• 한국철도학회논문집
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• 제2권3호
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• pp.46-53
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• 1999

In this paper, made was a study on a mesh generation method based on the pollution error. This method is designed for the control of the pollution error in any patch of elements of interest. It is a well-known fact that the pollution error estimates are much more than the local one. When the pollution error is significant, nothing can be said about the reliability of any estimator based on local computations in the patch. Reliable a posteriori error estimation is possible by controlling the pollution error in the patch through proper design of the mesh outside the patch. This design is possible by equally distributing the pollution error indicators over the mesh outside the patch. The mesh generated from the conventional feedback pollution-adaptive mesh generation algorithm needs many iterations. Therefore, the solution time is significant. But the remeshing scheme in the proposed method was used here. It was shown that the pollution-adaptive mesh improves the E.I., simply denoted as Effectivity Index, on the patch of interest, and the pollution error reduces less than the local error.

• Journal of Theoretical and Applied Mechanics
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• 제3권1호
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• pp.16-33
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• 2002

A concept of hierarchical modeling, the newest modeling technology. has been introduced early In 1990. This nu technology has a goat potential to advance the capabilities of current computational mechanics. A first step to Implement this concept is to construct hierarchical models, a family of mathematical models which are sequentially connected by a key parameter of the problem under consideration and have different levels in modeling accuracy, and to investigate characteristics In their numerical simulation aspects. Among representative model problems to explore this concept are elastic structures such as beam-, arch-. plate- and shell-like structures because the mechanical behavior through the thickness can be approximated with sequential accuracy by varying the order of thickness polynomials in the displacement or stress fields. But, in the numerical analysis of hierarchical models, two kinds of errors prevail: the modeling error and the numerical approximation errors. To ensure numerical simulation quality, an accurate estimation of these two errors Is definitely essential. Here, a local a posteriori error estimator for elastic structures with thin domain such as plate- and shell-like structures Is derived using element residuals and flux balancing technique. This method guarantees upper bounds for the global error, and also provides accurate local error Indicators for two types of errors, in the energy norm. Comparing to the classical error estimators using flux averaging technique, this shows considerably reliable and accurate effectivity indices. To illustrate the theoretical results and to verify the validity of the proposed error estimator, representative numerical examples are provided.

• Structural Engineering and Mechanics
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• 제8권5호
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• pp.513-529
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• 1999

A concept of hierarchical modeling, the newest modeling technology, has been introduced in early 1990's. This new technology has a great potential to advance the capabilities of current computational mechanics. A first step to implement this concept is to construct hierarchical models, a family of mathematical models sequentially connected by a key parameter of the problem under consideration and have different levels in modeling accuracy, and to investigate characteristics in their numerical simulation aspects. Among representative model problems to explore this concept are elastic structures such as beam-, arch-, plate- and shell-like structures because the mechanical behavior through the thickness can be approximated with sequential accuracy by varying the order of thickness polynomials in the displacement or stress fields. But, in the numerical, analysis of hierarchical models, two kinds of errors prevail, the modeling error and the numerical approximation error. To ensure numerical simulation quality, an accurate estimation of these two errors is definitely essential. Here, a local a posteriori error estimator for elastic structures with thin domain such as plate- and shell-like structures is derived using the element residuals and the flux balancing technique. This method guarantees upper bounds for the global error, and also provides accurate local error indicators for two types of errors, in the energy norm. Compared to the classical error estimators using the flux averaging technique, this shows considerably reliable and accurate effectivity indices. To illustrate the theoretical results and to verify the validity of the proposed error estimator, representative numerical examples are provided.

• 대한기계학회논문집A
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• 제21권5호
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• pp.850-858
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• 1997

A new a posteriori error estimator is introduced and applied to variational inequalities occurring in problems of flow through porous media. In order to construct element-wise a posteriori error estimates the global error is localized by a special mixed formulation in which continuity conditions at interfaces are treated as constraints. This approach leads to error indicators which provide rigorous upper bounds of the element errors. A discussion of a compatibility condition for the well-posedness of the local error analysis problem is given. Two numerical examples are solved to check the compatibility of the local problems and convergence of the effectivity index both in a local and a global sense with respect to local refinements.

• 한국정밀공학회지
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• 제15권5호
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• pp.120-127
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• 1998

Differential inequalities occurring in problems of obstacle contact problems are recast into variational inequalities and analyzed by finite element methods. A new a posteriori error estimator, which is essential in adaptive finite element method, is introduced to capture the errors in finite element approximations of these variational inequalities. In order to construct a posteriori error estimates, saddle point problems are introduced using Lagrange parameters and upper bounds are provided. The global upper bound is localized by a special mixed formulation, which leads to upper bounds of the element errors. A numerical experiment is performed on an obstacle contact problem to check the effectivity index both in a local and a global sense.

• 전산구조공학
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• 제11권1호
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• pp.261-274
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• 1998

본 연구에서는 무요소방법에 적응적 해석기법을 적용하기 위한 부분 및 전체오차의 평가기법을 제안하였다. 본 연구에서 제안한 오차의 평가방법은 무요소방법에서 계산된 응력이 오차가 큰 영역에서 진동한다는 특성을 이용한 것으로 해석결과 얻어진 응력을 낮은 차수의 형상함수로 투사하는 후처리를 함으로써 가상진동모우드를 제거하고 이때 얻어진 투영응력과 원래의 응력을 비교하여 부분오차 및 전체오차를 구할 수 있다. 1차원 및 2차원 예제해석을 통하여 투영응력을 구할 때 가능한 한 작은 영향영역을 사용하는 것이 바람직하다는 것을 보였으며 이는 영향영역의 크기를 과도하게 설정할 경우 투영응력을 과대 평가할 수 있기 때문이다. 본 연구에서 제안한 오차의 평가기법은 다른 무요소 방법에 적용될 수 있다.

• 한국잡초학회지
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• 제1권1호
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• pp.78-83
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• 1981

한국(韓國)의 야생(野生)잔디가 재식(栽植)되에 있는 잔디밭을 대상(對象)으로 문제잡초구명(問題雜草究明) 및 잡초방제방법구명시험(雜草防除方法究明試驗)에서 얻어진 결과(結果)를 요약(要約)하면 다음과 같다. l. 본(本) 조사지역(調査地域)에서 발생(發生)된 잡초종류(雜草種類)는 40여종(餘種)이었고 발생빈도(發生頻度) 및 발생량(發生量) 면(面)에서 크로바, 바랭이, 방동산이, 망초, 꽃다지 등이 문제(問題)의 잡초(雜草)로 구명(究明)되었다. 2. 경산(慶山) 칸트리클럽 주변(周邊)의 조사지점(調査地點)에서는 크로바, 바랭이, 꽃다지, 방동산이, 망초 등이 공존(共存)하는 군락형(群落型)으로 Simpson's Index가 0.306이었고 경북대(慶北大) 캠펴스내(內)의 조사지점(調査地點)에서는 Simpson's Index가 0.776으로 주로 크로바가 우점(優占)하는 군락형(群落型)을 보였다. 전체(全體)의 건물중(乾物重) 증가양상(增加樣相)에는 두 지역간(地域間)에 시간적(時間的) 차이(差異)는 있으나 유사(類似)하였다. 3. 크로바와 광엽잡초(廣葉雜草)가 우점(優占)하는 지역(地域)에 MCPP 3.4kg (a.i.)/ha를 2회(回) 처리(處理)는 경미한 약해(藥害)가 있기는 하나 84.1%의 높은 방제효과(方劑효果)를 나타냈으며 MCPP 2.2~2.8kg (a. i.)/ha 처리(處理)도 약해(藥害)는 전혀 없으며 높은 방제효과(方劑效果)를 나타냈다. 4. 2,4-D 성분량(成分量)으로 2.0kg/ha 처리(處理)는 MCPP 3.4kg (a.i.)/ha 에 준(準)한 방제효과(方劑效果)를 나타내지는 못하였으나 높은 방제율(防除率)을 보였으며 약해(藥害)를 고려(考慮)할 때 2,4-D 1.0kg (a.i.)/ha 정도면 광엽잡초방제(廣棄雜草防除)에 유효(有效)할 것이다.

• 한국수산과학회지
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• 제56권6호
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• pp.861-869
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• 2023

This study aimed to evaluate the effectivity of full-fat black soldier fly Hermetia illucens (BSF) and defatted mealworm Tenebrio molitor (MW) larvae meal as a fish meal (FM) substitute in a low-fish meal (LFM) diet for juvenile olive flounder Paralichthys olivaceus. The LFM diet comprising 45% FM with tankage meal, poultry byproduct meal, soy protein concentrate and wheat gluten was the control diet. Three experimental diets were 10% FM in Con with BSF, MW and a mixture of both at the same ratio (designated as B10, M10 and B5M5, respectively). Four hundred and forty-fourth juvenile P. olivaceus (34.3±0.1 g) were randomly distributed into 12 tanks (425 L) in three replicate groups per treatment and fed the experimental diets for 15 weeks. At the end of the feeding trial, growth performance, survival, biological indices (condition factor, viscerosomatic index, hepatosomatic index), non-specific immune responses (lysozyme, myeloperoxidase) and intestinal histology (villi length and goblet cells) were not significantly affected by treatments. Feed utilization was significantly decreased in M10 compared to the control group. Alanine aminotransferase level was significantly higher in M10 than in the control group. Glucose level was significantly lower in B10 than in the control group. These results suggest that BSF and MW can be used as FM substitutes. However, considering feed conversion ratio and AST level, MW availability is thought to be lower than that of BSF, and feeding fish with a diet containing MW for an extended period is thought to adversely affect fish growth.

• Parasites, Hosts and Diseases
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• 제57권1호
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• pp.1-8
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• 2019

There is no effective treatment modality available against different forms of leishmaniasis. Therefore, the aim of this study was to improve the penetration and efficacy of selenium and glucantime coupled with niosomes and compared them with their simple forms alone on in vitro susceptibility assays. In this study, the niosomal formulations of selenium and in combination with glucantime were prepared. The size and morphology of the niosomal formulations were characterized and the effectivity of the new formulation was also evaluated using in vitro MTT assay, intra-macrophage model, and gene expression profile. From the results obtained, no cytotoxicity effect was observed for niosomal and simple forms of drugs, as alone or in combination. Niosomal formulations of the drugs significantly showed more inhibitory effects ($P{\leq}0.001$) than the simple drugs when the selectivity index was considered. The gene expression levels of Interleukin (IL-10) significantly decreased, while the level of IL-12 and metacaspase significantly increased ($P{\leq}0.001$). The results of the present study showed that selenium plus glucantime niosome possess a potent anti-leishmanial effect and enhanced their lethal activity as evidenced by the in vitro experiments.