• 대한전기학회논문지
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• 제37권7호
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• pp.490-497
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• 1988

This paper is concerned with the robust stability of linear quadratic state feedback regulators for infinite dimensional systems in the presence of system uncertainties Several robustness results ensuring the asymptoitc stability and exponential stability of the perturbed closed loop system are derived for a class of nonlinear perturbations of the system and input operators satisfying the matching condition. For the case where the input space is finite dimensional, some robust properties of the state feedback regulator designed on the basis of the linear quadratic regulator for finite dimensional unstable modes are also discussed seperately.

• 한국정밀공학회지
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• 제7권3호
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• pp.103-114
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• 1990

Many high speed mechanical systems incorporate gearing for speed reduction. This study investigates the stability of mulit-rotor geared systems supported on oil film bearings taking into consideration the coupling between torsional and lateral dynamics. The emphasis of the study is on the analysis of the interaction between the combined torsional and whirl insta- bilities. The feasility of inducing a lateral and the torsional instability to neutralize an anticipated unstable condition is investigated. The possibility of suppressing the instabilities by controlling the parameters of the oil film bearings is also considered.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.1209-1212
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• 1996

In this paper, we design a stabilizing controller with disturbance rejection properties for multirate sampled-data systems which have periodic output measurement scheme. We assume that the plant is open-loop unstable and the disturbance consists of a sum of finite number of sine waves with different frequencies. A sufficient condition for maintaining observability in multirate sampled-data systems is derived. The proposed controller has an IMC structure and can be decomposed into the filtered-disturbance estimator and the inverse of the fast uniform sampled model of the pre-stabilized plant. An example is presented for illustrations.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 전력전자학술대회 논문집
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• pp.314-318
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• 1998

This paper discusses the development of electronic ballast for neon lamp as an application of a zero voltage switching high frequency inverter. Abnormal increase of secondary voltage due to grounded fault or partial damage of serial arranged loads is clarified and the protection circuit for this abnormal voltage increase is proposed. Also stable lighting condition for removing the unstable characteristics due to different load conditions is proposed.

• 한국광학회:학술대회논문집
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• 한국광학회 2006년도 하계학술발표회 논문집
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• pp.431-432
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• 2006

• Journal of applied mathematics & informatics
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• 제41권2호
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• pp.363-372
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• 2023

We consider Kuo problem of hydrodynamic stability which deals with incompressible, inviscid, parallel shear flows in the 𝛽-plane. For this problem, we derived instability region without any approximations and which intersects with Howard semi-circle region under certain condition. Also, we derived upper bound for growth rate and amplification factor of an unstable mode and proved Howard's conjecture.

• 한국지반환경공학회 논문집
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• 제17권4호
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• pp.17-31
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• 2016

Many researchers have evaluated the influence of vegetation cover on slope stability. However, due to the extensive variety of site conditions and vegetation types, different studies have often provided inconsistent results, especially when evaluating in different regions. Therefore, additional studies need to be conducted to identify the positive impacts of vegetation cover for slope stabilization. This study used the Transient Rainfall Infiltration and Grid-based Regional Slope-stability Model (TRIGRS) to predict the occurrence of landslides in a watershed in Jinbu-Myeon, Pyeongchang-gun, Korea. The influence of vegetation cover was assessed by spatially and temporally comparing the predicted landslides corresponding to multiple trials of cohesion values (which include the role of root cohesion) and real observed landslide scars to back-calculate the contribution of vegetation cover to slope stabilization. The lower bound of cohesion was defined based on the fact that there are no unstable cells in the raster stability map at initial conditions, and the modified success rate was used to evaluate the model performance. In the next step, the most reliable value representing the contribution of vegetation cover in the study area was applied for landslide assessment. The analyzed results showed that the role of vegetation cover could be replaced by increasing the soil cohesion by 3.8 kPa. Without considering the influence of vegetation cover, a large area of the studied watershed is unconditionally unstable in the initial condition. However, when tree root cohesion is taken into account, the model produces more realistic results with about 76.7% of observed unstable cells and 78.6% of observed stable cells being well predicted.

• 디지털융복합연구
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• 제10권1호
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• pp.399-405
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• 2012

본 연구의 목적은 지지 면이 다른 조건(안정, 상지 불안정, 하지 불안정, 상하지 불안정)에서의 푸시업 플러스운동이 어깨 안정근의 근 활성도에 미치는 영향을 비교 하는 것이다. 본 연구에서는 18명의 정상인이 자발적인 참여를 했다. 측정 방법은 지지 면이 다른 조건에서 푸시압 플러스를 수행 하는 동안 위세모근, 큰가슴근, 앞톱니근을 표면 근전도로 기록 하였다. 연구 대상자에게는 총 7일 동안 측정을 실시하였다. 결과 값은 푸쉬업 플러스를 실시한 실효치 값의 평균으로 제시하였다. 분석 방법은 반복 측정된 일원배치 분산분석을 이용하였다. 그 결과 위세모근과, 큰가슴근은 다른 조건의 지지 면과의 비교에서는 유의한 차이가 나타나지 않았다(p>.05). 하지만 앞톱니근에서는 상하지가 불안정한 조건일 때 푸쉬업 플러스 운동을 하는 동안 근 활성도가 가장 많이 향상되었다(p<.05). 따라서 본 연구에서는 어깨의 안정성을 향상시키기 위한 푸쉬업 플러스 운동 방법으로는 상 하지가 모두 불안정한 지지 면을 제공 할 때 가장 효과적 이였다.

• 대한기계학회논문집B
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• 제23권11호
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• pp.1434-1443
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• 1999

The turbulent fluctuations of temperature and two components of velocity have been measured with hot- and cold-wires in the Thermally Stratified Wind Tunnel(TSWT). Using the fin-tube heat exchanger type heaters and the neural network control algorithm, both stable ($dT/dz=109.4^{\circ}C$) and unstable ($dT/dz=-49.1^{\circ}C$) stratifications were realized. An ambient air jet was issued normally into the cross flow($U_{\infty}=1.0 m/s$) from a round nozzle(d = 6 mm) flushed at the bottom waII of the wind tunnel with the velocity ratio of $5.8(U_{jet}/U_{\infty})$. The characteristics of turbulent dispersion in the cross flow jet are found to change drastically depending on the thermal stratification. Especially, in the unstable condition, the vertical velocity fluctuation increases very rapidly at downstream of jet. The fluctuation velocity spectra and velocity-temperature cospectra along the jet centerline were obtained and compared. In the case of stable stratification, the heat flux cospectra changes Its sign from a certain point at the far field because of the restratification phenomenon. It is inferred that the main reason in the difference between the vertical heat fluxes is caused by the different length scales of the large eddy motions. The turbulent kinetic energy and scalar dissipation rates were estimated using partially non-isotropic and isotropic turbulent approximation. In the unstable case, the turbulent energy dissipation decreases more rapidly with the downstream distance than in the stable case.

• 대한간호학회지
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• 제48권3호
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• pp.266-278
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• 2018

Purpose: The aim of this study was to develop a substantive theory on self-management conducted by the adolescents with chronic kidney disease from their lived experience. Methods: Data was collected through in-depth interviews from May to December in 2015 with thirteen adolescents with chronic kidney disease. The data collected were analyzed on the basis of Strauss and Corbin's grounded theory. Results: The core of the category found in this study was "overcoming the unstable sense of self- control and integrating disease experience into their life". The causal conditions triggering the central phenomenon were "restriction in daily life" and "manifestation and aggravation of symptom". The central phenomenon in the experience of self-management within the adolescents with chronic kidney disease was "unstable sense of self control". The intervening condition for unstable self control were "micro system support" and "motivational resources". This study found that the adolescents with chronic kidney disease followed a series of strategies when they faced the central phenomenon, including; passive coping, reappraisal of illness, active coping, compliance with treatment, controlling physical activity, and adjusting school life. With these strategic approaches, the adolescents with chronic kidney disease could maintain their active lifestyles and achieve their health behaviors. The process of self-management by these adolescents passed through four phases; limited experience caused by diseases, effort for normalization, reorganizing their daily lives, and integration with daily lives and self-management. Conclusion: This Study explored the process and experience of self-management of adolescents with chronic kidney disease. These findings can be used for basis for developing substantive theory and nursing intervention strategy for adolescents with chronic kidney diseases.