• 대한수학회지
• /
• 제38권2호
• /
• pp.227-274
• /
• 2001

In this paper we intended to discuss the following topics: (1) Notation, generalities, Markov processes. The close relationship between (generators of) Markov processes and the martingale problem is exhibited. A link between the Korovkin property and generators of Feller semigroups is established. (2) Feynman-Kac semigroups: 0-order regular perturbations, pinned Markov measures. A basic representation via distributions of Markov processes is depicted. (3) Dirichlet semigroups: 0-order singular perturbations, harmonic functions, multiplicative functionals. Here a representation theorem of solutions to the heat equation is depicted in terms of the distributions of the underlying Markov process and a suitable stopping time. (4) Sets of finite capacity, wave operators, and related results. In this section a number of results are presented concerning the completeness of scattering systems (and its spectral consequences). (5) Some (abstract) problems related to Neumann semigroups: 1st order perturbations. In this section some rather abstract problems are presented, which lie on the borderline between first order perturbations together with their boundary limits (Neumann type boundary conditions and) and reflected Markov processes.

• 한국지하수토양환경학회:학술대회논문집
• /
• 한국지하수토양환경학회 2001년도 총회 및 춘계학술발표회
• /
• pp.77-80
• /
• 2001

The element-free Galerkin (EFG) method is one of meshless methods, which is an efficient method of modeling problems of fluid or solid mechanics with complex boundary shapes and large changes in boundary conditions. This paper discusses the theory of the EFG method and its applications to modeling of groundwater flow. In the EFG method, shape functions are constructed based on the moving least square (MLS) approximation, which requires only set of nodes. The EFG method can eliminate time-consuming mesh generation procedure with irregular shaped boundaries because it does not require any elements. The coupled EFG-FEM technique was introduced to treat Dirichlet boundary conditions. A computer code EFGG was developed and tested for the problems of steady-state and transient groundwater flow in homogeneous or heterogeneous aquifers. The accuracy of solutions by the EFG method was similar to that by the FEM. The EFG method has the advantages in convenient node generation and flexible boundary condition implementation.

• Interaction and multiscale mechanics
• /
• 제1권1호
• /
• pp.33-51
• /
• 2008

This paper investigates the modelling of coupled soil-structure interaction problems by domain decomposition techniques. It is assumed that the soil-structure system is physically partitioned into soil and structure subdomains, which are independently modelled. Coupling of the separately modelled partitioned subdomains is undertaken with various algorithms based on the sequential iterative Dirichlet-Neumann sub-structuring method, which ensures compatibility and equilibrium at the interface boundaries of the subdomains. A number of mathematical and computational characteristics of the coupling algorithms, including the convergence conditions and choice of algorithmic parameters leading to enhanced convergence of the iterative method, are discussed. Based on the presented coupling algorithms a simulation environment, utilizing discipline-oriented solvers for nonlinear structural and geotechnical analysis, is developed which is used here to demonstrate the performance characteristics and benefits of various algorithms. Finally, the developed tool is used in a case study involving nonlinear soil-structure interaction analysis between a plane frame and soil subjected to ground excavation. This study highlights the relative performance of the various considered coupling algorithms in modelling real soil-structure interaction problems, in which nonlinearity arises in both the structure and the soil, and leads to important conclusions regarding their adequacy for such problems as well as the prospects for further enhancements.

• 정보교육학회논문지
• /
• 제25권4호
• /
• pp.633-640
• /
• 2021

교육과 관련된 이슈는 다양한 집단과 상황이 서로 복잡하게 연계된 사회문제로 교육과 관련된 현상을 분석하여 이슈와 문제를 구체적으로 발견하는 것은 쉽지 않은 일이다. 한국어 기반 텍스트 분석은 정량적인 형태로 분석이 가능하고, 텍스트 분석기법의 발전에 따라 연구적인 성과를 내고 있어 교육과 관련된 이슈를 한국어 텍스트로 된 데이터에서 도출하는데 충분히 활용할 수 있다. 본 연구는 청와대 국민청원 홈페이지 게시판의 육아/교육 분야의 청원글을 수집하고 텍스트 분석방법을 활용하여 교육계의 이슈와 문제를 도출하고자 하였다. 분석은 토픽 모델링 기법 중 잠재 디리클레 할당(LDA)을 통해 6개 토픽을 도출하였고, 주요 키워드의 연관규칙을 분석하여 그래프로 시각화하였다. 기존의 설문을 통한 교육의 이슈를 도출하는 방법 이외에 추가로 텍스트 기반의 분석방법을 통해 이슈를 충분히 발견할 수 있다는 점에서 향후 연구의 방향과 정책에 시사점을 제공할 수 있다.

• 한국융합학회논문지
• /
• 제10권4호
• /
• pp.229-236
• /
• 2019

본 논문은 한국언론진흥재단이 운영하는 빅카인즈(Big KINDS)를 통하여 2018년 1월1일부터 12월 31일까지 언론 보도자료를 중십으로 체육계 병역특례와 관련된 여론, 관점과 흐름에 대한 자료를 수집 분석하여 사회적 현상 및 인식을 분석하려는 데에 그 목적이 있다. 이를 위하여 빅데이터 분석을 기반으로 사회적 현상에서 속에서 발견되는 문제점을 도출하기 위해 관련 키워드를 잠재 디리클레 할당 기법을 실행하여 토픽을 도출하고 시각화 하였다. 도출된 토픽은 '병역특례 재조명', '병역비리 논란', '체육분야 병역특례', '예술분야 대체복무 제도', '국정감사'의 5개이다. 이는 체육계 병역특혜와 관련된 사회적 논란에 대한 정확한 정보를 파악하여 정의롭고 평등부담원칙에 부합되면서도 스포츠선수의 특성이 고려된 현실적 방안을 마련할 기초자료로 사용될 수 있을 것이다.

• 한국IT서비스학회지
• /
• 제20권3호
• /
• pp.57-73
• /
• 2021

Recently, online job websites have been activated as unemployment problems have emerged as social problems and demand for job openings has increased. However, while the online job platform market is growing, users have difficulty choosing their jobs. When users apply for a job on online job websites, they check various information such as job contents and recruitment conditions to understand the details of the job. When users choose a job, they focus on various details related to the job rather than simply viewing and supporting the job title. However, existing online job websites usually recommend jobs using only quantitative preference information such as ratings. However, if recommendation services are provided using only quantitative information, the recommendation performance is constantly deteriorating. Therefore, job recommendation services should provide personalized services using various information about the job. This study proposes a recommended methodology that improves recommendation performance by elaborating on qualitative preference information, such as details about the job. To this end, this study performs a topic modeling analysis on the job content of the user profile. Also, we apply LDA techniques to explore topics from job content and extract qualitative preferences. Experiments show that the proposed recommendation methodology has better recommendation performance compared to the traditional recommendation methodology.

• 한국수학교육학회지시리즈B:순수및응용수학
• /
• 제13권4호
• /
• pp.281-294
• /
• 2006

Many partial differential equations defined on a rectangular domain can be solved numerically by using a domain decomposition method. The most commonly used decompositions are the domain being decomposed in stripwise and rectangular way. Theories for non-overlapping domain decomposition(in which two adjacent subdomains share an interface) were often focused on the stripwise decomposition and claimed that extensions could be made to the rectangular decomposition without further discussions. In this paper we focus on the comparisons of the two ways of decompositions. We consider the unconditionally stable scheme, the MIP algorithm, for solving parabolic partial differential equations. The SOR iterative method is used in the MIP algorithm. Even though the theories are the same but the performances are different. We found out that the stripwise decomposition has better performance.

• 한국수학교육학회지시리즈B:순수및응용수학
• /
• 제23권1호
• /
• pp.13-19
• /
• 2016

In this paper, we study some characterizations of unbounded domains. Among these, so-called G-domain is introduced by Cabre for the Aleksandrov-Bakelman-Pucci maximum principle of second order linear elliptic operator in a non-divergence form. This domain is generalized to wG-domain by Vitolo for the maximum principle of an unbounded domain, which contains G-domain. We study the properties of these domains and compare some other characterizations. We prove that sA-domain is wG-domain, but using the Cantor set, we are able to construct a example which is wG-domain but not sA-domain.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• 제5권1호
• /
• pp.55-78
• /
• 2001

Given the anisotropic Poisson equation $-{\nabla}{\cdot}{\mathcal{K}}{\nabla}p=f$, one can convert it into a system of two first order PDEs: the Darcy law for the flux $u=-{\mathcal{K}{\nabla}p$ and conservation of mass ${\nabla}{\cdot}u=f$. A very natural mixed finite volume method for this system is to seek the pressure in the nonconforming P1 space and the Darcy velocity in the lowest order Raviart-Thomas space. The equations for these variables are obtained by integrating the two first order systems over the triangular volumes. In this paper we show that such a method is really a standard finite element method with local recovery of the flux in disguise. As a consequence, we compare two approaches in analyzing finite volume methods (FVM) and shed light on the proper way of analyzing non co-volume type of FVM. Numerical results for Dirichlet and Neumann problems are included.

• 대한수학회논문집
• /
• 제35권4호
• /
• pp.1143-1158
• /
• 2020

In this paper, we are concerned with the blow-up phenomena for a class of pseudo-parabolic equations with weighted source u_t - △u - △u_t = a(x)f(u) subject to Dirichlet (or Neumann) boundary conditions in any smooth bounded domain Ω ⊂ ℝⁿ (n ≥ 1). Firstly, we obtain the upper and lower bounds for blow-up time of solutions to these problems. Moreover, we also give the estimates of blow-up rate of solutions under some suitable conditions. Finally, three models are presented to illustrate our main results. In some special cases, we can even get some exact values of blow-up time and blow-up rate.