• Title/Summary/Keyword: DC23

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DC Electric Field Characteristics considering Thermal Effect for HVDC Slip-on Type Outdoor Termination (HVDC 슬립 온형 기중 종단접속함에 대한 열 영향 반영 DC 전계 특성 평가)

  • Kwon, Ik-Soo;Hwang, Jae-Sang;Koo, Jae-Hong;Sakamoto, Kuniaki;Lee, Bang-Wook
    • KEPCO Journal on Electric Power and Energy
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    • v.1 no.1
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    • pp.39-46
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    • 2015
  • A outdoor termination installed at the outdoor substation is required to connect undergroud cables and overhead transmission lines. The joint box for AC transmission system is already developed and widely used to interconnect overhead and undergroud systems. But the development of the joint box for DC transmission system was only introduced from China and Japan, but theire developemnt staus and core technologies were not fully reported. In order to implement HVDC systems connecting ovehead transmission lines and undergroud cables, a outdoor termination should be developed, but the detailed specifications and information of this device were not reported. It is estimated that the development of the joint box for DC environment has some technical obstacles including insulating materials, electric field mitigation, thermal temperature rise, and space charge accumuations. Among this, the most important one is the DC elctrical insualtion design. Therefore, in order to investigate the DC elctrical insualton design of outdoor termination, the design of AC slip-on type outdoor termination is reffered, and DC electric field analysis performed to verify the possiblity of application of AC joint box into DC joint box. Especially for DC electric field analysis, temperature rise of insualting materials of a joint box was considered, because the conductivity of materials could be changed due to temperature rise. Furthermore, DC electric field analysis considering transinet state, and polarity reversal state were also investigated to verify which state is the most severe condition for the DC joint box. From the simualtion resulsts, it was shown that the value and the position of maximum electric field was obtained comparing AC state, DC state without temperaure rise, and DC state with temperaure rise. And it was confimred that severe DC electric field was observed considing temperaure rise. Finally, in order to reduce DC eletric field intensifation, different configuration of the joint box was applied and it was not possible to obtain satisfactory results. It means that the slight change of configuration of AC joint box was not the suitable soluton for DC joint box. It is essential to establish novel DC insulaton design skills and method for DC joint box to commercialze this product in the near future.

Clinical Factors for the Development of Posttraumatic Hydrocephalus after Decompressive Craniectomy

  • Choi, Il;Park, Hyung-Ki;Chang, Jae-Chil;Cho, Sung-Jin;Choi, Soon-Kwan;Byun, Bark-Jang
    • Journal of Korean Neurosurgical Society
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    • v.43 no.5
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    • pp.227-231
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    • 2008
  • Objective : Earlier reports have revealed that the incidence of posttraumatic hydrocephalus (PTH) is higher among patients who underwent decompressive craniectomy (DC). The aim of this study was to determine the influencing factors for the development of PTH after DC. Methods : A total of 693 head trauma patients admitted in our hospital between March 2004 and May 2007 were reviewed. Among thee, we analyzed 55 patients with severe traumatic brain injury who underwent DC. We excluded patients who had confounding variables. The 33 patients were finally enrolled in the study and data were collected retrospectively for these patients. The patients were divided into two groups: non-hydrocephalus group (Group I) and hydrocephalus group (Group II). Related factors assessed were individual Glasgow Coma Score (GCS), age, sex, radiological findings, type of operation, re-operation and outcome. Results : Of the 693 patients with head trauma, 28 (4.0%) developed PTH. Fifty-five patients underwent DC and 13 (23.6%) developed PTH. Eleven of the 33 study patients (30.3%) who had no confounding factors were diagnosed with PTH. Significant differences in the type of craniectomy and re-operation were found between Group I and II. Conclusion : It is suggested that the size of DC and repeated operation may promote posttraumatic hydrocephalus in severe head trauma patients who underwent DC.

A STUDY ON BONE STRENGTH AND THE DEGREE OF CONVERSION OF DENTIN BONDING AGENTS (수종 상아질 접착제의 결합강도와 중합률에 관한 연구)

  • Kim, Byung-Hyun;Kwon, Hyuk-Choon
    • Restorative Dentistry and Endodontics
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    • v.23 no.1
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    • pp.68-93
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    • 1998
  • The physical properties of polymer are greatly influenced by the extent to which a resin cures. The presence of un reacted monomer can, have a plasticizing effect on the polymer, thereby altering the physical and mechanical properties of dentin bonding agent (DBA). If the DBA does not polymerize sufficiently, it will leave a weak bonding layer and lead to lower bond strength. The purpose of this study was to evaluate the shear bond strengths(SBS) and the degree of conversion (DC) of 4 commercialy avilable dentin bonding systems which are composed of 2 multi-bottle systems [Scotchbond Multi-Purpose (SMP), AeliteBond(AB)] and 2 onebottle systems [SingleBond(SB), One-Step(OS)]. For shear bond strength measurement, labial surfaces of freshly extracted bovine incisors were ground with # 600 grit SiC paper to expose dentin. Four different groups of samples were formed, with 10 samples. being made for each of the 4 commercial DBA in each group according to the curing sequences of DBA and overlayer thickness of composites: Group I (standard cure and 1mm thick composites) : The DBA was light cured and the composites of 1mm thickness was applied ; Group II (standard cure and 2mm thick composites) : The DBA was light cured and the composites of 2mm thickness was applied; Group III (simultaneous cure and 1mm thick composites) : The DBA was not light-cured and simultaneously cured with composites of 1mm thickness; Group N (simultaneous cure and 2mm thick composites) : The DBA was. not light-cured and simultaneously cured with composites of 2mm thickness. The SBS was measured immediately after the composites was bonded to the bovine dentin using an Instron machine. The DC of the DBA was examined in a thin film under simulated conditions of the experimental groups according to the curing sequences and overlayer thickness of composites in the SBS test. using a Fourier transform Infrared(FTIR) spectrometer. The following results were obtained from SBS tests and DC measurements 1. In SBS tests, the multi-bottle DBA(SMP, AB) had a generally higher bond strength values than the one bottle DBA(SB, OS). In DC measurements, the one bottle DBA(SB, OS) had a significantly higher DC than the multi-bottle DBA(SMP, AB). 2. In all DBAs except OS, there was no significant difference between the bond strength of group I (standard cure and 1mm thick composites) and that of group III (simultaneous cure and 1mm thick composites). SMP, SB in Group I had a significantly higher DC than those in group III, but AB, OS in group I had a significantly lower DC than those in group III 3. All DBAs in Goup II (standard cure and 2mm thick composites) had significantly higher bond strength and DC than those in Group N (simultaneous cure and 2mm thick composites). 4. In all DBAs, there was no significantly different SBS and DC between Group I and Group II, but all DBAs in Group III had significantly higher SBS and DC than those in Group IV.

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초대석- 조병규 그리곤엔터테인먼트 사장

  • Sin, Jong-Hun
    • Digital Contents
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    • no.1 s.128
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    • pp.22-23
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    • 2004
  • 2003년에 제작된 디지털콘텐츠 가운데 가장 뛰어난 작품에 수여되는 디지털콘텐츠 대상 대통령상에 그리곤엔터테인먼트의‘씰온라인(Seal Online)’이 수상작으로 결정됐다. 씰온라인은 풀 카툰렌더링 기법을 도입한 3D 온라인게임으로, 밝고 명랑한 분위기를 강조해 게이머들이 편안하게 게임을 즐길 수 있도록 하는데 초점을 맞춘 게임이다. 올해 처음으로 대통령상으로 격상된 DC대상을 수상한 그리곤엔터테인먼트의 조병규 사장을 만났다.

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Effect of CQ-amine ratio on the degree of conversion in resin monomers with binary and ternary photoinitiation systems

  • Moon, Ho-Jin;Shin, Dong-Hoon
    • Restorative Dentistry and Endodontics
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    • v.37 no.2
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    • pp.96-103
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    • 2012
  • Objectives: This study evaluated the effect of camphorquinone (CQ)-amine ratio on the C=C double bond conversion of resins with binary and ternary photoinitiation systems. Materials and Methods: Two monomer mixtures (37.5 Bis-GMA/37.5 Bis- EMA/25 TEGDMA) with binary systems (CQ/DMAEMA in weight ratio, group A [0.5/1.0] and B [1.0/0.5]) and four mixtures with ternary system (CQ/OPPI/DMAEMA, group C [0.1/1.0/0.1], D [0.1/1.0/ 0.2], E [0.2/1.0/0.1] and F [0.2/1.0/0.2]) were tested: 1 : 2 or 2 : 1 CQ-amine ratio in binary system, while 1 : 1 ratio was added in ternary system. The monomer mixture was cured for 5, 20, 40, and 300 sec with a Demetron 400 curing unit (Demetron). After each exposure time, degree of conversion (DC) was estimated using Fourier transform infrared (FTIR) spectrophotometer (Nicolet 520, Nicolet Instrument Corp.). The results were analyzed by ANOVA followed by Scheffe test, with p = 0.05 as the level of significance. Results: DC (%) was expressed in the order of curing time (5, 20, 40, and 300 sec). Group A ($14.63{\pm}10.42$, $25.23{\pm}6.32$, $51.62{\pm}2.69$, $68.52{\pm}2.77$); Group B ($4.04{\pm}6.23$, $16.56{\pm}3.38$, $37.95{\pm}2.79$, $64.48{\pm}1.21$); Group C ($16.87{\pm}5.72$, $55.47{\pm}2.75$, $60.83{\pm}2.07$, $68.32{\pm}3.31$); Group D ($23.77{\pm}1.64$, $61.05{\pm}1.82$, $65.13{\pm}2.09$, $71.87{\pm}1.17$); Group E ($28.66{\pm}2.92$, $56.68{\pm}1.33$, $60.66{\pm}1.17$, $68.78{\pm}1.30$); Group F ($39.74{\pm}6.31$, $61.07{\pm}2.58$, $64.22{\pm}2.29$, $69.94{\pm}2.15$). Conclusion: All the monomers with ternary photoinitiation system showed higher DC than the ones with binary system, until 40 sec. Concerning about the effect of CQ-amine ratio on the DC, group A converted into polymer more than group B in binary system. However, there was no significant difference among groups with ternary system, except group C when cured for 5 sec only.

LLC Resonant Converter with Auxiliary Switches Operating Over A Wide Output Voltage Range (넓은 입·출력전압 범위에서 제어 가능한 보조스위치 적용 LLC 공진컨버터)

  • Lee, Ji-Cheol;Kim, Min-Ji;Oh, Jae-Sung;Kim, Eun-Soo;Kook, Yoon-Sang
    • The Transactions of the Korean Institute of Power Electronics
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    • v.23 no.4
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    • pp.256-264
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    • 2018
  • This paper proposes a three-bridge LLC resonant converter with auxiliary switches for a wide output voltage control range. This converter can be controlled in two ways to achieve a wide controllable output voltage control range of $V_o$ to $3V_o$. The first control mechanism is achieved through the pulse width modulation (PM) of the auxiliary switches and primary switching devices, while the second control mechanism is achieved through the frequency modulation (FM) of the primary switching devices that are configured to operate in the full-bridge switching mode when the auxiliary switches are turned off. The feasibility of using the proposed converter is verified by the results of an experiment with a 2kW prototype.

8kW LLC Isolated Converter Design for ESS Battery Charge/Discharge System (ESS 배터리 충방전 시스템을 위한 8kW급 LLC 절연형 컨버터 설계)

  • Kim, Jinwoo;Baek, Seunghoon;Cho, Younghoon;Koo, Tae-Geun
    • The Transactions of the Korean Institute of Power Electronics
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    • v.23 no.3
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    • pp.161-167
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    • 2018
  • In battery-operated systems, an isolated converter is used to interface the utility grid with the system to increase stability when charging and discharging batteries. Systems such as vehicle-to-grids (V2Gs), on-board chargers, and energy storage systems (ESSs) have recently become popular, and the roles of isolated converters have become important considerations in fabricating such devices. A fixed-frequency LLC converter, which is a type of isolated converter, presents the advantages of high efficiency and high power density by performing zero-voltage switching (ZVS) over wide frequency ranges. However, the magnetizing inductance of the LLC converter should be designed to enable ZVS in all switching devices. Therefore, in this study, the operating characteristics of the LLC circuit are analyzed, and an optimal design method for ZVS operation is established. Moreover, an 8 kW LLC high-efficiency and high-power-density resonant converter is designed and tested for ESS application. The LLC converter achieves 98% efficiency at rated power.

Study on the Evaluation Method of Electrical Isolation Property for Hydrogen Fuel Cell Vehicle in Post Crash (수소연료전지자동차의 충돌시 절연성능 평가방법에 관한 고찰)

  • Lee, Kiyeon;Gil, Hyoungjun;Kim, Dongook;Kim, Dongwoo;Kang, Daechul
    • Transactions of the Korean hydrogen and new energy society
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    • v.23 no.6
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    • pp.612-618
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    • 2012
  • In this paper, in order to prevent electric shock of high voltage system of HFCV after crash test, insulation performance measurement methods were studied. Under conditions of in-use, insulation performance tests can be divided into measurement method using the vehicle's own RESS as DC voltage source and measurement method using DC voltage from off-vehicle sources. However, these tests can not be applied after a post-crash because parts of high voltage system cover should be removed, and insulation performance can be influenced during these tests. Therefore, we proposed post-crash insulation performance test methods for preventing electric shock through problem analysis of previous post-crash insulation performance tests. Also, test equipment which can measure voltage absence and total energy was developed. We verified performance of the equipment through experiments with vehicle test.

Split-Capacitor Dual-Active-Bridge Converter (Split-Capacitor Dual-Active-Bridge 컨버터)

  • Kim, Kisu;Park, Siho;Cha, Honnyong;Choi, Byungcho
    • The Transactions of the Korean Institute of Power Electronics
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    • v.23 no.5
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    • pp.352-358
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    • 2018
  • A split-capacitor (SC) dual-active-bridge (DAB) converter is proposed in this study. The DC-link capacitors of input and output are split in the proposed converter. The primary and secondary windings of transformer are connected to the midpoints of the DC-links. Hence, the SC DAB converter can inherently prevent transformer from saturation. Although the switch current stress of the proposed converter is twice that of the conventional DAB converter, the switch voltage stress is reduced by half. Therefore, the proposed converter can reduce switching loss and achieve high efficiency in a high switching frequency. Given the SC structure, the proposed converter can readily be connected to neutral-point-clamped- or half-bridge-type converters. The topology of the proposed converter is presented and the operating principle is analyzed in detail. A 3-kW hardware prototype was built and tested to verify the performance of the proposed converter.

A Study on motion estimator design using DCT DC value (DCT 직류 값을 이용한 움직임 추정기 설계에 관한 연구)

  • Lee, Gwon Cheol;Park, Jong Jin;Jo, Won Gyeong
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.38 no.3
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    • pp.22-22
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    • 2001
  • 정보량이 많은 고화질의 동영상을 실시간으로 전송하기 위하여 압축 알고리즘을 필수적으로 사용하고 있으며, 시간적 중복성을 제거하는 동영상의 압축방법은 움직임 추정 알고리즘을 사용한다. 본 연구에서 설계하고자 하는 움직임 추정기는 블록정합 알고리즘이며, MPEG 부호기에서 사용되는 DCT 연산 결과인 DC 값을 이용하여 화면의 밝기를 판단한다. 움직임 추정기는 휘도 신호 8비트 모두를 사용하지 않고, 화면 밝기에 따른 비트 플레인(bit plane)에서 3비트만 선택하는 비교선택기를 이용한다. 본 연구에서 제안한 비교 선택기는 I-Picture만을 계산한다. I-Picture에 의해 계산된 선택 비트는 I, P와 B Picture의 움직임 추정 연산에 사용함으로서 움직임 추정기의 크기를 줄일 수 있는 구조를 제안하였다. 제안된 움직임 추정기의 고찰을 위하여 실험에 사용된 표준 동영상의 해상도는 352×288이며, DCT 연산의 처리 블록은 8×8이며, 탐색 영역은 23×23이다. 제안된 알고리즘은 C언어로 모델링하였으며, 기존 완전탐색방법과 PSNR을 비교한 결과 사람의 시각으로 거의 구별할 수 없는 작은 차이(0~0.83dB)가 나타남을 알 수 있었다. 본 연구에서 제안한 움직임 추정기의 하드웨어 크기는 기존 구조Ⅰ보다 38.3%, 기존 구조Ⅱ보다 30.7% 줄일 수 있었고, 메모리 크기는 기존 구조Ⅰ,Ⅱ보다 31.3% 줄일 수 있었다.