• 동력기계공학회지
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• 제19권6호
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• pp.33-38
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• 2015

In this study new CVT(Continuously Variable Transmission) system which is adaptable to a small size electric vehicle is proposed available to gradient response CVT. New pulleys consist of springs adapted driving pulley and driven pulley. At the moment a small electric vehicle drive a slope, new system respond to a gradient as overcoming tensional force of springs. We made prototype of gradient response CVT to test parts performance and travelling performance test. As a result of test, belt pitch diameter varied for high torque direction at the gradient. In the flat travelling, acceleration travelling and gradient travelling performance test, the small electric vehicle with gradient response CVT get improved perfomance than the small electric vehicle with reduction gear.

• Structural Engineering and Mechanics
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• 제15권6호
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• pp.705-716
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• 2003

Gradient elastic flexural beams are dynamically analysed by analytic means. The governing equation of flexural beam motion is obtained by combining the Bernoulli-Euler beam theory and the simple gradient elasticity theory due to Aifantis. All possible boundary conditions (classical and non-classical or gradient type) are obtained with the aid of a variational statement. A wave propagation analysis reveals the existence of wave dispersion in gradient elastic beams. Free vibrations of gradient elastic beams are analysed and natural frequencies and modal shapes are obtained. Forced vibrations of these beams are also analysed with the aid of the Laplace transform with respect to time and their response to loads with any time variation is obtained. Numerical examples are presented for both free and forced vibrations of a simply supported and a cantilever beam, respectively, in order to assess the gradient effect on the natural frequencies, modal shapes and beam response.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
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• pp.46-47
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• 2003

Direct numerical simulations are performed for a turbulent flow subjected to a sudden change in pressure gradient. The calculations are started from a fully-developed turbulent channel flow at $Re_{\tau}=180$. The pressure gradient of the channel flow is then changed abruptly. The responses of the turbulence quantities (e.g., turbulence intensities, Reynolds shear stress, and vorticity fluctuations) and the near-wall turbulence structure to the pressure gradient change are investigated. It is found that there are two different relaxations: a fast relaxation at the early stage and a slow one at the later stage. The early response of the velocity fluctuations shows an anisotropic response of the near-wall turbulence.

• The Korean Journal of Ecology
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• 제21권3호
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• pp.233-241
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• 1998

In order to test of intermediate disturbance hypothesis that an intermediate level of disturbance maximize biodiversity and to elucidate the effect of disturbance during the early old-field succession, the response of plant community along an experimental disturbance gradient was investigated in a five-year old-field. Response of plant community along an experimental disturbance gradient was connected with light condition because artificial disturbance gradient had been treat by clipping of plants and removing of litter. Artificial disturbance in five-year old-field plant community retarded rate of succession by increasing invasion and performance of the earlier successional species in the initial and middle stage of disturbance treatment. The species richness in the blocks of intermediate disturbance level showed the peak in early and mid-summer. This result did correspond with the prediction of intermediate disturbance hypothesis.

• Structural Engineering and Mechanics
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• 제68권1호
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• pp.103-119
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• 2018

In the present research, an attempt is made to obtain a semi analytical solution for both nonlinear natural frequency and forced vibration of embedded functionally graded double layered nanoplates with all edges simply supported based on nonlocal strain gradient elasticity theory. The interaction of van der Waals forces between adjacent layers is included. For modeling surrounding elastic medium, the nonlinear Winkler-Pasternak foundation model is employed. The governing partial differential equations have been derived based on the Mindlin plate theory utilizing the von Karman strain-displacement relations. Subsequently, using the Galerkin method, the governing equations sets are reduced to nonlinear ordinary differential equations. The semi analytical solution of the nonlinear natural frequencies using the homotopy analysis method and the exact solution of the nonlinear forced vibration through the Harmonic Balance method are then established. The results show that the length scale parameters give nonlinearity of the hardening type in frequency response curve and the increase in material length scale parameter causes to increase in maximum response amplitude, whereas the increase in nonlocal parameter causes to decrease in maximum response amplitude. Increasing the material length scale parameter increases the width of unstable region in the frequency response curve.

• Geomechanics and Engineering
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• 제7권6호
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• pp.679-703
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• 2014

This paper investigates nonlinear response of 51 laterally loaded rigid piles in sand. Measured response of each pile test was used to deduce input parameters of modulus of subgrade reaction and the gradient of the linear limiting force profile using elastic-plastic solutions. Normalised load - displacement and/or moment - rotation curves and in some cases bending moment and displacement distributions with depth are provided for all the pile tests, to show the effect of load eccentricity on the nonlinear pile response and pile capacity. The values of modulus of subgrade reaction and the gradient of the linear limiting force profile may be used in the design of laterally loaded rigid piles in sand.

• 감성과학
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• 제18권3호
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• pp.63-70
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• 2015

본 연구는 1/f fluctuation의 ${\alpha}$기울기 따라 구성된 사운드를 들었을 때 감정 스트레스 업무에 종사하고 있는 피험자들의 심박 변화를 확인하고자 하였다. 기존의 연구에서는 주로 사용자의 심리상태 안정시키는 효과 또는 생리적 안정성에 1/f fluctuation의 ${\alpha}$기울기가 관계가 있는 것으로 보고되었다. 본 연구에서는 1/f fluctuation 수준을 총 3가지 나누어 제작한 사운드를 독립변수로 사용하였다. 독립변수는 감정노동 종사자에게 제시하여 그에 따른 심장반응을 측정하였다. 종속변수는 네 가지로 BPM(Beat Per Minute), VLF(Very Low Frequency), SDNN(Standard Deviation of NN intervals), 그리고 HF(High Frequency) 파워(Power)값을 확인하였다. 분석결과 기울기가 3인 1/fluctuation 사운드는 각성효과를 보였다. 기울기 1, 2인 사운드는 이완효과가 있는 것을 통계적으로 검증하였다. 이러한 1/f fluctuation 사운드의 특성을 활용해 감정 노동자들의 스트레스를 완화시키기 위한 서비스에 응용될 수 있을 것으로 사료된다.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2001년도 Proceedings of 2001 Korea-Japan Joint Seminar on Particle Image Velocimetry
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• pp.14-22
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• 2001

The frequency responses on the sub-pixel evaluation technique were investigated using the Monte-calro Simulation technique. The frequency response by the FFT based cross-correlation gives very good results, however, the gain loss does exist for the small displacement, (less than 0.5 pixel). While, the no gain loss is observed in the Direct Cross-correlation, however, the sub-pixel accuracy was limited to be about 0.1 pixel, i.e., it could not detect the small displacement. To detect the higher accurate sub-pixel displacement, the gradient based technique is the best. For the small interrogation area (e.g., 4x4), only the gradient technique can detect the small displacement correctly.

• Advances in nano research
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• 제8권2호
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• pp.157-167
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• 2020

This paper studies forced vibrational behavior of porous nanocrystalline silicon nanoshells under radial dynamic loads using strain gradient theory (SGT). This type of material contains many pores inside it and also there are nano-size grains which define the material character. The formulation for nanocrystalline nanoshell is provided by first order shell theory and a numerical approach is used in order to solve nanoshell equations. SGT gives a scale factor related to stiffness hardening provided by nano-grains. For more accurate description of size effects due to nano-grains or nano-pore, their surface energy influences have been introduced. Surface energy of inclusion exhibit extraordinary influence on dynamic response of the nanoshell. Also, dynamic response of the nanoshell is affected by the scale of nano-grain and nano-pore.

• 제어로봇시스템학회논문지
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• 제18권12호
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• pp.1101-1105
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• 2012

This study proposes a method for improvement of PD type fuzzy controller. The method includes self tuner using gradient algorithm that is one of the optimization algorithms. The proposed controller improves simple Takagi-Sugeno type FLC (Fuzzy Logic Control) system. The simple Takagi-Sugeno type FLC system changes nonlinear characteristic to linear parameters of consequent membership function. The simple FLC system could control the system by calibrating parameter of consequent membership function that changes the system response. While the determination on parameter of the simple FLC system works well only partially, the proposed method is needed to determine parameters that work for overall response. The simple FLC system doesn't predict the response characteristics. While the simple FLC system works just like proportional part of PID, our system includes derivative part to predict the next response. The proposed controller is constructed with P part and D part FLC system that characteristic parameter on system response is changed by self tuner for effective response. Since the proposed controller doesn't include integral part, it can't eliminate steady state error. So we include a gain to eliminate the steady state error.