• Journal of the Korean Society of Combustion
• /
• v.12 no.4
• /
• pp.31-38
• /
• 2007

An numerical study was conducted on superdetonative mode ram accelerator with length extended combustor. The computation condition was based on ISL's RAMAC30 II S225 experiment. For 50% length increased combustor, flame is not sustained. For the case of 60% and 70% increase, flame is successfully sustaind. But detonation wave is oscillating and acceleration is fluctuating. Extention of combustor is helpful for sustaing detonation wave but it may cause unstart.

• The Science & Technology
• /
• v.31 no.4 s.347
• /
• pp.22-23
• /
• 1998

세계적인 광통신전문가인 백운출(광주과학기술원 정보통신공학과)교수는 지난19890년 세계최초로 장파장용 단일모드 광섬유로서 광분산이 일어나지 않는 광섬유를 설계했고 '86년에 초고속 광섬유 연출공법을 개발함으로써 광섬유를 실용화하는 쾌거를 이뤘으며 이 공적으로 미국 학술원 회원으로 추대되는 영광을 안았다. '91년 미국에서 이룬 모든 학문적 업적을 뒤로 한 채 귀국하여 광주과학기술원에서 후진 양성에 힘을 쏟고 있는 백교수는 21세기 우리나라가 정보통신을 리할 수 있도록 하는 마지막연구열을 불태우고 있다.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.35D no.7
• /
• pp.25-31
• /
• 1998

Modal transmission-line is utilized to analyze the power coupling of optical directional coupler composed by two parallel guiding slabs. By defining a coupling efficiency .eta. amenable to rigorous supermodes and boundary conditions of modal functions, we evaluate the power transfer for TE mode of gainy coupler. The results reveal that optimized power exchange occurs at a novel wavelength .lambda.$_{op}$ , which is generally different from minimum gap .lambda.$_{min}$ between rigorous modes and phase-matching condition .lambda.$_{ph}$ .

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.14 no.2
• /
• pp.28-31
• /
• 1977

Normal modes of carrier waves due to longitudinal modulation in solids have been defined. The dispersion relationship of these waves in the presence of collision effects and thermal diffusion is derived and examined in detail. It is also shown that the carrier waves are reduced to the wellknown space-charge waves and electroacoustic hayes in special cases.

• Journal of Ocean Engineering and Technology
• /
• v.31 no.5
• /
• pp.364-370
• /
• 2017

A numerical model based on the mode superposition method is used to study the vortex-induced vibration response characteristics of a deep-sea riser such as steel catenary riser (SCR). A steel catenary riser can be modeled using a flexible cable with simple supports at both ends. The natural frequency, mode shape and mode curvature of the riser are calculated and the vortex-induced vibration response of the riser is obtained using the equilibrium of the input and output power. The mode superposition method is applied to the vibrational stresses for each mode to calculate the overall riser fatigue life.

• Journal of the Korean Society for Precision Engineering
• /
• v.31 no.1
• /
• pp.67-73
• /
• 2014

A reliability evaluation or prediction can be defined as MTBF which stands for mean time between failures (Exclusively for repairable failures). Spindle system has huge effect on performance of machine tools and working quality as well as is required of high reliability. Especially, it takes great importance in producing automobiles which includes a large number of working processes. However, it is unusually difficult to predict reliability because there are lack of data and research about reliability of spindle system. Standards and methods of examinations for reliability evaluation of machine tools are scarce at local and abroad as well. Therefore, this research is meant to improve the reliability of spindle system before mass produced with developing standards of reliability and methods of examinations through FMEA to assess reliability of spindle system in prototype stages of developing high speed spindle system of machining center.

• Journal of Advanced Marine Engineering and Technology
• /
• v.31 no.8
• /
• pp.911-917
• /
• 2007

Global primary energy demand is projected to increase by 1.7% per year from 2000 to 2030. Almost three-quaters of the increase in demand will come from the transportation sector. Fuel cell hybrid vehicle technology has the potential to significantly reduce energy and harmful emissions, as well as our dependence on foreign oil. In this paper, a systematic and logical methodology is developed and improved mainly to design light duty fuel cell hybrid electric vehicle. We investigated structure and characteristics of light duty FC hybrid vehicle carefully. It can easily be expanded to analyze vehicle-to-grid power connectable plug-in NeHEV. A fuel cell hybrid neighbourhood electric vehicle configuration has been studied in-depth utilizing the proposed methodology.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.31 no.6A
• /
• pp.409-415
• /
• 2011

Optimization Analysis of angle-ply laminated shells, having one pair of opposite edges supported, are investigated on the basis of the first-order shear deformation theory. The equations of motion of the shell are solved by the use of ritz method. A range of results are presented for composite shells to show the effects of lamination angle and number of layers on natural frequency. In addition, an analysis of the strain energy distributions is used as an aid for the better understanding of the vibration characteristics of the shells.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.41 no.1
• /
• pp.31-39
• /
• 2013

A Quad Tilt Wing UAV is a new concept hybrid UAV having the advantages of both fixed-wing and rotary-wing aircraft. This paper presents longitudinal flight dynamic characteristics of a Quad Tilt Wing UAV. The designed Quad Tilt Wing UAV is a configuration of a tandem wing type aircraft with an actuating motor and propeller mounted at each wing. Momentum theory is used to calculate the thrust, and nonlinear modeling is performed considering lift and drag generated by slip stream effect of propellers. Also, Force and moment variation at each tilting angle is considered. Static trim on longitudinal axis is analyzed via numerical simulation. Componentwise force contribution was analyzed at each trim mode. Dynamic characteristics were evaluated through eigenvalue analysis for a linear model at each flight mode. It is verified that longitudinal dynamic characteristics are changing from unstable to stable state by continuous transition of dominant poles.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.31 no.3
• /
• pp.121-125
• /
• 2018

In this study, finite element analyses of crack propagation along a sinusoidal interface are performed by using cohesive elements. BK law is used for cohesive zone to consider mixed mode traction-separation relation at the crack tip on a sinusoidal interface of a double cantilever beam specimen. The shape of a sinusoidal interface crack and the cohesive strength and the cohesive energies in mixed mode cohesive laws are varied in numerical experiments, and load-displacement curves at the ends of a double cantilever beam specimen are obtained to investigate the crack propagation behavior along a sinusoidal interface.