• Coupled systems mechanics
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• 제2권1호
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• pp.111-126
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• 2013

The structural design requirements of an offshore platform subjected to wave induced forces and moments in the jacket can play a major role in the design of the offshore structures. For an economic and reliable design; good estimation of wave loadings are essential. A nonlinear response analysis of a fixed offshore platform under structural and wave loading is presented, the structure is discretized using the finite element method, wave plus current kinematics (velocity and acceleration fields) are generated using 5th order Stokes wave theory, the wave force acting on the member is calculated using Morison's equation. Hydrodynamic loading on horizontal and vertical tubular members and the dynamic response of fixed offshore structure together with the distribution of displacement, axial force and bending moment along the leg are investigated for regular and extreme conditions, where the structure should keep production capability in conditions of the 1-yr return period wave and must be able to survive the 100-yr return period storm conditions. The result of the study shows that the nonlinear response investigation is quite crucial for safe design and operation of offshore platform.

• Advances in biomechanics and applications
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• 제1권4호
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• pp.227-237
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• 2014

The in vitro construction of osteo-articular large implants combining biomaterials and cells is of great interest since these tissues have limited regeneration capability. But the development of such organoids is particularly challenging, especially in the later time of the culture, when the extracellular matrix has almost filled the initial porous network. The fluid flow needed to efficiently perfuse the sample can then not be achieved using only the hydraulic driving force. In this paper, we investigate the interest of using an electric field to promote mass transport through the scaffold at the late stage of the culture. Based on the resolution of the electrokinetics equations, this study provides an estimation of the necessary electric driving force to reach a sufficient oxygen perfusion through the sample, thus analyzing the feasibility of this concept. The possible consequences of such electric fields on cellular activities are then discussed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.1000-1003
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• 2014

The primary purpose of this study is to observe the dynamic behavior within a vehicle on chassis dynamometer throughout cleat impact testing with two different constraining setups (Tie-down strap and one point fixation). Throughout this empirical experiment, no outstanding dynamic behavior characteristics are observed between two setups and thus, the performance of the one point fixation device is validated. Neither the interior noise nor acceleration at driver seat rail and knuckle is heavily influenced by two different constraining methods. However, one point fixation is far more advantageous considering its shorter set up time and its capability of measuring traction force with its built in force sensor.

• Structural Engineering and Mechanics
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• 제28권3호
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• pp.335-352
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• 2008

Continuous operation of test and measurement is a new operating technique in the petroleum exploitation, which combines perforation with test and measurement effectively. In order to measure the original pressure of stratum layer exactly and prevent testing instrument from being impaired or damaged, a suitable shock absorber is urgently necessary to research. Based on the attempt on the FEM analysis and experiment research, a new shock absorber is designed and discussed in this paper. 3D finite element model is established and simulated accurately by LS-DYNA, the effect and the dynamic character of the shock absorber impact by half sinusoidal pulse force under the main lobe frequency are discussed both on theoretics and experiment. It is shown that the new designed shock absorber system has good capability of shock absorption for the impact load.

• Journal of Power Electronics
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• 제15권1호
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• pp.235-245
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• 2015

This paper proposes a reactive current assignment and control strategy for a doubly-fed induction generator (DFIG) based wind-turbine generation system under generic grid voltage sag or swell conditions. The system's active and reactive power constrains during grid faults are investigated with both the grid- and rotor-side convertors (GSC and RSC) maximum ampere limits considered. To meet the latest grid codes, especially the low- and high-voltage ride-through (LVRT and HVRT) requirements, an adaptive reactive current control scheme is investigated. In addition, a torque-oscillation suppression technique is designed to reduce the mechanism stress on turbine systems caused by intensive voltage variations. Simulation and experiment studies demonstrate the feasibility and effectiveness of the proposed control scheme to enhance the fault ride-through (FRT) capability of DFIG-based wind turbines during violent changes in grid voltage.

• BMB Reports
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• 제52권10호
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• pp.589-594
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• 2019

Single-molecule techniques have been used successfully to visualize real-time enzymatic activities, revealing transient complex properties and heterogeneity of various biological events. Especially, conventional force spectroscopy including optical tweezers and magnetic tweezers has been widely used to monitor change in DNA length by enzymes with high spatiotemporal resolutions of ~nanometers and ~milliseconds. However, DNA metabolism results from coordination of a number of components during the processes, requiring efficient monitoring of a complex of proteins catalyzing DNA substrates. In this min-review, we will introduce a simple and multiplexed single-molecule assay to detect DNA substrates catalyzed by enzymes with high-throughput data collection. We conclude with a perspective of possible directions that enhance capability of the assay to reveal complex biological events with higher resolution.

• Strategy21
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• 통권41호
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• pp.52-84
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• 2017

After finishing Cold War, the U.S. Navy's ability to Sea control has been gradually eroded last 15-20 years. The global security environment demands that the surface Navy rededicate itself to sea control, as a new group of potential adversaries is working to deny U.S. navy command of the sea. China has been increasing their sea denial capability, such as extended anti-surface cruise missile and anti-surface ballistic missile. To cope with this situation, the U.S. Naval Surface Forces Command has announced Surface Forces Strategy: Return to Sea Control. It is a new operating and organizing concept for the U.S. surface fleet called 'distributed lethality'. Under distributed lethality, offensive weapons such as new ASCMs are to be distributed more widely across all types of Navy surface ships, and new operational concept for Navy surface fleet's capability for attacking enemy ships and make it less possible for an enemy to cripple the U.S. fleet by concentrating its attack on a few very high-value Navy surface ships. By increasing the lethality of the surface ships and distributing them across wide areas, the Navy forces potential adversaries to not only consider the threat from our carrier-based aircraft and submarines, but they now consider the threat form all of those surface ships. This idea of using the distributed lethality template to generate surface action groups and adaptive force package and to start thinking about to increase the lethal efficacy of these ships. The U.S. Navy believes distributed lethality increases the Navy's sea control capability and expands U.S. conventional deterrence. Funding new weapons and renovated operating concept to field a more lethal and distributed force will enable us to establish sea control, even in contested area. The U.S. Navy's Surface Forces Strategy provides some useful implications for The ROK Navy. First the ROK Navy need to reconsider sea control mission. securing sea control and exploiting sea control are in a close connection. However, recently the ROK Navy only focuses on exploiting sea control, for instance land attack mission. the ROK Navy is required to reinvigorate sea control mission, such as anti-surface warfare and anti-air warfare. Second, the ROK Navy must seek the way to improve its warfighting capability. It can be achieved by developing high-edge weapons and designing renewed operating concept and embraced new weapon's extended capabilities.

• 산업기술연구
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• 제13권
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• pp.71-80
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• 1993

To analyze dynamic characterics for a motorcar, the creating and the hammering test methods are introduced. This paper has studied the method of computing the natural frequency of the impulse wave on a tire, the decay constant which determines the absorption capability for the impulsive force. Moreover we have examined the reliability for the decay constant calculated, in this paper theoritical results are agreed with the simulated ones.

• Architectural research
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• 제14권4호
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• pp.143-152
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• 2012

A form-finding procedure is presented for planar tensegrity structures. Notably, a simple decision criteria is proposed to select the desirable candidate position vector from the unitary matrix produced by the eigenvalue decomposition of force density matrix. The soundness of the candidate position vector guarantees faster convergence and produces a desirable form of tensegrity without any member having zero-length. Several numerical examples are provided to demonstrate the capability of the proposed form-finding process.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.1008-1013
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• 1992

본 논문에서는 다중 로보느의 협조제어(Coordinated Control)를 위한 로보트 콘트롤러의 설계에 대해서 연구한다. 첫 부분에서는 다중 로보느의 연구배경 및 연구동기에 대해서 논의하고 이어서 Coordinated Task를 묘사하기 위한 Programming Primiitive Set을 정의하며 구현에 대해서도 논의한다. 특히 Motopn Primitive는 synchronous(Coordinated Motion), Asynchronous Motion, Conditional Motion, 특수 Motion으로 분류하고, 각각의 궤적계획 및 구현에 대해서도 간단히 논의한다. 특히 본 논문에서는 외부의 변화하는 환경에 효과적으로 적응할 수 있게 하기 위하여 Vision센서, Encoder신호와 Limit센서, Force센서 등의 다양한 외부 센서를 융합 처리할수 있는 다중 로보트 제어 시스템을 개발하였다.