• The KIPS Transactions:PartA
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• v.13A no.7 s.104
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• pp.573-580
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• 2006

The conventional transport layer protocol TCP is designed to work under condition of packet loss is due to the network congestion, so that it's suitable in the traditional wired network with fixed hosts but it's inefficient on the wireless network where the environment of fading, noise, and transmission error comes from interference. This result from the needless transmission control of the bit error is due to treats the packet loss as a packet congestion control in the wireless network. In this paper, we propose the advanced SNOOP protocol with the consecutive packet loss and TCP window control to avoid the needless congestion management algorithm in wireless network for the wireless TCP packet transmission enhancement. We verify the performance of the advanced module from the simulation experiment result.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.5
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• pp.597-604
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• 2010

This study focuses on the design of a mechanical joint for a zero moment crane (ZMC), which is a specialized loading/unloading system used in a mobile harbor (MH). The mechanical joint is based on the concept of zero moment point (ZMP), and it plays an important role in stabilizing a ZMC. For effective stabilization, it is necessary to ensure that the mechanical joint is robust to a wide variety of loads; further, the joint must allow the structures connected to it to perform rotational motion with two degrees of freedom By adopting a traditional design process, we designed a new mechanical joint; in this design, a universal joint is coupled with a spherical joint, and then, deformable rolling elements are incorporated. The rolling elements facilitate load distribution and help in decreasing power loss during loading/unloading. Because of the complexity of the proposed system, Kriging-based approximate optimization method is used for enhancing the optimization efficiency. In order to validate the design of the proposed mechanical joint, a structural analysis is performed, and a small-scale prototype is built.

• Proceedings of the Korea Contents Association Conference
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• 2007.11a
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• pp.126-129
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• 2007

Recently the use of wireless network increases according to it solves the hand-off and with path loss, pading, noise etc of wireless network the research for transmission error improvement is developed. TCP and SCTP of standard where it guarantees the reliability of wire network apply in wireless network the congestion control, flow control mechanism used it decreases the efficiency of data transfer throughputs. In this paper, It mixes SCTP and SNOOP for SCTP apply on wireless network, to improve BS(Basic Station) operation processes when the transmission error occurs in wireless network. BS send ZWP(Zero Window Probe) to MN(Mobile Node) when the transmission error occurs so, check path and status and update RWND and error status checked. It selects the new path, send ZWA(Zero Window Advertisement) to FH(Fixed Host) and the prevents call to congestion control or flow control and it does to make wait status standing. Continuously of data transfer after the connection of wireless network is stabilized, it make increase about 10% the transmission throughput of data.

• Journal of the Korea Computer Industry Society
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• v.2 no.3
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• pp.357-362
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• 2001

For general laser power supply to control the laser power density, the secondary of the power transformer is connected to the rectifier and filter capacitor. The output of a rectifier is applied to a switching element in the secondary of the transformer. So power supply is complicated and the loss of switching is considerably. In addition, according to increasing pulse repetition rate, charged energy of energy-storage capacitor bank is not transferred sufficiently to flashlamp, and laser output efficiency decreases. In this study, we have proposed the power supply in which the SCR was turned on at the zero point of input AC voltage by the method of zero cross control(ZCC). As a result of that, The new power supply employed ZCC are simple and compact in design. And laser output efficiency increased by the 3.5$\%$ other than conventional power supply (SCADC), when a repetition rate was increased by the 10pps. In 60pps, efficiency was increased by about 20$\%$.

• Journal of Electrical Engineering and Technology
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• v.13 no.3
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• pp.1251-1264
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• 2018

The systematic and effective design method of a Class-D current-source resonant inverter for use in an induction cooker with zero-ripple line current is presented. The design procedure is based on the principle of the Class-D current-source resonant inverter with a simplified load network model that is a parallel equivalent circuit. An induction load characterization is obtained from a large-signal excitation test-bench based on parallel load network, which is the key to an accurate design for the induction cooker system. Accordingly, the proposed scheme provides a systematic, precise, and feasible solution than the existing design method based on series-parallel load network under low-signal excitation. Moreover, a zero-ripple condition of utility-line input current is naturally preserved without any extra circuit or control. Meanwhile, a differential-mode input electromagnetic interference (EMI) filter can be eliminated, high power quality in utility-line can be obtained, and a standard-recovery diode of bridge-rectifier can be employed. The step-by-step design procedure explained with design example. The devices stress and power loss analysis of induction cooker with a parallel load network under large-signal excitation are described. A 2,500-W laboratory prototype was developed for $220-V_{rms}/50-Hz$ utility-line to verify the theoretical analysis. An efficiency of the prototype is 96% at full load.

• Resources Recycling
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• v.12 no.6
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• pp.26-31
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• 2003

The power loss characteristics of Mn-Zn ferrite were observed with the sintering temperature. In case of $1150 ^{\circ}C$ sintering, the core loss increased with measuring temperature, and does not have minimum value at the point where the magnetocrystalline anisotropy be 'zero'. This reason mainly due to the change of core loss mechanism with grain size which affects residual loss. The grain size and sintered density slightly increased with equilibrium oxygen partial pressure at$ 1150 ^{\circ}C$ sintering. The resistivity and initial permeability showed no significance with atmosphere, these results due to complex effect of $Fe^{2+}$ concentration and microstructure change. The core loss at $100^{\circ}C$ decreased as the equilibrium oxygen partial pressure increased.e increased.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.559-561
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• 1994

In this paper a new AC/DC/AC converter in which Soft-Switched-Inductor Module is used, is proposed. This new converter adopts ZVS(Zero-Voltage-Switching) for main switches. Therefore the switching loss is minimized and high frequency operation is possible. Operations principles, short analyses and computer simulation results are presented.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.114-117
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• 1999

This paper has described about principle and form of proposed circuit made use of soft switching technology ZVS(Zero-Voltage-Switching) to reduce turn on and off loss at switching. Also, the analysis of the proposed circuit was described by using normalized parameter and operating characteristics has been evaluated as to switching frequency and parameters. Based on the characteristics value, a method of the circuit design is proposed. The theoretical results are in good agreement with the experimental ones. The proposed circuit is considerated to be useful for induction heating and discharge lamp.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.259-262
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• 1999

This paper presents the design of highly efficient one-chip CMOS DC/DC converter. The converter operates at the switching frequency of 1MHz for reducing the size of passive elements. And use the zero voltage switching(ZVS) for minimizing switching loss at high frequency. The simulation shows that the circuit can achieve a 95% efficiency while delivering a load of 1W at 2V output.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1999.11a
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• pp.189-194
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• 1999

This paper proposes a current-fed type high frequency inverter using a soft switching technology Zero-Voltage-Switching to reduce turn on and off loss at the switching. The analysis of the proposed circuit was described by using normalized parameter and operating characteristics have been evaluated as to switching frequency and parameters. The theoretical results are in good agreement with the experimental ones. In the future the proposed circuit is considered to be useful for induction heating applications.