• Structural Engineering and Mechanics
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• v.22 no.2
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• pp.223-240
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• 2006

Taking into account the geometrical and material nonlinearities, an ultimate behavior of reinforced concrete cooling tower shell in hyperbolic configuration is presented. The design wind pressures suggested in the guidelines of the US (ACI) and Germany (VGB), with or without the effect of internal suction, are employed in the analysis to examine the qualitative and quantitative characteristics of each design wind pressure. The geometrical nonlinearity is incorporated by the Green-Lagrange strain tensor. The nonlinear features of concrete, such as the nonlinear stress-strain relation in compression, the tensile cracking with the smeared crack model, an effect of tension stiffening, are taken into account. The biaxial stress state in concrete is represented by an improved work-hardening plasticity model. From the perspective of quality of wind pressures, the two guidelines are determined as highly correlated each other. Through the extensive analysis on the Niederaussem cooling tower in Germany, not only the ultimate load is determined but also the mechanism of failure, distribution of cracks, damage processes, stress redistributions, and mean crack width are examined.

• Structural Engineering and Mechanics
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• v.39 no.5
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• pp.661-667
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• 2011

In the famous equivalent elasticity modulus method proposed by Ernst for the geometrical nonlinear analysis of stay cables, the cable shape was assumed as a parabolic curve, and only a part of the gravity load normal to the chord was taken into account with the other part of gravity load parallel to the chord being ignored. Using the actual catenary curve and considering the entire gravity load of stay cables, the present study has derived the equivalent stiffness method to analyze the sag effect of stay cables in cable-stayed bridges. The derived equivalent stiffness can be degenerated into Ernst's equivalent elasticity modulus method with some approximations. Therefore, the Ernst's method is a special and approximate formulation of the present method. The derived equivalent stiffness provides a theoretical explanation for the famous Ernst's formula.

• Journal of the Korean Chemical Society
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• v.57 no.1
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• pp.20-24
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• 2013

The effect of the DFT methods and basis sets on harmine molecule has been investigated. 26 DFT methods with 6 basis sets were used. Two main comparison chosen DFT methods in this work has been investigated. It is concluded that this contribution is very important and cannot be neglected. In the following analysis, changes in energy levels were investigated by two different methods. Considering a specific basis set, changes in energy levels were obtained using different DFT methods. A specific DFT method is chosen and changes in energy levels have been investigated by means of various basis sets. Effect of the choice of basis sets on geometrical parameters on harmine molecule has also been investigated.

• International Journal of Air-Conditioning and Refrigeration
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• v.15 no.4
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• pp.163-168
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• 2007

The feature of six existing condensation heat transfer correlations for microfin tubes were evaluated with the consideration of vapor quality, mass flux, geometries, and various refrigerants. The Kosky and Staub [15] and the Jaster and Kosky [16] correlations for smooth tube were used for the evaluation of the heat transfer enhancement factor (EF). For the prediction of zeotropic mixtures, most correlations show discrepancy with previous measurements. The Yu and Koyama [4] and the Shikazono et al. [8] correlations do not consider spiral angle effect. The Han and Lee [10] correlation shows fin height growth deteriorates heat transfer. Experimental verification to develop reliable condensation heat transfer correlation for microfin tubes is still needed with the consideration of geometrical effects and working conditions.

• Ocean Systems Engineering
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• v.13 no.2
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• pp.97-121
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• 2023

Through-the-thickness stress distribution in a tubular member has a profound effect on the fatigue behavior of tubular joints commonly found in steel offshore structures. This stress distribution can be characterized by the degree of bending (DoB). Although multi-planar joints are an intrinsic feature of offshore tubular structures and the multi-planarity usually has a considerable effect on the DoB values at the brace-to-chord intersection, few investigations have been reported on the DoB in multi-planar joints due to the complexity of the problem and high cost involved. In the present research, data extracted from the stress analysis of 243 finite element (FE) models, verified based on available parametric equations, was used to study the effects of geometrical parameters on the DoB values in two-planar tubular DYT-joints. Parametric FE study was followed by a set of nonlinear regression analyses to develop six new DoB parametric equations for the fatigue analysis and design of axially loaded two-planar DYT-joints.

• 전기의세계
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• v.29 no.8
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• pp.524-531
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• 1980

In order to investigate the effect of inorganic dielectric fine particle mixed in Low Density Polyethylene on the deterioration by treeing, a comparative study for initiation and development of the tree has been carried out between the pure thin film specimen and the same geometrical specimen mixed with a constant weight percent by a defiend particle size of $Al_{2}$O$_{3}$ and SiO$_{2}$, having larger dielectric constants than that of the base material. According to the results, it has been observed that as increasing dielectric constant, the initiation of tree is expedited, however, the development of the tree reached at the surface of filler particles shows the suppressive trends. From these facts, a reasonable interpretation may be possible by considering the effect of intensified electrical field around the tip in the presence of filler particles, that the initiation and the development of tree are a mechanical break down process caused by Maxwell stress due to the concentration of electrical field at the tip. This suppressive effect is specifically suggestive for the reason that a discharge route must be constructed around the particle surface because of the intensified field strength near filler, which, in turn, reduces the geometrical curvature of the tip so that the local intensity of electrical field can be relaxed. Further more an experimental evidence for this assumption was able to observe in this investigation.

• Korean Journal of Optics and Photonics
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• v.15 no.4
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• pp.287-292
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• 2004

This paper presents the effect of scratches on an optical connector interface surface on the insertion loss of optical connectors. We propose a model for calculating the insertion loss of optical connectors. The model is expressed in terms of geometrical parameters of scratches assuming that the transmission coefficient of a light wave on the scratch surfaces is linearly varied as a function of scratch depth. Geometrical parameters of scratches such as location, width, and depth of scratches are measured using 3D optical interferometry surface profiler. We obtain the equation of the transmission coefficient in terms of scratch depth comparing the experimental insertion loss data to the insertion loss data using the model presented in this paper. Using the model and the equation of the transmission coefficient presented in this paper, we present the results of the insertion loss of optical connectors for various geometrical parameters of scratches. Scratches which are located at longer than two times the core radius from the center of the core show negligible effect on the insertion loss of optical connectors.

• Journal of Hydrogen and New Energy
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• v.12 no.4
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• pp.247-255
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• 2001

The relation between the deformation and the geometrical shape, and the effect of cold work on the hydrogen absorption behavior in palladium were investigated. The Pd specimens used were plates and wires as cold worked and annealed states. The palladium plates and wires were loaded with hydrogen by electrochemical method. Experimental analyses were carried out through X -ray diffraction, micrometer measurement and decimal balance measurement. As the results, it is found that the effect of cold work on hydrogen absorption capacity was relatively small. The deformation of the palladium plates in thickness direction is larger than in other lateral directions whereas the palladium wires showed the same deformation ratio in all radius directions because of the circular distribution of coexisting $\alpha$ and $\beta$ phases. The products of plastic deformation such as slip lines and voids etc. were observed abundantly in all specimens although the specimens had undergone only once of a hydrogen absorption and desorption.

• Nuclear Engineering and Technology
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• v.55 no.4
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• pp.1400-1409
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• 2023

In this study, three condensation models of the CUPID code, i.e., the resolved boundary layer approach (RBLA), heat and mass transfer analogy (HMTA) model, and an empirical correlation, were tested and validated against the COPAIN and CAU tests. An improvement on HMTA model was also made to use well-known heat transfer correlations and to take geometrical effect into consideration. The RBLA was a best option for simulating the COPAIN test, having mean relative error (MRE) about 0.072, followed by the modified HMTA model (MRE about 0.18). On the other hand, benchmark against CAU test (under natural convection and occurred on a slender tube) indicated that the modified HMTA model had better accuracy (MRE about 0.149) than the RBLA (MRE about 0.314). The HMTA model with wall function and the empirical correlation underestimated significantly, having MRE about 0.787 and 0.55 respectively. When using the HMTA model, consideration of geometrical effect such as tube curvature was essential; ignoring such effect leads to significant underestimation. The HMTA and the empirical correlation required significantly less computational resources than the RBLA model. Considering that the HMTA model was reasonable accurate, it may be preferable for large-scale simulations of containment.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.1113-1118
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• 2006

A numerical investigation of single phase heat and flow characteristics in circular tubes with a single set of spiral micro fins was performed with varying geometrical parameters like fin height, spiral angle, and number of fins. The properties of $40^{\circ}C$ water was used as a working fluid to simulate a condenser and the RNG $k-{\epsilon}$ turbulence model was adopted. Calculation results were obtained in fully developed turbulent flow with constant surface heat flux boundary condition. Relative terms were introduced to investigate the substitution effect of conventional smooth tubes. The dimensionless terms were the heat transfer enhancement factor, the pressure drop penalty factor, and the efficiency index. Additionally, a numerical optimization was carried out to maximize thermal performance with the concept of the robust design. A statistical analysis showed that fin height interacts with number of fins and spiral angle.