• Title/Summary/Keyword: Misalignment

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Star-gas misalignment in galaxies: I. the properties of galaxies from the Horizon-AGN simulation and comparisons to SAMI

  • Khim, Donghyeon J.;Yi, Sukyoung K.
    • The Bulletin of The Korean Astronomical Society
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    • v.45 no.1
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    • pp.38.1-38.1
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    • 2020
  • Recent integral field spectroscopy observations have found that about 11% of galaxies show star-gas misalignment. The misalignment possibly results from external effects such as gas accretion, interaction with other objects, and other environmental effects, hence providing clues to these effects. We explore the properties of misaligned galaxies using Horizon-AGN, a large-volume cosmological simulation, and compare the result with the result of the Sydney-AAO Multi-object integral field spectrograph (SAMI) Galaxy Survey. Horizon-AGN can match the overall misalignment fraction and reproduces the distribution of misalignment angles found by observations surprisingly closely. The misalignment fraction is found to be highly correlated with galaxy morphology both in observations and in the simulation: early-type galaxies are substantially more frequently misaligned than late-type galaxies. The gas fraction is another important factor associated with misalignment in the sense that misalignment increases with decreasing gas fraction. However, there is a significant discrepancy between the SAMI and Horizon-AGN data in the misalignment fraction for the galaxies in dense (cluster) environments. We discuss possible origins of misalignment and disagreement. This presentation is mainly based on the published work Khim et al. 2020, ApJ, 894, 106 (17pp).

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Calculation of Unbalanced Magnetic Pull of Induction Motors due to Rotor Misalignment (경사 편심에 의한 유도전동기의 자기흡인력 평가)

  • Kim, S.H.;Yang, B.S.;Kim, H.C.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2006.05a
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    • pp.1321-1327
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    • 2006
  • This paper presents the calculation of unbalanced magnetic pull (UMP) that causes rotor misalignment in induction motor. The excessive noise and vibration will be occurred by means of rotor misalignment. Angular misalignment of rotor will produce air-gap permeance wave which is function of axial and circumferential coordinate. In this paper, the UMP is calculated using permeance and magneto motive force (MMF) in the case of static and dynamic misalignment. Based on the percentage of misalignment, the result shows that the UMP and magnetic pressure are increased according to the increasing of misalignment. The UMP is occurred not only in It frequency component but also the others.

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Fatigue Life Analysis for Angular Contact Ball Bearing with Angular Misalignment (각 어긋남을 고려한 각접촉 볼베어링의 피로수명 해석)

  • Bae, Gyu-Hyun;Tong, Van-Canh;Hong, Seong-Wook
    • Journal of the Korean Society for Precision Engineering
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    • v.33 no.1
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    • pp.53-61
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    • 2016
  • Angular misalignment has a significant effect on the characteristics of angular contact ball bearings (ACBBs). This paper presents an analysis of fatigue life for ACBBs subjected to angular misalignment. A simulation model is developed with de Mul's bearing model and the ISO basic reference rating life model. Simulation is performed to calculate the life of the ACBBs subjected to angular misalignment. The numerical results show that angular misalignment influences the load distribution significantly, thus reducing the bearing rating life. The fatigue life of ACBBs is decreased by angular misalignment regardless of axial preload, external radial load and rotational speed. The results show that angular misalignment should be maintained at less than 1mrad for ACBBs.

Star-Gas Misalignment in Galaxies: II. Origins Found from the Horizon-AGN Simulation

  • Khim, Donghyeon J.;Yi, Sukyoung K.
    • The Bulletin of The Korean Astronomical Society
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    • v.46 no.1
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    • pp.29.1-29.1
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    • 2021
  • There have been many studies aiming to reveal the origins of the star-gas misalignment found in galaxies, but there still is a lack of understanding of the contribution from each formation channel candidate. We explore the properties, origins, and lifetimes of the star-gas misalignment using Horizon-AGN, a large-volume cosmological simulation. First, the misalignment fraction shows a strong anti-correlation with the kinematic morphology (V/sigma) and the cold gas fraction of the galaxy. This result is consistent with the result of integral field spectroscopy observations. Second, we have identified four main formation channels of misalignment and quantified their level of contribution: mergers (35%), interaction with nearby galaxies (23%), interaction with dense environments or their central galaxies (21%), and secular evolution including smooth accretion from neighboring filaments (21%). Third, the decay timescale of the misalignment is strongly linked with the kinematic morphology of the galaxy: early-type galaxies (2.28 Gyr) tend to have a longer misalignment lifetime than LTGs (0.49 Gyr). We also found that the morphology and cold gas fraction are both and independently anti-correlated with the misalignment lifetime.

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Numerical Analysis of Misaligned Finite Line Contacts EHL Problem (Misalignment가 있는 유한한 선접촉 EHL 문제의 수치해석)

  • Park, Tae-Jo
    • Tribology and Lubricants
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    • v.26 no.5
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    • pp.263-271
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    • 2010
  • The rollers of cylindrical roller bearing are axially profiled to relieve high edge stress concentration caused by mainly their finite length and by misalignment. In this paper, a numerical analysis is carried to study the EHL of misaligned (tilted) rollers with axially profiled ends. Using a finite difference method with non-uniform grids and the Newton-Raphson method, the highly nonlinear EHL problems are systematically solved. Physically consistent solutions are obtained for moderate load, material parameters and very small misalignment. For different misalignment angles, contours and sectional plots of pressure and film shape near both edge regions are compared. The asymmetric pressure distributions and film shapes show that the EHL results of finite line contacts are highly dependent upon very small amounts of roller misalignment. Especially, the effect of misalignment on the EHL pressure distribution is much higher than the film shapes.

A Study on Development the Dynamic Model to Misaligned Gear Coupling (I) - The Focus on Development of Dynamic Model to n Gear Coupling (정렬불량을 가진 기어 커플링의 동역학적 모델 개발에 관한 연구 (I) - 기어 커플링의 동적모델 구축을 중심으로-)

  • Kim, Byung-Ok;Kim, Yong-Chul
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.6
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    • pp.857-863
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    • 2003
  • In rotating machinery, unbalance and misalignment are major concerns in vibration. Unbalance can be eliminated by balancing procedure to some degree. but little work has been done on the vibrations that occur in a misaligned rotor system. Currently, no generalized theoretical model based on a rotor system with flexible coupling is available to describe the vibrations caused by misalignment. As a part of systematic investigation on the misalignment, first of all, the study on flexible coupling with misalignment should be preceded. In this study, the geometry and reaction force and moment of a gear coupling with misalignment was investigated, also the theoretical model of a gear coupling with misalignment was presented by using the relationship between geometry and moment of gear coupling. It is expected that the proposed procedure can be applied to derive the theoretical model of other couplings.

Dynamic Analysis of Spindle with Angular Contact Ball Bearings Subjected to Angular Misalignment (각접촉 볼베어링으로 지지된 스핀들의 정렬오차에 의한 동특성 변화 해석)

  • Bae, Gyu-Hyun;Hong, Seong-Wook;Yoon, Young-Seok
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.23 no.4
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    • pp.368-373
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    • 2014
  • This paper presents the dynamic modeling and analysis results for a spindle supported by angular contact ball bearings (ACBBs) subjected to angular misalignment. Although ACBBs are widely used in spindle systems, their characteristics in regard to angular misalignment have rarely been investigated. A simulation program was developed to calculate the dynamic characteristics of a simple spindle model that is supported by angular contact ball bearings subjected to angular misalignment. Angular misalignment is shown to introduce anisotropy into the angular contact ball bearings and then split the natural frequencies in spindles. Simulations were also performed to show the possibility of evaluating bearing misalignment using natural frequency measurements.

Nonlinear Analysis of Gear Driving System due to Misalignment (정렬불량에 의한 기어구동계 비선형 해석)

  • Lee, B. H.;Park, Y. S.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.11a
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    • pp.311.2-311
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    • 2002
  • Even through the problem of misalignment is of great importance, not much work has been reported in the literature on the effect of misalignment on the vibrations of the gear-bearing systems. Therefore, the nonlinear dynamic characteristics of the gear driving system due to misalignment are investigated in this work. Transmission error for helical gear and bearing nonlinear stiffness is calculated. (omitted)

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Prediction of the Fatigue Life of Deep Groove Ball Bearing under Radial and Moment Loads -Equivalent Dynamic Loads- (반경방향과 모멘트하중 하에서의 깊은홈 볼베어링의 피로수명 평가 -동등가하중식 제안-)

  • 김완두;한동철
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.7
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    • pp.1654-1663
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    • 1994
  • Even if the ball bearing was conservatively designed considering the dynamic capacity and the rating life, sometimes the bearing was early failed on account of the misalignment and the lubricant contaminations etc. Misalignment was generated when bearing-shaft system transmitted large power and when the bearing was inadequately mounted. It was possible to predict the fatigue life of ball bearing under the misalignment considering the motions of ball, cage and raceway, and the factors of the effect on fatigue life. Misalignment affected on ball bearing as radial and moment load and the relationships between misalignment and moment were obtained. In this paper, the analysis of the load distributions between ball and raceway, and the prediction of fatigue life of deep groove ball bearing under radial and moment loads were carried out. And, the new formulation of equivalent dynamic load considering the effects of moment load was proposed.

A Misalignment Compensation Algorithm for Flexible Parts Assembly (유연 부품 조립을 위한 횡방향 오차의 보정 알고리즘)

  • 김진영;조형석
    • Journal of Institute of Control, Robotics and Systems
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    • v.5 no.7
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    • pp.841-847
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    • 1999
  • For successful assembly of flexible parts, informations about their deformation as well as possible misalignments between the holes and their mating parts are essential. Such informations can be acquired from visual sensors. For robotic assembly, the corrective assembly motion to compensate for such misalignments has to be determined from the measured informations. However, this may not be simply derived from the measured misalignment alone because the part deformation progressively occurs during misalignment compensation. Based on the analysis of flexible parts assembly process, this paper presents a neural net-based inference system that can infer the complex relationship between the corrective motion and the measured information of parts deformation and misalignments. And it verifies the performance of the implemented inference system. The results show that the proposed neural net-based misalignment compensation algorithm Is effective in compensating for the lateral misalignment, and that it can be extended to the assembly tasks under more general conditions.

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