• Title, Summary, Keyword: stability

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On asymptotic Stability in nonlinear differential system

  • An, Jeong-Hyang
    • Journal of the Korea Industrial Information Systems Research
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    • v.11 no.5
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    • pp.62-66
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    • 2006
  • We investigate various $\Phi(t)-stability$ of comparison differential equations and we abtain necessary and/or sufficient conditions for the uniform asymptotic and exponential asymptotic stability of the nonlinear differential equation x'=f(t, x).

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Ship Stability Calculation for Cause Analysis of No. 501 Oryong Sinking Accident

  • Lee, Sang-Gab;Lee, Jae-Seok;Ki, Jee-Hun
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • pp.248-255
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    • 2018
  • Deep-sea fishing vessel No. 501 Oryong was fully flooded through the openings and was sunk down to the bottom of sea due to the very rough sea weather on the way of evasion after fishing operation in the Bearing Sea with many crews dead and/or missed. In this study, calculation of ship stability was carried out using KST-SHIP(ship calculation system of KST), considering the effect of flow fluid and fish catch arrangement according to the progress of its sinking accident, and damage stability was analyzed. For this study, intact stability calculation of its accident ship under the full load departure condition and its calculation result were verified by comparing with each other, and intact stability according to displacement from the departure of accident ship just before the accident was calculated and analyzed. Damage stability was calculated according to the progress during sinking accident and also analyzed.

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The Effects of Gluteus Medius Strength Training on Ankle Stability in Patient with Chronic Ankle Sprains (중간볼기근 강화운동이 만성 발목염좌 환자의 발목 안정성에 미치는 효과)

  • Kim, Yoon-hwan;Park, Su-hyung;Song, Hyun-seung
    • The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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    • v.24 no.2
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    • pp.59-67
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    • 2018
  • Background: The purpose of this study was to investigate the effects of gluteus medius strength exercise on the ankle stability of high school student with chronic ankle sprains. Methods: A total of 30 participants were divided two groups. Experimental group was 15 participants applied gluteus medius strength exercise. Control group was 15 participants performing ankle strength exercise. This study was performed for 50 minutes per day, three a week for 6 weeks. All measurements were taken to a pre and post test. Strength was measured using Power Track ll. Balance was measured using Biodex balance system for Limits of Stability and Postural Stability. Ankle Stability was measured using Cumberland Ankle Instability Tool (CAIT). Results: In the case of gluteus medius strength, there were statistically significant differences between the experimental group and the control group. For ankle stability were statistically significant differences within the experimental group according to measurements taken by Limits of Stability, Postural Stability, and CAIT. A between group comparison showed a statistically significant difference for CAIT only. Conclusion: According to our measurements it appears that gluteus medius strength training was effective in benefiting muscular strength, balance and ankle stability among the physical education.

Stochastic Stability Analysis of the Power System Incorporating Wind Power using Measurement Wind Data

  • Parinya, Panom;Sangswang, Anawach;Kirtikara, Krissanapong;Chenvidhya, Dhirayut
    • Journal of Electrical Engineering and Technology
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    • v.13 no.3
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    • pp.1110-1122
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    • 2018
  • This paper proposes an alternative method to evaluate the effect of wind power to the power system stability with small disturbance. Alternatively, available techniques for stability analysis of a power system based on deterministic methods are less accurate for high penetration of wind power. Numerical simulations of random behaviors are computationally expensive. A stochastic stability index (SSI) is proposed for the power system stability evaluation based on the theory of stochastic stability and energy function, specifically the stochastic derivative of the relative well-defined energy function and the critical energy. The SSI is implemented on the modified nine-bus system including wind turbines under different conditions. A doubly-fed induction generator (DFIG) wind turbine is characterized and modeled using measured wind data from several sites in Thailand. Each of the obtained wind power data is analyzed. The wind power effect is modeled considering the aggregated effect of wind turbines. With the proposed method, the system behavior is properly predicted and the stability is quantitatively evaluated with less computational effort compared with conventional numerical simulation methods.

Characteristics of the Marriage and Marital Stability among Elderly Couples (노년기 부부의 결혼특성요인과 결혼안정성)

  • 김태현;전길양
    • Journal of Korean Home Management Association
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    • v.20 no.4
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    • pp.197-206
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    • 2002
  • The purpose of this study was to examine the effect of marital characteristics on the marital stability among the elderly couples. Each participant was measured using a scale for the concept of marriage, a scale for marital coherence, a marital stress scale, a coping behavior scale and a marital stability scale. Elderly people who have a living spouse and who are living In Seoul were recruited. The data from two hundred and forty participants over 60-years-old were used in the final analyses. Major findings are as follows First, demographic factors such as educational level, health, economic status, the main source of income, and employment status appeared to significantly predict the elderly folks'marital stability Second, gender seems to be a factor In elderly couples'experience of marital stability. Husbands perceived marital stability to be higher than wives did. Third, the perception of marital stress, positive coping behavior and marital coherence influence the marital stability of the elderly couples. That is, the less elderly couples perceived marital stress and the less they relied on negative coping behaviors, the higher they perceived marital stability. These results imply that a healthful coping behavior to marital stress is important in enhancing marital stability for elderly couples.

A Study on the Interactive Grain Stability Calculation (대화형 Grain Stability Calculation에 관한 연구)

  • Lee, S.S.;Lee, K.O.;Kang, W.S.;Yoon, M.T.;Sung, D.K.;Lee, J.C.
    • Journal of the Society of Naval Architects of Korea
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    • v.34 no.1
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    • pp.102-110
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    • 1997
  • In a shipyard, computer calculation is not frequently used for the grain stability calculation because of large difference between calculation values and real values. Therefore, the necessary calculation process for grain stability is done manually. GUI(Graphical User Interface) is adopted for the convenience of users and interactive data I/O. The hold shape (girder, hold, etc.)needed for calculation are visualized using GLBAX which is a 3 dimensional graphic library. The interface with the ship basic calculation package is also implemented. The aim of this paper is to develop a reliable interactive grain stability calculation program which reduces computational time, and is to computerize the grain stability calculation procedure.

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An Investigation of the Lateral Stability Criteria for Integrated Chassis Control (통합 샤시 제어를 위한 횡방향 안전성 판단 조건에 관한 연구)

  • Ann, Kookjin;Joa, Eunhyek;Koh, Youngil;Yi, Kyongsu;Sohn, Kimo
    • Journal of Auto-vehicle Safety Association
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    • v.9 no.2
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    • pp.26-32
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    • 2017
  • This paper presents the lateral stability criteria for integrated chassis control. To determine the intervention timing of chassis control system, the lateral stability criteria is needed. The proposed lateral stability criteria is based on velocity-yawrate gain domain to determine whether vehicle is stable. If the yawrate gain violates the proposed criteria, the stability of the vehicle is considered as unstable. Characteristic velocity and critical velocity are employed to distinguish lateral stability criteria. The inside of the two boundaries is stable and the outside is unstable. If yawrate gain of vehicle violates the lateral stability criteria, the chassis control begin to intervene. To validate the lateral stability criteria, both computer simulations and vehicle test are conducted with respect to circular turn scenario. The proposed lateral stability criteria makes it possible to reduce intervention of chassis control system.

Assessment of Total Transfer Capability Using IPLAN: An Application of UPFC for Total Transfer Capability Enhancement

  • Lee Byung Ha;Kim Jung-Hoon;Kwak No-Hong;Lee Woon-Hee
    • KIEE International Transactions on Power Engineering
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    • v.5A no.3
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    • pp.244-251
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    • 2005
  • Power transfer capability has been recently highlighted as a key issue in many utilities. It is determined by the thermal stability, dynamic stability and voltage stability limits of generation and transmission systems. In particular, voltage stability affects power transfer capability to a great extent in many power systems. This paper presents a tool for determining total transfer capability from a static voltage stability viewpoint using IPLAN, which is a high level language used with the PSS/E program. The tool was developed so as to analyze static voltage stability and to determine the total transfer capability between different areas from a static voltage stability viewpoint by tracing stationary behaviors of power systems. A unified power flow controller (UPFC) is applied for enhancing total transfer capability between different areas from the viewpoint of static voltage stability. Evaluation of the total transfer capability of a practical KEPCO power system is performed from the point of view of static voltage stability, and the effect of enhancing the total transfer capability by UPFC is analyzed.

Effect of coarse aggregates and sand contents on workability and static stability of self-compacting concrete

  • Mohamed, Sahraoui;Taye, Bouziani
    • Advances in concrete construction
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    • v.7 no.2
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    • pp.97-105
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    • 2019
  • In this paper, the workability and static stability were evaluated using a proposed test method. Workability and static stability represent a key property of self-compacting concrete (SCC) in fresh state. A number of standardized test methods were developed to assess these properties. However, no accelerated test method reliably predicts both workability and static stability of SCC. In the present work, a modified K-slump test method was developed to evaluate workability and static stability of SCC. In order to take implicit mixture variations of SCC constituents that can affect fresh SCC properties, a central composite design was adopted to highlight the effect of gravel to sand ratio (G/S), gravel 3/8 to gravel 8/15 ratio (G1/G2), water to cement ratio (W/C), marble powder to cement ratio (MP/C) and superplasticizer content (SP) on workability measured with slump and flow time (T50) tests and static stability measured with sieve stability test (Pi), segregation test index (SSI), Penetration test (Pd) and the proposed K-slump test (Km). The obtained results show that G/S ratio close to 1 and G1/G2 ratio close to 60% can be considered as optimal values to achieve a good workability while ensuring a sufficient static stability of SCC. Acceptable relationships were obtained between Slump flow, Pi, Pd and Km. Results show that the proposed K-slump test allow to assess both workability and static stability of fresh SCC mixtures.