• Environmental Analysis Health and Toxicology
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• v.14 no.4
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• pp.175-187
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• 1999

To investigate the risk perception of environmental issues, two consequtive surveys were conducted to environmental professionals using a standardized questionnaire from September to October in 1999. The number of subjects were 72 for the first survey and 68 for the second one. The questionnaire was consisted of items such as the degree of environmental pollution in Korea, risk perception of some issues on human health and ecosystem, and seriousness of the problems in the real situation in Korea. For the degree of environmental pollution in Korea, the average risk rating in the second test (7.4 point) was significantly higher than that in the first test (7.2 point). The risk perception on the general human health and ecosystem, and the seriousness in Korea situation were analyzed in the order of ′air pollution′, ′water pollution′,′soil contamination′,′waste′,′toxic chemical pollutants′,′food contamination′,′ocean contamination′, ′odor pollution′, and ′noise pollution′. Also ′toxic chemical pollutants′ problem was perceived to be the highest risk on general human health or ecosystem, and on present situation in Korea. ′Automotive vehicle exhaust′ problem was perceived to be the most severe environmental problems among specific 30 items. ′Industrial source air pollution′,′toxic air pollutants′, and ′domestic and industrial source pollutants to surface water′ were relatively severe environmental problems comparing to other problems. The pollution issues were classified into four categories by two aspects of perception; risk in general setting and seriousness in Korea situation. If the issues were highly serious in Korea and low risk perception in general setting then it is named "the Korea-specific group". Those that were all high score in two aspects, named "the Common group". Those that were all low in two aspects, named "the Nonsignificant group". And the issues were high risk perception in general setting and low seriousness in Korean situation, named "the Latent group".

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.6
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• pp.244-251
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• 2014

In this study, we give a detailed account of normal and abnormal state of GIS(Gas Insulated Switch-gear) using the preventive diagnostic technology. And it is based on the analysis and diagnosis for storing data of GIS by intelligent GIS monitoring system. The wave shape of GIS sound is similar to noise and is systematically generated by discharge and its corona sound. Therefore, in this paper, to classify normal and abnormal GIS sound. We could discriminate between normal and abnormal case using level crossing rate(LCR) and spectrogram energy rate.

• Tribology and Lubricants
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• v.32 no.4
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• pp.113-118
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• 2016

As an economic, high quality, and highly reliable gear with low noise and low vibration is demanded, an overall finite element analysis regarding a gear is required. Also, an infrared thermography test, which is a quantitative testing technique, is demanded for safety and longer lifespan of gear products. In order to manufacture a gear product or to determine safety of a gear being used, it is necessary to precisely determine ingredients of a material constituting a gear and detect any internal defect. This study aims to realize a design that minimizes the spur gear displacement with respect to power during its rotation and ensures the spur gear control capacity by using a 3D model and the midasNFX program. This facilitates the assessment of the possibility of cracking by evaluating the stress intensity and focusing on the integrity of the spur gear. We prepare the specimen of the spur gear based on the possibility of cranking as per the result of the structural interpretation from an infrared ray thermal measuring technique. After cooling the spur gear, we perform experiments using thermography and halogen lamps and analyze the temperature data according to the results of the experiment. In the experiment which we use thermography after cooling, we find a rise in the temperature of the room. As a result, the defective part show temperatures lower than their surroundings while the normal parts have temperatures higher than the defective parts. Therefore, it possible to precisely identify defective part owing to its low temperature.

• Journal of the Korean Magnetics Society
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• v.23 no.2
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• pp.68-76
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• 2013

Currently, wireless power transmission technology based on magnetic induction was employed in battery charger for smart phone application. The system consists of wireless power transmitter in base station and receiver in smart phone. Size and thickness of receiver was strictly limited in the newest smart phone. In order to achieve high efficiency of a tiny small wireless power receiver module, sub-millimeter thick electromagnetic wave shielding sheet having high permeability and Q was essential component. It was found that magnetic field from transmitter to receiver can be intensified by sufficient shielding cause to minimize leakage magnetic flux by those magnetic properties. This leads to high efficiency of wireless power transmission and protects crucial integrated circuit of main board from electromagnetic noise. The important soft magnetic materials were introduced and summarized for the current small-power wireless power charger and NFC application and mid-power home appliance and high-power automotive application in the near future.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.11
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• pp.1297-1306
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• 2012

This work presents a 77 GHz radar transmitter for the automotive radar system. An integrated 13 GHz frequency synthesizer fabricated using 130 nm RF CMOS process drives a commercial W-band compound semiconductor monolithic multifunction amplifier(MPA), which includes a frequency multiplier by six to generate 77 GHz transmitting signal. The 13 GHz frequency synthesizer includes a high efficiency injection buffer of 4 dBm output power to drive the MPA. The output power of 77 GHz radar transmitter is higher than 13.99 dBm and the magnitude of the reference spur relative to the carrier is -36.45 dBc. The phase noise is -81 dBc/Hz at 1 MHz offset frequency from the carrier.

• Journal of the Korean Institute of Gas
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• v.11 no.4
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• pp.47-53
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• 2007

The safe operation of high pressure pipe line systems is of significant importance. Leaks due to faulty operation from the pipelines can lead to considerable product losses and to exposure of community to dangerous gases. There are several leak detection methods, which have been recently suggested on pipeline network. The negative pressure wave detection technology, which has advantages of short time detection availability, accurate leaking location estimate capability and cost effective, is concentrated in this study. Theoretical analysis of the flow characteristics for leaking through a hole on the pipe wall has been performed by using CFD++, commercial CFD package. The results of 3-dimensional analysis near leaking hole confirm the occurrence of negative pressure wave and verify the characteristics of propagation of the wave which travels with speed equal to the speed of sound in the pipeline contents. For the application of long pipe line system. The method of 1-dimensional analysis has been suggested and verified with results of CFD++.

• Composites Research
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• v.29 no.1
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• pp.7-15
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• 2016

The quality of polymeric automotive parts depends highly on an injection molding process, which causes various defects, such as warpage, sink marks, weld lines, shrinkage, residual stress, etc. This study is to determine the optimum processing parameters, such as packing pressure, mold temperature, melting temperature, and packing time for the manufacture of polycarbonate buttons in cars on the basis of FEM, the Taguchi method, and analysis of variance (ANOVA). As a result, the optimum processing parameters of buttons made of polycarbonate material were obtained as follows: 140 MPa of packing pressure, $105^{\circ}C$ of mold temperature, $292.5^{\circ}C$ of melting temperature and 1 second of packing time. A gain of S/N (signal to noise) ratio, 10.2, was obtained with the optimum values. Moreover, the melting temperature was found to be the most significant factor followed by the mold temperature.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.6
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• pp.224-231
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• 2016

When aiming to reduce the low frequency noise of a subway guest room through sound absorbing treatment methods inside the wall of a tunnel the resonator is often more effective than a porous sound absorbing material. Therefore, the perforated panel type resonator embedded with a perforated panel is proposed. The perforated panel is installed in the neck, which is then extended into the resonator cavity so that it can ensure useful volume. The absorption performance of the perforated panel type of resonator is obtained by acoustic analysis and experiment. The analytical results are in good agreement with the experimental results. In the case of multiple perforated panel type resonators, as the number of perforated panels increase, the 1st resonance frequency is moved to a low frequency band and sound absorption bandwidth is extended on the whole. In order to obtain excellent absorption performance, the impedance matching between multi-panels should be considered. When the perforated panel in the resonator is combined with a porous material, the absorption performance is highly enhanced in the anti-resonance and high frequency range. In case of the resonator inserted with perforated panels of 2, the 2nd resonance frequency is shifted to a low frequency band in proportion to the distance between perforated panels.

• BioChip Journal
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• v.12 no.4
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• pp.332-339
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• 2018

The future neuro-prosthetic devices would be required spikes data monitoring through sub-nanoscale transistors that enables to neuroscientists and clinicals for scalable, wireless and implantable applications. This research investigates the spikes monitoring through integrated CNT front-end amplifier for neuro-prosthetic diagnosis. The proposed carbon nanotube-based architecture consists of front-end amplifier (FEA), integrate fire neuron and pseudo resistor technique that observed high electrical performance through neural activity. A pseudo resistor technique ensures large input impedance for integrated FEA by compensating the input leakage current. While carbon nanotube based FEA provides low-voltage operation with directly impacts on the power consumption and also give detector size that demonstrates fidelity of the neural signals. The observed neural activity shows amplitude of spiking in terms of action potential up to $80{\mu}V$ while local field potentials up to 40 mV by using proposed architecture. This fully integrated architecture is implemented in Analog cadence virtuoso using design kit of CNT process. The fabricated chip consumes less power consumption of $2{\mu}W$ under the supply voltage of 0.7 V. The experimental and simulated results of the integrated FEA achieves $60G{\Omega}$ of input impedance and input referred noise of $8.5nv/{\sqrt{Hz}}$ over the wide bandwidth. Moreover, measured gain of the amplifier achieves 75 dB midband from range of 1 KHz to 35 KHz. The proposed research provides refreshing neural recording data through nanotube integrated circuit and which could be beneficial for the next generation neuroscientists.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.2
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• pp.143-149
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• 2021

BLDC motors are getting better performance due to the improvement of material technology including high performance of permanent magnets, advancement of driving IC technology with high integration and high functionality, and improvement of assembly technology such as high point ratio. While having the advantage of such a square wave driven BLDC motor, interest in the design and development of a square wave driven BLDC permanent magnet motor and development of a position detection circuit and driver is increasing in order to more meet the needs of users. However, in spite of the cost and functional advantages due to reduced efficiency, switching loss and vibration, noise, etc., the application is somewhat limited. Therefore, in this paper, we study a position detection circuit that generates a sinusoidal signal in proportion to the magnetic flux of a BLDC motor rotor using a Hall Effect Sensor that generates a sinusoidal wave to increase the efficiency of the motor, reduce ripple, and drive a sinusoidal current with excellent speed and torque characteristics.