• 대한수학회논문집
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• 제24권2호
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• pp.161-169
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• 2009

In this paper, we introduce the generalized ideal-based zero-divisor graph structure of near-ring N, denoted by $\widehat{{\Gamma}_I(N)}$. It is shown that if I is a completely reflexive ideal of N, then every two vertices in $\widehat{{\Gamma}_I(N)}$ are connected by a path of length at most 3, and if $\widehat{{\Gamma}_I(N)}$ contains a cycle, then the core K of $\widehat{{\Gamma}_I(N)}$ is a union of triangles and rectangles. We have shown that if $\widehat{{\Gamma}_I(N)}$ is a bipartite graph for a completely semiprime ideal I of N, then N has two prime ideals whose intersection is I.

• Kyungpook Mathematical Journal
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• 제55권2호
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• pp.449-472
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• 2015

Let X be a nonempty set and $\mathcal{F}$(X) be the set of nonempty finite subsets of X. The paper deals with the extended metrics ${\tau}:\mathcal{F}(X){\rightarrow}\mathbb{R}$ recently introduced by Peter Balk. Balk's metrics and their restriction to the family of sets A with ${\mid}A{\mid}{\leqslant}n$ make possible to consider "distance functions" with n variables and related them quantities. In particular, we study such type generalized diameters $diam_{{\tau}^n}$ and find conditions under which $B{\mapsto}diam_{{\tau}^n}B$ is a Balk's metric. We prove the necessary and sufficient conditions under which the restriction ${\tau}$ to the set of $A{\in}\mathcal{F}(X)$ with ${\mid}A{\mid}{\leqslant}3$ is a symmetric G-metric. An infinitesimal analog for extended by Balk metrics is constructed.

• 수산해양기술연구
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• 제58권3호
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• pp.193-198
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• 2022

In this study, for the purpose of reducing the catch of small giant octopus in a net pot, an escape experiment of octopus was performed on five types of escape rings of different sizes. As a result of the experiment, the smallest giant octopus with a weight of 406 g was found to escape from an escape ring with a diameter of 30 mm or larger, and 592 g octopus, a weight similar to the octopus of the current minimum landing weight (600 g), escaped from an escape ring with a diameter of larger than 40 mm. An individual weight with 406 g becomes 39 mm when converted from a diameter of 25 mm circular escape vent; that is, the circumference to the inner diameter of the mesh. It can be inferred that the converted mesh size of 39 mm cannot escape. Logistic regression analysis was performed using a generalized linear model (GLM) to investigate the correlation between the ratio of escape ring size/Mantle diameter (R/MD) and the escape rate. As a result, it was found that there was a significant correlation between the R/MD ratio and the escape rate and that the higher the R/MD ratio, the greater the escape rate. As a result of logistic regression analysis, the R/MD value was denoted 0.520 with the 50% escape rate. In addition, it can be estimated to be about 50 mm when converted to the mesh size. Therefore, in this study, the diameter of the escape ring and the size of the escape possible of the octopus were experimentally considered. It was found that there was a significant correlation.

• 대한수학회지
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• 제56권2호
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• pp.421-437
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• 2019

We establish some Hessian comparison theorems and volume comparison theorems for Riemann-Finsler manifolds under various line radial integral curvature bounds. As their applications, we obtain some results on first eigenvalue, Gromov pre-compactness and generalized Myers theorem for Riemann-Finsler manifolds under suitable line radial integral curvature bounds. Our results are new even in the Riemannian case.

• Journal of Chest Surgery
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• 제14권3호
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• pp.274-279
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• 1981

We performed three replacement operations of great venous obstruction with Dacron prosthesis from July, 1980 to Nov. 1980. Summary of 3 cases as belows: 1) Inferior vena cava obstruction . 43 years old male was admitted because of abdominal distension and marked superficial collateral circulation on chest and abdomen. Inferior vena cavogram showed complete obstruction of I. V .C. just below hepatic vein. Bypass operation was done between Rt atrium '||'&'||' I. V.C. (just above renal vein) with Woven Dacron prosthesis (22mm in Diameter) under ex tracorporeal ci rculation. 2) Superior vena cava obstruction . 21 years old male was admitted because of facial edema and irritative cough. Well circumscribed lobulated mass was located at ant. superior mediastinum and extended to Rt. thorax in chest P-A view. Woven Dacron prosthesis (10mm in Diameter) was replaced at involved S.V.C. segment after Rt. upper '||'&'||' middle lobectomy with tumor resection. 3) Common iliac vein obstruction (Lt) . 64 years old female was admitted because of generalized edema and tenderness of Lt. lower extremity. Venography of Lt leg showed complete obstruction of common iliac vein. Woven Dacron prosthesis (10mm in Diameter) was replaced at obstruction site.eplaced at obstruction site.

• Advances in aircraft and spacecraft science
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• 제7권3호
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• pp.203-214
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• 2020

In many applications like the aircraft or the rockets/missiles, the flow from a nozzle needs to be expanded suddenly in an enlarged duct of larger diameter. The enlarged duct is provided after the nozzle to maximize the thrust created by the flow from the nozzle. When the fluid is suddenly expanded in an enlarged duct, the base pressure is generally lower than the atmospheric pressure, which results in base drag. The objective of this research work is to optimize the length to diameter (L/D) ratio of the enlarged duct using the CFD analysis in the flow field from the supersonic nozzle. The flow from the nozzle drained in an enlarged duct, the thrust, and the base pressure are studied. The Mach numbers for the study were 1.5, 2.0 and 2.5. The nozzle pressure ratios (NPR) of the study were 2, 5 and 8. The L/D ratios of the study were 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. Based on the results, it is concluded that the L/D ratio should be increased to an optimum value to reattach the flow to an enlarged duct and to increase the thrust. The supersonic suddenly expanded flow field is wave dominant, and the results cannot be generalized. The optimized L/D ratios for various combinations of flow and geometrical parameters are given in the conclusion section.

• 한국전산구조공학회논문집
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• 제34권5호
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• pp.339-345
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• 2021

본 논문에서는 우리나라의 중저준위 방폐물 처분을 위한 사일로 형식 지하동굴의 유한요소해석을 수행하였다. 사일로의 벽체부분은 지름 25m의 원형구조이고, 높이는 35m이다. 사일로의 천장부분은 지름 30m의 돔 형식이고, 높이 17.4m의 규모이다. 사일로는 해수면으로부터 -80m에서 -130m에 위치하고 있다. 중저준위 방폐물 처분 1단계 시설로 6개의 사일로가 건설되어 운영되고 있으나, 본 연구에서는 1개의 사일로에 대해서 고려하였다. SMAP-3D 프로그램을 사용하여 2차원 축대칭 유한요소모델과 3차원 유한요소모델을 생성하였다. Generalized Hoek and Brown Model이 수치해석에 적용되었다. 다양한 측압계수(수평방향 현장응력과 수직방향 현장응력의 비)의 변화에 따른 사일로 형식 지하동굴의 유한요소해석을 수행하였으며, 수치해석결과 및 분석결과가 제시되었다.

• 한국환경보건학회지
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• 제49권3호
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• pp.149-158
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• 2023

Background: Injury is one of the major health problems in South Korea. Few studies have evaluated both intentional and unintentional injury when investigating the association between exposure to air pollutants and injury. Objectives: We aimed to explore the association between short-term exposure to ambient air pollution and years of life lost (YLLs) due to injury. Methods: Data on daily YLLs for 2002~2019 were obtained from the the Death Statistics Database of the Korean National Statistical Office. This study estimated short-term exposure to particulate matter with an aerodynamic diameter of <10 ㎛ (PM₁₀), particulate matter with an aerodynamic diameter of <2.5 ㎛ (PM_2.5), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), carbon monoxide (CO), and ozone (O₃). This time series study was conducted using a generalized additive model (GAM) assuming a Gaussian distribution. We also evaluated a delayed effect of ambient air pollution by constructing a lag structure up to seven days. The best-fitting lag was selected based on smallest generalized cross validation (GCV) value. To explore effect modification by intentionality of injury (i.e., intentional injury [self-harm, assault] and unintentional injury), we conducted stratified subgroup analyses. Additionally, we stratified unintentional injury by mechanism (traffic accident, fall, etc.). Results: During the study period, the average daily YLLs due to injury was 307.5 years. In the intentional injury, YLLs due to self-harm and assault showed positive association with air pollutants. In the unintentional injury, YLLs due to fall, electric current, fire and poisoning showed positive association with air pollutants, whereas YLLs due to traffic accident, mechanical force and drowning/submersion showed negative associations with air pollutants. Conclusions: Injury is recognized as preventable, and effective strategies to create a safe society are important. Therefore, we need to establish strategies to prevent injury and consider air pollutants in this regard.

• Journal of Forest and Environmental Science
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• 제36권1호
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• pp.7-16
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• 2020

Tree size distribution modelling is an integral part of forest management. Most distribution yield systems rely on some flexible probability models. In this study, a simple finite mixture of two components two-parameter Weibull distribution was compared with complex four-parameter distributions in terms of their fitness to predict tree size distribution of teak (Tectona grandis Linn f) plantations. Also, a system of equation was developed using Seemingly Unrelated Regression wherein the size distributions of the stand were predicted. Generalized beta, Johnson's SB, Logit-Logistic and generalized Weibull distributions were the four-parameter distributions considered. The Kolmogorov-Smirnov test and negative log-likelihood value were used to assess the distributions. The results show that the simple finite mixture outperformed the four-parameter distributions especially in stands that are bimodal and heavily skewed. Twelve models were developed in the system of equation-one for predicting mean diameter, seven for predicting percentiles and four for predicting the parameters of the finite mixture distribution. Predictions from the system of equation are reasonable and compare well with observed distributions of the stand. This simplified mixture would allow for wider application in distribution modelling and can also be integrated as component model in stand density management diagram.

• 공업화학
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• 제7권4호
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• pp.809-812
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• 1996

일반화된 van der Waals류의 3차 상태방정식에 사용되는 인력 및 반발력 상수항을 온도의존 함수로 나타내는 core-softening 이론을 도입하여 van der Waals 유체의 비이상적 열팽창, 즉 밀도 비이상성을 설명하였다. 온도의존 함수로는 온도의 증가에 따라 hard-core의 직경피 줄어드는 $db_r/dT_r<0$을 만족하는 형태와, 분자간의 반발력이 강해지는 $da_r/dT_r>0$을 만족하는 식을 사용하였다. 온도에 따른 밀도 최대점은 전자의 경우 전 범위의 압력하에서 나타났으며 후자의 경우 유체에 장력(tension)이 가해질때만 존재하였다.