• Journal of the Korean Vacuum Society
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• v.21 no.5
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• pp.264-272
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• 2012

In this paper, we report THz generation and detection characteristics investigated by InGaAs semiconductor epilayers, as results of a basic study obtained from the InGaAs-based THz transmitter/receiver (Tx/Rx). High-temperature and low-temperature (LT) grown InGaAs epilayers were prepared by the molecular beam epitaxy technique for the characterization of THz generation and detection, respectively, and the surface emission based on the photo-Dember effect was tried for THz generation. THz wave was generated by irradiation of a Ti:Sapphire fs pulse laser (60 ps/83 MHz), and a LT-GaAs Rx was used for the THz detection. The frequency band shown in the spectral amplitudes Fourier-transformed from the measured current signals was ranging in 0.5~2 THz, and the signal currents were exponentially increased with the Tx beam power. The THz detection characteristics of LT-InGaAs were investigated by using an Rx with dipole (5/20 ${\mu}m$) antenna, and the cutoff frequency was ~2 THz.

• The Journal of the Acoustical Society of Korea
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• v.22 no.2
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• pp.121-128
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• 2003

Acoustic Echo Cancellation(m) is very active research topic having many applications like teleconference and hands-free communication and it employs Double Talk Detector(DTD) to indicate whether the near-end speaker is active or not. However. the DTD is very sensitive to the variation of acoustical environment and it sometimes provides wrong information about the near-end speaker. In this paper, we are focusing on the development of robust DTD algorithm which is a basic building block for reliable AEC system. The proposed AEC system consists of delayless subband AEC and narrow-band DTD. Delayless subband AEC has proven to have excellent performance of echo cancellation with a low complexity and high convergence speed. In addition, it solves the signal delay problem in the existing subband AEC. On the other hand, the proposed narrowband DTD is operating on low frequency subband. It can take most advantages from the narrow subband such as a low computational complexity due to the down-sampling and the reliable DTD decision making procedure because of the low-frequency nature of the subband signal. From the simulation results of the proposed narrowband DTD and wideband DTD, we confirm that the proposed DTD outperforms the wideband DTD in a sense of removing possible false decision making about the near-end speaker activity.

• Journal of the Korean Magnetics Society
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• v.17 no.5
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• pp.198-204
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• 2007

The effects of annealing temperature on electromagnetic wave absorption characteristics in $Fe_{73.5}Cu_1Nb_3Si_{15.5}B_7$ (at%) alloy flakes/polymer composite sheets available for quasi-microwave band have been investigated. The composite sheet including the magnetic flakes annealed at $425{\sim}475^{\circ}C$ for 1 h exhibited highest power loss in the GHz frequency range as compared with the sheets composed of the alloy flakes annealed at higher temperature than $475^{\circ}C$ or in as-milled state. Moreover the imaginary part of complex permeability had largest value in the GHz frequency range for the sheets including the flakes annealed at $425{\sim}475^{\circ}C$. The large value of power loss of the sheets including the magnetic flakes annealed at $425{\sim}475^{\circ}C$ was attributed to the high imaginary part of the complex permeability. However, because of its large transmission parameter $S_{21}$, the composite sheet having the magnetic flakes annealed at $525^{\circ}C$ showed low power loss.

• Journal of Korean Medicine Rehabilitation
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• v.23 no.4
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• pp.59-71
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• 2013

Objectives The aim of this review is to figure out which acupoints are frequently used to treat low back pain and which exercises are effective to low back pain. Methods We searched the three electronic database (RISS, KISS, KTKP) and manually checked related Korean journals and reference lists up to June 2013. We investigated the frequency of acupoints for using treatment of low back pain. We Introduce exercise therapies we can do easily at home without professional skills for treatment low back pain. Results We included 72 articles in this study. The most frequently adopted acupoints were BL25, BL23, BL24, GB30, BL40, BL26, BL60, GB34, BL52, BL57, GB39. The most frequently adopted meridian pathways were BL, GB, GV, ST. The most frequently adopted disease causing low back pain were HIVD (Herniated intervertebral disc), Lumbar sprain, Spinal stenosis, Compression fracture, Cauda equina syndrome, Spondylolisthesis, Ankylosing spondylitis. There are many exercise therapies (Lumbar stabilizing exercise, Resistance exercise, Bareunmom physical exercise, Mckenzie exercise, Williams exercise, Emblass exercise, Swiss ball exercise, Thera band exercise, Yoga) for treatment low back pain. Conclusions These results suggest that most frequently adopted acupoints were foot taeyang urinary bladder channel acupoints. Beacuse foot taeyang urinary bladder channel is passes through the waist, it will be effective for treatment of low back pain. Also exercise therapy is effective for enhance Muscular strength. In order to treatment of low back pain, Acupuncture treatment is also important, as well as exercise therapy.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.7
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• pp.727-732
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• 2008

Recently, according to the increase of using the microwave equipments, the interests in effects on human body have been also increased. For example, there have been many researches on making the standard the specific absorbing ratio (SAR) caused by mobile phones. However, it is needed to study on the induced current on human body caused by HF(Hight Frequency) band which can deeply penetrate the human body. Especially, since the RFID systems are applied to the transportation card and the library, it is hooded to research on the effect on human body exposed to the radiated power from the RFID system. In this paper, we designed a cylindrical monopole antenna model of human body exposed to 13.56 MHz RFID system, which can model the induced current on human body. To verify the proposed equivalent antenna model, we compared the induced currents between human body and the equivalent antenna model.

• Journal of the Korean Society of Clothing and Textiles
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• v.32 no.11
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• pp.1692-1703
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• 2008

On 2008, China comes to be an era of opening the market for 30 years, being both the 4th economically biggest country and 2nd ranked clothing export country in the world. China plays a huge consuming market for the world, along with the competition arena for the numerous world fashion brands while more than 100 kinds of Korean fashion ones being launched into the China. By applying the analysis and investigation of preferred street style. in local area to the development of fashion items and design, the synergistic effect of university and industrial corporation might also be expected. This study aims to provide the basic resources for the development of fashion design on behalf of the Korean fashion brands launched into China and moreover to anticipate the requirement on the part of Chinese consumers by way of understanding the preferred fashion styles, through analysis and investigation of the street fashion in Dalian, northeastern area of China. Conclusively, in terms of clothing style, 80.5% of casual style and 19.5% of formal style were notified. The jean casual, and easy casual being dominant in the former, feminine style in the later. In view of the high frequency of T-shirt, sleeveless on the top, full-length pants and 7/9 length pants on the bottom. The simple and cool style seems to be favored, making them easy through the hot summer. The upper clothes exposed in body part of back, chest and shoulder, were frequently shown. In light of colours. white, black, red were preferred on top, blue and black were preferred on bottom. To deal with accessories, the shoulder bag mostly preferred among bags, the sandal, slippers, snickers in sequential order among shoes, the hair pins and rubber band(tied or, held up style), in hair accessories. Other items of hat, belt, and sunglasses, which could give a point to the summer style, were identified low frequency.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.8
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• pp.117-125
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• 2015

In this paper, we propose a classification algorithm based on the obtained EEG(Electroencephalogram) signal for the control of 'left' and 'right' turnings of which a driving system composed of EEG sensor, Labview, DAQ, Matlab and driving robot. The proposed algorithm uses features extracted from frequency band information obtained by DWT (Discrete Wavelet Transform) and selects features of high discrimination by using Fisher score. We, also propose the number of feature vectors for the best classification performance by using SVM(Support Vector Machine) classifier and propose a decision pending algorithm based on MLD (Maximum Likelihood Decision) to prevent malfunction due to misclassification. The selected four feature vectors for the proposed algorithm are the mean of absolute value of voltage and the standard deviation of d5(2-4Hz) and d2(16-32Hz) frequency bands of P8 channel according to the international standard electrode placement method. By using the SVM classifier, we obtained 98.75% accuracy and 1.25% error rate. Also, when we specify error probability of 70% for decision pending, we obtained 95.63% accuracy and 0% error rate by using the proposed decision pending algorithm.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.2 s.117
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• pp.126-135
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• 2007

This paper proposes a new miniaturization method for a parallel coupled line filter with enhanced bandwidth characteristics. A previous method incorporated several advantages, such as size reduction through the use of only a small number of capacitors, in addition to grounding, suppression of harmonic characteristics, and improved skirt characteristics for the parallel coupled line filter, which is conventional in the field of RE filters due to its design and fabrication simplicity. However, the previous method also has disadvantages related to the bandwidth shrinkage of the miniaturized filters. In this paper, the amount of bandwidth shrinkage is analyzed in terms of the relationship between the loaded Q(quality factor) and the group delay of a resonator. Moreover, the reduction in the bandwidth is solved by a design with new design equations. To show the validity of the proposed method, a hairpin filter with a center frequency of 5.2 GHz and an fractional bandwidth(FBW) of 10% was scaled down to half its original dimension by the proposed method with the enhanced bandwidth characteristics. The measured result shows a high level of agreement with theoretical results.

• Journal of the Korean Wood Science and Technology
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• v.42 no.3
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• pp.339-345
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• 2014

For enhancing productivity of glulam, high frequency (HF) curing technique was researched in this study. Heat energy is generated by electromagnetic energy dissipation when HF wave is applied to a dielectric material. Because both lamina and adhesives have dielectric property, internal heat generation would be occurred when HF wave is applied to glulam. Most room temperature setting adhesives such as phenol-resorcinol-formaldehyde (PRF) resin, which is popularly used for manufacturing glulam, can be cured more quickly as temperature of adhesives increases. In this study, dielectric properties of larch wood and PRF adhesives were experimentally evaluated, and the mechanism of HF heating, which induced the fast curing of glue layer in glulam, was theoretically analyzed. Result of our experiments showed relative loss factor of PRF resin, which leads temperature increase, was higher than that of larch wood. Also, it showed density and specific heat of PRF, which are resistance factors of temperature increase, were higher than those of wood. It was expected that the heat generation in PRF resin by HF heating would occur greater than in larch wood, because the ratio of relative loss factor to density and specific heat of PRF resin was greater than that of larch wood. Through theoretical approach with the experimental results, the relative strengths of ISM band HF electric fields to achieve a target heating rate were estimated.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.4
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• pp.282-285
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• 2019

A 100-nm gate-length metamorphic high electron mobility transistor(mHEMT) with a T-shaped gate was fabricated using a two-step gate recess and characterized for DC and microwave performance. The mHEMT device exhibited DC output characteristics having drain current($I_{dss}$), an extrinsic transconductance($g_m$) of 1,090 mS/mm and a threshold voltage($V_{th}$) of -0.65 V. The $f_T$ and $f_{max}$ obtained for the 100-nm mHEMT device were 190 and 260 GHz, respectively. The developed mHEMT will be applied in fabricating W-band monolithic microwave integrated circuits(MMICs).