• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.246-247
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• 2001

짧은 파장의 레이저 빔이 비선형 결정에 입사할 때 긴 파장의 두 광으로 자발적으로 변환하는 매개 하향변환(parametric down-convension; PDC)과정을 통해서 양자적 상관관계를 갖는 광원을 얻을 수 있다. PDC 과정은 에너지 보존 (w$_{p}$ = w$_{s}$ ＋ w$_{i}$)과 운동량 보존 (k$_{p}$ = k$_{s}$ ＋ k$_{i}$)에 해당하는, 위상조화 (phase matching) 조건이 잘 만족할 때 효과적으로 일어난다. PDC에서 광자들이 아주 짧은 시간에 쌍으로 발생한다는 것과 이러한 광자쌍을 동시에 측정하는(coincidence count; 동시계수) 방법을 이용하면 효과적으로 신호와 잡음을 분리해 낼수 있고, 배경(background)이나 잡음(noise)보다 미약한 신호를 통해서도 정보를 전달할 수 있는 가능성을 제공해준다. (중략)

• Journal of Communications and Networks
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• v.7 no.1
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• pp.13-20
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• 2005

In this paper, a new multi carrier, direct sequence code division multiple access (MC-DS-CDMA) system is proposed. Our new signal construction is based on convolutional encoding of the transmitted data, serial-to-parallel (S/P) conversion of the encoded data, Walsh-Hadamard-transformation (WHT), a second S/P conversion of the WHT outputs, spread spectrum (SS) modulation with a common pseudo-noise (PN) sequence, and then multicarrier transmission. The system bit error rate (BER) performance in frequency selective fading channel in the presence of additive white Gaussian noise (AWGN) and a jamming tone is analyzed and simulated. The numerical results are compared with those from an orthogonal MC-DS-CDMA system of Sourour and Nakagawa [7]. It is shown that the two systems have almost the same BER performance, but the proposed scheme has better anti-jamming ability.

• Child Health Nursing Research
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• v.4 no.2
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• pp.265-273
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• 1998

The purpose of this study was to identify the children's sleeping patterns, such as the sleeping hours and the nature of sleep disruptions following hospitalization and its accompanying factors. The data were collected from December, 1997 to March, 1998 using a questionnaire developed by researchers. The subjects were 76 children in a hospital. The results of this study were summarized as follows : 1. The average sleeping hours (sleep duration) at night were 10 hours and 10 minutes and 9 hours and 9 minutes before and after hospitalization respectively. There was a significant difference (p<0.01). The average sleeping hours in the day time were 1 hour 28 minutes and 2 hours and 26 minutes before and after hospitalization respectively. There was a significant difference(P<0.01). 2. The mean bed time(sleep onset) was 10: 22 pm and 10 : 28 pm before and after hospitalization respectively. There was no significant difference. 3. The mean hour of rising(sleep termination) was 7: 54 am 7 : 08 am before and after hospitalization respectively. There was a significant difference (p<0.01). 4. The mean number of sleep disruption was 0.72 and 1.94 before and after hospitalization respectively. There was a significant difference(P<0.01). The sleep disruptions were influenced by crying of other children(53.9%), lights(28.9), nursing procedures(18.4%), noise of TV(17.l%) and noise of visitors (15.8%).

• Journal of the Korean Society of Radiology
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• v.11 no.7
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• pp.619-625
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• 2017

The sudy was intended to evaluate the optimal equipment selection by quantitatively assessing the SNR(signal to noise ratio) and CNR(contrast to noise ratio) on the abdominal organ. This study performed on 1.5 T and 3.0 T MRI units focusing on HASTE, HASTE(f/s) and FFE(in of phase), FFE(out of phase) without using the contrast medium(Gadolinium). The data analysis was performed by randomly selecting on 1.5 T and 3.0 T abdominal MRI images. As a results, SNR and CNR values of 3.0 T is higher than 1.5 T at liver, kidney and spleen(p<0.05). Stomach, abdominal fat and pancreas was obtained a higher value at 1.5 T(p<0.05). On conclusion, the organs of outer part in the body showed generally a high value at 3.0 T, and the organs of inner part in the body including the gas showed a high value at 3.0 T because of a large difference on magnetic susceptibility.

• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.240-242
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• 2005

It is well known that the PD (Partial Discharge) signals are generated if insulators have some defects such as voids in electrical facility and various PD detection methods are developed for preventing electrical troubles. So, an interest for the PD signals is higher and higher according to the high concern for the defects detection method of the aging electrical facility. When the equipment to detect PD signals installed at site and it works, a lot of noises flow in the equipment from surrounding situation and it will be mixed with original PD waveform. So we can not get the desired PD waveform. Therefore, there are many trial to reject or suppress the noise from the PD signals from long times ago. The greater of them used the hardware such as bridge circuits and frequency filters to suppress the noise. This paper proposed a novel noise rejection method in acquired data from PD detection equipment. The noise has the irregular phase and higher signal level than real PD, and noise decision is performed after inspection of pulse distribution in ${\Phi}$-q-n graph of acquired data from PD detection equipments. By experimental results on high voltage electric equipments, it is shown that proposed method has good performance. It is expected that this noise rejection technology is useful in numeric calculation and trend management of PD level.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2019.05a
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• pp.214-216
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• 2019

Recently, as the use of digital equipment increases in various fields, the importance of image and signal processing is increasing. However, many kinds of noise occur in the digital signal during transmission and reception, and this noise greatly affects the final output of the system. In this paper, we propose an algorithm that effectively restores the image by removing noise according to pixel similarity in a mixed noise environment with impulse noise and AWGN. The proposed algorithm sets the reference value according to the noise type and applies the filtering to pixels similar to the reference value to obtain the final output. Simulation results show that the proposed algorithm has good noise canceling performance and compared with conventional methods using PSNR.

• The Journal of the Acoustical Society of Korea
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• v.40 no.6
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• pp.678-682
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• 2021

Reverberation Time (RT) with noise levels can affect speech recognition ability in a listening environment. The degree of influence may depend on reverberation times and modes of binaural hearing. In this study, Korean monosyllabic Word Recognition Scores (WRS) were investigated in 10 young normal hearing subjects under binaural conditions. The RT of 3.4 s and signal to noise ratio of 0 dB were used at 55 dB HL for diotic (noise with the same phase) and dichotic (noise with the fixed phase difference, π) conditions. The improvement in WRS was noted in dichotic hearing (p < 0.05) while the similar trend was not observed in diotic hearing. This data may be useful in analyzing psychoacoustic effects of RTs under noisy conditions.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.8 no.2
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• pp.45-51
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• 1990

DEM must have a high accuracy against the actual topographic model. A model which can compute heights responding to random plane position by using of the topographic data and interpolation must be constructed. Interpolation affected by the accuraccy of the observations included noise, which affected by the slop and curvature weight. Data smoothing is a method to reduce the noise. Average declination and area ratio are variable which result similarity in according to slope. But in local area, area ratio well shows a local change. This study try to classify the terrain by the declination to analysis the effects of the declination and curvature weights, and then to represent the most probable model. The result are following : In terrain classification by the slop, p16 and p24 were fitted in the plane surface fit p16 and S in the varying surface, and S and p24 in the irregular surface in classification by curvature, p24 and S were fitted in the plane or varying surface, and p16 in the irregular surface In case of hybrid, p16, p24 and S are fitted in the plane, varying and irregular surface respectively. Smoothing is the most effective in case of slope of 50 persentage and of curvature weight of 0.0015.

• The Journal of Korean Physical Therapy
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• v.14 no.4
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• pp.183-203
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• 2002

To know the effect of index of social ability (ISA) and function of social life (FSL) with activities of daily living (ADL) and instrumental activities of daily living (IADL), we carried out a study on the elderly with osteoarthritis daily living in Daegu city for 4 months, from April to July 2002. The followings were observed: 1. The score of functional disability of knee, ADL and ISA were better at lower age (p < 0.01). 2. The younger they are, the better FSL they have. The lower age group has good FSL (p < 0.01). 3. Weight affects more to the under 49Kg group than 50-59Kg group and 60-69Kg group in functional disability of knee, while it doesn't make much difference for the other groups (p > 0.05) and other assessment index doesn't show any relationship with weight. 4. Regarding relat ionship with height , taller group has better knee functions: it's proved by post hock examination that the over 160cm group has much higher knee function than the other groups (p < 0.05). In case of ADL, the over 160cm group and under 149cm group were better than 150$\∼$159cm group. (p < 0.01) . 5. ISA was also different depending on height . It was proved that FSL was the better for the over 160cm group than for the others as a result of post hock examination (p < 0.05). 6. In regard of how many months have passed since the attack of functional disability of knee, knee joint function was better for the 12mon$\∼$36mon group than for the others and the score of ADL was lower for the 12mon$\∼$36mon group than for the others (p < 0.01). ISA was lower for the 12mon$\∼$36mon group and the under 6mon group than for the other groups (p < 0.01). FSL was lower for the 12mon$\∼$36mon group and the under 6mon group than the other groups. (p < 0.01). 7. Comparing left knee with right one, the problem with left knee has lower score of functional disability in all items (p < 0.01). 8. Considering friction noise, knee joint function was slightly better for non-friction noise-group, but it's not statistically significant though. ADL and ISA were better for non-friction noise-group (p < 0.01), while no statistical significance was found in FSL, 9. Knee joint function was better for the group who doesn't have limitation on range of knee flexion motion (p,0.05) but no other difference was found in other items from this group. 10. Limitation on range of knee flexion motion has no statistical difference in ADL and FSL. However, ISA was better for the non-limitation group (p < 0.05) . 11. Knee joint function score has high correlation with ISA (r=0.812, p < 0.01) and FSL (r=0.732, p < 0.01) , which shows the better knee joint function, the higher the score. 12. ISA and FSL were highly correlated: the better ISA, the better FSL (r=0.893, p < 0.01), while ADL has no correlation with either knee joint function or ISA or FSL.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.387-390
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• 1998

In this paper, HBT's with lower phase noise and passive elements, such as resistors, capacitors and inductors, for resonance and impedance matching networks are designed, fabricated, tested, and carefully analysed, respectively, and then, they are integrated for the design and fabrication of functional X-band oscillators with lower phase noise. Epi-wafers for HBT's with the structure of graded $Al_{x}$G $a_{1-x}$ As emitter and C-doped base layer of 700.angs. thick were used to specially emphasize the improvement of $f_{T}$ and $f_{max}$, and the lowering of phase noise, in design aspects. At the test frequencies of 12GHz, capacitances of MIM capacitors, spiral inductor, and resistances are 0.5~10pF, 0.4~11.06nH, and 20~1,380.ohm., respectively. The emitter size of HBY's for the X-band MMIC oscillators is 3*10u $m^{2}$, and find chip size is 0.9*0.9m $m^{2}$..EX>.