• 한국자동차공학회논문집
• /
• 제12권2호
• /
• pp.45-53
• /
• 2004

An experimental study was carried out to obtain the fundamental data about the effects of radicals induced injection on premixture combustion. A constant volume combustor divided to the sub-chamber and the main chamber was used. The volume of the sub-chamber is set up to occupy less than 1.5％ of that of whole combustion chamber. Radial twelve narrow passage holes are arranged between the main chamber and the sub-chamber. The products including radicals generated by spark ignition in the sub-chamber will derive the simultaneous multi-point ignition in the main chamber. While the equivalence ratio of pre-mixture in the main chamber and the sub-chamber is uniform. We have examined the effects of the sub-chamber volume, the diameter of passage hole, and the equivalence ratio on the combustion characteristics by means of burning pressure measurement and flame visualization. In the case of radical ignition method(RI), the overall turning time including the ignition delay became very short and the maximum burning pressure was slightly increased in comparison with those of the conventional spark ignition method(SI), that is, single chamber combustion without the sub-chamber. The combustible lean limit by RI method is extended to more ER=0.25 than that by SI method. Therefore the decrease of every emission including NOx and the improvement of fuel consumption is anticipated due to lean burn.

• 대한전자공학회논문지
• /
• 제22권1호
• /
• pp.41-45
• /
• 1985

디지탈 이동물체지시기 계통(DMTI System)에서 신호대잡음비(SNR)의 저하는 적정처리 전에 디지탈 이동물체지시기의 출력펄스를 weightlng시킴에 의하여 개선될 수 있구 #정상살기의 수가 증가함에 따라 신호대잡음비가 개선됨을 나타내었다. Optimum weighting으로 얻어진 신호대잡음비는 binomial weighting으로 얻어진 것보다 더 커짐을 알았다. 컴퓨터 시뮬레이션 결과를 통하여 각각의 경우에 대한 신호대잡음비의 배선특성을 나타낸다.

• 암석학회지
• /
• 제5권2호
• /
• pp.135-141
• /
• 1996

La-Ce법은 최근에 새로 개발된 연대측정법이다. 특히 La 및 Ce은 회토류원소군의 일원으로서 Sm-Nd법과 대비하여 해석할 경우, 지각물질 및 맨틀물질의 진화과정을 해석하는 데 있어서 아주 유용하게 쓰일 수가 있다. 본 논문에서는 La-Ce법의 기본개념에 대한 소개와 도불이 이를 토대로 하여 강원도 임원지 역의 우백질 화강편마암과 중국 요령성 안산지역에 분포하는 칼륨부화 화강암에 대하여 그 기원물질의 경희토류 분포양상을 유추하였다. 칼륨부화 화강암의 Sm-Nd년대는 $3.16{\pm}0.06$Ga($2{\sigma}$)이며 $^{143}Nd/^{144}Nd$초기치는 $0.50846{\pm}0.00005$(${\varepsilon}_{Nd}$=-1.5)이다. 이 초기치는 칼륨부화 화강암이 지각 내에서의 화성활동에 형성되어졌음을 의미한다. Nd 및 Ce 동위원소비의 결과에 이하면, 우백질 화강편마암과 칼륨부화 화강암은 CHUR과 거의 유사한 물질로부터 분화되었음을 알 수가 있다. 그리고 중국 동북부 료령성지역의 지각형성시기는 3.5Ga 보다 더 오래된 것으로 사료된다.

• 한국해안·해양공학회논문집
• /
• 제27권2호
• /
• pp.135-141
• /
• 2015

본 연구에서는 사석 방파제에 사용되는 대표적 방사형 소파 블록인 Tetrapod, Rakuna-IV 및 Dimple 등에 대하여 각각 두 가지의 정적 피복 방법을 제안하고 각 방법에 대한 안정계수를 수리실험을 통하여 결정하였다. Tetrapod와 Rakuna-IV는 피복 방법에 상관없이 비슷한 안정계수를 보인 반면, Dimple은 피복 방법에 따라 약간 다른 안정계수를 보였다. Dimple이 가장 큰 안정계수를 나타낸 반면, Tetrapod가 가장 작은 안정계수를 나타내었다. Tetrapod와 Rakuna-IV를 정적 하였을 경우에는 난적보다 약간 큰 안정계수를 보인 반면, Dimple을 정적 했을 경우에는 난적보다 훨씬 큰 안정계수를 나타내었다. 하지만, 본 연구에서 제안한 Dimple의 정적 방법은 공극률이 매우 작고 일층 피복 블록과 비슷한 거동을 보여서 급격한 파괴가 발생할 수 있으므로 주의를 요한다.

• Journal of Welding and Joining
• /
• 제12권1호
• /
• pp.59-72
• /
• 1994

This paper presents an on-line quality monitoring and control method to obtain a uniform weld quality in gas metal arc welding (GMAW) processes. The geometrical parameters of the weld pool such as the top bead width and the penetration depth plus half back width are utilized to assess the integrity of the weld quality. Since a good quality weld is characterized by a relatively high depth-to-width ratio in its dimensions, the second geometrical parameter is regulated to a desired one. The monitoring variables are the surface temperatures measured at various points on the top surface of the weldment which are strongly related to the formation of the weld pool The relationship between the measured temperatures and the weld pool size is implemented on the multilayer perceptrons which are powerful for realization of complex mapping characteristics through training by samples. For on-line quality monitoring and control, it is prerequisite to estimate the weld pool sizes in the region of transient states. For this purpose, the time history of the surface temperatures is used as the input to the neural estimator. The control purpose is to obtain a uniform weld quality. In this research, the weld pool size is directly regulated to a desired one. The proposed controller is composed of a neural pool size estimator, a neural feedforward controller and a conventional feedback controller. The pool size estimator predicts the weld pool size under growing. The feedforward controller compensates for the nonlinear characteristics of the welding process. A series of simulation studies shows that the proposed control method improves the overall system response in the presence of changes in torch travel speed during GMA welding and guarantees the uniform weld quality.

• 한국소음진동공학회논문집
• /
• 제15권8호
• /
• pp.897-903
• /
• 2005

When driving on uniformly tining concrete pavement road, the whine noise which has high spectrum at the specific frequency related to the uniform tining space exist. In this paper, a randomization method of tining space for concrete pavements is proposed to reduce the whine noise. The proposed method is developed based on the LCG(linear congruential generator) algorithm. The design parameters used in the method are number of different tining space, ratio of each tining space, total linings of each size. sequence of actual tining under given constant drag length and texture. Monte Carlo simulations are used to validate the proposed method.

• 동력기계공학회지
• /
• 제5권1호
• /
• pp.104-109
• /
• 2001

The stress distributions of hydranlic actuator cylinder tube acting in uniform inner pressure were analysed by the boundary element method(BEM). STKM13C tube was utilized for machine structural purposes model, its inner radius was 100 mm and outer radius was 140 mm. Axial length was semi-infinite and the isoparametric element of BEM was used. Radial and tangential stresses are maximum(-20.3 MPa and 52 MPa) at the inner radius and the minimum at the outer radius of the hydraulic actuator cylinders for an industrial systems. Stress diminution ratio was about 0.6 MPa/mm. And then coincidence between the simulation techniques as exact results(Lame' equation) and finite element method(FEM) is found to be fairly good, showing that the proposed analysis by BEM is reliable.

• 한국지진공학회논문집
• /
• 제7권4호
• /
• pp.63-69
• /
• 2003

본 연구에서는 단자유도계 시스템에서 작성한 이력에너지 스펙트럼과 누적된 변위 연성비 스펙트럼을 이용하여 비좌굴 가새골조의 내진설계법을 제안하였다. 먼저 목표 연성비에 해당하는 이력에너지 스펙트럼과 누적된 연성비 스펙트럼을 작성하였다. 주어진 목표 변위를 만족하기 위하여 필요한 가새의 단면적은 이력에너지 요구량과 가새에 의하여 소산된 누적 소성에너지를 같다고 하여 산정하였다. 스펙트럼을 작성하고 설계절차의 유효성을 검증하기 위하여 20개의 지진기록을 이용하였다. 제안된 방법에 따라 설계된 3층과 8층 비좌굴 가새골조의 해석결과에 따르면 최상층 변위의 평균값이 성능 목표 변위에 잘 부합됨을 알 수 있다. 또한 층간변위는 구조물 높이에 따라 비교적 일정하였는데 이것은 손상 분포가 일정하기 때문에 바람직하다. 그러므로 제안된 에너지 설계법은 기존 강도설계법의 대안으로 비좌굴 가새골조의 신뢰할만한 설계법이라고 할 수 있다.

• 한국가시화정보학회지
• /
• 제18권3호
• /
• pp.42-51
• /
• 2020

This study performs a numerical simulation of lid driven rectangular cavity flow with different aspect ratios of k = 0.5 to 4 under Reynolds 100, 1,000, 10,000 by using multi-relaxation time (MRT) Lattice Boltzmann Method (LBM). In order to achieve better convergence, well-posed boundary conditions in the domain should be defined such as no-slip condition on side and bottom solid wall surfaces and uniform horizontal velocity on the top of the cavity. This study focuses on the flow inside different shape of rectangular cavity with the aim to observe the effect of the Reynolds number and aspect ratio on the flow characteristics and primary/secondary vortex formation. In order to validate the study, the results have been compared with existing works. The result shows that the Reynolds number and the aspect ratio both has substantial effects on the flow inside the lid-driven rectangular cavity.

• Computers and Concrete
• /
• 제19권6호
• /
• pp.677-687
• /
• 2017

The nonlinear buckling response of nano composite anti-symmetric functionally graded polymeric microplate reinforced by single-walled carbon nanotubes (SWCNTs) rested on orthotropic elastomeric foundation with temperature dependent properties is investigated. For the carbon-nanotube reinforced composite (CNTRC) microplate, a uniform distribution (UD) and four types of functionally graded (FG) distribution are considered. Based on orthotropic Mindlin plate theory, von Karman geometric nonlinearity and Hamilton's principle, the governing equations are derived. Generalized differential quadrature method (GDQM) is employed to calculate the non-linear buckling response of the plate. Effects of FG distribution type, elastomeric foundation, aspect ratio (thickness to width ratio), boundary condition, orientation of foundation orthotropy and temperature are considered. The results are validated. It is found that the critical buckling load without elastic medium is significantly lower than considering Winkler and Pasternak medium.