• Title/Summary/Keyword: GPD

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Extreme Value Analysis of Statistically Independent Stochastic Variables

  • Choi, Yongho;Yeon, Seong Mo;Kim, Hyunjoe;Lee, Dongyeon
    • Journal of Ocean Engineering and Technology
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    • v.33 no.3
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    • pp.222-228
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    • 2019
  • An extreme value analysis (EVA) is essential to obtain a design value for highly nonlinear variables such as long-term environmental data for wind and waves, and slamming or sloshing impact pressures. According to the extreme value theory (EVT), the extreme value distribution is derived by multiplying the initial cumulative distribution functions for independent and identically distributed (IID) random variables. However, in the position mooring of DNVGL, the sampled global maxima of the mooring line tension are assumed to be IID stochastic variables without checking their independence. The ITTC Recommended Procedures and Guidelines for Sloshing Model Tests never deal with the independence of the sampling data. Hence, a design value estimated without the IID check would be under- or over-estimated because of considering observations far away from a Weibull or generalized Pareto distribution (GPD) as outliers. In this study, the IID sampling data are first checked in an EVA. With no IID random variables, an automatic resampling scheme is recommended using the block maxima approach for a generalized extreme value (GEV) distribution and peaks-over-threshold (POT) approach for a GPD. A partial autocorrelation function (PACF) is used to check the IID variables. In this study, only one 5 h sample of sloshing test results was used for a feasibility study of the resampling IID variables approach. Based on this study, the resampling IID variables may reduce the number of outliers, and the statistically more appropriate design value could be achieved with independent samples.

Comparison of probability distributions to analyze the number of occurrence of torrential rainfall events (집중호우사상의 발생횟수 분석을 위한 확률분포의 비교)

  • Kim, Sang Ug;Kim, Hyeung Bae
    • Journal of Korea Water Resources Association
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    • v.49 no.6
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    • pp.481-493
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    • 2016
  • The statistical analysis to the torrential rainfall data that is defined as a rainfall amount more than 80 mm/day is performed with Daegu and Busan rainfall data which is collected during 384 months. The number of occurrence of the torrential rainfall events can be simulated usually using Poisson distribution. However, the Poisson distribution can be frequently failed to simulate the statistical characteristics of the observed value when the observed data is zero-inflated. Therefore, in this study, Generalized Poisson distribution (GPD), Zero-Inflated Poisson distribution (ZIP), Zero-Inflated Generalized Poisson distribution (ZIGP), and Bayesian ZIGP model were used to resolve the zero-inflated problem in the torrential rainfall data. Especially, in Bayesian ZIGP model, a informative prior distribution was used to increase the accuracy of that model. Finally, it was suggested that POI and GPD model should be discouraged to fit the frequency of the torrential rainfall data. Also, Bayesian ZIGP model using informative prior provided the most accurate results. Additionally, it was recommended that ZIP model could be alternative choice on the practical aspect since the Bayesian approach of this study was considerably complex.

Enhanced and Targeted Expression of Fungal Phytase in Saccharomyces cerevisiae

  • LIM, YOUNG-YI;EUN-HA PARK;JI-HYE KIM;SEUNG-MOON PARK;HYO-SANG JANG;YOUN-JE PARK;SEWANG YOON;MOON-SIK YANG;DAE-HYUK KIM
    • Journal of Microbiology and Biotechnology
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    • v.11 no.6
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    • pp.915-921
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    • 2001
  • Phytase improves the bioavailability of phytate phosphorus in plant foods to humans and animals, and reduces the phosphorus pollution of animal waste. In order to express a high level of fungal phytase in Saccharomyces cerevisiae, various expression vectors were constructed with different combinations of promoters, translation enhancers, signal peptides, and terminator. Three different promoters fused to the phytase gene (phyA) from Aspergillus niger were tested: a galactokinase (GAL1) promoter, glyceraldehyde-3-phosphate dehydrogenase (GPD) promoter, and yeast hybrid ADH2-GPD promoter consisting of alcohol dehydrogenase II (ADH2) and a GPD promoter. The signal peptides of phytase, glucose oxidase (GO), and rice amylase 1A(RAmy1A) were included. Plus, the translation enhancers of the ${\Omega}$ sequence and UTR70 from the tobacco mosaic virus (TMV) and spinach, respectively, were also tested. Among the recombinant vectors, pGphyA06 containing the GPD promoter, the ${\Omega}$ sequence, RAmy1A, and GAL7 terminator expressed the highest phytase activity in a culture filtrate, which was estimated at 20 IU/ml. An intracellular localization of the expressed phytase activity in a culture filtrate, which was estimated at 20 IU/ml. An intracellular localization of the expressed phytase was also performed by inserting an endoplasmic reticulum (ER) retention signal, KDEL sequence, into the C-terminus of the phytase within the vector pHphyA-6. It appeared that the KDEL sequence directed most of the early expression of phytase into the intracellular compartment yet more than $60\%$ of the total phytase activity was still retained within the cell even after the prolonged (>3 days) incubation of the transformant. However, the intracellular enzyme activity of the transformant without a KDEL sequence was as high as that of the extracellular one, thereby strongly suggesting that the secretion of phytase in S. cerevisiae appeared to be the rate-limiting step for the expression of a large amount of extracellular recombinant phytase, when compared with other yeasts.

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Threshold Estimation of Generalized Pareto Distribution Based on Akaike Information Criterion for Accurate Reliability Analysis (정확한 신뢰성 해석을 위한 아카이케 정보척도 기반 일반화파레토 분포의 임계점 추정)

  • Kang, Seunghoon;Lim, Woochul;Cho, Su-Gil;Park, Sanghyun;Lee, Minuk;Choi, Jong-Su;Hong, Sup;Lee, Tae Hee
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.39 no.2
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    • pp.163-168
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    • 2015
  • In order to perform estimations with high reliability, it is necessary to deal with the tail part of the cumulative distribution function (CDF) in greater detail compared to an overall CDF. The use of a generalized Pareto distribution (GPD) to model the tail part of a CDF is receiving more research attention with the goal of performing estimations with high reliability. Current studies on GPDs focus on ways to determine the appropriate number of sample points and their parameters. However, even if a proper estimation is made, it can be inaccurate as a result of an incorrect threshold value. Therefore, in this paper, a GPD based on the Akaike information criterion (AIC) is proposed to improve the accuracy of the tail model. The proposed method determines an accurate threshold value using the AIC with the overall samples before estimating the GPD over the threshold. To validate the accuracy of the method, its reliability is compared with that obtained using a general GPD model with an empirical CDF.

Heterologous Expression of Human Ferritin H-chain and L-chain Genes in Saccharomyces cerevisiae (재조합 효모를 이용한 사람 H-Chain 교 L-Chain Ferritin의 생산)

  • 서향임;전은순;정윤조;김경숙
    • KSBB Journal
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    • v.17 no.2
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    • pp.162-168
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    • 2002
  • Human ferritin H- and L-chain genes(hfH and hfL) were cloned into the yeast shuttle vector YEp352 with various promoters, and the vectors constructed were used to transform Saccharomyces cerevisiae 2805. Three different promoters fused to hfH and hfL were used: galactokinase 1 (GAL1) promoter, glyceraldehyde-3-phosphate dehydrogenase(GPD) promoter and alcohol dehydrogenase 1(ADH1 ) promoter. SDS-polyacrylamide gel electrophoresis and Western blotting analyses displayed expression of the introduced hfH and hfL. In the production of both ferritin H and L subunits GAL1 promoter was more effective than GPD promoter or ADH1 promoter. Ferritin H and L subunits produced in S. cerevisiae were spontaneously assembled into its holoproteins as proven on native polyacrylamide gels. Both recombinant H and L-chain ferritins were catalytically active in forming iron core. When the cells were cultured in the medium containing 10 mM ferric citrate, the cell-associated concentration of iron was 174.9 $\mu\textrm{g}$ Per gram(dry cell weight) for the recombinant yeast YG-L and 148.8 $\mu\textrm{g}$ Per gram(dry cell weight) for the recombinant yeast YG-L but was 49.4 $\mu\textrm{g}$ Per gram(dry cell weight) in the wild type, indicating that the iron contents of yeast is improved by heterologous expression of human ferritin H-chain or L-chain genes.

The Irradiated Lung Volume in Tangential Fields for the Treatment of a Breast (유방암의 접선 조사시 피폭 폐용적)

  • Oh Young Taek;Kim Juree;Kang Haejin;Sohn Jeong Hye;Kang Seung Hee;Chun Mison
    • Radiation Oncology Journal
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    • v.15 no.2
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    • pp.137-143
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    • 1997
  • Purpose : Radiation pneumonitis is one of the complications caused by radiation therapy that includes a Portion of the lung tissue. The severity of radiation induced pulmonary dysfunction depends on the irradiated lung volume, total dose, dose rate and underlying Pulmonary function. It also depends on whether chemotherapy is done or not. The irradiated lung volume is the most important factor to predict the pulmonary dysfunction in breast cancer Patients following radiation therapy. There are some data that show the irradiated lung volume measured from CT scans as a part of treatment Planning with the tangential beams. But such data have not been reported in Korea. We planned to evaluate the irradiated lung volume quantitatively using CT scans for the breast tangential field and search for useful factors that could Predict the irradiated lung volume Materials and Methods : The lung volume was measured for 25 patients with breast cancer irradiated with tangential field from Jan.1995 to Aug.1996. Parameters that can predict the irradiated lung volume included; (1) the peruendicular distance from the Posterior tangential edge to the posterior part of the anterior chest wall at the center of the field (CLD) ; (2) the maximum perpendicular distance from the posterior tangential field edge to the posterior Part of the anterior chest wall (MLD) ; (3) the greatest perpendicular distance from the Posterior tangential edge to the posterior part of anterior chest wall on CT image at the center of the longitudinal field (GPD) ; (4) the length of the longitudinal field (L). The irradiated lung volume(RV), the entire both lung volume(EV) and the ipsilateral lung volume(IV) were measured using dose volume histogram. The relationship between the irradiated lung volume and predictors was evaluated by regression analysis. Results :The RV is 61-279cc (mean 170cc), the RV/EV is $2.9-13.0\%\;(mean\;5.8\%)$ and the RV/IV is $4.9-29.0\%\;(mean\;12.2\%)$. The CLD, the MLD and the GPD ave 1.9-3.3cm, 1.9-3.3cm and 1.4-3.1cm respectively. The significant relations between the irradiated lung volume such as RV. RV/EV, RV/IV and parameters such as CLD, MLD, GPO, L. $CLD\timesL,\;MLD\timesL\;and\;GPD\timesL$ are not found with little variances in parameters. The RV/IV of the left breast irradiation is significantly larger than that of the right but the RV/EVS do not show the differences. There is no symptomatic radiation pneumonitis at least during 6 months follow up. Conclusion : The significant relationship between the irradiated lung volume and predictors is not found with little variation on parameters. The irradiated lung volume in the tangential held is liss than $10\%$ of entire lung volume when CLO is less than 3cm. The RV/IV of the left tangential field is larger than that of the right but there was no significant differences in RV/EVS. Symptomatic radiation pneumonitis has not occurred during minimum 6 months follow up.

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