• Korean Journal of Optics and Photonics
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• v.11 no.2
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• pp.119-122
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• 2000

We proposed a novel mode shape converter (MSC) that can effectively reduce the coupling loss between polymer rib waveguide and single mode fiber. The double-nb geometry that was used in the novel MSC converted an elliptical mode to circular mode and an circular mode to elliptical mode. This structure can be easily realized by using the typical fabrication process for polymer wavegUide. Simulation using a three dimensional beam propagation method showed that the novel MSC has a coupling loss of 0.079 dB/facet and total lllsertioll loss of less than 0.2 dB. .2 dB.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.9
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• pp.97-104
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• 1999

Brake squeal noise has been a problem since the early days of motoring . It is important to obtain vibration mode shape for reduction of brake noise . Stroboscopic Electronic Speckle Pattern Interferometry is a very powerful measuring method for study of vibrating objects in static state compared with conventional methods because this method can give both resonance frequency and quantitative visualization of vibration mode shape at the same time. In this paper, we performed qualitative visualization and quantitative analysis of vibration mode shpae of disk brake by using stroboscopic ESPI and phase shifting method. The stroboscopic wavefronts are obtained by chopping continuous wave laser beam using acousto-optic modulator .Experiments were performed at the same constraint conditions as disk brake of the practical vehicle as far as possible. The experimental results of this paper show quantitative measurement of vibration mode shape and quantiative visualization of vibration amplitude of disk brake with 3D plotting.

• The KSFM Journal of Fluid Machinery
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• v.18 no.1
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• pp.20-28
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• 2015

The pump-turbine impeller is the key component of pumped storage power plant. Current design methods of pump-turbine impeller are private and protected from public viewing. Generally, the design proceeds in two steps: the initial hydraulic design and optimization design to achieve a balanced performance between pump mode and turbine mode. In this study, the 3D inverse design method is used for the initial hydraulic impeller design. However, due to the special demand of high performance in both pump and reverse mode, the design method is insufficient. This study is carried out by modifying the geometrical parameters of the blade which have great influence and need special consideration in obtaining the high performance on the both modes, such as blade shape type at low pressure side (inlet of pump mode, outlet of turbine mode) and the blade lean at blade high pressure side (outlet of pump mode, inlet of turbine mode). The influence of the geometrical parameters on the performance characteristic is evaluated by CFD analysis which presents the efficiency and internal flow results. After these investigations of the geometrical parameters, the criteria of designing pump-turbine impeller blade low and high sides shape is achieved.

• Steel and Composite Structures
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• v.25 no.3
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• pp.347-360
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• 2017

The goal of this study is to fill this apparent gap in the area about vibration analysis of multiwalled carbon nanotubes (MWCNTs) curved panels by providing 3-D vibration analysis results for functionally graded multiwalled carbon nanotubes (FG-MWCNTs) sandwich structure with power-law distribution of nanotube. The effective material properties of the FG-MWCNT structures are estimated using a modified Halpin-Tsai equation. Modified Halpin-Tsai equation was used to evaluate the Young's modulus of MWCNT/epoxy composite samples by the incorporation of an orientation as well as an exponential shape factor in the equation. The exponential shape factor modifies the Halpin-Tsai equation from expressing a straight line to a nonlinear one in the MWCNTs wt% range considered. Also, the mass density and Poisson's ratio of the MWCNT/phenolic composite are considered based on the rule of mixtures. Parametric studies are carried out to highlight the influence of MWCNT volume fraction in the thickness, different types of CNT distribution, boundary conditions and geometrical parameters on vibrational behavior of FG-MWCNT thick curved panels. Because of using two-dimensional generalized differential quadrature method, the present approach makes possible vibration analysis of cylindrical panels with two opposite axial edges simply supported and arbitrary boundary conditions including Free, Simply supported and Clamped at the curved edges. For an overall comprehension on 3-D vibration analysis of sandwich panel, some mode shape contour plots are reported in this research work.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.1
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• pp.201-210
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• 1994

A theoretical heat-flow model incorporating with a constant moving CO$_{2}$ laser beam has been analyzed to predict depth and the shape of bead section during last beam welding. The laser beam is exponentially attenuated with an abosrption coefficient in the material. The solution can be expressed in terms of normalized variables. The experimental data were generated by usint CW 2 CO$_{2}$ laser with multi beam mode and CW 3 kW CO$_{2}$laser with Gaussian mode. The specimens were made as bead-on-plate welds for SM 10C, STS 304, STS 316, STS 420 and pure Nickel. The maximum possible penetration depth and the shape of beas section for given sources of laser power, travel speed and beam spot size can be prdicted with this model in a given material.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.12
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• pp.1337-1342
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• 2012

In this paper, we propose a novel reconfigurable antenna that can change the electrical shape of the matching network using RF switches of PIN diodes. The designed antenna operates at two different modes that are Mode 1 (HSDPA band, 2.1~2.2 GHz) and Mode 2(WiBro WiFi band, 2.3~2.5 GHz). The antenna is built on both sides of a polyarcylate substrate. The measured reflection coefficient shows a matching bandwidth of 547 MHz($S_{11}$ <-3 dB, 2.035~2.582 GHz) for Mode 1 and 600 MHz($S_{11}$ <-3 dB, 2.2~2.8 GHz) for Mode 2, and it shows average vertical gains of -4.4 dBi and -4.5 dBi in x-y plane, respectively.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.3
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• pp.96-102
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• 2007

An Optimal shape design of the boom system in high ladder vehicles is performed using 3-D finite element method (FEM). Results of structural analyses providing displacements, stresses are implemented for the optimum shape design. Lanzcos algorithm is used for the modal analysis in order to find natural frequencies. The optimal shape including cross sectional thickness and length of the boom system is controlled by the subproblem method besed on displacement and Von Mises stress. It is found that a plenty of materials can be saved by using shape design optimization in high ladder vehicles. It is also found that the natural frequency is increased until 6th mode and maintained similarly or decreased after 6th mode.

• Coupled systems mechanics
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• v.9 no.4
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• pp.311-323
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• 2020

This paper deals with the effect of the mode shapes on the dynamic response of a multi-storey frame subjected to moving train loads which are modelled as loads of constant intervals with constant velocity using the finite element method. The multi-storey frame is modelled as a number of Bernoulli-Euler beam elements. First, the first few modes of the multi-storey frame are determined. Then, the effects of force span length to beam length ratio and velocity on dynamic magnification factor (DMF) are evaluated via 3D velocity-force span length to beam length ratio-DMF graphics and its 2D projections. By using 3D and 2D graphics, the directions of critical speeds that force the structure under resonance conditions are determined. Last, the mode shapes related to these directions are determined by the time history and frequency response graphs. This study has been limited by the vibration of the frame in the vertical direction.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.2
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• pp.128-133
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• 2015

This paper describes the construction of a static 3D ultrasonography image by tracking the radiation beam position during the handy operation of a 1D array probe to enable point-of-care use. The theoretical model of the transformation from the translational and rotational information of the sensor mounted on the probe to the reference Cartesian coordinate system was given. The signal amplification and serial communication interface module was made using a commercially available sensor. A test phantom was also made using silicone putty in a donut shape. During the movement of the hand-held probe, B-mode movie and sensor signals were recorded. B-mode images were periodically selected from the movie, and the gray levels of the pixels for each image were converted to the gray levels of 3D voxels. 3D and 2D images of arbitrary cross-section of the B-mode type were also constructed from the voxel data, and agreed well with the shape of the test phantom.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.220-223
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• 2000

In this study for the development of a 3D pattern mill, we designed its layout which has high stiffness and low-weight structure. We calculated the load of each axis component when 3D pattern mill is under the worst cutting conditions. On base of the calculations, we determined the size of its structure and selected main components of the machine. Also, using FEM we analyzed the layout design of 3D pattern mill to reduce the wcight of structure and increase stiffness of it. According to the load position and direction, shapes and values of the deformation and the stress distributions are calculated, also we calculated the natural frequencies and mode shapes in order ta modify and redesign the weak parts