• 수산해양기술연구
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• 제53권4호
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• pp.309-316
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• 2017

In this paper, numerical modeling is conducted to analyze the tension of an anchor line by varying the size and drag coefficient of a buoy when the trapnet is influenced by the wave and the current simultaneously. A mass-spring model was used to analyze the behavior of trapnet underwater under the influence of waves and current. In the simulation of numerical model, wave height of 3, 4, 5 and 6 m, a period of 4.4 s, and the flow speed of 0.7 m/s were used for the wave and current condition. The drag coefficients of buoy were 0.8, 0.4 and 0.2, respectively. The size of buoy was 100, 50 and 25% based on the cylindrical buoy ($0.0311m^3$) used for swimming crab trap. The drag coefficient of the trapnet, the main model for numerical analysis, was obtained by a circular water channel experiment using a 6-component load cell. As a result of the simulation, the tension of the anchor line decreased proportional to buoy's drag coefficient and size; the higher the wave height, the greater the decrease rate of the tension. When the buoy drag coefficient and size decreased to one fourth, the tension of the anchor line decreased to a half and the tension of the anchor line was lower than the holding power of the anchor even at 6 m of wave height. Therefore, reducing the buoy drag coefficient and size appropriately reduces the trapnet load from the wave, which also reduces the possibility of trapnet loss.

• Progress in Superconductivity
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• 제4권1호
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• pp.42-47
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• 2002

Measuring magnetic fields with a SQUID sensor always requires preliminary adjustments such as optimum bas current determination and flux-locking point search. A conventional magnetoencephalography (MEG) system consists of several dozens of sensors and we should condition each sensor one by one for an experiment. This timeconsuming job is not only cumbersome but also impractical for the common use in hospital. We had developed a serial port communication protocol between SQUID sensor controllers and a personal computer in order to control the sensors. However, theserial-bus-based control is too slow for adjusting all the sensors with a sufficient accuracy in a reasonable time. In this work, we introduce programmatic control sequence that saves the number of the control pulse arrays. The sequence separates into two stages. The first stage is a function for searching flux-locking points of the sensors and the other stage is for determining the optimum bias current that operates a sensor in a minimum noise level Generally, the optimum bias current for a SQUID sensor depends on the manufactured structure, so that it will not easily change about. Therefore, we can reduce the time for the optimum bias current determination by using the saved values that have been measured once by the second stage sequence. Applying the first stage sequence to a practical use, it has taken about 2-3 minutes to perform the flux-locking for our 37-channel SQUID magnetometer system.

• 대한수의학회지
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• 제45권4호
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• pp.581-585
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• 2005

The purpose of this study is to establish the analgesic effects of electroacupuncture for Korean native goat. Electroacupuncture was applied to the 6 Korean native goats. In 3 of them, rumenotomy was performed, and in the other 3, laparotomy was done. The analgesic induction time was 15 to 30 minutes. The acupoints used were Tian-ping (Celestial Peace, GV-5), Bai-hui (Hundred Meetings, GV-20), left 13th thoracic nerve and left 3rd lumbar nerve. Electroacupuncture was performed in lateral recumbency. Needles were inserted 1-2 cm deep, and connected to the electroacupuncture apparatus. The electrical stimulation condition was 30 Hz and 2-6 volts. Initially, the voltage of analgesia mode was maximized in each channel. And, the output was slowly reduced to the critical point that goats could tolerate without obvious discomfort or pain. Surgical operation was done successfully under electroacupuncture analgesia in 6 Korean native goats. In addition, the changes of temperature, heart rate and respiratory rate were studied during acupuncture analgesia. For 3 months after surgery, no experimental animals showed clinical problem in 6 Korean native goats.

• Journal of the Korean Wood Science and Technology
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• 제38권6호
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• pp.498-506
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• 2010

국산 침엽수재를 고부가가치의 구조부재로 활용하기 위해서는 국내 기준에 적합한 등급구분 체계가 갖춰져야 한다. 김 등(2009a, b)의 연구에서는 목재의 생산 및 유통규모가 작은 국내 현실에서 제재목 등급구분의 자동화 및 기계화를 목적으로 화상처리시스템을 개발하였다. 본 연구에서는 이전 연구에서 개발한 화상처리시스템의 핵심 기술 중 하나인 화상입력시스템의 성능을 향상시키기 위하여 최적 화상병합 조건을 구명하고자 하였다. 연구 결과 국산 낙엽송 $180{\time}120$ mm 부재의 화상을 병합하는 데 있어서 획득된 화상의 green채널 정보를 병합 에 이용하는 것이 가장 높은 병합정확성을 얻을 수 있었다. 입력된 화상의 전처리 과정으로 Y-derivative Sharr's kernel 필터를 적용함으로써 화상병합 성능을 향상시킬 수 있었으나, 카메라 보정에 의한 효과는 미미 하였다. 또한 화상병합을 위한 최적 템플릿 크기는 폭 30 pixel ${\time}$ 높이 150 pixel로 확인되었다. 이상의 조건을 적용하였을 때, 병합된 화상의 길이오차는 평균 3.1 mm, 연산시간은 평균 9.7초로 나타났다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.380-383
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• 2006

The media transport system is used in a printer, a ATM(Automated Tellor Machine), and so on. The media transport system has many problems through miniaturization and rapid transportation of these machines. In the paper feeding mechanism, it is important to feed the sheet without jamming under any conditions. To avoid sheet jamming, first we need to predict the behavior of the sheet exactly. In this paper, the analysis of media behavior is based on J. Stolte's studies. In all of OA machines, a flexible beam or plate is pushed from the channel. The motion may be constrained by guides. This leads to a transient and geometrically nonlinear problem. The behavior of paper is simulated by dynamic elastica theory. The shape of guide is represented by parametric cubic curve. But J. Stolte's studies did not considered contact condition between sheet and guide. So Klarbring's Model. will be applied. And the analysis of flexible media has to include aerodynamic effect for more exact behavior analysis, because the flexible media can be deformed drastically by a little force. Therefore aerodynamic force must be applied to the governing equation. Lastly, the simulation of this model is performed, and the experiment is performed for verification of this model. The experimental results of low exit velocity are consistent with the simulation results, however experimental results of high exit velocity do not agree well with analytical results. The reason is that there may be other effects like nip Phenomena

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.106-106
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• 2011

Recently, zinc oxide (ZnO) thin films have attracted great attention as a promising candidate for various electronic applications such as transparent electrodes, thin film transistors, and optoelectronic devices. ZnO thin films have a wide band gap energy of 3.37 eV and transparency in visible region. Moreover, ZnO thin films can be deposited in a poly-crystalline form even at room temperature, extending the choice of substrates including even plastics. Therefore, it is possible to realize thin film transistors by using ZnO thin films as the active channel layer. In this work, we investigated influence of oxygen partial pressure on ZnO thin films and fabricated ZnO-based thin film transistors. ZnO thin films were deposited on glass substrates by using a pulsed laser deposition technique in various oxygen partial pressures from 20 to 100 mTorr at room temperature. X-ray diffraction (XRD), transmission line method (TLM), and UV-Vis spectroscopy were employed to study the structural, electrical, and optical properties of the ZnO thin films. As a result, 80 mTorr was optimal condition for active layer of thin film transistors, since the active layer of thin film transistors needs high resistivity to achieve low off-current and high on-off ratio. The fabricated ZnO-based thin film transistors operated in the enhancement mode with high field effect mobility and low threshold voltage.

• 수산해양기술연구
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• 제52권4호
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• pp.299-307
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• 2016

This study aims to investigate effects of the length of the buoy and sand bag line on the loss of webfoot octopus pot. A numerical modeling and simulation was carried out to analyze the process that the pot gear affected by wave using the mass spring model. Through the simulation, tensions of sand bag line under various condition were investigated by length of buoy and sand bag line. The drag force and coefficient k of an artificial shell used in the webfoot octopus pot was obtained from an experiment in a circular water channel, and the coefficient k was applied to the simulation. To verify the accuracy of the simulation model, a simple test was conducted into measuring a rope tension of a hanging shell under flow. Then, the test result was compared with the simulation. The lengths of the buoy line in the simulation were 1.12, 1.41, 1.80, 2.23, 2.69, and 3.17 times of water depth. The lengths of sand bag line were 10, 20, 30, and 40 meters, and conditions of water depth were 8, 15, 22 meters. 4 meter height and 8 second period of wave were applied to all simulations. As a results, the tension of the sand bag line was decreased as the buoy and sand bag line were increased. The minimum tension of the sand bag line was appeared in conditions that the length of the buoy line is twice of water depth and the sand bag line length is over 40 meters (except in case of depth 8 meters.).

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권9호
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• pp.4398-4417
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• 2017

Multi-user Multiple-Input and Multiple-Output (MU-MIMO) has potential for prominently enhancing the capacity of wireless network by simultaneously transmitting to multiple users. User selection is an unavoidable problem which bottlenecks the gain of MU-MIMO to a great extent. Major state-of-the-art works are focusing on improving network throughput by using Channel State Information (CSI), however, the overhead of CSI feedback becomes unacceptable when the number of users is large. Some work does well in balancing tradeoff between complexity and achievable throughput but is lack of consideration of fairness. Current works universally ignore the rational utilizing of time resources, which may lead the improvements of network throughput to a standstill. In this paper, we propose TOUSE, a scalable and fair user selection scheme for MU-MIMO. The core design is dynamic-time-warping-based user selection mechanism for downlink MU-MIMO, which could make full use of concurrent transmitting time. TOUSE also presents a novel data-rate estimation method without any CSI feedback, providing supports for user selections. Simulation result shows that TOUSE significantly outperforms traditional contention-based user selection schemes in both throughput and fairness in an indoor condition.

• 한국항공우주학회지
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• 제43권1호
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• pp.72-78
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• 2015

오늘날 위성은 통신, 기상, 해양탐사, 광학, 레이다등 민수분야에서 군사분야까지 폭넓게 적용되어 그 유용성이 점점 더 증가되고 있다. 또한, 부품기술의 발달로 위성 전장품의 기능도 더욱 능동적인 형태로 진화되고 있다. 위성선진국에서는 통신위성의 중계기 효율을 증가시키고, 간섭신호를 제거하여 가입자 서비스 품질을 유지하기 위해서 디지털중계기를 탑재하고 있다. 디지털중계기는 다양한 기능구현을 위해 신호처리용 부품들을 다수 사용한다. 따라서, 기존의 수동형 중계기에 비해 많은 전력을 소모하여 더 높은 발열 상태를 유지한다. 본 논문에서는 우주인증모델(EQM)급으로 자체 제작된 디지털중계기 열진공 시험결과의 성능을 분석한다. 열진공시험과정중 디지털중계기의 기능검증을 위해 디지털 이득조정 시험결과를 제시한다. 또한, 열진공 시험결과를 근거로 주요부품의 부하경감(Derating)을 분석하여 디지털중계기 설계의 적절성을 논의한다.

• 방송공학회논문지
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• 제13권5호
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• pp.719-731
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• 2008

본 논문은 WiBro 망을 통한 다시점 비디오 서비스의 품질을 향상시키기 위하여, 수신자가 느끼는 다시점 비디오 품질을 위한 QoE (Quality of Experience)를 정의하고, 이를 최대화할 수 있는 계층 간 최적화 방식(Cross-Layer Optimization: CLO)을 제안한다. 제안하는 계층 간 최적화 방식(이하 CLO) 알고리즘은 물리계층에서 비디오계층까지 포함한다. 시간과 장소에 따라 변화하는 무선망 상황에서, 다시점 비디오의 시점별 중요도와 시간적 중요도를 구분하여, 프레임 전송 우선순위와 순방향 오류 정정(Forward Error Correction : FEC) 수준을 결정한다. 핸드오버 상황에서 제안하는 CLO 방식을 사용하였을 때 최소의 자원으로 최고대의 QoE를 달성할 수 있음을 시뮬레이션을 통하여 보여준다.