• Journal of Radiation Protection and Research
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• v.3 no.1
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• pp.6-22
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• 1978

High energy electron beams took effect for tumor radio-therapy, however, had a lot of problems in clinical application because of various conversion factors and complication of physical reactions. Therefor, we had experimentally studied the important properties of high energy electron beams from the linear accelerator, LMR-13, installed in Yonsei Cancer Center. The results of experimental studies on the problems in the 8, 10, 12 Mev electron beam therapy were reported as following. 1. On the measurements of the outputs and absorbed doses, the ionization type dosimeters that had calibrated by $^{90}Sr$ standard source were suitable as under 3% errors for high energy electrons to measure, but measuring doses in small field sizes and the regions of rapid fall off dose with ionization chambers were difficult. 2. The electron energy were measured precisely with energy spectrometer consisted of magnet analyzer and tele-control detector and the practical electron energy was calculated under 5% errors by maximum range of high energy electron beam in the water. 3. The correcting factors of perturbated dose distributions owing to radiation field, energy and material of the treatment cone were checked and described systematically and variation of dose distributions due to inhomogeneous tissues and sloping skin surfaces were completely compensated. 4. The electron beams, using the scatterers; ie., gold, tin, copper, lead, aluminium foils, were adequately diffused and minimizing the bremsstrahlung X-ray induced by the electron energy, irradiation field size and material of scatterers, respectively. 5. Inproving of the dose distribution from the methods of pendulum, slit, grid and focusing irradiations, the therapeutic capacity with limited electron energy could be extended.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.71.2-71.2
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• 2010

Cooling hot gas sets a floor on the ionization level for diffuse gas in the ISM in general and the galactic halo. Many high galactic latitude sight lines, cooling hot gas is the dominant source of the ionization. Such sites are prime regions for the formation of both C IV and Si IV ions at a temperature of T~105K. To study of the ISM that have the 104.5~6K ionization state by ionization or photoionization by the collision, searching for the radiation energy that is emitted at far ultra violet range is required. In this paper, we report the analysis of NGP( North Galactic Pole, $l:270^{\circ},b:90^{\circ},rad:40^{\circ}$) region by fuv($1350{\sim}1750{\AA}$) data that are surveyed with FIMS. After making the FIMS FUV image of the NGP region, we divided up into 50 small regions for that and got the spectrum emission lines from each one.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.70.2-70.2
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• 2010

Cooling hot gas sets a floor on the ionization level for diffuse gas in the ISM in general and the galactic halo. Many high galactic latitude sight lines, cooling hot gas is the dominant source of the ionization. Such sites are prime regions for the formation of both C IV and Si IV ions at a temperature of T~105K. To study of the ISM that have the 104.5~6K ionization state by ionization or photoionization by the collision, searching for the radiation energy that is emitted at far ultra violet range is required. In this paper, we report the analysis of NGP(North Galactic Pole, $l:0^{\circ},b:90^{\circ}$,rad: $40^{\circ}$) region by fuv($1350\sim1750\AA$) data that are surveyed with FIMS. After making the FIMS FUV image of the NGP region, we divided up into some small regions for that and got the spectrum emission lines from each one.

• Analytical Science and Technology
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• v.23 no.5
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• pp.498-504
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• 2010

It is very difficult to get stable ion peak intensity of ruthenium by thermal ionization mass spectrometry because of its high ionization potential and high volatility of its oxides which causes to lose much of ruthenium ions, so the intensity of the signal decrease quickly. Accordingly, a study was performed in oder to increase the ionization efficiency and to prevent sample losses due to volatilization and to check with isobaric effect by impurities in filament for the measurement of ruthenium isotopes. Both single filament and double filament were tested. The former was proved to be more efficient for the stable and strong intensity of signal and revealed less isobaric effect from the molybdenum (Mo) as a filament impurity. Also, when the temperature of filament increased too high, the isobaric effect from Mo greatly appeared. That is, Mo impurity from filament gave a serious effect for measuring the ruthenium isotopes. It was proved to be of importance that filament current should be slowly increased with time interval. Finally, ruthenium isotopes were accurately measured by correction with measuring $^{94}Mo/^{99}Ru$.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.05a
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• pp.394-397
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• 1999

Impact ionization, which is a kind of a carrier-carrier interaction process occurring in a semiconductor under the influence of a high electric field, is necessary to analyse carrier transport properties. Since the parabolic or nonparabolic E-k relation is different from real band structure in high energy range, exact model of impart ionization have been presented using full band I-k relation and Fermi's golden rule. We have investigated relation of density of states, energy band structure and overlap integral. We make use of empirical pseudopotential method in order to calculate energy band structure of silicon, tetrahedron method in order to calculate density of states. We know density of states very depends on energy band structure and overlap integral depends on the primary electron energy.

• Progress in Medical Physics
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• v.13 no.2
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• pp.69-73
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• 2002

Exposure measurement data with parallel plate ionization chambers were known to depend on the polarity ($k_{pol}$) effect. In this work, the polarity effect were investigated for three parallel plate ionization chambers with different volume. The ionization chamber was fabricated using acrylic plate for the chamber medium and printed circuit board for electrical configuration. The various sizes of the sensitive volumes designed so far were 0.9, 1.9, and 3.1 co. High voltage generator was fabricated using the conventional 9 V batteries to apply the high voltage (300-500 V) to the electrode of the parallel plate ionization chamber. The gap between two electrodes ranged from 3, 6, and 10mm. As the result of our experiment, the polarity effect was within 0.5% in photon beam and 1% to 3.5% in the electron beams. Among electron beams, 16 MeV beam, which had highest energy, showed less polarity effect than electron beams with other energies.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.11a
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• pp.552-554
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• 1999

Phonon scattering and impact ionization models have been presented to analyze hot carrier transport in high energy region, using full band model and Fermi's golden rule. We have investigated temperature dependent properties for impact ionization process of Si using realistic energy band structures at 77K and look. The realistic full band model, obtained from the empirical pseudopotential method with local from factors, is used to calculate scattering rate. The accurate calculation of impact ionization rate requires the use of a wavevector- and frequency-dependent dielectric function ξ ( q,$\omega$). The empirical phonon scattering rate P$\sub$ph/, is given by deriving from linear function for P$\sub$ph/ versus D(E) since the phonon scattering rate is linearly depended on density of states D(E). Impact ionization rate p,, is calculated from the first principle's theory. and fitted by modified Keldysh formula having power of above 2.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.3
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• pp.181-187
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• 1998

The ionization energy and degree of ionization for p-type $Si_{1-x}Ge_x$ with boron doping are calculated taking into account the screening and broadening effects. The drift and Hall mobilities are then calculated using the relaxation time approximation and compared with the previously reported measurement data for relaxed and strained $Si_{1-x}Ge_x$ alloys to estimate the alloy scattering potential. From a fit, the alloy scattering potential is found to be 0.5 eV. The in-plane drift mobility for p-type strained $Si_{1-x}Ge_x$ grown on (001) Si substrate is approximately 1+$10x^2$ times higher than that for bulk Si in the high doping range.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.3
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• pp.100-109
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• 1995

A new Hydrodynamic model for the high energy tail electrons(Tail Electron Hydrodynamic Model : TEHD) is developed using the moment method. The Monte Carlo method is applied to a $n^{+}-n^{-}-n^{+}$ device to calibrate the TEHD equations. the discretization method and numerical procedures are explained. New models for the impact ionization and injection into the gate oxide using the tail electron density are proposed. The simulated results of the impact ionization rate for a $n^{+}-n^{-}-n^{+}$ device and MOSFET devices, and the gate injection experiment are shown to give good agreement with the Monte Carlo simulation and the measurements.

• Mass Spectrometry Letters
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• v.9 no.4
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• pp.91-94
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• 2018

Bilin tetrapyrroles are metabolic products of the breakdown of porphyrins within a species. In the case of mammals, these bilins are formed by the catabolism of heme and can be utilized as either biomarkers in disease or as an indicator of human waste contamination. Although a small subset of bilin tandem mass spectrometry reports exist, limited data is available in online databases for their fragmentation. The use of fragmentation data is important for metabolomics analyses to determine the identity of compounds detected within a sample. Therefore, in this study, the fragmentation of bilins generated by positive ion mode electrospray ionization is examined by collision-induced dissociation (CID) as a function of collision energy on an FT-ICR MS. The use of the FT-ICR MS allows for high mass accuracy measurements, and thus the formulas of resultant product ions can be ascertained. Based on our observations, fragmentation behavior for hemin, biliverdin and its dimethyl ester, phycocyanobilin, bilirubin, bilirubin conjugate, mesobilirubin, urobilin, and stercobilin are discussed in the context of the molecular structure and collision energy. This report provides insight into the identification of structures within this class of molecules for untargeted analyses.