• Physical Therapy Korea
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• v.11 no.1
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• pp.69-74
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• 2004

Hemiplegic patients usually present with difficulty maintaining balance. Balance retraining is the major component of rehabilitation program for patients with neurological impairment. The purpose of this study was to investigate the effects of prorpioceptive exercise program on the improvement of balance in the patients with chronic hemiplegia. Thirty subjects (mean age $57.0{\pm}9.8$) were recruited and the subjects were divided into a proprioceptive group and a visual group. The subjects for the proprioceptive group were participated in the proprioceptive exercise program for 4 weeks, and the visual group were treated visual feedback training using Balance Master. At 4 week follow-up test, Berg Balance Scale significantly improved 1.1 points (p<.01), Timed Up & Go test improved 4.2 second (p<.01), and weight distribution during sit to stand also improved 5.0% (p<.01). As a result of this study, the proprioceptive control approach improved dynamic balance in the patients with chronic hemiplegia. It is suggested that there was no benefit of visual feedback training like as Balance Master when administrated in combination with other physical therapy interventions, compared with physical therapy alone using proprioceptive control approach to hemiplegia.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.197-202
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• 1991

Recently, an output feedback variable structure control scheme(OFVSCS) is proposed to remove the assumption of full state availability and to make the application of VSC scheme to the high order systems with unmeasurable state variables possible. In this paper, a design method of an output feedback variable structure control system (IOFVSCS) that guarantees the invariance of the sliding mode against process parameter variation and external disturbance is proposed. The IOFVSCS is composed of two components; dynamic switching surface driven by measured I/0 informations and switching control input generator driven by switching surface information and measured output, where the two components are constructed by adopting unknown vector modelling approach. The invariance condition for the IOFVSCS is proved to be the same as that of the conventional VSCS. Simulation results show that the IOFVSCS can be designed to have robust properties better than that of the conventional VSCS in spite that the IOFVSCS is driven by small amount of measured information.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.921-925
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• 1988

An attractive approach to speed of induction motors is to achieve full linearization via appropriate feedback. However, the prior results toward this direction are based on full feedback. In practice, rotor fluxes are not directly measurable but can be estimated using observers. We propose a nonlinear feedback controller with an observer. As t${\rightarrow}{\infty}$, the closed-loop system with our controller becomes as if it were a linearly decoupled system. We provide the stability analysis of our control method. Simulation and experimental results are also included to demonstrate the practical significance of our results.

• International Journal of Control, Automation, and Systems
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• v.6 no.4
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• pp.596-606
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• 2008

In this paper, we present a co-design methodology of dynamic optimal network-bandwidth allocation (ONBA) and adaptive control for networked control systems (NCSs) to optimize overall control performance and reduce total network-bandwidth usage. The proposed dynamic co-design strategy integrates adaptive feedback control with real-time scheduling. As part of this co-design methodology, a "closed-loop" ONBA algorithm for NCSs with communication constraints is presented. Network-bandwidth is dynamically assigned to each control loop according to the quality of performance (QoP) information of each control loop. As another part of the co-design methodology, a network quality of service (QoS)-adaptive control design approach is also presented. The idea is based on calculating new control values with reference to the network QoS parameters such as time delays and packet losses measured online. Simulation results show that this co-design approach significantly improves overall control performance and utilizes less bandwidth compared to static strategies.

• Journal of the Korean Society for information Management
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• v.32 no.1
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• pp.7-22
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• 2015

This paper describes a Web search optimization study that investigates both static and dynamic tuning methods for optimizing system performance. We extended the conventional fusion approach by introducing the "dynamic tuning" process with which to optimize the fusion formula that combines the contributions of diverse sources of evidence on the Web. By engaging in iterative dynamic tuning process, where we successively fine-tuned the fusion parameters based on the cognitive analysis of immediate system feedback, we were able to significantly increase the retrieval performance. Our results show that exploiting the richness of Web search environment by combining multiple sources of evidence is an effective strategy.

• Nuclear Engineering and Technology
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• v.51 no.6
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• pp.1540-1553
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• 2019

A nuclear power plant (NPP) is a highly complex system-of-systems as manifested through its internal systems interdependence. The negative impact of such interdependence was demonstrated through the 2011 Fukushima Daiichi nuclear disaster. As such, there is a critical need for new strategies to overcome the limitations of current risk assessment techniques (e.g. the use of static event and fault tree schemes), particularly through simulation of the nonlinear dynamic feedback mechanisms between the different NPP systems/components. As the first and key step towards developing an integrated NPP dynamic probabilistic risk assessment platform that can account for such feedback mechanisms, the current study adopts a system dynamics simulation approach to model the thermal dynamic processes in: the reactor core; the secondary coolant system; and the pressurized water reactor. The reactor core and secondary coolant system parameters used to develop system dynamics models are based on those of the Palo Verde Nuclear Generating Station. These three system dynamics models are subsequently validated, using results from published work, under different system perturbations including the change in reactivity, the steam valve coefficient, the primary coolant flow, and others. Moving forward, the developed system dynamics models can be integrated with other interacting processes within a NPP to form the basis of a dynamic system-level (systemic) risk assessment tool.

• Journal of Computational Design and Engineering
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• v.3 no.4
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• pp.312-321
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• 2016

Dynamic behaviour of a slider-crank mechanism associated with a smart flexible connecting rod is investigated. Effect of various mechanisms' parameters including crank length, flexibility of the connecting rod and the slider's mass on the dynamic behaviour is studied. Two control schemes are proposed for elastodynamic vibration suppression of the flexible connecting rod and also obtaining a constant angular velocity for the crank. The first scheme is based on feedback linearization approach and the second one is based on a sliding mode controller. The input signals are applied by an electric motor located at the crank ground joint, and two layers of piezoelectric film bonded to the top and bottom surfaces of the connecting rod. Both of the controllers successfully suppress the vibrations of the elastic linkage.

• Korean System Dynamics Review
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• v.13 no.2
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• pp.5-23
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• 2012

This paper studies dynamic relationship between cash market, forward market, and options market, from the perspective of systems thinking. It is shown that an exogenous shock to forward market can yield almost the same impact to the cash market, given a practically reasonable condition, but not vice versa. As far as options market is concerned, it matters what kind of options we deal with, who are long the option, and whether the option market maker performs dynamic hedging or not. In some cases, it is possible for the spot price to become unstable and diverge rather violently due to a strong negative feedback between the markets.

• Korean Management Science Review
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• v.23 no.1
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• pp.87-113
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• 2006

This paper describes a comprehensive approach to examine how technological innovation contributes to the renewal of the firm's competences through its dynamic and reciprocal relationship with R&D and product commercialization. Three theories of technology and innovation (R&D and technological knowledge concept, product-process concept, technological interdependence concept) are used to relate technology and innovation to strategic management. Based on those theories, this paper attempts to identify dynamic relationship between product innovation and process innovation by system dynamics, by investigating the aspect of the dynamic changes of the closed feedback circulation structure in which R&D investments drive technological knowledge accumulation, and such knowledge accumulation actualizes product innovation and process innovation, subsequently resulting in the increase of productivity, customer satisfaction, profit generation, and re-investment on R&D from the created profits. This provides the ability to assess the advantages and disadvantages of different technological innovation strategies and commitments, and the opportunity to explore equilibrium point and suggest a generalized technological innovation model under different industry environment parameters and time-strategies.

• International Journal of Control, Automation, and Systems
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• v.1 no.1
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• pp.54-67
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• 2003

In this paper, a novel estimation technique for a robust adaptive control scheme is presented for a class of uncertain nonlinear systems with a general set of uncertainty. For a class of introduced more extended semi-strict feedback forms which generalize the systems studied in recent years, a novel estimation technique is proposed to estimate the states of the fully nonlinear unmodeled dynamics without stringent conditions. With the introduction of powerful functions, the estimation error can be tuned to a desired small region around the origin via the estimator parameters. In addition, with some effective functions, a modified adaptive backstepping for dynamic uncertainties is presented to drive the output to an arbitrarily small region around the origin by an appropriate choice of the design parameters. With our proposed schemes, we can remove or relax the assumptions of the existing results.