, and its response tests were performed according to its energizing conditions. As a result, the maximum input current for solenoid was controlled by the period of first stage exciting current and chopping duty ratio of control stage exciting current, and the fastest "on" time was able to get 0.46ms. The conditions of fastest "on" time was 0.3ms for first stage exciting current, 0.16ms for control exciting current and 75% for chopping duty ratio.

• 한국동물학회지
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• 제20권3호
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• pp.141-147
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• 1977

한국 재래산양 50마리의 신정맥 vinylite를 주입하여 주형표본을 만들어 신정맥의 분포상태를 관찰하여 다음과 같은 결과를 얻었다. 1. 신장의 구역정맥들이 모여서 신정맥지를 이루고, 신정맥은 $2\\sim 3$개의 신정맥지로서 구성되나, 2개의 신정맥지인 경우가 많았다. 2. 신정맥은 전지(Ramus cranialis)와 후지(Ramus caudalis)로 구성되는 경우, 배지(Ramus dorsalis)와 복지(Ramus ventralis)로 구성되는 경우, 전지 $\\codt$ 중지(Ramus medius)후지로 구성되는 경우 그리고 $배지\\cdot 중지 \\cdot 복지$로 구성되는 경우가 있었는데, $배지\\cdot 복지$로 되는 경우가 가장 많았다. 3. 정맥성 구역은 $좌\\cdot 우신$, $배\\cdot 복면$이 각각 $2\\sim 4$개 였으며 3개인 경우가 가장 많았다. 4. 신장의 배면과 복면의 전단, 또는 후단 그리고 $전\\cdot 후양단$에서 공통구역을 형성하는 경우도 있었다. 5. 신극정맥의 출현은 없었다. 6. 신정맥의 주행과 분포상태는 신동맥과는 현저히 달랐다.