• Advances in materials Research
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• v.2 no.2
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• pp.93-98
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• 2013

Objective of this study is to calculate gamma buildup factors for pointed and isotropic gamma sources in depleted uranium, uranium dioxide, natural uranium, tin, water and concrete using MCNP4C code. The thickness of the media ranges from 0.5 to 10 mean-free-path (mfp) and gamma energy ranges from 0.5 to 10 MeV. Owing to the outstanding accuracy of MCNP in calculation involving gamma interaction, results fairly match those reported previously. The maximum relative error is 2%.

• The Journal of Korean Society for Radiation Therapy
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• v.9 no.1
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• pp.50-55
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• 1997

The optimal management of uveal melanoma is still a matter of controversy. To determine the effect of Gamma Knife surgery for patients with uveal malanoma. the authors reviewed the results of 5 patients underwent Gamma Knife sugery between Sep. 1993 and Dec. 1996. The mean age was 60.7 years ranging from 42.5 to 76.5 years. Median follow-up was 13.29 months and the patient with follow up period more than 6 months was 4. The mean tumor volume was $3442 mm^3$(mean diameter 15.3 mm) and all patients were irradiated with a mean maximum dose of 74Gy(range $60\~80\;Gy$), using the $50\%$ isodose. After Gamma Knife surgery. one pateint showed complete disapperance in tumor size with follow-up 32 months, one enucleation due to progression, and 2 no interval change. In regard to vision, one patient blind. one enucleation, and 2 patients had no interval change. According to our experiences, Gamma Knife surgery for uveal melanoma be able to achieve local tumor control, spare the eyeball, and have possibility of save vision.

• Bulletin of the Korean Mathematical Society
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• v.54 no.1
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• pp.159-175
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• 2017

We solve the $Bj{\ddot{o}}rling$ problem for constant mean curvature one surfaces in hyperbolic three-space and in de Sitter three-space. That is, we show that for any regular, analytic (and spacelike in the case of de Sitter three-space) curve ${\gamma}$ and an analytic (timelike in the case of de Sitter three-space) unit vector field N along and orthogonal to ${\gamma}$, there exists a unique (spacelike in the case of de Sitter three-space) surface of constant mean curvature 1 which contains ${\gamma}$ and the unit normal of which on ${\gamma}$ is N. Some of the consequences are the planar reflection principles, and a classification of rotationally invariant CMC 1 surfaces.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.2
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• pp.59-68
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• 1998

This study was conducted to derive optimal design floods by generalized gamma distribution model of the annual maximum series at eight watersheds along Geum, Yeongsan and Seomjin river systems. Design floods obtained by different methods for evaluation of parameters and for plotting positions in the generalized gamma distribution model were compared by the relative mean errors and graphical fit along with 95% confidence limits plotted on gamma probability paper. The results were analyzed and summarized as follows. 1. Basic statistics and parameters were calculated by the generalized gamma distribution model using different methods for parameters. 2. Design floods according to the return periods were obtained by different methods for evaluation of parameters and for plotting positions in the generalized gamma distribution model. 3. It was found that design floods derived by sundry averages method for parameters and Cunnane method for plotting position in the generalized gamma distribution are much closer to those of the observed data in comparison with those obtained by the other methods for parameters and for plotting positions from the viewpoint of relative mean errors. 4. Reliability of design floods derived by sundry averages method in the generalized gamma distribution was acknowledged within 95% confidence interval.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.3
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• pp.83-95
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• 1997

This study was conducted to derive optimal design floods by Gamma distribution models of the annual maximum series at eight watersheds along Geum , Yeong San and Seom Jin river Systems, Design floods obtained by different methods for evaluation of parameters and for plotting positions in the Gamma distribution models were compared by the relative mean errors and graphical fit along with 95% confidence interval plotted on Gamma probability paper. The results were analyzed and summarized as follows. 1.Adequacy for the analysis of flood flow data used in this study was confirmed by the tests of Independence, Homogeneity and detection of Outliers. 2.Basic statistics and parameters were calculated by Gamma distribution models using Methods of Moments and Maximum Likelihood. 3.It was found that design floods derived by the method of maximum likelihood and Hazen plotting position formular of two parameter Gamma distribution are much closer to those of the observed data in comparison with those obtained by other methods for parameters and for plotting positions from the viewpoint of relative mean errors. 4.Reliability of derived design floods by both maximum likelihood and method of moments with two parameter Gamma distribution was acknowledged within 95% confidence interval.

• Journal of Environmental Impact Assessment
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• v.23 no.4
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• pp.285-295
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• 2014

In this study, we analyzed probability distribution of EMCs (Event Mean Concentration) of COD, TOC, T-N, T-P and SS from rice paddy fields and compared the mean values of observed EMCs and the median values of estimated EMCs ($EMC_{50}$) through probability distribution. The field monitoring was conducted during a period of four crop-years (from May 1, 2008, to September 30. 2011) in a rice cultivation area located in Emda-myun, Hampyeong gun, Jeollanam-do, Korea. Four probability distributions such as Normal, Log-normal, Gamma, and Weibull distribution were used to fit values of EMCs from rice paddy fields. Our results showed that the applicable probability distributions were Normal, Log-normal, and Gamma distribution for COD, and Normal, Log- Normal, Gamma and Weibull distribution for T-N, and Log-normal, Gamma and Weibull distribution for T-P and TOC, and Log-normal and Gamma distribution for SS. Log-normal and Gamma distributions were acceptable for EMCs of all water quality constituents(COD, TOC, T-N, T-P and SS). Meanwhile, mean value of observed COD was similar to median value estimated by the gamma distribution, and TOC, T-N, T-P, and SS were similar to median value estimated by log-normal distribution, respectively.

• Journal of the Korean Ceramic Society
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• v.33 no.10
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• pp.1079-1088
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• 1996

Discontinuous ${\gamma}$-LiAlO2 fibers for fiber-reinforcing MCFC matrixes have been produced by the sol-gel process using the centrifugal spinning apparatus of the Rotary type. Gel fibers could be obtained through spinning of stable LiAlO2 complex polymetric sols under the optimum spinning conditions (hollow-disc rotating velocity 9000 rpm sol feeding rate of 4ml/min flowing N2 temperature of 4$0^{\circ}C$ and flowing N2 pressure of 4 bar). It was found that defect free and densified ${\gamma}$-LiAlO2 fibers with the relative density of 98% and the mean diameter of 4.7${\mu}{\textrm}{m}$ were prepared when the spinned fibers were heat-treated to 100$0^{\circ}C$ on the specified heating schedule. in particular the mean diameter and length of fibers could be controlled by the pressure of flowing N2 and the chopping-sieving method respectively.

• Journal of Korean Neurosurgical Society
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• v.50 no.3
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• pp.179-184
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• 2011

Objective : The aim of this study is to evaluate the therapeutic effects of gamma knife radiosurgery (GKRS) in patients with multiple brain metastases and to investigate prognostic factors related to treatment outcome. Methods : We retrospectively reviewed clinico-radiological and dosimetric data of 36 patients with 4-14 brain metastases who underwent GKRS for 264 lesions between August 2008 and April 2011. The most common primary tumor site was the lung (n=22), followed by breast (n=7). At GKRS, the median Karnofsky performance scale score was 90 and the mean tumor volume was 1.2 cc (0.002-12.6). The mean prescription dose of 17.8 Gy was delivered to the mean 61.1% isodose line. Among 264 metastases, 175 lesions were assessed for treatment response by at least one imaging follow-up. Results : The overall median survival after GKRS was $9.1{\pm}1.7$ months. Among various factors, primary tumor control was a significant prognostic factor ($11.1{\pm}$1.3 months vs. $3.3{\pm}2.4$ months, p=0.031). The calculated local tumor control rate at 6 and 9 months after GKRS were 87.9% and 84.2%, respectively. Paddick's conformity index (>0.75) was significantly related to local tumor control. The actuarial peritumoral edema reduction rate was 22.4% at 6 months. Conclusion : According to our results, GKRS can provide beneficial effect for the patients with multiple (4 or more) brain metastases, when systemic cancer is controlled. And, careful dosimetry is essential for local tumor control. Therefore, GKRS can be considered as one of the treatment modalities for multiple brain metastase.

• Journal of the Chungcheong Mathematical Society
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• v.27 no.1
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• pp.9-16
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• 2014

Let $\mathbb{A}=\mathbb{F}_q[T]$ be a polynomial ring over $\mathbb{F}_q$. In this paper we determine an asymptotic mean value of quadratic Dirich-let L-functions L(s, ${\chi}_{{\gamma}D}$) at the central point s=$\frac{1}{2}$, where D runs over all monic square-free polynomials of even degree in $\mathbb{A}$ and ${\gamma}$ is a generator of $\mathbb{F}_q^*$.

• Water for future
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• v.18 no.4
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• pp.317-325
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• 1985

In the analysis, monthly streamflow records atthe gauging station in Nakdong, Han and Geum river were used. Also, the fitness of monthly streamflow to Gamma and Long-normal distribution was tested by Kolomogorv-Smirnov test. The results obtained in this study can be summarized as follws (1) The fitness of monthly streamflow to two-parameter Gamma distribution was tested by Kolomorov-Smirnov test, which fits well to this Gamma distribution (2) The Run-length and Run-sum were simulated by the Gamma model. In this result, run-length and Run-sum of monthly streamflow were fit for Gamma model (3) The mean decreases (increases) the expected surplus (deficit) Run-Sum of the monthly streamflow. The higher the truncation level of negative Run-length and Run-sum the larger is the effect of mean.