• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.6
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• pp.677-684
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• 2003

A new unipolar aerosol charger was developed by using an indirect photoelectric charging. The charger consists of two coaxial tubes, the inner UV lamp wrapped with stainless mesh and the outer Al cylinder. In this study, the effects of flow rate, particle size, and electric field were examined to search the optimal charging conditions with experimental and numerical methods. Monodisperse NaCl particles were fed into an annular space and the particles were charged by negative ions generated from Al plate exposed to the UV light. According to experimental results, the average number of elementary charge on particles increases from 2.5 to 5.5 as particle size increases from 50nm to 130nm at 2.5 L/min and 100V. The average number of elementary charge on particles was maximized at 25V as the electric potential between the stainless mesh and Al plate was varied from 0V to 400V.

• Steel and Composite Structures
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• v.48 no.1
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• pp.1-17
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• 2023

The main goal of this paper is to study vibration of damaged core laminated sectorial plates with Functionally graded (FG) face sheets based on three-dimensional theory of elasticity. The structures are made of a damaged isotropic core and two external face sheets. These skins are strengthened at the nanoscale level by randomly oriented Carbon nanotubes (CNTs) and are reinforced at the microscale stage by oriented straight fibers. These reinforcing phases are included in a polymer matrix and a three-phase approach based on the Eshelby-Mori-Tanaka scheme and on the Halpin-Tsai approach, which is developed to compute the overall mechanical properties of the composite material. Three complicated equations of motion for the sectorial plates under consideration are semi-analytically solved by using 2-D differential quadrature method. Using the 2-D differential quadrature method in the r- and z-directions, allows one to deal with sandwich annular sector plate with arbitrary thickness distribution of material properties and also to implement the effects of different boundary conditions of the structure efficiently and in an exact manner. The fast rate of convergence and accuracy of the method are investigated through the different solved examples. The sandwich annular sector plate is assumed to be simply supported in the radial edges while any arbitrary boundary conditions are applied to the other two circular edges including simply supported, clamped and free. Several parametric analyses are carried out to investigate the mechanical behavior of these multi-layered structures depending on the damage features, through-the-thickness distribution and boundary conditions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.6
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• pp.324-330
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• 2013

The main objective of this work is to experimentally investigate the effect of inlet geometries on the distribution of two-phase annular flow at header-channel junctions simulating the corresponding parts of compact heat exchangers. The cross-section of the header and the channels were fixed to $16mm{\times}16mm$ and $12mm{\times}1.8mm$, respectively. Experiments were performed for the mass flux and the mass quality ranges of $30{\sim}140kg/m^2s$ and 0.3~0.7, respectively. Air and water were used as the test fluids. Three different inlet geometries of the header were tested:no restriction (case A), a single 8 mm hole at the center (case B), and nine 2 mm holes around the center (case C) at the inlet, respectively. The tendencies of the two-phase flow distribution were different, in each case. For cases B and C (flow resistance exists), more uniform flow distribution results were seen, compared with case A(no flow resistance), due to the flow pattern change to mist flow from annular flow at the inlet, and the flow recirculation near the end plate of the header.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.4
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• pp.601-607
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• 2003

The column type is used as the sensing element of the load cell to measure the large force in the range of 10$^4$~ 10$^{7}$ N. However. it is not easy to handle the load with large capacity due to its size. It is, therefore, necessary to design a compact load cell with a low aspect ratio. Thus this paper showed the characteristic evaluation of compact load cell with respect to the shape of supporting plate. The supporting plate of the load cell was an annular type with inner(D$_{i}$) and outer(D$_{o}$) diameters. Using the strain distribution obtained from FEM. the supporting plate was designed to get the stable output voltage of the load cell. The three designed supporting plates were manufactured, and the result of characteristic experiment of the load cell, using the 10 MN hydraulic force standard machine, was compared with FEM.M.M.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.2
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• pp.269-277
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• 2002

Experiments on the evaporation heat transfer and pressure drop in the brazed type plate heat exchangers were performed using refrigerants R410A and R22. To investigate the geometric effect, plate heat exchangers with the same pitch and height but different 45$^{\circ}$, 35$^{\circ}$and 20$^{\circ}$chevron angles are used. Tests were conducted fur the ranges of the mass flux of refrigerant from 13 kg/m$^2$s to 34 kg/m$^2$s, the evaporation temperatures of 15$^{\circ}C$, 1$0^{\circ}C$ and 5$^{\circ}C$, vapor quality from 0.15 to 0.95 and the heat flux from 2.5 kW/m$^2$to 8.5 kW/m$^2$. The evaporation heat transfer coefficients and pressure drops were measured. Most of flow patterns are in the chum flow regime and become close to the annular flow for increasing the mass flux and the vapor quality. The heat transfer coefficient increases with increasing the evaporation temperature at a given mass flux in all plate heat exchangers. Also, the pressure drop increases with increasing the mass flux and the quality and decreasing the evaporation temperature and the chevron angle.

• 한국기계연구소 소보
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• s.18
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• pp.75-85
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• 1988

The distributor for hydraulic pumps or motors, particularly radial piston motors, include rotary member which has equally both surface shape for dynamic balance and two fixed members, located in both side of rotary member, which have equal surface shape for dynamic balance and circular ring which use to retain predetermined clearance between two fixed members. Rotary member must have valve part for flow-distribution and can have hydrostatic bearing for excellently dynamic balance. At least two annular steps located on said pressure plate which use in compensation of bolt expansion.

• Current Optics and Photonics
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• v.2 no.2
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• pp.147-152
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• 2018

We propose a novel bi-focal metallic Fresnel zone plate (MFZP) with shallow depth-of-field (DOF) characteristics. We design the specific annular slit patterns, exploiting the phase-selection-rule method along with the particle swarm optimization algorithm, which we have recently proposed. We numerically investigate the novel characteristics of the bi-focal MFZP in comparison with those of another bi-focal MFZP having equivalent functionality but designed by the conventional multi-zone method. We verify that whilst both bi-focal MFZPs can produce dual focal spots at $15{\mu}m$ and $25{\mu}m$ away from the MFZP plane, the former exhibits characteristics superior to those of the latter from the viewpoint of axial resolution, including the axial side lobe suppression and axial DOF shallowness. We expect the proposed bi-focal MFZP can readily be fabricated with electron-beam evaporation and focused-ion-beam processes and further be exploited for various applications, such as laser micro-machining, optical trapping, biochemical sensing, confocal sensing, etc.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.373-378
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• 2000

Zinc galvanized steel plates(sections) of annular corrugations have been used in buried steel culverts. These structures are referred to by a variety of names such as flexible pipes, buried pipes, soil-steel bridges, corrugated steel culverts, and etc. Buried corrugated steel structures show flexible behaviour under the soil load. compared with concrete box structures. Finite element analysis was performed to suggest the reasonable connecting method between the flexible steel culverts and the rigid concrete box. It was predicted that perfectly constrained connections could induce the excessive stress in steel plates. Therefore elastic bearing connections that allow vertical displacement at the connecting point were applied.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.1
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• pp.22-30
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• 1992

The free vibrations of the outer-clamped spinning annular disk which simulates a wafer cutting machine are investigated. The effects of the initial tension, the centrifugal force and outer-fixture extension caused by spinning on the vibration characteristics of the disk are considered. The modal parameters of the disk are calculated by using Galerkin's method as the rotating speed and initial tension are varied. Laboratory experiments are also performed with a rotating and stationary disk, and, it is found that experimental and simulation results are in good agreement.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.1
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• pp.150-157
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• 2008

Bellows are commonly used in piping systems to absorb expansion and contraction in order to reduce stress. Unlike most piping components, bellows consist of a thin-walled shell of revolution with a corrugated meridian, in order to provide the flexibility needed to absorb mechanical movements. It is a composite shell structure consisting of at least one toroidal shell, an annular plate or conical shell. It is difficult to analyze the behavior of bellows because of its complex geometry. Simplified formulas for variable mechanical behaviors of bellows are provided by a standard called EJMA. An automatic design software for bellows is programming by using VBA(Visual Basic for Application) based on EJMA. Bellows engineers can effectively make a decision for bellows geometries because this software provides graphically design results in its post-processor. Bellows design software is expected to give quite a good guidance to practical design. The characteristics of bellows are also investigated through the automatic design process in bellows design software.