• Wind and Structures
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• 제17권4호
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• pp.399-417
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• 2013

The structural vibration suppression with active constrained layer damping (ACLD) was widely studied recently. However, the literature seldom concerned with the vibration control on flow-induced vibration using active constrained layer. In this paper the wind induced vibration of cantilevered beam is analyzed and suppressed by using random theory together with a velocity feedback control strategy. The piezoelectric material and frequency dependent viscoelastic layer are used to achieve effective active damping in the vibration control. The transverse displacement and velocity in time and frequency domains, as well as the power spectral density and the mean-square value of the transverse displacement and velocity, are formulated under wind pressure at variable control gain. It is observed from the numerical results that the wind induced vibration can be significantly suppressed by using a small outside active voltage on the constrained layer.

• 대한조선학회논문집
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• 제31권2호
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• pp.65-77
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• 1994

본 논문은 SWATH선의 히브 및 피치 제어에 대한 LQ이론의 상세한 응용과정을 제시한다. 부가질량과 감쇄계수를 상하동요 고유주기에서의 값으로 근사함으로써 선형 시불변 2차 연립 미분방정식이 주파수 응답 모델로부터 유도된다. 파기진력은 사인파들의 합으로서 모델링 된다. 좋은 과도응답(transient response)과 적절한 제어핀 운동을 얻기 위하여 상태 및 제어 가중행렬의 체계적인 선택과정이 제시된다. 본 논문의 제어기 설계과정의 타당성이 시간영역 및 주파수 영역에서의 시뮬레이션과 전달함수행렬의 특이값 선도에 의해 철저히 조사되어 진다. 최종 설계된 제어시스템은 본 연구의 응용이 성공적이었음을 나타내는 좋은 전체 성능을 보여준다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2002년도 ICCAS
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• pp.90.6-90
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• 2002

An active stick which has the variable force-feel characteristics is developed. A combined position and force control strategy is mechanized using a 2-axis built-in force sensor and LVDT. The 2-axis force sensor which measures the stick force felt by the operator is developed by using strain gages and appropriate instrumental amplifiers. A mathematical model of the active stick dynamics is derived, and compared with the experimental results. The frictional torque of the stick due to the mechanical contacts of several parts makes the experimental frequency responses to be dependent on the magnitude of excitation signal, and the precision closed loop control to be difficult. A friction observe...

• Structural Engineering and Mechanics
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• 제68권4호
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• pp.399-408
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• 2018

Cable supported structures have been widely used in civil engineering. Cable tension estimation has great importance in cable supported structures' analysis, ranging from design to construction and from inspection to maintenance. Even though the Bernoulli-Euler beam element is commonly used in the traditional finite element method for calculation of frequency and cable tension estimation, many elements must be meshed to achieve accurate results, leading to expensive computation. To improve the accuracy and efficiency, a dynamic finite element method for estimation of cable tension is proposed. In this method, following the dynamic stiffness matrix method, frequency-dependent shape functions are adopted to derive the stiffness and mass matrices of an exact beam element that can be used for natural frequency calculation and cable tension estimation. An iterative algorithm is used for the exact beam element to determine both the exact natural frequencies and the cable tension. Illustrative examples show that, compared with the cable tension estimation method using the conventional beam element, the proposed method has a distinct advantage regarding the accuracy and the computational time.

• Journal of Nutrition and Health
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• 제32권4호
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• pp.407-418
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• 1999

The purpose of this study was to identify dietary factors related to the incidence of diabetes mellitus in Korea. The study consisted of 165 diabetic patients, male and female, aged 30 to 70 years and 198 healthy persons as controls. Diabetic patients who had been diagnosed with diabetes mellitus for less than five years before the study period were recruited from eight different hospitals located in Seoul, Korea. Socioeconomic status, state of illness, physical activity, food habits and food intake were assessed. Food intake was assessed by food frequency questionnaire method using a 105-food frequency questionnaire developed for diabetic patients. The stress and activity indices of diabetic patients were not significantly different from control, but alcohol consumption and smoking levels were higher in diabetics than controls. Other diseases of male diabetic patients included liver diseases, digestive system diseases, and hypertension, while those of female diabetics were hypertension, neuralgia, arthritis and digestive system diseases. These disease patterns are different from Western countries whose most common complications are hypertension and hyperlipidemia. More irregular and less varied meals were found in the diabetic group compared to the control group, suggesting that diabetic patients have generally undesirable food habits. Otherwise, food and nutrient intake of diabetics did not differ greatly from the control group. It was found that diabetic patients consumed more cereals and less fruit than the control group, and also that male diabetics consumed more alcohol. The carbohydrate : protein : fat energy distribution ratio was 61.7 : 15.8 : 22.5 in male patients and 65.1 : 14.9 : 19.7 in female patients. Discriminant analysis showed that diabetes risk factors differed with sex. In male patients, the important factors were body mass index(BMI), vitamin C intake, family diabetic history and vegetable intake, while in female patients they were BMI, cereals intake, carbohydrate intake, vitamin C intake, stress, food habits and Ca intake. These results show that excessive intake of energy and fat are not the major causal factors in Korean NIDDM. Therefore, the diabetes risk factors of Western countries may not directly apply to Koreans. Mors study is needed to clarify the risk factors of Korean NIDDM.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1999년도 전력전자학술대회 논문집
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• pp.155-158
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• 1999

In the high speed range for Vector control of Synchronous Reluctance Motor, the effect of iron loss and the cross-coupling of dq axis currents is dependent on the increase of the operating frequency can not be negligible. In this paper, we propose a decupling Vector control of dq axis current that the effect of iron loss is eliminated, and confirm that through simulation results.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 I
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• pp.213-218
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• 2001

A magnetorheological(MR) engine mount for a passenger vehicle and its vibration control performance is experimentally evaluated. A mixed-mode model for the MR engine is derived by incorporating Herschel-Bulkely model of the MR fluid. After analyzing the field-dependent damping force, a appropriate size of the MR engine mount is manufactured. The field-dependent is displacement transmissibility of the engine mount is evaluated in the frequency domain at various excitation levels. In addition, time-dependant damping force is experimentally investigated by changing the excitation amplitude.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 춘계학술대회 논문집
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• pp.1023-1026
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• 2007

CBTC (Communication Based Train Control) is a railroad system, using wireless communication for data transmission between on-board units and ground units, that makes ground computer periodically collect position and speed data from each train and transmits the preceding train's distance data up to speed limit point so as to make on-board control unit control the optimum train speed. Due to the fact that wireless communication system for train control employs only limited frequency band and output frequency, a number of ground communication units should be installed at track-side; also a running train should carry out Handover function which maintains the communication by accessing a new communication channel of the adjacent on-board communication units in accordance with the output of received radio wave. Especially CBTC is largely dependent on Handoff function between ground communication units. Therefore, this paper provides the method of identification of hazard between ground communication units and on board units.

• 한국학교보건학회지
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• 제8권2호
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• pp.315-326
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• 1995

This study was performed to find variables which affect oral health care of infants. The subjects were 439 infants and their mothers who live in suburban area. Oral examinations for the infants were conducted and the questionnairs were given to infants' mothers. Toothbrushing frequency, oral hygiene score, the percentage of filled teeth among decayed teeth, and dental treatment experience of infants were used as dependent variable, respectively. Demographic, socio-economic variables and the other variables which might affect oral health care of infants were used as independent variables. Correlation analysis and analysis of variance were used for the independent variables of toothbrushing frequency, oral hygiene score, and the percentage of filled teeth among decayed teeth of infant. Chi-Square and Student's t-test were used for the dependent variables of dental treatment experience of infant. The obtained results were as follows; 1. Toothbrushing frequency of mother and internal locus of oral control of mother were the factors which affect toothbrusing frequency of infants. 2. Oral health belief of mother was the factor which affect oral hygiene score of infants. 3. Age of infant was the factor which affect the percentage of filled teeth among decayed teeth. 4. Age of infant and educational level of infant's mother were the factors which affect the infants' consumption of dental treatment.

• Journal of Power Electronics
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• 제15권3호
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• pp.577-586
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• 2015

The combination of voltage feedforward and feedback control is a conventional approach for correcting the power factor in single-phase ac-dc boost converters. The feedback duty ratio increases significantly with an increase of the line frequency and input inductance. Therefore, the performance of the conventional approach is highly dependent on the bandwidth of the feedback controller. As a result, the input power quality can be significantly exacerbated due to uncompensated duty ratios if the feedback controller is limited. This paper proposes an input impedance and current feedforward control method to reduce the control portion of the feedback controller. The findings in this paper are 1) the theoretical derivation and analysis of variations of line frequency and input inductance on a power factor correction approach, 2) guaranteed consistent performance in a wide range of conditions, and 3) that a low switching frequency can be utilized by the proposed method. A MATLAB/Simulink model and a 1.2kW dual boost converter are built to demonstrate the effectiveness of the proposed method.