• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.5
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• pp.589-594
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• 2014

It has been known that the particular brain waves are induced when a human concentrates. In our study, we aimed to analysis the brain waves related to human concentration using visual stimulus to induce the concentration. The visual stimulus tasks were presented to subjects for concentration. We measured EEG signals with several channels and analyzed the signals into several frequency bands. In the measured EEG signals, we analyzed to focus on theta waves, SMR waves and mid-beta waves. Therefore we presented the results to investigate characteristics of the EEG signals related to the human concentration.

• Korean Journal of Food Science and Technology
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• v.26 no.6
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• pp.791-798
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• 1994

Ohmic heating is a food processing operation in which heat is internally generated within foods by the passage of alternating electric current. The process enables highly viscous paste foods such as Kochujang, and fermented soybean paste to be heated very fast. In order to develope the novel pasteurization process of paste foods, static Ohmic heating system was built, and heating characteristic during Ohmic heating under various conditions were studied. Electric conductivities of Kochujang and fermented soybean paste at room temperature were 1.865 S/m and 2.510 S/m, respectively and increased linearly with increasing temperature. Specific heating rate was highly dependent on the frequency. The highest heating rate was achieved at 5 KHz for Kochujang and 20 KHz for fermented soybean paste. Uniform heating throughout the sample was achieved during Ohmic heating with low frequency electrical currents, however above 5 KHz frequency, surface temperature was several degrees higher than the bulk.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.4
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• pp.352-361
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• 2010

In this paper, a compact 20 W block-up-converter for C-band satellite communication is designed and implemented. The designed block up-converter consists of an intermediate frequency circuit, a mixer and local oscillator, a driver amplifier, a solid-state power amplifier, waveguide circuits, and a power supply module. To reduce the size of the block-up-converter, all circuits are assembled within an housing, so its dimension is just $21{\times}14{\times}11cm^3$. Especially, the waveguide filter and microstirp-to-waveguide transition are easily implemented using an housing. Also, to meet spurious and harmonics specification, various compact microstrip filters including an elliptic filter are integrated. Measurement results show that the developed block up-converter has good electrical performances: the output power of 43.7 dBm, the minimum gain of 65 dB, the gain flatness of ${\pm}1.84$, the IMD3 of -35 dBc, and the harmonic level of -105 dBc.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.14 no.1
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• pp.15-36
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• 1978

Underwater sounds of some fishes and crabs were analyzed in the laboratory. The behavioral responses to the playback sounds of their feeding and croaking sound were investigated. The samples used in the experiment were as follows: Nibea albiflora, seriola quinqueradiata, Navodon modestus, Fugu xanthopterus, chrysophrys major, Scylla serrata, Telmessus acutidens, Charybdis japonica, and Portunus trituberculatus. The feeding and croaking sounds of the samples were recorded by a tape recorder through a hydrophone in an anechoic aquarium. The sound intensity level was measured by means of a sound level meter at an anechoic chamber. The frequency, intensity and wave form of various sounds were analyzed with an analyzing system consisting of a 1/3 octave filter set, a high speed level recorder, an amplifier, an octave band analyzer and an oscilloscope. The most successful recording was edited into a sequence of sound track which repeats sound emitting for 5 to 7 seconds after pausing for 5 to 7 seconds. The sequence was then reproduced into an anechoic aquarium through the under water speaker. The experimental anechoic aquarium used for the sample fishes was divided into the four sections with any three screens selected from 40$\times$40mm, 60$\times$60mm, 80$\times$80mm and 100$\times$100mm mushes according to the species of the fishes, besides that for crabs were not sectioned. The results of the investigation are as follows: 1. Of the feeding sound of fish, the frequency of wave from of the sound produced by Nibea albiflora and seriola quinqucradiata was 125～250Hz, that by Navodon modestus 63～125Hz, and that by Fugu xanthopterus 400～500Hz. The pressure level of the feeding sound produced by Nibea albiflora and Seriola quinqueradiata was 56～62db, that by Navodon modestus 57～59db, and that by Fugu xanthopterus 60～64db. 2. Of the croaking sound of Nibea albiflora, the frequency of the sound was 125～250Hz almost equivalent to that of feeding sound, and the pressure level was 62～63db, slightly higher than that of feeding sound. 3. Of the croaking sounds of crabs, the frequency of the sound produced by scylla serrata was 125～250Hz, that by Charybdis japonica and Telmessus acutidens 500～1,000Hz, and that by Portunus trituberculatus 250～500Hz. The pressure level of the croaking sound by Scylla serrata was 68～70db, and that by Charybdis japonica, Telmessus acutidens and Portuens trituberculatus 50～62db. 4. Phonotactic responses of Nibea albiflora and Seriola quinqueradiata to the feeding sounds produced by their own species, the same body length were conspicuous with the phonotactic index of 56～87%, but that of Navodon modestus, Chrysophrys major and Fugu xanthopterus were hardly recognized. 5. Phonotactic responses of the sample fishes to the sinusoidal sound with the frequency range of 50 to 9,000 Hz were observed not conspicuous. 6. Phonotactic responses of Portunus trituberculatus to the croaking sounds produced by their own species was varied in the range of 40～100%, according to the carapace length and the sex.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.3
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• pp.541-546
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• 2010

The push-push DRO(dielectric resonator oscillator) using a multi-layer structure of LTCC(low temperature co-fired ceramic) fabrication is designed. After the single DRO of series feedback type in the center frequency of 8GHz is designed, the push-push DRO in the center frequency of 16GHz including the Wilkinson power combiner is designed. The bias circuit affecting the size of oscillator are embedded in the intermediate layer of the LTCC multi-layer substrate. As a result, the large reduction in the size of VCO is obtained compared to the general oscillator on the single layer substrate. Experimental results show that the fundamental and third harmonics suppression are above 15dBc and 25dBc, respectively, and phase noise characteristics of the push-push DRO presents performance of -102dBc/Hz@100KHz and -128dBc/Hz@1MHz offset frequencies from carrier.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.4
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• pp.323-335
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• 1992

In this paper, an adaptive cosine transform coding scheme which incorporate human visual properties into the coding scheme is investigated. Human vision is relatively sensitive to mid-frequency band, and insensitive to very low and very high frequency band. These property was mathematically modelled with MTF(Modulation Transfer Function) through many psychovisual experiment. DCT transforms energy in spatial domain into frequency domain, so can exploit the MTF very efficiently. Another well-known visual characteristics is spatial masking effect that visibility of noise is less in regions of high activity than in regions of low activity. Proposed coding scheme imploys quantization matrix which represent the properties of these spatial frequency response of human vision, and adaptively quality of an image. To compute the activity index of an image block, simple operation is performed in spatial domain, and according to activity index. block of low activity region is more exactly quantized relatively than that of high activity region. Results showed that, at low bit rate, the subjective quality of the reconstructed images by proposed coding scheme is acceptible than that of coding scheme without HVS properties.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.1
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• pp.1-8
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• 2005

In this paper, peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) with respect to the subchannel coding schemes for interchannel interference (ICI) self-cancellation is analyzed. It is shown theoretically and experimentally that a shaping component is generated in the transmitted sequence in the conventional correlative coding where a pair of antipodal signals is assigned in adjacent subchannels. Due to the shaping component, the signal powers in the mid and edges of a symbol are scaled by different weighting coefficients, resulting in increased PAPR. To overcome this problem a simple adjacent subchannel coding scheme is presented in this paper. In the new scheme, the shaping component caused by partial repetition of signals is eliminated by assigning a pair of signals in which phase difference varies signal-to-signal. As results, the new scheme has 2-3 dB smaller PAPR than the conventional ICI self-cancellation OFDM while maintaining much higher carrier-to-interference ratio than a normal OFDM system.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.11
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• pp.107-115
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• 2005

This paper presents the structure of a broadband coplanar waveguide(CPW) fed square slot antenna with a impedance bandwidth tuning patch. The designing method of the antenna suggests that two resonant frequencies are excited as a dual-frequency dipole antenna following the dimensions of the square slot. In other words, the lower resonant frequency mainly depends on the slot width and the higher one its length. A CPW fed square slot antenna with a impedance tuning patch was measured to $20GHz^\~33GHz$, $50\%$, VSWR=2 impedance bandwidth by adjusting the dimensions of the tuning patch when the slot length had $70\%$ of its width. This result shows that a medical CPW fed antenna is easily implemented with a simple square slot structure including a bandwidth tuning patch in the center.

• Journal of Oral Medicine and Pain
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• v.17 no.2
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• pp.51-61
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• 1992

저자는 서울대학병원 치과진료부 구강진단과를내원한 두 개하악장애 환자 중, 악관절음이 있음을 호소하는 환자 106명을 대상으로 SonoPAK을 이용하여 악관절음을 분석하고 Transcranial TMJ Series와 파노라마상 판독결과를 종합하여 다음과 같은 결론을 얻었다. 1. SonoPAK에 기록된 210회의 발생 악관절음 중 왕복성 관절음은 44건, 88회 발생하였고, 개구시 관절음은 74회, 그리고 폐구시 관절음은 48회 발생하였으며, 개구시에 관절음이 더 빈번히 나타났다. 2. 왕복성 악관절음이 있다고 인정되는 혼자군에서, 개구시 평균 최대 단위는 18.6(%)$\pm$15.6(%), 폐구시 평균 최대 진폭은 16.6(%)$\pm$17.4(%) 이었으며, 개폐구간 진폭의 차이에는 유의성이 없었다. (p>0.05). 3. 악관절음을 미약한 소리, 중간소리, 큰소리로 분류할 수 있었으며 각각 110, 79,21회의 발생을 기록하였다. 4. (>300Hz)/(<300Hz)의 비율이 0인 경우는 34회 였고, 300Hz 이상의 주파수가 관찰된 경우는 176회였다. 5. Transcranial TMJ projection series 와 파노라마상의 판독 결과 하악과두의 골 변화가 인정된 환자군에서 SonoPAK 기록의 평균 주파수 비율((>300Hz)/(<300Hz))은 0.387$\pm$0.284이었고 골 변화가 인지되지는 않았으나 주파수 비율이 0.01 이상인 환자군의 평균은 0.286$\pm$0.227이었다.

• Journal of Digital Contents Society
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• v.8 no.3
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• pp.355-363
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• 2007

One of major factors for learning achievement is the student's learning preference according to his character type. In course of learning, if a student studies e-learning contents opposed to his preference, then he would be under stress and his blood pressure and heart beat be changed. For measuring unwillingness, we used spectral components in frequency domain known as stress measure. For 13 children attending kindergarten we examined S(sensing)/ N(intuition) of MBTI and presented same learning contents during 10 minutes. During learning we gathered ECG signals, changed into HRV(heart rate variability), transformed time-varying HRV signal into spectral density in frequency domain. And then, we divided it into three areas of low(LF), middle(MF), and high-frequency(HF) and calculated stress measures by rates of those frequency area. We compared estimated stress measures of S group with them of N group whether students in different group preferred different contents or not. Experimental shows that students according to MBTI type prefer different contents.