• 한국전자파학회논문지
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• 제23권2호
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• pp.220-228
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• 2012

본 논문에서는 밀리미터파 탐색기의 수신기 보호용으로 사용할 낮은 누설 전력을 가지는 Ka 대역 능동 리미터 설계 및 제작 기법을 설명하였다. 낮은 누설 전력을 구현하기 위해서 송신 펄스 주기 신호와 입력 전력의 크기에 따라 리미터를 제어할 수 있는 능동 리미터 제어 회로를 제안하였다. 능동 리미터는 전형적인 2단 수동 리미터에 방향성 결합기, 검파기, 연산 증폭기 및 과전류 보호용 저항으로 구성된 궤환 회로로 구성되어진다. 제작된 Ka 대역 능동 리미터 측정 결과, 주파수 대역은 1 GHz, 약 신호 시 삽입 손실은 3.5 dB 이하, 능동 제어시 최대 감쇄량 46 dB, 4 W RF 입력 시 정상 누설 전력은 -7.5 dBm을 보였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2013년도 전력전자학술대회 논문집
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• pp.244-245
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• 2013

This paper proposes a control algorithm for permanent magnet synchronous generator with a back-to-back three-level neutral-point clamped voltage source converter in a medium-voltage offshore wind power system under unbalanced grid conditions. The proposed control algorithm particularly compensates for the unbalanced grid voltage at the point of common coupling in a collector bus of offshore wind power system. This control algorithm has been formulated based on the symmetrical components in positive and negative rotating synchronous reference frames under generalized unbalanced operating conditions. Instantaneous active and reactive power are described in terms of symmetrical components of measured grid input voltages and currents. Negative sequential component of ac input current is injected to the point of common coupling in the proposed control strategy. The amplitude of negative sequential component is calculated to minimize the negative sequential component of grid voltage under the limitation of current capability in a voltage source converter. The proposed control algorithm makes it possible to provide a balanced voltage at the point of common coupling resulting in the generated power of high quality from offshore wind power system under unbalanced network conditions.

• 한국해양공학회지
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• 제33권2호
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• pp.178-188
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• 2019

When burying underwater cables using robots, heading control is one of the key functions for the robots to improve task efficiency. This paper addresses the heading control issue for URI-T, an ROV for underwater construction tasks, including the burial and maintenance of cables or small diameter pipelines. Through modeling and identifying the heading motion of URI-T, the dynamic characteristics and input limitation are analyzed. Based on the identification results, a PD type controller with appropriate input treatment is designed for the heading control of URI-T. The performance of the heading controller was verified in water tank experiments. The field applicability of the proposed controller was also evaluated through the sea trial of URI-T at the East Sea, with a water depth of 500 m.

• 기술혁신연구
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• 제26권1호
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• pp.85-105
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• 2018

본 논문은 한국의 연구개발투자가 제조업구분에 따른 파급효과들을 산업연관분석을 이용하여 분석하고 있다. 연구 방법은 2010~2014년 국내 산업연관표 상에서 연구개발투자 부문을 외생화하고, 경제협력개발기구(OECD)의 기술수준 분류표에 입각하여 기술수준별로 제조업을 분류하여 연구개발투자가 미치는 생산유발효과와 부가가치유발효과를 분석하였다. 분석결과, 연구개발투자의 기술수준별 제조업 구분에 따른 생산유발효과는 중고기술과 중저기술에 속한 제조업에서 높은 것으로 나타났으며, 부가가치유발효과 역시 중고기술 제조업에서 높은 것으로 나타났다. 반면 연구개발투자가 가장 많은 고기술제조업에서 생산유발효과와 부가가치유발효과가 상기 2부문보다 낮은 것으로 분석되었다. 이러한 결과들은 한국 제조업이 연구개발투자를 통해 기술수준의 제고를 달성하고 이를 산업구조의 고도화로 이어간다는 품질사다리론과 연계되지 않았음을 의미한다. 이러한 분석결과로부터 한국의 연구개발투자가 고기술제조업의 생산유발과 부가가치효과의 증대를 위해 구조조정이 필요하다는 시사점을 얻었다. 본 논문은 산업연관표의 구조적 특성으로 인해 연구개발투자의 시차를 고려하지 못한 한계를 안고 있다.

• 기술혁신연구
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• 제23권1호
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• pp.87-105
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• 2015

본 연구는 한국 제조업 중소기업의 R&D 투자와 성과 간의 관계를 분석하여 비선형 형태를 확인하고, 문턱값인 투자적정수준을 도출하였다. 기존 연구들은 투자와 성과 간 시차를 고려하지 않거나, 투자와 성과 간 회귀모형에서 투자 변수의 1차, 2차 항을 이용한 산술적 계산을 통하여 간접적으로 투자수준을 결정하였는데, 본 연구에서는 이를 극복하기 위해 2년의 시차를 가정한 문턱회귀모형을 사용하였다. 분석결과에 의하면, R&D 집중도 및 연구원비율과 이익률간의 관계는 S곡선 형태를 보였고, 매출액 대비 R&D 투자액 기준으로 6.4%, 종업원수 대비 연구원수 기준으로 13%가 R&D 투자의 적정수준으로 도출되었다. 연구로부터 도출된 투자 및 성과 간 관계 형태와 문턱값은 향후 기업의 R&D 투자 전략 및 정부 지원 정책의 기초자료로 활용될 수 있을 것으로 기대된다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.390-395
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• 2002

The experimental and numerical study has been conducted on the sleeve repair welding of API 5L X65 pipeline. SMA W and GTAW were applied to weld the sleeve. The macrostructure and hardness of repair welds have been examined. The [mite element analysis of the multi-pass sleeve-fillet welding has been conducted to validate the experiment and investigate the effects of in-service welding conditions. The effect of gas flow rate on the hydrogen cracking was investigated. The effect of internal pressure on residual stresses and plastic strain was investigated. The allowable heat input was predicted considering the maximum temperature of inner surface of pipe and cooling rate at CGHAZ.

• International Journal of Korean Welding Society
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• 제2권2호
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• pp.36-41
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• 2002

The experimental and numerical study has been conducted on the sleeve repair welding of API 5L X65 pipeline. SMAW and GTAW were applied to weld the sleeve. The macrostructure and hardness of repair welds have been examined. The finite element analysis of the multi-pass sleeve-fillet welding has been conducted to validate the experiment and investigate the effects of in-service welding conditions. The effect of gas flow rate on the hydrogen cracking was investigated. The effect of internal pressure on residual stresses and plastic strain was investigated. The allowable heat input was predicted considering the maximum temperature of inner surface of pipe and cooling rate at CGHAZ.

• International Journal of Korean Welding Society
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• 제4권1호
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• pp.23-29
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• 2004

In weaving welding where a V groove exists, the heat input distribution is an important factor that determines the defectiveness of the bead shape, undercut and over-lap. In this study, the amount of heat input, which is determined by the welding current, voltage, speed and weaving conditions is calculated through mathematical development and numerical methods. Furthermore, the heat input distribution as a two- dimensional heat source was observed when applied to each groove.

• Journal of Welding and Joining
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• 제31권1호
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• pp.65-70
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• 2013

Finite element analysis and welding experiments were performed to evaluate deformation aspect for Flux Cored Arc Welding(FCAW) and Electro Gas Welding(EGW). Numerical researches of FCAW and EGW were performed considering the difference of number of welding pass and welding direction to arc flow. To perform the numerical study of FCAW and EGW, number of welding pass and welding direction to arc flow were considered in the finite element model. FCAW process requires multi pass and its welding direction is vertical to welding torch. On the other hand, EGW process requires single pass and its welding direction is parallel to welding torch. The difference of welding direction and heat input was considered in the finite element analysis. In FCAW process, Goldak's double ellipsoidal heat input model was adopted. In the EGW process, Hemi-spherical power density distribution was adopted. In the results of experiment and finite element analysis, angular deformation of FCAW process is larger than that of EGW process.

• 산업경영시스템학회지
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• 제46권4호
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• pp.39-52
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• 2023

In this study, project information of government-funded research institute in the food field was collected and analyzed to systematically identify the factors affecting the process of transferring technological achievements of public research institute to the private sector. This study hypothesized that human resources, financial resources, and technological characteristics as input factors of R&D projects affect output factors, such as research papers or patents produced by R&D projects. Moreover, these outputs would serve as drivers of the technology transfer as one of the R&D outcomes. Linear Regression Analysis and Poisson Regression Analysis were conducted to empirically and sequentially investigate the relationship between input factors and output and outcome of R&D projects and the results are as follows: First, the principle investigator's career and participating researcher's size as human resource factors have an influence on both the number of SCI (science citation index) papers and patent registration. Second, the research duration and research expenses for the current year have an influence on the number of SCI papers and patent registrations, which are the main outputs of R&D projects. Third, the technology life cycle affects the number of SCI papers and patent registrations. Lastly, the higher the number of SCI papers and patent registrations, the more it affected the number of technology transfers and the amount of technology transfer contract.