• Journal of rehabilitation welfare engineering & assistive technology
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• v.11 no.1
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• pp.45-52
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• 2017

EEG signals that are the same as those that have the same disabled people. So, the EEG signals are becoming the next generation. In this paper, we propose an internet of things system that controls the indoor environment using EEG signal. The proposed system consists EEG measurement device, EEG simulation software and indoor environment control device. We use data as EEG signal data on emotional imagination condition in a comfortable state and logical imagination condition in concentrated state. The noise of measured signal is removed by the ICA algorithm and beta waves are extracted from it. then, it goes through learning and test process using SVM. The subjects were trained to improve the EEG signal accuracy through the EEG simulation software and the average accuracy were 87.69%. The EEG signal from the EEG measurement device is transmitted to the EEG simulation software through the serial communication. then the control command is generated by classifying emotional imagination condition and logical imagination condition. The generated control command is transmitted to the indoor environment control device through the Zigbee communication. In case of the emotional imagination condition, the soft lighting and classical music are outputted. In the logical imagination condition, the learning white noise and bright lighting are outputted. The proposed system can be applied to software and device control based BCI.

• Journal of Broadcast Engineering
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• v.14 no.5
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• pp.573-588
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• 2009

In this paper, we propose a novel video quality degradation monitoring scheme titled VR-VQMS(Visual Rhythm based Video Quality Monitoring Scheme) over an IPTV service prone to packet losses during network transmission. Proposed scheme quantifies the amount of quality degradation due to packet losses, and can be classified into a RR(reduced-reference) based quality measurement scheme exploiting visual rhythm data of H.264-encoded video frames at a media server and reconstructed ones at an Set-top Box as feature information. Two scenarios, On-line and Off-line VR-VQMS, are proposed as the practical solutions. We define the NPSNR(Networked Peak-to-peak Signal-to-Noise Ratio) modified by the well-known PSNR as a new objective quality metric, and several additional objective and subjective metrics based on it to obtain the statistics on timing, duration, occurrence, and amount of quality degradation. Simulation results show that the proposed method closely approximates the results from 2D video frames and gives good estimation of subjective quality(i.e.,MOS(mean opinion score)) performed by 10 test observers. We expect that the proposed scheme can play a role as a practical solution to monitor the video quality experienced by individual customers in a commercial IPTV service, and be implemented as a small and light agent program running on a resource-limited set-top box.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1991.04a
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• pp.75-79
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• 1991

고도로 산업화가 진행됨에 따라 회전기계는 더욱 중요시되고 있으며 이의 성능 향상에 부단한 노력이 경주되고 있다. 특히 우주 시대의 개막과 더불어 우주선 및 인공위성에 사용하기 위해 초소형이며 초고속의 고성능회전모타 를 개발하기에 이르렀다. 한 예로서 미국립항공우주국(NASA)의 스페이스셔 틀에 사용되는 주엔진 터보펌프를 들 수 있는데 이 터보펌프는 접시만한 크 기로써 71000마력을 생성해 낸다. 이러한 가공할 만한 에너지 밀도와 유량을 감당해 내려면 종래의 회전기계보다는 훨씬 더 높은 회전속도를 가져야 한 다. 이러한 회전체는 큰 관성부하와 진 동 및 동안정성의 문제등을 내포하고 있다. 고성능 회전기계의 또다른 예로서 초정밀 가공용 공작기계를 들 수 있 다. 선반 혹은 밀링머신으로 초정밀가공을 행하기 위해서는 회전축의 진동이 극히 작아야 한다. 이와 같이 오늘날 갈수록 초고성능 초정밀도를 추구함에 있어서 회전축의 진동을 현장에서 모니터링하고 이 진동데이터를 분석하여 회전축을 제어하는 것이 강력히 요구되어진다. 따라서 in-situ 측정이 중요성 을 띠게 되었는데 이는 제어기술의 바탕이 되는 자료를 현장에서 제공할 수 있기 때문이다. 회전축 진동측정의 대상이 되는 것들은 모타, 발전기, 엔진 및 터빈등을 대표적으로 들 수가 있다. 여기서 소형회전기계의 축표면과 같 이 비교적 곡면을 이루고 있는 부분의 진동변위 측정에 신중한 고려가 요구 되어 진다. 이는 축의 곡면도에 따라 감도가 변화하기 때문이다. 따라서 평 판에 대한 calibration 챠트를 회전기계축진동 변위환상에 이용하면 곡률에 따라서 오차가 생기게 된다. 본 연구에서는 비접촉 축진동측정시 발생되는 오차에 대하여 검토하고자 한다. from the studies, the origin of ${\alpha}$$_1$peak was attributed to the detrapping process form trap with 2.88[eV] deep of injected space charge from the chathode in the crystaline regions. The origin of ${\alpha}$$_2$ peak was regarded as the detrapping process of ions trapped with 0.9[eV] deep originated from impurity-ion remained in the specimen during production process of the material, in the crystalline regions. The origin of ${\beta}$ peak was concluded to be due to the depolarization process of "C=0"dipole with the activation energy of 0.75[eV] in the amorphous regions. The origin of ${\gamma}$ peak was responsible to the process combined with the depolarization of "CH$_3$", chain segment, with the activation energy of carriers from the shallow trap with 0.

• Progress in Medical Physics
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• v.19 no.4
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• pp.201-208
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• 2008

Physical evaluations provide the basis for an objective and quantitative analysis of the image quality. Nonetheless, there are limitations in using physical evaluations to judge the utility of the image quality if the observer's subjectivity plays a key role despite its imprecise and variable nature. This study proposes a new method for objective and quantitative evaluation of image quality to compensate for the demerits of both physical and subjective image quality and combine the merits of them. The images of chest phantom were acquired from four digital radiography systems on clinic sites. The physical image quality was derived from an image analysis algorithm in terms of the contrast-to-noise ratio (CNR) of the low-contrast objects in three regions (lung, heart, and diaphragm) of a digital chest phantom radiograph. For image analysis, various image processing techniques were used such as segmentation, and registration, etc. The subjective image quality was assessed by the ability of the human observer to detect low-contrast objects. Fuzzy integral was used to integrate them. The findings of this study showed that the physical evaluation did not agree with the subjective evaluation. The system with the better performance in physical measurement showed the worse result in subjective evaluation compared to the other system. The proposed protocol is an integral evaluation method of image quality, which includes the properties of both physical and subjective measurement. It may be used as a useful tool in image evaluation of various modalities.

• Journal of Biomedical Engineering Research
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• v.25 no.4
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• pp.269-275
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• 2004

Different biological tissues have different values of electrical resistivity. In EIT (electrical impedance tomography), we try to provide cross-sectional images of a resistivity distribution inside an electrically conducting subject such as the human body mainly for functional imaging. However, it is well known that the image reconstruction problem in EIT is ill-posed and the quality of a reconstructed image highly depends on the measurement error. This requires us to develop a high-performance EIT system. In this paper, we describe the development of a 16-channel digital EIT system including a single constant current source, 16 voltmeters, main controller, and PC. The system was designed and implemented using the FPGA-based digital technology. The current source injects 50KHz sinusoidal current with the THD (total harmonic distortion) of 0.0029% and amplitude stability of 0.022%. The single current source and switching circuit reduce the measurement error associated with imperfect matching of multiple current sources at the expense of a reduced data acquisition time. The digital voltmeter measuring the induced boundary voltage consists of a differential amplifier, ADC, and FPGA (field programmable gate array). The digital phase-sensitive demodulation technique was implemented in the voltmeter to maximize the SNR (signal-to-noise ratio). Experimental results of 16-channel digital voltmeters showed the SNR of 90dB. We used the developed EIT system to reconstruct resistivity images of a saline phantom containing banana objects. Based on the results, we suggest future improvements for a 64-channel muff-frequency EIT system for three-dimensional dynamic imaging of bio-impedance distributions inside the human body.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.3
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• pp.376-383
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• 2008

Generally a return current plane(RCP) of high speed digital and analog part is partitioned. This is achieved in order to decrease the noise interference between subsystem in PCBs(Printed Circuit Boards). However, when the connected signal line exists between each subsystem, this partition will cause unwanted effects. In a EMI(Electromagnetic Interference) point of view, the partition of the return current plane becomes a primary factor to increase the radiated emission. Component bridge(CB) is used for the way of maintaining radiated emission, still specific user's guide doesn't give sufficient principle. In a view point of EMI, design principle of multi-CB using method will be analyzed by measurement. And design principle of noise mitigation will be provided. Generally interval of multi-CB is ${\lambda}/20$ ferrite bead. In this study, When multi-CB connection is applied, design principle of ferrite bead and chip resistor is proved by measurement. Multi-connected chip resistance$(0{\Omega})$ is proved to be more effective design method in the point of EMI.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.3
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• pp.366-375
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• 2008

Generally a return current plane(RCP) of high speed digital and analog part is partitioned. This is achieved in order to decrease the noise interference between subsystem in PCBs(Printed Circuit Boards). However, when the connected signal line exists between each sub system, this partition will cause unwanted effects. In a circuital point of view, RCP partition has a bad influence upon signal integrity. In a EMI(Electromagnetic Interference) point of view, the partition of the return current plane becomes a primary factor to increase the radiated emission. Component bridge(CB) is usecl for the way of maintaining signal integrity, still specific user's guide doesn't give sufficient principle. In a view point of signal integrity, design principle of multi-CB using method will be analyzed by measurement and simulation. And design principle of noise mitigation will be provided. Generally interval of CB is ${\lambda}/20$ ferrite bead. In this study. When multi-CB connection is applied, design principle of ferrite bead and chip resistor is proved by measurement and simulation. Multi-connected chip resistance$(0{\Omega})$ is proved to be more effective design method in the point of signal integrity.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.16 no.2
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• pp.131-144
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• 2006

For the purpose of preparing the fundamental data on working environment of small scale manufacturing industries and preventing the occupational diseases of workers in these industries, authors surveyed the status of working environment to several chemical substances and physical agents by types of industry and types of process in the small scale manufacturing industries with less than five workers in Gimhae including 235 workplaces, 14 types of industry and 25 types of process from January 2002 to December 2004. This measurement method was work environment measurement method (established in Ministry of Labor, Korea), analytical methods (2nd Ed.) of Occupational Safety and Health Administration (OSHA) and manual of analytical methods (4th Ed.) of National Institute for Occupational Safety and Health (NIOSH) and collected data was analyzed by using SPSS 10.0 for windows, the results were as follows: 1. Noise generated in 14 types of industry and 22 types of process. an actual level of mean exposure (90.7 dB(A)) exceeded threshold limit values (TLVs) in manufacture of other transport equipment. An actual level of mean exposure (90.2dB) exceeded TLVs in the process of wire-drawing and 90.4dB in the process of wire-stranding. 2. Dusts of type I, II, III were generated in 9 types of industry and 8 types of process. Its mean concentration did not exceed TLVs. 3. Heavy metals (Pb, Mn, Cr, Ni) were generated in 7 types of industry and 7 types of process. Its mean concentration did not exceed TLVs. 4. 16 kinds of organic solvents were generated in 11 types of industry and 6 types of process. Its mean concentration did not exceed TLVs. As the above results, chemical substances and physical agents were generated in the several different types of industry and process of the manufacturing industry with less than five workers, and only mean level of noise was exceeded TLVs. In case of exceeding threshold limit values, improvement of work environment is actively needed, and work environment management should be performed continuously for prevention of an occupational diseases and work related diseases.

• The Journal of the Acoustical Society of Korea
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• v.33 no.2
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• pp.87-93
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• 2014

If one identifies the detailed distribution of pressure and axial velocity at a source plane, the position and strength of major noise sources can be known, and the propagation characteristics in axial direction can be well understood to be used for the low noise design. Conventional techniques are usually limited in considering the constant source characteristics specified on the whole source surface; then, the source activity cannot be known in detail. In this work, a method to estimate the pressure and velocity field distribution on the source surface with high spatial resolution is studied. The matrix formulation including the evanescent modes is given, and the nearfield measurement method is proposed. Validation experiment is conducted on a wide duct system, at which a part of the source plane is excited by an acoustic driver in the absence of airflow. Increasing the number of evanescent modes, the prediction of pressure spectrum becomes further precise, and it has less than -25 dB error with 26 converged evanescent modes within the Helmholtz number range of interest. By using the converged modal amplitudes, the source parameter distribution is restored, and the position of the driver is clearly identified at kR = 1. By applying the regularization technique to the restored result, the unphysical minor peaks at the source plane can be effectively suppressed with the filtering of the over-estimated pure radial modes.

• Journal of IKEEE
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• v.14 no.2
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• pp.16-23
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• 2010

Since the interest of a brain science research is increased recently, various devices using brain waves have been developed in the field of brain training game, education application and brain computer interface. In this paper, we have developed a portable EEG measurement and a bluetooth based wireless transmission device measuring brain waves from the frontal lob simply and conveniently. The low brain signals about 10~100${\mu}V$ was amplified into several volts and low pass, high pass and notch filter were designed for eliminating unwanted noise and 60Hz power noise. Also, PIC24F192 microcontroller has been used to convert analog brain signal into digital signal and transmit the signal into personal computer wirelessly. The sampling rate of 1KHz and bluetooth based wireless transmission with 38,400bps were used. The LabVIEW programing was used to receive and monitor the brain signals. The power spectrum of commercial biopac MP100 and that of a developed EEG system was compared for performance verification after the simulation signals of sine waves of $1{\mu}V$, 0~200Hz was inputed and processed by FFT transformation. As a result of comparison, the developed system showed good performance because frequency response of a developed system was similar to that of a commercial biopac MP100 inside the range of 30Hz specially.