• Journal of the Korean Vacuum Society
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• v.8 no.2
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• pp.102-110
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• 1999

The LIGA X-ray exposure step was modelled into three inequalities, by assuming that the X-ray energy attenuated within a resist is deposited only in the localized range of the resist. From these inequalities, equations for the minimum and maximum exposure times required for a good quality microstructure were obtained. Also, an equation for the thickness of an X-ray mask absorber was obtained from the exposure requirement of threshold dose deposition. The calculation method of the synchrotron radiation power from a synchrotron radiation source was introduced and applied to an X-ray exposure step. A power from a synchrotron radiation source was introduced and applied to an X-ray exposure step/ A power function of photon energy, approximating the attenuation length of the representative LIGA resist, PMMA, and the mean photon energy of the XZ-rays incident upon an X-ray mask absorber were applied to the above mentioned equations. Consequently, the tendencies of the minimum and maximum exposure and with respect to mean photon energy and thick ness of PMMA was obtained. Additionally, the tendencies of the necessary thickness of PMMA and photon energy of the X-ray mask absorber with respect to thickness of PMMA and photon energy of the X-rays incident upon an X-ray mask absorber were examined. The minimum exposure time increases monotonically with increasing mean photon energy for the same total power density and is not a function of the thickness of resist. The minimum exposure time increases with increasing mean photon energy for the same total power density in the case of the general LIGA process, where the thickness of PMMA is thinner than the attenuation length of PMMA. Additionally, the minimum exposure time increases monotonically with increasing thickness of PMMA. The maximally exposable thickness of resist is proportional to the attenuation length of the resist at the mean photon energy with its proportional constant of ln $(Dd_m/D_{dv})$. The necessary thickness of a gold X-ray mask absorber due to absorption edges of gold, increases smoothly with increasing PMMA thickness ratio, and is independent of the total power density itself. The simplicity of the derived equations has made clearly understandable the X-ray exposure phenomenon and the correlation among the exposure times, the attenuation coefficient and the thickness of an X-ray mask absorber, the attenuation coefficient and the thickness of the resist, and the synchrotron radiation power density.

• Journal of Korea Multimedia Society
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• v.12 no.9
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• pp.1233-1241
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• 2009

Over the 50 percents of women who are older than 45 years have osteoporosis. Because people hardly recognize this disease by themselves, the researches that measure bone mineral density have been doing widely to detect osteoporosis in the early stage. The most widely used methods for bone mineral density measurement are based on the X-ray imaging. Among them, DEXA(Dual-energy X-ray Absorptiometry) imaging is one of the important methods in bone mineral density measurement. DEXA images are useful methods to increase diagnosis efficiency by reducing anatomic noise as two images obtained from two different energy levels. However, it has some problems to a calibration parameter determined by the heuristic method for bone extraction. In this paper, we propose the method to extract bone in DEXA image using calibration parameter based on anatomic attenuation coefficient. The experimental results reveal that the proposed method is effective.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.58.2-58.2
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• 2011

Park, Gott, & Choi (2008) found that when a galaxy is located within the virial radius from its closest neighbor and the neighbor is an elliptical, the probability of the galaxy to be an elliptical is very sensitive to the large-scale background density over a few Mpc scales. They suggested that the large-scale dependence can be arise if the temperature of a diffuse hot gas held by elliptical galaxies are higher in higher density environment. In this study, to understand the large-scale environment affects the X-ray properties of individual galaxies, we investigated the dependence of the X-ray luminosities of the elliptical galaxies on the large-scale environment using X-ray and optical data which we selected from the ROSAT All-Sky Survey and the Sloan Digital Sky Survey Data Release 7. To exclude galaxies embedded in an intra-group/cluster medium which could enhance their observed X-ray luminosity, we used isolated elliptical galaxies.

• Imaging Science in Dentistry
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• v.30 no.4
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• pp.235-242
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• 2000

Purpose: To evaluate the effect of the systemic osteoporosis on radiographic density of alveolar bone and cortical thickness of mandible. Materials and Methods: The bone mineral density values of lumbar and femur were measured by dual-energy X-ray absorptiometry and T scores of lumbar, femur were obtained respectively. Radiographic densities of alveolar bones and panorama mandibular index (PMI, represents as cortical thickness) were analysed statistically according to age and T score variables. Results: The radiographic density of alveolar bone of maxillary molar showed significant difference by age and femur T group. That of mandibular molar showed significant difference between femur T group. Panorama mandibular index showed significant difference between age groups. Conclusion: The radiographic density of alvealar bones was more dependent on age and femur T than lumbar T. Cortical thickness of mandible was correlated with increasing age.

• Journal of the Korean Society of Radiology
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• v.5 no.1
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• pp.27-35
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• 2011

The purpose of this study is to examine factors that affect the bone mineral density of pre-menopause women by using the dual energy x-ray absorptionmetry, ultimately contributing to preventing women's osteoporosis that tends to be aggravated since menopause. Out of the subjects, 20.2% were suffering osteopenia. Age was found most important in estimating the level of bone mineral density. Meanwhile, the older women were, the significantly lower their bone mineral density was. It was found that taking exercise has a more positive effect on boss mineral density than not taking. Exercising in a suitable amount was helping women keep their bone mineral density better. Preferring meat to vegetarian diets were significantly affecting women's bone mineral density. Meanwhile, it was found that the shorter menstrual cycle is, the significantly lower bone mineral density is. A multi=regression analysis of bone mineral density and its related factors showed that the older women were, the significantly lower their bone mineral density was. In other words, age was found as the most risk factor of osteoporosis.

• Journal of the Optical Society of Korea
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• v.13 no.1
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• pp.42-47
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• 2009

The propagation of an intense laser pulse through an upward density-gradient plasma in a self-modulated laser wakefield acceleration (SM-LWFA) is investigated by using particle-in-cell (PIC) simulations. In the fully relativistic and kinetic PIC simulations, the relativistic and kinetic effects including Landau damping enhance the electron dephasing. This electron dephasing is the most important factor for limiting the energy of accelerated electrons. However, the electron dephasing, which is enhanced by relativistic and kinetic effects in the homogeneous plasma, can be forestalled through the detuning process arising from the longitudinal density gradient. Simulation results show that the detuning process can effectively maintain the coherence of the laser wake wave in the spatiotemporal wakefield pattern, hence considerable energy enhancement is achievable. The spatiotemporal profiles are analyzed for the detailed study on the relativistic and kinetic effects. In this paper, the optimum slope of the density gradient for increasing electron energy is presented for various laser intensities.

• Journal of Korean Society of Forest Science
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• v.80 no.4
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• pp.351-359
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• 1991

Annual ring characteristics of pinus thunbergii grown in several air-polluted areas were investigated by soft X-ray densitometry. Ring width, maximum density and relative difference between maximum and minimum density(abbreviated to DD) were generally decreased after the beginning of operation of the factories at the vicinity of the pollution sources. Especially at the nearest areas of the industrial complex, those were distinctly decreased, and the changes, either increases or decreases, in percentage of latewood and minimum density could not be explained by the air pollution dosages. Ring width, maximum density and DD were being more apparently decreased after 5 years than those for 5 years after the beginning of operation, and also the rate of decrease was increased from after 5 years after the beginning of operation, and the rate of decrease of ring width was the highest of all. It was inferred that ring width, maximum density and DD of Pinus thunbergii could be used as indicators to detect the growth damage by air pollution.

• Economic and Environmental Geology
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• v.27 no.3
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• pp.289-294
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• 1994

This paper describes an effective utilization method of well logging data and boring cores for understanding the geology of Keoje-do area. Six holes were drilled in 1988-1989, and all rock cores were recovered. Nevertheless, seven kinds of logs were carried out in each borehole. The geologic situations of the drilling sites are accurately evaluated from a comparison between core descriptions and well logging data. Porosities and clay contents of sedimentary rocks can be calculated using the data of density and gamma-ray logs. Fractured zones are easily detected from the change in inside diameter of borehole by caliper log. Sonic, density and gamma-ray logging data clearly indicate alternated and dyke zones; the former can be detceted from an acoustic wave attenuation and a decline of compaction by sonic and density logs, the latter can be detected from the amount of potassium contents of bed rock and dyke by gamma-ray log.

• Journal of Magnetics
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• v.11 no.2
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• pp.87-89
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• 2006

CoFeV thin film alloys were fabricated by electrodeposition, and the dependences of their magnetic properties on the current density were investigated using an X-ray diffractometer and a vibrating sample magnetometer. The deposited Co increased from about 45 to 60 wt.% with increasing current density until $25mA/cm^2$ whereas the deposited Fe decreased from about 55 to 40 wt.% with increasing current density until $25mA/cm^2$. The deposited V, about 2 wt.%, was independent of the current density. The current efficiencies of electrodeposition decreased linearly from about 40 to 29% with increasing current density. The X-ray diffraction measurement showed that all peaks of the CoFeV films were consistent with those of a typical Co hcp and Fe bcc mixed phase. An increase in the current density decreased the grain size and increased the lattice constant. The saturation magnetization increased from about 2.2 to 2.5 T with increasing current density. The coercivity measured in the perpendicular direction decreased from 260 to 120 Oe with increasing current density; a drastic drop of 60 Oe occurred at $5mA/cm^2$. The coercivity measured in the in-plane direction remained almost unchanged, at about 20 Oe, with increasing current density.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.29 no.1
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• pp.33-41
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• 2007

Bone scan using radioactive isotope can be more effective than conventional X-ray radiograph for finding jaw lesion because it takes an image of the physiologic change of bone. This study is designed to show how available bone scan is able to diagnose jaw lesion better than simple X-ray and CT, as well as to determine a basis of diagnosis for jaw lesion using bone scan. The 77 patients, visiting the Oral & Maxillofacial Surgery, Department of Dankook University Hospital from January 2002. to August 2005. who were diagnosed histopathologically with postoperative malignant tumor, osteomyelitis, and bone infiltrative benign disease. Preoperative X-ray, CT, bone scan were taken and were compared with histopathologic finding. Also to compare specificty of each lesion in bone scan, bone density was measured to compare. The results were as follows. 1. Among the 25 cases of oral malignant tumor of bony invasion, a positive diagnosis associated with histopathologic evaluation, 22 cases(88%) in bone scan, 14 cases(56%) in CT image, and 10 cases40%) in simple X-ray. 2. Among the 31 cases of osteomyelitis, a positive diagnosis associated with histopathologic evaluation, 30 cases(97%) in bone scan, 23 cases(74%) in CT image, and 19 cases(61%) in simple X-ray. 3. Among the 11cases of bone infiltrative benign disease, a positive diagnosis associated with histopathologic evaluation, 11 cases(100%) in bone scan, 10 cases(91%) in CT image, and 6 cases(55%) in simple X-ray. 4. Measurement of bone density in each group showed no statistical significant difference between malignant tumor and osteomyelitis as well as benign bone disease. But, a statistical significance was seen between osteomyelitis and benign bone disease. From this results, bone scan are more sensitive than simple X-ray and CT image in jaw lesion diagnosis, but specificity shows no significant difference. Therefore, it should be suggested that evaluation of bone scan must be carrying out in reference to final histopathologic diagnosis.