• Journal of Institute of Control, Robotics and Systems
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• v.9 no.9
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• pp.658-663
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• 2003

In deterministic design of feedback controllers for uncertain dynamic systems, the upper bound of the uncertainty is very important to guarantee the stability of the closed loop system. In this paper, we assume that the upper bound of the uncertainty is formulated using a Fredholm integral equation of the first kind, that is, an integral of the product of a predefined kernel with an unknown influence function. We propose an adaptation law that is capable of estimating this upper bound. Using this adaptive upper bound, we design an adaptive variable structure control (AVSC), which guarantees asymptotic stability/ultimate boundedness of uncertain dynamic systems. The illustrative example shows the proposed AVSC is effective for uncertain dynamic systems.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1998.03a
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• pp.39-42
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• 1998

This paper proposes an adaptive fuzzy control scheme for a class of continuous-time nonlinear dynamic systems for which an explicit linear parameterization of the uncertainty is either unknown or impossible. In order to improve robustness under approximation errors and disturbances the proposed scheme includes deadzone in adaptation laws which varies its size adaptively. The assumption of known bounds on the approximation errors and disturbances is not required since those are estimated using adaptation laws. The overall adaptive scheme is proven to guarantee uniform ultimate boundedness in the Lyapunov sense.

• ETRI Journal
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• v.39 no.5
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• pp.695-706
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• 2017

This paper presents a caching algorithm that offers better reconstructed data quality to the requesters than a probabilistic caching scheme while maintaining comparable network performance. It decides whether an incoming data packet must be cached based on the dynamic caching probability, which is adjusted according to the priorities of content carried by the data packet, the uncertainty of content popularities, and the records of cache events in the router. The adaptation of caching probability depends on the priorities of content, the multiplication factor adaptation, and the addition factor adaptation. The multiplication factor adaptation is computed from an instantaneous cache-hit ratio, whereas the addition factor adaptation relies on a multiplication factor, popularities of requested contents, a cache-hit ratio, and a cache-miss ratio. We evaluate the performance of the caching algorithm by comparing it with previous caching schemes in network simulation. The simulation results indicate that our proposed caching algorithm surpasses previous schemes in terms of data quality and is comparable in terms of network performance.

• Journal of Korea Water Resources Association
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• v.50 no.2
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• pp.121-128
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• 2017

In this study, robustness index and uncertainty analysis were proposed to quantify the risk inherent in the process of climate change vulnerability assessment. The water supply vulnerability for six metropolitan cities (Busan, Daegu, Incheon, Gwangju, Daejeon, and Ulsan), except for Seoul, were prioritized using TOPSIS, a kind of multi-criteria decision making method. The robustness index was used to analyze the possibility of rank reversal and the uncertainty analysis was introduced to derive the minimum changed weights of the criteria that determine the rank reversal between any paired cities. As a result, Incheon and Daegu were found to be very vulnerable and Daegu and Busan were derived to be very sensitive. Although Daegu was relatively vulnerable against the other cities, it can be largely improved by developing and performing various climate change adaptation measures because it is more sensitive. This study can be used as a preliminary assessment for establishing and planning climate change adaptation measure.

• Journal of Korean Academy of Nursing
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• v.46 no.2
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• pp.271-282
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• 2016

Purpose: This study was done to explore adaptation experience of living kidney donors after donation. Specific aims were to identify challenges donors face in the process of adaptation following surgery and how they interact with recipients and other people. Methods: Grounded theory methodology was utilized. Participants were 13 living kidney donors at six months or more after donation. Data were collected by in-depth interviews with individual participants. Data were analyzed using constants comparative method with theoretical saturation. Results: A core category emerged as 'keeping the fences of my family in spite of vulnerability'. The adaptation process after donation was manifested in four phases: exploration, balance, maintenance, and acclimatization. Phenomenon was perception of vulnerability. Strategies to manage the vulnerability were assessing changes of body awareness, tailoring regimen to one's own body condition, coping with health problems, keeping restoration of health, and ruminating on the meaning of one's kidney donation. Consequences were reestablishing family well-being, realizing the values of one's kidney donation, and living with uncertainty. Conclusion: Findings of the study indicate that there is a need for health professionals to understand the vulnerability of living kidney donors and help their family system maintain a healthy and productive life. The results of this study can be used to develop phase-specific, patient-centered, and tailored interventions for living kidney donors.

• Journal of Korean society of Dental Hygiene
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• v.10 no.4
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• pp.735-744
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• 2010

Objectives : The purpose of this study was to examine the stressors and stress-adaptation patterns of students preparing for the national dental hygiene certification examination. Methods : The subjects in this study were dental hygiene juniors in four selected colleges located in the metropolitan area. After a survey was conducted, the collected data were analyzed. Results : 1. Concerning motivation of choosing the department of dental hygiene, the largest group that accounted for 72.2 percent chose it due to employment prospects. As to satisfaction level with the department, 40.4 percent were satisfied. In relation to employment prospects, 54.1 percent thought the prospects were bright. 2. They got a mean of 3.23 in stressors. To be specific, they felt the most stress due to test anxiety(3.70), followed by leisure insufficiency (3.21), the uncertainty of the future(3.18) and parental pressure(2.64). 3. They got a mean of 2.02 in stress-adaptation method. They got 2.31 and 1.72 in long-term and short-term adaptation respectively, which showed that long-term stress adaptation method were more prevailing than short-term ones. 4. As for the relationship of the stressors, there was positive correlation among all the test anxiety, future uncertainty, leisure insufficiency and parental pressure, and their correlation was statistically significant(p<0.000). 5. Regarding connections between general characteristics and the stressors, whether they spent two years or more for college admission, satisfaction level with the dental hygiene department, employment prospects and health status made significant differences to the stressors (p<0.05), and there were significant gaps in adaptation patterns according to academic standing, satisfaction level with the department and health state(p<0.05). Conclusions : The dental hygiene students were under great pressure since they had to prepare for the national dental hygiene certification examination to become a certified dental hygienist, one of professional health care workers. Therefore stress counseling programs and stress-coping programs should be developed to relieve the stress of dental hygiene students who are going to take the national dental hygiene certification examination. And they should be assisted to stay away from stress and to handle their stress in a more active manner.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.18 no.2
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• pp.79-88
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• 2015

Preparations need to be made for Korean pine(Pinus koraiensis) in anticipation of climate change because Korean pine is an endemic species of South Korea and the source of timber and pine nut. Therefore, climate change adaptation policy has been established to conduct an impact assessment on the distribution of Korean pine. Our objective was to predict the distribution of Korean pine while taking into account uncertainty and afforestation conditions. We used the 5th forest types map, a forest site map and BIOCLIM variables. The climate scenarios are RCP 4.5 and RCP 8.5 for uncertainty and the climate models are 5 regional climate models (HadGEM3RA, RegCM4, SNURCM, GRIMs, WRF). The base period for this study is 1971 to 2000. The target periods are the mid-21st century (2021-2050) and the end of the 21st century (2071-2100). This study used the MaxEnt model, and 50% of the presences were randomly set as training data. The remaining 50% were used as test data, and 10 cross-validated replicates were run. The selected variables were the annual mean temperature (Bio1), the precipitation of the wettest month (Bio13) and the precipitation of the driest month (Bio14). The test data's ROC curve of Korean pine was 0.689. The distribution of Korean pine in the mid-21st century decreased from 11.9% to 37.8% on RCP 4.5 and RCP 8.5. The area of Korean pine at an artificial plantation occupied from 32.1% to 45.4% on both RCPs. The areas at the end of the 21st century declined by 53.9% on RCP 4.5 and by 86.0% on RCP 8.5. The area of Korean pine at an artificial plantation occupied 23.8% on RCP 4.5 and 7.2% on RCP 8.5. Private forests showed more of a decrease than national forests for all subsequent periods. Our results may contribute to the establishment of climate change adaptation policies for considering various adaptation options.

• Journal of Environmental Impact Assessment
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• v.28 no.1
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• pp.1-22
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• 2019

This study aims at deriving the implications for adaptation policy and research target regarding climate change risk assessment in ecosystem sector in Korea. The common ground of exemplary cases of "world leaders" in terms of adaptation policies and researches was that they emphasize nationwide study on climate change on biodiversity and ecosystem in target of establishing scientific evidence-bases and reducing uncertainty for their national adaptation policies and plans. In light of this trend, Korean government should settle down more successful adaptation structure by leading adaptation system in further national policy-settings to observe UNFCCC and CBD integratedly and effectively, considering the economic value of adaptation in policy, and strengthening scientific research programs and technology developments. Moreover, risks assessment based on diagnoses and analysis on the risk factors (hazard, exposure, and vulnerability) for climate change in nationwide habitats and species and consolidations with subsequent adaptation strategies could make adaptations in ecosystem sector more effective and successful.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.381-393
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• 2016

This was a qualitative study to explore and better understand the adaptation experience and processes of peoples with fibromyalgia syndrome (FMS), as well as to develop a substantive theory using the grounded theory method. There were 13 patients (12 females and 1 male) who received FMS treatment from Rheumatic Medicine outpatient department of one general hospital. The data were collected through an in-depth interview between January and May of 2014. Transcribed interview contents were analyzed by the grounded theory method of Corbin and Strauss (2008). As a result, a total of 98 concepts, 26 sub-categories, and 10 categories were identified through the open coding process. The process of adaptation experience showed 4 steps: perception of uncertainty and limited condition, evaluation of self-control possibility and determinations of expectations of life, searching and trying of strategies, as well as self-regulation. The 4 types of adaptation experience were expansionary, complacently, effusively and withering. The 'protective self-regulation' theory was derived from the core category of 'learning to self-regulation method'. Patients with FMS has repeatedly attempted these strategies of protective self-regulation in order to gain stability from uncertainty and limited condition of the disease. Based on these results, it is necessary to develop an educational program for patients and families which has appropriate nursing intervention strategies in accordance with the types of adaptation.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.11
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• pp.1081-1087
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• 2006

Generally, biped walking is difficult to control because a biped robot is a nonlinear system with various uncertainties. In this paper, we propose a hybrid sliding-mode control method using a WNN uncertainty observer for stable walking of the 5-link biped robot with model uncertainties and the external disturbance. In our control system, the sliding mode control is used as main controller for the stable walking and a wavelet neural network(WNN) is used as an uncertainty observe. to estimate uncertainties of a biped robot model, and the error compensator is designed to compensate the reconstruction error of the WNN. The weights of WNN are trained by adaptation laws that are induced from the Lyapunov stability theorem. Finally, the effectiveness of the proposed control system is verified through computer simulations.