• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.13-18
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• 2010

This study aim to investigate the internal mixing flow characteristics by recess length of swirl coaxial injector for gas generator has propellant of Kerosene-LOx. Recess length is a very important element, have influence in spray stability and LOx post damage. The influence of recess length was analyzed by visualizing internal flow and measuring liquid film thickness and manifold pressures. Also, frequency characteristics were analyzed by liquid film thickness measurement with mixing time.

• Advances in nano research
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• v.12 no.3
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• pp.337-344
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• 2022

In this work, the vibrational frequency of two layered FGM cylindrical shell with and without the effects of internal pressure under ring support are discussed in detailed. The functionally graded materials of a cylindrical shell are designed for specific purpose and studied under various boundary conditions. The Love shell dynamical equations theory is utilized to find the relationship between the curvature displacement and strain displacement. Natural frequency vibrations are analyzed by using volume polynomial for bi-layered FGM shell under ring support both for with and without internal pressures.

• Geotechnical Engineering
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• v.6 no.2
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• pp.35-46
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• 1990

An analytical solution method is described to estimate the developed static and dynamic horizontal earth pressures behind a vertical or inclined rigid wall experiencing outward toranslational movement. The results predicted by the developed method of analysis are compared with chose from the experimental model testg on sandy. The comparisons show good agreements at various stases of wall movement. When the wall i9 inclined with a certain angle in the direction of the supported strand sass, the effects of reduction in developed static and dynamic horizontal earth pressures are also analyzed. Finally, results of analytical parametric study are presented to demonstrate the effects of various parameters, such as wall friction angle and internal strand friction angle.

• Wind and Structures
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• v.27 no.1
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• pp.11-27
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• 2018

The straight-cone steel cooling tower is a novel type of structure, which has a distinct aerodynamic distribution on the internal surface of the tower cylinder compared with conventional hyperbolic concrete cooling towers. Especially in the extreme weather conditions of strong wind and heavy rain, heavy rain also has a direct impact on aerodynamic force on the internal surface and changes the turbulence effect of pulsating wind, but existing studies mainly focus on the impact effect brought by wind-driven rain to structure surface. In addition, for the indirect air cooled cooling tower, different additional ventilation rate of shutters produces a considerable interference to air movement inside the tower and also to the action mechanism of loads. To solve the problem, a straight-cone steel cooling towerstanding 189 m high and currently being constructed is taken as the research object in this study. The algorithm for two-way coupling between wind and rain is adopted. Simulation of wind field and raindrops is performed with continuous phase and discrete phase models, respectively, under the general principles of computational fluid dynamics (CFD). Firstly, the rule of influence of 9 combinations of wind sped and rainfall intensity on flow field mechanism, the volume of wind-driven rain, additional action force of raindrops and equivalent internal pressure coefficient of the tower cylinder is analyzed. On this basis, the internal pressures of the cooling tower under the most unfavorable working condition are compared between four ventilation rates of shutters (0%, 15%, 30% and 100%). The results show that the 3D effect of equivalent internal pressure coefficient is the most significant when considering two-way coupling between wind and rain. Additional load imposed by raindrops on the internal surface of the tower accounts for an extremely small proportion of total wind load, the maximum being only 0.245%. This occurs under the combination of 20 m/s wind velocity and 200 mm/h rainfall intensity. Ventilation rate of shutters not only changes the air movement inside the tower, but also affects the accumulated amount and distribution of raindrops on the internal surface.

• Geomechanics and Engineering
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• v.20 no.1
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• pp.29-41
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• 2020

It is extremely important to obtain rock strength parameters for geological engineering. In this paper, the evolution of sandstone cohesion and internal friction angle with plastic shear strain was obtained by simulating the cyclic loading and unloading tests under different confining pressures using Particle Flow Code software. By which and combined with the micro-crack propagation process, the mesoscopic mechanism of parameter evolution was studied. The results show that with the increase of plastic shear strain, the sandstone cohesion decreases first and then tends to be stable, while the internal friction angle increases first, then decreases, and finally maintains unchanged. The evolution of sandstone shear strength parameters is closely related to the whole process of crack formation, propagation and coalescence. When the internal micro-cracks are less and distributed randomly and dispersedly, and the rock shear strength parameters (cohesion, internal friction angle) are considered to have not been fully mobilized. As the directional development of the internal micro-fractures as well as the gradual formation of macroscopic shear plane, the rock cohesion reduces continuously and the internal friction angle is in the rise stage. As the formation of the macroscopic shear plane, both the rock cohesion and internal friction angle continuously decrease to a certain residual level.

• Journal of Mechanical Science and Technology
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• v.17 no.4
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• pp.477-483
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• 2003

An independent kinematic hardening material model in which the reverse yielding point is defined by the Bauschinger effect factor (BEF) , has been defined for stainless steel SUS 304. The material model and the BEF are obtained experimentally and represented mathematically as continuous functions of effective plastic strain. The material model has been incorporated in a non-linear stress analysis for the prediction of reverse yielding in thick-walled cylinders during the autofrettage process of these vessels. Residual stress distributions of the independent kinematic hardening material model at the onset of reverse yielding are compared with residual stresses of an isotropic hardening model showing the significant effect of the BEF on reverse yielding predictions. Critical pressures of direct and reverse yielding are obtained for the most commonly used cylinders and a range of permissible internal pressures for an efficient autofrettaged process is recommended.

• Transactions of Materials Processing
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• v.9 no.3
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• pp.265-273
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• 2000

The conventional and new forging processes of the power steering worm blank are analyzed by the rigid-plastic finite element method. The conventional process contains three stages such as indentation, extrusion and upsetting, which was designed by a forming equipment expert. Process conditions such as reduction in area, semi-die angle and upsetting ratio are considered to prevent internal or geometrical defects. The results of simulation of the conventional forging process are summarized in terms of deformation patterns, load-stroke relationships and die pressures for each forming operation. Based on the simulation results of the current three-stage, the power steering worm blank forging process for improving the conventional process sequence is designed. Die pressures and forming loads of proposed process are within limit value which is proposed by experts and the proposed process is found to be proper for manufacturing the power steering worm blank.

• 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.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.1
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• pp.42-53
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• 2008

The two dimensional PIV (particle image velocimetry) measurement technique is applied to water flow in a narrow cavitation tunnel. The nearly homogeneous and isotropic turbulent flows are generated by the honeycomb installed in the tunnel and visualized with a PIV technique. The velocities in the measurement plane at the tunnel centerline 184cm downward from the honeycomb were measured and calculated by an image correlation technique. The turbulent properties are evaluated and each term in the turbulent kinetic energy equation is calculated for the conditions with different internal pressures. Lowering the internal pressure gives an effect on the turbulent flow due to growing bubbles which are resolved in the water. The turbulent kinetic energy in the measurement plane is decayed much slower than those of other research results carried out with wind tunnels. With decreasing the tunnel internal pressures the turbulent intensities are increased about 1.5 times and the anisotropic tendency is also increased.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.46 no.1
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• pp.1-14
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• 2023

This study is a leading case of empirical analysis of whether, when corporate stakeholders (government, investors, customers, managers, employees) put pressure on companies for ESG management, it affects the introduction and implementation of ESG activities (environmental, social, governance) and affects business performance. As for the research method, a sustainability report was published, and a web survey of Korea Research Inc. was conducted from May 10 to May 20, 2022 targeting ESG management managers of 192 companies, and analyzed through the PLS structural equation model. As a result of the study, it was found that the introduction and execution of ESG is closely influenced by the pressure from the government, investors, managers, and employees, and in particular, the internal pressure of current managers and executives and employees has a great impact on the introduction and implementation of environmental, social, and governance activities. In particular, although external pressure also has some influence, it is practical to suggest that strong internal pressure is necessary for continuous activities and performance. And, methodologically, the main activity indicators of the GRI Reporting Guidelines, which are the most representative ESG management indicators, were developed as a questionnaire, and reliability, validity, and model fit were secured through comparison with indicators of multiple systems and expert reviews. The limitations of this study are that more in-depth analysis by industry or size is possible when ESG management is mature and sufficient samples are secured, and complex ESG pressure factor modeling is possible when more diverse stakeholders are added.