• Title/Summary/Keyword: Gamma analysis

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Similarity analysis of pixelated CdTe semiconductor gamma camera image using a quadrant bar phantom for nuclear medicine: Monte Carlo simulation study

  • Park, Chan Rok;Kang, Seong-Hyeon;Lee, Youngjin
    • Nuclear Engineering and Technology
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    • v.53 no.6
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    • pp.1947-1954
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    • 2021
  • In the nuclear medicine imaging, quality control (QC) process using quadrant bar phantom is fundamental aspect of evaluating the spatial resolution. In addition, QC process of gamma camera is performed by daily or weekly. Recently, Monte Carlo simulation using the Geant4 application for tomographic emission (GATE) is widely applied in the pre-clinical nuclear medicine field for modeling gamma cameras with pixelated cadmium telluride (CdTe) semiconductor detector. In this study, we modeled a pixelated CdTe semiconductor detector and quadrant bar phantom (0.5, 1.0, 1.5, and 2.0 mm bar thicknesses) using the GATE tool. Similarity analysis based on correlation coefficients and peak signal-to-noise ratios was performed to compare image qualities for various source to collimator distances (0, 2, 4, 6, and 8 cm) and collimator lengths (0.2, 0.4, 0.6, 0.8, and 1.0 cm). To this end, we selected reference images based on collimator length and source to collimator distance settings. The results demonstrate that as the collimator length increases and the source to collimator distance decreases, the similarity to reference images improves. Therefore, our simulation results represent valuable information for the modeling of CdTe-based semiconductor gamma imaging systems and QC phantoms in the field of nuclear medicine.

Low Flow Frequency Analysis of Steamflows Simulated from the Stochastically Generated Daily Rainfal Series (일 강우량의 모의 발생을 통한 갈수유량 계열의 산정 및 빈도분석)

  • Kim, Byeong-Sik;Gang, Gyeong-Seok;Seo, Byeong-Ha
    • Journal of Korea Water Resources Association
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    • v.32 no.3
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    • pp.265-279
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    • 1999
  • In this study, one of the techniques on the extension of low flow series has been developed, in which the daily streamflows were simulated by the Tank model with the input of extended daily rainfall series which were stochastically generated by the Markov chain model. The annual lowest flow serried for each of the given durations were formulated form the simulated daily streamflow sequences. The frequency of the estimated annual lowest flow series was analyzed. The distribution types to be used for the frequency analysis were two-parameter and three-parameter log-normal distribution, two-parameter and three-parameter Gamma distribution, three-parameter log-Gamma distribution, Gumbel distribution, and Weibull distribution, of which parameters were estimated by the moment method and the maximum likelihood method. The goodness-of-fit test for probability distribution is evaluated by the Kolmogorov-Sminrov test. The fitted distribution function for each duration series is applied to frequency analysis for developing duration-low flow-frequency curves at Yongdam Dam station. It was shown that the purposed technique in this study is available to generate the daily streamflow series with fair accuracy and useful to determine the probabilistic low flow in the watersheds having the poor historic records of low flow series.

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The Use of Generalized Gamma-Polynomial Approximation for Hazard Functions

  • Ha, Hyung-Tae
    • The Korean Journal of Applied Statistics
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    • v.22 no.6
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    • pp.1345-1353
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    • 2009
  • We introduce a simple methodology, so-called generalized gamma-polynomial approximation, based on moment-matching technique to approximate survival and hazard functions in the context of parametric survival analysis. We use the generalized gamma-polynomial approximation to approximate the density and distribution functions of convolutions and finite mixtures of random variables, from which the approximated survival and hazard functions are obtained. This technique provides very accurate approximation to the target functions, in addition to their being computationally efficient and easy to implement. In addition, the generalized gamma-polynomial approximations are very stable in middle range of the target distributions, whereas saddlepoint approximations are often unstable in a neighborhood of the mean.

Comparative Analysis on the Design Rainfall derived by Gamma Family Distributions (Gamma Family군의 분포형에 의한 강우의 빈도분석)

  • Ryoo, Kyong-Sik;Lee, Soon-Hyuk;Maeng, Sung-Jin;Song, Ki-Hurn;Kim, Gi-Chang
    • Proceedings of the Korean Society of Agricultural Engineers Conference
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    • 2003.10a
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    • pp.439-442
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    • 2003
  • This study was conducted to choose optimal distribution and to estimate properly parameters for the derivation of design rainfall in Gamma Family. Design rainfall derived by Gamma Family Distributions were compared by the Relative Mean Errors(RME) and Relative Absolute Errors(RAE) for the consecutive durations of 1, 3, 6, 12, 24, 36, 48 and 72hr and 65 regions all over the regions except Cheju and Wulreung islands in Korea. Consequently, Design rainfall derived by Indirect Method of Moments in the Log-Pearson Type 3 distribution are seemed to be more reasonable than those of other distributions in Gamma Family.

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Preparation of Modified Hollow Polypropylene Membrane and Their Adsorption Properties of ${\gamma}$-Globulins

  • Hwang, Taek-Sung;Park, Jin-Won
    • Macromolecular Research
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    • v.11 no.5
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    • pp.347-351
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    • 2003
  • The hydrophobic ligand-containing hollow polypropylene (PP) membranes were synthesized by the mutual radiation induced graft copolymerization with glycidylmethacrylate (GMA) onto hollow PP membrane followed by the subsequent functionalization with L-phenylalanine. FT-IR, elemental analysis and UV spectroscopy were utilized to characterize copolymer composition, and degree of grafting, functionalization conversion and ${\gamma}$-globulins adsorption. The degree of grafting on the PP surface increased with the reaction time and total dose of E-beam. In the subsquent functionalization, the amount of L-phenylalanine increased with the increase in the degree of grafting and the degree of conversion was about 30%. The ${\gamma}$-globulins adsorption experiments showed that adsorption capacity had a maximum value at pH 8. The ${\gamma}$-globulins adsorption capacity in the basic pH region was higher than in the acidic pH region.

Evaluation of solid surface properties by analysis of liquid penetration rate into powder bed - Examination of surface free energy -

  • Choi, Woo-Sik;Ha, Jong-Hak
    • Proceedings of the PSK Conference
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    • 2003.10b
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    • pp.236.1-236.1
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    • 2003
  • Evaluation of solid surface properties is very important for formulation of solid dosage form, specially insoluble drugs. The contact angle of insoluble drugs was measured by the penetration rate into powder bed using Washburn equation and wicking method. From the measured contact angle data, the surface free energy value of pharmaceutical powders ${\gamma}$s was divided and analysized into the polar component, ${\gamma}$s$\^$p/ and the dispersion component, ${\gamma}$s$\^$d/. Furthermore, the data was interpreted for acid part, ${\gamma}$s$\^$+/ and base part, ${\gamma}$s$\^$$\square$/ of surface free energy. (omitted)

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An Study on the Structure of Maghemite(${\gamma}$-Fe$_2$O$_3$) I -Rietveld Analysis of Powder XRD Patterns- (마게마이트(${\gamma}$-Fe$_2$O$_3$)대한 연구 I -분말 X-선 회절무늬의 Rietveld 분석-)

  • 신형섭
    • Journal of the Korean Ceramic Society
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    • v.35 no.10
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    • pp.1113-1119
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    • 1998
  • Crystal structure of needle-shaped maghemite(${\gamma}$-{{{{ { {Fe }_{2 }O }_{3 } }}) has been studied by the Rieveld analysis of powder X-ray diffraction patterns. The tetragonal space group P41,.3212 and cubic space group P41,.32 have been have been used for the refinement of X-ray diffraction patterns. The crystal system of maghemite is closed to tetragonal more than cubic. The tetragonal lattice parameters are a=8.3460$\AA$ and c=25.034$\AA$ The standard X-ray diffraction pattern of the tetragonal maghemite analyzed with space group P41,.3212 is proposed.

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Absence of Tocotrienol Form of Vitamin E in Purple Perilla (Perilla frutescens var. acuta Kudo) Seeds Confirmed by Comparative Analysis Using HPLC and GC (GC 및 HPLC 비교분석에 기초한 차조기 종실내 tocotrienol 부재의 평가)

  • Lee, Young-Sang;Kim, Min-Kyoung
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.53 no.spc
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    • pp.115-120
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    • 2008
  • Lipid soluble vitamin E consists of tocopherols and tocotrienols depending upon double bonds in phytyl side chains attached to chromanol ring. Recent reports on antioxidative, anticancer, and cholesterol-lowering effects of tocotrienols have increased researches and commercialization of tocotrienols. Purple perilla (Perilla frutescens var. acuta Kudo) has been reported as a plant containing tocotrienols along with tocopherol forms of vitamin E based upon normal phase HPLC analysis. To confirm the existence or absence of tocotrienol form of vitamin E in purple perilla, comparative analysis using HPLC, GC/FID, and GC/MSD has been conducted for 14 purple perilla genetic accessions collected from Korea and Japan. Normal phase HPLC analysis showed ${\alpha}-$, ${\beta}-$, ${\gamma}-$, and ${\delta}-tocopherols$ along with peaks with retention times quite similar to ${\beta}-$ and ${\gamma}-tocotrienols$. Same purple perilla samples, analysed by GC exhibited ${\alpha}-$, ${\beta}-$, ${\gamma}-$, and ${\delta}-tocopherols$ quantitatively equivalent to HPLC results. However, no peaks for ${\beta}-$ and ${\gamma}-tocotrienols$ could be observed and unknown two peaks of similar retention times with ${\beta}-$ and ${\gamma}-tocotrienols$ were identified not corresponding tocotrienols by GC/MSD. These results suggest the absence of tocotrienol form of vitamin E in purple perilla as well as the necessity of using GC-based qualitative and quantitative vitamin E analysis to avoid misinterpretation of peaks with similar retention times as tocotrienol isomers when analysed by an HPLC.

Molecular Cloning and mRNA Expression of the Bovine Peroxisome Proliperator Receptor Gamma(PPARγ) (한우 PPARγ 유전자의 동정과 mRNA의 발현)

  • Jeoung, Y.H.;Lee, S.M.;Park, H.Y.;Yoon, D.H.;Choi, J.G.;Moon, S.J.;Kang, M.J.
    • Journal of Animal Science and Technology
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    • v.46 no.1
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    • pp.23-30
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    • 2004
  • The peroxisome proliferator-activated receptor $\gamma$(PPAR$\gamma$), a member of the steroid/thyroid nuclear hormone receptor suferfamily of ligand-activated transcription factor, is an important regulator of adipocyte gene expression and differentiation. In this studies, we report the identification, characterization, and expression of a Hanwoo PPAR$\gamma$ gene. The PPAR$\gamma$ cDNA sequence of the Hanwoo show strong conservation with the corresponding sequences reported in other species except of three amino acid sequences. The distribution of PPAR$\gamma$ mRNA in various tissues of Korean cattle aged 12 months were investigated using Northern Blot analysis. The highest expression was detected in adipose tissue, more lower expression was detected in colon, small intestine, kidney, lung, while expression was not detected in brain, heart. PPAR$\gamma$ expression was higher in adipose tissue of Korean cattle when aged 30 months than aged 12 months. These results indicated PPAR$\gamma$, regulator adipocyte gene expression and differentiation, related on adipose differentiation in Korean native cattle(HANWOO).

A STUDY ON THE MICROSTRUCTURES OF THE AMALGAM ALLOYS AND AMALGAMS (치과용 아말감합금 및 아말감의 마세구조에 관한 연구)

  • Yeon, Sang-Heum;Lee, Chung-Sik;Lee, Myung-Jong;Um, Chung-Moon
    • Restorative Dentistry and Endodontics
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    • v.21 no.1
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    • pp.87-105
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    • 1996
  • The purpose of this study is to investigate the characteristics of the compositions and phases of amalgam alloys and amalgams by using EMPA and X-ray diffractometer. Each specimen was made from Caulk Fine Cut Clow copper lathe cut amalgam), Caulk Spherical (low copper spherical amalgam), Tytin (high copper unicorn position amalgam), Dispersally (high copper admixed amalgam) and Valiant (Palladium enriched amalgam). For preparing amalgam alloys, Tytin and Valiant were used as powder forms and the others were used as tablet forms after being polished with polishing machine. For preparing amalgams, each amalgam alloy and Hg were measured, and triturated by mechanical amalgamater according to user's instructions. After triturating, the triturated mass was inserted to cylindrical metal mold and simultaneously adapted by cylindrical condenser with same diameter and condensed by Instron universal testing machine with 80kg pressure & 1mm/min speed. Each specimen was removed from the metal mold and stored at room temperature for a week. The specimen was polished with the same polishing machine for amalgam alloy. For observation of microstructure and analysis of composition of amalgam alloys and amalgams, EMPA was used to get secondary electron images, backscattered images and characteristic X-ray images of Ag, Sn, Cu, Zn, Hg. To analyze compositions of amalgam alloys and amalgams, X-ray diffractometer was used. Amalgam alloys were scanned at the range of 2${\theta}$ of 30-$85^{\circ}$ and the speed of $4^{\circ}$/min with Cuka line and amalgams were scanned at the range of 2${\theta}$ of 28-$44^{\circ}$ and the speed of $4^{\circ}$/min with Cuka line. By comparing obtained d(distance between surfaces) and d of expected phases and atoms in amalgam alloys and amalgams in ASTM card, phases and atoms were identified. The results were as follows, 1. In Caulk Fine Cut amalgam alloy typical ${\gamma}$ phase was shown, and in amalgam, ${\gamma}$, ${\gamma}_1$ and ${\gamma}_2$ phases were observed. 2. In Caulk Spherical amalgam alloy ${\gamma}$, Ag, Cu and $\varepsilon$ phases were shown, and in amalgam ${\gamma}$, ${\gamma}_1$, ${\gamma}_2$ and $\eta$ phases were observed. 3. In Tytin amalgam alloy ${\gamma}$, Cu and $\varepsilon$ phases were shown, and in amalgam ${\gamma}$, ${\gamma}_1$, $\eta$ and $\varepsilon$ phases were observed. 4. In Dispersalloy ${\gamma}$, Ag, Cu and $\varepsilon$ phases were shown, and in amalgam ${\gamma}$, ${\gamma}_1$, $\eta$ and $\varepsilon$ phases were observed. 5. In Valiant alloy ${\gamma}$, Cu and e phases were shown, and in amalgam ${\gamma}$, ${\gamma}_1$, $\eta$ and $\varepsilon$ phases were observed.

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