• 한국생산제조학회지
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• 제9권1호
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• pp.88-95
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• 2000

In this paper, an expansion-resonator type pulsation attenuator is proposed to absorb and attenuate flow an pressure ripple with high frequencies generated from hydraulic control systems. The basic principle of a pulsation attenuator proposed here is applied to propagation, reflection, absorption of pressure waves at the cross section of discontinuity and resonance in the pipeline. It has advantage of the compact size and high degree fo freedom for installation in hydraulic systems. The design scheme based on distributed parameter pipeline system with dissipative viscous compressible model is developed. To investigate the reduction of flow and pressure ripple with high frequencies produced by swash plate type axial piston pump, two kinds of attenuators are manufactured. It is experimently confirmed that the spectral intensity of flow and pressure ripple with high frequencies from the pump are reduced up to about 20$^{\circ}$~30dB by using attenuators proposed here. The calculated results were in good agreement with the measured values. From there sults of this study, it is shown that an expansion-resonator type pulsation attenuator is effective in a wide frequency ranges to attenuate the flow and pressure ripple from hydraulic components.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권7호
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• pp.1638-1656
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• 2013

The demand for multimedia streaming services is increasing rapidly. To meet this demand, there has been much research and many practical developments for providing multimedia services. A push-to-talk (PTT) service is one of the multimedia streaming services that have been deployed not only over IP multimedia subsystem (IMS) but also in peer-to-peer (P2P) overlay networks. The benefit of PTT has been demonstrated in the literature. However, the need for using PTT service in communication can be arbitrary among users, regardless what kind of PTT services they use. This demand does not support current PTT systems, so an expansion of PTT services still be limited. Moreover, the combination of PTT services in IMS and P2P networks will help operators to provide more scalable PTT services. Therefore, in this paper, we proposed a model to support PTT service interworking between IMS and P2P overlay networks. We also introduced our system design and some interworking service scenarios. We confirmed our architecture through implementation and testing.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1995년도 추계 학술대회논문집
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• pp.160-168
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• 1995

This paper describes computational efforts on the various energy and environmental problems using Patankar's SIMPLE method. The specific problems included in this study are : pollutant and flammable material dispersions in open and confined areas, aerator-induced flow in a lake for DO(dissolved oxygen) concentration, primary clarifier for water and waste water treatment, hood ventilation in workplace, cyclone and LNG combustors and Dow chlorination reactor. A control-volume based finite-difference method is employed together with the power-law scheme. The pressure-velocity coupling is resolved by the use of the revised version of SIMPLE, says SIMPLER and SIMPLEC. The Reynolds stresses are closed using the standard or the RNG $k-{\varepsilon}$ models. Turbulent reaction is modeled using two fast chemistry methods such as eddy breakup and conserved scalar models. Further, a nonequilibrium model is developed for the application of the chlorination process in the Dow reactor. Other important empirical models and physical insights appeared in this study are presented and discussed in a brief note. The computational method developed in this study is considered, in general, as a viable tool for the design and determination of the optimal condition of various engineering system of interest.

• 한국전산유체공학회지
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• 제2권1호
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• pp.93-108
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• 1997

This paper describes several computational results on the various energy and environmental problems using Patankar's SIMPLE method. The specific problems included in this study are : pollutant and flammable material dispersions in open and confined areas, buoyancy-driven flow in a lake, primary clarifier for water and waste water treatment, hood ventilation in workplace. cyclone combustor and Dow chlorination reactor. A control-volume based finite-difference method is employed together with the power-law scheme. The pressure-velocity coupling is resolved by the use of the revised version of SIMPLE, says SIMPLER and SIMPLEC. The Reynolds stresses are closed using the standard or RNG κ-ε models. A nonequilibrium turbulent reaction model is developed for the application of the chlorination process in the Dow thermal reactor. Other important empirical models and physical insights appeared in this study are presented and discussed in a brief note. The computational method developed in this study is considered, in general, as a viable tool for the design and determination of the optimal operating condition of various environmental engineering system of interest.

• Smart Structures and Systems
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• 제18권4호
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• pp.787-800
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• 2016

The aim of the paper is to analyze nonlinear transverse vibration of an embedded piezoelectric plate reinforced with single walled carbon nanotubes (SWCNTs). The system in rested in a Pasternak foundation. The micro-electro-mechanical model is employed to calculate mechanical and electrical properties of nanocomposite. Using nonlinear strain-displacement relations and considering charge equation for coupling between electrical and mechanical fields, the motion equations are derived based on energy method and Hamilton's principle. These equations can't be solved analytically due to their nonlinear terms. Hence, differential quadrature method (DQM) is employed to solve the governing differential equations for the case when all four ends are clamped supported and free electrical boundary condition. The influences of the elastic medium, volume fraction and orientation angle of the SWCNTs reinforcement and aspect ratio are shown on frequency of structure. The results indicate that with increasing volume fraction of SWCNTs, the frequency increases. This study might be useful for the design and smart control of nano/micro devices such as MEMS and NEMS.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2005년도 전력전자학술대회 논문집
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• pp.134-136
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• 2005

The author present a modified multi-loop algorithm Including feedforward for controlling a 55kW stepdown chopper in the power supply of Maglev The gains of the control algorithm were selected based on pole locations formulated from a prototype Bessel transfer function model. The design incorporate tradeoffs in DC-to-DC converter hard-ware para-meters and pole locations. This perturvation is derived by subtracting the desired output voltage from the actual output voltage. The proportional and integral action stabilizes the system and minimizes output voltage error. In order to verify the validity of the proposed multi-loop controller, simulation study was tried using Matlab simulink.

• 한국물환경학회지
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• 제29권6호
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• pp.730-738
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• 2013

In recent years, low impact development (LID) has emerged as an effective approach to control stormwater in an urban area, and watershed and stormwater managers need modeling tools to evaluate alternative plans for controlling stormwater. This study illustrates how to design and evaluate the effect of non-point pollutant management using SUSTAIN which is developed by USEPA. SUSTAIN can provide evaluating, selecting, and placing LID facilities in an urban catchment based on user-defined cost-effectiveness criteria. Also, this paper suggests a minimal methodology for estimating model parameters for modeling an ungauged urban catchment to reflect the situation of typical Korean urban interested catchments which are usually ungauged. In addition, the optimal length of various LID facilities and the optimal number of units in our test catchment are estimated.

• 한국지능시스템학회논문지
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• 제8권5호
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• pp.51-60
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• 1998

퍼지 시스템의 안정도와 퍼지 제어기의 설계 방법론에 관한 연구는 최근 들어 많은 주목을 받아왔다. 본 논문은 TS(Takagi-Sugeno) 퍼지 모델로 표현된 비선형 시스템에 대한 제어기 설계분제가 선형행렬부등식(LMI, linear matrix inequality)을 포함하는 convex 문제로 간략화됨을 보인다. 입력행렬의 구조에 따라서 TS 퍼지 시스템을 세 가지로 분류하고, 각각에 대해 선형행렬부등식을 이용한 제어기 설계 방법을 제시한다. 또한 안정도 이외의 성능용건을 고려한 제어기를 설계한다. 제안된 설계 방법론을 설명하기 위해 예제를 다룬다.

• 한국공간구조학회논문집
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• 제19권1호
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• pp.109-116
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• 2019

In this paper, the shape adjustment algorithm of the spoked wheel cable structures with retractable membrane system is studied. The initial tension of the membrane or cable is necessary to form the structure and its value is determined by the design shape. However, due to internal and external environmental influences, its shape may be different from the initial designed shape. In the case of the cable structures covered in this study, tension adjustment is necessary to maintain the designed shape because it influences the tension of the cable depending on the state of the retractable membrane. Therefore, we proposed an adjustment algorithm of an initial shape based on the force method. The effectiveness and validity of the methodology were examined through the applicable cable structures. The results of the shape adjustment analysis of the symmetric spoked wheel cable model were reliable and accurate results were obtained.

• 한국해양공학회지
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• 제33권6호
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• pp.590-596
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• 2019

Numerous deaths and substantial property damage have occurred recently due to frequent disasters of the highest intensity according to the abnormal climate, which is caused by various problems, such as global warming, all over the world. Such large-scale disasters have become an international issue and have made people aware of the disasters so they can implement disaster-prevention measures. Extensive information on disaster prevention actively has been announced publicly to support the natural disaster reduction measures throughout the world. In Japan, diverse developmental studies on disaster prevention systems, which support hazard map development and flood control activity, have been conducted vigorously to estimate external forces according to design frequencies as well as expected maximum frequencies from a variety of areas, such as rivers, coasts, and ports based on broad disaster prevention data obtained from several huge disasters. However, the current reduction measures alone are not sufficiently effective due to the change of the paradigms of the current disasters. Therefore, in order to obtain the synergy effect of reduction measures, a study of the establishment of an integrated system is required to improve the various disaster prevention technologies and the current disaster prevention system. In order to develop a similar typhoon search system and establish a disaster prevention infrastructure, in this study, techniques will be developed that can be used to forecast typhoons before they strike by using artificial intelligence (AI) technology and offer primary disaster prevention information according to the direction of the typhoon. The main function of this model is to predict the most similar typhoon among the existing typhoons by utilizing the major typhoon information, such as course, central pressure, and speed, before the typhoon directly impacts South Korea. This model is equipped with a combination of AI and DNN forecasts of typhoons that change from moment to moment in order to efficiently forecast a current typhoon based on similar typhoons in the past. Thus, the result of a similar typhoon search showed that the quality of prediction was higher with the grid size of one degree rather than two degrees in latitude and longitude.