• Steel and Composite Structures
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• 제15권1호
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• pp.41-55
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• 2013

This paper presents a numerical study of axially loaded concrete-filled steel tubular columns with "T" shaped cross section (CFTTS) based on the ABAQUS standard solver. Two types of columns with "T" shaped cross section, the common concrete-filled steel tubular columns with "T" shaped cross section (CCFTTS) and the double concrete-filled steel tubular columns with "T" shaped cross section (DCFTTS), are discussed. The failure modes, confining effects and load-displacement curves are analyzed. The numerical results indicate that both have the similar failure mode that the steel tubes are only outward buckling on all columns' faces. It is found that DCFTTS columns have higher axial capacities than CCFTTS ones duo to the steel tube of DCFTTS columns can plays more significant confining effect on concrete. A parametric study, including influence of tube thickness, concrete strength and friction coefficient of tube-concrete interface on the axial capacities is also carried out. Simplified formulae were also proposed based on this study.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1998년도 추계학술대회 논문집
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• pp.54-60
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• 1998

PSC box bridges by MSS construction method in high-speed railway may not be cast in place at one step. Web and bottom flange(U member) in the cross section are cast in place at first, then top flange will be cast in place later with some time lag. In this section, stress distributions of U member and top flange are different with those in generally complete cast in place cross section. In the composite section composed of two different aged members, the redistribution of stresses takes place. This results from time-dependent strain characteristics of concrete and the effects of forces applied at the various stages. For comparison in the present paper, two models, one with the composite cross section and the other with generally complete cast in place cross section, are analyzed. The longitudinal stress differences of two models on considering construction stages are compared. As the analysis results show the considerable differences in the stresses of cross section between two models, the composition of cross section is considered for rational design of PSC box girder bridge.

• Nuclear Engineering and Technology
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• 제56권3호
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• pp.933-940
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• 2024

A macroscopic cross section generation model was developed for the conceptual horizontal, compact high temperature gas reactor (HC-HTGR). Because there are many sources of spectral effects in the design and analysis of the core, conventional LWR methods have limitations for accurate simulation of the HC-HTGR using a neutron diffusion core neutronics simulator. Several super-cell model configurations were investigated to consider the spectral effect of neighboring cells. A new history variable was introduced for the existing library format to more accurately account for the history effect from neighboring nodes and reactivity control drums. The macroscopic cross section library was validated through comparison with cross sections generated using full core Monte Carlo models and single cell cross section for both 3D core steady-state problems and 2D and 3D depletion problems. Core calculations were then performed with the AGREE HTR neutronics and thermal-fluid core simulator using super-cell cross sections. With the new history variable, the super-cell cross sections were in good agreement with the full core cross sections even for problems with significant spectrum change during fuel shuffling and depletion.

• 대한기계학회논문집A
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• 제38권7호
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• pp.699-709
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• 2014

본 논문에서는 단일윤축 탈선이론을 적용하여 측풍 조건에서 주행 중인 철도차량의 탈선을 예측하는 방법을 제시하였다. 기존 연구에서는 측풍에 의한 탈선은 모두 전복탈선이라고 가정하여 탈선 예측 이론을 개발하였다. 그러나 이러한 가정은 특수한 주행조건하에서 차륜 타고오름 탈선의 가능성을 무시하고 있다. 또 기존의 측풍 탈선 이론은 주행 중 발생하는 차륜-궤도 사이의 마찰력, 동적상호작용과 같은 주행조건이 탈선에 미치는 영향을 고려할 수 없었다. 본 논문의 방법은 차륜-궤도 사이의 동적 영향, 횡가속도 및 켄트 영향, 측풍 영향 등을 동시에 고려할 수 있었다. 본 이론의 결과를 기존 이론 및 시뮬레이션 결과와 비교하여 타당성을 검증하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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• pp.615-620
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• 1997

The flow rate and the noise level of 18 cross flow fans were measured to analyze the effect of design variables on these and to finally find the optimal design value. These data were analyzed by the Taguchi method and the neural network. The optimal values obtained by the neural network showed good agreements with that by the Taguchi method. The effects of eight design variables on the fan performance and the noise were evaluated and discussed.

• Journal of the Korean Data and Information Science Society
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• 제6권1호
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• pp.63-71
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• 1995

We have consider the study of local influence for smoothing parameter estimates in spline regression model with heteroscedasticity. Practically, generalized cross-validation does not work well in the presence of heteroscedasticity. Thus we have proposed the local influence measure for generalized cross-validation estimates when errors are heteroscedastic. And we have examined effects of diagnostic by above measures through Hyperinflation data.

• Geomechanics and Engineering
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• 제15권5호
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• pp.1039-1046
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• 2018

This paper presents a limit analysis of the series of construction stages of shallow tunneling method by investigating their respective safety factors and failure mechanisms. A case study for one particular cross-section of Beijing Subway Line 7 is undertaken, with a focus on the effects of multiple soil layers and construction sequencing of dual tunnels. Results show that using the step-excavation technique can render a higher safety factor for the excavation of a tunnel compared to the entire cross-section being excavated all at once. The failure mechanisms for each different construction stage are discussed and corresponding key locations are suggested to monitor the safety during tunneling. Simultaneous excavation of dual tunnels in the same cross-section should be expressly avoided considering their potential negative interactions. The normal and shear forces as well as bending moment of the primary lining and locking anchor pipe are found to reach their maximum value at Stage 6, before closure of the primary lining. Designing these struts should consider the effects of different construction stages of shallow tunneling method.

• 한국유체기계학회 논문집
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• 제1권1호
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• pp.41-48
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• 1998

This study was carried out to investigate the effect of design parameters on the volume flow-rate and the noise level and to finally find the optimal design variables. Eighteen cross-flow fans were designed by the method of orthogonal array, and the flow-rate and the noise level were measured. These data were analyzed by the neural network system. The effects of eight design variables(scroll exit angle, scroll arc length et al.) on the fan performance and the noise level were valuated and discussed. This experiment shows that the design solutions suggested by neural network system may increase its volume flow-rate and reduce noise simultaneously.

• 자원환경지질
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• 제33권1호
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• pp.41-50
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• 2000

Geo-radar survey which has the advantage of high-resolution and relatively fast survey has been widely used for engineering and environmental problems. Three-dimensional effects have to be considered in the interpretation of geo-radar for high-resolution. However, there exists a trouble on the analysis of the three dimensional effects. To solve this problem an efficient three dimension numerical modeling algorithm is needed. Numerical radar modeling in three dimensional case requires large memory and long calculating time. In this paper, a finite difference method time domain solution to Maxwell's equations for simulating electromagnetic wave propagation in three dimensional media was developed to make economic algorithm which requires smaller memory and shorter calculating time. And in using boundary condition Liao absorption boundary. The numerical result of cross-hole radar survey for tunnel is compared with real data. The two results are well matched. To prove application to three dimensional analysis, the results with variation of tunnel's incident angle to survey cross-section and the result when the tunnel is parallel to the cross-section were examined. This algorithm is useful in various geo-radar survey and can give basic data to develop dat processing and inversion program.

• 한국음향학회:학술대회논문집
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• 한국음향학회 2004년도 춘계학술발표대회 논문집 제23권 1호
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• pp.297-300
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• 2004

Perforated elements are extensively used in mufflers for the intake and exhaust systems of various fluid machines. Perforated elements are usually exposed to grazing flow or cross flow. For analyzing performances of mufflers, the impedance of perforated elements with mean flow is very important. The impedance of perforates under both conditions are measured with different experimental setups. Even if there is no flow, the preceding experimental method for grazing flow shows different values with both theoretical ones and measured under cross flow setup. Using high-order analysis considering phase differences, the experimental method for grazing flow can be modified. The acoustical impedance of perforated impedance contains interaction effects between orifices. After correcting these effects, the measured impedance with grazing flow setup show similar results with both theoretical impedance and measured ones under cross flow setup.