• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 전력전자학술대회 논문집
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• pp.230-231
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• 2012

This paper describes a gate driver that operates numerous semiconductor switch in the solide-state pulsed power modulator. the proposed gate driver is designed to receive both the isolated drive-power and the on/off pulse signals through the transformer. Moreover, the IGBT-switch can be quickly turned off by adding protection circuit. Therefore it protects the IGBT-switch from the arc condition that frequently occurs in high-voltage pulse application. To comprehend operating characteristic of each IGBT-switch in pulse output condition, the device consisting of a high efficiency soft-switching capacitor charger and two series stacking IGBT-switch is developed. Finally, the relability of the proposed gate driver and the device for its test are proved through PSpice simulation and experiments.

• 한국정보과학회논문지:정보통신
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• 제31권2호
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• pp.233-241
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• 2004

본 논문에서는 MPLS(Multiprotocol Label Switching) 망에서 패킷 손실 없이 장애를 복구하는 기존의 fast rerouting 기법 적용 시 ingress 노드 버퍼에서 발생하는 누적 지연 문제를 해결하는 방안을 제안한다. 제안된 기법은 사용자 트래픽을 복구하기 위해서 사전에 설정된 대체 LSP(Label Switched Path)와 각 노드에 설치된 버퍼를 사용한다. Ingress 노드에서 발생하는 버퍼 지연 문제를 해결하기 위해서 본 논문에서는 두 가지 해결방안을 제안하였다. 첫 번째 방안은 대체 LSP가 보호되는 working LSP보다 일정기간동안 큰 대역폭을 가지도록 제어하는 것이다. 장애가 복구된 후, 대체 LSP에 설정된 대역폭은 working LSP와 동일하도록 재조정된다. 두 번째 방안은 세그먼트 기반의 장애복구 기법을 적용하여 보호되는 working LSP의 길이를 줄이는 것이다. 본 논문에서 제안한 방안들은 장애 복구 후 ingress 노드에서 버퍼 지연 문제가 발생하지 않으며, ingress 노드에서 필요로 하는 버퍼의 크기도 기존 방안보다 작다는 장점을 가진다.

• Nutrition Research and Practice
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• 제10권6호
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• pp.623-628
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• 2016

BACKGROUND/OBJECTIVES: Obesity-induced steatohepatitis accompanied by activated hepatic macrophages/Kupffer cells facilitates the progression of hepatic fibrinogenesis and exacerbates metabolic derangements such as insulin resistance. Heme oxyganase-1 (HO-1) modulates tissue macrophage phenotypes and thus is implicated in protection against inflammatory diseases. Here, we show that the flavonoid quercetin reduces obesity-induced hepatic inflammation by inducing HO-1, which promotes hepatic macrophage polarization in favor of the M2 phenotype. MATERIALS/METHODS: Male C57BL/6 mice were fed a regular diet (RD), high-fat diet (HFD), or HFD supplemented with quercetin (HF+Que, 0.5g/kg diet) for nine weeks. Inflammatory cytokines and macrophage markers were measured by ELISA and RT-PCR, respectively. HO-1 protein was measured by Western blotting. RESULTS: Quercetin supplementation decreased levels of inflammatory cytokines ($TNF{\alpha}$, IL-6) and increased that of the anti-inflammatory cytokine (IL-10) in the livers of HFD-fed mice. This was accompanied by upregulation of M2 macrophage marker genes (Arg-1, Mrc1) and downregulation of M1 macrophage marker genes ($TNF{\alpha}$, NOS2). In co-cultures of lipid-laden hepatocytes and macrophages, treatment with quercetin induced HO-1 in the macrophages, markedly suppressed expression of M1 macrophage marker genes, and reduced release of MCP-1. Moreover, these effects of quercetin were blunted by an HO-1 inhibitor and deficiency of nuclear factor E2-related factor 2 (Nrf2) in macrophages. CONCLUSIONS: Quercetin reduces obesity-induced hepatic inflammation by promoting macrophage phenotype switching. The beneficial effect of quercetin is associated with Nrf2-mediated HO-1 induction. Quercetin may be a useful dietary factor for protecting against obesity-induced steatohepatitis.

• Journal of Power Electronics
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• 제17권6호
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• pp.1535-1544
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• 2017

Advances in FPGA technology have enabled fast real-time simulation of power converters, filters and loads. FPGA based HIL (Hardware-In-the-Loop) simulators have revolutionized control hardware and software development for power electronics. Common time step sizes in the order of 100ns are sufficient for simulating switching frequency current and voltage ripples. In order to keep the time step as small as possible, ideal switching function models are often used to simulate the phase legs. This often produces inferior results when simulating the discontinuous conduction mode (DCM) and disabled operational states. Therefore, the corresponding measurement and protection units cannot be tested properly. This paper describes a new solution for this problem utilizing a discrete-time PI controller. The PI controller simulates the proper DC and low frequency AC components of the phase leg voltage during disabled operation. It also retains the advantage of fast real-time execution of switch-based models when an accurate simulation of high frequency junction capacitor oscillations is not necessary.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 B
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• pp.1211-1214
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• 1992

본 논문에서 제안한 Fara DS Series의 AC SERVO (DC BRUSHLESS) MOTOR 제어기는 ROBOT, CNC, 각종 공작기계및 FA기기에서 MOTOR를 구동 원으로 사용하는데 사용되는 제품이다. AC SERVO MOTOR DRIVE의 Inverter에 IGBT(Insulated Gate Bipoler Transistor)를 사용하여 Switching 주파수를 높임으로써 Motor를 가변속 제어할때 발생하는 소음 및 진동을 극소화 하였다. 또한 일반적으로 Motor 속도제어를 급감속으로 제어할때 Servo Motor의 비선형 특성으로 인한 전류위상을 보상하여 모든 동작구간에서 최적의 상태의 제어가 되도록 개발하였다. 그리고 다양한 User Option 기능을 내장하여 User가 원하는 제어대상에 효과적으로 적용할 수 있도록 하였다. 아울러 MOTOR 제어기에 내장 된 다수의 보호기능을 통해서 Motor운전중 발생하는 이상상태에 대해 제어기를 보호할 수 있도록 하였다. 제안한 제어기는 부하변동, 전압변동, 온습도변동에 대해 속도변동율을 최소화 함으로써 ROBOT, CNC등 FA분야에서 폭넓게 이용할수 있다.

• KIEE International Transactions on Power Engineering
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• 제5A권4호
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• pp.357-365
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• 2005

This research investigates the influences of distributed generations (DG), which are interconnected to the bus by the dedicated lines, on the overcurrent relays (OCR) of the neighboring distribution feeders and also proposes a novel method to reduce the negative effects on the feeder protection. Due to the grid connected DG, the entire short-circuit capacity of the distribution networks increases, which may raise the current of the distribution feeder during normal operations as well as fault conditions. In particular, during the switching period for loop operation, the current level of the distribution feeder can be larger than the pickup value for the fault of the feeder's OCR, thereby causing the OCR to perform a mal-operation. This paper proposes the adaptive setting algorithm for the OCR of the distribution feeders having the neighboring dedicated feeders for the DG to prevent the mal-operations of the OCR under normal conditions. The proposed method changes the pickup value of the OCR by adapting the power output of the DG monitored at the relaying point in the distribution network. We tested the proposed method with the actual distribution network model of the Hoenggye substation at the Korea Electric Power Co., which is composed of five feeders supplying the power to network loads and two dedicated feeders for the wind turbine generators. The simulation results demonstrate that the proposed adaptive protection method could enhance the conventional OCR of the distribution feeders with the neighboring dedicated lines for the DG.

• 한국전기전자재료학회논문지
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• 제25권5호
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• pp.334-339
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• 2012

A study on electrical and electronic equipment will occur in the atmosphere, which is essential to cut the power to prevent the waste of power by power measurement technology development and to develop the technology to do this operation is the main core of standby power to detect and block it and return the configured for software and hardware, while the actual construction to ensure stability through field testing and debugging of problems improved accordingly, as well as ease of installation and so it could be done while the test. In addition, in terms of basic hardware switching of standby power when blocking, reducing stress and ensure stable operation and circuit design, power off and back to ensure stable operation even when a protection circuit is applied.

• 전기학회논문지
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• 제67권11호
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• pp.1512-1516
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• 2018

The power system and control system constantly reveals surge voltage such as switching surge of lighting devices and power conversion devices, operating and stops surge of rotating devices, charge & discharge surge, opening & closing surge of circuit breakers and the like. Such a surge voltages can cause damage or malfunction of the element such as CPU, Memory, semiconductor etc. In the industry, in order to protect the system from the surge voltage, a surge protector with low discharge starting voltage, fast response time, and low capacitance is required, and technical development research for that is ongoing. In this paper, in order to solve the problem of the existing GDT discharge tube not discharging from the transient voltage which is higher than the commercial voltage and lower than the discharge voltage of the discharge element, we have developed a discharge element having the control electrode & control circuit. The discharge element having the control electrode and the control circuit can control the discharge voltage according to the needs of the consumer and can satisfy the requirement of the discharge element and the technology of the surge protector downsizing technology and the surge protection technology. It is judged to be effective for development.

• 한국콘텐츠학회논문지
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• 제17권1호
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• pp.129-136
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• 2017

본 연구는 사회복지사의 이직 의사 영향 요인을 파악하여 제도적인 대책방안을 모색하는데 목적이 있다. 원 자료는 한국보건사회연구원의 2014년도 사회복지시설 종사자 보수수준 및 근로여건 실태조사 자료를 활용하였다. 분석결과, 사회복지사 중 33.7%가 이직 의사가 있는 것으로 나타났으며, 사회복지사는 여성보다 남성이, 나이가 적을수록, 학력이 높을수록, 직업만족도가 낮을수록, 보수가 낮을수록, 고용형태가 정규직에 비해 비정규직일 때 이직 가능성이 높았다. 이러한 결과는 취약계층에 대한 지원을 강화하기 위해 사회복지사에 대한 전문직의 처우가 개선되어야 함을 의미한다. 제도적 발전으로 직무 또는 자격수당 신설과 지역별로 인접한 사회복지기관, 시설의 통합화를 통한 순환 직급체계의 정비를 제안하였다.

• 중소기업융합학회논문지
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• 제6권2호
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• pp.31-36
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• 2016

Sniffing은 공격자가 암호화 되지 않은 패킷들을 수집하여 순서대로 재조합 하고난 후 공격 대상의 개인정보, 계좌정보 등 중요 정보를 유출하기 위한 수동적 형태의 공격이다. Sniffing 공격으로 인해 패킷들이 유출되는 것을 방지하기 위해 기존의 방법들을 살펴보고, 효율적인 방어대책을 제시하였다. Sniffing공격은 공격 대상의 근거리 네트워크를 Promiscuous Mode을 이용해 조작한 후 필터링을 해제하고 패킷을 훔치는 방식으로 작동한다. 공격의 형태로 Switch Jamming, Port mirroring, ARP Redirect, ICMP Redirect 공격 등이 있다. 제안하는 공격 대응 방법으로는 SSL을 통한 패킷의 암호화, 스위칭 환경의 네트워크 구성 관리, DNS를 이용하는 방법과 decoy방법을 이용하면 안전한 통신이 가능할 것으로 기대하며, 더 효율적이며 안전한 ICT 연구에 기여한다. 향후 프로토타입 프로토콜을 통하여 효율성을 증명하는 것은 향후 연구로 진행할 예정이다.