• International Journal of Naval Architecture and Ocean Engineering
• /
• v.5 no.3
• /
• pp.392-403
• /
• 2013

For the analysis of radiating noise problems in medium-to-high frequency ranges, the Energy Flow Boundary Element Method (EFBEM) was developed. EFBEM is the analysis technique that applies the Boundary Element Method (BEM) to Energy Flow Analysis (EFA). The fundamental solutions representing spherical wave property for radiating noise problems in open field and considering the free surface effect in underwater are developed. Also the directivity factor is developed to express wave's directivity patterns in medium-to-high frequency ranges. Indirect EFBEM by using fundamental solutions and fictitious source was applied to open field and underwater noise problems successfully. Through numerical applications, the acoustic energy density distributions due to vibration of a simple plate model and a sphere model were compared with those of commercial code, and the comparison showed good agreement in the level and pattern of the energy density distributions.

• Journal of Aerospace System Engineering
• /
• v.3 no.1
• /
• pp.42-46
• /
• 2009

The 1st development of "Human Powered Aircraft(HPA)" in Korea has been conducting by KAFA(Korea Air Force Academy) from Aug. 2008 to now. HPA is an aircraft powered by directly human energy. The thrust provided by the human power may be the only source and that is weak. Therefore, light weight and strong structure is first requirement. In this paper, treating a basic conceptual design of HPA and material property and material choice for HPA. Also analysing the structure and checking the safety of HPA.

• Journal of Digital Convergence
• /
• v.9 no.1
• /
• pp.51-59
• /
• 2011

The objective of this paper is to identify factors influencing intention to use ubiquitous banking service focusing on potential users using a regression model. Through this, providers of ubiquitous banking services can get an idea of future development, including marketing strategy through the results of this analysis. This paper proposes that perceived usefulness is the most important factor influencing the uptake of ubiquitous service. Also in addition, ANOVA test shows that higher education level of the user can lead to the higher intention to use an ubiquitous banking service. In this study, we set up a model by using the most basic factor among influential factors presented in previous studies as an independent variable. However, other research variables which affect acceptance of ubiquitous service should be considered by thinking more diversely.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.14 no.5
• /
• pp.1181-1185
• /
• 1990

A failure evaluation diagram to evaluate fatigue fracture was developed. The relation between the fatigue limit and the threshold stress intensity factor for the short-cracked specimens of various materials including a piping carbon steel can be rationally predicted by the proposed method. It is shown that the coupled failure evaluation diagram for fatigue and ductile fracture is expecially useful for evaluation of the flaw tolerance as well as the margin of the safety of the pressure vessel and piping. Further, accumulation of fatigue data will be needed to construct an accurate fatigue failure evaluation diagram.

• Water for future
• /
• v.25 no.2
• /
• pp.79-87
• /
• 1992

This study is a model on the Migration Characteristics which developed by using the equations for conservation of mass, momentum and for lateral stability of the streambed, an the model can be examined for magnitude and location of near-bank bed scour as well as rates and direction of meander migration in which sine-Wave type rivers(SWR) of the small sinuosity. It is evident from this study that the transverse bed slope factor B' and transverse mass flux factor $ play significient roles, and show reasonable that the values are B'=4.0 and $=0.4 respectively . It will be a useful guide in planning, design, construction, and development of SWR river-basin projects.

• Journal of the Korea Safety Management & Science
• /
• v.11 no.3
• /
• pp.209-216
• /
• 2009

A development in method of evaluating the measurement precisions using approximate F tests and variance components from expected mean square (EMS) is investigated. The research proposes three-factor mixed measurement models with the fixed and random factors. Unrestricted and unconstrained design work was rarely studied, while restricted and constrained designs have been significantly discussed. The unrestricted and unconstrained designs assume to be an independence of interaction. The proposed evaluation method about the measurement precisions can be extended to four-factor random measurement model or mixed measurement model. The study also presents the three evaluation indexes of precisions such as R&RTR (Reproducibility & Repeatability-To-Total Precision Ratio), PTR (Precision-To-Tolerance Ratio), and SNR (Signal-To-Noise Ratio). Numerical examples are proposed to evaluate the approximate F tests with Satterthwaite degrees of freedom and three indexes using the measurement precisions from EMS.

• Journal of Institute of Control, Robotics and Systems
• /
• v.1 no.1
• /
• pp.50-57
• /
• 1995

In this paper, the design and the implementation of the controller for an articulate robot, which is developed in our Automatic Control Laboratory, are mainly discussed. The controller reduces software computational load via distributed processing method using multiple CPU's, and simplifies structures by the time-division control with TMS320C31 DSP chip. The method of control is based on the fuzzy-compensated PID control with scale factor, which compensates for the influence of load variation resulting from the various postures of the robot with conventional PID scheme. The application of the proposed controller to the robot system with DC servo-motors shows some excellent control capabilities. Also, the response characteristics of system for the various trajectory commands verify the superiority of the controller.

• Proceedings of the KIPE Conference
• /
• 2019.11a
• /
• pp.31-33
• /
• 2019

본 논문에서는 고주파 변압기 대신 무선 전력 전송 시스템을 적용해 양방향 전력 전송을 가능케 해주는 loosely coupled dual-active-bridge 컨버터에서, 코일 간 전송 효율을 높이기 위한 코일 형상 설계에 관한 연구를 진행하였다. 유한 요소법을 통해 여러 형태의 페라이트 코어에 대해 해석했다. 페라이트 코어 형태가 I-자 일 때 가장 높은 quality factor의 코일을 얻을 수 있었다. 또한, I-core의 ferrite plate의 크기에 따라 무선 전력 전송의 효율을 결정하는 코일의 coupling coefficient와 코일의 quality factor가 변하고 trade-off 관계가 있음을 확인하였다. 3cm의 air-gap에 대해 최대 효율을 가지는 코일 형상을 설계하여 시뮬레이션을 통해 97.8%의 코일간 전송효율을 얻었다.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.51 no.8
• /
• pp.385-390
• /
• 2002

This paper presents a substation expansion planning method with quantitative analysis using ANP. To calculate the reliability factor and economy factor of the system, reliability indices and total construction cost is used. With these factors, new ANP model which select the best plan either economy or reliability among various alternatives is developed. This model can assist the decision making for the system planner. The usefulness of the method is verified by applying it to the large-scaled distribution system.

• Proceedings of the KIEE Conference
• /
• 1998.07c
• /
• pp.1079-1081
• /
• 1998

This paper describes the dissipation factor measuring device for insulating oil in operating pole transformer by DSP(digital signal processor). After applying voltage to the sensor which is installed in a transformer, acquire source voltage and current of sensor using FFT techniques, then we could evaluate the dissipation factor of insulating oil. To improve measuring accuracy and processing speed, we use TMS320C31 DSP, FFT and data analysis techniques. Also we suggest deterioration criterion of insulating oil and compared the developed diagnosis device with schering bridge on deteriorated insulating oil. The result of this paper show that the developed measuring device can be used as diagnosis device for the pole transformers.