• Ocean Systems Engineering
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• v.10 no.4
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• pp.359-371
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• 2020

The performance of a multi-level overtopping wave energy converter (OWEC) has been numerically and experimentally investigated in a two-dimensional wave tank in order to study the effects of opening width of additional reservoirs. The device is a fixed OWEC consisting of an inclined ramp together with several reservoirs at different levels. A particle-based numerical simulation utilizing the Lattice Boltzmann Method (LBM) is used to simulate the flow behavior around the OWEC. Additionally, an experimental model is also built and tested in a small wave flume in order to validate the numerical results. A comparison in energy captured performance between single-level and multi-level devices has been proposed using the hydraulic efficiency. The enhancement of power capture performance is accomplished by increasing an overtopping flow rate captured by the extra reservoirs. However, a noticeably large opening of the extra reservoirs can result in a reduction in the power efficiency. The overtopping flow behavior into the reservoirs is also presented and discussed. Moreover, the results of hydrodynamic performance are compared with a similar study, of which a similar tendency is achieved. Nevertheless, the LBM simulations consume less computational time in both pre-processing and calculating phases.

• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.5
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• pp.651-659
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• 2018

A multi-level overtopping wave energy converter was designed according to the large tidal range and small wave heights in China. It consists of two reservoirs with sloping walls at different levels. The reservoirs share a common outflow duct and a low-head axial turbine. The experimental study was carried out in a laboratory wave-flume to investigate the overtopping performance of the device. The depth-gauges were used to measure the variation of the water level in the reservoirs. The data was processed to derive the time-averaged overtopping discharges. It was found that the lower reservoir can store wave waters at the low water level and break the waves which try to climb up to the upper reservoir. The upper sloping angle and the opening width of the lower reservoir both have significant effects on the overtopping discharges, which can provide more information to the design and optimization of this type of device.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.819-824
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• 2008

Energy consumption in Korea and Japan has already progressed to high level. Especially, it will be important to take up the effort to achieve further energy savings in residential sector that has significant increase both nations. For this reason, research for energy consumption and saving method in residential sector compare Korea with Japan that of similar data to grasps the direction for energy savings. In addition for introduction of distributed energy system to residential sector, such as apartment house, the electricity and gas demand was simulated. To be more specific, several key characteristics were studied, such as housing type housing scale and width of common space.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.1
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• pp.413-435
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• 2018

Although the accuracy of handwritten character recognition based on deep networks has been shown to be superior to that of the traditional method, the use of an overly deep network significantly increases time consumption during parameter training. For this reason, this paper took the training time and recognition accuracy into consideration and proposed a novel handwritten character recognition algorithm with newly designed network structure, which is based on an extended nonlinear kernel residual network. This network is a non-extremely deep network, and its main design is as follows:(1) Design of an unsupervised apriori algorithm for intra-class clustering, making the subsequent network training more pertinent; (2) presentation of an intermediate convolution model with a pre-processed width level of 2;(3) presentation of a composite residual structure that designs a multi-level quick link; and (4) addition of a Dropout layer after the parameter optimization. The algorithm shows superior results on MNIST and SVHN dataset, which are two character benchmark recognition datasets, and achieves better recognition accuracy and higher recognition efficiency than other deep structures with the same number of layers.

• The Journal of the Convergence on Culture Technology
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• v.3 no.1
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• pp.43-48
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• 2017

We are confirmed to the variation of the transfer condition and the functional penetration by the permitted conversion energy on the skin. The given conversion energy is consist of the flow level of penetration control and go to the processing transfer in the skin that is to create the modeling for algorithm. The energy level of control processing was achieved effectively modeling system that was the composition of auto and local control level in the epidermis-dermis layer. Their penetration pulse control system was consisted of conversion energy with reference of fixing situation and recreation of designed apparatus for the energy control function that was converted to capacity by the size, form and combination. Also, the system was shown accurately distribution of conversion at the depth of skin correction. Therefore, conversion modeling was established effectively to separate the division parts for conversion system. We will be possible to progress the improvement effectiveness of the skin and to consist of the continuous penetration control system for functional energy on the skin.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2109-2118
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• 2016

Based on the space vector pulse width modulation (SVPWM) theory, this paper realizes an easier SVPWM strategy, which is equivalently implemented by CBSPWM with zero-sequence voltage injection. The traditional SVPWM strategy has no effect on controlling the neutral-point voltage balance. In order to solve the neutral-point voltage unbalance problem for neutral-point-clamped (NPC) three-level inverters, this paper proposes a neutral-point voltage balance controller. The proposed controller realizes controlling the neutral-point voltage balance by dynamically calculating the offset superimposed to the three-phase modulation waves of an equivalent SVPWM strategy. Compared with the traditional SVPWM strategy, the proposed neutral-point voltage balance controller has a strong ability to balance the neutral-point voltage, has good steady-state performance, improves the output waveforms quality and is easy for digital implementation. An experiment has been carried out on a NPC three-level inverter prototype based on a digital signal processor-complex programmable logic device (DSP-CPLD). The obtained experimental results verify the effectiveness of the proposed neutral-point voltage balance controller.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.1
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• pp.53-58
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• 2016

Various jumping robot platforms have been developed to carry out missions such as rescues, explorations, or inspections of dangerous environments. We suggested a jumping robot platform using energy conversion of the elastic body like the bar of a pole vault, which is the main part in which elastic force occurs. The compliant link was optimized by an optimization method based on Taguchi methodology, and the robot's leaping ability was improved. Among the parameters, the length, width, and thickness of the link were selected as design variables first while the others were fixed. The level of the design variables was settled, and an orthogonal array about its combination was made. In the experiment, dynamic simulations were conducted using the DAFUL program, and response table and sensitivity analyses were performed. We found optimized values through a level average analysis and sensitivity analysis. As a result, the maximum leaping height of the optimized robot increased by more than 6.2% compared to the initial one, and these data will be used to design a new robot.

• Journal of Power Electronics
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• v.18 no.1
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• pp.34-44
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• 2018

This paper presents a pulse-width adjustment (PWA) strategy for a novel bidirectional DC-DC boost converter to improve the performance of the dynamic inductor current response. This novel converter consists of three main components: a full-bridge converter (FBC), a high-frequency isolated transformer with large leakage inductance, and a three-level voltage-doubler rectifier (VDR). A number of scholars have analyzed the principles, such as the soft-switching performance and high-efficiency characteristic, of this converter based on pulse-width modulation plus phase-shift (PPS) control. It turns out that this converter is suitable for energy storage applications and exhibits good performance. However, the dynamic inductor current response processes of control variable adjustment is not analyzed in this converter. In fact, dc component may occur in the inductor current during its dynamic response process, which can influence the stability and reliability of the converter system. The dynamic responses under different operating modes of a conventional feedforward control are discussed in this paper. And a PWA strategy is proposed to enhance the dynamic inductor current response performance of the converter. This paper gives a detailed design and implementation of the PWA strategy. The proposed strategy is verified through a series of simulation and experimental results.

• Solar Energy
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• v.12 no.3
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• pp.21-27
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• 1992

This study is presents model testing to evalute daylighting performance in Atrium Building. There are several methods fof the prediction of Daylighting level in a Atrium Building, But they are not sufficient to estimate intreior daylight level of each different hights onleaner Atrium Building. In this study provide with making the model to estimate the environmental effect for the daylight on leaner Atrium, measuring the model in 80 variable sky condition, building direction, interior length-width ratio through the variation of floor-hight and space ratio.

• Advanced Composite Materials
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• v.16 no.2
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• pp.151-166
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• 2007

High-cycle fatigue characteristics of quasi-isotropic carbon fiber reinforced plastic (CFRP) laminates [-45/0/45/90]s up to $10^8$ cycles were investigated. To assess the fatigue behavior in the high-cycle region, fatigue tests were conducted at a frequency of 100 Hz, since it is difficult to investigate the fatigue characteristics in high-cycle at 5 Hz. Then, the damage behavior of the specimen was observed with a microscope, soft X-ray photography and a 3D ultrasonic inspection system. In this study, to evaluate quantitative characteristics of both transverse crack propagation and delamination growth in the high-cycle region, the energy release rate associated with damage growth in the width direction was calculated. Transverse crack propagation and delamination growth in the width direction were evaluated based on a modified Paris law approach. The results revealed that transverse crack propagation delayed under the test conditions of less than ${\sigma}_{max}/{\sigma}_b$ = 0.3 of the applied stress level.