• Computational Structural Engineering
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• v.10 no.2
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• pp.213-223
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• 1997

Calculation of elastic wave fields has important applications in a variety of engineering fields including NDE (Non-destructive evaluation). Scattering problems have been investigated by numerous authors with different solution schemes. For simple geometries of the scatterers (e.g., cylinders or spheres), the analysis of steady-state elastic wave scattering has been carried out using analytical techniques. For arbitrary geometries and multiple inclusions, numerical methods have been developed. Special finite element methods, e.g., the infinite element method and a hybrid method called the Global-Local finite element method have also been developed for this purpose. Recently, the boundary integral equation method has been used successfully to solve scattering problems. In this paper, a volume integral equation method (VIEM) is proposed as a new numerical solution scheme for the solution of general elasto-dynamic problems in unbounded solids containing multiple inclusions and voids or cracks. A boundary integral equation method (BIEM) is also presented for elastic wave scattering problems. The relative advantage of the volume and boundary integral equation methods for solving scattering problems is discussed.

• Journal of Periodontal and Implant Science
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• v.35 no.2
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• pp.277-288
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• 2005

There is a potential role of collagenase-3 in alveolar bone loss and periodontal disease progression, we need to develope or find chemotherapeutic drugs or herbal agents which may regulate the expression of MMP-13. Ginseng saponin, one of the major components of Korea ginseng(panax ginseng) root, has many various biologic effects, such as cytotoxic effect, tumoricidal effects, cytokine regulations, and protein biosynthesis effect. The purpose of this study was to determine the effects of Korea red ginseng saponin on MMP-13 gene expression in osteoblasts. The experimental groups were cultured with ginseng saponin in concentration of 1.0, 10, 25, 50, 100, 250 and $500{\mu}g/ml$ for MTT assay. Primary rat calvarial cells were pre-treated for 1 hour with ginseng saponin(100 ${\mu}g/ml$) and then stimulated with $IL-1{\beta}(1.0ng/ml)$ and PTH(10 nM). MMP-13 gene expression was evaluated by RT-PCR. The results were as follows: Ginseng saponin was cytotoxic to osteoblast at concentration exceeding $250{\mu}g/ml$ for longer than 24 hours in tissue culture(p<0.01). In RT-PCR analysis, steady state MMP-13 mRNA levels were increased approximately 350% by $IL-1{\beta}$, and 400% by PTH when normalized to untreated control. $IL-1{\beta}-indued$ MMP-13 mRNA expression was reduced 50% by pretreatment with ginseng saponin. But ginseng saponin didn't inhibit MMP-13 expression from PTH stimulated cells. This results suggest that ginseng saponin Inhibit $IL-1{\beta}-indued$ MMP-13 mRNA expression.

• Elastomers and Composites
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• v.47 no.4
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• pp.347-354
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• 2012

There exist many merits in designing products and setting operational condition when computer aided engineering (CAE) is adopted in injection molding process. CAE also gives increasing efficient of molding, reducing developing time of product, and maintaining high quality products. Specially, it suggests design guidelines for new products and reducing wasting time to get steady state. Two and three dimensional computer simulations are available in injection molding and those results are somewhat different. However there are no guidelines for 2D and 3D computer simulations in using CAE in injection molding even though it is widely used in plastic industry. In this study, two and three dimensional computation results were compared for various part thickness, part shape, and number of finite element. Subsequently computational results were compared with experimental data such as pressure and temperature. The guidelines in two and three dimensional CAE analysis have been suggested through this study.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.20 no.43
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• pp.175-195
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• 1997

The learning curve has an important effect the growth of corporation. But, in Korea, the study and inference on the learning rate of each industry are unprepared, and so, Korean industires have difficult in productivity and cost. At this point, this study infers the learning rate of the oil industries and investigates the productivity and growth of them. In conclusion, this study presents the direction of the oil industries' development. With the intention of this objects, this study seizes the status which is concerned the total quantity, the operating rate, the plant capacity, the indicators concerning productivity, the investment of R & D and the scales, and then, infers and verifies the relevancy in connection with the learning rate. In the oil industry, the average rate of learning is 65.96% from 1982 to 1994 which the total quantity and the average operation time are used to infer the rate. To observe the low rate within a same period of time, this study takes the consequences that the learning rate is almost indentical with them each year. This steady state is caused by a difference between the employee and the decision maker about the acquirement and assimiliated of technology. When the high-quality technologies posses the environment to applicate in the scene of labor with them, this technology applies to the productivities. As the learning rate increases, the productivity has more effectiveness. The result of analysis about the effectiveness of the learning rate follows that the R & D unfoldes to exist and does not contribute to the growth of the oil industry. To analyze the variables of the growth, such as the learning rate, the investement of R & D, the operating rate and the gross value added to property, plant and equipment, the model is established and examined. The business strategy in the oil industry must be developed to achive the internal growth as well as the external.

• Journal of the Korea Convergence Society
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• v.3 no.4
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• pp.35-44
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• 2012

In this study, a simulation program is developed in order to investigate non steady-state cornering performance of 6WD/6WS special-purpose vehicles. 6WD vehicles are believed to have good performance on off-the-road maneuvering and to have fail-safe capabilities. But the cornering performances of 6WS vehicles are not well understood in the related literature. In this paper, 6WD/6WS vehicles are modeled as a 18 DOF system which includes non-linear vehicle dynamics, tire models, and kinematic effects. Then the vehicle model is constructed into a simulation program using the MATLAB/SIMULINK so that input/output and vehicle parameters can be changed easily with the modulated approach. Cornering performance of the 6WS vehicle is analyzed for brake steering and pivoting, respectively. Simulation results show that cornering performance depends on the middle-wheel steering as well as front/rear wheel steering. In addition, a new 6WS control law is proposed in order to minimize the sideslip angle. Lane change simulation results demonstrate the advantage of 6WS vehicles with the proposed control law.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.1
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• pp.35-44
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• 1998

In this paper, input LC filter design of diode rectifiers considering filter V A rating reduction has been propoesd. It consisted of an input LC parallel resonent tank whose inductor and capacitor values are se$.$ lected so that the input filter presents an infinite impedance to harmonic input ac current component. The operation of proposed input filter has been analyzed in detail under steady state conditions. Performance evaluation and related design data have been provided on Per Unit basis for the proper implementation of diode rectification system. Finally, Detailed input and output current analysis has shown that the proposed input filter yield high quality input ac current waveforms, in particular, high input power factor values and more reliabilty which reducing the V A rating of passive components as compared to the standard type LC filter.filter.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.11a
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• pp.415-420
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• 2005

This paper presents the two lossless auxiliary inductors-assisted voltage source type half bridge (single ended push pull: SEPP) series resonant high frequency inverter for induction heated king roller in copy and printing machines. The simple high-frequency inverter treated here can completely achieve stable zero current soft switching (ZCS) commutation for wide its output power regulation ranges and load variations under its constant high frequency pulse density modulation (PDM) scheme. Its transient and steady state operating principle is originally described and discussed for a constant high-frequency PDM control strategy under a stable ZCS operation commutation, together with its output effective power regulation characteristics-based on the high frequency PDM strategy. The experimental operating performances of this voltage source SEPP ZCS-PDM series resonant high frequency inverter using IGBTs are illustrated as compared with computer simulation results and experimental ones. Its power losses analysis and actual efficiency are evaluated and discussed on the basis of simulation and experimental results. The feasible effectiveness of this high frequency inverter appliance implemented here is proved from the practical point of view.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.4
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• pp.309-316
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• 2011

A PLL system has widely used for synchronizing the grid voltage at the grid-connected inverter for supplying power from the PV generation systems. In this paper, a PLL algorithm without both the loop filter and PI controller is suggested for improving the performance of synchronization at the single-phase and three-phase grid connected inverters. In order that the output voltage of a phase detector in the PLL has only a dc voltage, and it approaches to 0 when the synchronization signal is locked to the grid voltage, the feedback signals are determined by using two-phase voltages. After the PLL system with a proportional controller is modelled with the small signal analysis, the stability and steady-state error are investigated. Through the simulation studies and experimental results, the performances of the proposed PLL algorithm are verified.

• Journal of the Korean Society of Clothing and Textiles
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• v.26 no.7
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• pp.958-969
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• 2002

No one doubts that textile and apparel industries have contributed to economic miracles of the export-led growth in Korea. However, by the turning of 1990′s, these sectors have encountered many problems such as decreasing of domestic production and exports mainly due to wage rise and shortage. Therefore, foreign direct investment to the low labor cost countries has been enlarged for a way of improving its competitiveness and increasing exports. However, no intensive study has been made exploring current investments and future directions. This study focuses Vietnam as one of the promising overseas investment countries. The purposes of this study are to analyze current investment status of Korean textiles and apparel firms in Vietnam, to explore merits and problems Vietnam has, and to present useful implications and strategies for Korean textiles and apparel companies. Analysis of current secondary data suggests that Korean apparel industry, rather than textiles industry, have invested more in Vietnam, mostly in southern Ho Chi Minh City. Investments of Korean apparel and textile firms have shown steady increase from 1990 but have turned to a decrease from 1995. Findings suggested that Vietnam has merits for attracting foreign investment since it provides relatively cheap labor and outstanding skillful hands suitable for apparel and textiles industries. In addition, because of EU quota increase and the trade agreement between Vietnam and USA it is likely for firms in Vietnam to increase exports to EU and USA Rapid expansion of domestic apparel market and "Korean trend (Han Rue)" in Vietnam resulted from successful star marketing of Korean firms are another merits Vietnam has to the Korean fm. However, regulations of central government, low efficiency of bureaucratic and stiff administrative process, difficulty of making decision in case of joint venture, lack of social overhead capital, high factory construction costs, weak construction condition, and the excessive competition among investment enterprises have found to be problems. Based on pros and cons of investment to Vietnam, marketing strategies, practical implications and future directions were suggested.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.7
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• pp.118-126
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• 2003

In this study, a battery charge and discharge regulator of modular type is designed as paralleled bi-directional converter that is possible to provide the power without failure not only in the steady state but also in the transient period by the step load variation or the unexpected faults among the converter modules. Each converter module is designed to get stability, performance, reliability, and maintainability and the average current mode method used for controller has the advantages such as noise immunity, fast response, and the real average current signal acquisition. The equivalent model and small signal model for the paralleled battery chargerIdischarger are presented, and also the transfer functions are analyzed for the CCM(Continuous Charge Mode), CDM(Continuous Discharge Mode) and DDM(Discontinuous Discharge Mode). The experiments of the paralleled bi-directional converter are carried out in the step load variation, and in faults of one converter module respectively. And the performance of paralleled bi-directional converter is verified via the experimental results.