• 지식경영연구
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• 제18권2호
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• pp.85-102
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• 2017

With rapid development of information and communication technologies, open collaboration can be eased through the Internet. Open source software, as a representative area of open collaboration, is developed and adopted to various fields. In this research, based on organizational learning theory, we examine the impacts of exploration and exploitation on innovation performance in open source software development projects. We define knowledge exploration as a number of developers from outside organization and knowledge exploitation as the ratio of member of an organization who participated in an open source software project managed by the organization. For analysis, we collect data of 4794 projects from github which is a representative open source software development platform using Web crawler developed by Python. As a result, we find that excessive exploration has curvilinear (invers U-shape) relationship on project performance. On the other hand, exploitation with enough external developers will positively impact on project performance.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2010년도 추계학술대회 논문집
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• pp.101-109
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• 2010

This paper reports active control of clamped beams using acceleration feedback controllers (AF). The equations of motion of clamped beam under force and moment pairs were derived and the equations of AF controllers were formulated. The effect of the parameters - gain and damping ratio - of the AF controllers on the open loop transfer function was investigated mainly in terms of the system stability. Increasing the gain of the AF controller tuned at a mode, the magnitude of the open loop transfer function is increased at all frequencies. The increase of the damping ratio of the AF controller leads to decrease the magnitude of the open loop transfer function and modifies its phase characteristics to be more stable. Three AF controllers connected in parallel were then proposed. Each AF controller is tuned at the $2^{nd}$, $3^{rd}$ and $4^{th}$ modes, respectively. Their parameters were determined to remain the system to be stable based on the results of the parametric study. A significant reduction in vibration at the 3 modes can be obtained.

• 환경영향평가
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• 제15권5호
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• pp.299-308
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• 2006

To utilize a closed municipal solid waste landfill site in environmentally secure conditions, it is necessary to verify the stabilization level of landfill leachate. To assess leachate stabilization of an open-dumping municipal solid waste landfill site (Salmi Landfill) which is located at the vicinity of Chungju Reservoir which flows into Paldang Reservoir utilized as Seoul Metropolitan water supplies, the landfill history and surrounding characteristics of the landfill site were surveyed. In this investigation, waste, leachate, groundwater and surfacewater samples from this landfill were physically and chemically analyzed, and the analysis results were evaluated by 'The Criteria of Landfill Waste Stabilization (CLWS)', 'Discharge Criteria of Landfill Leachate', 'The Criteria of Domestic Use in Groundwater Quality', and 'The Criteria of Domestic Use in Surfacewater Quality' that promulgated by Korean Ministry of Environment. From the analysis results on the Salmi open-dumping landfill, C/N ratio was 18.9 and $BOD/COD_{Cr}$ ratios in leachate were higher than 1/10. Based on the CLWS, this results seemed to imply that the process of leachate stabilization at this landfill was still proceeding.

• 한국해양환경ㆍ에너지학회지
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• 제2권1호
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• pp.49-62
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• 1999

해상에서의 선박의 충돌이나 좌초로 인한 유출사고시 오일붐은 기름의 확산을 방지하고 유출된 기름을 일정한 두께로 모아 유회수기(oil skimmer)의 회수효율을 높이는 목적으로 사용되고 있다. 해상에 설치된 오일붐은 조류속도, 파고, 풍속 등 다양한 해상조건에 따라 보유성능(oil-containment capability)에 영향을 받는다. 본 연구에서는 오일붐의 성능평가 기법 개발의 일환으로 1998년 4월 20일부터 30일까지 10일 동안 여수 우암 앞바다에서 고형식, 총기팽창식, 자동팽창식 오일붐 등 3종류를 대상으로 실해역에서의 조류속도, 풍속, 파고, 선박의 예인속도 등 해양조건에 따른 오일붐의 거동 및 월파현상을 분석하고, gap ratio에 따른 오일붐의 장력을 계측하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.527-535
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• 2012

This paper reports the active vibration control of plates using positive position feedback controller (PPF). The equations of motion of the plate under force and moment pairs were derived and the equations of PPF controllers were formulated. The effect of the parameters - gain and damping ratio - of the PPF controllers on the open loop transfer function was investigated mainly in terms of the system stability. Increasing the gain of the PPF controller tuned at a mode, the magnitude of the open loop transfer function is increased at all frequencies without changing the phase behavior. The increase of the damping ratio of the PPF controller leads to decrease the magnitude of the open loop transfer function and to modify its phase characteristics to be more stable. Two PPF controllers connected in parallel, Each PPF controller is tuned at the $1^{st}$ and $2^{nd}$ modes, respectively. Their parameters were determined to remain the system to be stable based on the results of the parametric study. A significant reduction in vibration at the 2 modes can be obtained.

• 소성∙가공
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• 제20권7호
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• pp.518-523
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• 2011

The three dimensional geometries of an aluminum open cell foam before and after uniaxial compressive loading were investigated using the X-ray micro CT(computed tomography). Aluminum 6101-T6 open cell foams of 10, 20, 40 ppi (pore per inch) were considered in this work. After the serial sectioning CT images of aluminum foams were obtained from non-destructive X-ray images, the exact 3D structure were reproduced and visualized with commercial image processing program. The relative density ratio was around the 7.0 to 9.0 range, the unit cells showed anisotropic shapes having the different dimensional ratios of 1.1 to 1.3 between the rise and the transverse directions. The yield stress increased with the relative density ratio and the volumetric strain increased proportionally with compressive strain. The plateau stress in the compressive stress-strain curve was caused by the buckling of ligaments.

• 전기학회논문지
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• 제58권12호
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• pp.2462-2467
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• 2009

This paper proposes a dual band branch line coupler (BLC) using a composite right/left handed (CRLH) transmission line. The existing dual band BLCs with open stubs require hundreds of line impedance for the open stub as the frequency bands approach to each other, so it has been almost impossible to realize them. However in the proposed BLC, a CRLH transmission line replaces the open stub with an extremely high line impedance so that the BLC circuit may be realized even two frequencies are close to each other. As an example, a dual band BLC operating at 1800MHz and 2300MHz (the frequency ratio is 1:1.28) is designed and measured. Open stubs with $560\Omega$ line impedance are replaced by CRLH transmission lines for realizing the dual band BLC. The measured performances prove that the dual band operation is well acceptable and the proposed design method is successful even the ratio between two frequencies is not around two nor more.

• 한국소음진동공학회논문집
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• 제20권12호
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• pp.1190-1199
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• 2010

This paper reports active control of clamped beams using acceleration feedback controllers (AF). The equations of motion of clamped beam under force and moment pairs were derived and the equations of AF controllers were formulated. The effect of the parameters - gain and damping ratio - of the AF controllers on the open loop transfer function was investigated mainly in terms of the system stability. Increasing the gain of the AF controller tuned at a mode, the magnitude of the open loop transfer function is increased at all frequencies. The increase of the damping ratio of the AF controller leads to decrease the magnitude of the open loop transfer function and modifies its phase characteristics to be more stable. Three AF controllers connected in parallel were then proposed. Each AF controller is tuned at the 2nd, 3rd and 4th modes, respectively. Their parameters were determined to remain the system to be stable based on the results of the parametric study. A significant reduction in vibration at the 3 modes can be obtained.

• 한국공간구조학회논문집
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• 제18권3호
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• pp.75-82
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• 2018

Large space structures exhibit different natural vibration characteristics depending on the aspect ratio of structures such as half-open angle. In addition, since the actual large space structure is mostly supported by the lower structure, it is expected that the natural vibration characteristics of the upper structure and the entire structure will vary depending on the lower structure. Therefore, in this study, the natural vibration characteristics of the dome structure are analyzed according to the natural frequency ratio by controlling the stiffness of the substructure. As the natural frequency of the substructure increases, the natural frequency of the whole structure increases similarly to the natural frequency of the upper structure. Vertical vibration modes dominate at $30^{\circ}$ and $45^{\circ}$, and horizontal vibration modes dominate at $60^{\circ}$ and $90^{\circ}$.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.71-74
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• 2008

In order to resolve the problems which appear after the clean large ingot production process, the impurities which are involved in the steel smelting process should be removed by developing cleaner materials. Through the rationalization of cogging process that is the first forging process of large ingot the quality is to be improved. For the sake of the optimization of an open die forging process and the improvement of the subject matter frequency ratio, a hazard precise die forging process must be developed and a Near Net Shape Forming accomplished. As a result, energy can be reduced by minimizing an after control process. In order to produce large axes and other forming parts, processing techniques are to be developed. In this context, this paper is a study about a reduction ratio, dies width ratio and rotary angles, the amount of overlap, and intends to analysis cogging processes, utilizing Deform-3D cogging module