• Proceedings of the KIEE Conference
• /
• 2008.07a
• /
• pp.890-891
• /
• 2008

본 논문에서는 37인치 LCD TV의 패널 전원 공급용 회로로 사용되는 120W급 LLC 공진형 컨버터의 정상 상태 해석을 하였다. 특히, 종래와 달리 TV의 소비 전력 절감을 위해 넓은 범위로 동작하는 램프의 PWM Dimming 기능 동작시의 넓은 동작 영역에서의 공진형 컨버터의 정상 상태 해석을 하였다. TV SET의 동작 중 발생할 수 있는 공진형 컨버터 회로의 전단 회로인 Power Factor Correction 회로의 전압 변동과 또한 넓은 범위로 동작하는 램프의 PWM Dimming 기능 동작시의 부하 변동을 고려하여 LLC 공진형 컨버터의 정상 상태 해석을 하였다. 넓은 범위의 입출력 조건에서도 안정적으로 동작하는 컨버터 회로에 대한 이론적 분석과 실험을 통해 적용된 회로의 신뢰성과 우수성을 확인할 수 있었다.

• Journal of the Society of Naval Architects of Korea
• /
• v.41 no.5
• /
• pp.1-7
• /
• 2004

The Spar platform with deep draft is characterized as effective structure in extreme wave condition, which has larger natural period than that of waves in sea. In this paper, the time domain simulation of motion responses of Spar with catenary mooring line is presented in irregular waves. The memory effect is modeled by added mass at infinite frequency and convolution integrals in terms of wave damping coefficients. The added mass, wave damping coefficients and wave exciting forces are obtained from three-dimensional panel method in the frequency domain. The motion equations are consisted of forces for inertia, memory effect, hydrostatic restoring, wave exciting and mooring line. The forces of mooring line are modeled as quasi-static catenary cable.

• Journal of Digital Convergence
• /
• v.16 no.3
• /
• pp.1-12
• /
• 2018

The objective of this study is to explore the way to improve baby boom generation's ICT skills in their daily life. This study explores the effect of leisure activities on ICT skills. The analysis used 2016 Korea Media Panel data. Results show that the more leisure activities baby-boomers participate, the higher ICT skills they could get. The result of 2SLS regression also supports the leisure activities' effect on the improvement of ICT skills. More specifically, watching performing art such as movies, musicals, affects the improvement of the integrated ICT skills, and creative hobbies such as cooking, painting, affect the ability to use video contents and e-commerce; shopping affects the improvement of communication and information searching with a digital device. These findings suggest that leisure activities could improve ICT skills for baby boom generation who are familiar with face to face communication.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.35 no.5
• /
• pp.375-380
• /
• 2007

The nonlinear aerodynamic analysis of wing with control surface is performed using the frequency-domain panel method. To take into consideration the nonlinear aerodynamic characteristics of wing an iterative decambering approach is introduced. The iterative decambering approach uses the known aerodynamic characteristics of airfoil to calculate the aerodynamic characteristics of wing. The multi-dimensional Newton iteration is used to account for the coupling between the different sections of wing. The present method is verified by showing that it produces results that are in good agreement with experiments. The present method will be useful for the analysis of aircraft in the conceptual design because the present method can calculate promptly the nonlinear aerodynamic characteristics of wing with a few computing resources.

• Composites Research
• /
• v.13 no.5
• /
• pp.50-59
• /
• 2000

In this paper, two methods to suppress flutter of the composite panel are examined. First, in the active control method, a controller based on the linear optimal control theory is designed and control input voltage is applied on the actuators and a PZT is used as actuator. Second, a new technique, passive suppression scheme, is suggested for suppression of the nonlinear panel flutter. In the passive suppression scheme, a shunt circuit which consists of inductor-resistor is used to increase damping of the system and as a result the flutter can be attenuated. A passive damping technology, which is believed to be more robust suppression system in practical operation, requires very little or no electrical power and additional apparatuses such as sensor system and controller are not needed. To achieve the great actuating force/damping effect, the optimal shape and location of the actuators are determined by using genetic algorithms. The governing equations are derived by using extended Hamilton's principle. They are based on the nonlinear von Karman strain-displacement relationship for the panel structure and quasi-steady first-order piston theory for the supersonic airflow. The discretized finite element equations are obtained by using 4-node conforming plate element. A modal reduction is performed to the finite element equations in order to suppress the panel flutter effectively and nonlinear-coupled modal equations are obtained. Numerical suppression results, which are based on the reduced nonlinear modal equations, are presented in time domain by using Newmark nonlinear time integration method.

• Journal of Korea Multimedia Society
• /
• v.10 no.10
• /
• pp.1271-1283
• /
• 2007

To detect defect of FPD(flat panel displays) is very difficult due to uneven illumination on FPD panel image. This paper presents a method to detect various types of defects using the approximated image of the uneven illumination by B-spline. To construct a approximated surface, corresponding to uneven illumination background intensity, while reducing random noises and small defect signal, only the lowest smooth subband is used by wavelet decomposition, resulting in reducing the computation time of taking B-spline approximation and enhancing detection accuracy. The approximated image in lowest LL subband is expanded as the same size as original one by wavelet reconstruction, and the difference between original image and reconstructed one becomes a flat image of compensating the uneven illumination background. A simple binary thresholding is then used to separate the defective regions from the subtracted image. Finally, blob analysis as post-processing is carried out to get rid of false defects. For applying in-line system, the wavelet transform by lifting based fast algorithm is implemented to deal with a huge size data such as film and the processing time is highly reduced.

• Journal of Korean Library and Information Science Society
• /
• v.49 no.1
• /
• pp.193-214
• /
• 2018

This study aimed to exploratorily investigate the new roles of libraries in the era of K-MOOC. For this, potential roles were derived and categorized from former researches and practices. And to evaluate the appropriacy of those roles, two expert surveys were conducted. Panel A was comprised of 30 professors who had been running K-MOOC classes and Panel B was comprised of 30 librarians of Universities that had adopted K-MOOC. The result shows that they both agree about distinct roles of library as information provider such as licensing and providing digital contents requested from information users, while technological part, for example, recording video and audio, managing website, and providing open access, was considered inappropriate because those roles were already taken by CTLs. Also, professors agree that information literacy education is required for teachers not just for students as the speed of technological development is too swift and librarians agree that they have to equipped with core competence in preparation for upcoming change by creating added value, establishing closer relationship with various educational and technological institutes, and securing organizational flexibility.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.9B
• /
• pp.1108-1116
• /
• 2011

The visible light communication system that transmits data by controlling light emission of LED and receives data through photo detecter is considered as one of the strong candidates of the next generation wireless communication systems. The visible light communication provides both lighting and wireless communication wherever the LED lamps are installed. Due to the feature of visible light communication system, the communication is possible within the area that LED light reaches, and the communication quality depends on the light intensity received at the receiver. In this paper, we analyze the effects of LED panel position and lighting angel on communication channel quality in visible light communication systems. Through computer simulations, we prove that position of LED panel and light angle have a great impact on illuminance and SNR of the visible light communication systems.

• Journal of the Society of Naval Architects of Korea
• /
• v.36 no.1
• /
• pp.30-36
• /
• 1999

A surface panel method for the analysis of ducted propellers in both uniform and non-uniform onset inflow is developed. A low order, perturbation potential based panel method with an efficient numerical Kutta condition is used. The boundary surface is discretized with hyperboloidal panels and the boundary condition is applied at the panel centroids. The unsteady analysis is based on a time-step algorithm in time domain. Numerical implementation is employed into both steady and unsteady problems. The results with the resent method are shown to have good convergence on the circumferential distribution of circulation on the duct. The effect of the propeller tip clearance on the circumferential circulation on the duct is also presented Numerical results on forces and moments of the propeller and the duct are compared with other numerical results and experimental data.

• International Area Studies Review
• /
• v.13 no.3
• /
• pp.73-91
• /
• 2009

In this paper, we attempt to study the trend of regional disparity among Chinese provinces and examine the effects of globalization on the disparities adapting panel data approach. The panel data set utilized consists of the annual variables of 29 provinces during 18 years from 1990 to 2007. The trend of inter-provincial disparities in the 1990s with the expansive trend but the trend has started to decrease since 2000. The results of the China case study show clearly that the provincial international trade level and ratio variables perform on regional income disparities remarkably in all cases. It means that the large development of international trade do with increased among provincial disparity. While due to the large area in the provinces, there exist urban-rural disparities within provinces could be one of the main source of regional disparities. Therefore, along with western regions development policy various development policies against small cities are necessary for balanced regional economic growth in China.