• 한국응용과학기술학회지
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• 제29권1호
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• pp.33-39
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• 2012

A numerical simulation of plume from a stack into atmospheric cross flow is investigated using a two-dimension model. The simulation is based on the ${\kappa}{\sim}{\varepsilon}$ turbulence model and a finite volume method. In this paper, it mostly researches how the wind velocity affects the flue gas diffusion from an 80 m high stack. Wind velocity is one of the most important factors for flue gas diffusion. The plume shape size, the injection height, the NO pollutant distribution and the concentration at the near ground are presented with two kinds of wind velocities, 1 m/s and 5 m/s. It is found that large wind velocity is better for flue gas diffusion, it generates less downwash. Although the rise height is lower, the pollutant dilutes faster and more sufficient.

• 한국수학사학회지
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• 제17권4호
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• pp.37-44
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• 2004

힐베르트 시지지 정리와 그에 따른 분해에서 호몰로지 대수의 흔적을 찾을 수 있다. 1950년대에 이르러 대수 위상의 발달과 함께 그의 이론적인 도구로서 호몰로지 대수의 실질적인 시작을 볼 수 있다. 1956년 쎄레는 정칙 국소환의 대역적 차원이 유한하다는 것을 증명하였는데, 이 정리는 호모로지 대수적인 문제 풀이에서 근본적인 도구를 제공하고 있다. 호모로지 대수에서 토르를 구하고 그의 깊이를 계산하는 것은 어려운 문제인데, 이 논문에서는 1961년 오슬랜더가 제시한 토르 가군의 깊이에 관한 문제와 그에 따른 토르 게임(Tor game)에 대하여 논하고자 한다.

• 대한수학회지
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• 제59권4호
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• pp.821-841
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• 2022

In this paper, we introduce and study regular rings relative to the hereditary torsion theory w (a special case of a well-centered torsion theory over a commutative ring), called w-regular rings. We focus mainly on the w-regularity for w-coherent rings and w-Noetherian rings. In particular, it is shown that the w-coherent w-regular domains are exactly the Prüfer v-multiplication domains and that an integral domain is w-Noetherian and w-regular if and only if it is a Krull domain. We also prove the w-analogue of the global version of the Serre-Auslander-Buchsbaum Theorem. Among other things, we show that every w-Noetherian w-regular ring is the direct sum of a finite number of Krull domains. Finally, we obtain that the global weak w-projective dimension of a w-Noetherian ring is 0, 1, or ∞.

• Computers and Concrete
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• 제19권6호
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• pp.641-649
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• 2017

The discovery of the Interfacial Transition Zone (ITZ) by Farran in 1956 initiated a new era in the study of the behaviour of concrete. Acknowledged as the weak link, this ITZ was studied extensively, numerically as well as experimentally. While the complementary experimental tests illustrated the visual behaviour of this specimen under increasing monotonic compression loading, a perfect bond within the ITZ has also been studied by using finite element analysis for comparison purposes. Finite element analysis was used to evaluate the degree of correctness and precision of the proposed ITZ model. This paper discusses the use of the cutoff bar in finite element modeling, representing the ITZ of a single aggregate (inclusion) in a mortar matrix. Experiments were conducted to investigate the influence of the ITZ model on the single inclusion specimen's strength. The model was tested for some inclusions that varied in dimension and shape. The effect of inclusion shape on the stress concentrations of the specimens was examined. The aim of this research work is to propose a simple yet accurate ITZ model to be used in the commercially available finite element software packages.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1288-1293
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• 2007

The present study covers the design and analysis of a thermionic scanning electron microscope (SEM) column. The SEM column contains an electron optical system in which electrons are emitted and moved to form a focused beam, and this generates secondary electrons from the specimen surfaces, eventually making an image. The electron optical system mainly consists of a thermionic electron gun as the beam source, the lens system, the electron control unit, and the vacuum unit. In the design process, the dimension and capacity of the SEM components need to be optimally determined with the aid of finite element analyses. Considering the geometry of the filament, a three-dimensional (3D) finite element analysis is utilized. Through the analysis, the beam emission characteristics and relevant trajectories are predicted from which a systematic design of the electron optical system is enabled. The validity of the proposed 3D analysis is also discussed by comparing the directional beam spot radius. As a result, a prototype of a thermionic SEM is successfully developed with a relatively short time and low investment costs, which proves the adoptability of the proposed 3D analysis.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.654-659
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• 2003

PVAP (Pressure Vessel Analysis Program V1.0) was developed by adopting the finite element analysis program ANSYS V6.0, and Microsoft Visual Basic V6.0 was also utilized for the interfacing and handling of input and output data during the analysis. PVAP offers the end user the ability to design and analyze vessels in strict accordance with ASME Section VIII, Division 2. More importantly, the user is not required to make any design decisions during the input of the vessel. PVAP consists of three analysis modules for the finite element analysis of the primary components of pressure vessel such as head, shell, nozzle, and skirt. In each module, finite element analysis can be performed automatically only if the end user gives the dimension of the vessel. Furthermore, the calculated results are compared and evaluated in accordance with the criteria given in ASME Boiler and Pressure Vessel Code, Section VIII, Division 2. In particular, heat transfer analysis and consecutive thermal stress analysis for the junction between skirt and head can be carried out automatically in the skirt-tohead module. Finally, report including the above results is created automatically in Microsoft Word format.

• Structural Engineering and Mechanics
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• 제66권3호
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• pp.329-341
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• 2018

This paper considers the smooth receding contact problem between a homogeneous half-plane and a composite laminate composed of an inhomogeneously coated elastic layer. The inhomogeneity of the elastic modulus of the coating is approximated by an exponential function along the thickness dimension. The three-component structure is pressed together by either a concentrated force or uniform pressures applied at the top surface of the composite laminate. Both semianalytical and finite element analysis are performed to solve for the extent of contact and the contact pressure. In the semianalytical formulation, Fourier integral transformation of governing equations and boundary conditions leads to a singular integral equation of Cauchy-type, which can be numerically integrated by Gauss-Chebyshev quadrature to a desired degree of accuracy. In the finite element modeling, the functionally graded coating is divided into homogeneous sublayers and the shear modulus of each sublayer is assigned at its lower boundary following the predefined exponential variation. In postprocessing, the stresses of any node belonging to sublayer interfaces are averaged over its surrounding elements. The results obtained from the semianalytical analysis are successfully validated against literature results and those of the finite element modeling. Extensive parametric studies suggest the practicability of optimizing the receding contact peak stress and the extent of contact in multilayered structures by the introduction of functionally graded coatings.

• 대한수학회보
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• 제21권1호
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• pp.27-30
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• 1984

The concepts of the numerical range of an operator on a Hillbert space and on a Banach space were introduced by Toeplitz in 1918 and Bauer in 1962 respectively. Bauer's paper was concerned only with finite dimensional Banach spaces, but the concept of numerical range that he introduced is available without restriction of the dimension [1, 2]. In this paper, we define a C-algebra spatial numerical range of an operator on C-algebra valued inner product modules introduced by Paschke [4], and give analogous results on these modules as those on Banach spaces.

• 호남수학학술지
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• 제27권4호
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• pp.595-602
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• 2005

Comtrans algebras are modules equipped with two trilinear operations: a left alternative commutator and a translator satisfying the Jacobi identity, the commutator and translator being connected by the so-called comtrans identity. These identities have analogues for trilinear forms. On a given vector space, the set of all comtrans algebra structures itself forms a vector space. In this paper, the dimension of the space of comtrans algebra structures on a finite-dimensional vector space is determined.

• 대한수학회지
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• 제47권3호
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• pp.633-643
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• 2010

Let a be an ideal of a commutative Noetherian ring R, M a finitely generated R-module and N a weakly Laskerian R-module. We show that if N has finite dimension d, then $Ass_R(H^d_a(N))$ consists of finitely many maximal ideals of R. Also, we find the least integer i, such that $H^i_a$(M, N) is not consisting of finitely many maximal ideals of R.