• Journal of the Korean Society of Radiology
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• v.15 no.4
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• pp.463-472
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• 2021

Demand for examinations using transvaginal transducer with high frequencies is increasing to observe pelvic organs in gynecological ultrasound tests. However, the quality control of the replacement probe in clinical trials is not properly implemented and the evaluation criteria have not been established. Therefore, 58 transvaginal transducers and 20 convex transducers were applied to the ATS-539 ultrasound phantom for 20 ultrasound devices currently in clinical use to obtain their respective images and measure them quantitatively and qualitatively. For quantitative measurements, vertical measurement, horizontal measurement, and focal zone and qualitative measurements, dead zone, axial·lateral resolution, sensitivity, functional resolution, gray scale·dynamic range were performed. Quantitative statistical analysis showed significant differences between the two transducers in the lateral measurement and local area (p<0.05). qualitative comparative analysis showed differences in sensitivity and functional resolution. This occurs due to the difference in frequency between transducers and the transducer's injection geometry. Based on the above experiments, the tolerance for horizontal measurement is raised to 10% (±8 mm), the tolerance for sensitivity is observed up to 6 cm deep, which is 12 cm deep,which is the level of the third quartile (75%). The permissible range of functional resolution is up to 6 (12 cm), 6 (12 cm), 11 (11 cm), 9 (9 cm), 6 (6 cm) target, which is the level of the third quartile (75%). It is considered reasonable to adjust the depth of targets in gray scale·dynamic range to measure at a depth of 2 cm, which is 50% of the depth of 4 cm. As above, the criteria for evaluating the quality of transvaginal transducer for use in the past have been proposed and it is expected that this study will be used as a basic data for the production of phantom exclusively for transvaginal transducer in the future.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.35 no.6
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• pp.109-120
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• 2023

The High-Frequency Radar (HFR) is an equipment designed to measure real-time surface ocean currents in broad maritime areas.It emits radio waves at a specific frequency (HF) towards the sea surface and analyzes the backscattered waves to measure surface current vectors (Crombie, 1955; Barrick, 1972).The Seasonde HF Radar from Codar, utilized in this study, determines the speed and location of radial currents by analyzing the Bragg peak intensity of transmitted and received waves from an omnidirectional antenna and employing the Multiple Signal Classification (MUSIC) algorithm. The generated currents are initially considered ideal patterns without taking into account the characteristics of the observed electromagnetic wave propagation environment. To correct this, Antenna Pattern Measurement (APM) is performed, measuring the strength of signals at various positions received by the antenna and calculating the corrected measured vector to radial currents.The APM principle involves modifying the position and phase information of the currents based on the measured signal strength at each location. Typically, experiments are conducted by installing an antenna on a ship (Kim et al., 2022). However, using a ship introduces various environmental constraints, such as weather conditions and maritime situations. To reduce dependence on maritime conditions and enhance economic efficiency, this study explores the possibility of using unmanned aerial vehicles (drones) for APM. The research conducted APM experiments using a high-frequency radar installed at Dangsa Lighthouse in Dangsa-ri, Wando County, Jeollanam-do. The study compared and analyzed the results of APM experiments using ships and drones, utilizing the calculated radial currents and surface current fields obtained from each experiment.

• 한국해양학회지
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• v.30 no.6
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• pp.550-564
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• 1995

The temporal and spatial characteristics of wind fields over the neighbouring seas of the Korean peninsula are investigated using 10-years daily wind data during 1978${\sim}$1987 which have been spatially smoothed and low-pass filtered. Long term annual and monthly means are examined for synoptic patterns and spectral analyses are made for temporal variability and spatial coherence. Spatial patterns of the annual mean wind stress and curl have a strong resemblance with those of monthly means during the winter season. Two outstanding periodicities are observed at 1 and 2 cycles per year. The synoptic winds over the study area are highly coherent at both the annual and semi-annual periodicities. However, each basin has its own characteristic spatial pattern. For instance, the prevailing wind during the winter season is northerIy over the northern East Sea (ES), Yellow Sea (YS), and northern East China Sea (ECS), while it is northwesterly over the southern ES and northesterly over the northern ES and southern ECS. At the same time, the wind stress curl is positive over the northern ES and southern ECS, while it is negative over the southern ES, YS and northern ECS. On the other hand, the wind field during the summer season, with its strength being much reduced, is completely different from that during the winter season, and frequent passage of tropical storms provokes large temporal variability over ECS. One remarkable point is that the annual cycle, dominated by the Siberian High, tends to propagate from northeast to southwest, i.e., from northern 25 toward southern ES, YS and ECS, while the semi-annual cycle propagates in the opposite direction, from southwest to northeast. The semi-annual periodicity may reflect development of extratropical cyclones in spring and fall which frequently cross the Korean peninsula. In higher frequencies, there are no dominant periodicities, but local winds over YS and ES are highly correlated for frequencies larger than 0.1 cycles per day and phase difference increases linearly with frequency. This linear increase of phase corresponds to phase speed of 550 and 730 km/d at 0.1 and 0.3 cpd, respectively, The phase speed is apparently coincident with moving speed of extratropical cyclones across the Korean peninsula in the west-east direction.

• Radiation Oncology Journal
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• v.24 no.4
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• pp.300-308
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• 2006

$\underline{Purpose}$: To develop a wireless CCTV system in semi-beam's eye view (BEV) to monitor daily patient setup in radiation therapy. $\underline{Materials\;and\;Methods}$: In order to get patient images in semi-BEV, CCTV cameras are installed in a custom-made acrylic applicator below the treatment head of a linear accelerator. The images from the cameras are transmitted via radio frequency signal (${\sim}2.4\;GHz$ and 10 mW RF output). An expected problem with this system is radio frequency interference, which is solved utilizing RF shielding with Cu foils and median filtering software. The images are analyzed by our custom-made software. In the software, three anatomical landmarks in the patient surface are indicated by a user, then automatically the 3 dimensional structures are obtained and registered by utilizing a localization procedure consisting mainly of stereo matching algorithm and Gauss-Newton optimization. This algorithm is applied to phantom images to investigate the setup accuracy. Respiratory gating system is also researched with real-time image processing. A line-laser marker projected on a patient's surface is extracted by binary image processing and the breath pattern is calculated and displayed in real-time. $\underline{Results}$: More than 80% of the camera noises from the linear accelerator are eliminated by wrapping the camera with copper foils. The accuracy of the localization procedure is found to be on the order of $1.5{\pm}0.7\;mm$ with a point phantom and sub-millimeters and degrees with a custom-made head/neck phantom. With line-laser marker, real-time respiratory monitoring is possible in the delay time of ${\sim}0.17\;sec$. $\underline{Conclusion}$: The wireless CCTV camera system is the novel tool which can monitor daily patient setups. The feasibility of respiratory gating system with the wireless CCTV is hopeful.

• Journal of the Korean Vacuum Society
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• v.22 no.5
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• pp.238-244
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• 2013

Doping process using laser is an important process in fabrication of solar cell for heat treatment. However, the process of using the furnace is difficult to form a selective emitter doping region. The case of using a selective emitter laser doping is required an expensive laser equipment and induce the wafer's structure damage due to high temperature. This study, we fabricated a new costly plasma source. Through this, we research the selective emitter doping. We fabricated that the atmospheric pressure plasma jet injected Ar gas is inputted a low frequency (a few tens kHz). We used shallow doping wafers existing PSG (Phosphorus Silicate Glass) on the shallow doping CZ P-type wafer. Atmospheric plasma treatment time was 15 s and 30 s, and current for making the plasma is 40 mA and 70 mA. We investigated a doping profile by using SIMS (Secondary Ion Mass Spectroscopy) and we grasp the sheet resistance of electrical character by using doping profile. As result of experiment, prolonged doping process time and highly plasma current occur a deeper doping depth, moreover improve sheet resistance. We grasped the wafer's surface damage after atmospheric pressure plasma doping by using SEM (Scanning Electron Microscopy). We check that wafer's surface is not changed after plasma doping and atmospheric pressure doping width is broaden by increase of plasma treatment time and current.

• Progress in Medical Physics
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• v.10 no.1
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• pp.17-22
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• 1999

INJ-I, INJ-E, PFN, BMI, and PRF were selected among the various factors which constitute a digital linear accelerator to find effects on the dose distribution by changing current and voltage within the permitted scale which Mevatron automatically maintained. We measured the absorbed dose using an ion chamber, analyzed the waveform of beam output using an oscilloscope, and measured symmetry and flatness using a dosimetry system. An RFA plus (Scanditronix, Sweden) device was used as a dosimetry system. Then an 0.6cc ion chamber (PR06C, USA), an electrometer (Capintec192, USA), and an oscilloscope (Tektronix, USA) were employed to measure the changes on the dose distribution characteristics by changing the beam-tuning parameters. When the currents and the voltages of INJ-I, INJ-E, PFN, BMI, and PRF were modified, we were able to see the notable change on the dose rate by examining the change of the output pulse using the oscilloscope and by measuring them using the ion chamber. However, the results of energy and flatness graph from RF A plus were almost identical. The factors had fine differences: INJ-I, INJ-E, PFN, BMI, and PRF had 0.01∼0.02% differences in D10/D20, 0.1∼0.2 % differences in symmetry, and 0.1∼0.4% differences in flatness. Since Mevatron controlled itself automatically to keep the reference value of the factor, it was not able to see large differences in the dose distribution. There were fine differences on the dose rate distribution when the voltage and the currents of the digitized factors were modified Nonetheless, a basic operational management information was achieved.

• Clinical and Experimental Pediatrics
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• v.46 no.10
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• pp.996-1002
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• 2003

Purpose : In Rett syndrome patients, the incidence of sudden death is greater than that of the general population, and cardiac electrical instability including fatal cardiac arrhythmia is a main suspected cause. In this study, we are going to find out the possible cause of the higher risk of sudden death in Rett patients by the evaluation of heart rate variability, a marker of cardiac autonomic activity and corrected QT intervals. Methods : Diagnosis of Rett syndrome was made by molecular genetic study of Rett syndrome (MECP2 gene) or clinical diagnostic criteria of Rett syndrome. Heart rate variability and corrected QT intervals were measured by 24 h-Holter study in 12 Rett patients, and in 30 age-matched healthy children with chief complaints of chest pain or suspected heart murmurs. The were compared with the normal age-matched control. Results : Patients with total Rett syndrome, classic Rett syndrome, and Rett variants had significantly lower heart rate variability(especially rMSSD)(P<0.05) and longer corrected QT intervals than age-matched healthy children(P<0.05). Sympathovagal balance expressed by the ratio of high to low frequency(LF/HF ratio) also showed statistically significant differences between the three groups considered(P<0.05). Conclusion : A significant reduction of heart rate variability, a marker of autonomic disarray, suggests a possible explanation of cardiac dysfunction in sudden death associated with Rett syndrome.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.95-95
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• 2018

강재의 방식법 중 도장은 부식을 억제하는데 효과적이고 편리한 방법으로 선박 및 해양 강 구조물의 방식법으로 사용되고 있다. 한편, 강 구조물의 효율적인 유지관리를 위해서는 방식 도장의 도막 열화도를 평가하고 잔존 수명을 예측하여 최적 시기에 보수도장 혹은 재도장하는 것이 필요하다. 일반적으로 선박 및 해양구조물에 적용되는 도막의 방식 성능 평가 방법으로 해수 침지 시험, 염수 분무 시험, 옥외 폭로 시험 등이 있다. 그러나 이러한 시험들은 그 시험 방법에 따라서 정량적인 평가에 한계가 있음은 물론 장기간 소요되는 등 곤란한 문제점이 있다. 그러므로 선박 및 해양구조물을 비롯하여 교량, 각종 강 구조물의 도장 방식에 사용되는 방식용 도료의 성능을 단기간에 적절하게 평가할 수 있는 가속시험법이 제시되며 연구-사용되고 있다. 그 중 도막 방식 성능을 보다 효율적, 비파괴적, 정량적으로 평가할 수 있는 임피던스 분광법(EIS)과 같은 전기화학적 방법은 상대적으로 시험 기간을 크게 단축시킬 수 있고, 대상 방식 도장의 미세한 성능 차이도 분별 가능하다는 장점이 있다[1]. 따라서 본 연구에서는 선박 및 해양구조물 등 가혹한 부식환경에서 강력한 내구성을 가질 수 있도록 다양한 종류의 표면처리 도장 시편을 제작하여 자외선 조사-염수분무-침지환경 등의 열악한 환경조건 하에서 부식-열화 촉진 시험을 실시하였다. 그리고 그 촉진 열화 과정에서 도막의 외관 상태를 관찰 분석함은 물론 전기화학적 임피던스 분광법을 병행 측정하며 그 표면막의 부식 및 도막 열화도를 비교-종합 평가하였다.본 연구에 사용된 시편은 Al 및 Zn 도금 강판에 에폭시, 에폭시-실리콘 우레탄, 에폭시-우레탄 도장 시편으로 Scribe, No Scribe 및 비교재 Al 및 Zn 도금 시편으로 분류하여 각각 실험을 진행하였다. 즉, 도막 열화 시험은 복합 노화 시험법으로 UV 조사 36 시간(ASTM G53), 염수분무 32 시간(ISO 7253), 수분 응축 10 시간을 1 Cycle로 100 Cycle(7800 시간) 동안 실험을 진행하였다. 이때 도막 열화도 평가는 전기화학적 임피던스 분광법을 이용하여 각 실험 조건별로 주파수에 따른 임피던스(Z) 값을 평가하였다. 즉, 상온 $25^{\circ}C$의 3.5% NaCl 100 ml 수용액에 작동 전극(Working Electrode)과 구리 도선을 통해 연결하였고, 노출 면적은 $1cm^2$로 일정하게 유지 하였으며, 상대 전극(Counter Electrode)은 탄소봉, 기준 전극(Reference Electrode)으로 포화카로멜전극(Saturated Calomel Electrode)을 사용하여 측정하였다. No Scribe 시편의 경우에는 Al 기판 에폭시-실리콘 우레탄 도장 시편이 우수한 도막 저항성을 나타내었으며, 에폭시-우레탄 도장시편은 23사이클 이후의 저항값이 가장 낮게 나타났다. Zn 기판의 경우는 에폭시, 에폭시-실리콘 우레탄, 에폭시-우레탄 도장 시편 모두 저항 값이 유사하였으며, Al 및 Zn 도금 시편은 도장 처리된 시편에 비해 훨씬 낮은 저항 값을 보였다. 또한 Scribe 시편의 경우에는 Al 기판 에폭시-실리콘 우레탄 도장 시편에서 높은 초기 저항 값을 보였으며, 23 사이클 후의 저항 값은 세 종류의 도막에서 약 1~0.1 Gohm 으로 나타났다. 그리고 Zn 기판 에폭시-실리콘 우레탄 도장 시편에서 가장 낮은 도막 저항 값이 나타났다. 이상의 실험을 통해서 본 연구 내용은 실내촉진시험으로 선박 및 해양 강 구조물에 사용되는 다양한 종류의 도막의 열화도를 평가하는 기초 설계 지침으로 응용될 수 있을 것으로 사료된다. 한편, 도막은 노출 환경에 따라 방식 성능이 다르므로 실제 도막의 사용환경을 고려하여 도장 사양별 적용 부위에 따른 적정 가속 실험 방법을 선정할 필요가 있다고 사료된다.

• Science of Emotion and Sensibility
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• v.8 no.1
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• pp.47-54
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• 2005

This study is aimed to inspect how the different sensitivities in Behavioral activation system(BAS) and behavioral inhibition system(BIS) modulate on the properties of physiological responses stimulated by positive or negative affective sound. We measured the electroencephalogram(EEG) and electrocardiogram (ECG) of 32 students, consisted of four groups depending on the BAS and BIS sensitivities, during listening to meditation music or noise. The EEG was recorded at Fpl and Fp2 sites and Power spectral density(PSD) of HRV was derived from the ECG, and the power of HRV was calculated for 3 major frequency ranges(low frequency[LF], medium frequency and high frequency[HF]). After listening to music or noise, subjects reported the affect induced by the sound. For EEG, the power in the alpha band at Fp2, especially in the alpha-2 band(9.0-11.0 Hz) increased during the subjects listening to music, while the power at Fpl increased during noise. During listening to meditation music, there is a tendency that the left-sided activation in prefrontal cortex(PFC) is positively correlated with the difference of BAS(Z)-BIS(Z). During listening to noise, there is a tendency that the right-sided activation in PFC is dominant in case any of the sensitivity of BAS or BIS is high. For HRV, we found that the index of MF/(LF+HF), during listening to music, was higher significantly in the individuals with a low BIS but high BAS than in the individuals with a low sensitivity both BIS and BAS individuals. With high BIS, regardless of the BAS sensitivity, the difference of this index values was not significant. From these results we suggest that the physiological responses of different individuals in BAS and BIS react differently under the same emotionally provocative challenge.

• Geophysics and Geophysical Exploration
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• v.1 no.2
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• pp.127-135
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• 1998

The Born approximation is widely used for solving the complex scattering problems in electromagnetics. Approximating total internal electric field by the background field is reasonable for small material contrasts as long as scatterer is not too large and the frequency is not too high. However in many geophysical applications, moderate and high conductivity contrasts cause both real and imaginary part of internal electric field to differ greatly from background. In the extended Born approximation, which can improve the accuracy of Born approximation dramatically, the total electric field in the integral over the scattering volume is approximated by the background electric field projected to a depolarization tensor. The finite difference and elements methods are usually used in EM scattering problems with a 2D model and a 3D source, due to their capability for simulating complex subsurface conductivity distributions. The price paid for a 3D source is that many wavenumber domain solutions and their inverse Fourier transform must be computed. In these differential equation methods, all the area including homogeneous region should be discretized, which increases the number of nodes and matrix size. Therefore, the differential equation methods need a lot of computing time and large memory. In this study, EM modeling program for a 2D model and a 3D source is developed, which is based on the extended Born approximation. The solution is very fast and stable. Using the program, crosshole EM responses with a vertical magnetic dipole source are obtained and the results are compared with those of 3D integral equation solutions. The agreement between the integral equation solution and extended Born approximation is remarkable within the entire frequency range, but degrades with the increase of conductivity contrast between anomalous body and background medium. The extended Born approximation is accurate in the case conductivity contrast is lower than 1:10. Therefore, the location and conductivity of the anomalous body can be estimated effectively by the extended Born approximation although the quantitative estimate of conductivity is difficult for the case conductivity contrast is too high.