• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.8
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• pp.5541-5549
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• 2015

This paper introduces a safer and more power efficient heater by using induction heating, to apply to the semiconductor wafer fabrication exhaust gas cleaning system. The exhaust gas cleaning system is currently made with filament heater that generates an endothermic reaction of N2 gas for the removal of moisture. Induction theory, through the bases of theoretical optimization and electronic implementation, is applied in the design of the induction heater specifically for the semiconductor wafer exhaust system. The new induction heating design provides a solution to the issues with the current energy inefficient, unreliable, and unsafe design. A robust and calibrated design of the induction heater is used to optimize the energy consumption. Optimization is based on the calibrated ZVS induction circuit design specified by the resonant frequency of the exhaust pipe. The fail-safe energy limiter embedded in the system uses a voltage regulator through the feedback of the MOSFET control, which allows the system performance to operate within the specification of the N2 Heater unit. A specification and performance comparison from current conventional filament heater is made with the calibrated induction heater design for numerical analysis and the proof of a better design.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.11
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• pp.2199-2214
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• 1994

In order to sufficiently utilize the potential effectiveness of ATM networks, systematic and effective network management and control systems must be employed. In addition to network design, planning, and call routing techniques used in traditional circuit-switched networks. ATM networks can provide logical VP(Virtual Path) reconfiguration capabilities which can adapt to changes in the network environment. With a proper application of the VP reconfiguration technique, ATM networks can reduce the overhead of frequent network redesign and the overhead of call routing processing. However, ATM VP reconfiguration is a very complex and difficult problem which consists of many facets of optimization subproblems such as VP routing. VP sizing, VP terminating point location and VC routing. Most previous research on the ATM logical network reconfiguration problem dealt with the subset of the problem. This paper mathematically formulates the ATM network reconfiguration problem completely considering all subproblems. Since it is very difficult to derive the optimal solution of the formulated problem, we develop a heuristic method based on a Max min bandwidth allocation principle. We show the feasibility of the proposed heuristic method with a simple example.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.11
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• pp.2465-2473
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• 2011

This paper describes a circuit-level optimization of DFU(decoding function unit) for LDPC decoder which is used in wireless communication systems including WiMAX and WLAN. A new design of DFU based on sign-magnitude arithmetic instead of two's complement arithmetic is proposed, resulting in 18% reduction of gate count for 96 DFUs array used in mobile WiMAX LDPC decoder. A multi-mode LDPC decoder for mobile WiMAX standard is designed using the proposed DFU. The LDPC decoder synthesized using a 0.18-${\mu}m$ CMOS cell library with 50 MHz clock has 268,870 gates and 71,424 bits RAM, and it is verified by FPGA implementation.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.12
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• pp.1376-1381
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• 2012

Optical devices are used extensively in the field of information network. Increasing demand for optical device, optical interconnection has been a important issue for commercialization. However many problems exist in the interconnection between optical device and optical fiber, and in the case of the multi-channel, problems of the optical alignment and optical array arise. For solving the alignment and array problem of optical device and the optical fiber, we fabricated fiber alignment and array by using imprint technology. Achieved higher precision of optical fiber alignment and array due to fabricating using imprint technology. The silicon stamp with different depth was fabricated using the conventional photolithography. Using the silicon stamp, a nickel stamp was fabricated by electroforming process. We conducted imprint process using the nickel stamp with different depth. The optical alignment and array by fabricating the patterns of optical device and fiber alignment and array using imprint process, and achieved higher precision of decreasing the dimensional error of the patterns by optimization of process. The fabricated optical interconnection of PLC device was measured 3.9 dB and 4.2 dB, lower than criteria specified by international standard.

• Journal of Convergence Society for SMB
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• v.6 no.4
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• pp.25-30
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• 2016

This paper presents on the development of a compact anti-lost device requested recently. The proposed device consists of the master and slave modules based on Bluetooth4.1 technology. To implement a low-power characteristic, an algorithm has been also developed. The transmitting and receiving circuits are designed by using BoT CLE110 module supporting Bluetooth 4.1. The ATmega 328P-AU was used for the control and LP3874EMP was used as a linear regulator. Power consumption of the fabricated product in operating mode is only 10mAh and 35mAh for MCU operating state. Alarm operation distance is $10m{\pm}30%$, the effective radiated power is less than 10mW, the frequency band is designed to operate in the Bluetooth band with 26MHz bandwidth. And algorithms have been developed to extend the battery life. The size of the product was obtained as $45{\times}45{\times}15mm$ for master and $35{\times}35{\times}10mm$ fr slave. After the optimization process, it is expected to be commercialized as a wristwatch for anti-lost device.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.347.1-347.1
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• 2016

Screen printing is commonly used to form the electrode for crystalline silicon solar cells. However, it has caused high resistance and low aspect ratio, resulting in decrease of conversion efficiency. Accordingly, Ni/Cu/Ag plating method could be applied for crystalline silicon solar cells to reduce contact resistance. For Ni/Cu/Ag plating, laser ablation process is required to remove anti-reflection layers prior to the plating process, but laser ablation results in surface damage and then decrease of open-circuit voltage and cell efficiency. Another issue with plating process is ghost plating. Ghost plating occurred in the non-metallized region, resulting from pin-hole in anti-reflection layer. In this paper, we investigated the effect of Ni/Cu/Ag plating on the electrical properties, compared to screen printing method. In addition, phosphoric acid layer was spin-coated prior to laser ablation to minimize emitter damage by the laser. Phosphorous elements in phosphoric acid generated selective emitter throughout emitter layer during laser process. Then, KOH treatment was applied to remove surface damage by laser. At this step, amorphous silicon formed by laser ablation was recrystallized during firing process and remaining of amorphous silicon was removed by KOH treatment. As a result, electrical properties as Jsc, FF and efficiency were improved, but Voc was lower than screen printed solar cells because Voc was decreased due to surface damage by laser process. Accordingly, we expect that efficiency of solar cells could be improved by optimization of the process to remove surface damage.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.1
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• pp.23-30
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• 2017

Currently, road lightings are installed with less than 400W of existing metal halide lamps. These road lightings are being replaced by energy-saving lightings. Induction lamps are expected to be more actively replaced with targets for tunnel lighting and high ceiling lighting. Therefore, it is necessary to develop high efficiency, high power induction lamps system. In this study, the gas type & pressure, amalgam type were designed for the high power of the induction lamps. And induction lamp system was optimized through electrical, optical characteristics analysis. It is optimized to the gas pressure 300~350 [mmHg] for the discharge tube of high power induction lamp and ferrite core. The driving circuit matching was completed with a induction lamp using indium amalgam. The rated power consumption of the induction lamp was optimized with 250 W (rated ${\pm}10%$)

• Journal of Power Electronics
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• v.15 no.5
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• pp.1305-1317
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• 2015

Distributed generation systems (DGSs) have been getting more and more attention in terms of renewable energy use and new generation technologies in the past decades. The self-excited induction generator (SEIG) occupies an important role in the area of energy conversion due to its low cost, robustness and simple control. Unlike synchronous generators, the SEIG has to absorb capacitive reactive power from the outer device aiming to stabilize the terminal voltage at load changes. This paper presents a novel static VAR compensator (SVC) called a magnetic energy recovery switch (MERS) to serve as a voltage controller in SEIG powered DGSs. In addition, many small scale SEIGs, instead of a single large one, are applied and devoted to promote the generation efficiency. To begin with, an expandable mathematic model based on a d-q equivalent circuit is created for parallel SEIGs. The control method of the MERS is further improved with the objective of broadening its operating range and restraining current harmonics by parameter optimization. A hybrid control strategy is developed by taking both of the stand-alone and grid-connected modes into consideration. Then simulation and experiments are carried out in the case of single and double SEIG(s) generation. Finally, the measurement results verify that the proposed DGS with SVC-MERS achieves a better stability and higher feasibility. The major advantages of the mentioned variable reactive power supplier, when compared to the STATCOM, include the adoption of a small DC capacitor, line frequency switching, simple control and less loss.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.7 s.98
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• pp.732-739
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• 2005

In this paper, the design and implementation of the Ka-band(20/30 GHz) waveguide diplexer with an E-plane T-junction are described. The waveguide diplexer consists of a transmit filter and a receive filter combined to the antenna port via an E-plane T-junction. The reason why the E-plane T-junction structure was selected is to reduce PIM(Passive Intermodulation) level as the split-plane is located in the low electrical current zone. The optimization was performed using the equivalent circuit so that the computation time might reduce. The structure of the diplexer was designed to handle high power and the multipaction analysis was performed. The multipaction margin was greater than 12 dB and satisfied with ESA/ESTEC recommendation. The manufactured diplexer shows minimum return loss of 22 dB, maximum insertion loss of 0.20 dB and maximum isolation of -40 dB for both transmitted receive bands. Those mean the analysis results of the waveguide diplexer were well agreed with the electrical performance test.

• Journal of the Korea Convergence Society
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• v.9 no.8
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• pp.33-39
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• 2018

In the Internet of Things (IoT) era, objects are connected to each other by wired and wireless networks, and information is exchanged whenever necessary. Channel and network environments change over time; thus, a carrier sensing function that identifies whether signals containing information are present in the channel is essential. The carrier sensing circuit of a wireless communication system determines the receiver sensitivity, and the receiver sensitivity is closely related to the service coverage and service quality of the system. As the receiver sensitivity decreases, the service coverage increases but it becomes sensitive to noise. However, as the receiver sensitivity increases, the service coverage decreases but it becomes insensitive to the noise. Therefore, carrier sensing design and optimization are very important from the viewpoint of the receiver sensitivity and noise sensitivity. This paper proposes an effective carrier sensing technique from the viewpoint of the receiver sensitivity for the long range IoT.