• 한국컴퓨터정보학회논문지
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• 제12권4호
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• pp.33-42
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• 2007

소프트웨어 제품의 정확한 인도시기를 예측하거나 효용성 및 신뢰성을 예측하기 위해서는 소프트웨어 테스팅 과정에서 중요한 요소인 테스트 커버리지를 이용하면 보다 효율적인 테스팅 작업을 할 수 있다. 이런 모형을 ENHPP모형이라고 한다. 본 논문에서는 기존의 소프트웨어 신뢰성 모형인 지수 커버리지 모형과 S-커버리지 모형을 재조명하고 이 분야에 적용될 수 있는 Burr 분포에 기초한 Burr 커버리지 모형을 제안하였다. 고장 간격 시간으로 구성된 자료를 이용한 모수추정 방법은 최우추정법 과 일반적인 수치해석 방법인 이분법을 사용하여 모수 추정을 실시하고 효율적인 모형 선택은 편차자승합(SSE) 및 콜모고로프 거리를 적용하여 모형들에 대한 효율적인 모형선택도 시도하였다. NTDS 자료를 사용한 임무시간 비교 분석한 결과 Burr 커버리지 모형 시행이 지수나 S-형 모형보다 우수함을 보이고 있다. 이 자료들에서 기존의 모형과 Burr 커버리지 모형의 비교를 위하여 산술적 및 라플라스 검정, 편의 검정등을 이용하였다.

• 대한교통학회지
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• 제25권5호
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• pp.209-231
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• 2007

이 논문은 통행선택행위를 간접효용함수 대신 체감비용을 비교하는 평가방법을 제시하였다. 체감비용 비교방법은 가계생산이론을 통행자가 통행비용과 시간 등 정량적 요소와 함께 안락성과 안전성 등 정량적 요소를 동시에 고려하는 경우에 적용하여 도출되었다. 이 분석에서는 통행행위가 통행목적 달성과 함께 여러 정성적 요소를 동시에 산출하는 과정을 기술하는 특수한 형태의 동차 공동생산함수를 고안하여 이용하였다. 통행대안별 체감비용은 금전적인 통행비용에 시간가치 중에서 정량적 요소에 대해 통행자가 느끼는 기회비용을 제한 값을 합하여 산출하였다. 이러한 체감비용은 통계적 측정가능조건을 충족시킬뿐더러 통행선택행위를 보다 합리적으로 설명할 수 있어, 통행선택에 대한 통계분석에서 간접효용함수에 비해 통계측정 대상으로서 보다 우수하다.

• 한국산학기술학회논문지
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• 제19권12호
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• pp.41-46
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• 2018

본 연구에서는 바이오가스 기반 예혼합 압축착화(Homogeneous charged compression ignition, HCCI) 엔진에 수소를 첨가하였을 때, 연소실 내부 압력, 온도 배출가스에 미치는 영향에 대해 살펴보았다. 자세히는 수소 첨가량과 과다공기량(${\lambda}$) 변화에 따른 연소실 압력 온도, 그리고 생성물로서의 NO, $CO_2$ 배출 특성을 화학 반응 해석 프로그램을 사용하여 고찰하였다. 대상의 엔진은 2300cc 바이오가스 엔진 발전기로서 압축비 13:1, 발전량 15kW 급이다. 과급압은 1.2bar 고정 조건이며, rpm은 1800rpm의 정속 조건이다. 엔진 연소 방식은 예혼합 압축 착화를 모사하였다. 본 연구를 진행하기에 앞서 바이오가스의 주요 조성인 메탄의 연소 및 산화 메커니즘에 대한 선행 연구에 대한 고찰을 통하여 연소반응 메커니즘을 규명하기 위한 반응 메커니즘 연구 기술의 경향을 살펴보고, 본 연구에 적용 가능한 반응 메커니즘을 선정하여 해석을 진행하였다. 수소를 첨가할 때 NO는 증가하는 반면, $CO_2$등의 배출량은 감소하였고 실린더 내부 압력이 상승하며, 상승 구간이 진각 됨을 알 수 있었다. 또한, 희박영역에서 수소 첨가가 가연 한계를 증가시켰다.

• Steel and Composite Structures
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• 제44권5호
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• pp.721-740
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• 2022

In this paper, an accurate kinematic model has been developed to study the mechanical response of functionally graded (FG) sandwich beams, mainly covering the bending, buckling and free vibration problems. The studied structure with homogeneous hardcore and softcore is considered to be simply supported in the edges. The present model uses a new refined shear deformation beam theory (RSDBT) in which the displacement field is improved over the other existing high-order shear deformation beam theories (HSDBTs). The present model provides good accuracy and considers a nonlinear transverse shear deformation shape function, since it is constructed with only two unknown variables as the Euler-Bernoulli beam theory but complies with the shear stress-free boundary conditions on the upper and lower surfaces of the beam without employing shear correction factors. The sandwich beams are composed of two FG skins and a homogeneous core wherein the material properties of the skins are assumed to vary gradually and continuously in the thickness direction according to the power-law distribution of volume fraction of the constituents. The governing equations are drawn by implementing Hamilton's principle and solved by means of the Navier's technique. Numerical computations in the non-dimensional terms of transverse displacement, stresses, critical buckling load and natural frequencies obtained by using the proposed model are compared with those predicted by other beam theories to confirm the performance of the proposed theory and to verify the accuracy of the kinematic model.

• Journal of applied mathematics & informatics
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• 제7권2호
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• pp.493-506
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• 2000

Recently the first author and his coworker report a new finite element method for the Poisson equations with homogeneous Dirichlet boundary conditions on a polygonal domain with one re-entrant angle [7], They use the well-known fact that the solution of such problem has a singular representation, deduced a well-posed new variational problem for a regular part of solution and an extraction formula for the so-called stress intensity factor using tow cut-off functions. They use Fredholm alternative an Garding's inequality to establish the well-posedness of the variational problem and finite element approximation, so there is a maximum bound for mesh h theoretically. although the numerical experiments shows the convergence for every reasonable h with reasonable size y imposing a restriction to the support of the extra cut-off function without using Garding's inequality. We also give error analysis with similar results.

• The Korean Journal of Physiology
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• 제27권2호
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• pp.123-138
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• 1993

The mechanism of insulin action to increase glucose transport is attributed to glucose transporter translocation from intracellular storage pools to the plasma membrane in insulin-sensitive cells. The present study was designed to visualize the redistribution of the glucose transporter by means of an immunogold labelling method. Our data clearly show that glucose transporter molecules were visible by this method. According to the method this distribution of glucose transporters between cell surface and intracellular pool was different in adipocytes. The glucose transporter molecules were randomly distributed at the cell surface whereas the molecules at LDM were farmed as clusters. By insulin treatment the number of homogeneous random particles increased at the cell surface whereas the cluster forms decreased at the intracellular storage pools. It suggests that the active molecules needed to be evenly distributed far effective function and that the inactive molecules in storage pools gathered and termed clusters until being transferred to the plasma membrane.

• Journal of the Optical Society of Korea
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• 제17권2호
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• pp.130-135
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• 2013

Based on the extended Huygens-Fresnel principle and generalized Stokes theory, the evolution of polarization properties of beams generated by quasi-homogenous (QH) sources propagating in clear oceanic water was studied by the use of the oceanic turbulence spatial spectrum function. The results show that the beams have similar polarization self-reconstructed behavior under different turbulence conditions in the far field, but if the propagation distance is not long enough, the degree of polarization (DOP) fluctuates with much more complexity than state of polarization (SOP) of QH beams. The self-reconstructed ability of DOP at the special distance in turbulence would get to the best value if the values of coherence of width were chosen suitably, but for SOP, it has no best value.

• 영어어문교육
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• 제12권1호
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• pp.257-286
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• 2006

This paper investigates the effects of small group collaborative transcription activities on the improvement of university students' English listening ability. Based on the results of pre-tests, a class of 42 students was subdivided into 11 small homogeneous groups of three to four students. Each group was provided with 7 different news items to be transcribed. Means were compared between pre-test and post-test scores, followed by comparison of transcription errors in content and function words. Finally, students' perception and attitudes about the use of small group transcription for improving listening skills were qualitatively analysed and compared with pre- and post test results. It was found that post test scores highly correlated with improvement of listening ability. It was also found that groups of high degree of collaboration showed improvement in listening ability while lack of collaboration contributed to loss of interests in listening. Students who see process more important were found to make more contribution to the group success than those who place more emphasis on the results.

• 호남수학학술지
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• 제38권3호
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• pp.661-674
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• 2016

In [15] they introduced a new finite element method for accurate numerical solutions of Poisson equations with corner singularities, which is useful for the problem with known stress intensity factor. They consider the Poisson equations with homogeneous Dirichlet boundary condition, compute the finite element solution using standard FEM and use the extraction formula to compute the stress intensity factor, then they pose a PDE with a regular solution by imposing the nonhomogeneous boundary condition using the computed stress intensity factor, which converges with optimal speed. From the solution we could get accurate solution just by adding the singular part. This approach works for the case when we have the accurate stress intensity factor. In this paper we consider Poisson equations with mixed boundary conditions and show the method depends the accrucy of the stress intensity factor by considering two algorithms.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.658-662
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• 2004

This paper develops a stability analysis and controller synthesis methodology for a continuous-time affine Takagi-Sugeno (T-S) fuzzy systems with parametric uncertainties. Affine T-S fuzzy system can be an advantage because it may be able to approximate nonlinear functions to high accuracy with fewer rules than the homogeneous T-S fuzzy systems with linear consequents only. The analysis is based on Lyapunov functions that are continuous and piecewise quadratic. The search for a piecewise quadratic Lyapunov function can be represented in terms of bilinear matrix inequalities (BMIs). A simulation example is given to illustrate the application of the proposed method.