• Progress in Medical Physics
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• v.8 no.1
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• pp.53-67
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• 1997

General hospitals have being under the influence of various and specific environment of electromagnetic field. The factors are development of medical electric equipment and device with enlarged functional demands, in high power and multi-frequency. It has all of both faces, EMI(electromagnetic interference) and EMS(electromagnetic susceptibility). In additional, expansion of personal communication system(cellular phone) has many unreliable factor of using time and area, making noise of electromagnetic fields. We studied actual conditions of EMI in the medical site, where is numerous medical equipment, especially central operation room and ICU(intensive care unit), AKR(artificial kidney room : hemo-dialysis unit), etc. The influence, most of medical equipments made electromagnetic nosie has various factors in its band of frequency, harmonics and strength. In the experimental use of electro-surgical unit and cellular phone, noticeable and considerable noise of eletromagnetic fields were measured. All of that can make trouble and errors on the steadiness of bioelectrical devices. In conclusion, It is necessary to reconsiderations of reallocating EMI source vs. EMS factor, and set to definite forbiding area of using cellular phone. For maintenance of steady normal conditions, in spite of existing any other legal standards of safty level, it need considering all of alternative electromagnetic situations on a case-by-case basis.

• Investigative Magnetic Resonance Imaging
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• v.3 no.2
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• pp.167-172
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• 1999

Purpose : To evaluate the detection rate of hyperacute intracerebral hemorrhage in echo planar imaging (EPI) and other MR sequences. materials and Methods : Intracerebral hemorrhage was experimentally induced in ten rats. EPI, fast spin-echo (FSE) T2 weighted images, fluid attenuated inversion recovery (FLAIR), spin-echo (SE) T1 weighted images and gradient echo (GE) T1 weight ed images of rat's brains were obtained 2 hours after onset of intracerebral hemorrhage. EPI and FSE T2 images were additionally obtained 30 min and 1 hour after onset of hemorrhage in 3 and 6 rat, repeatedly, For objective visual assessment, discrimination between the lesion and normal brain parenchyma was evaluated on various MR sequences by three radiologists. For quantitative assessment, contrast-to-noise ratio (CNR) was calculated fro hemorrhage-normal brain parenchyma. Statistical analysis was performed usning the Wilcoxon-Ranks test. Results : EPI, FLAIR, and FSE T2 images showed high signal intensity lesions. The lesion discrimination was easier on EPI than on other sequences, and also EPI showed higher signal intensity for the subjective visual assessment. In quantitative evaluation, CNR of the hemorrhagic lesion versus normal brain parenchyma were higher on EPI and FLAIR images (p<0.01). There was no difference in CNR between EPI and FLAIR (p>0.10). On MR images obtained 30 minutes and 1 hour after the onset of intracerebral hemorrhage, the lesion detection was feasible on both EPI and FSE T2 images showing high signal intensity. Conclusion : EPI showed higher detection rate as compared with other MR sequences and could be useful in early detection and evaluation of intracerebral hemorrhage.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.5
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• pp.492-499
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• 2002

Performance analysis and comparison of the hybrid DS-SFH spread-spectrum (SS) system using coherent MSK and QPSK modulation techniques over Rayleigh fading channel are considered in the presence of MTJ(multi-tone jamming). To analyze the BER performance of the hybrid systems with or without the Rake receiver, signal-to-noise plus interference ratio is derived as a function of the average signal-to-noise ratio, the jammer-to-signal ratio and other system parameters. Numerical results show that the performance difference between the two modulation schemes, MSK and QPSK, is negligible for low JSR, while it becomes significant with the increase of JSR. In multi-path Rayleigh fading channel without Rake receiver, the performances of the two modulation schemes are slightly improved as the DS spreading gain is increased when the total SS bandwidth is fixed. In particular, there is an optimum DS spreading gain for large JSR, in which a minimum BER is achieved, while only DS spreading gives the best performance for small JSR. For hybrid systems with Rake receiver, it is shown that the hybrid system of the MSK modulation scheme provides better anti-jamming performance and larger performance improvement with the increase of multi-path resolution capability of Rake receiver than that of QPSK modulation for all conditions.

• Journal of KIISE:Software and Applications
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• v.33 no.4
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• pp.402-410
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• 2006

This paper presents a method for feature based block motion estimation that uses multi -resolution image sequences to obtain the panoramic images in the continuous ultrasound image sequences. In the conventional block motion estimation method, the centers of motion estimation blocks are set at the predetermined and equally spaced locations. This requires the large blocks to include at least one feature, which inevitably requires long estimation time. In this paper, we propose an adaptive method which locates the center of the motion estimation blocks at the feature points. This make it possible to reduce the block size while keeping the motion estimation accuracy The Harris-Stephen corner detector is used to get the feature points. The comer points tend to group together, which cause the error in the global motion estimation. In order to distribute the feature points as evenly as Possible, the image is firstly divided into regular subregions, and a strongest corner point is selected as a feature in each subregion. The ultrasound Images contain speckle patterns and noise. In order to reduce the noise artifact and reduce the computational time, the proposed method use the multi-resolution image sequences. The first algorithm estimates the motion in the smoothed low resolution image, and the estimated motion is prolongated to the next higher resolution image. By this way the size of search region can be reduced in the higher resolution image. Experiments were performed on three types of ultrasound image sequences. These were shown that the proposed method reduces both the computational time (from 77ms to 44ms) and the displaced frame difference (from 66.02 to 58.08).

• Journal of the Korean Society of Radiology
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• v.5 no.2
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• pp.97-101
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• 2011

In this study, the basic research verifying possibility of applications as radiology image sensor in Digital Radiography was performed, the radiology image sensor was fabricated using double layer technique tio decrease dark current. High efficiency material in substitution for a-Se have been studied as a direct method of imaging detector in Digital Radiography to decrease dark current by using Hetero junction already used as solar cell, semiconductor. Particle-In-Binder method is used to fabricate radiology image sensor because it has a lot of advantages such as fabrication convenient, high yield, suitability for large area sensor. But high leakage current is one of main problem in PIB method. To make up for the weak points, double layer technique is used, and it is considered that high efficient digital radiation sensor can be fabricated with easy and convenient process. In this study, electrical properties such as leakage current, sensitivity is measured to evaluate double layer radiation sensor material.

• The Journal of the Acoustical Society of Korea
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• v.35 no.1
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• pp.74-82
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• 2016

In this paper, a new automatic speech recognition (ASR) was proposed where ultrasonic doppler signals were used, instead of conventional speech signals. The proposed method has the advantages over the conventional speech/non-speech-based ASR including robustness against acoustic noises and user comfortability associated with usage of the non-contact sensor. In the method proposed herein, 40 kHz ultrasonic signal was radiated toward to the mouth and the reflected ultrasonic signals were then received. Frequency shift caused by the doppler effects was used to implement ASR. The proposed method employed multi-channel ultrasonic signals acquired from the various locations, which is different from the previous method where single channel ultrasonic signal was employed. The PCA(Principal Component Analysis) coefficients were used as the features of ASR in which hidden markov model (HMM) with left-right model was adopted. To verify the feasibility of the proposed ASR, the speech recognition experiment was carried out the 60 Korean isolated words obtained from the six speakers. Moreover, the experiment results showed that the overall word recognition rates were comparable with the conventional speech-based ASR methods and the performance of the proposed method was superior to the conventional signal channel ASR method. Especially, the average recognition rate of 90 % was maintained under the noise environments.

• Journal of the Korean Society of Radiology
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• v.4 no.2
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• pp.27-30
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• 2010

A X-ray optical modulator measures x-ray dose using optical transmissivity ratio change of the liquid crystal cell. To apply in this optical modulator, we made photoconductor films and compared electrical properties of this films in this study. Photoconductors are deposited on ITO glass with $200{\mu}m$ using the percipitation method and print method. I-V test was conducted to alalyze electrical properties of this films and measured darkcurrent and SNR was acquired using the measured dark current and sensitivity. As a result of this measurements, $HgI_2$ film made by precipitation method is lower(about 40%) darkcurrent than $HgI_2$ films made by precipitation method and sensitivity is two times greater than print method. And we knew that $HgI_2$ films were also 10~25 times greater SNR at $1v/{\mu}m$ than $PbI_2$, PbO, CdTe film made by precipitation method. This results suggest that $HgI_2$ films made by precipitation method has improved characteristics of x-ray dose meter by applying in x-ray optical modulator.

• Geophysics and Geophysical Exploration
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• v.22 no.3
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• pp.107-115
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• 2019

Recently, since earthquakes have happened frequently in Gyeongju and Pohang areas in Korea, the earthquake detection research gets lots of attention. Geophysical monitoring data have been changed during the earthquake activity because the huge amount of energy is accumulated. The change of telluric current can be predicted by both of piezoelectric and electrokinetic effects before or during the earthquake occurrence, and if the change value exceeds the conventional telluric current noise, we can measure changes in the electric field associated with earthquakes. In this study, we have self-developed and verified the system that can monitor the telluric current. In order to verify our telluric current monitoring system, we installed lines of 40 m (E-W direction) and 28 m (N-S direction) on the site in Pohang. The telluric currents were sampled at 1 kHz for about a month. We have compared and analyzed the data of earthquake signals and electrical noises based on the earthquakes that occurred during the monitoring period. We have monitored if there were significant signals related to the earthquake on measured time series data. Through this study, we will suggest the direction of continuous research in the future.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.21 no.3
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• pp.270-276
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• 1999

저자등은 1996년 5월 부터 1999년 4월까지 인하대병원 치과에 악관절 질환을 주소로 내원한 958명의 환자 중 병력, 임상소견, 방사선학적 검사 결과 퇴행성 악관절 질환으로 진단된 68명에서 병록지 상에 기록된 환자의 성별, 나이, 주소, 병력, 현증상, 방사선학적 소견 및 치료방법 등에 관해 검사 후 다음과 같은 결론을 얻었다. 1. 남녀 발병 비율은 1:2로 여성에서 높았다. 2. 발병나이는 20대, 30대. 40대, 10대 순이었다. 3. 병력기간은 2년이상, 6개월이하, 1 - 2년 순이었다. 4. 전 환자에서 악관절 동통을, 44명의 환자에서 관절잡음을, 26명의 환자에서 개구제한을 호소하였다. 5. 그밖에 26명의 환자에서 관절부위에 민감성을, 5명의 환자에서 안면 비대칭을, 또한 개교합, 섬유성 악관절강직의 소견이 각각 2명의 환자에서, 양측성질환의 소견이 4명의 환자에서 관찰되었다. 6. 방사선학적 소견상, 15명 환자의 과두부에서 증식성 재성형소견(progressive remodeling)이, 51명의 환자에서 침식성 재성형소견(regressive or erosive remodeling)이 관찰되었으며, 침식성 재성형 환자 중 11명에서 과두주변부 증식성 재성형소견(peripheral remodeling or marginal lipping)이 관찰되었다. 7. 골증식체(osteophyte) 및 소성체(loose body)의 소견이 각각 2명의 환자에서 관찰되었다. 8. 약물에 의한 보존적 치료방법이 1차로 모든 환자에서 시행되었으며, 이중 12명의 환자는 교합안정장치를 병행하여 치료하였다. 9. 관절강내 스테로이드 주사요법에 의한 치료환자가 2명, 관절원판절제술 및 이개연골 이식술을 동반한 악관절성형술 환자가 각각 1명 및 2명이었다.

• Journal of the Korean Institute of Intelligent Systems
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• v.11 no.4
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• pp.354-358
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• 2001

This paper presents a fuzzy neural network model which solves the underutilization problem. This fuzzy neural network has both stability and flexibility because it uses the control structure similar to AHT(Adaptive Resonance Theory)-l neural network. And this fuzzy nenral network does not need to initialize weights and is less sensitive to noise than ART-l neural network is. The learning rule of this fuzzy neural network is the modified and fuzzified version of Kohonen learning rule and is based on the fuzzification of leaky competitive leaming and the fuzzification of conditional probability. The similarity measure of vigilance test, which is performed after selecting a winner among output neurons, is the relative distance. This relative distance considers Euclidean distance and the relative location between a datum and the prototypes of clusters. To compare the performance of the proposed fuzzy neural network with that of Kohonen Self-Organizing Feature Map the IRIS data and Gaussian-distributed data are used.