• 소성∙가공
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• 제9권3호
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• pp.293-303
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• 2000

Recent developments of Fe technology make it possible to apply CAD/CAE/CAM techniques successfully to the stamping die design among the automotive parts industries. Those successful applications are greatly attributable to the development of commercial S/W. Up to now most commercial S/W for the analysis of sheet metal forming is based on the dynamic explicit algorithm. The main characteristics of dynamic explicit algorithm is that there is no convergence problem if the time increment is taken less than the stability limit. The stability of the analysis is guaranteed in the commercial code, since the adequate time increment is computed from the so called "Courant Condition". However excess computing time is often pointed out in the dynamic explicit analysis according to the characteristics of process parameters taken. In the study, various parameters that may affect the stability and the method how to improve computational efficiency of analysis have been investigated.estigated.

• 대한기계학회논문집
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• 제19권2호
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• pp.509-518
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• 1995

A study for the flame stability and the combustion characteristics of coaxial diffusion flame was conducted. The fuel employed was natural gas. The experimental variables were rim thickness of fuel tube, blockage ratio of the outer diameter of fuel tube to the inner diameter of air tube, and momentum ratio of fuel to air. It was consequently found that the stability in the neighborhood of the fuel rim depended on the rim thickness, especially in the case of above 3 mm, and that the stable region of the flame extended remarkably due to the formation of recirculation zone above rim. The effect of the blockage ratio on the flame stability was found to be minor in the case of above 3 mm of rim thickness. Between the momentum ratio 2 and 3, the stable flame zone was widely established as well good combustion. With increasing the fuel-air momentum ratio, axial velocity, turbulence intensity, and Reynolds stress increased.

• Wind and Structures
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• 제14권3호
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• pp.209-220
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• 2011

The cable system is generally considered to be a structural solution to increase the spanning capacity of suspension bridges. In this work, based on the Runyang Bridge over the Yangtze River, three case suspension bridges with different 3D cable systems are designed, structural dynamic characteristics, the aerostatic and aerodynamic stability are investigated numerically by 3D nonlinear aerostatic and aerodynamic analysis, and the cable system favorable to improve the wind-induced instability of long-span suspension bridges is also proposed. The results show that as compared to the example bridge with parallel cable system, the suspension bridge with inward-inclined cable system has greater lateral bending and tensional frequencies, and also better aerodynamic stability; as for the suspension bridge with outward-inclined cable system, it has less lateral bending and tensional frequencies, and but better aerostatic stability; however the suspension bridge is more prone to aerodynamic instability, and therefore considering the whole wind-induced instability, the parallel and inward-inclined cable systems are both favorable for long-span suspension bridges.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.394-399
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• 2012

This paper describes a stability and dynamic characteristics of bearingless helicopter main rotor in hover. Baseline rotor configuration is defined and modal analysis for the configuration is taken to verify the dynamic characteristics. The kinematic pitch-lag couplings through ways of pitch link installation are analyzed to know effects on loads, frequencies and stability. The effects of pitch link attachments in spanwise direction and chordwise direction as well as pitch link inclination on thrust, power, flpa-lag-pitch mode frequencies and inplane damping are examined. Pitch link at trailing edge location in chordwise direction has influence on aeroelastic stability of the rotor. Also, the pitch link with negative inclination angle makes inplane damping increase.

• Structural Engineering and Mechanics
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• 제44권3호
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• pp.305-323
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• 2012

Structural defects such as cracks are the source of local flexibilities and cause deficiencies in structural resistance. In the engineering constructions, structural elements sometimes are subjected to axial loading. Therefore, besides crack ratios and locations, influence of applied load on the stability and dynamical characteristics should also be explored. This study offers a numerical technique for the vibration and stability analysis of axially loaded cracked beams. The model merges finite element and component mode synthesis methods. Initially, stability analysis is completed and then dynamical characteristics of beams are found. Very good conformities between outcomes of the current study and those in literature, give the confidence that proposed method is reliable and effective.

• 대한전기학회논문지
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• 제41권8호
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• pp.841-849
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• 1992

In power system operation, the stability of synchronous machine has been recognized one of the most important things. AESOPS program developed by EPRI in U.S.A. is a frequency domain analysis program in power system stability and it computes the electro-mechanical oscillation mode. This paper presents how to analyze the power system small signal stability problem efficiently by uusing the AESOPS program and analyze the various factors affecting the damping characteristics of these oscillations in KEPCO power system of 1986 with pumped-storage plant. To reduce the computing time and efforts, selecting the poorly-damped oscillation mode and clustering technique have been used. The characteristics of load, the amount of power flow on the transmission line and the gain of exciter have a significant effects on the damping of the system while the governing system has only a minor one. With the Power System Stabilizers, the stability of the power system has been improved.

• Wind and Structures
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• 제21권4호
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• pp.407-424
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• 2015

To explore the favorable structural system of cable-stayed bridges with ultra-kilometer main span, based on a fully self-anchored cable-stayed bridge with 1400 m main span, a partially earth-anchored cable-stayed bridge scheme with the same main span is designed. Numerical investigation on the dynamic characteristics, aerostatic and aerodynamic stability of both two bridge schemes is conducted, and the results are compared to those of a suspension bridge with similar main span, and considering from the aspect of wind stability, the feasibility of using partially earth-anchored cable-stayed bridge in super long-span bridges with ultra-kilometer main span is discussed. Moreover, the effects of structural design parameters including the length of earth-anchored girder, the number of auxiliary piers in side span, the height and width of girder, the tower height etc on the dynamic characteristics, aerostatic and aerodynamic stability of a partially earth-anchored cable-stayed bridge are analyzed, and their reasonable values are proposed. The results show that as compared to fully self-anchored cable-stayed bridge and suspension bridge with similar main span, the partially earth-anchored cable-stayed bridge has greater structural stiffness and better aerostatic and aerodynamic stability, and consequently becomes a favorable structural system for super long-span bridges with ultra-kilometer main span. The partially earth-anchored cable-stayed bridge can achieve greater stiffness and better wind stability under the cases of increasing the earth-anchored girder length, increasing the height and width of girder, setting several auxiliary piers in side span and increasing the tower height.

• 문화기술의 융합
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• 제7권1호
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• pp.406-415
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• 2021

본 연구는 조직문화 특성이 종업원의 혁신행동에 어떠한 영향을 미치는가를 고찰하기 위해 연구모형을 설정하고 분석하였다. 본 연구는 조직문화 특성을 하위 요인으로 발전성, 안정성, 합리성으로 나누어 각각 혁신행동과의 관계에 관한 연구를 진행하였다. 본 연구는 또한 창의적 효능감이 조직문화 특성과 혁신행동 간의 매개를 하는지에 대해 확인하고자 하였다. 이를 위해 자료 수집은 기업에 재직 중인 조직구성원 80명을 대상으로 하였고 수집 자료 분석을 위해서 SPSS와 PLS 프로그램을 사용하여 분석하였다. 가설검증 결과, 조직문화 특성 중 안정성만이 혁신행동에 직접적 영향을 유의하게 미쳤다. 이러한 결과는 조직문화 특성과 종업원의 혁신행동 간의 연구에서 의미 있는 결과로 해석할 수 있다. 또한, 창의적 효능감은 조직 문화 특성 (발전성, 안정성, 합리성)이 종업원의 혁신행동에 미치는 영향을 유의하게 매개하는 것으로 확인되었다. 이러한 결과는 기업이 종업원이 지각하는 조직 내부 안정성 측면의 조직문화를 형성하는데 역점을 두고 종업원의 혁신행동을 이끌어 조직성과 창출을 해야함을 시사한다. 또한, 기업은 조직문화 특성 (발전성, 안정성, 합리성)이 종업원의 창의적 효능감을 높여 종업원의 혁신행동으로 이어지도록 조직 문화를 조성해야 할 것이다.

• 한국정밀공학회지
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• 제18권8호
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• pp.116-121
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• 2001

The paper presents the dynamic characteristics of a rotor-bearing system supported by an actively controlled hydrodynamic journal bearing. The proportional. derivative and integral controls are adopted for the control algorithm to control the hydrodynamic journal bearing with an axial groove. Also, the cavitation algorithm implementing the Jakobsson-Floberg-Olsson boundary condition is adopted to predict cavitation regions in the fluid film more accurately than conventional analysis, which uses the Reynolds condition. The speed at onset of instability of a rotor-bearing system is increased by both proportional and derivative control of the bearing. The proportional control increases the stability threshold without affecting the whirl ratio. However, for the derivative control of the bearing, increase of stability threshold speed is accompanied by a parallel reduction of the whirl ratio. The integral control has no effect on stability characteristics of hydrodynamic journal bearing. The PD-control is more effective than proportional or derivative control. Results 7how the active control of bearing can be adopted for the stability improvement of a rotor-bearing system.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1999년도 제29회 춘계학술대회
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• pp.92-100
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• 1999

Friction characteristics of automotive friction materials according to the types of phenolic resin were investigated by using a pad-on-disk type friction tester. Four different simplified friction materials bound with Bakelite$^{TM}$ and Xylok$^{TM}$ phenolic resin were studied in this work. Two different modes of drag test(constant initial temperature test and constant interval test) were employed to analyze the effects of the binders on friction characteristics. Friction materials containing modified Xylok$^{TM}$ resin showed good heat resistance and friction stability. The results also showed that aramid fiber played important roles in improving friction stability and weard wear