• Journal of Chest Surgery
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• 제23권6호
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• pp.1074-1083
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• 1990

This study was evaluated the metabolic, physiologic and histologic effects of myocardial protection of verapamil[isoveratril]on isolated rat hearts to 90 minutes of ischemic arrest. Heart was perfused with a modified Kreb’s Henseleit bicarbonate buffer with glucose and arrested with retrograde coronary perfusion by glucose insulin[GI], potassium and verapamil. Mean aortic systolic pressure, heart rate, coronary flows were measured and morphologic changes were examined during working heart perfusion. Perfusion and arrest were controlled four groups subjected 60 isolated rat hearts. Four groups hearts reperfused during 40 minutes after 90 minutes global ischemia for physiologic recovery. 15 hearts of four groups were assayed to histological morphologic changes. GI treated hearts recovered less than 28% of function and changed more than 80% of mitochondria of control group. Verapamil hearts[0.2, 0.1 gm/kg] recovered more than 88% of function and permitted the maintenance of continuous cellular level of Serum Glutamic Oxalaxetate Transaminase[SGOT], but declined 28% of Phosphate Kinase[CP], GI treated heart showed widespread evidence of extensive damage of mitochondria. The damage was that interstitial huge edema are present and there was contraction band formation within the swollen cells. The verapamil and potassium group were not found morphologic change compared with control group. Their functions were shown that metabolic and physiologic action of verapamil-group lasted 20 minutes longer than potassium group.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1234-1238
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• 2005

As the low power GPS signal is susceptible to interference, interference can seriously degrade the performance of GPS receiver. This paper designs a ANIEF(Adaptive Narrowband Interference Excision in Frequency domain) filter that removes narrow band interferences with low signal loss. This filter uses the pre-correlation technique and attempts to filter out the interference in the frequency domain. The interference excision performance of the designed filter is evaluated for various interferences using the ANIEF filter inserted GPS software receiver and the interference generator. Interferences considered in this paper are single-tone CWI(Continuous Wave Interference), multi-tones CWI, pulsed CWI, and swept CWI. The narrowband interference excision filter in frequency domain is very effective against various interferences and the strong interference with a simple structure. However, the signal power loss is unavoidable while transforming. In this paper, the hamming window and overlap technique are adopted to reduce the signal power loss. Finally, the interference excision performance and the reduced signal power loss of the ANIEF filter are shown.

• 대한화학회지
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• 제19권4호
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• pp.246-251
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• 1975

Dideptidyl carboxypeptidases와 angiotenisn-coverting enzyme의 새로운 기질불질로서 thiol ester 인 S-Hippuryl thioglycolyl glycine을 합성하였으며, 이 기질에 의한 간편하고도 예민한 효소 활성도의 정량방법을 제시하였다. 이 경우 효소반응 생성물인 thioglycolyl glycine은 반응계중에 첨가한 5,5-dithio-bis-(2-nitrobenzoic acid), DTNB와 쉽게 반응하여 410nm에서 강한 흡광스펙트럼을 갖는 5-thio-2-nitrobenzoic acid(${\varepsilon}M=1.36{\times}10^4$)을 형성함으로서 효소의 새로운 미량정량 방법으로 이용 가치가 크다고 본다.

• 한국인터넷방송통신학회논문지
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• 제10권4호
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• pp.121-126
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• 2010

HEMP분야에 대한 연구는 1950년대 이후 미국을 중심으로 핵을 보유한 국가에 의해 주로 국가방위를 목적으로 수천 건의 연구가 집중적으로 이루어졌다. HEMP 방호설비의 핵심은 차폐, 필터링, 접지, 과전압 보호로 구성된다. 이중에서 투자비용이 가장 높은 차폐실 설계에 있어 기존에 나와 있는 이론식을 적용하여 시뮬레이션을 하면 특정 주파수 대역을 제외하고 실제 측정값과 전혀 맞지 않는 모순이 있었다. 본 논문에서는 HEMP 방호용 차폐실의 최적설계를 위해 기존 이론식을 개선하여 실제 측정값과 넓은 주파수 범위에서 잘 일치할 수 있는 이론을 제시하고, 각각의 재료정수에 따라 설계전에 충분하게 시뮬레이션을 거쳐 경제적이고 효과적으로 HEMP 방호용 차폐실을 건설할 수 있도록 하는 시뮬레이터를 개발하였다.

• 한국정보통신학회논문지
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• 제7권5호
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• pp.879-886
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• 2003

주파수 도약 대역확산시스템에서의 광대역 주파수 도약을 위해 주파수 합성기가 널리 이용된다. 따라서 본 논문에서는 효과적인 무선 디지털 데이터 전송 성능을 얻기 위한 FH-FSK 통신에 미치는 주파수 합성기의 영향을 분석하였다. 이를 위해 PLL의 성능을 좌우하는 위상 변화, 스퓨리어스의 발생, PLL의 과도응답 특성에 의해 영향을 받는 주파수 도약율 등 여러 가지 파라미터들에 따른 성능을 분석하였다. 전형적인 PLL을 사용한 주파수 도약 시스템에서는 주파수 도약을 위한 반송파 신호를 국부 발진기에서 만들어낸다. 반송파 간격이 협대역인 협대역 무선 통신 시스템일 경우에는 빠른 주파수 도약을 위한 PLL의 구현이 어렵다. 본 논문에서는 이런 문제점을 해결하기 위해 디지털 주파수 합성기/CPM 변조기를 사용하여 빠른 주파수 도약을 위한 PLL 구현이 가능함을 Matlab tool를 사용한 시뮬레이션 결과를 통해 분석할 수 있었다.

• Journal of Power Electronics
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• 제16권5호
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• pp.1743-1751
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• 2016

The increasing demand for high voltage DC grids resulting from the continuous installation of offshore wind farms in the North Sea has led to the concept of multi-terminal direct current (MTDC) grids, which face some challenges. Power (current) flow control is a challenge that must be addressed to realize a reliable operation of MTDC grids. This paper presents a reduced switch count topology of a current flow controller (CFC) for power flow and current limiting applications in MTDC grids. A simple control system based on hysteresis band current control is proposed for the CFC. The theory of operation and control of the CFC are demonstrated. The key features of the proposed controller, including cable current balancing, cable current limiting, and current nulling, are illustrated. An MTDC grid is simulated using MATLAB/SIMULINK software to evaluate the steady state and dynamic performance of the proposed CFC topology. Furthermore, a low power prototype is built for a CFC to experimentally validate its performance using rapid control prototyping. Simulation and experimental studies indicate the fast dynamic response and precise results of the proposed topology. Furthermore, the proposed controller offers a real solution for power flow challenges in MTDC grids.

• 한국분말재료학회지
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• 제23권4호
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• pp.307-310
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• 2016

$TiOF_2$, which has remarkable electrochemical and optical properties, is used in various applications such as Li-ion batteries, electrochemical displays, and photocatalysts. In addition, it is possible to utilize the template which is allowed to synthesize fluorine doped $TiO_2$ powders with hollow or faceted structures. However, common synthesis methods of $TiOF_2$ powders have some disadvantages such as the use of expensive and harmful precursors and batchtype processes with a limited production scale. In this study, we report a synthetic route for preparing $TiOF_2$ powders by using an inexpensive and harmless precursor and a continuous ultrasonic spray pyrolysis process under a controlled atmosphere to address the aforementioned problems. The synthesized powder has an average size of $1{\mu}m$, a spherical shape, a pure $TiOF_2$ phase, and exhibits a band-gap energy of 3.2 eV.

• Journal of electromagnetic engineering and science
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• 제15권2호
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• pp.82-88
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• 2015

The magnetron, a vacuum tube, is currently the usual high-power microwave power source used for microwave heating. However, the oscillating frequency and output power are unstable and noisy due to the low quality of the high-voltage power supply and low Q of the oscillation circuit. A heating system with enhanced reliability and the capability for control of chemical reactions is desired, because microwave absorption efficiency differs greatly depending on the object being heated. Recent studies on microwave high-efficiency power amplifiers have used harmonic processing techniques, such as class-F and inverse class-F. The present study describes a high-efficiency 100 W GaN-HEMT amplifier that uses a harmonic processing technique that shapes the current and voltage waveforms to improve efficiency. The fabricated GaN power amplifier obtained an output power of 50.4 dBm, a drain efficiency of 72.9%, and a power added efficiency (PAE) of 64.0% at 2.45 GHz for continuous wave operation. A prototype microwave heating system was also developed using this GaN power amplifier. Microwaves totaling 400 W are fed from patch antennas mounted on the top and bottom of the microwave chamber. Preliminary heating experiments with this system have just been initiated.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2016년도 춘계학술발표대회
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• pp.124-126
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• 2016

Successful deployment of the Software Defined Network (SDN) depends on its ability to cope up with network failures. There are various types of failures that may occur in an SDN. The most common are switch and link failures. It is necessary to recover the network from failures for a continuous service availability. But for the real-time services fast recovery from the failure is required to minimize the service disruption time. In the proposed work, we focused on minimizing the recovery time after the failure is detected. Once the failure is detected, the controller involvement is needed to dynamically reroute the failure disrupted flows from the failed component to an alternate path. The aim of the proposed scheme is to provide a traffic management scheme which can react to the dynamic network events by rapidly modifying the forwarding behavior of the switches for faster in-band network adaptability. The proposed scheme (1) Considers the shared data and control path delay (2) Optimally utilize the network resources (3) Eliminates the need of constant monitoring overhead at the controller which results into faster detouring and ultimately rapid recovery.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제9권3호
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• pp.178-184
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• 2009

An efficient fault diagnosis system is needed for industry because it can optimize the resources management and improve the performance of the system. In this study, a fault diagnostic system is proposed for rotating machine using wavelet packet transform (WPT) and elman neural network (ENN) techniques. In most fault diagnosis for mechanical systems, WPT is a well-known signal processing technique for fault detection and identification. In previous work, WPT can improve the continuous wavelet transform (CWT) used over a longer computing time and huge operand. It can also solve the frequency-band disagreement by discrete wavelet transform (DWT) only breaking up the approximation version. In the experimental work, the extracted features from the WPT are used as inputs in an Elman neural network. The results show that the scheme can reliably diagnose four different conditions and can be considered as an improvement of previous works in this field.