• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.4A
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• pp.471-480
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• 2000

With the limited wireless resources, various traffic in the cellular system is served based on micro-cell or pico-cell structure. The rapid increase in the number of mobile users results in the frequent handoff which is becoming a critical issue. In this paper, we propose a channel allocation scheme to reduce the probability of handoff failure. In this scheme, we provide a guard channel for each service to handle the handoff processes. It maintains the low probability of failure in handoff calls. To prevent the performance degradation due to the traffic variation, we use a channel arbitration method that adaptively manages the number of channels based on the call density. We evaluated the performance in terms of the initial call blocking probability and the handoff call blocking probability for various traffic and motility. We found that the proposed scheme keeps the lower probability of call blocking through the efficient channel arbitration than other suggested methods even for the irregular traffic conditions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.7A
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• pp.770-777
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• 2007

Smaller cell size in the micro-cell or pico-cell structure brings about more frequent hand-overs between cells, and higher speed movement of the mobile terminal makes short the permissible time interval for executing these hand-over procedures. In this situation the hand-over failure may occur or some packets may be lost during the hand-over. Moreover a rapid degradation of throughput is triggered by packet re-transmission for compensating such errors. The QoS (Quality of Services) of mobile multimedia applications with higher bits rate requirements and higher speed mobility are severely affected by even shot service interruption. This paper proposes a new hand-over scheme to provide seamless services in the next generation mobile communication systems. Simulation is done to evaluate the performance of the proposed scheme based on its hand-over failure rate and packet loss rate.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.6
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• pp.583-590
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• 2010

In this paper, a novel CRLH-TL unit cell with controllable transmission zeros was proposed. Proposed composite right/left handed transmission line(CRLH-TL) unit cell is implemented in the form of the metal-insulator-metal(MIM) capacitors, the microstrip stub inductors, and the co-planar waveguide(CPW) inductor. And this proposed CRLH-TL generates two transmission zeros in lower/upper passband by the effort of electromagnetic couplings between each MIM capacitors and microstrip stub inductors. Using this proposed CRLH-TL, broad bandpass filter for UWB system was designed and fabricated. The measured results reveal that the two transmission zeros are observed in lower/upper passband and the overall size of the filter, excluding the feed line is about 8 mm$\times$8 mm, less then $\lambda_g$/4 on electric size.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.4
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• pp.57-61
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• 2016

Thick film sealing glass paste is required for cell packaging of NaS based battery for energy storage system, to join the beta-alumina electrolyte tube and the alpha-alumina battery cell cap components. This paper presents the effect of the particle sizes of seal glass powder and the sealing temperatures on the microstructure of the glass sealants was investigated. It was found that the larger in the particle size of seal glass powder, the smaller the pore volume and the number of pores in a unit area. Also, the number of pores decreased with increasing the sealing temperatures while the pore size was increased. This result enables the control of porosity, pore distribution and number of pores in a microstructure of glass sealing component by proper selection of glass powders particle size and sealing temperature.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.5
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• pp.331-338
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• 2020

In this study, the characteristic of a 3-D micro-woven material, which is one of the newly developed periodic open-cell structure, is analyzed through various computational simulations. To increase the accuracy of the numerical simulations, the distance between each directional wire is parameterized using six design variables, and its model geometry is precisely discretized using tetrahedron elements. Using the improved computational model, the material properties of the mechanical, thermal, and fluidic behavior are investigated using commercial software and compared with the previous experimental results. By changing the space between the x- and y-directional wires, a parametric test is performed to determine the tendency of the change in the material properties. In addition, the correlation between two different material properties is investigated using the Ashby chart. The result can further be used in determining the optimal pattern and wire spacing in 3-D micro-woven materials.

• Elastomers and Composites
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• v.44 no.4
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• pp.384-390
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• 2009

Roll-to-roll forming process is one of important metal processing technology because the process is simple and economical. These days, with these merits, roll-to-roll forming process is tried to be employed in manufacturing the circuit board, barrier ribs and solar cell plate. The solar cell plate may have millions of patterns, and the analysis of forming considering all the patterns is impossible due to the computational costs. In this study, analyses are carried out for various numbers of patterns and the results are compared. It is shown that the analyses results with four row patterns and twelve row patterns are same. So, it is considered that the analysis can be carried out for only four rows of pattern for the design of incremental roll-to-roll forming process. Also formability is analysed for various number of mesh, protrusion shapes and forming temperature.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.3
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• pp.13-23
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• 2022

Demand and interest in electric vehicles are increasing rapidly due to environmental issues. Improving the performance of electric vehicles requires the development of automotive batteries and battery joining technologies. Aluminum alloys are the most widely used metals in the electric vehicle industry, and aluminum bonding is used in all processes comprising automotive batteries. Therefore, in this paper, based on the characteristics of aluminum and aluminum alloys and knowledge of various aluminum joining technologies, the main and the next generation bonding technologies used in automotive battery are reviewed. It also explains the structure of automotive secondary battery cells and the integration order of 'cell-module-pack' where joining is used in the process, also various environmental conditions that must be considered when joining.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.4
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• pp.71-75
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• 2022

In this research, Fe-Ni alloy films were electrodeposited on stainless steel (SS304 and SS430) and Ti plates to investigate the effects of surface conditions of cathode on deposits. The Ti plates were electropolished in 3 M H₂SO₄-methanol electrolytes at various conditions before electrodeposition, and unpolished Ti and the optimized specimen, polished at 10 V for 8 min, were used as cathode. The anomalous codeposition, the phenomenon which more active Fe is reduced preferentially, occurred on all substrate, however, there were differences in composition of all deposits. As the results of potential monitoring during electrodeposition, it was confirmed that the larger overpotential was applied to the deposition cell when using Ti cathode, leading to high Fe content of deposits from unpolished Ti due to increase in nucleation of Fe. Also, it was founded that the polished Ti can reduced deposition overpotential.

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.749-753
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• 2012

In present work, anode support for micro-tubular SOFC was fabricated with outer diameter of 3 mm and characterized with microstructure, mechanical properties and gas permeability. The microstructure of surface and cross section of a porous anode support were analyzed by using SEM (Scanning Electron Microscope) image. The gas permeability and the mechanical strength of anode support was measured and analysed by using differential pressure at the flow rates of 50, 100, 150 cc/min. and using universal testing machine respectively. The unit cell composed of NiO-YSZ, YSZ, YSZ-LSM/LSM/LSCF was fabricated and operated with reaction temperature and fuel flow rate and showed maximum power density of $1095mW/cm^2$ on the condition of $800^{\circ}C$. The performance of single cell for micro-tubular SOFC increased with the increasing the reaction temperature due to the decrement of ohmic resistance of cell by the increment of the ionic conductivity of electrolyte through the evaluation of electrochemical impedance analysis for single cell with reaction temperature.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.12
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• pp.2569-2578
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• 2009

Core-A microprocessor is the all-Korean product designed as 32-bit embedded RISC microprocessor developed by KAIST and supported by the Industrial Property Office. This paper analyze Core-A microprocessor architecture and proposes efficient method to interface Core-A microprocessor with coprocessor. To verify proposed interfacing method, the AES cryptography processor that has 128-bit key and block size is used as a coprocessor. Coprocessor and AES are written in Verilog-HDL and verified using Modelsim simulator. It except AES module consists of about 3,743 gates and its maximum operating frequency is about 90Mhz under 0.35um CMOS technology. The proposed coprocessor interface architecture is efficiency to send data or to receive data from Core-A to coprocessor.