• Structural Engineering and Mechanics
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• v.13 no.5
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• pp.569-589
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• 2002

In performing the dynamic analysis, the step size used in a step-by-step integration method might be much smaller than that required by the accuracy consideration in order to capture the rapid chances of dynamic loading or to eliminate the linearization errors. It was first found by Chen and Robinson that these difficulties might be overcome by integrating the equations of motion with respect to time once. A further study of this technique is conducted herein. This include the theoretical evaluation and comparison of the capability to capture the rapid changes of dynamic loading if using the constant average acceleration method and its integral form and the exploration of the superiority of the time integration to reduce the linearization error. In addition, its advantage in the solution of the impact problems or the wave propagation problems is also numerically demonstrated. It seems that this time integration technique can be applicable to all the currently available direct integration methods.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10b
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• pp.370-375
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• 1992

An algorithm for the notion planning of the robotic hand is proposed to generate finite displacements and changes in orientation of objects by considering sliding effects between the fingertips and the object at contact points. Specifically, an optimization problem is firstly solved to find minimum contact forces and minimum joint velocities to impart a desired motion to the object at each time step. Then the instantaneous relative velocity at the contact point is found by determining velocities of the fingertip and the velocity of the object at the contact point. Finally time derivatives of the surface variables and contact angle of the fingertip and the object at the present time step is computed using the Montana's contact equation to find the contact parameters of the fingertip and the object at the next time step. To show the validity of the proposed algorithm, a numerical example is illustrated by employing the robotic hand manipulating a sphere with three fingers each of which has four joints.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.1
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• pp.37-43
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• 2014

The extended framework of Hamilton's principle provides a new rigorous weak variational formalism for a broad range of initial boundary value problems in mathematical physics and mechanics in terms of mixed formulation. Based upon such framework, a new variational numerical method of linear elasticity is provided for the classical single-degree-of-freedom dynamical systems. For the undamped system, the algorithm is symplectic with respect to the time step. For the damped system, it is shown to be accurate with good convergence characteristics.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.4C
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• pp.305-311
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• 2008

In this paper, we proposed an algorithm for adaptive noise cancellation (ANC) using the variable step size normalized least mean square (VSSNLMS) in real-time automobile environment. As a basic algorithm for ANC, the LMS algorithm has been used for its simplicity. However, the LMS algorithm has problems of both convergence speed and estimation accuracy in real-time environment. In order to solve these problems, the VSSLMS algorithm for ANC is considered in nonstationary environment. By computer simulation using real-time data acquisition system(USB 6009), VSSNLMS algorithm turns out to be more effective than the LMS algorithm in both convergence speed and estimation accuracy.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.3
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• pp.107-112
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• 2013

Cu(In,Ga)$Se_2$ (CIGS) thin films were annealed on molybdenium/sodalime glass substrates of $300{\times}300mm^2$ by rapid thermal processing (RTP) with 2-step rising-temperature times in $N_2$ ambient. Morphological property, structural characteristics and chemical composition of the precursor of CIGS thin films were influenced directly with a change of $1^{st}$-step rising-temperature time in RTP whereas there is no significant difference with the different $2^{nd}$-step rising-temperature time (final crystallization temperature). The shorter $1^{st}$-step rising-temperature time in RTP obtained the higher photovoltaic cell efficiency from 7.469% to 8.479% even though the ideal composition in CIGS thin films could not be accoplished in this study.

• Smart Structures and Systems
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• v.14 no.6
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• pp.1131-1150
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• 2014

One of the issues in extending the range of applicable problems of real-time hybrid simulation is the computation speed of the simulator when large-scale computational models with a large number of DOF are used. In this study, functionality of real-time dynamic simulation of MDOF systems is achieved by creating a logic circuit that performs the step-by-step numerical time integration of the equations of motion of the system. The designed logic circuit can be implemented to an FPGA-based system; FPGA (Field Programmable Gate Array) allows large-scale parallel computing by implementing a number of arithmetic operators within the device. The operator splitting method is used as the numerical time integration scheme. The logic circuit consists of blocks of circuits that perform numerical arithmetic operations that appear in the integration scheme, including addition and multiplication of floating-point numbers, registers to store the intermediate data, and data busses connecting these elements to transmit various information including the floating-point numerical data among them. Case study on several types of linear and nonlinear MDOF system models shows that use of resource sharing in logic synthesis is crucial for effective application of FPGA to real-time dynamic simulation of structural response with time step interval of 1 ms.

• New & Renewable Energy
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• v.20 no.2
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• pp.17-25
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• 2024

In this study, the effect of the time step specified in a computational fluid dynamics (CFD) simulation on load response is analyzed and the drag coefficients of the floating body of floating offshore wind turbines (FOWTs) are estimated. By evaluating the error in the FOWT load response and the change in the drag-coefficient values based on the density of the time intervals, this study aims to establish a time-interval setting that minimizes the time and cost of CFD simulations for selecting drag-coefficient values. Practical CFD utilization strategies necessary for the calibration of medium-to high-fidelity analysis tools are presented. Based on a comparative analysis of CFD simulations conducted at various time intervals, the results confirmed that under a certain time interval that sufficiently considers various factors, the accuracy of the FOWT response with respect to density shows minimal differences, thereby providing an efficient utilization method for CFD simulations in FOWT design and analysis.

• Journal of The Korean Society of Integrative Medicine
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• v.10 no.4
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• pp.145-151
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• 2022

Purpose : Stroke patients exhibit abnormal walking patterns such as slow walking speed and asymmetrical walking values. The recovery of symmetrical walking in the stance phase using a treadmill means improvements in walking speed and asymmetrical walking. The purpose of this research was to investigate the effect of unilateral step treadmill training (USTT) on gait speed and the recovery of symmetrical walking in chronic stroke patients. Methods : Fifteen patients (11 men and 4 women) with chronic stroke participated in this study. The 10-meter walk test (10MWT) and GAITRite system were used to determine the intervention-related changes in gait speed and symmetrical walking values such as non-paretic step length (NSL), non-paretic step time (NST), paretic single-support time (PSST), step length asymmetry (SLA), and step time asymmetry (STA) after USTT. All participants completed USTT and underwent measurements at 3 different times: at pretest, posttest, and the follow-up test. Repeated-measures analysis of variance was used to compare walking speed and asymmetrical walking values. The statistical significance level was set at p<.05. Results : Walking speed by 10MWT (p<.05) showed significant improvements after USTT as follows: at pretest and posttest (p<.05), posttest and follow-up test (p<.05), and pretest and follow-up test (p<.05). Recovery of symmetrical walking patterns such as NSL (p<.05), NST (p<.05), and SLA (p<.05) were observed after USTT. However, no significant improvements were found in PSST (p>.05) and STA (p>.05) in symmetrical gait. Conclusion : This study suggests that USTT may have a positive effect on walking speed and symmetrical walking patterns in chronic stroke patients. Thus, this study contributes to the existing knowledge about the usefulness of USTT for the effective management of patients with chronic stroke. Further studies are needed to generalize these findings.

• Journal of Soil and Groundwater Environment
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• v.25 no.4
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• pp.35-47
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• 2020

Step-drawdown test is one of the widely-used aquifer test methods to evaluate aquifer and well losses. Various approaches have been suggested to estimate well losses using the step-drawdown test data but the uncertainties associated with data interpretation and analysis still exist. In this study, we applied three different step-drawdown test analysis methods -Jacob (1947), Labadie and Helweg (1975), Gupta (1989)- to the step-drawdown test data in Seobu-myeon, Hongseong-gun, South Korea and estimated aquifer and well losses. Comparisons of different step-drawdown test analysis methods revealed that the estimated well losses showed different values depending on the applied methods and these variations are likely to be related to the limitation of the assumptions for each analysis method. Based on the detailed analysis of time-drawdown data, we performed step-drawdown test analysis after removing outlier data during the initial stage of step drawdown test. The results showed that the application of the revised time-drawdown data could substantially decrease the error of the analysis as well as the variations in the estimated well losses from different analysis methods.

• 제어로봇시스템학회:학술대회논문집
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• 1999.10a
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• pp.116-120
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• 1999

The step response of the Manabe standard form[1］has little overshoot and shows almost same waveforms regardless of the order of the characteristic polynomials. In some situations it is difficult to control the rise time and settling time simultaneously of the step response of the Manabe standard form. To control its rise time and settling time efficiently, we develop the generalization of the Manabe standard form: we try to find out the SRFS(Slow Rise time & Fast Settling time) form which has the slower rise time and faster settling time than those of the Manabe standard form. we also consider the other three forms: FRSS(Fast Rise time & Slow Settling time), SRFS(Slow Rise time ＆ Fast Settling time) and SRSS(Slow Rise time & Slow Settling time) forms. In this paper, by using the genetic algorithm, we obtain all the coefficient of the four forms we mention above. Finally, we design a controller for a given plant so that the overall system has the performance that the rise time is faster, the settling time is slower than those of the Manabe standard form.