• Journal of Power Electronics
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• v.18 no.6
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• pp.1912-1919
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• 2018

The output capacitance of power semiconductor devices is important in determining the switching losses and in the operation of some resonant converter topologies. Thus, it is important to be able to accurately determine the output capacitance of a particular device operating at elevated power levels so that the contribution of the output capacitance discharge to switch-on losses can be determined under these conditions. Power semiconductor switch manufacturers usually measure device output capacitance using small-signal methods that may be insufficient for power switching applications. This paper shows how first principle methods are applied in a novel way to obtain more relevant large signal output capacitances of Gallium-Nitride (GaN) FETs using the drain-source voltage transient during device switch-off numerically. A non-linear capacitance for an increase in voltage is determined with good correlation. Simulations are verified using experimental results from two different devices. It is shown that the large signal output capacitance as a function of the drain-source voltage is higher than the small signal values published in the data sheets for each of the devices. It can also be seen that the loss contribution of the output capacitance discharging in the channel during switch-on correlates well with other methods proposed in the literature, which confirms that the proposed method has merit.

• Journal of the Semiconductor & Display Technology
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• v.19 no.4
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• pp.22-27
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• 2020

In this paper, a generalized efficiency equation was proposed to estimate the internal loss of the SMPS (switched-mode power supply) with 3 variables. The first variable was an internal loss not related to the load current such as auxiliary power, the second was a loss proportional to the current such as diode loss, and the third was a loss proportional to square of the current such as conduction loss. Especially, theoretical internal losses of the totem pole bridgeless PFC which is widely used for high efficiency SMPS were expressed as output function to compare generalized efficiency equation. In addition, in order to reduce the conduction loss of the switch, when a multiple switch were paralleled, the correlation with the efficiency was analyzed and shown as a graph. In order to confirm the degree of the parallel switch structure on the efficiency improvement, a 2kW class totem pole bridgeless PFC was constructed and the effectiveness of the analysis was confirmed by comparing the generalized efficiency equation and theoretical loss analysis results with experimental data.

• IEIE Transactions on Smart Processing and Computing
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• v.6 no.1
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• pp.60-65
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• 2017

Network virtualization enables us to make efficient use of resources in a physical network by embedding multiple virtual networks in the physical network. In this paper, we develop a prototype of a virtual network embedding system. Our system consists of OpenStack, which is an open source cloud service platform, and shell scripts. Because OpenStack does not provide a quality of service control function, we realize bandwidth reservation for virtual links by making use of the ingress policing function of Open vSwitch, which is a virtual switch used in OpenStack. The shell scripts in our system automatically construct the required virtual network on the physical network using the OpenStack command-line interface, and they reserve bandwidth for virtual links using the Open vSwitch command. Experimental evaluation confirms that our system constructs the requested virtual network and appropriately allocates node and link resources to it.

• Journal of Service Research and Studies
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• v.5 no.1
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• pp.57-70
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• 2015

This paper develop curnel based high speed packet filtering imbedded gateway and firewall using cloud database. This study develop equipment include of predict function through bigdata analysis using cloud system. This equipment include intrusion prevention for network attack, and include system security function of L7 switch based contents. This study can improve security level of little company and general family. This study can pioneer a new market. This study can develop high perfomance switch and replacement of existing security equipment. This study proposed new next generation algorithm for constuction of high performance system from low specifications.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.80-82
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• 2007

In this paper, we proposed new maximum electric power tracking algorithm by composing Buck-boost chopper circuit to charge electric power from wind energy generator which is under low and high wind velocity. The break function is also proposed with the existed buck-boost chopper switch. We made a proto-type as a lab level to verify appropriateness of using proposed circuit.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.1
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• pp.466-474
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• 2014

This paper presents the line contention avoidance experiments with an optical switch, which was selected based on the comparison analysis and evaluation of the various characteristics. For example, the function, structure, strengths and weaknesses of the optical switches. After considering the nonblocking, modularity, upgrade ability and optical power loss of the several kind of the switch fabrics, a switch was selected. The selected switch fabric by using wavelength converters was controlled to avoid contention of the optical lines. In this experiment shows an example of three cases. As a result of this experiment, optical signal shows a changed peek of optical power in output. By showing a peak it confirms that the contention was avoided. By analyzing of changed optical power according to the channel setting time and release time to control of the switch could be determined. If this analysis applied to the network design, economical and efficient structures can be formed.

• Journal of Electrical Engineering and information Science
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• v.3 no.1
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• pp.28-35
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• 1998

In this paper, an NxN input-buffered crosspoint packet switch which selects a Head of the Line, HOL, packet in contention randomly is analyzed with a new approach. The approach is based on both a Markov chain representation of the input buffer and the probability that a HOL packet is successfully served. The probability as a function of N is derived, and it makes it possible to express the average packet delay and the average number of packets in the buffer as a function of N. The contention resolution policy based on the occupancy of the input buffer is also presented and analyzed with this same approach and the relationship between two selection policies is analyzed in terms of the occupancy of the input buffer.

• Journal of Korean Ophthalmic Optics Society
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• v.6 no.1
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• pp.81-85
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• 2001

The color vision was composed of the wavelength absorption of three R. G. B cone photo-receptors and the r-g, y-b channel of an opponent process. The color vision defects mechanism for the electric circuit made up a photo cell, relay switch and transformer. This mechanism very well applied to the color vision defects mechanism owing to be y-b chromatic valence function in case of a cone R or G defects and to be r-g chromatic valence function in case of a cone B defects.

• Nuclear Engineering and Technology
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• v.35 no.2
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• pp.133-143
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• 2003

Stem-stem nut coefficient of friction(COF) in motor-operated gate/globe valves is one of the important factors which determine the performance of the valve/actuators. The COF is affected greatly by the type and condition of the stem-stem nut lubricants, environmental parameters, surface condition of the stem/stem-nuts, and the number of strokes after the lubrication. In this paper, the measured data of the COFs at stem threads of some safety-related motor-operated gate/globe valves in domestic nuclear power plants are presented. In addition, the performance of the lubricants is evaluated by comparing the COFs among those valves. The results show that the measured COF at torque switch trip are higher than the unwedging COF and conservatively applicable to the unwedging COF. It is also shown that the lubricating performance based on the measured COFs varies with the lubricants.

• The KIPS Transactions:PartC
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• v.9C no.1
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• pp.65-72
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• 2002

In this paper, we implement a high-speed swatch tilth the function for label integration to enhance the expansion of networks using the label space of routers efficiently on MPLS over ATM networks. We propose an appropriate hardware structure to support the VC-merge function and differentiated services simultaneously. In this paper, we use the adaptive congestion control method such as EPD algorithm in carte that there is a possibility of network congestion in output buffers of each core LSR. In addition, we justify the validity of the proposed VC-merge method through simulation and comparison to conventional Non VC-merge methods. The proposed VC-merge capable switch is modeled in VHDL. synthesized, and fabricated using the SAMSUNG 0.5um SOG process.