• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2012.06a
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• pp.338-340
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• 2012

항만의 시설물을 개선함에 있어서 해상교통안전진단이 이루어지고 있으며 포항항 스웰개선대책 시설물 건설 관련된 해상교통안전진단 사례 소개를 통하여 도출된 문제점에 대한 해결방안을 제시하였다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2011.06a
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• pp.129-131
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• 2011

해상기상은 재박 및 운항 선박의 안전에 중요한 영향을 미친다. 따라서, 관제구역에서 선박 안전운항을 관리하는 VTS에 있어 기상예보 및 국지적 실시간 기상정보를 모니터링 하여 대상선박에 대해 사전 안전조치를 취하거나 실무 관제에 중요한 참고자료로 활용해야 함이 해양사고 예방을 위해서 절대적으로 요청되고 있다. 이 논문에서는 겨울철 기압골 형성에 따라 동해안에서 자주 발생하고 있는 북동방향으로 부터의 스웰 유입에 대해, 2011년 1월 1일 포항항에 큰 스웰 유입 당시의 해상기상에 대한 예보 및 실측 자료를 분석하여, 문제점을 고찰하고 선박관제 운용에 있어 기상정보 활용의 중요성을 부각시키고자 노력 하였다. 아울러, 기상청 홈페이지에서 제공하고 있는 상세 기상정보를 선박관제 운용에 활용하고 있는 포항청 사례를 소개하여 타 항만에서도 해상기상 악화에 대비 대응할 수 있는 방안 모색에 도움이 되고자 한다.

• Elastomers and Composites
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• v.46 no.1
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• pp.54-59
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• 2011

One of the viscoelastic flow behaviors during profile extrusion is the swelling of extrudate. In this study, die swell of rubber compound in the capillary die have been investigated through experiment and computer simulation. Simplified viscoelastic model and non-linear differential viscoelastic model such as PTT model have been used in the computer simulation. The simulation results have been compared with experimental data. Experiment and simulation have been performed using fluidity tester and commercial CFD code, Polyflow respectively. Die swells predicted by two models showed good agreement with experimental results. Pressure and velocity distribution, and circulation flow at the corner of reservoir have been well predicted by PTT model. Simplified viscoelastic model can not predict circulation flow at the corner of reservoir. However this model has an advantage in computation time compare with full viscoelastic model, PTT model.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06c
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• pp.361-364
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• 1998

주파수 합성기는 주로 PLL을 이용하여 설계하는데, PLL(Phase-lock loop)이란 출력신호 주파수를 항상 일정하게 유지하도록 구성된 주파수 부귀환 회로로써 기본적인 구성은 위상출력기, 저역통과필터, 전압 제어 발진기로 이루어진다. 이런 PLL의 기본적인 구성에 프로그래머블카운터를 VCO의 출력단에 부가하여 구성한 형태가 주파수합성기이다. 이 주파수합성기의 출력을 프로그래머블 디바이더에 입력하기 전에 주파수를 낮출 필요가 있는데, 현재 슈퍼헤테로다인 다운 컨버터방식과 프리스케일러방식과 펄스 스웰로 카운터를 사용하는 방식 등의 3가지 방법이 있다. 본 논문에서는 펄스 스웰로 카운터 방식의 주파수 합성기를 MATLAB의 GUI환경과 병행하여 시뮬레이션 과정을 통한 동작특성을 이해하고, 한 화면에서 이루어지는 조작에 의해 모든 주파수 합성기의 요소를 관찰할 수 있도록 모델링하였다. 그리고, 모델링한 주파수합성기와 실제 주파수합성기에서 예상되는 출력과 비교하여 그 결과에 있어서 얼마나 유사한지 살펴보았다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2018.11a
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• pp.353-354
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• 2018

스웰 등 장주기파랑은 높은 에너지를 갖고 있어서 바람이 없어도 에너지가 사라지지 않고 전파되어 항만에 이르게 되고, 차폐된 항내수역에서 파고가 증폭되어 대형선박의 접이안과 하역작업을 중단시키는 경제적 손실을 야기한다. 본 실험은 대규모 개발에 따른 장주기 파랑에 의한 반응특성과 부진동의 영향을 검토하였다. 특히, 항만확장외에 외역에 추가적 개발을 위한 매립을 고려하여 항만정온도와 장주기 반응 특성을 파악하여 가능한 대책방향을 검토하고자 하였다.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.1
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• pp.80-87
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• 2016

This study investigates output voltage variation of a voltage disturbance generator in case of sag and swell modes. The generator uses series transformers and silicon-controlled rectifier thyristors to provide voltage disturbance; consequently, voltage drop at the output terminal is inevitable. On the basis of the analysis, voltage drop increases as the power factor decreases in lagging. Voltage drop is 3.7 [%] at a power factor (lagging) of 0.8. Simulation and experimental results show the validity of the analysis.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.3
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• pp.163-170
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• 2008

Switching characteristics in both linear and nonlinear loads are analysed for a 3-phase voltage disturbance generator applicable to the performance test of custom power devices. Since the line current of the linear load is continuous the natural commutation of the SCR thyristors comprising the generator is carried out with ease. However, in case of nonlinear load the natural commutation scheme is different from that of the linear load due to the discontinuous load current. Through the analysis it is found that a specific switching condition can provide the voltage sag, swell, outage, and voltage unbalance generation in nonlinear load too. The operation of the voltage disturbance generation is described and the usefulness of the generator is verified through simulation and experimental results. It is expected that the generator can be used in the performance test of the custom power devices with low implementation cost and easy control.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.6
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• pp.367-373
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• 2021

In this study, deep learning model was set up to predict the wave heights inside a harbour. Various machine learning techniques were applied to the model in consideration of the transformation characteristics of offshore waves while propagating into the harbour. Pohang New Port was selected for model application, which had a serious problem of unloading due to swell and has lots of available wave data. Wave height, wave period, and wave direction at offshore sites and wave heights inside the harbour were used for the model input and output, respectively, and then the model was trained using deep learning method. By considering the correlation between the time series wave data of offshore and inside the harbour, the data set was separated into prevailing wave directions as a pre-processing method. As a result, It was confirmed that accuracy and stability of the model prediction are considerably increased.

• The Korea Journal of Herbology
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• v.29 no.3
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• pp.79-85
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• 2014

Objectives : In this study, we attempted to evaluate the effects of Careswell on human mast cell-mediated allergy inflammation in vitro and pruritogen-induced scratching behavior in vivo. Method : The Careswell was extract by distilled water. The anti-itching effects of Careswell were investigated on the compound 48/80 ($50{\mu}g/kg$) or histamine ($100{\mu}g/kg$) induced scratching behavior male ICR mice for 30 min by an observer blind. Terfenadine (10 mg/kg) was used as a positive control drug. The cell toxicity of Careswell was determined by 3-(4,5-dimethylthiazole-2-yl)-2, 5-diphenyl-tetrazolium bromide (MTT) assay. The regulatory effect of Careswell on interleukin (IL)-6 and tumor necrosis factor (TNF)-${\alpha}$ levels was determined by enzyme-linked immunosorbent assay (ELISA) in phorbol 12-myristate 13-acetate plus calcium ionophore A23187 (PMACI) stimulated human mast cells (HMC-1). Also, we evaluated the effect of Careswell on PMACI induced the activation of Nuclear factor-kappa B (NF-${\kappa}B$) into nucleus by Western blot analysis. Result : The results revealed that the oral administration of Careswell (200 mg/kg, p.o.) attenuated the compound 48/80 or histamine-induced scratching behavior in mice. We showed that Careswell significantly reduced the PMACI-induced the production of IL-6 (0.5-1 mg/ml) and TNF-${\alpha}$ (0.1-1 mg/ml). Additionally, Careswell significantly inhibited the activation of NF-${\kappa}B$ in PMACI-stimulated HMC-1. Conclusion : Collectively, the findings of this study provide us with a novel insight into the pharmacological actions of Careswell as a potential molecule for use in the treatment of allergic inflammation diseases.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.5
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• pp.463-470
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• 2006

This paper deals with a new 3-phase power quality disturbance generator. The proposed generator can provide phase jump as well as voltage sag, swell, outage, unbalance, and over and under voltage. The operating principle of the generator is described in each mode of disturbance. The magnitude of the phase jump is analysed and it is found that the magnitude is the function of the turn-ratios of the transformers consisting the generator. The scheme has simple structure compared with the conventional one, and the major components of the proposed scheme are SCR thyristor and transformer, which guarantees high reliability and cost-effective implementation of the generator. Furthermore, high efficiency can be obtained because there is no PWM switching of the semiconductor devices, and it is easy to control the system. Simulations are carried out to confirm the operation in each disturbance mode, and experiments has been done with 5kVA power rating. The usefulness of the proposed scheme is verified through simulation and experimental results. It is expected that the scheme can be applied to the performance test of the custom power devices such as UPS, DVR, DSTATCOM, and SSTS with cost-effective system.