• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.11
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• pp.1077-1082
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• 2007

We present a micromechanical active amplifier, inspired from the principle of the outer hair cells in cochlea, amplifying both displacement and force. The present micromechanical active amplifier modulates the resonant carrier motion using the variable stiffness spring whose stiffness changes proportionally to the input motion. We design, fabricate, and characterize two types of the amplifiers A and B, each having the variable stiffness spring fur the maximum displacement gain and force gain, respectively. In the experimental study, the amplifier A shows the displacement gain of 5.62, which is 2.15 times larger than that of the amplifier 3. The amplifier B shows the force gain of 10.0, resulting in 1.26 times larger value compared to that of the amplifier A. We experimentally verify that the haircell-inspired micromechanical amplifiers are capable to amplify both displacement and force.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.4
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• pp.114-121
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• 2002

This paper describes the control system of the toroidal traction driver continuously variable-speed transmission(CVT) fur a tractor. The instrumentation system, the hydraulic power control system and the principle control scheme were introduced. Experimental tests in the bench and the tractor were conducted to validate the performance of the CVT utilizing the proposed controller. The speed of the vehicle was continuously changed to follow the speed set by driver under various operating conditions. Given the reduction ratio of the variator from 2.0 to 1.0, the settling time was about just 0.52 seconds which was satisfactory value for working with the tractor. It was also proved that the tractor could work with continuously variable speed under heavy load disturbances.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.3
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• pp.106-114
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• 2003

The pressure ripple in the delivery port is caused by flow ripple, which is induced by variation of pumping chamber volume. The other reason is the reverse flow from the outlet volume produced by pressure difference between pumping chamber and outlet volume, when the pumping chamber is connected with the outlet volume. In this study, a mathematical model is presented for analyzing discharge pressure ripple, which includes vane detachment, cam ring movement , and fluid inertia effects in V-groove in the side plate. From the analysis and experiment, it was found that V-groove on the side plate, coefficient of spring supporting the cam ring, and average discharge pressure are the main factors of discharge pressure ripple in variable displacement vane pump. The theoretical results, provided in this study, were well agreed with experimental results. The analytical model to estimate the magnitude of pressure ripple in this study is expected to be used f3r the optimal design of the variable displacement vane pump.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.7
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• pp.808-815
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• 2006

In this paper, we suggest decoupling control method based on general PI control law to control variable speed refrigeration system of the ship effectively. In the variable speed refrigeration system, the capacity and the superheat are controlled by inverters and electronic expansion valves respectively for saving energy and improving cost performance. Thus, we propose decoupling model to eliminate the interfering loop between capacity and superheat at first. Next, we design PI controller to control capacity and superheat independently and simultaneously. Finally the control performance was investigated through some experiments. The experimental results show that the PI control design can obtain good control performance under the adjustable control reference and thermal load variation.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.9
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• pp.100-108
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• 2003

This paper proposes a flywheel hybrid vehicle to solve the energy crisis problem by the exhaustion of a fossil fuel and air pollution for the conservation of environment. The proposed flywheel hybrid vehicle is composed of an accumulator and a flywheel as the energy generation and storage component and three variable displacement hydraulic pump/motors as the energy transfer devices. Flywheel has the characteristics of high energy density and easy energy absorption and consumption. The effectiveness of the energy-saving of the proposed flywheel hybrid vehicle is verified by simulation using Matlab/simulink. First of ail, analytical modeling for the flywheel hybrid vehicle is presented and simulations are performed based on the experimental efficiency data of a variable displacement pump/motor. The results of the simulation show that the effect of energy savings is realized by the proposed hybrid vehicle in 3 different city driving patterns.

• Proceedings of the KSPS conference
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• 2007.05a
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• pp.315-318
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• 2007

This paper proposes the methods to enhance the speech quality of source controlled variable bit-rate coder based on the waveform interpolation. The methods are to estimate and generate the parameters that are not transmitted from encoder to decoder by the repetition and extrapolation schemes. For the performance evaluation, the PESQ(Perceptual Evaluation of Speech Quality) scores are measured. The experimental results shows that our proposed method outperforms the conventional source controlled variable bit-rate coder. Especially, the performance of the extrapolation method is better than that of the repetition method.

• Journal of the Korean Wood Science and Technology
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• v.17 no.4
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• pp.35-43
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• 1989

Nailed joints, which are commonly used in Wooden structures, transmit loads from one member to another and induce partial composite actions between members. Long-term loads induce creep slip in nailed joints and affect load sharing and partial composite action, which may reduce joint stiffness. Two theoretical viscous-viscoelastic models were developed for nailed joints to predict creep behavior under long-term variable loads. Those models were also used to predict stiffness changes under long-term variable loads. The stiffness of nailed joint is defined as a Secant modulus which is called the joint modulus or slip modulus. Input data for the models are the results of constant load tests under three different load levels. To verify the models, nailed joints were also tested under two long-term variable load functions. The predictions of the models were very close to the experimental data. Therefore, the theoretical viscous-viscoelastic models and procedures developed in this study can be applied to predict creep slip and the changes in joint moduli of nailed joints under long-term variable loads.

• International Journal of Fluid Machinery and Systems
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• v.8 no.1
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• pp.13-22
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• 2015

This study presents a simulation model of a heat pump air conditioning system with a variable capacity compressor and variable speeds fans for electric bus. An experimental sample has been developed in order to check results from the model. Effects on system performance of such working conditions as compressor speed, evaporator fans speeds and the condenser fans speeds have been simulated by means of developed model. The results show that the three speeds can be adjusted simultaneously according to actual working condition so that the AC system can operate under the optimum state which the control objects want to achieve. It would be a good and simple solution to extend the driving ranges of EVs because of the highest efficiency and the lowest energy consumption of AC system.

• Journal of Power System Engineering
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• v.22 no.1
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• pp.18-24
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• 2018

This paper focuses on systematic design about the membership ranges of the main design factors such as control error, control error rate, and sampling time for the fuzzy logic control of the variable speed drive refrigeration cycle. The upper and the lowest limit of the membership ranges are set up from the data of static characteristics obtained by experiments. Three kinds of membership ranges on the control error and the control error rate are tested by experiments. Especially, an effect of sampling time on control performance is also investigated in the same way. Experimental data showed the control error rate and the sampling time strongly effected on the control performance of the refrigeration cycle with a variable speed drive.

• Journal of the Korean Data and Information Science Society
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• v.24 no.1
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• pp.201-209
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• 2013

For censored regression, it is often the case that some input variables are not important, while some input variables are more important than others. We propose a novel algorithm for selecting such important input variables for censored kernel regression, which is based on the penalized regression with the weighted quadratic loss function for the censored data, where the weight is computed from the empirical survival function of the censoring variable. We employ the weighted version of ANOVA decomposition kernels to choose optimal subset of important input variables. Experimental results are then presented which indicate the performance of the proposed variable selection method.