• 약학회지
• /
• 제27권1호
• /
• pp.21-28
• /
• 1983

Distribution volume (Vd$_{ss}$ ) of a model basic drug, tetraethylammonium bromide (TEA) at a steady-state decreased sinificantly in glycerol and uranium-renal failure rats. Assuming carrier-mediated transport of TEA into tissues, the theoretical $Vd_{ss}$ of TEA decreases in an exponential way as the plasmal concentration of TEA increases. The relationship between $Vd_{ss}$ and plasma concentration of TEA in the experimental renal failure (ERF)-rats was similar. Therefore, the decrease in $Vd_{ss}$ of TEA in the ERF-rats seemed to be due to the saturation of the carrier system that are responsible for the tissue distribution of TEA, by the elevated plasma concentration of TEA in the ERF-rats. ERF was induced to rats with glycerol, folate, salicylate, uranium and gentamicin, respectively..

• 전기학회논문지P
• /
• 제51권3호
• /
• pp.120-125
• /
• 2002

The switching-mode power converter has been widely used because of its features of high efficiency and small weight and size. These features are brought by the ON-OFF operation of semiconductor switching devices. However, this switching operation causes the surge and EMI(Electromagnetic Interference) which deteriorate the reliability of the converter themselves and entire electronic systems. This problem on the surge and noise is one of the most serious difficulties in AC-to-DC converter. In the switching-mode power converter, the output voltage is generally controlled by varying the duty ratio of main switch. When a converter operates in steady state, duty ratio of the converter is kept constant. So the power of switching noise is concentrated in specific frequencies. Generally, to reduce the EMI and improve the immunity of converter system, the switching frequency of converter needs to be properly modulated during a rectified line period instead of being kept constant. Random Pulse Width Modulation (RPWM) is performed by adding a random perturbation to switching instant while output-voltage regulation of converter is performed. RPWM method for reducing conducted EMI in single switch three phase discontinuous conduction mode boost converter is presented. The more white noise is injected, the more conducted EMI is reduced. But output-voltage is not sufficiently regulated. This is the reason why carrier frequency selection topology is proposed. In the case of carrier frequency selection, output-voltage of steady state and transient state is fully regulated. A RPWM control method was proposed in order to smooth the switching noise spectrum and reduce it's level. Experimental results are verified by converter operating at 300V/1kW with 5%~30% white noise input. Spectrum analysis is performed on the Phase current and the CM noise voltage. The former is measured with Current Probe and the latter is achieved with LISN, which are connected to the spectrum analyzer respectively.

• ETRI Journal
• /
• 제31권5호
• /
• pp.489-499
• /
• 2009

This paper focuses on assessment and design of transmission systems for distribution of digital signals over standard Category-7A copper cables at speeds beyond 10 Gbps. The main contribution of this paper is on the technical feasibility and system design for data rates of 40 Gbps and 100 Gbps over copper. Based on capacity analysis and rate optimization algorithms, system parameters are obtained and the design implementation trade-offs are discussed. Our simulation results confirm that with the aid of a decision-feedback equalizer and powerful coding techniques, namely, TCM or LDPC code, 40 Gbps transmission is feasible over 50 m of CAT-7A copper cable. These results also indicate that 100 Gbps transmission can be achieved over 15 m cables.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1996년도 추계학술대회 논문집
• /
• pp.113-116
• /
• 1996

The drain current of the MOSFET in the off state(i.e., Id when Vgs=0V) is undesired but nevertheless important leakage current device parameter in many digital CMOS IC applications (including DRAMs, SRAMs, dynamic logic circuits, and portable systems). The standby power consumed by devices in the off state have added to the total power consumed by the IC, increasing heat dissipation problems in the chip. In this paper, hot-carrier-induced degra- dation and gate-induced-drain-leakage curr- ent under worse case in P-MOSFET\`s have been studied. First of all, the degradation of gate-induced- drain-leakage current due to electron/hole trapping and surface electric field in off state MOSFET\`s which has appeared as an additional constraint in scaling down p-MOSFET\`s. The GIDL current in p-MOSFET\`s was decreased by hot-electron stressing, because the trapped charge were decreased surface-electric-field. But the GIDL current in n-MOS77T\`s under worse case was increased.

• ETRI Journal
• /
• 제29권5호
• /
• pp.596-606
• /
• 2007

It is well known that an OFDM receiver is vulnerable to synchronization errors. Despite fine estimations used in the initial acquisition, there are still residual synchronization errors. Though these errors are very small, they severely degrade the bit error rate (BER) performance. In this paper, we propose a residual error elimination scheme for the digital OFDM baseband receiver aiming to improve the overall BER performance. Three improvements on existing schemes are made: a pilot-aided recursive algorithm for joint estimation of the residual carrier frequency and sampling time offsets; a delay-based timing error correction technique, which smoothly adjusts the incoming data stream without resampling disturbance; and a decision-directed channel gain update algorithm based on recursive least-squares criterion, which offers faster convergence and smaller error than the least-mean-squares algorithms. Simulation results show that the proposed scheme works well in the multipath channel, and its performance is close to that of an OFDM system with perfect synchronization parameters.

• Journal of Power Electronics
• /
• 제12권5호
• /
• pp.739-747
• /
• 2012

This paper applies carrier phase shifted pulse-width modulation (CPS-PWM) to transformerless modular multilevel converters (MMC) to improve the output spectrum. Because the MMC topology is characterized by the double-star connection of six legs consisting of cascaded modular chopper cells with floating capacitors, the balance control of the DC-link capacitor voltage is essential for safe operation. This paper presents a leg-balancing control strategy to achieve DC-link voltage balance under all operating conditions. This strategy based on circulating current decoupling control focused on DC-link balancing between the upper and lower legs in each phase pair by considering the six legs as three independent phase-pairs. Experiments are implemented on a 100-V 3-kVA downscaled prototype. The experimental results show that the proposed leg-balancing control is both effective and practical.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2009년도 제38회 동계학술대회 초록집
• /
• pp.374-374
• /
• 2010

Charge transfer mechanism of poly(4,4'-aminotriphenylene hexafluoroisopropylidenediphthalimide) (TP6F PI) which exhibits bistable ON and OFF switching has been studied using photoemission electron spectroscopy (PES) and near-edge x-ray absorption fine structure (NEXAFS). Here, we demonstrate novel set-up in which holes are injected by photoemission process instead of direct charge carrier injection via metal electrode. The accumulated charges on the PI surface in the OFF state abruptly flow across the PI film when the bias voltage of a back electrode reaches a specific value, indicating that the film is changed to the ON state. Core level and x-ray absorption spectra probed at charge injection region via photoemission process do not show any evidences implying structural modification of TP6F PI during the phase change. Whereas, in valence band spectra, the highest occupied molecular orbital (HOMO) is shifted toward Fermi level, responsible for improved hole-mobility of TP6F PI of ON state.

• 전력전자학회논문지
• /
• 제8권3호
• /
• pp.292-298
• /
• 2003

교류전동기의 가변속 운전에 사용되는 삼상 인버터에는 두개 또는 세개의 전류센서가 장착되며 이를 이용하여 삼상 교류전류를 측정한다. 전류센서의 갯수를 줄이기 위하여 개발된 것이 직류링크에 한개의 전류센서로 직류전류를 측정하고 측정된 전류 값과 스위칭 상태로부터 삼상 교류전류를 추정하는 방법이다. 전류를 정확히 측정하려면 스위칭 상태가 최소 측정시간 이상 유지되어야 하며, 이를 위한 펄스폭 조정과 이에 따른 전압 왜곡의 보상 방법이 연구되어 왔다. 그러나 기존에 발표된 방식들은 공간벡터 전압변조법에는 적합하지만 산업체에서 널리 쓰이는 펄스폭 변조 방식인 삼각파 비교법에 적용하기에는 어려운 면이 많다. 본 연구에서는 삼각파 비교법에 적합한 전류 측정 방식과 전압왜곡 보상 방식을 제안하고 이의 타당성을 실험을 통하여 검증하였다.

• 전력전자학회논문지
• /
• 제8권6호
• /
• pp.469-477
• /
• 2003

본 논문은 플라잉 커패시터 멀티-레벨 인버터의 가장 큰 문제점인 플라잉 커패시터 전압 불균형의 새로운 해결방법으로 캐리어 로테이션(Carrier-Rotation) PWM 기법을 제안한다. 제안된 기법은 모든 스위치가 한번의 스위칭동작을 하는 동안 플라잉 커패시터의 충전과 방전에 관계된 레그 전압 리던던시(redundancy)를 같은 비율로 사용하여 플라잉 커패시터 전압을 일정하게 유지하며, 전압의 변동폭이 최소가 되도록 제어한다 이 방법은 각 캐리어의 배치가 모두 통상이므로 출력 전압의 고조파 성분이 저감되며, 또한 모든 스위치의 스위칭 주파수가 같으므로 스위치 이용률이 개선되는 특성을 갖는다. 제안된 기법을 플라잉 커패시터 3-레벨 인버터에 적용하여 상세히 분석하고, 3-레벨 이상에 적용할 수 있도록 일반화한다. 제안된 기법의 타당성은 실험 결과로 검증된다.

• Journal of Communications and Networks
• /
• 제7권4호
• /
• pp.509-524
• /
• 2005

Due to the strict requirements of emerging applications, per-flow admission control is gaining increasing importance. One way to implement per-flow admission control is using an on­path resource reservation protocol, where the admission decision is made hop-by-hop after a new flow request arrives at the network boundary. The next-steps in signaling (NSIS) working group of the Internet engineering task force (IETF) is standardising such an on-path signaling protocol. One of the reservation methods considered by NSIS is reduced-state mode, which, suiting the differentiated service (DiffServ) concept, only allows per-class states in interior nodes of a domain. Although there are clear benefits of not dealing with per-flow states in interior nodes-like scalability and low complexity-, without per-flow states the handling of re-routed flows, e.g., after a failure, is a demanding and highly non-trivial task. To be applied in carrier-grade networks, the protocol needs to be resilient in this situation. In this article, we will explain the consequences of a route failover to resource reservation protocols: Severe congestion and incorrect admission decisions due to outdated reservation states. We will set requirements that handling solutions need to fulfill, and we propose extensions to reduced-state protocols accordingly. We show with a set of simulated scenarios that with the given solutions reduced-state protocols can handle re-routed flows practically as fast and robust as stateful protocols.