• 디지털콘텐츠학회 논문지
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• 제18권5호
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• pp.895-904
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• 2017

본 논문에서는 1인 가구를 대상으로 전기 안전, 전기 에너지 소비 관리 그리고 비상시 네트워크를 연결하여 예약된 연락처에 메시지를 전송하는 사물인터넷 기반의 스마트 콘센트 시스템 구축 방식을 제안한다. 제안된 스마트 콘센트 시스템은 서버와 모듈, 어플리케이션, WiFi AP 수신기 사이에 패킷 데이터와 프로토콜을 파싱하여 구현된다. 통신을 위해 구축된 WiFi AP는 콘센트 뿐 만 아니라 가스 차단, 도어락 등에 연결하여 사용하는 것이 가능하다. 또한 제안된 방식은 AC 전류센서(SCT-013)를 통해 받아온 해당 콘센트의 전력량을 실시간으로 수신하여 원격 모니터링 기능을 제공할 수 있다. 스마트 콘센트 시스템은 대기전력 차단 기능과 더불어 전력 사용 자동 분석을 통해 비상시 전력 자동 차단 기능까지 할 수 있을 것으로 기대한다.

• Structural Monitoring and Maintenance
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• 제2권4호
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• pp.319-338
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• 2015

The electro-mechanical impedance (EMI) technique makes use of surface-bonded lead zirconate titanate (PZT) patches as impedance transducers measuring impedance variations monitored on host structural components. The present experimental work further evaluate an alternative to the conventional EMI technique which performs measurements of the variations in the output voltage of PZT transducers rather than computing electromechanical impedance (or admittance) itself. This paper further evaluates a variant of the EMI approach presented in a previous work of the present authors, suitable, for low-cost concrete structures monitoring applications making use of a credit card-sized Raspberry Pi single board computer as core hardware unit. This monitoring approach is also deployed by introducing a new damage identification index based on the ratio between the area of the 2-D error ellipse of specific probability of EMI-based measurements containment over that of the 2-D error circle of equivalent probability. Experimental results of damages occurring in concrete cubic and beam specimens are investigated under increasing loading conditions. Results illustrate that the proposed technique is an efficient approach for identification and early detection of damage in concrete structures.

• Smart Structures and Systems
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• 제25권1호
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• pp.57-64
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• 2020

The nonlinear dynamics of a directly forced clamped-clamped-free-free magneto-rheological elastomer (MRE) sandwich shell has been experimentally investigated. Experiments have been conducted on an aluminium shallow shell (shell A) and an MRE-aluminium sandwich shallow shell with single curvature (shell B). An electrodynamic shaker has been used to directly force shells A and B in the vicinity of their fundamental resonance frequency; a laser displacement sensor has been used to measure the vibration amplitude to construct the frequency-response curves. It was observed that for an aluminium shell (shell A), that at small forcing amplitudes, a weak softening-type nonlinear behaviour was observed, however, at higher forcing amplitudes the nonlinear dynamical behaviour shifted and a strong hardening-type response occurred. For the MRE shell (shell B), the effect of forcing amplitude showed softening at low magnetic fields and hardening for medium magnetic fields; it was also observed the mono-curved MRE sandwich shell changed dynamics to quasiperiodic displacement at some frequencies, from a periodic displacement. The presence of a magnetic field, initial curvature, and forcing amplitude has significant qualitative and quantitative effects on the nonlinear dynamical response of a mono curved MRE sandwich shell.

• 제어로봇시스템학회논문지
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• 제12권9호
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• pp.926-934
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• 2006

This paper proposes intelligent control of a virtual walking machine that can generate infinite floor for various surfaces and can provide proprioceptive feedback of walking to a user. This machine allows users to participate in a life-like walking experience in virtual environments with various terrains. The controller of the machine is implemented hierarchically, at low-level for robust actuator control, at mid-level fur platform control to compensate the external forces by foot contact, and at high-level control for generating walking trajectory. The high level controller is suggested to generate continuous walking on an infinite floor for various terrains. For the high level control, each independent platform follows a man foot during the swing phase, while the other platform moves back during single stance phase. During double limb support, two platforms manipulate neutral positions to compensate the offset errors generated by velocity changes. This control can, therefore, satisfy natural walking conditions in any direction. Transition phase between the swing and the stance phases is detected by using simple switch sensor system, while human foot motions are sensed by careful calibration with a magnetic motion tracker attached to the shoe. Experimental results of walking simulations at level ground, slope, and stairs, show that with the proposed machine, a general person can walk naturally on various terrains with safety and without any considerable disturbances. This interface can be applied to various areas such as VR navigations, rehabilitation, and gait analysis.

• 한국자기학회지
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• 제21권4호
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• pp.132-135
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• 2011

초연자성을 갖는 코네틱(NiFeCuMo) 박막을 NiFe 박막 사이에 삽입한 삼층박막 위에 반강자성체 FeMn을 증착한 다층박막에서 NiFe와 NiFeCuMo 박막의 두께에 따른 교환결합력과 보자력에 관한 특성을 조사하였다. 특히 NiFeCuMo 박막의 두께가 1 nm일 때 NiFe 박막 사이에 삽입한 삼층박막 위에 반강자성체 FeMn을 증착한 다층박막의 교환결합력은 최댓값을 나타내었다. 고정층과 자유층에 각각 NiFeCuMo 박막을 삽입하여 초연자성의 바이오센서용 거대자기저항-스핀밸브(giant magnetoresistive-spin valves; GMR-SV) 소자를 개발할 수 있는 가능성을 보여주었다.

• Journal of Electrical Engineering and Technology
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• 제3권2호
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• pp.224-234
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• 2008

Multi-phase machines can be used in variable speed drives. Their applications include electric ship propulsion, 'more-electric aircraft' and traction applications, electric vehicles, and hybrid electric vehicles. Multi-phase machines enable independent control of a few numbers of machines that are connected in series in a particular manner with their supply being fed from a single voltage source inverter(VSI). The idea was first implemented for a five-phase series-connected two-motor drive system, but is now applicable to any number of phases more than or equal to five-phase. The number of series-connected machines is a function of the phase number of VSI. Theoretical and simulation studies have already been reported for number of multi-phase multi-motor drive configurations of series-connection type. Variable speed induction motor drives without mechanical speed sensors at the motor shaft have the attractions of low cost and high reliability. To replace the sensor, information concerning the rotor speed is extracted from measured stator currents and voltages at motor terminals. Open-loop estimators or closed-loop observers are used for this purpose. They differ with respect to accuracy, robustness, and sensitivity against model parameter variations. This paper analyses operation of an MRAS estimator based sensorless control of a vector controlled series-connected two-motor five-phase drive system with current control in the stationary reference frame. Results, obtained with fixed-voltage, fixed-frequency supply, and hysteresis current control are presented for various operating conditions on the basis of simulation results. The purpose of this paper is to report the first ever simulation results on a sensorless control of a five-phase two-motor series-connected drive system. The operating principle is given followed by a description of the sensorless technique.

• 한국통신학회논문지
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• 제41권1호
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• pp.12-22
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• 2016

운전자의 편의와 안전을 위한 자율 주행 자동차 시스템으로 레이더 시스템이 활발히 연구가 진행되고 있다. 레이더 시스템은 전방 차량의 거리, 속도 그리고 각도를 추정한다. 도로 환경에 차량뿐만 아니라 인식해야 할 다양한 요소들이 다양해짐에 따라 고해상도 각도 추정 알고리즘이 적용되고 있다. 기존의 방식으로는 클러터들 사이에서 전방의 차량만의 각도를 추정하기 어렵고, 특히 같은 각도 상에 놓인 다른 차량들을 구분하기 힘들다. FMCW 레이더 시스템에서는 거리와 속도가 다른 차량들이 서로 다른 비트 주파수를 가지기 때문에, 비트 주파수에 기반하여 각도 추정을 할 수 있다면 효율적인 시스템을 구축할 수 있다. 본 논문에서는 MUSIC 알고리즘을 주파수 영역에서 적용하는 방법을 제시하고 적합성에 대한 분석을 한다.

• Journal of Information Processing Systems
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• 제10권1호
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• pp.1-22
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• 2014

Recent technological advances provide the opportunity to use large amounts of multimedia data from a multitude of sensors with different modalities (e.g., video, text) for the detection and characterization of criminal activity. Their integration can compensate for sensor and modality deficiencies by using data from other available sensors and modalities. However, building such an integrated system at the scale of neighborhood and cities is challenging due to the large amount of data to be considered and the need to ensure a short response time to potential criminal activity. In this paper, we present a system that enables multi-modal data collection at scale and automates the detection of events of interest for the surveillance and reconnaissance of criminal activity. The proposed system showcases novel analytical tools that fuse multimedia data streams to automatically detect and identify specific criminal events and activities. More specifically, the system detects and analyzes series of incidents (an incident is an occurrence or artifact relevant to a criminal activity extracted from a single media stream) in the spatiotemporal domain to extract events (actual instances of criminal events) while cross-referencing multimodal media streams and incidents in time and space to provide a comprehensive view to a human operator while avoiding information overload. We present several case studies that demonstrate how the proposed system can provide law enforcement personnel with forensic and real time tools to identify and track potential criminal activity.

• 센서학회지
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• 제24권6호
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• pp.364-367
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• 2015

Tin oxide thin films were fabricated on glass substrates by the successive ionic layer adsorption and reaction (SILAR) method at room temperature and ambient pressure. Before measuring their properties, all samples were annealed at $500^{\circ}C$ for 2 h in air. Film thickness increased with the number of cycles; X-ray diffraction patterns for the annealed $SnO_2$ thin films indicated a $SnO_2$ single phase. Thickness of the $SnO_2$ films increased from 12 to 50 nm as the number of cycles increased from 20 to 60. Although the optical transmittance decreased with thickness, 50 nm $SnO_2$ thin films exhibited a high value of more than 85%. Regarding electronic properties, sheet resistance of the films decreased as thickness increased; however, the measured resistivity of the thin film was nearly constant with thickness ($3{\times}10^{-4}ohm/cm$). From Hall measurements, the 50 nm thickness $SnO_2$ thin film had the highest mobility of the samples ($8.6cm^2/(V{\cdot}s)$). In conclusion, optical and electronic properties of $SnO_2$ thin films could be controlled by adjusting the number of SILAR cycles.

• 센서학회지
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• 제20권2호
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• pp.124-130
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• 2011

In this study, in order to evaluate the yield of bubble by ultrasonic cavitation in HIFU sonication, the bubble image analysis was performed. The changing phenomenon of cavitation effect according to the sonication condition was discussed by analyzing the bubble image. Especially the appearance of bubble cloud, the size of micro-bubble, and the yield of bubble were considered. The 500 KHz and 1.1 MHz concave type ultrasonic transducers were used for HIFU sonication. Computer controlled digital camera was used to obtain the bubble image, and the binary image processing(binarization coefficient : 0.15) was performed to analyze them. In results of 500 KHz and 1.1 MHz transducer, the area of bubble cloud was increased in proportion to the rise in sonication intensity($R^2$ : 0.7031 and 0.811). The mean size of single microbubble was measured as 98.18 um in 500 KHz sonication, and 63.38 um in 1.1 MHz sonication. In addition, the amount of produced bubble was increased in proportion to sonication intensity. Through the result of this study and further study for variable image processing method, the quantitative evaluation of ultrasonic cavitation effects in HIFU operation could be possible with the linearity associated with the sonication conditions.