• 제목/요약/키워드: geometric parameters

검색결과 1,149건 처리시간 0.029초

기하학적 적응제어에 의한 엔드밀링머시인의 안내면 오차 규명 (Identification of guideway errors in the end milling machine using geometric adaptive control algorithm)

  • 정성종;이종원
    • 대한기계학회논문집
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    • 제12권1호
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    • pp.163-172
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    • 1988
  • 본 논문에서는 GAC방법을 이용하여 공작기계의 안내면오차를 수치제어 공작기계가 가지고 있는 가공조건의 조절 능력을 이용하여 가공오차를 보상제어 함으로써 규명(identification)할 수 있는 방법을 제시한다.

Nonlinear resonance of porous functionally graded nanoshells with geometrical imperfection

  • Wu-Bin Shan;Gui-Lin She
    • Structural Engineering and Mechanics
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    • 제88권4호
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    • pp.355-368
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    • 2023
  • Employing the non-local strain gradient theory (NSGT), this paper investigates the nonlinear resonance characteristics of functionally graded material (FGM) nanoshells with initial geometric imperfection for the first time. The effective material properties of the porous FGM nanoshells with even distribution of porosities are estimated by a modified power-law model. With the guidance of Love's thin shell theory and considering initial geometric imperfection, the strain equations of the shells are obtained. In order to characterize the small-scale effect of the nanoshells, the nonlocal parameter and strain gradient parameter are introduced. Subsequently, the Euler-Lagrange principle was used to derive the motion equations. Considering three boundary conditions, the Galerkin principle combined with the modified Lindstedt Poincare (MLP) method are employed to discretize and solve the motion equations. Finally, the effects of initial geometric imperfection, functional gradient index, strain gradient parameters, non-local parameters and porosity volume fraction on the nonlinear resonance of the porous FGM nanoshells are examined.

A Robust Pricing/Lot-sizing Model and A Solution Method Based on Geometric Programming

  • Lim, Sung-Mook
    • Management Science and Financial Engineering
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    • 제14권2호
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    • pp.13-23
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    • 2008
  • The pricing/lot-sizing problem of determining the robust optimal order quantity and selling price is discussed. The uncertainty of parameters characterized by an ellipsoid is explicitly incorporated into the problem. An approximation scheme is proposed to transform the problem into a geometric program, which can be efficiently and reliably solved using interior-point methods.

FXLMS 알고리즘 수렴성의 기하학적 해석 (Geometric Analysis of Convergence of FXLMS Algorithm)

  • 강민식
    • 대한전기학회논문지:시스템및제어부문D
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    • 제54권1호
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    • pp.40-47
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    • 2005
  • This paper concerns on Filtered-x least mean square (FXLMS) algorithm for adaptive estimation of feedforward control parameters. The conditions for convergence in ensemble mean of the FXLMS algorithm are derived and the directional convergence properties are discussed from a new geometric vector analysis. The convergence and its directionality are verified along with some computer simulations.

The Numerical Analysis of Spindle Motor Bearing Composed of Herringbone Groove Journal and Spiral Groove Thrust Bearing

  • Oh, Sang-Man;Rhim, Yoon-Chul
    • KSTLE International Journal
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    • 제2권2호
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    • pp.93-102
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    • 2001
  • Ball bearings have been widely used for the spindle motor bearing in various kinds of information storage devices. Recently many researchers have been trying to replace ball bearings with fluid film bearings because of their superior NRRO(non-repeatable runout) characteristics. In this study, a numerical analysis has been conducted for the complicate bearing system composed of herringbone groove journal bearing and spiral groove thrust bearing for the spindle motor of the information storage device. At first, spindle motor bearing is modeled as journal bearing part and thrust bearing part separately, and then observed various influences of geometric parameters. Previous studies had considered only the translational motion of the journal bearing. However, this study takes the additional 2-degree of freedom rotation into consideration to attempt to describe the real motion of the spindle bearing. As a result, rotational stiffness coefficients and rotational damping coefficients are obtained. In addition, a spindle bearing system made up of four bearings is modeled and interpreted at once and coefficients of dynamic characteristics of each bearing are obtained. Finally, an eigen analysis of bearing system is made with these results. Through this analysis, it is possible to estimate an unstable condition of the system for given geometric parameters and to propose a method which is able to avoid the unstable condition by a proper adjustment of geometric parameters.

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열전달 계수 최대화를 위한 마이크로 증발기의 최적 설계 (Optimal design of a micro evaporator to maximize heat transfer coefficient)

  • 성태종;오대식;서태원;김종원
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2007년도 춘계학술대회B
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    • pp.2097-2101
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    • 2007
  • This paper presents an optimal design of a micro evaporator which maximizes the heat transfer coefficient. Number of gaps, spanwise distance and streamwise distance are selected as the geometric design parameters. Mass flow rate of the refrigerant is selected as the non-geometric design parameter. Temperature at the surface of the heater is measured to valuate the heat transfer coefficient. Nine experiments are conducted using $L_9(3^4)$ orthogonal array. Maximum heat transfer coefficient is 640 W/$m^2K$ at the parameters of 2 gaps, 0.2 mm spanwise distance, 1.0 mm streamwise distance and 0.72 g/s mass flow rate. Among the 3 geometric parameters, the spanwise distance is the most sensitive parameter influencing the heat transfer coefficient. We conduct a second stage of experiment to increase the heat transfer coefficient by reselecting the mass flow rate. We concluded that 0.87 g/s is the optimized flow rate for an active micro cooler resulting in a heat transfer coefficient of 651 W/$m^2K$.

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조선용 강재의 $CO_2$레이저 GMA 하이브리드 용접에서 갭 브리징 능력 향상기술 개발 (Improvement of Gap Bridging Ability in $CO_2$ Laser-GMA Hybrid Welding)

  • 채현병;김철희;김정한;이세헌
    • Journal of Welding and Joining
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    • 제24권5호
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    • pp.49-56
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    • 2006
  • For laser welding in shipbuilding industry, gap bridging capability is one of the most important characteristics to achieve the high productivity and good weld quality. Recently, laser-GMA hybrid welding process is regarded as a distinctive method to overcome the tight gap tolerance with improving the productivity. In this study, the influence of process parameters on the bead formation was experimentally analyzed and the relationship between the process parameters and geometric imperfections was investigated. It was revealed that undercut, excessive weld metal, excessive penetration and incompletely filled groove were the major geometric imperfections. The optimized wire feeding and arc pressure were necessary to ensure the gap bridging ability. The approach to select the process parameters was conducted for butt welding with up to 2mm joint gap, in which the sound weld beads were generated without changing the welding speed.

스위치드 릴럭턴스 전동기의 토오크 리플 저감을 위한 기하학적인 파라미터와 전기적인 파라미터의 최적화 (Optimum Geometric and Electrical Parameter for minimization Torque Ripple of Switched Reluctance Motor)

  • 정성인;최재학;김윤현;김솔;이주;주민식;최동훈
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2001년도 하계학술대회 논문집 B
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    • pp.608-610
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    • 2001
  • In this paper, 6/4 Switched Reluctance Motor(SRM) which has simple structure and little switching element is selected basic analysis model. In order to reduce torque ripple causing noise and vibration, we execute optimization of geometric parameters (stator and rotor pole arc) and electrical parameters (turn-on angle and turn-of angle) by means of combining Fletcher-Reeves's Conjugate Directions and Finite Element Method (FEM) considering driving circuits. When considering the switching condition according to inductance profile, torque characteristics is influenced by geometric and electrical parameters importantly. The pole arc and switching angle of the optimum can also obtain the low torque ripple without high currents.

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R-134a를 사용한 자동차용 스크롤 압축기의 스크롤 형상변화가 성능에 미치는 영향 (Effect of Geometric Parameters on the Performance of an Automotive Scroll Compressor Using R-134a)

  • 이건호;김학수;조금남;유정열
    • 대한기계학회논문집B
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    • 제22권11호
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    • pp.1635-1646
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    • 1998
  • The present study investigated the effects of geometric parameters considered on the performance of an automotive scroll compressor by assuming ideal, semi-real and real gases for R-134a. The geometric parameters were center thickness of scroll, height of scroll and the size of discharge port. Fourth-order Runge-Kutta method was applied to solve the thermodynamic equations, leaking rate equation and the equation of motion of discharge valve for ideal, semi-real, and real gases. The volumetric and adiabatic efficiencies for semi-real and real gases differed little, but those for ideal gas differed by 18% and 25% compared with those for real gas at 2,000rpm. The volumetric efficiency changed little as the design angle of scroll (${\gamma}$) changed, but the adiabatic efficiency at ${\gamma}$ of $34^{\circ}$ was higher by 2.4% than that of $147^{\circ}$ for 2,000rpm. The volumetric and adiabatic efficiencies at scroll height of 29.8mm were higher by 1.7% and 2.8% than those of 65.8mm. The volumetric efficiency changed little as the size of discharge port changed, but the adiabatic efficiency increased a little as the size of discharge port decreased.

흡수성능에 미치는 수직 액막 파동의 영향에 관한 연구 (Effect of Wavy Flow of Vertical Falling Film on the Absorption Performance)

  • 김정국;조금남
    • 설비공학논문집
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    • 제16권2호
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    • pp.194-201
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    • 2004
  • In the present study, the improvement of absorption characteristics on combined heat and mass transfer process in a falling film of a vertical absorber by change of geometric parameters were studied experimentally and analytically. The energy and diffusion equations are solved simultaneously to give the temperature and concentration variations at the liquid solution-refrigerant vapor interface and at the wall. Absorption behaviors of heat and mass transfer were analyzed through falling film of the LiBr aqueous solution contacted by refrigerant vapor in the absorber. Effects of film Reynolds number, geometric parameters by insert device (spring) and flow pattern on heat and mass transfer performances have been also investigated. Especially, effects of the flow pattern by geometric parameters have been considered to observe the total heat and mass transfer rates through falling film along the absorber. As a numerical and experimental result, maximum absorption rate was shown at the wave-flow by insert device (spring). The error ranges between experiment and analysis were from 5.8 to 12% at Re$_{f}$ > 100.0.