• Journal of Advanced Marine Engineering and Technology
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• v.13 no.1
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• pp.77-96
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• 1989

In diesel engines, it is inevitable that the torsional vibration is produced by the fluctuation of engine torque. Therefore, if the occurence of torsional vibration is confirmed in the design stage or the torsional vibration is observed on the bed of test run, it is necessary to establish some preventive measures to avoid dangerous conditions. Major preventive measures are as follows : 1. Changing the natural frequency of shaft system. 2. Repressing the vibration amplitude by the damping energy. 3. Counterbalancing the exciting torque by the resistant torque. 4. Counterbalacing the harmonic component of exciting energy. In above methos, the damper is the last measure to be used for controlling the torsional vibration. In this thesis, the design of viscous damper that absorbs the exciting energy is investigated and a number of problems associated with the design of viscous damper are treated and a computer pregram for the process of damper design is developed. A viscous damper for a high speed diesel engine is designed and its effect is simulated by the author's computer program.

• Journal of Electrical Engineering and Technology
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• v.8 no.3
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• pp.565-571
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• 2013

This paper presents an effective method to improve efficiency of switched reluctance motor by optimizing energy conversion loop. A nonlinear analytical model which takes saturation account is developed to calculate inductance and flux-linkage. The flux-linkage curve is studied to calculate the co-energy increment to obtain the optimum exciting current. For a given cross-section, the exciting current at which co-energy increment is maximum was found to be constant while stack length varies. Then the energy conversion loop was optimized by varying the stack length and turns of windings. The constraints during optimization were that motor was excited by the maximum increment co-energy current and the energy in the loop was determined by rated power of motor. Dynamic finite element analysis was used to evaluate the efficiency of various models and the comparison of results shows promising effects of the proposed method. Experiment was also conducted to validate the simulation result.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1999.05a
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• pp.133-138
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• 1999

바람의 변화가 심한 풍력발전에 응용하기 위한 발전기는 동기속도 이상과 이하에서 발전이 가능하여야 한다. DFIG(Doubly Fed Induction Generator) 시스템의 경우 회전자 여자제어를 통한여 운전점을 이동시킬 수 있으며, 이를 통하여 운전영역의 확장이 가능하고 동기속도의 이상과 이하의 범위에서 발전이 가능하다.(중략)

• Bulletin of the Korean Chemical Society
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• v.16 no.10
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• pp.972-976
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• 1995

A trace amount of 4-biphenylcarboxylate having a pre-twisted biphenyl moiety was attached to a poly(methyl methacrylate) side chain and the fluorescence properties of the chromophore were investigated in various solvents such as ethyl acetate and butyl chloride. At room temperature, the polymer exhibited a distinct red shift of the short wavelength emission (325 nm) and an enhanced emission intensity around 430 nm upon excitation at the absorption red edge. The temperature dependence of the intensity ratio (R) of the 325 nm emission to the 430 nm emission was observed when exciting at the red edge over the temperature range between -20 and 60 ℃. However, the temperature dependence was not observed when exciting at the shorter wavelength. The Arrhenius plot of the R value shows the activation energy of 6.0 kJ/mol which is in good agreement with the energy required for the twist of the biphenyl moiety. Together with the results of red edge excitation effects it was concluded that the pre-twisted geometry of the biphenyl moiety is preserved by the restriction of the polymer chain to facilitate the formation of the twisted intramolecular charge transfer (TICT) state upon excitation.

• Journal of the Korean Professional Engineers Association
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• v.34 no.5
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• pp.34-39
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• 2001

Seoul World Cup Stadium is created as a state-of-the-art versatile World Cup stadium. In order to ensure that the 2002 World Cup will be a successful and exciting sports and cultural event that will draw world class athletes, millions of spectators, and organizers from all around the world. And various facilities will be established in the Seoul World Cup Stadium that will allow the citizens to use the stadium for a wide range of exciting sports, cultural and social activites. The Building Services of Seoul World Cup Stadium is planned by placing emphasis on building maintenance and energy saving, considering the characteristics of state-of-the-art versatile World Cup Stadium and various facilities after the World Cup 2002

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.12
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• pp.999-1006
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• 2014

Mindlin plate theory includes the shear deformation and rotatory inertia effects which cannot be negligible as exciting frequency increases. The statistical methods such as energy flow analysis(EFA) and statistical energy analysis(SEA) are very useful for estimation of structure-borne sound of various built-up structures. For the reliable vibrational analysis of built-up structures at high frequencies, the energy transfer relationship between out-of-plane waves and in-plane waves exist in Mindlin plates coupled at arbitrary angles must be derived. In this paper, the new wave transmission analysis is successfully performed for various energy analyses of Mindlin plates coupled at arbitrary angles.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.789-794
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• 2008

The damage identification in a flexible system requires modal informations which is represented by FRF(Frequency response function) or modal parameters. In this paper, energy isoclines are introduced to access the prediction of fatigue damage on a flexible component exposed mainly to the exciting source rather than external forces. After deriving the concerned function, energy isoclines, from the investigation of the relationship between energy and damage, its practical application is explained by the simple uni-axial excitation test for the notched round bar.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.246-251
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• 2003

This paper presents an experimental study on the energy dissipation characteristics of viscous damping wall (VDW). VDW is consisted of a plate floating in a thin case made of steel plated filled with highly viscous silicone oil. Because VDW demonstrates both viscous damping and stiffness characteristics, the viscous resisting force can be expressed as the sum of velocity dependant viscous damping force and displacement dependant restoring force. The viscous resisting force and energy absorbing capacity can be easily adjusted by changing three factors, i.e. viscosity of the fluid, gap distance and area of the wall plates. VDW was tested using a series of harmonic (sinusoidal) displacement history having different frequency and amplitude and the force-displacement relationship was recorded. The relationship between dissipated energy with three factors and the influence of exciting frequency on resisting force were Investigated

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.135.1-135.1
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• 2014

Silicon nanoparticles can be synthesized in a standard radio-frequency glow discharge system at low temperature (${\sim}200^{\circ}C$). Plasma synthesis of silicon nanoparticles, initially a side effect of powder formation, has become over the years an exciting field of research which has opened the way to new opportunities in the field of materials deposition and their application to optoelectronic devices. Hydrogenated polymorphous silicon (pm-Si:H) has a peculiar microstructure, namely a small volume fraction of plasma synthesized silicon nanoparticles embedded in an amorphous matrix, which originates from the unique deposition mechanism. Detailed discussion on plasma synthesis of silicon nanoparticles, growth mechanism and photovoltaic application of pm-Si:H will be presented.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.11B no.3
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• pp.59-63
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• 2001

This paper presents a new modeling of the two dimensional magnetic property in soft magnetic materials for the magnetic field computations. In this modeling an approximate treatment is introduced to expand the applicable exciting frequency range. The result shows that the new modeling presented here is very useful in simplicity of magnetic field analysis.