• 한국인터넷방송통신학회논문지
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• 제24권3호
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• pp.41-47
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• 2024

Internet of Things (IoT)의 성능 발전 및 보급으로 다양한 위치 기반 서비스가 제공되고 있으며, 요구되는 서비스의 목적에 맞게 다양한 거리 추정 기법들이 연구되고 있다. 기존 거리 추정 기법은 태그와 앵커가 직접 신호를 교환하여 거리를 추정하기 때문에 대규모 IoT 환경에서 통신 자원을 효율적으로 사용하지 못하다는 한계점을 갖는다. 이러한 한계점을 극복하기 위해 능동적-수동적 거리 추정 기법들이 제안되었으나, 클록 드리프트 오차에 대한 이론적인 수렴성 보장과 거리 추정 기법의 특징에 대한 분석이 부족하여 정밀한 측위 결과를 도출하기 어려울 수 있다. 본 논문에서는 대규모 IoT 환경에서 정밀 측위를 위해 클록 드리프트 오차를 반영한 개선된 능동적-수동적 거리 추정 기법을 제안한다. 시뮬레이션 결과, 제안하는 개선된 능동적-수동적 거리 추정 기법은 기존 능동적-수동적 거리 추정 기법 대비 최대 94.4%, 14.4% 거리 추정 성능을 개선할 수 있음을 확인했다.

• 한국태양에너지학회 논문집
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• 제33권5호
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• pp.82-88
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• 2013

There are the stirring test and drain test in the daily performance test to determine the thermal performance of a domestic solar hot water system. The drain test is a test that measures the discharge heating rate while drain the hot water from the top of the storage tank and supply the city water to the bottom of the tank. From the perspective of the user, this drain test is more effective than the stirring test. In this study, the thermal performance were compared through the drain test for a passive type and an active type domestic solar hot water systems consisting of the same storage tank and collectors. At this point, a passive type was used the horizontal storage tanks, and an active type was used vertical storage tank. In the drain test, when the hot water drained up to the reference hot water temperature, an active type which have vertical storage tank represents excellent daily performance than a passive type which have horizontal storage tank regardless of weather conditions. The reason for this is because the vertical storage tank is advantageous to thermal stratification in the tank. After the drain test, the residual heat for the horizontal storage tank was much more than the vertical storage tank, but in the next day the amount of discharged heat were less than the those of vertical storage tank neither. Thus, the solar water heating system which have horizontal storage tank should be adopted preheating control method rather than separate using control method when connected with auxiliary heat source device.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(1)
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• pp.182-185
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• 2003

Proposed Hybrid System is composed of phase leading capacitor banks, LC passive filters and active power filter. The passive power filter in parallel connection eliminate the 5th and 7th harmonics. The Variable capacitor banks correct the most of power factor, and the active power filter takes charge of remainder,

• 대한정형도수물리치료학회지
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• 제16권2호
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• pp.40-47
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• 2010

Purpose : To exam the effects of active ankle range of motion(ROM) exercise on sciatic nerve movement and provide the evidence that use it to patients with hypomobile sciatic nerve as a nerve mobilization technique. Methods : The subjects consist of 32 asymptomatic healthy adults(male; 15, female; 17) who have limited passive straight leg raising(PSLR) ranges below 70 degrees. First, examiner measures PSLR angles at three times. Then, subject was instructed perform the active ankle ROM exercise(dorsiflexion and plantarflextion) at limited angle. After each subject completed the active ankle ROM exercise, return the starting position and examiner measures the PSLR angles at three times again. Results : First, PSLR range was no significant differences between dominant and non-dominant leg(p >.05). Second, active ankle ROM exercise significantly increased PSLR range by mean of degrees(p <.05). Third, there was no learning effects among the measurement trials(p >.05). Conclusion : These data show that active ankle ROM exercise can mobilize the sciatic nerve. Therefore, it can be applied to patients with hypomobile sciatic nerve(sliding dysfunction) as a neural mobilization technique.

• 전기전자학회논문지
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• 제17권2호
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• pp.163-167
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• 2013

이동 통신 서비스가 확대됨에 따라 인접 기지국 간의 간섭 문제가 증가하게 되었으며, 이에 따라 이동통신 시스템의 수동 상호변조왜곡(PIMD: Passive Inter-Modulation Distortion)에 대한 문제가 크게 대두되고 있다. 본 논문에서는 기존의 수동형 안테나구조에서 증폭기 등의 핵심 능동부가 기지국안테나의 방사소자에 직접 연결되는 안테나 일체형 능동안테나에 대한 새로운 PIMD 특성시험 방안을 제안하고 이에 대한 시험결과를 제시한다. 제안된 시험결과 통하여, 능동형 기지국안테나는 기존의 수동형 구조에 비하여 약 8.4dB의 PIMD 개선효과를 가지며, 제안된 PIMD 시험방식은 기지국안테나가 실제 기지국에서 운용되는 환경에 근접하게 시행됨으로써 보다 정확한 시험결과를 도출할 수 있을 것으로 판단된다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2006년도 학술발표회 논문집
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• pp.424-431
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• 2006

Many types of tuned mass dampers (TMDs), such as active TMDs, multiple TMDs, hybrid TMDs etc., have been studied to effectively reduce the dynamic responses of a structure subjected to various types of dynamic loads. In this study, we replace a passive damper by a semi-active tuned mass damper to improve the control performance of conventional TMDs (STMD). An idealized variable damping device is used as semi-active dampers. These semi-active dampers can change the properties of TMDs in real time based on the dynamic responses of a structure. The control performance of STMD is investigated with respect to various types of excitation by numerical simulation. Groundhook control algorithm is used to appropriately modulate the damping force of semi-active dampers. The control effectiveness between STMD and a conventional passive TMD, both under harmonic and random excitations, is evaluated and compared for a single-degree-of-freedom (SDOF) structure. Excitations are applied to the structure as a dynamic force and ground motion, respectively. The numerical studies showed that the control effectiveness of STMD is significantly superior to that of the passive TMD, regardless of the type of excitations.

• 전자공학회논문지
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• 제54권1호
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• pp.26-32
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• 2017

본 논문에서는 설계 요구가 높고, 전력 소모가 높은 opamp를 이용하는 기존의 능동형 적분기를, 수동형 적분기로 대체하여 고속의 저전력, 고해상도 특성을 갖는 incremental delta-sigma ADC를 소개한다. 능동형 적분기에서 수동형 적분기로의 변환을 위해, 기존의 능동형 적분기의 특성을 분석하였다. 이를 바탕으로 opamp의 설계 요구를 낮추고, 더 나아가 opamp를 사용하지 않는 저전력의 수동형 적분기를 제안하였다. 65nm 공정을 이용하여 수동형 적분기로 구성된 1차 single-bit incremental delta-sigma ADC를 설계하였다. Transistor-level 시뮬레이션 결과, 이는 supply 전압이 1.2V인 상황에서 modulator만 0.6uW, digital filter를 포함한 ADC 전체에서 6.25uW를 소모하며 BW 22KHz, SNDR 71dB, dynamic range 74.6dB을 달성하였다.

• 전력전자학회논문지
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• 제6권3호
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• pp.258-264
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• 2001

본 논문에서는 직접 보상전압 추출기법을 이용한 새로운 직렬형 능동전력필터의 제어법을 제안한다. 제안된 직렬형 능동전력필터는 비선형 부하를 갖는 3상 3선식 전력계통에 병렬 수동필터와 함께 사용되어 병렬 수동필터의 단점을 보완하고, 전원측 고조파 저감 효과를 극대화시키는데 기여한다. 제안된 제어법은 직렬형 능동전력필터의 보상전압을 성능함수에 의해 상변환 없이 직접 추출할 수 있다. 따라서 기존의 방법에 비해 연산시간이 짧고, 제어가 보다 간단하다. 실험결과는 제안된 제어법을 이용한 시스템이 고조파 저감에 우수한 성능을 나타냄을 입증한다.

• 대한기계학회논문집
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• 제18권5호
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• pp.1169-1181
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• 1994

Vibration isolation of mechanical systems, in general, is achieved through passive or active vibration isolators. Passive vibration isolator has an inherenrt performance limitation. Whereas, active vibration isolator provides significantly superior vibration-isolation performance at the cost of energy sources and sensors. Recently, in many cases, such as suspension system, precision machinery ... etc, active isolation system outweighs its limitation. Therefore, many studies, researches, and applications are carried out in this field. In this study, vibration-isolation characteristics of an active vibration control system using electromagnetic force actuator are investigated. Several control algorithms including optimal, feedforward are used for active vibration isolation. From the experimental results of each algorithm, effective control algorithms for this active vibration-isolation system are proposed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 I
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• pp.476-481
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• 2001

This research is concerned with development of the active vibration absorber using piezoelectric actuators. This active isolation system consists of a-pairs of PZT actuators bonded on a S-shaped aluminum plate and the passive damping material. The active system is connected to the passive system in series. In this paper, one of the popular control techniques which have been successfully applied to the smart structure is the Positive Position Feedback(PPF) control. The digital PPF control lows downloaded to the DSP chip and a main program, which runs SISO PPF algorithm. The structure and dynamic characteristics of the proposed active vibration isolation system and described in detail. To demonstate the effectiveness of the active vibration control, the PPF controller is first employed. Experimental results show that the active vibration isolation is possible by means of the proposed system.