• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2000년도 제 25회 정기총회 및 추계학술발표회
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• pp.51-58
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• 2000

The purpose of this study is the optimum modification of dynamic characteristics of stiffened plate structure. In the method of the optimization ,finite element method (FEM), sensitivity analysis and optimum structural modification method are used. To begin with, using FEM, the dynamic characteristics of stiffened plate structure is analyzed. Next, rate of change of dynamic characteristic by the change of design variable is calculated using the sensitivity analysis. Then, amount of change of design variable is calculated using this sensitivity value and optimum structural modification method. The change of natural frequency is made to be an objective function. Thickness of plate and cross section moment become a design variable. It is shown that the results are effective in the optimum modification for dynamic characteristics of the stiffened plate structure.

• Tribology and Lubricants
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• 제11권2호
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• pp.44-55
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• 1995

Frictional characteristics with the change of dynamic parameters, such as stiffness, inertia and damping, in the friction measurement at dry sliding surfaces were experimentally and theoretically investigated throughout the study. Dynamic frictional force and the variation in the normal load were mainly measured at the various conditions of system dynamic parameters with which stiffness in the normal direction, loading mechanisms and test materials were varied. For the normal load, mechanisms using both a dead weight and a pneumatic cylinder were applied, which resulted in change of the inertia and damping of the test rig. Test materials were steel, rosin and PTFE, which have different types of intrinsic frictional characteristics. Test results showed that frictional characteristics under different dynamic parameters could be different even though the operating variables were the same and also they could result in the variation in the normal load, which could consequently affect the wear mechanism.

• 대한임상전기생리학회지
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• 제10권1호
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• pp.39-44
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• 2012

Purpose : This study purposed to analyze how dynamic stabilization exercise on an unstable surface, and static stabilization exercise on muscle strength and endurance. Methods : For this study we sampled 9 people for the unstable surface dynamic stabilization exercise group, 9 for the stable surface static stabilization exercise group, and 9 for the control group. In order to examine muscle strength and endurance, we measured changes in the maximal voluntary isometric contraction (MVIC) using a dynamometer before, 3 weeks after, and 6 weeks after the experiment. Results : First, with regard to change in muscle strength, flexion strength showed a significant change in interaction by time (p<0.05). Extension strength showed a significant change in interaction by time (p<0.05). Second, with regard to change in endurance, flexion endurance showed a significant change in interaction by time (p<0.05). Extension endurance showed a significant change in interaction by time (p<0.05). Conclusion : In conclusion, this study confirmed significant changes in interaction between the groups and by time with regard to changes in muscle strength and endurance. These results suggest the potential of surface dynamic stabilization exercise as a clinical intervention.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1996년도 가을 학술발표회 논문집
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• pp.131-137
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• 1996

To perform condition monitoring of P.C. Box girder bridge under ambient traffic, dynamic characteristics were identified using the results of load test an analysis. It was found that natural frequencies obtained from the measured acceleration data for the forced vibration part and free vibration part were nearly identical. Thus it can be concluded that dynamic parameters are properly determined under ambient traffic condition. Finite element model for analysis was calibrated using measured frequencies. Change of dynamic characteristics were predicted through analysis of the established finite element model with anticipated change.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권12호
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• pp.653-660
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• 2006

In this paper, dynamic simulation results for modules of a magnetically-levitated(Maglev) vehicle are presented. The mathematical dynamic models for the Maglev vehicle are firstly derived. The Maglev system consists of one vehicle, two half-bogies, one guideway, four secondary suspensions, eight electromagnets and levitation control systems. Also, the dynamic characteristics are analysed by using the derived models. Finally, two simulations such as reference airgap step change of 1mm and rail step change of 1mm, are carried out. The dynamic simulation results are shown to testify the developed dynamic simulation program. From the results, we can see the possibility of the dynamic simulation program to develop a new Maglev vehicle system.

• 대한인간공학회:학술대회논문집
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• 대한인간공학회 1998년도 춘계학술대회논문집
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• pp.194-199
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• 1998

The purpose of this study is conducted to evaluate the psycho-physiological effects of the dynamic lighting on VDT workers and to establish the dynamic lighting design guides. The main experimental factors are changes of illuminance. There were five conditions including 1) ripid change, 2) slow change at 300lx .approx. 500lx, 3) a static illuminance level at 300lx, and 4) rapid chante, 5) slow change at 200lx .approx. 300lx. The ranges of change were set typical illuminance level for the simple visual task requirement and reasonable to a VDT task ; 200-300-500lx. The psycho-physiological measurements used were EEG, R-R interval, CFF, near point accommodation, feeling perceived fatigue, and work performance. Analysis of psycho-physiological factors shows that higher illumination level conditions are more affirmative effects than lower on VDT workers under 500lx except for the results of feeling perceived fatigue. And about the speed of changes of illuminance level. The conditions of slow change were better than the others in terms of the work performance as well as psycho-physiological results.

• 정보화연구
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• 제10권3호
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• pp.295-303
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• 2013

This paper presents a new approach to managing dynamic business process changes based on business process change patterns. We identify and categorize business process change patterns that occur recurrently in a dynamic business environment. Several issues regarding management of process versions are discussed, and a pattern-based version management method for handling process changes more flexibly is explained in detail. We propose a mechanism for abstract process execution with runtime encapsulation of a business process, which can maximize the flexibility of process execution using multiple process versions. In addition, we propose a concept of process promotion and demotion that can dynamically choose an actual version of the process at run-time. With our pattern-based process change management and versioning approach, it is expected that the flexibility and efficiency of BPM systems can be enhanced significantly.

• 한국항해학회지
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• 제25권1호
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• pp.45-52
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• 2001

본 논문은 선체구조에 많이 이용되고 있는 보강판 구조물의 동적 특성을 최적 변경하는데 그 목적이 있다. 유한요소법(FEM), 동적 감도해석법, 최적구조 변경법을 이용하여 보강판의 동적 특성을 최적화한다. 먼저, FEM을 이용하여 보강판 구조물의 동적 특성을 해석한다. 다음으로 설계변수의 변화에 따른 동적 특성의 변화율을 동적 감도해석법으로 해석한다. 감도해석법으로 구한 감도값과 최적구조 변경법을 이용하여 설계변수들의 변경 량을 계산한다. 보강판 구조물의 고유진동수의 변경을 목적함수로 하고, 보강판의 두께와 보강재의 단면2차 모우멘트를 설계 변수로 한다. 본 논문에서 이용한 최적구조 변경법이 보강판 구조물의 동특성을 최적화하는데 유용함을 보여준다.

• Communications for Statistical Applications and Methods
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• 제30권4호
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• pp.369-388
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• 2023

In this paper, we develop the two-step procedure that detects and estimates the position of structural changes for multivariate nonstationary time series, either on mean parameters or second-order structures. We first investigate the presence of mean structural change by monitoring data through the aggregated cumulative sum (CUSUM) type statistic, a sequential procedure identifying the likely position of the change point on its trend. If no mean change point is detected, the proposed method proceeds to scan the second-order structural change by modeling the multivariate nonstationary time series with a multivariate locally stationary Wavelet process, allowing the time-localized auto-correlation and cross-dependence. Under this framework, the estimated dynamic spectral matrices derived from the local wavelet periodogram capture the time-evolving scale-specific auto- and cross-dependence features of data. We then monitor the change point from the lower-dimensional approximated space of the spectral matrices over time by applying the dynamic principal component analysis. Different from existing methods requiring prior information on the type of changes between mean and covariance structures as an input for the implementation, the proposed algorithm provides the output indicating the type of change and the estimated location of its occurrence. The performance of the proposed method is demonstrated in simulations and the analysis of two real finance datasets.

• 한국도로학회논문집
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• 제15권3호
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• pp.65-74
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• 2013

PURPOSES: This study is to evaluate the dynamic modulus changes of permeable asphalt mixtures by using non-destructive impact testing method and to compare the dynamic moduli of permeable asphalt mixtures through repeated freezing and thawing conditions. METHODS: For the study, non-destructive impact testing method is used in order to obtain dynamic modulus of asphalt specimen and to confirm the change of dynamic modulus before and after freezing and thawing conditions. RESULTS : This study has shown that the dynamic moduli of asphalt concrete specimens consisting of 10%, 15% and 20% porosity are reduced by 11.851%, 1.9564%, 24.593% after freezing and thawing cycles. CONCLUSIONS : Non-destructive impact testing method is very useful and has repeatability. Specimen with 15% porosity has high durability than others.