• Title, Summary, Keyword: stability

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Design of a Mechanism to Increase Lateral Stability of Mobile Robot (이동로봇의 횡방향 안정성 증대를 위한 기구)

  • 정상국;최용제
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.1148-1153
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    • 2004
  • This paper presents the mechanism to increase lateral stability of a mobile robot using an energy stability margin theory. Previous measure of stability used in a wheeled mobile robot has been based on a static stability margin. However, the static stability margin is independent of the height of the robot and does not provide sufficient measure for the amount of stability when the terrain is not a horizontal plane. In this work, the energy stability margin theory, which is dependent on robot's height is used to develop a 2 dof mechanism to increase lateral stability. This proposed mechanism shifts the center of gravity of the robot to the point where the energy stability margin is maximized and overall stability of the robot equipped with this mechanism will be increased.

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The understanding of the Longitudinal Static Stability Flight Test (종축 정안정성 비행시험기법 이해)

  • Lee, Ju-Ha
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.15 no.4
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    • pp.142-147
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    • 2007
  • When the aircraft is developed, several flight tests are performed including stability and controllability, performance and systems, above all the most important part of the flight test is stability test. Stability test is divided into two parts, static stability and dynamic stability. Static stability of the aircraft is typically defined in terms of its initial tendency to return to equilibrium after a disturbance and not included time concept. One of static stability, longitudinal static stability, was addressed here. The longitudinal static stability was studied from the basic theory to the flight test method and also explained data reduction method throughout the flight test. Finally showed how to meet the specifications such as ROC, FAR and MIL-specifications.

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The Effect of Postural Stability on Genu Varum in Young Adults

  • Chae, Yun-Won;Park, Ji-Won;Park, Seol
    • The Journal of Korean Physical Therapy
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    • v.24 no.6
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    • pp.419-422
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    • 2012
  • Purpose: Malalignment of the lower limbs may increases the difficulty of maintaining equilibrium. The purpose of this study was to study the effects of genu varum and poor posture in the sagittal plane on postural stability. Methods: We had 27 subjects with varus and 27 normal subjects participate in this study. Subjects for whom the distance between the medial epicondyles in the knee joint was more than 3 cm were classified as varus group, and subjects for whom the distance was less than 3 cm were classified as normal group. The measurements of static and dynamic stability were used overall stability index (OSI), anterioposterior stability index (APSI), and mediolateral stability index (MLSI) using a Biodex balance system. Results: When measuring the static stability index, there were significant differences in the mediolateral stability index between the varus and control groups. When measuring the dynamic stability index, there were significant differences in the overall, anteriorposterior, and mediolateral stability index between the varus and control groups. These results demonstrated that genu varum affects mediolateral movement in static stability, and overall, anterioposterior and mediolateral movements in dynamic stability. Conclusion: As genu varum affects static and dynamic stability in young adults, it increases the risk of injuries or falls. Exercise and surgery are required for realigning the genu varum. Future studies about postural stability in young children and elderly people who have a risk of falls due to lower postural control ability, are needed, as well as in young adults.

Development on Evaluation Technique of Stability for Safety Elevation in Fishing(Stow-Neting)Vessel (어선(안강망) 안정성능 향상을 위한 복원성 평가기법 개발)

  • 박제웅;이희준;김주남
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.4 no.2
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    • pp.53-62
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    • 1998
  • International Maritime Organizatin(IMO) has been chosen some of agreements for regulating the international stability criteria of fishing vessels and recommended that each goverment adopts theirs into the domestic law. As a result, 77/93 Fishing Safety Agreement was ratified. Among the above agreement, contents of stability was not only applied to domestic law, but also strenghten considerably compared with existing stability criteria. And even if the calculation guide of stability with recommendations was regualted, Analysis of stability on domestic fishing vessels never have been used according to such a caculation method. Moreover, the caculation of stability criteria caused by strong wind, rolling effect and deck inflow was not considered in the existing basic design program. Therefore, the development of stability criteria program available for such a caculation has been of vital impotance. This research has developed a stability criteria program under 77/93 Fishing Safety Agreement. Also through development of stability criteria program, the stability performance of fishing vessel with 69ton stow-nesting was evaluated.

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CHARACTERIZATION OF STRICTLY OPERATOR SEMI-STABLE DISTRIBUTIONS

  • Choi, Gyeong-Suk
    • Journal of the Korean Mathematical Society
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    • v.38 no.1
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    • pp.101-123
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    • 2001
  • For a linear operator Q from R(sup)d into R(sup)d and 0$\alpha$ and parameter b on the other. characterization of strictly (Q,b)-semi-stable distributions among (Q,b)-semi-stable distributions is made. Existence of (Q,b)-semi-stable distributions which are not translation of strictly (Q,b)-semi-stable distribution is discussed.

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Characterization of Some Classes of Distributions Related to Operator Semi-stable Distributions

  • Joo, Sang Yeol;Yoo, Young Ho;Choi, Gyeong Suk
    • Communications for Statistical Applications and Methods
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    • v.10 no.1
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    • pp.177-189
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    • 2003
  • For a positive integer m, operator m-semi-stability and the strict operator m-semi-stability of probability measures on R^d$ are defined. The operator m-semi-stability is a generalization of the definition of operator semi-stability with exponent Q. Characterization of strictly operator na-semi-stable distributions among operator m-semi-stable distributions is given. Translation of strictly operator m-semi-stable distribution is discussed.

Characterization of some classes of distributions related to operator semi-stable distributions

  • Joo, Sang-Yeol;Choi, Gyeong-Suk
    • Proceedings of the Korean Statistical Society Conference
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    • pp.221-225
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    • 2002
  • For a positive integer m, operator m-semi-stability and the strict operator m-semi-stability of probability measures on $R^{d}$ are defined. The operator m-semi-stability is a generalization of the definition of operator semi- stability with exponent Q. Translation of strictly operator m-semi-stable distribution is discussed.

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LIPSCHITZ AND ASYMPTOTIC STABILITY FOR PERTURBED NONLINEAR DIFFERENTIAL SYSTEMS

  • Goo, Yoon Hoe
    • The Pure and Applied Mathematics
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    • v.21 no.1
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    • pp.11-21
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    • 2014
  • The present paper is concerned with the notions of Lipschitz and asymptotic stability for perturbed nonlinear differential system knowing the corresponding stability of nonlinear differential system. We investigate Lipschitz and asymtotic stability for perturbed nonlinear differential systems. The main tool used is integral inequalities of the Bihari-type, in special some consequences of an extension of Bihari's result to Pinto and Pachpatte, and all that sort of things.

Effects of Wire speed Fluctuation on Arc Stability in GMA Welding (GMAW에서 와이어 송급속도의 변동이 아크안정성에 미치는 영향에 관한 연구)

  • 신현욱;최용범;성원호;장희석
    • Journal of Welding and Joining
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    • v.13 no.4
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    • pp.85-102
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    • 1995
  • Weld quality of GMA welding processes is closely related to arc stability. Although many researches on arc stability have been performed, real-time estimation of arc stability has not been attempted. For instance, Mita proposed a off-line statistical method in which short circuiting and arcing time, and voltage and current wave forms were sampled to assess arc stability. But this method is not suitable to assess arc stability for GMA welder which employ inverter power source due to its controlled current and voltage wave forms. In this paper, the relationship between are stability and wire feed rate fluctuation is analyzed to propose new criterion for inverter power source. When arc voltage and arc current and arcing time are analyzed, we can assess arc stability only for short circuit transfer mode. When wire feed rate is analyzed, we can estimate arc stability udner the condition of spray transfer mode as well. Hence, the wire feed rate is chosen for monitoring process variable to cover possible metal transfer modes in GMAW. Through this research, it has been identified that arc stability in GMA welding processes is closely related to wire fed rate. When inverter power source is used, conventional statistical method of estimating arc stability, such as Mita index, is no longer valid due to its controlled voltage and current wave forms. Arc stability has been also examined in phase plane diagram.

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Development of Stability Index for Vessel Operators Support System (선박 운항자 지원 시스템용 선박 복원성능 지수 개발)

  • IM, Nam-Kyun;HWANG, SooJin;CHOE, Hun
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.24 no.1
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    • pp.1-9
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    • 2018
  • All ships should ensure stability in accordance with IMO regulations. However, GM is only used to determine ship stability because it takes a lot of time to validate all regulations. This is a problem given that the safety of vessels cannot be guaranteed, potentially leading to accidents. There is a need for a more intuitive and comprehensive method of confirming the stability of ships. This study developed a stability index that expresses ship stability in one value. An index equation is defined based on the 6 stability criteria for ships prescribed by IMO and the result of calculating the ship stability of a model ship. A stability index has been derived for each loading condition by applying the index equation to the same ship. It can clearly be seen that this stability index appropriately explains the criteria. In other words, it is possible to assess ship stability with one value and confirm whether the ship stability satisfies IMO regulations. This index will help masters and officers more easily and accurately check ship stability.