• Proceedings of the Korean Environmental Health Society Conference
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• 2004.06a
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• pp.139-141
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• 2004

Emission of volatile organic compounds (VOCs) are one of the popular issues of air pollution in Korea, especially in Ulsan city, where much chemical plants are located. It is necessary to detect the VOCs precisely in order to control the air pollution during the plant operation. In general, to examine the concentration of VOCs, gas chromatography (GC) is used. However, most plant operators are using the easy operating handy VOCs detector, which is imported, because GC is difficult to treat and the installation price is high although it is very useful equipment. Therefore, the development of the VOCs detector becomes one of the urgent issues. In this study, sensing characteristics of selected VOCs for the development of VOCs detector was investigated. Semiconductor sensor and several VOCs such as aliphatic, aromatic, and non-homogeneous hydrocarbons were used for the experiment. Through the various experiments, sensor used in the experiment has shown high linearity and sensitivity for most VOCs in the range of 1 -500 ppm concentration.

• Journal of Biomedical Engineering Research
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• v.16 no.2
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• pp.129-138
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• 1995

High-energy and high-dose X-ray and electron beam have been used in radiation therapy after developing particle accelerators. It is recommended to irradiate patients exect real dose for improving therapy effectiveness by International Committee on Radiation Units and Measurement. The radiation detector for daily beam checks of medical accelerators is described. Using thirteen silicon diodes, we have designed the diode detector providing information about calibration, beam symmetry, flatness, stability variation according to radiation damage, time and general quality assurance for both photon and eletron beams. we also compared these measurement values with those of using ionization chamber, film and semiconductor dosimeter.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.2
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• pp.151-156
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• 2008

Many kinds of mass spectrometer type leak detectors have been widely used for detecting leak of vacuum processes in semiconductor and display industries etc. The leak detectors should be often calibrated by the permeation type standard leak in order to ensure accurate and reproducible leak measurement. We have developed a comparative calibration system for permeation type standard leak by using mass spectrometer type leak detector and specification of the calibration method. Following this technique the reliable calibration for leak standard ran be performed even in fields.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.176-176
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• 2007

Flat-panel direct conversion detectors used in compound substance of semiconductor are being studied for digital x-ray imaging. Recently, such detectors are deposited by physical vapor deposition(PVD) generally. But, most of materials (HgI2, PbI2, TlBr, PbO) deposited by PVD have shown difficult fabrication and instability for large area x-ray imaging. Consequently, in this paper, we propose applicable potentialities for screen printing method that is coated on a substrate easily. It is compared to electrical properties among semiconductors such as $HgI_2$, $PbI_2$, PbO, HgBrI, InI, and $TlPbI_3$ under investigation for direct conversion detectors. Each film detector consists of an ~25 to $35\;{\mu}m$ thick layer of semiconductor and was coated onto the substrate. Substrates of $2cm{\times}2cm$ have been used to evaluate performance of semiconductor radiation detectors. Dark current, sensitivity and physics properties were measured. Leakage current of $HgI_2$ as low as $9pA/mm^2$ at the operation bias voltage of ${\sim}1V/{\mu}m$ was observed. Such a value is not better than PVD process, but it is easy to be fabricated in high quality for large area x-ray Imaging. Our future efforts will concentrate on optimization of growth of film thickness that is coated onto a-Si TFT array.

• Nuclear Engineering and Technology
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• v.41 no.5
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• pp.723-728
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• 2009

The response property of the CZT detector ($5{\times}5{\times}5\;mm^3$), widely used in photon spectroscopy, was evaluated by considering the charge collection efficiency, which depends on the interaction position of incident radiation, A quantitative analysis of the energy spectra obtained from the CZT detector was also performed to investigate the tail effect at the low energy side of the full energy peak. The collection efficiency of electrons and holes to the two electrodes (i.e., cathode and anode) was calculated from the Hecht equation, and radiation transport analysis was performed by two Monte Carlo codes, Geant4 and MCNPX. The radiation source was assumed to be 59.5 keV gamma rays emitted from a $^{241}Am$ source into the cathode surface of this detector, and the detector was assumed to be biased to 500 V between the two electrodes. Through the comparison of the results between the Geant4 calculation considering the charge collection efficiency and the ideal case from MCNPX, an pronounced difference of 4 keV was found in the full energy peak position. The tail effect at the low energy side of the full energy peak was confirmed to be caused by the collection efficiency of electrons and holes. In more detail, it was shown that the tail height caused by the charge collection efficiency went up to 1000 times the pulse height in the same energy bin at the calculation without considering the charge collection efficiency. It is, therefore, apparent that research considering the charge collection efficiency is necessary in order to properly analyze the characteristics of CZT detectors.

• Proceedings of the KIEE Conference
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• 1999.11c
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• pp.754-756
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• 1999

In this paper, we have developed a high-sensitivity SNRD(Semiconductor Nuclear Radiation Detector) using silicon PIN photodiode. The SNRD is constructed with silicon PIN photodiode(S3590-05), preamplifier and shaping amplifier. To show the effectiveness of SNRD, nuclear radiation experiments are conducted with $\gamma$-ray Ba-133, Cs-137 and Co-60. The SNRD is different in characteristics of the energy spectrum to scintillation detectors. However, the SNRD have a good linearity on $\gamma$-ray energy and activity. The results of this paper can be applied to electronic personal dosimeter.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.3
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• pp.352-358
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• 2016

A 5-phase phase-locked loop (PLL) for USB2.0 applications was implemented by using an all-synthesis technique. The length of the time-to-digital converter for the fine phase detector was halved by the operation of a coarse phase detector that uses 5-phase clocks. The maximum time difference between the rising edges of two adjacent-phase clocks was 6 ps at 480 MHz. The PLL chip in a 65-nm process occupies $0.038mm^2$, consumes 4.8 mW at 1.2 V. The measured rms and peak-to-peak output jitters are 8.6 ps and 45 ps, respectively.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.138-140
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• 2007

A novel AC-DC switching technology is suggested without inductors for one-chip semiconductor. The suggested converter consists of a rectifier diodes, AC source level detector, switching control, detector of over-current and voltage, feedback controller and switching block, The key technology of the proposed AC-DC converting methode is detecting of the low level voltage for AC voltage, power control transistor and rectifying of DC level. The measurement results with commercial devices show that the converter has power efficiency of 66.5% for DC 12V 0.24A and the standby power is 49.58mW at AC 110V.

• Korean Journal of Optics and Photonics
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• v.8 no.2
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• pp.165-168
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• 1997

We have constructed a scanning confocal microscope using a 780 nm semiconductor laser, an actuator of a compact disk player and a quad-detector. This device detects heights and characteristics of a surface. The laser focus was located at the surface of a sample by using the error signal obtained by a quad-dector, and the current supplied to the actuator for lens was displayed as a height. The materials of a surface were classified according to reflected total intensities and was displayed by different color in a monitor. The device has very samll dimensions of 30 mm$\times$20 mm$\times$20 mm and scan field is 1.6 mm$\times$1.6mm. We obtained two images, one using only reflected light and the other using an error signal from a quad-detector and compared these two images.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.10
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• pp.1163-1171
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• 2007

In this paper, the design techniques required to design heterodyned OPLL such as frequency-phase deference detector, loop filter and phase noise of semiconductor laser are presented. Through the experiments with the calculated parameters, we confirmed that the frequency-phase difference detector simply develops an error component that is proportional to the frequency-phase difference between heterodyned optical signals. The achieved frequency-phase locking range of the input laser diode frequency is around ${\pm}150MHz$. This paper describes the details of the designed as well as experimental results.