• Aerospace Engineering and Technology
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• v.9 no.1
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• pp.106-115
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• 2010

Because of space limitations, interferences between antennas of the KSLV-I communication systems occur and their effects become worse during all sorts of tests such as the flight test using a light plane. In this paper, coupled signal magnitude is calculated using the FDTD method. The theory of the FDTD, absorbing boundary condition, source input technique, and post processing of data are explained. The calculated coupling factor between two IFAs, which have 2 GHz resonance frequency and placed 5 cm apart, is -12.7 dB. Applied coupling calculation method can be effectively used for KSLV-I performance analysis, subsystem design, antenna arrangement, and communication link budget for the next space launch vehicle.

• Journal of Korean Society of Steel Construction
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• v.12 no.5 s.48
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• pp.569-579
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• 2000

An improved multi-level (IML) optimization algorithm using automatic differentiation (AD) of framed structures is proposed in this paper. For the efficiency of the proposed algorithm, multi-level optimization techniques using a decomposition method that separates both system-level and element-level optimizations, that utilizes and an artificial constraint deletion technique, are incorporated in the algorithm. And also to save the numerical efforts, an efficient reanalysis technique through approximated structural responses such as moments and frequencies with respect to intermediate variables is proposed in the paper. Sensitivity analysis of dynamic structural response is executed by AD that is a powerful technique for computing complex or implicit derivatives accurately and efficiently with minimal human effort. The efficiency and robustness of the IML algorithm, compared with a plain multi-level (PML) algorithm, is successfully demonstrated in the numerical examples.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.12
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• pp.8791-8799
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• 2015

In this paper, One-way car-sharing System represents the verification system consider events in revenue effects. Revenue which the time and distance represented the graph, compare one-way vehicle relocate car-sharing system which proven in existing international papers with one-way vehicle relocate car-sharing system consider the event currently in the Korea. Especially, The maximum profit according to the distance and time were assessed through multiple linear regression analysis, and there are probable maximum loss allow for the maximum loss. The company suggested using the event as a discount coupon to customers through various marketing strategies, and then focused on increasing customer demand. So, Correlation analysis to determine the maximum revenue of the actual travel distance and time were carried out through Non-linear Regression.

• Journal of Acupuncture Research
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• v.24 no.5
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• pp.151-170
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• 2007

Backgraounds : Recent studies provide the evidences that the efficacy of acupuncture may be no better than placebo or inconclusive. These results are very different from those of the actual clinical situations in many acupuncture medical institutions. Objectives : The present study was designed to evaluate the influencing factors which affect the efficacy of acupuncture scale(FEAS) as the methodological assessment tool of acupuncture for examining acupuncture interventions and to demonstrate the importance of it in randomized controlled trials of acupuncture. Data sources : Electronic data were retrieved from NDSL, Pubmed, sciencedirect, LWW, OVID, Black-Well Synergy, Wiley Interscience, EBSCO HOST, springer, PML, and Kluwer. No electronic data were collected from MEDLIS and MEDLAS. Study selection : The inclusion criteria were five systematic reviews included in Alberta study and all randomized controlled trials obtained from their references. Study analysis : The acupuncture rationale, methods of stimulation, treatment regimen, and the practitioner's background were rated by FEAS, and the scores were compared with those by other methodological assessment tools. Results : The number of positive conclusions of high-rank RCTs by FEAS was the same as or higher than that of high-rank RCTs by other methodological assessment tools. Conclusions : We have analysed 5 systematic reviews and their objectives 58 RCTs using FEAS. Practitioner's background has been described slightly in some reviews and studies. It may directly influence the effectiveness of acupuncture negatively in the systematic reviews.

• Journal of Korean society of Dental Hygiene
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• v.12 no.3
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• pp.533-541
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• 2012

Objectives : The purpose of this study was to evaluate the effects of tooth bleaching agent contained 35% hydrogen peroxide on the color, microhardness and surface roughness of tooth-colored restorative materials. Methods : Four types of tooth-colored restorative materials, including a composite resin(Filtek Z350 ; Z350), a flowable composite resin(Filtek P60 : P60), a compomer(Dyract$^{(R)}$ AP ; DY), and a glass-ionomer cement(KetacTM Molar Easymix ; KM) were used in the study. The specimens($8mm{\times}5mm$) were made by using a customized acrylic mold. Each material was divided into two groups equally(n=40) : experimental group(35% HP) and control group(distilled water). 35% HP group was treated 30 mim/5 days for 15 days. Each 30 minute treatment session consisted of two 15 minute cycles of gel application with 20 second light exposure. The authors measured the color, microhardness, and roughness of the specimens before and after bleaching. The data were analyzed with ANOVA and T-test. Results : 35% HP group showed an apparent color change(${\Delta}E^*$) than control group. In particular, DY and KM showed a noticeable color change and statistically significant differences(p<0.05). 35% HP group showed a reduction in microhardness. Z350 and P60 does not have a statistically significant difference(p>0.05), DY and KM showed a statistically significant difference(p<0.05). Percentage microhardness loss(PML) of control group was 0.6 to 5.5% in the group, 35% HP group was 6.6 to 34.6%. Roughness was increased in 35% HP group after bleaching. Especially DY and KM were significantly increased(p<0.05). Conclusions : Bleaching agents may affect the surface of existing restorations; therefore, they should not be used indiscriminately when tooth-colored restorations are present.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.11
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• pp.28-33
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• 2002

In this paper, the impedance-tuned monopole microstrip antenna designed for PCS is analyzed using finite difference time domain(FDTD) method. The perfectly matched layer(PML) absorbing material condition proposed by Berenger is used for the truncation of finite difference time domain lattice. A Gaussian pulse is selected as an excitation signal and a resistive voltage source model is used to reduce the error caused by the reflection waves. The FDTD method is inherently a near field technique. Therefore, the near field to far field transformation is need to compute far field antenna parameters such as radiation patterns and gain. The near field to far field transformation can be done both in the time domain and the frequency domain. We use the frequency domain transformation to compute the far field radiation patterns at single frequency. All the numerical results obtained by the FDTD method are compared with simulation results using the HFSS software. Good agreements are obtained in all cases.

• Journal of Environmental Science International
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• v.15 no.8
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• pp.719-725
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• 2006

Since low-floor apartments ate vertically closer to patting lots and roadways, it is hypothesized that residents in low-floor apartments may be exposed to elevated ambient levels of motet vehicle emissions compared to residents in high-floor apartments. The present study examined this hypothesis by measuring two motor vehicle source-related pollutants(CO and PM10) in ambient air of high-rise apartment buildings within the boundary of industrial complexes according to atmospheric stability The ambient air concentrations of CO and PM10 were higher for low-floor apartments than for high-floor apartments, regardless of atmospheric stability, The median concentration ratio of the low-floor air to high-floor alt ranged from 1.3 to 2.0, depending upon atmospheric stabilities, seasons and compounds. Moreover, the CO and PM10 concentrations were significantly higher in the winter and in the summer, regardless of the Hoot height. Atmospheric stability also was suggested to be important for the residents' exposure of high-rise apartment buildings to both CO and PM10. The median ratios of surface inversion air to non-surface inversion air ranged from 1.2 to 1.7 and from 1.0 to 1.6 lot PM10 and CO, respectively, depending upon seasons. Conclusively, these parameters(apartment floor height, season, and atmospheric stability) should be considered when evaluating the exposure of residents, living in high-rise apartment buildings, to CO and PM10. Meanwhile, the median PMl0 outdoor concentrations were close to or higher than the Korean annual standards for PM10, and the maximum PM10 concentrations substantially exceeded the Korean PM10 standard, thus suggesting the need for a management strategy for ambient PM 10. Neither the median nor the maximum outdoor CO concentrations, however, were higher than the Korean CO standard.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.7_spc
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• pp.485-494
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• 2016

The risk-based assessment, also called time-based assessment of structure is usually performed to provide seismic risk evaluation of a target structure for its entire life-cycle, e.g. 50 years. The prediction of collapse probability is the estimator in the risk-based assessment. While the risk-based assessment is the key in the performance-based earthquake engineering, its application is very limited because this evaluation method is very expensive in terms of simulation and computational efforts. So the evaluation database for many archetype structures usually serve as representative of the specific system. However, there is no such an assessment performed for building stocks in Korea. Consequently, the performance objective of current building code, KBC is not clear at least in a quantitative way. This shortcoming gives an unresolved issue to insurance industry, socio-economic impact, seismic safety policy in national and local governments. In this study, we evaluate the comprehensive seismic performance of an low-rise residential buildings with discontinuous structural walls, so called piloti-type structure which is commonly found in low-rise domestic building stocks. The collapse probability is obtained using the risk integral of a conditioned collapse capacity function and regression of current hazard curve. Based on this approach it is expected to provide a robust tool to seismic safety policy as well as seismic risk analysis such as Probable Maximum Loss (PML) commonly used in the insurance industry.

• Journal of electromagnetic engineering and science
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• v.6 no.1
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• pp.47-52
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• 2006

The objective of this study is to evaluate the effects of size and permittivity on the specific absorption rate(SAR) values of rat brains during microwave exposure at mobile phone frequency bands. A finite difference time domain (FDTD) technique with perfect matching layer(PML) absorbing boundaries is used for this evaluation process. A color coded digital image of the Sprague Dawley(SD) rat based on magnetic resonance imaging(MRI) is used in FDTD calculation with appropriate permittivity values corresponding to different tissues for 3, 4, 7, and 10 week old rats. This study is comprised of three major parts. First, the rat model structure is scaled uniformly, i.e., the rat size is increased without change in permittivity. The simulated SAR values are compared with other experimental and numerical results. Second, the effect of permittivity on SAR values is examined by simulating the microwave exposure on rat brains with various permittivity values for a fixed rat size. Finally, the SAR distributions in depth, and the brain-averaged SAR and brain 1 voxel peak SAR values are computed during the microwave exposure on a rat model structure when both size and permittivity have varied corresponding to different ages ranging from 3 to 10 weeks. At 900 MHz, the simulation results show that the brain-averaged SAR values decreased by about 54 % for size variation from the 3 week to the 10 week-old rat model, while the SAR values decreased only by about 16 % for permittivity variation. It is found that the brain averaged SAR values decreased by about 63 % when the variations in size and permittivity are taken together. At 1,800 MHz, the brain-averaged SAR value is decreased by 200 % for size variation, 9.7 % for permittivity variation, and 207 % for both size and permittivity variations.

• Journal of Korean Physical Therapy Science
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• v.29 no.4
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• pp.43-53
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• 2022

Background: It is suggested that the decline in functional level due to aging influences the increase in traffic accidents among elderly drivers. Among the functions related to the driving behavior of older drivers, physical function is related to muscle strength and motor control, and aging causes deterioration of motor control and a defect in motor output variability. Method: Data Search The online databases used for literature search are PubMed, ProQuest(PML), NDSL, and literature searches were conducted from April 19 to April 26, 2022. For the search, 'aging', 'driving', and 'braking' were used in the investigation. Results: The physical functions related to the braking ability of elderly drivers were analyzed in muscle strength, reaction ability, motor control, and other related factors. In terms of muscle strength, 3 studies analyzed the above factors. 8 studies analyzed the above factors for response ability. For motor control, two studies analyzed the above factors. In addition, related factors were analyzed in one piece. Conclusion: As a result of the analysis, physical function for reaction ability showed the highest frequency, followed by the strength item with the highest frequency. This study suggests that factors that can increase physical function must be included in the development of a rehabilitation program for the driving ability of the elderly.