• 대한수학회논문집
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• 제34권3호
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• pp.819-839
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• 2019

We study the stabilization of 2D g-Navier-Stokes equations in bounded domains with no-slip boundary conditions. First, we stabilize an unstable stationary solution by using finite-dimensional feedback controls, where the designed feedback control scheme is based on the finite number of determining parameters such as determining Fourier modes or volume elements. Second, we stabilize the long-time behavior of solutions to 2D g-Navier-Stokes equations under action of fast oscillating-in-time external forces by showing that in this case there exists a unique time-periodic solution and every solution tends to this periodic solution as time goes to infinity.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2009년도 정기총회 및 추계학술대회 논문집
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• pp.287-289
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• 2009

This paper deals with a parallel processing uninterruptible power supply (UPS) for sudden voltage fluctuation in computer applications to integrate power quality improvement, load voltage stabilization and UPS. To reduce the complexity, cost and number of power conversions, which results in higher efficiency, only one voltage-controlled voltage source inverter (VCVSI) is used. The system provides sinusoidal voltage at the fundamental value of 220V/60Hz for the load during abnormal utility power conditions or grid failure. Also, the system can be operated to mitigate the harmonic current and voltage demand from nonlinear loads and provide voltage stabilization for loads when sudden voltage fluctuation occur, such as sag and swell. System operation simulation demonstrates that the system protects against outages caused by abnormal utility power conditions and sudden voltage fluctuations and changes.

• Journal of Electrical Engineering and Technology
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• 제1권1호
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• pp.80-84
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• 2006

The sustained oscillation of rotor speed is often experienced in PWM inverter induction motor (IM) drive systems. In this paper the oscillation is investigated from the point of view of Hopf bifurcation theory. The sufficient and necessary conditions for existence of limit cycle are introduced to determine the bifurcation set in the stator voltage versus stator frequency plane. According to the conditions it is clarified that the bifurcation set inherently exists in the instable operation of IM. Moreover, it is numerically shown that the V/f curve can be adjusted to stabilize the sustained oscillation of rotor speed.

• 한국전기전자재료학회논문지
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• 제16권3호
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• pp.175-180
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• 2003

As the integrated circuit device shrinks to the deep submicron regime, the ion implantation process with high ion dose has been attracted beyond the conventional ion implantation technology. In particular, for the case of boron ion implantation with low energy and high dose, the stabilization and throughput of semiconductor chip manufacturing are decreasing because of trouble due to the machine conditions and beam turning of ion implanter system. In this paper, we focused to the improved characteristics of processing conditions of ion implantation equipment through the modified deceleration mode. Thus, our modified recipe with low energy and high ion dose can be directly apply in the semiconductor manufacturing process without any degradation of stability and throughput.

• 한국전문물리치료학회지
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• 제24권4호
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• pp.60-67
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• 2017

Background: Scapular downward rotation syndrome (SDRS) is a common scapular alignment impairment that causes insufficient upward rotation and muscle imbalance, shortened levator scapulae (LS) and rhomboid, and lengthened serratus anterior (SA) and trapezius. A modified shrug exercise (MSE), performing a shrug exercise with the shoulders at $150^{\circ}$ abduction, is known as an effective exercise to increase scapular stabilizer muscle activation. Previous studies revealed that scapular exercise are more effective when combined with trunk stabilization exercises in decreasing scapular winging and increasing scapular stabilizer muscle activation. Objects: The purpose of our study was to clarify the effect of MSE with or without trunk stabilization exercises in subjects with SDRS. Methods: Eighteen volunteer subjects (male=10, female=8) with SDRS were recruited for this experiment. All subjects performed MSE under 3 different conditions: (1) MSE, (2) MSE with an abdominal draw-in maneuver (ADIM), and (3) MSE with an abdominal expansion maneuver (AEM). The muscle thickness of the lower trapezius (LT) and the SA were measured using an ultrasonography in each condition. Electromyography (EMG) data were collected from the LT, LS, SA, and upper trapezius (UT) muscle activities. Data were statistically analysed using one-way repeated analysis of variance at a significance level of .05. Results: The muscle thickness of the LT and the SA were the significant different in the MSE, MSE with ADIM (MSE+ADIM) and MSE with AEM (MSE+AEM) conditions (p<.05) In both LT and SA, the order of thick muscle thickness was MSE+AEM, MSE+ADIM, and MSE alone. No significant differences were found in the EMG activities of the SA, UT, LS, and LT in all condition. Conclusion: In conclusion, MSE is more beneficial to people with SDRS when combined with trunk stabilization exercises by increased thickness of scapular stabilizer muscles.

• 대한기계학회논문집B
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• 제35권4호
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• pp.431-438
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• 2011

비예혼합 화염의 부상 조건은 연소기의 운전 조건을 한정하는 매우 중요한 변수이다. 동축류 층류 비예혼합화염의 경우 점성계수와 물질 확산 계수의 비로 정의되는 슈미트 수가 1 보다 큰 조건에서 안정적인 부상화염이 존재하고 그 반대의 경우 부상이 불가능한 것으로 알려져 있다. 본 연구에서는 동축 관내에서의 화염의 부상 특성에 대해 슈미트 수가 1 보다 큰 프로판과 슈미트 수가 1 보다 작은 메탄 비예혼합 화염의 부상 안정화를 실험적으로 비교하였다. 그 결과, 제한된 공간에서는 슈미트 수가 1 보다 작은 조건에서도 안정적인 부상화염이 존재할 수 있음을 확인하였다. 그 원인 규명을 위해 간단한 비반응 유동장에 대한 수치해석을 수행하였다. 결론적으로 개방공간에서와는 달리 관내 조건에서는 유한한 크기의 화염 공간으로 인해 인접한 상류에서 유동 재편이 물질확산에 비해 선택적으로 재편됨으로써 새로운 안정화 기구가 형성될 수 있음을 확인하였다. 이러한 결과는 제한된 공간내에 화염이 형성되는 일반적인 연소기의 화염안정화 설명에 중요한 단서를 제공한다.

• 한국항해항만학회지
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• 제36권5호
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• pp.379-385
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• 2012

본 논문에서는 수상 및 수중운동체의 안정성 및 안정화기법에 관해 고찰한다. 선박이 운동을 하게 되면 부가질량이 변하게 되고 대칭인 시스템행렬이 비대칭이 된다. 비대칭성에 따라 시스템의 안정성해석방법도 달라지는데 예를 들어 가속도 피드백을 통해 비대칭요소를 제거하여 대칭으로 변환시키는 것이 가장 대표적인 해석 및 안정화 기법이다. 시스템 모델자체는 어디까지나 모델이기 때문에 대상시스템을 명확하게 수식으로 표현할 수 없으므로 피드백에 의한 비대칭요소를 소거시키는 방법은 타당하지 못하다. 따라서 본 논문에서는 대칭행렬이 비대칭행렬로 변하는 제약에 구애받지 않는, 보다 일반성을 갖는 안정성해석법을 제안하였다. 그리고 시스템 안정성 조건을 행렬부등식으로 변환하여 나타내었다. 이것은 안정성 해석 및 안정화를 위한 제어이득을 효율적으로 계산할 수 있는 방법으로 다양한 제약조건에도 유연하게 대응할 수 있다. 시뮬레이션을 통해 제안한 기법의 유효성을 검증하였다.

• 한국항공우주학회지
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• 제37권4호
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• pp.399-405
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• 2009

위성 카메라를 위한 초점면부 영상 안정화 장치는 영상이 맺히는 초점면부의 운동외란을 제거함으로써 위성 카메라의 영상 품질을 향상 시킬 수 있는 효율적인 방법 중 하나이다. 본 연구의 목적은 초점면부 안정화 기법을 소개하고 초점면부 영상 안정화 장치 액츄에이터의 응답 및 추력에 대한 최적의 구동 조건을 결정하는 것이다. 이를 위해 다양한 구동 조건에 따른 영상화 안정화 장치의 마찰 구동형 압전 액츄에이터의 응답성과 추력을 실험적으로 조사하였다. 실험결과로부터 마그네슘 슬라이더에 대한 최적의 구동 주파수는 70 kHz, 듀티비는 27% 였다.

• 대한기계학회논문집B
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• 제33권9호
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• pp.699-708
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• 2009

To understand hydrogen jet liftoff height, the stabilization mechanism of turbulent lifted jet flames under non-premixed conditions was studied. The objectives were to determine flame stability mechanisms, to analyze coexistence of two different flame structure, and to characterize the lifted jet at the flame stabilization point. Hydrogen flow velocity varied from 100 to 300 m/s. Coaxial air velocity was changed from 12 to 20 m/s. Simultaneous velocity field and reaction zone measurements used, PIV/OH PLIF techniques with Nd:YAG lasers and CCD/ICCD cameras. Liftoff height decreased with the increase of fuel velocity. The flame stabilized in a lower velocity region next to the faster fuel jet due to the mixing effects of the coaxial air flow. The flame stabilization was related to turbulent intensity and strain rate assuming that combustion occurs where local flow velocity and turbulent flame propagation velocity are balanced. At the flame base, two different flame structures were found that was the partial premixed flames and premixed flame.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2009년도 학술발표회 초록집
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• pp.2078-2082
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• 2009

Riparian vegetation distribution patterns and diversity relative to various fluvial geomorphic channel patterns, stream bank stabilization methods, and stream flow processes are described and interpreted for selected stream of Goesan, Central Korea. Idong Stream Pilot Project, which began in May 2003 and finished in December 2003, was selected to develop effective methods. The project aim to maintain or increase stream bank stabilization ecosystem goods and services while protecting downstream and stream bank ecosystem. A number of protecting methods which are a Flight of fieldstone, Vegetation block, Green river block, Stone net, Green environment block, Eco friendly cobble, Vegetation mat and Geo green cell and Firefly block were applied on the bank of Idong stream. The stream sites have been monitored about flora conditions each method in 2007. We selected 12 points for summer seasons to separately investigate in left bank, right bank and river bed. The main purpose of this study was to find out suitable methods and to improve stream restoration techniques for ecosystem. On the stream bank, Eco friendly cobble method(9.57) was the highest average of vegetation cover and Firefly block method(3.87) was the lowest average in applied methods.