• Current Optics and Photonics
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• 제5권1호
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• pp.8-15
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• 2021

An elliptical zone plate (EZP) array is important in off-axis optical systems because it provides two advantages. First, the residual beam and the main source are not focused in the same direction and second, the light from the observation plane is not reflected back towards the beam source. However, the fill factor of the previous EZP array was about 76% which was a little low. Hence, this EZP array could not collect the maximum amount of illumination light, which affected the overall optical performance of the lens array. In this study, we propose a new EZP array design with a 97.5% fill factor used in off-axis imaging system for enhancement of brightness and contrast. Then, direct laser lithography was used to fabricate the high fill factor EZP array by moving the XY linear stage of the system in a zigzag motion. The imaging properties of the proposed EZP array were experimentally verified at the focal plane and compared with the previous model.

• Advances in nano research
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• 제13권4호
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• pp.369-378
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• 2022

Dynamic study of concrete plates under impact load is presented in this article. The main objective of this work is presenting a mathematical model for the concrete plates under the impact load. The concrete plate is reinforced by carbon nanoparticles which the effective material proprieties are obtained by mixture's rule. Impacts are assumed to occur normally over the top layer of the plate and the interaction between the impactor and the structure is simulated using a new equivalent three-degree-of-freedom (TDOF) spring-mass-damper (SMD) model. The structure is assumed viscoelastic based on Kelvin-Voigt model. Based on the classical plate theory (CPT), energy method and Hamilton's principle, the motion equations are derived. Applying DQM, the dynamic deflection and contact force of the structure are calculated numerically so that the effects of mass, velocity and height of the impactor, volume percent of nanoparticles, structural damping and geometrical parameters of structure are shown on the dynamic deflection and contact force. Results show that considering structural damping leads to lower dynamic deflection and contact force. In addition, increasing the volume percent of nanoparticles yields to decreases in the deflection.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.297-302
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• 2002

This paper investigated the properties of flexural behavior of composite beams (end-Reinforced concrete, center-Steel concrete) according to attaching length of main bars to flange, shear reinforcing length for different types of structure. In the preceding study, structural properties of composite beams were investigated according to shear span to depth ratio, attaching method of main bars and shear reinforcing method. Based on these results, a series of experiments was carried out according to attaching length of main bar ＆ reinforcing length for different types of structure. Consequently, as attaching length of main bar and shear reinforcing length increased, composite beams represented higher strength, ductility index and stress mechanism distributed in connection zone of different types of structure.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제14권10호
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• pp.4713-4718
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• 2013

Nowadays, three-dimensional computer added design(3D CAD) tool are widely and actively used for design of mechanical machine. Because using the tool is more effective to understand design concept and to collaborate with other operation than using two-dimensional design tool. In this study, the 3D CAD tool which is called I-DEAS was applied for three-dimensional modeling of main parts and assembling of modeled parts for identification the entire shape of a injection molding machine. In addition, a study was also performed regarding reduction for the weight of main plates for saving production cost and energy in the machine. A finite element method(FEM) program in I-DEAS tool was used for the improvement study. First, the current main plates were structural analysed and then the plate deformations, weak regions and stress distributions were graped. By the FEM results, the 2nd improved designing of the plates was conducted such as reinforcement or slimming of the plate wall thickness. The 2nd structural FEM was performed for verification of the redesigned plates and then the FEM results were compared with the 1st FEM's result. The weight of the main plates were averagely reduced approximately 3 - 7%. By these results, it was seemed that the improved plates have a useful availability.

• Geomechanics and Engineering
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• 제8권4호
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• pp.615-630
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• 2015

The use of helical anchors has been extensively beyond their traditional use in the electrical power industry in recent years. They are commonly used in more traditional civil engineering infrastructure applications so that the advantages of rapid installation and immediate loading capability. The majority of the research has been directed toward the tensile uplift behaviour of single anchors (only one plate) by far. However, anchors commonly have more than one plate. Moreover, no thorough numerical and experimental analyses have been performed to determine the ultimate pullout loads of multi-plate anchors. The understanding of behavior of these anchors is unsatisfactory and the existing design methods have shown to be largely inappropriate and inadequate for a framework adopted by engineers. So, a better understanding of helical anchor behavior will lead to increased confidence in design, a wider acceptance as a foundation alternative, and more economic and safer designs. The main aim of this research is to use numerical modeling techniques to better understand multi-plate helical anchor foundation behavior in soft clay soils. Experimental and numerical investigations into the uplift capacity of helical anchor in soft clay have been conducted in this study. A total of 6 laboratory tests were carried out using helical anchor plate with a diameter of 0.05 m. The results of physical and computational studies investigating the uplift response of helical anchors in soft clay show that maximum resistances depend on anchor embedment ratio and anchor spacing ratio S/D. Agreement between uplift capacities from laboratory tests and finite element modelling using PLAXIS is excellent for anchors up to embedment ratios of 6.

• Transactions of the Korean Society of Mechanical Engineers A
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• 제25권1호
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• pp.70-80
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• 2001

A cycloid reducer is one of the rotational velocity reduction equipments of machinery. It has advantages of the higher reduction ratio, the higher accuracy, the easier adjustment of transmission ratio and the smaller workspace than other kinds of reducer. A cycloidal plate gear is a main part of the cycloid reducer. Its tooth shape is peculiar because of gearing with the roller gear that has the several rollers on the circular line. And then it can be designed to contact all teeth to rollers. So, the cycloid reducer has the good characteristics in the dynamic properties and the zero-backlash in the contact motion. It can be used in robots, high-precision machines and high capacity machinery. This paper proposes a new approach for the shape design of the cycloidal plate gear and presents a Computer-Aided-Design program developed by the proposed method. The first part of this paper defines the two types of the cycloid reducers and explains their mechanisms. The second part defines the instant velocity centers for each type of the cycloid reducers and calculates the contact angles and the contact points by using te geometric relationships and the kinematical properties of the reducers. The third part generates the full shape of the cycloidal plate gear by the coordinate transformation technique. Finally, this paper presents two examples for the shape design of the cycloidal plate gear in order to prove the theory of the proposed method in this paper and the accuracy of the \"CycloGear Designer\".

• Journal of the Korea Organic Resources Recycling Association
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• 제25권1호
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• pp.5-13
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• 2017

Polypropylene is the main existing material in the domestic market being used for the filter plate because of its moldability, low cost, and commercial availability. Polypropylene filter plate once distorted due to the high-pressure during operation may cause the problem in the continuous operation of the solid-liquid separation module. Thermoplastic Poly Urethane (TPU) can be a high-performance alternative material for the filter plate in the solid-liquid separation module of the dehydration process. Hence, to predict and evaluate the TPU for structural stability in the filter plate through analytical techniques designed and experimental verification is essential. As a result, TPU filter plate had maximum strain of 27.85 MPa at 20 bar pressure condition. This result is less than TPU stress-strain limit, which ensures the structural stability of the TPU material.

• Transactions of the Korean Society of Mechanical Engineers A
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• 제35권10호
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• pp.1273-1279
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• 2011

The variable-swash-plate compressor has recently been adopted as a vehicle compressor to improve fuel efficiency. The rotation torque in the variable-swash-plate compressor and the pressure-affected piston have a great influence on the swash-plate design and deformation. This paper suggests the optimal configuration design by using Chebyshev orthogonal polynomial and optimization techniques. The orthogonal array (OA) and analysis of variance (ANOVA) techniques and response surface optimization, are employed to determine the main effects and their optimal design variables. According to the optimal design, we confirm an effective design variable in swash plate and explain the optimal solution, the usefulness for satisfying the constraints of maximum stress and deformation.

• Carbon letters
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• 제8권4호
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• pp.326-334
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• 2007

In this study, graphite composites were fabricated by warm press molding method to realize commercialization of PEM fuel cells. Graphite composites have been considered as alternative economic materials for bipolar plate of PEM fuel cells. Graphite powder that enables to provide electrical conductivity was selected as the main substance. The graphite powder was mixed with phenolic resin and the mixture was pressed using a warm press method. First of all, the graphite powder was pulverized with a ball mill for the dense packing of composite. As the ball milling time increases, the average size of particles decreases and the size distribution becomes narrow. This allows for improvement of the uniformity of graphite composite. However, the surface electrical resistivity of graphite composite increases as the ball milling time increases. It is due to that graphite particles with amorphous phase are generated on the surface due to the friction and collision of particles during pulverizing. We found that the contact electrical resistivity of graphite particles increases as the particle size decreases. The contact electrical resistivity of graphite powders was reduced due to high molding pressure by warm press molding. This leads to improvement of the mechanical properties of graphite composite. Hydrogen gas impermeability was measured with the graphite composite, showing a possibility of the application for bipolar plate in fuel cell. And, I-V curves of the graphite composite bipolar plate exhibit a similar performance to the graphite bipolar plate.

• Transactions of the Korean Society of Mechanical Engineers A
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• 제37권9호
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• pp.1117-1125
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• 2013

A finite element based approach that can be used to investigate the plane-view shape and crop loss of a material during plate rolling is presented. We employed a three-dimensional finite element model to continuously simulate the shape change of the head and tail of a plate as the number of rolling passes increases. The main feature of the proposed model lies in the fact that the multistage rolling can be simulated without a break because the rolling direction of the material is reversibly controlled as the roll gap sequentially decreases. The material constants required in the finite element analysis were experimentally obtained by hot tensile tests. We also performed a pilot hot plate rolling test to verify the usefulness of the proposed finite element model. Results reveal that the computed plane-view shapes as well as crop losses by the proposed finite element model were in good agreement with the measured ones. The crop losses predicted by the proposed model were within 5% of those measured from the pilot hot plate rolling test.