• 소음진동
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• 제8권2호
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• pp.324-330
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• 1998

The forced vibration analysis of the outer-clamped spinnig annular disk with arbitrary in-plane is formulated to investigate the influence of non-uniform tension on the cutting accuracy of wafer cutting machine. The arbitrary in-plan force along the outer edge of an annular plate is expressed as a Fourier series. Galerkin method and modal superposition method are employed to obtain the forced responses under the static force and the impulse force in astationary coordinate. Through qualitative and quantitative analyses, it can be found that forced and impulse responses are sensitive to the non-uniformity of in-plane force, which can bring a bad effect to the accuracy of wafer cutting process. Also, in case of a spinning disk with non-uniform in-plane force, critical speed is required to define in a different way, compared with conventional definition in axi-symmetrical spinning disk.

• 소음진동
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• 제9권3호
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• pp.587-592
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• 1999

Piston slap is one of the sources producing engine block surface vibration and mechanical noise. To analyze piston slap-induced vibration, a realistic but simple model is proposed and verified experimentally. A piston is modeled by 3 degree of freedom system and an impact point between piston skirt and cylinder wall by 2 degree of freedom system. Numerical simulation estimates impact forces of piston in cylinder, and the engine block surface vibration response is predicted by the convoluton of the impact forces with measured impulse responses. Experimental verification on the predicted response has been also performed by using a commercial 4-cylinder diesel engine. the predicted and experimental vibration responses confirm that the suggested model is practically useful.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 IWAIT
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• pp.825-829
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• 2009

In this paper, we examine the fundamental performance of image coding schemes based on multipulse model. First, we introduce several kinds of pulse search methods (i.e., correlation method, pulse overlap search method and pulse amplitude optimization method) for the model. These pulse search methods are derived from auto-correlation function of impulse responses and cross-correlation function between host signals and impulse responses. Next, we explain the basic procedure of multipulse image coding scheme, which uses the above pulse search methods in order to encode the high frequency component of an original image. Finally, by means of computer simulation for some test images, we examine the PSNR(Peak Signal-to-Noise Ratio) and computational complexity of these methods.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 전력전자학술대회 논문집
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• pp.411-414
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• 2002

This paper proposed new techniques of rotor position detection for Switched Reluctance Motor(SRM). This technique is very simple and easy to find out rotor position. The main idea uses the impulse responses which have different values between aligned and unaligned. In order to obtain the rotor position, the Impulse applied to the unenergized phases and their responses are analized to control the speed of SRM without shaft sensor, Experimental results verify the feasibility of the proposed method.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1998년도 창립기념 춘계학술대회 논문집
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• pp.525-532
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• 1998

In this study, dynamic characteristics of catenary that supplies electrical power to high-speed trains is investigated. A particular emphasis is placed on the effect of droppers on the dynamic response of the contact wire, a dropper is an element that connects the contact wire with the messenger wire so as to maintain near uniform compliance, Finite element model compressing 3 spans is constructed. For the linear model, droppers are modeled as linear springs with various stiffness values. Modal analysis is performed to obtain the natural frequencies and modes and the variation in the modal density distribution for changing stiffness values are noted. Impulse response is also obtained through computer simulation. In practice, dropper is a nonlinear element with low stiffness in compression and high stiffness in tension. Hence, dropper can be modeled as a nonlinear spring with hi-directional stiffness values. Impulse and harmonic responses are obtained for the nonlinear model through simulation. The responses aye also compared with the linear cases.

• East Asian Economic Review
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• 제25권1호
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• pp.73-97
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• 2021

China has experienced many structural changes in the process of economic development over the past three decades. Using a time-varying parameter VAR model with stochastic volatility and mixture innovations, this study investigates whether such structural changes in, especially tools and operational aims of monetary policy, affect the monetary transmission mechanism. We find that impulse responses of output growth and inflation to monetary shocks have substantially increased and then reversed to decrease around 2005-2006. This time variation is mainly caused by changes in the monetary transmission mechanism, i.e., the manner in which main macroeconomic variables respond to policy shocks, rather than by changes in volatilities of exogenous shocks. The result implies that aggressive monetary policy to facilitate economic growth in the developing economies may be legitimized, unless it causes inflation seriously.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1986년도 하계학술대회논문집
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• pp.140-144
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• 1986

In this paper an FIR(finite impulse response) filter and smoother are introduced for discrete time-invariant state-space models with driving noises. The FIR structure not only quarantees the BIBO stability and the robustness to parameter changes but also improves the filter divergence problem. It is shown that the impulse responses of the FIR filter and the smoother are obtained by Riccati-type difference equations and that they are to be time-invariant and reduced to very simple forms. For implementational purpose, recursive forms of the FIR filler and smoother are derived with each other used as the adjoint variable.

• Tribology and Lubricants
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• 제16권4호
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• pp.295-301
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• 2000

The dynamic simulation of slider in hard disk drive is performed using Factored Implicit Finite Difference method. The modified Reynolds equation with Fukui and Kaneko model is employed as a governing equation. Equations of motion for the slider of three degrees of freedom are solved simultaneously with the modified Reynolds equation. The transient responses of the slider for disk step bumps and slider impulse forces are shown for various cases and are compared for the iteration algorithm and new algorithm.

• 한국항만경제학회지
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• 제19권2호
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• pp.55-67
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• 2003

The purpose of this study is to estimate and forecast the marine trading volumes based on the structural model. We employ GPH cointegration test since the structural model must be stationary to get the accurate predicted values. The empirical results show that our model is stationary. This paper also applies variance decompositions and impulse-response functions to the structural model composed of exchange rate, domestic industrial activity, and world business. The results indicate that while both loading and unloading volumes respond positively to the shocks in income and then decay very slowly, their responses are different to the shocks in exchange tate.

• 복식문화학회:학술대회논문집
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• 복식문화학회 2005년도 Joint International Conference
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• pp.183-185
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• 2005