• Progress in Medical Physics
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• v.9 no.1
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• pp.11-21
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• 1998

Circular metal electrodes were vacuum-deposited with chromium on the both sides of Teflon-FEP and PET film characteristic of electret and the physical properties of the two polymers were observed during an irradiation by gamma-ray from $\^$60/Co. With the onset of irradiation of output 25.0 cGy/min the induced current increased rapidly for 2 sec, reached a maximum, and subsequently decreased. A steady-state induced current was reached about in 60 second. The dielectric constant and conductivity of Teflon-FEP were changed from 2.15 to 18.0 and from l${\times}$l0$\^$-17/ to 1.57${\times}$10$\^$-13/ $\Omega$-$\^$-1/cm$\^$-1/, respectively. For PET the dielectric constant was changed from 3 to 18.3 and the conductivity from 10$\^$-17/ to 1.65${\times}$10$\^$-13/ $\Omega$-$\^$-1/cm$\^$-1/. The increase of the radiation-induced steady state current I$\^$c/, permittivity $\varepsilon$ and conductivity $\sigma$ with output(4.0 cGy/min, 8.5 cGy/min, 15.6 cGy/min, 19.3 cGy/min) was observed. A series of independent measurements were also performed to evaluate reproducibility and revealed less than 1% deviation in a day and 3% deviation in a long term. Charge and current showed the dependence on the interval between measurements, the smaller the interval was, the bigger the difference between initial reading and next reading was. At least in 20 minutes of next reading reached an initial value. It may indicate that the polymers were exhibiting an electret state for a while. These results can be explained by the internal polarization associated with the production of electron-hole pairs by secondary electrons, the change of conductivity and the equilibrium due to recombination etc. Heating to the sample made the reading value increase in a short time, it may be interpreted that the internal polarization was released due to heating and it contributed the number of charge carriers to increase when the samples was again irradiated. The linearity and reproducibility of the samples with the applied voltage and absorbed dose and a large amount of charge measured per unit volume compared with the other chambers give the feasibility of a radiation detector and make it possible to reduce the volume of a detector.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.3
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• pp.13-19
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• 2018

The soldering property of Pb-containing solder(Sn-Pb) and Pb-free solders(Sn-3.0Ag-0.5Cu and Sn-1.0Ag-0.7Cu-1.6Bi-0.2In) for solar combiner box module was compared. The solar combiner box module was composed of voltage and current detecting modules, diode modules, and other modules. In this study, solder paste printability, printing shape inspection, solder joint property, X-ray inspection, and shear force measurements were conducted. For optimization of Pb-free soldering process, step 1 and 2 were divided. In the step 1 process, the printability of Pb-containing and Pb-free solder alloys were estimated by using printing inspector. Then, the relationship between void percentages and shear force has been estimated. Overall, the property of Pb-containing solder was better than two Pb-free solders. In the step 2 process, the property of reflow soldering for the Pb-free solders was evaluated with different reflow peak temperatures. As the peak temperature of the reflow process gradually increased, the void percentage decreased by 2 to 4%, but the shear force did not significantly depend on the reflow peak temperature by a deviation of about 0.5 kgf. Among different surface finishes on PCB, ENIG surface finish was better than OSP and Pb-free solder surface finishes in terms of shear force. In the thermal shock reliability test of the solar combiner box module with a Pb-free solder and OSP surface finish, the change rate of electrical property of the module was almost unchanged within a 0.3% range and the module had a relatively good electrical property after 500 thermal shock cycles.

• The Journal of the Petrological Society of Korea
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• v.10 no.3
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• pp.179-189
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• 2001

The determination of trace concentration of U, Th and Pb was carried out for chemical dating of zircon and monazite by electron microprobe. Detection limit and error range should be considered to measure characteristic X-rays of M-line from those minerals, which are low in the ionization of atom and low peak intensity in the spectrum. The element of U, Th and Pb were simultaneously measured with 3 spectrometers equipped with PET crystal to reduce a total counting time and error due to drift of instrumental operating condition. Detection limit could be improved from increase of the peak/background ratio through adjusting pulse height analyzer about 1000 mv baseline. Under permissible maximum analytical conditions, theoretical detection limit of U, Th and Pb is down to 30 ppm (99% confidence level). The analytical result was maintained at a relative error $\pm$10% ($2{\sigma}$) in 800 ppm Pb, $\pm$5% ($2{\sigma}$) in 2330 ppm U and $\pm$10% ($2{\sigma}$) in dating from a single measurement of zircon at 15 keV and 100 nA. However, for the precise dating of zircon and monazite, if it is considered a 3 $\mu\textrm{m}$ spatial resolution, <100 ppm ($3{\sigma}$) detection limit and <$\pm$10% ($2{\sigma}$) relative error, optimum analytical conditions are given as 15~20 keV accelerating voltage, 100~200 nA beam current and 300~1200 sec total counting time. To reduce material damage by high current, there is need to be up to 3~5 $\mu\textrm{m}$ of electron beam diameter, or to use arithmetic average of multiple measuring at a shorter counting time. A younger or relatively low concentration rocks can be dated chemically by lower detection limit and improved precision resulted from increase of current and measuring time.

• Science of Emotion and Sensibility
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• v.13 no.4
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• pp.703-710
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• 2010

In this study, a tactile stimulator was developed to resolve some problems from the previous version of the system such as system configuration, inappropriate stimulation control and additional problems. The developed tactile stimulator consists of control unit, drive unit and vibrator unit. The control unit was controlled by E-Prime software to generate appropriate vibration pulses. The drive unit supplies enough energy to the vibrator to generate effective stimulation pulses. The vibrator unit consists of small coin type vibrator and velcro, and was made to be attached at the hand easily. The developed tactile stimulator was designed by small-size, light-weight, low-power, simple-fabrication, max 35 channels and little delay time from instruction signal of E-Prime software to vibrator. The duration and magnitude of stimulation was controlled by 10 grades and the problems concerning stimulation control were compensated by wideband frequency ranges. Additionally, the electrical safety was ensured by low voltage operation. Vibrator was made to be attached on finger as well as on any part of the subject. Since this tactile stimulator is developed based on E-Prime software which is widely used in cognitive science, it is believed that this stimulator be suitable for the wide application of cognitive science study.

• Journal of Chest Surgery
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• v.34 no.9
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• pp.698-703
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• 2001

Background: Endovascular stent-graft insertion in aortic diseases is now generally accepted as an attractive alternative treatment modality. We reviewed our clinical experiences of endovascular stent-graft insertion in thoracic aorta. Material and Method: Since 1995, we performed 8 cases of endovasclar stent-graft insertion. Preoperative diagnoses were aortic aneurysms in 4, traumatic aortic ruptures in 3, and ruptured aortic pseudoaneurysm in 1. All procedures were performed in angiography room with the guidance of fluoroscopy. The stent-graft device is a custom-made 0.35mm thickness Z-shaped stainless steel wires, intertwined with each other using polypropylene suture ligation. It is covered with expanded Dacron vascular graft. Result: All procedures were performed successfully. Follow-up studies revealed 2 minimal perigraft leakages. There was no significant leakage or graft migration. 2 patients expired due to multiple organ failure and fungal sepsis. Other survivors(6) are doing well. Conclusion: Endovascular stent-graft insertion is relatively saft and effective treatment modality in the managment of various types of aortic diseases. In may be an effective alternative in aortic diseases of great surgical risk.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.5
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• pp.87-97
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• 2016

This work proposes a time-shared 10b DAC based on a two-step resistor string to minimize the effective area of a DAC channel for driving each AMOLED display column. The proposed DAC shows a lower effective DAC area per unit column driver and a faster conversion speed than the conventional DACs by employing a time-shared DEMUX and a ROM-based two-step decoder of 6b and 4b in the first and second resistor string. In the second-stage 4b floating resistor string, a simple current source rather than a unity-gain buffer decreases the loading effect and chip area of a DAC channel and eliminates offset mismatch between channels caused by buffer amplifiers. The proposed 1-to-24 DEMUX enables a single DAC channel to drive 24 columns sequentially with a single-phase clock and a 5b binary counter. A 0.9pF sampling capacitor and a small-sized source follower in the input stage of each column-driving buffer amplifier decrease the effect due to channel charge injection and improve the output settling accuracy of the buffer amplifier while using the top-plate sampling scheme in the proposed DAC. The proposed DAC in a $0.18{\mu}m$ CMOS shows a signal settling time of 62.5ns during code transitions from '$000_{16}$' to '$3FF_{16}$'. The prototype DAC occupies a unit channel area of $0.058mm^2$ and an effective unit channel area of $0.002mm^2$ while consuming 6.08mW with analog and digital power supplies of 3.3V and 1.8V, respectively.

• Korean Journal of Animal Reproduction
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• v.26 no.1
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• pp.79-85
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• 2002

We investigated the optimal concentration and exposure time of cycloheximide(CHX) on development of activated porcine oocytes following electrical pulse(EP). After 42~44 h maturation, oocytes were treated with 0.1% hyaluronidase, and denuded cumulus cells by pipetting. Oocytes were stimulated by electric pulse (1.2 kV/cm, 30 $\mu$sec, 1 pulse) or incubated for 3, 5 and 7 h in cycloheximide (1, 5 and 10 $\mu\textrm{g}$/$m\ell$, respectively) following electric pulse, and cultured for 8 days. Cleavage rate of oocytes activated with 10 $\mu\textrm{g}$/$m\ell$ CHX following EP was significantly (P＜0.05) higher than those of 1 $\mu\textrm{g}$/$m\ell$ (86.8% vs. 74.4%). The developmental competence of oocytes incubated to 5 $\mu\textrm{g}$/$m\ell$ of CHX was significantly (P＜0.05) higher development to blastocysts (13.3%), compared with 10 $\mu\textrm{g}$/$m\ell$ of CHX (5.6%). When the oocytes were activated with 5$\mu\textrm{g}$/$m\ell$ CHX for 3, 5, and 7 h following EP, the cleavage rate of oocytes in 5 h group(86.6%) was significantly (P＜0.05) higher than that in 3 h group(73.2%). The developmental rate of oocytes to morula in 5 and 7 h groups(26.7% and 16.4%) were significantly (P＜0.05) high than that in 3 h group(14.5%). Matured oocytes were activated with electric pulse (EP) or electric pulse combined with cycloheximide (EP + CHX) and cultured for 8 days. The rate of cleavage and development to blastocyst (80.1% and 11.6%) of activated with EP group were similar to EP combined with CHX group. When activated with EP or EP combined with CHX, the mean cell number of blastocysts were less in the activated with EP (18.67$\pm$5.53) than in the activated EP combined CHX (20.71$\pm$6.16), but not significantly different. This results suggest that, when the porcine oocytes were activated with CHX following EP, the developmental rate of activated oocytes can be improved by treated with a concentration of 5 $\mu\textrm{g}$/$m\ell$ CHX for 5 h exposure time.

• Journal of radiological science and technology
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• v.32 no.3
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• pp.299-306
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• 2009

Purpose : To compare radiation dose for coronary CT angiography (CTA) obtained with 6 examination protocols such as a retrospectively ECG gated helical scan, a prospectively ECG gated sequential scan, low kVp technique, and cardiac dose modulation technique. Materials and Methods : Coronary CTA was performed by using 6 current clinical protocols to evaluate effective dose and organ dose in primary beam area with anthropomorphic female phantom and glass dosimetric system in 64 channel multi-detector CT. After acquiring topograms of frontal and lateral projection with 80 kVp and 10 mA, main coronary scan was done with 0.35 sec tube rotation time, 40 mm collimation ($0.625\;mm{\times}64\;ea$), small scan field of view (32 cm diameter), 105 mm scan length. Heart beat rate of phantom was maintained 60 bpm in ECG gating. In constant mAs technique 120 kVp, 600 mA was used, and 100 kVp for low kVp technique. In a retrospectively ECG gated helical CT technique 0.22 pitch was used, peak mA (600 mA) was adopted in range of $40{\sim}80%$ of R-R interval and 120mA(80% reduction) in others with cardiac dose modulation. And 210 mAs was used without cardiac dose modulation. In a prospectively ECG gated sequential CT technique data were acquired at 75% R-R interval (middle diastolic phase in cardiac cycle), and 120 msec additional padding of the tube-on time was used. For effective dose calculation region specific conversion factor of dose length product in thorax was used, which was recommended by EUR 16262. Results : The mean effective dose for conventional coronary CTA without cardiac dose modulation in a retrospectively ECG gated helical scan was 17.8 mSv, and mean organ dose of heart was 103.8 mGy. With low kVp and cardiac dose modulation the mean effective dose showed 54.5% reduction, and heart dose showed 52.3% reduction, compared with that of conventional coronary CTA. And at the sequential scan(SnapShot pulse mode) under prospective ECG gating the mean effective dose was 4.9 mSv, this represents an 72.5% reduction compared with that of conventional coronary CTA. And heart dose was 33.8 mGy, this represents 67.4% reduction. In the sequential scan technique under prospective ECG gating with low kVp the mean effective dose was 3.0 mSv, this represents an 83.2% reduction compared with that of conventional coronary CTA. And heart dose was 17.7 mGy, this represents an 82.9% reduction. Conclusion : In coronary CTA at retrospectively ECG gated helical scan, cardiac dose modulation technique using low kVp reduced dose to 50% above compared with the conventional helical scan. And the prospectively ECG gated sequential scan offers substantially reduced dose compared with the traditional retrospectively ECG gated helical scan.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.321-322
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• 2012

의료용 방사선 장비는 초기의 아날로그 방식의 필름 및 카세트에서 진보되어 현재는 디지털 방식의 DR (Digital Radiography)이 널리 사용되며 그에 관한 연구개발이 활발히 진행되고 있다. DR은 크게 간접방식과 직접방식의 두 분류로 나눌 수 있는데, 간접방식은 X선을 흡수하면 가시광선으로 전환하는 형광체(Scintillator)를 사용하여 X선을 가시광선으로 전환하고, 이를 Photodiode와 같은 광소자로 전기적 신호로 변환하여 방사선을 검출하는 방식을 말하며, 직접 방식은 X선을 흡수하면 전기적 신호를 발생 시키는 광도전체(Photoconductor)를 사용하여 광도전체 양단 전극에 고전압을 인가한 형태를 취하고 있는 가운데, X선이 조사되면 일차적으로 광도전체 내부에서 전자-전공쌍(Electron-hole pair)이 생성된다. 이들은 광도전체 양단의 인가되어 있는 전기장에 의해 전자는 +극으로, 전공은 -극으로 이동하여 아래에 위치한 Active matrix array을 통해 방사선을 검출하는 방식이다. 본 연구에서는 직접방식 X-ray 검출기에서 활용되는 a-Se을 ITO (Indium Thin oxide) glass 상단에 Thermal evaporation증착을 이용하여 두께 $50{\mu}m$, 33 넓이로 증착 시킨 다음, a-Se상단에 Sputtering증착을 이용하여 ITO를 11 cm, 22 cm, $2.7{\times}2.7cm$ 넓이로 증착시켜 상하부의 ITO를 Electrode로 이용하여 직접방식의 X-ray검출기 샘플을 제작하였다. 제작 과정 중 a-Se의 Thermal evaporation증착 시, 저진공 $310^{-3}_{Torr}$, 고진공 $2.210^{-5}_{Torr}$에서 보트의 가열 온도를 두 번의 스텝으로 나누어 증착 시켰다. 첫 번째 스텝 $250^{\circ}C$, 두 번째 스텝은 $260^{\circ}C$의 조건으로 증착하여 보트 내의 a-Se을 남기지 않고 전량을 소모할 수 있었으며, 스텝간의 온도차를 $10^{\circ}C$로 제어하여 균일한 박막을 형성 할 수 있었다. Sputtering증착 시, 저진공 $2.510^{-3}$, 고진공 $310^{-5}$에서 Ar, $O_2$를 사용하여 100 Sec간 플라즈마를 생성시켜 ITO를 증착하였다. 제작된 방사선 각각의 검출기 샘플 양단의 ITO에 500V의 전압을 인가하고, 진단 방사선 범위의 70 kVp, 100 mA, 0.03 sec 조건으로 X-ray를 조사시켜 ITO넓이에 따른 민감도(Sensitivity)와 암전류(Dark current)를 측정하였다. 측정결과 민감도(Sensitivity)는 X-ray샘플의 두께에 따른 $1V/{\mu}m$ 기준 시, 증착된 ITO의 넓이가 11 cm부터 22 cm, $2.7{\times}2.7cm$까지 각각 $7.610nC/cm^2$, $8.169nC/cm^2$, $6.769nC/cm^2$로 22 cm 넓이의 샘플이 가장 높은 민감도를 나타내었으나, 암전류(Dark current)는 $1.68nA/cm^2$, $3.132nA/cm^2$, $5.117nA/cm^2$로 11 cm 넓이의 샘플이 가장 낮은 값을 나타내었다. 이러한 데이터를 SNR (Signal to Noise Ratio)로 합산 하였을 시 104.359 ($1{\times}1$), 60.376($2{\times}2$), 30.621 ($2.7{\times}2.7$)로 11 cm 샘플이 신호 대 별 가장 우수한 효율을 나타냄을 알 수 있었다. 따라서 ITO박막의 면적이 클수록 민감도는 우수하나 그에 따른 암전류의 증가로 효율이 떨어짐을 검증 할 수 있었으며, 이는 ITO면적이 넓어짐에 따른 저항의 증가로 암전류에 영향을 끼침을 할 수 있었다. 본 연구를 통해 a-Se의 ITO 박막 면적에 따른 전기적 특성을 검증할 수 있었다.

• Korean Journal of Microbiology
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• v.37 no.4
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• pp.284-288
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• 2001

Respiratory viruses are one of the most infectious agent in human. Six different respiratory tract viruses were detected from Busan while working on the preventive surveillance in 1997-2000. The isolation rate from suspected specimens were 8.4%. Influenza virus A, B type, parainfluenza virus, adenovirus, mumps virus, and measles virus were examined from throat swabs, serum, and secretions of patients. Influenza A/Sydney/05/97(H3N2)-like, A/Johanesburg/33/94(H3N2)-like, A/Beijing/262/95(H1N1)-like and Influenza B/Beijing/262/95-like, B/Harbin/07/94-like, B/Guangdong/08/93-like were found. Adenovirus serotype 1, 2, 3 and 5 were detected, antibody of mumps both IgM and IgG were shown and outbreaks of measles were confirmed. Different antigenic types of influenza virus were detected every year, one outbreak of parainfluenza in 1999, mumps outbreak in 1999 and 2000, and incidence of measles in 2000 were noticeable. Monthly outbreaks were November through following March with influenza virus, January through June with adenovirus, February through May and December with mumps, April through August and November, December with measles, respectively. The size of isolated viruses were 130 nm with influenza virus B type, non-enveloped, icosahedron with 70 nm with adenovirus, 170 nm with mumps virus and 180 nm with parainfluenza virus in diameter, respectively.