• 대한의용생체공학회:의공학회지
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• 제28권2호
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• pp.258-264
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• 2007

Spatiotemporal changes of brain rhythmic activity at a certain frequency have been usually monitored in real time using scalp potential maps of multi-channel electroencephalography(EEG) or magnetic field maps of magnetoencephalography(MEG). In the present study, we investigate if it is possible to implement a real-time brain activity monitoring system which can monitor spatiotemporal changes of cortical rhythmic activity on a subject's cortical surface, neither on a sensor plane nor on a standard brain model, with a high temporal resolution. In the suggested system, a frequency domain inverse operator is preliminarily constructed, considering the individual subject's anatomical information, noise level, and sensor configurations. Spectral current power at each cortical vertex is then calculated for the Fourier transforms of successive sections of continuous data, when a single frequency or particular frequency band is given. An offline study which perfectly simulated the suggested system demonstrates that cortical rhythmic source changes can be monitored at the cortical level with a maximal delay time of about 200 ms, when 18 channel EEG data are analyzed under Pentium4 3.4GHz environment. Two sets of artifact-free, eye closed, resting EEG data acquired from a dementia patient and a normal male subject were used to show the feasibility of the suggested system. Factors influencing the computational delay are investigated and possible applications of the system are discussed as well.

• 디지털콘텐츠학회 논문지
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• 제19권8호
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• pp.1507-1514
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• 2018

본 논문에서는 1인용 스마트 전동휠체어의 보다 안전한 주행을 위한 지능형 통합 제어보드의 기능 개선 솔루션을 제안한다. 기존 국내 외의 전동휠체어 제품의 경우 안전 관련 기능 또는 장치가 포함되지 않은 경우가 많기 때문에 노약자 및 장애인이 지속적으로 증가하는 추세를 보이는 현 상황에서 전동휠체어가 관련된 사고의 발생 빈도 또한 지속적인 증가추이를 보이고 있다. 하지만 현재 상용되는 제품들에는 중고가형 이상의 전동휠체어에만 기본적인 완충작용 장치가 설치되어 있는 한계로 저가형의 제품에도 안전관련 기능이 필요한 실정이다. 따라서, 스마트 제어 플랫폼의 개발을 통해 전동휠체어 이동 중 사용자가 감지하지 못하는 장애물 또는 지형변화를 자동으로 감지 및 전동휠체어의 모터를 자동으로 제어함으로써 사용자가 안정적인 주행을 할 수 있도록 다양한 전동휠체어에 적용 가능한 스마트 전동휠체어 통합제어보드를 제시한다.

• 센서학회지
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• 제13권5호
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• pp.399-404
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• 2004

We report on the technology of formation of sandwich structures based on fullerite films and on experimental results in research of optical and conductivity properties of these sandwich samples. Single crystals of sapphire (100) or silicon were used as substrates. The sandwich specimens were based on the structure M/$C_{60}$/M (M=Cr, Pd, Ag, Al, Cu). The thickness of the fullerite films was about $0.2{\sim}1.0{\mu}m$. The area of the $C_{60}$ film under the top contact was about $1cm^{2}$. The specimens have been investigated by infrared spectroscopy, spectra-photometry, ellipsometry and X-ray diffraction analysis. Measurements of the current/voltage characteristics and research on the temperature dependence of conductivity were performed as well. It was shown that metals such as Cr, Pd, Ag, Al, and Cu penetrate easily into the fullerite films. It appears that these specimens have a large conductivity. For silver/$C_{60}$ and other sandwich structures the conductivities show a semiconductor-like behaviour.

• 제어로봇시스템학회논문지
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• 제17권2호
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• pp.93-101
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• 2011

For mobile robot, recognizing its current location is very important to navigate autonomously. Especially, loop closing detection that robot recognize location where it has visited before is a kernel problem to solve localization. A considerable amount of research has been conducted on loop closing detection and localization based on appearance because vision sensor has an advantage in terms of costs and various approaching methods to solve this problem. In case of scenes that consist of repeated structures like in corridors, perceptual aliasing in which, the two different locations are recognized as the same, occurs frequently. In this paper, we propose an improved method to recognize location in the scenes which have similar structures. We extracted salient regions from images using visual attention model and calculated weights using distinctive features in the salient region. It makes possible to emphasize unique features in the scene to classify similar-looking locations. In the results of corridor recognition experiments, proposed method showed improved recognition performance. It shows 78.2% in the accuracy of single floor corridor recognition and 71.5% for multi floor corridors recognition.

• 센서학회지
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• 제21권5호
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• pp.359-366
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• 2012

Nanopore DNA sequencing is an emerging and promising technique that can potentially realize the goal of a low-cost and high-throughput method for analyzing human genome. Especially, solid-state nanopores have relatively high mechanical stability, simple surface modification, and facile fabrication process without the need for labeling or amplification of PCR (polymerized chain reaction) in DNA sequencing. For these advantages of solid-sate nanopores, the use of solid-state nanopores has been extensively considered for developing a next generation DNA sequencing technology. Solid-state nanopore sequencing technique can determine and count charged molecules such as single-stranded DNA, double-stranded DNA, or RNA when they are driven to pass through a membrane nanopore between two electrolytes of cis-trans chambers with applied bias voltage by measuring the ionic current which varies due to the existence of the charged particles in the nanopore. Recently, many researchers have suggested that nanopore-based sensors can be competitive with other third-generation DNA sequencing technologies, and may be able to rapidly and reliably sequence the human genome for under $1,000.

• 조명전기설비학회논문지
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• 제19권5호
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• pp.54-59
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• 2005

브러시리스 직류 전동기(Brushless U Motor : BLDCM)는 기존의 직류 전동기의 단점인 브러시를 제거한 것으로 제어가 간단하면서도 넓은 범위에서 속도 제어가 가능하고 효율이 높으며 경제적으로 제어기 제작이 가능하여 산업용 뿐 아니라 가전에까지 널리 사용된다. 그러나 BLDCM을 구동하는데 필수적인 센서는 제품 가격을 증가시킬 뿐만 아니라 운전 환경이 열악한 곳에서는 동작 오류를 발생하는 원인이 되고 있다. 본 논문에서는 BLDCM의 센서리스 구동에서 정상상태 운전뿐만 아니라 안정된 초기 구동에 관한 연구를 수행한다. 정상상태 운전은 측정된 역기전력을 이용하여 회전자의 위치를 결정함으로써 이루어지며, 초기 구동을 개선하기 위해 환류 다이오드로부터 측정된 전류 신호를 이용하여 초기 구동을 하게 된다. 이것은 실험을 통해 타당성을 확인하였다.

• Smart Structures and Systems
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• 제7권5호
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• pp.365-378
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• 2011

Piezo-based active structural health monitoring (SHM) requires amplifiers specifically designed for capacitive loads. Moreover, with the increase in number of applications of wireless SHM systems, energy efficiency and cost reduction for this type of amplifiers is becoming a requirement. General lab grade amplifiers are big and costly, and not built for outdoor environments. Although some piezoceramic power amplifiers are available in the market, none of them are specifically targeting the wireless constraints and low power requirements. In this paper, a piezoceramic transducer amplifier for wireless active SHM systems has been designed. Power requirements are met by two digital On/Off switches that set the amplifier in a standby state when not in use. It provides a stable ${\pm}180$ Volts output with a bandwidth of 7k Hz using a single 12 V battery. Additionally, both voltage and current outputs are provided for feedback control, impedance check, or actuator damage verification. Vibration control tests of an aluminum beam were conducted in the University of Houston lab, while wireless active SHM tests of a wind turbine blade were performed in the Harbin Institute of Technology wind tunnel. The results showed that the developed amplifier provided equivalent results to commercial solutions in suppressing structural vibrations, and that it allows researchers to perform active wireless SHM on moving objects with no power wires from the grid.

• Current Applied Physics
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• 제18권11호
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• pp.1327-1337
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• 2018

This paper investigates the vibration behavior of pristine and defected triangular graphene sheets; which has recently attracted the attention of researchers and compare these two types in natural frequencies and sensitivity. Here, the molecular dynamics method has been employed to establish a virtual laboratory for this purpose. After measuring the different parameters obtained by the molecular dynamics approach, these data have been analyzed by using the frequency domain decomposition (FDD) method, and the dominant frequencies and mode shapes of the system have been extracted. By analyzing the vibration behaviors of pristine triangular graphene sheets in four cases (right angle of 45-90-45 configuration, right angle of 60-90-30 configuration, equilateral triangle and isosceles triangle), it has been demonstrated that the natural frequencies of these sheets are higher than the natural frequency of a square sheet, with the same number of atoms, by a minimum of 7.6% and maximum of 26.6%. Therefore, for increasing the resonance range of sensors based on 2D materials, nonrectangular structures, and especially the triangular structure, can be considered as viable candidates. Although the pristine and defective equilateral triangular sheets have the highest values of resonance, the sensitivity of defective (45,90,45) triangular sheet is more than other configurations and then, defective (45,90,45) sheet is the worst choice for sensor applications.

• Current Optics and Photonics
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• 제5권3호
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• pp.213-219
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• 2021

We describe a single-channel rubidium (Rb) radio-frequency atomic magnetometer (RFAM) as a receiver that takes magnetic signal resonating with Zeeman splitting of the ground state of Rb. We optimize the performance of the RFAM by recording the response signal and signal-to-noise ratio (SNR) in various parameters and obtain a noise level of 159 $fT{\sqrt{Hz}}$ around 30 kHz. When a resonant radiofrequency magnetic field with a peak amplitude of 8.0 nT is applied, the bandwidth and signal-to-noise ratio are about 650 Hz and 88 dB, respectively. It is a good agreement that RFAM using alkali atoms is suitable for receiving signals in the very low frequency (VLF) carrier band, ranging from 3 kHz to 30 kHz. This study shows the new capabilities of the RFAM in communications applications based on magnetic signals with the VLF carrier band. Such communication can be expected to expand the communication space by overcoming obstacles through the high magnetic sensitive RFAM.

• 한국산림과학회지
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• 제89권3호
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• pp.405-413
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• 2000

본 연구는 산림 기상 수문 환경의 모니터링을 위해 온도, 풍향, 풍속, 강우량, V노치의 수위, 계류수의 전기전도도 및 pH 등의 인자를 대상으로 하여 마이크로프로세서에 의한 전동식 센서유니트를 작동시켜 자동관측이 가능한 시스템을 개발하고자 실시하였으며, 그 결과는 다음과 같다. 1. 관측시스템은 크게 신호처리부, 전동식센서부, 전원제어부 그리고 무선데이터 통신부로 구성하였다. 2. 웨어부착형 전동식 센서유니트를 채택하여 계류수의 결빙 및 급류에 의한 센서의 파손을 방지하도록 하였으며, 동시에 항상 일정한 수위에서 측정이 이루어지도록 하였다. 3. 관측시스템에서 데이터의 전송은 무선 모뎀을 사용하여 산림유역의 수문 상황을 실시간 모니터링이 가능하도록 하였다. 4. 관측시스템은 각 기능별 독립구조의 모듈형태로 구성하여 측정 모듈의 수리, 교체, 추가 등의 변경이 가능하도록 하였다. 5. 관측시스템의 성능 시험을 실시한 결과 온도, EC, pH는 각각 최대 ${\pm}0.2^{\circ}C$, ${\pm}1{\mu}S$, ${\pm}0.1pH$의 오차범위 내에서 관측되었다. 6. 현장에서 관측시스템을 시험 운영해 본 결과 장기적이고 안정적인 산림 수문 수질 인자의 측정이 가능할 것으로 평가되었다.