• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.5
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• pp.384-394
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• 1996

The propagation properties of square and Gaussian pulse signals on the microstrip line are investigated by using proper conventional models to meet the frequency range of a pulse, accuracy, and geometrical requirements of the microstrip line. Numerical integration technique which has its accuracy and is easily simulated, is used to obtain the time domain response of pulse signals. The dispersion of pulse signals is analyzed regarding to the relative permittivity $\varepsilon_r$, substrate height h, strip width w of the microstrip line and pulse width $\tau$ of signal pulse. The simulation results show that small relative permittivity and small rationale of w/h are advantageous for the dispersion of the pulse signals, and that pulse signals with small bandwidth cause smaller dispersion. The results of this paper are compatible to the trade-off determination of relative permittivity, substrate height, strip width and pulse width of signal pulse when a design of MIC and MMIC is necessary.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.4
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• pp.418-426
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• 2008

In this paper, investigations on the impedance characteristics of a DGS(Defected Ground Structure) slot in the groud plane of microstripline are presented in spectral domain and applied to the characteristic improvement of stepped impedance microstrip low pass filter(LPF). In this method, expressions for the impedance of a DGS slot are derived from self-reaction of the angular spectrum of plane waves and the discontinuity in the modal voltage. The numerical results are compared with those of the rigorous full-wave method and are shown to produce reasonably accurate data. And the stepped impedance microstrip low pass filter is designed and fabricated with the uniform and nonuniform DGS slots for improving the frequency responses. The experiments show that the proposed filter with slots in the ground plane has a wider stopband and sharper cutoff response.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.4
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• pp.427-435
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• 2008

In this paper, a stable marching-on in time(MOT) method with a time domain combined field integral equation(CFIE) is presented to obtain the transient scattering response from arbitrarily shaped three-dimensional conducting bodies. This formulation is based on a linear combination of the time domain electric field integral equation(EFIE) with the magnetic field integral equation(MFIE). The time derivatives in the EFIE and MFIE are approximated using a central finite difference scheme and other terms are averaged over time. This time domain CFIE approach produces results that are accurate and stable when solving for transient scattering responses from conducting objects. Numerical results with the proposed MOT scheme are presented and compared with those obtained from the conventional method and the inverse discrete Fourier transform(IDFT) of the frequency domain CFIE solution.

• Journal of the Korean Geotechnical Society
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• v.35 no.11
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• pp.63-74
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• 2019

Numerical liquefaction model and response history analysis procedure are verified based on dynamic centrifuge test results. The test was a part of the Liquefaction Experiments Analysis Project (LEAP). The model ground was formed inside of rigid box by using the submerged Ottawa F65 sand with a relative density of 55% and 5° of surface inclination. A tapered sinusoidal wave with a frequency of 1 Hz was applied to the base of the model box. Numerical analyses were performed by two dimensional finite difference method in prototype scale. The soil is modeled to show hysteretic behavior before shear failure, and Mohr-Coulomb model is applied for shear failure criterion. Byrne's liquefaction model was applied to track the changes in pore pressure due to cyclic loading after static equilibrium. In order to find an appropriate flow condition for the liquefaction analysis, numerical analyses were performed both in drained and undrained condition. The numerical analyses performed under the undrained condition showed good agreement with the centrifuge test results.

• Journal of the Korean Society of Clothing and Textiles
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• v.36 no.2
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• pp.206-217
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• 2012

This study examined the causal relationship between the Chinese preference for Korean cultural products (Korean talent, K-pop songs, TV dramas, and movies), for Korean fashion products, and their purchase intentions. The relationship between the Korea's national brand image and Chinese fashion leadership with the three variables was investigated. Data was collected from 580 Chinese in Dalian, China. The data was analyzed using frequency, correlations, reliability, and AMOS for path analysis. The results of this study were as follows. First, the preference for Korean talent, K-pop songs, TV dramas, movies, and fashion products showed that the Chinese had a positive response and the degree of preference for each item was similar. Second, the Chinese preference for Korean talent, movies, and TV dramas significantly influenced the preference for Korean fashion products. In addition, the Chinese preference for Korean fashion products significantly influenced the purchase intentions of Korean fashion products. Third, the Chinese preference for Korean talent and fashion products had a significant relationship with their fashion leadership. In addition, the preference for Korean talent, movies, TV dramas, K-pop songs, fashion products, and purchase intentions had the same positive relationship with Korea's national brand images. This study examined from a structural aspect how the preference of Korean intangible cultural products affected the purchase intention of Korean fashion products. This study explored that the preference for Korean cultural products transcended the popularity of the Korean popular culture with a subsequent national industrial and economic ripple effect that improved the national brand image.

• The Korean Journal of Health Service Management
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• v.7 no.2
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• pp.23-35
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• 2013

A study of the factors influencing the quality of life and social support of people suffering with mental disabilities, who use mental health centers. The purpose of the study includes the general characteristics of subjects, characteristics of the mental health center, the mean score of social support and quality of life of people living with mental disabilities. The 132 questionnaires were administered by meeting directly with subjects and personal visits. 112 Questionnaires were returned(85% response rate). Data was collected from mentally disabled patients in Chungnam Mental Health Center. difference in quality of life by using t-test, one way ANOVA table, the relationship between social support, quality of life by pearson correlation coefficients, and relevant factors affecting quality of life by multiple regression with the SPSS 19.0 program. This study revealed that the group that participated regularly in the day time rehabilitation program showed better social support and positive attitude to a better quality of life than the other group that participated irregularly. This result is directly proportional to the participation frequency to the program during the recent 3-month duration. Another correlation with religion was found in the study due to the fact that a buddhist group showed positive significance in quality of life than non-religious groups. The results show positive correlation between the improvement of the quality of life of patients living with mental disabilities and the social support they receive.

• International Journal of Automotive Technology
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• v.4 no.4
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• pp.181-191
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• 2003

Since the nonlinearity and uncertainties which inherently exist in vehicle system need to be considered in active suspension control law design, this paper proposes a new control strategy for active vehicle suspension systems by using a combined control scheme, i.e., respectively using a genetic algorithm (GA) based self-tuning PID controller and a fuzzy logic controller in two loops. In the control scheme, the PID controller is used to minimize vehicle body vertical acceleration, the fuzzy logic controller is to minimize pitch acceleration and meanwhile to attenuate vehicle body vertical acceleration further by tuning weighting factors. In order to improve the adaptability to the changes of plant parameters, based on the defined objectives, a genetic algorithm is introduced to tune the parameters of PID controller, the scaling factors, the gain values and the membership functions of fuzzy logic controller on-line. Taking a four degree-of-freedom nonlinear vehicle model as example, the proposed control scheme is applied and the simulations are carried out in different road disturbance input conditions. Simulation results show that the present control scheme is very effective in reducing peak values of vehicle body accelerations, especially within the most sensitive frequency range of human response, and in attenuating the excessive dynamic tire load to enhance road holding performance. The stability and adaptability are also showed even when the system is subject to severe road conditions, such as a pothole, an obstacle or a step input. Compared with conventional passive suspensions and the active vehicle suspension systems by using, e.g., linear fuzzy logic control, the combined PID and fuzzy control without parameters self-tuning, the new proposed control system with GA-based self-learning ability can improve vehicle ride comfort performance significantly and offer better system robustness.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.192-195
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• 2005

The silicon thin film solar cells were fabricated by 13.56 MHz PECVD (Plasma-Enhanced Chemical-Vapor Deposition) and 60 MHz VHF PECVD (Very High-Frequency Plasma-Enhanced Chemical-Vapor Deposition). We focus on textured ZnO:Al films prepared by RF sputtering and post deposition wet chemical etching and studied the surface morphology and optical properties. These films were optimized the light scattering properties of the textured ZnO:Al after wet chemical etching. Finally, the textured ZnO:Al films were successfully applied as substrates for silicon thin films solar cells. The efficiency of tandem solar cells with $0.25 cm^2$ area was $11.8\%$ under $100mW/cm^2$ light intensity. The electrical properties of tandem solar cells were measured with solar simulator (AM 1.5, $100 mW/cm^2)$ and spectral response measurements.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.12
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• pp.866-873
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• 2015

The transverse vibration of the deploying beam from rigid hub was analyzed by simulation and experiment. The linear governing equation of the deploying beam was obtained using the Euler-Bernoulli beam theory. To discretize the governing equation, the Galerkin method was used. After transforming the governing equation into the weak form, the weak form was discretized. The discretized equation was expressed by the matrix-vector form, and then the Newmark method was applied to simulate. To consider the damping effect of the beam, we conducted the modal test with various beam length. The mass proportional damping was selected by the relation of the first and second damping ratio. The proportional damping coefficient was calculated using the acquired natural frequency and damping ratio through the modal test. The experiment was set up to measure the transverse vibration of the deploying beam. The fixed beam at the carriage of the linear actuator was moved by moving the carriage. The transverse vibration of the deploying beam was observed by the Eulerian description near the hub. The deploying or retraction motion of the beam had the constant velocity and the velocity profile with acceleration and deceleration. We compared the transverse vibration results by the simulation and experiment. The observed response by the Eulerian description were analyzed.

• Journal of Physiology & Pathology in Korean Medicine
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• v.22 no.4
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• pp.993-999
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• 2008

Ischemic brain injury such as cerebral infarction is characterized by acute local inflammatory response mediated by cytokines. The mechanism of cytokines involved in cerebral infarction progression are uncompletely revealed yet. We investigated to find out the relationship between single nucleotide polymorphism (SNP) of interleukin 4 receptor(IL4R) and Oriental Medicine therapy efficacy in patients with cerebral infarction for 2 weeks. Oriental Korean Medicine therapies (herbal medicine and acupuncture) were applied daily and motor functions of patients were assessed using the modified cerebral vascular accident (MCVA) scores. Genotyping for IL4R polymorphism was done by pyrosequencing analysis. In IL4R genotypes and the frequency of alleles, there was no significant difference between cerebral infarction patients (n=124) and controls group (n=175). And there was also no significant difference among good and bad responders in cerebral infarction patients. In this study the IL4R genotype might not be the risk factor or a good predictive genetic marker for good and bad responders in cerebral infarction patients in Korean. Further studies including different cytokine genes will be necessary for the exact genetic markers.