• Korean Journal of Optics and Photonics
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• v.11 no.6
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• pp.390-394
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• 2000

An optical system for iris pattern recognition of the human eye is designed. The lens system is triplet type, and characterized to minimize longitudinal chromatic aberration and Petzval sum. The distance from object to image is 200 mm-300 mm and the effective focal length is 50 mm. Performance of the imaging system is assessed by calculating the ray-fan and spot diagram for Fraunhofer C, d and F line for object height 0 mm, 4 mm and 6 mm. Furthermore, MTFs are calculated. All of the spot sizes are less than 0.05 mm in diameter. The MTF values are higher than 0.5 in the spatial frequency range up to 20 lines/mm for all of the object heights. ights.

• Nuclear Engineering and Technology
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• v.54 no.12
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• pp.4684-4692
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• 2022

Radionuclide identification is an important part of the nuclear material identification system. The development of artificial intelligence and machine learning has made nuclide identification rapid and automatic. However, many methods directly use existing deep learning models to analyze the gamma-ray spectrum, which lacks interpretability for researchers. This study proposes an explainable radionuclide identification algorithm based on the convolutional neural network and class activation mapping. This method shows the area of interest of the neural network on the gamma-ray spectrum by generating a class activation map. We analyzed the class activation map of the gamma-ray spectrum of different types, different gross counts, and different signal-to-noise ratios. The results show that the convolutional neural network attempted to learn the relationship between the input gamma-ray spectrum and the nuclide type, and could identify the nuclide based on the photoelectric peak and Compton edge. Furthermore, the results explain why the neural network could identify gamma-ray spectra with low counts and low signal-to-noise ratios. Thus, the findings improve researchers' confidence in the ability of neural networks to identify nuclides and promote the application of artificial intelligence methods in the field of nuclide identification.

• Journal of Radiation Protection and Research
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• v.43 no.3
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• pp.97-106
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• 2018

Background: A cargo container scanner using a high-energy X-ray generates a fan beam X-ray to acquire a transmitted image. Because the generated X-rays by LINAC may affect the image quality and radiation protection of the system, it is necessary to acquire accurate information about the generated X-ray beam distribution. In this paper, a diode-based multi-channel spatial dose measuring device for measuring the X-ray dose distribution developed for measuring the high energy X-ray beam distribution of the container scanner is described. Materials and Methods: The developed high-energy X-ray spatial dose distribution measuring device can measure the spatial distribution of X-rays using 128 diode-based X-ray sensors. And precise measurement of the beam distribution is possible through automatic positioning in the vertical and horizontal directions. The response characteristics of the measurement system were evaluated by comparing the signal gain difference of each pixel, response linearity according to X-ray incident dose change, evaluation of resolution, and measurement of two-dimensional spatial beam distribution. Results and Discussion: As a result, it was found that the difference between the maximum value and the minimum value of the response signal according to the incident position showed a difference of about 10%, and the response signal was linearly increased. And it has been confirmed that high-resolution and two-dimensional measurements are possible. Conclusion: The developed X-ray spatial dose measuring device was evaluated as suitable for dose measurement of high energy X-ray through confirmation of linearity of response signal, spatial uniformity, high resolution measuring ability and ability to measure spatial dose. We will perform precise measurement of the X-ray beamline in the container scanning system using the X-ray spatial dose distribution measuring device developed through this research.

• Journal of Astronomy and Space Sciences
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• v.30 no.3
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• pp.127-132
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• 2013

Here we review the effort of Fermi Asian Network (FAN) in exploring the supernova remnants (SNRs) with state-of-art high energy observatories, including Fermi Gamma-ray Space Telescope and Chandra X-ray Observatory, in the period of 2011- 2012. Utilizing the data from Fermi LAT, we have discovered the GeV emission at the position of the Galactic SNR Kes 17 which provides evidence for the hadronic acceleration. Our study also sheds light on the propagation of cosmic rays from their acceleration site to the intersteller medium. We have also launched an identification campaign of SNR candidates in the Milky Way, in which a new SNR G308.3-1.4 have been uncovered with our Chandra observation. Apart from the remnant, we have also discovered an associated compact object at its center. The multiwavelength properties of this X-ray source suggest it can possibly be the compact binary that survived a supernova explosion.

• Journal of information and communication convergence engineering
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• v.8 no.5
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• pp.581-585
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• 2010

A grid was sandwiched between two cascaded imaging plates. Using a fan-beam X-ray tube and a single exposure scheme, the two imaging plates, respectively, recorded grid-less and grid type information of the object. Referring to the mathematical model of the Grid-less and grid technique, it was explained that the collected components whereas that of imaging plates with grid was of high together with large scattered components whereas that of imaging plate with grid was of low and suppressed scattered components. Based on this assumption and using a Gaussian convolution kernel representing the effect of scattering, the related data of the imaging plates were simulated by computer. These observed data were then employed in the developed post-processing estimation and restoration (kalman-filter) algorithms and accordingly, the quality of the resultant image was effectively improved.

• Journal of the Korean Society for Nondestructive Testing
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• v.18 no.3
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• pp.181-190
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• 1998

A computerized tomography system was developed using the X-ray source that has diameter of 5 micrometer. The system is used for the nondestructive testing of specimens with diameter below 20 mm. The convolution back projection algorithm was adopted for the reconstruction of cross sectional image, and the shape of the X-ray beam was let parallel beam or fan beam to compare each resultant image. Our CT system was constructed to operate based on the personal computer. The sectional images of the fabricated specimens were reconstructed and analyzed. The reconstructed images well coincided with real images taken with optical microscope and gave us enough reports on the defects in the ceramic specimen. The resolution of the system regarded as about $20{\sim}30$ micrometers.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.425-426
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• 2002

The bone densitometer is to investigate the bone mineral content and density for the osteoporosis assessment by using dual energy X-ray photons. For the clinical verification of the ISOL's OSTEO plus, the clinical study was performed with healthy and non-menopausal 30 female volunteers. The fan-beam DXA machine (Lunar, Expert) was chosen as a reference. After correlation analysis of their bone mineral densities, a strong correlation was obtained. From the results, it is claimed that the new forearm bone densitometer is clinically useful in osteoporosis diagnosis.

• Journal of Astronomy and Space Sciences
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• v.31 no.2
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• pp.101-120
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• 2014

The nature of the exotic stellar corpses which reincarnate by consuming their companion is reviewed. Apart from sucking life from their partners, they are actually eating the doomed companions away by their deadly and powerful particle/radiation beams. Such situation resembles that a female "black widow" spider that eats its mate after mating. These celestial zombies are called - Millisecond pulsars (MSPs). In this review article, I will focus on the effort of Fermi Asian Network (FAN) in exploring these intricating objects over the last five years. Two special classes of MSPs are particularly striking. Since Fermi Gamma-ray Space Telescope has started surveying the gamma-ray sky, the population of "black widows" has been boosted. Another dramatic class is so-called "redbacks" (Australian cousin of "black widows") which has just emerged in the last few years. These MSPs provide us with a long-sought missing link in understanding the transition between accretion-powered and rotation-powered systems. The strategy of hunting MSPs through mulitwavelength observations of the unidentified Fermi objects is also reviewed.

• Korean Journal of Optics and Photonics
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• v.5 no.2
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• pp.204-211
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• 1994

Micro array lens systems are designed for a faximile or copy machine. The array type is hexagonal. Diameter of a lens is 0.16 mm and the distance of the center of the nearest neighbor is 0.192 mm. The magnitude of the lens system is 1:1. Working distane is 10.55 mm and the spot size is less than 0.04 mm radius on axis and 0.20 mm off-axis in case of single layer system. Working distance is 7.90 mm and the spot size is less than 0.07 mm radius on axis and 0.09 mm radius off axis in case of double layer system. Performance of single layer micro array lens system and double layer micro array lens system are compared with the characteristics of the ray fans.y fans.

• Bulletin of the Korean Chemical Society
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• v.33 no.7
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• pp.2309-2314
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• 2012

Ag deposited N-$TiO_2$ composite nanoparticles were prepared via $NH_3$ plasma treatment. X-ray diffraction, UV-vis spectroscopy, photoluminescence, and X-ray photoelectron spectroscopy were used to characterize the prepared $TiO_2$ samples. The plasma treatment did not change the phase composition and particle sizes of $TiO_2$ samples, but extended its absorption edges to the visible light region. The photocatalytic activities were tested in the degradation of an aqueous solution of a reactive dyestuff, methylene blue, under visible light. The photocatalytic activities of Ag deposited N-$TiO_2$ composite nanoparticles were much higher than Ag-$TiO_2$, N-$TiO_2$, and P25. A possible mechanism for the photocatalysis was proposed.