• Computers and Concrete
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• v.24 no.6
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• pp.513-525
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• 2019

In this work, an experimental research has been performed on Steel Fiber-Steel Reinforced Concrete (SFSRC)specimens subjected to four-point bending tests to evaluate the feasibility of mutual replacement of steel fibers and conventional reinforcement through studying failure modes, load-deflection curves, stiffness of characteristic points, stiffness degradation curves and damage analysis. The variables considered in this experiment included steel fiber volume percentage with and without conventional reinforcements (stirrups or steel fibers) with shear span depth ratios of S/D=2.5 and 3.5. Experimental results revealed that increasing the volume percentage of steel fiber decreased the creation and propagation of shear and bond cracks, just like shortening the stirrups spacing. Higher crack resistance and suturing ability of steel fiber can improve the stability of its bearing capacity. Both steel fibers and stirrups improved the stiffness and damage resistance of specimens where stirrups played an essential role and therefore, the influence of steel fibers was greatly weakened. Increasing S/D ratio also weakened the effect of steel fibers. An equation was derived to calculate the bending stiffness of SFSRC specimens, which was used to determine mid span deflection; the accuracy of the proposed equation was proved by comparing predicted and experimental results.

• Polymer(Korea)
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• v.35 no.3
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• pp.232-237
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• 2011

The relaxation spectra of polyacrylonitrile-poly(vinyl chloride) copolymer filament fibers were obtained by applying the experimental stress relaxation curves to the theoretical equation of relaxation spectrum. The theoretical equation of relaxation spectrum was derived from the Ree-Eyring and Maxwell model. The experimental of stress relaxation was carried out using a tensile tester with a solvent chamber. The determination of relaxation spectra was performed by computer calculation. From the relaxation spectra, the fine structures, viscoelastic properties and hole volumes of solid polymers were studied. It was observed that the relaxation spectra of these samples were directly related to the distribution of molecular weights and self diffusions of flow segments.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.718-733
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• 2021

A prediction method, based on the Morison equation as well as Froude-Krylov formula, is presented to simulate the loads acting on the columns and caissons of the semi-submersible platform induced by Internal Solitary Wave (ISW) respectively. Combined with the experimental results, empirical formulas of the drag and inertia coefficients in Morison equation can be determined as a function of the Keulegan-Carpenter (KC) number, Reynolds number (Re) and upper layer depth h₁/h respectively. The experimental and calculated results are compared. And a good agreement is observed, which proves that the present prediction method can be used for analyzing the ISW-forces on the semi-submersible platform. Moreover, the results also demonstrate the layer thickness ratio has a significant effect upon the maximum horizontal forces on the columns and caissons, but both minimum horizontal and vertical forces are scarcely affected. In addition, the incoming wave directions may also contribute greatly to the values of horizontal forces exerted on the caissons, which can be ignored in the vertical force analysis.

• Proceedings of the KSPS conference
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• 1996.10a
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• pp.333-336
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• 1996

It is widely known that the Japanese alveolar nasal (n) is affected by adjacent vowels in most positions, that is, the variants of the alveolar (n) occur conditionally. The Japanese (n) is palatalized under the influence of vowel (i) or palatal (j). In the articulation of (ni), for instance, the tip and sides of the tongue make wide contact with the palate. It is interesting to know how palatalization occurs and varies during the production in different contexts. In my presentation, the actual realization of the palatalized alveolar nasal in different contexts is examined and clarified by consider me the Electro-palatographic data and examining the articulatory feel ins and auditory impression. As a result, palatalized (equation omitted) occurs either word-initially or inter-vocalically. (equation omitted) in (equation omitted) and (equation omitted) has great palatality. When conditioned by (j), the (equation omitted) in (equation omitted), (equation omitted) and (equation omitted) has full palatality. In each sound the average number of contacted electrodes of the Electro-palatograph at maximum tongue-palate contact is 63 or 100% of the total. To summarize the experimental data, articulatory feel ins and auditory impression, it can be concluded that the (n) followed by or hemmed in (i), (j) is a palatalized nasal (equation omitted).

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.2
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• pp.87-97
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• 2013

Recently the use of gas spring in the combat and commercial vehicle's suspension is increasing. Because of its nonlinear characteristics, the gas spring can support wide range of dynamic loads and gives good ride quality. In design of gas spring, isothermal and adiabatic processes are applied generally, but those processes could not produce heat transfer effect in the simulation. So in this study, heat transfer differential equation and BWR/Ideal state equation are used to calculate the pressure of gas spring which is changing with time. The numerical analysis showed that the pressure of gas spring forms a hysteresis loop in the both of the state equations. But the peak pressure value of BWR equation over 0.1Hz frequency are higher than that of adiabatic process. And the test results showed that the differences between test results and ideal gas equation are smaller than those of BWR equation, so the ideal equation is more accurate than BWR equation in this case.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.1
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• pp.18-24
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• 2015

In this study, a $CO_2$ air-conditioning system was investigated with different types of electrically driven compressors, parallel flow type gas cooler, four-pass type evaporator, internal heat exchanger integrated with accumulator, and electric expansion valve. The experimental study was conducted under various operating conditions (ie., different rotational compressor speeds, air inlet temperatures and air velocity coming into heat exchangers). The experimental results showed the cooling capacity was 3.5kW at $35^{\circ}C$ ambient temperature when the vehicle was idle (ie., the worst condition for cooling off the gas cooler). In terms of performance effect of the compressor, the e-RP model had a slightly better cooling capacity and coefficient of performance than the e-GR model under the same test conditions. An experimental equation for optimum cooling-performance control was also suggested based on the results. A high-pressure control algorithm for the super critical cycle was determined to achieve both maximum cooling performance and efficient energy consumption. The results from the experimental equation coincided with those of previous experimental studies.

• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.104-111
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• 2009

The existing code which solves two-dimensional RANS(Reynolds Averaged Navier-Stokes) equations and 2-equation turbulence model equations was modified to enable numerical simulation of various supersonic flows. For this, various boundary conditions have been implemented to the code. Bleed boundary condition was incorporated into the code for calculating wall mean flow quantities. Furthermore, the boundary conditions for the turbulence quantities along rough surfaces as well as porous walls were applied to the code. The code was verified and validated by comparing the computational results against the experimental data for the supersonic flows over bleed region on a flat plate. Using the newly modified code, numerical simulations were performed and compared with other computational results as well as the experimental data for the supersonic flows over an oblique shock with a bleed region.

• Structural Engineering and Mechanics
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• v.66 no.4
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• pp.423-438
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• 2018

This pioneer study focuses on finite element modeling and numerical modeling of three types of Reinforced Concrete Haunched Beams (RCHBs). Firstly, twenty RCHBs, consisting of three types, and four prismatic beams which had been tested experimentally were modeled via a nonlinear finite element method (NFEM) based software named as, ATENA. The modeling results were compared with experimental results including load capacity, deflection, crack pattern and mode of failure. The comparison showed a good agreement between the results and thus the model used can be effectively used for further studies of RCHB with high accuracy. Afterwards, new mechanism modes and design code equations were proposed to improve the shear design equation of ACI-318 and to predict the critical effective depth. These equations are the first comprehensive formulas in the literature involving all types of RCHBs. The statistical analysis showed the superiority of the proposed equation to their predecessors where the correlation coefficient, $R^2$ was found to be 0.89 for the proposed equation. Moreover, the new equation was validated using parametric and reliability analyses. The parametric analysis of both experimental and predicted results shows that the inclination angle and the compressive strength were the most influential parameters on the shear strength. The reliability analysis indicates that the accuracy of the new formulation is significantly higher as compared to available design equations and its reliability index is within acceptable limits.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.6
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• pp.1552-1560
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• 1990

A general form of the mathematical function in the fatigue crack growth rate law for CT specimens was determined by means of the dimensional analysis at elevated temperatures. The experimental results can be rigorously described by the combination of rate theory and fracture mechanics. The rate theory approach extends the scope of fracture mechanics through the consideration of the temperature. The fatigue crack growth rates are represented by the Arrhenius type equation. This equation explains fairly well the experimental data for Cr-Mo-V rotor steel and A517-F steel in the comparatively wide temperature regions as affected with the temperature and the stress intensity factor range interaction.

• Fire Science and Engineering
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• v.18 no.3
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• pp.9-17
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• 2004

The values of physical properties of the inert gases of Ar, $N_2$, $CO_2$ were calculated by the empirical equations. The regression coefficients were obtained by the experimental data and the resulting calculated values. For the empirical equation with a lower regression coefficient, a new correlation was suggested. At an atmosphere pressure, the empirical equation was confirmed by the experimental values for the viscosity, density, saturated pressure, and surface tension of Ar, $N_2$, $CO_2$. The correlation coefficients of the empirical equations proposed in this work was higher than 0.99.