• Journal of Korea Multimedia Society
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• v.10 no.9
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• pp.1153-1164
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• 2007

One of the most challenging technical issues in mobile communication for multimedia is Quality of Service (QoS) management of handover calls. This paper proposes a 2-level handover control system to copy with this problem. A 2-level handover control system consists of resource reservation and call admission control modules. The resource reservation module divides the network resource into Hard and Soft reserved resource. The Hard reserved resource is only for the handover calls while the Soft reserved resource is for both the handovers and the new calls. And also, the resource reservation module classifies handovers into primary and secondary handovers based on often they occur. The call admission control module deals with the primary and secondary handover calls in different ways. The new calls can use Soft reserved resource only if there is sufficient amount available in the Hard reserved resource. Proposed system is evaluated using an M/M/c/c queueing model. It is shown that proposed system allows more efficient utilization of network resource without degrading QoS comparing with the legacy handover control systems.

• Journal of the Korean Solar Energy Society
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• v.30 no.6
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• pp.73-80
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• 2010

This study was conducted to estimate the relative performance of modules with changed characteristics due to long term exposure to the outdoor environment, with a specially made test device for simultaneous measurement of real time power output from the photovoltaic array, taking into account the inclined panel, direct irradiation, power being generated, temperature as well as the optimal analysis timing. In terminology description, M is an abbreviation of module and Group A, Group B are 10 modules series connection (1~10 of M), (11~20 of M) for each of them respectively. The overall mean voltage difference of M-18 with the lowest power output and M-14 with the highest output is-2.13V and it was identifiable that voltage difference was more concentrated to Group B. In addition, in case of M-2 and M-7, M-8, when compared with M-14, the overall mean voltage difference was -0.92V, -1.56 and -0.91V respectively showing the more concentration to Group A. When the temperature of module went up by $1^{\circ}C$, the mean voltage was reduced by 0.35V. For current, Group A was lower than Group B by-0.022A and the ratio of each group was 49.68% and 50.32% respectively, presumably the module with deteriorated properties were more concentrated to Group A relatively. From the comparison of relations with the comprehensive accumulation, M-2, M-7, M-8, M-16 and M-18 were those with deterioration of performance to the worst, thereby requiring precision examination. In comparative efficiency, M-14 was the most excellent one as 12.19% while M-18 as 10.53% was identified that its efficiency was comparatively rapidly reduced.

• Journal of Electrical Engineering and Technology
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• v.13 no.4
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• pp.1638-1643
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• 2018

Multi-layer ceramic capacitors as decoupling capacitor were fabricated by dielectric composition with a high dielectric constant. The fabricated decoupling capacitors were embedded in the PCB of the 10G RF transceiver module and evaluated for the characteristics of electrical noise by the level of AC input voltage. In order to further improve the electrical properties of the $BaTiO_3$ based composite, glass frit, MgO, $Y_2O_3$, $Mn_3O$, $V_2O_5$, $BaCO_3$, $SiO_2$, and $Al_2O_3$ were used as additives. The electrical properties of the composites were determined by various amounts of additives and optimum sintering temperature. As a result of the optimized composite, it was possible to obtain a density of $5.77g/cm^3$, a dielectric constant of 1994, and an insulation resistance of $2.91{\times}10^{12}{\Omega}$ at an additive content of 5wt% and a sintering temperature of $1250^{\circ}C$. After forming a $2.5{\mu}m$ green sheet using the doctor blade method, a total of 77 layers were laminated and sintered at $1180^{\circ}C$. A decoupling capacitor with a size of $0.6mm(W){\times}0.3mm(L){\times}0.3mm(T)$ (width, length and thickness, respectively) and a capacitance of 100 nF was embedded using a PCB process for the 10G RF Transceiver modules. In the range of AC input voltage 400mmV @ 500kHz to 2200mV @ 900kHz, the embedded 10G RF Transceiver modules evaluated that it has better electrical performance than the non-embedded modules.

• Communications of the Korean Mathematical Society
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• v.31 no.4
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• pp.695-701
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• 2016

Let I and J be two ideals of a commutative Noetherian ring R and M, N be two non-zero finitely generated R-modules. Let t be a non-negative integer such that $H^i_{I,J}(N)$ is (I, J)-minimax for all i < t. It is shown that the generalized local cohomology module $H^i_{I,J}(M,N)$ is (I, J)-Cofinite minimax for all i < t. Also, we prove that the R-module $Ext^j_R(R/I,H^i_{I,J}(N))$ is finitely generated for all $i{\leq}t$ and j = 0, 1.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1904-1906
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• 1999

The purpose of this study is to manufacture and test a thermoelectric generator which converts unused energy from close-at-hand sources, such as garbage incineration heat and industrial exhaust, to electricity. A manufacturing process and the properties of a thermoelectric generator are discussed before simulating the thermal stress and thermal properties of a thermoelectric module located between an aluminum tube and alumina plate. It was shown that the electric voltage of a thermoelectric generator with 128 thermoelectric modules was 4.8 voltage per Kelvin, and the longitudinal stresses of an aluminum tube with a two-point constrained tube could be released more than those with a one-point constrained tube.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.257-262
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• 2001

This paper describes a specialized CAD system for injection mold design, which has been developed using the application procedure interfaces of Unigraphics. The system consists of modeling modules that are mutually independent and can be accessed without any predefined sequence. In addition, the design process modeling capability proposed in this paper facilitate mold redesign process caused by modification of part shape.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.322-325
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• 2002

In this study, noise figures of 0.3 $\mu\textrm{m}$-GaAs MESFETs are predicted experimentally with different temperatures. Both the noise figure and the gate leakage current are obtained with wide range of temperatures(27$^{\circ}C$∼300$^{\circ}C$). From the results, gate leakage current increases with temperatures. It is expected that gate leakage current contributes directly to the increase of shot noise current. It is therefore highly recommended to apply an accurate noise analysis to the design of the devices and modules at high temperatures. Fini,Uy the relation between the gate currents resulting in the increase of noise and the noise figures of submicron GaAs MESFETs are traced with different temperatures

• Journal of the Korean Society for Precision Engineering
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• v.19 no.1
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• pp.79-92
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• 2002

This paper describes a research work of developing computer-aided design of a product with bending and piercing for progressive working. An approach to the system for progressive working is based on the knowledge-based rules. Knowledge for the system is formulated from plasticity theories, experimental results and the empirical knowledge of field experts. The system has been written in AutoLISP on the AutoCAD with a personal computer and is composed of four main modules, which are input and shape treatment, flat pattern layout, strip layout and die layout modules. The system is designed by considering several factors, such as bending sequences by fuzzy set theory, complexities of blank geometry, punch profiles, and the availability of a press equipment. Strip layout drawing generated in the strip layout module is presented in 3-D graphic farms, including bending sequences and piercing processes with punch profiles divided into for external area. The die layout module carries out die design for each process obtained from the results of the strip layout. Results obtained using the modules enable the manufacturer for progressive working of electric products to be more efficient in this field.

• Journal of the Korea Society of Computer and Information
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• v.20 no.4
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• pp.111-117
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• 2015

The exam scheduling problem has been classified as nondeterministic polynomial time-complete (NP-complete) problem because of the polynomial time algorithm to obtain the exact solution has been unknown yet. Gu${\acute{e}}$ret et al. tries to obtain the solution using linear programming with $O(m^4)$ time complexity for this problem. On the other hand, this paper suggests chromatic number algorithm with O(m) time complexity. The proposed algorithm converts the original data to incompatibility matrix for modules and graph firstly. Then, this algorithm packs the minimum degree vertex (module) and not adjacent vertex to this vertex into the bin $B_i$ with color $C_i$ in order to exam within minimum time period and meet the incompatibility constraints. As a result of experiments, this algorithm reduces the $O(m^4)$ of linear programming to O(m) time complexity for exam scheduling problem, and gets the same solution with linear programming.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.2
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• pp.357-362
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• 2017

Among the lithium metal oxides for asymmetric hybrid supercapacitor, $Li_4Ti_5O_{12}(LTO)$ is an emerging electrode material as zero-stain material in volume change during the with the charging and discharging processes. The pulverized LTO powder was observed to show the enhanced capacity from 120 mAh/g to 156 mAh/g at C-rate (10, 100 C). Hybrid supercapacitor module(48V, 416F) was fabricated using an asymmetric hybrid capacitor with a capacitance of 7500F. As a result of the measurement of C-rate characteristics, the module shows that the discharge time is drastically reduced at more than 50C, and the ESR and voltage drop characteristics are increased. The energy density and power density were reduced under high C-rate conditions. When designing asymmetric hybrid supercapacitor module, the C-rate and ESR should be considered As a result of measuring the 5 kw UPS, it was discharged at the current of 116A~170A during the discharge in the voltage range of 48V~30V, and the compensation time at discharge was measured to be about 33.2s. Experimental results show that it can be applied to applications related to stabilization of power quality by applying hybrid supercapacitor module.