• Structural Engineering and Mechanics
• /
• v.70 no.2
• /
• pp.153-168
• /
• 2019

In this paper, energy absorption characteristics of circular windowed tubes with different section shapes (circular, ellipse, square, hexagon, polygon and pentagon) are investigated numerically and experimentally. The tube possesses the same material, thickness, height, volume and average cross sectional area which are subjected under axial and oblique quasi-static loading conditions. Numerical model was constructed with FE code ABAQUS/Explicit, the obtained outcome of simulation is in good matching with the experimental data. The energy absorbed, specific energy absorption, crash force efficiency, peak and mean loads along with the collapse modes with their initiation point of simple and windowed tubes were evaluated. The technique for order of preference by similarity ideal solution (TOPSIS) approach was employed for assessing their overall crushing performances. The obtained results confirm that efficacy of crash force indicators have improved by introducing windows and tubes with pentagonal and circular windows achieves the maximum ranking about 0.528 and 0.517, it clearly reveals the above are best window shapes.

• Proceedings of the Korean Magnestics Society Conference
• /
• 2000.09a
• /
• pp.352-362
• /
• 2000

In this study, effects of novel VMn underlayer on magnetic properties of CoCrPt/VMn longitudinal medium was studied and compared with those of CoCrPt/Cr medium. It was found that the VMn film had (200) preferred orientation and the lattice constant was about 0.2967 nm, which is slightly larger than that of the Cr, 0.2888 nm. The grain size of VMn film was 9.3 nm at 30 nm thickness, and this is about 38 % smaller than that of a similarly deposited Cr film. The CoCrPt/VMn films showed higher coercivity in comparison with the CoCrPt/Cr films. The coercivity increase seems to be attributed to the increased Co (11.0) texture, improved lattice matching between Co (11.0) and VMn (200), and lower stacking fault density. Mn must have diffused into the CoCrPt magnetic layer more uniformly rather than preferentially along grain boundaries this reduced Ms at higher substrate temperature

• Journal of information and communication convergence engineering
• /
• v.22 no.1
• /
• pp.80-87
• /
• 2024

The Manchu language holds historical significance, but a complete dataset of Manchu script letters for training optical character recognition machine-learning models is currently unavailable. Therefore, this paper describes the process of creating a robust dataset of extracted Manchu script letters. Rather than performing automatic letter segmentation based on whitespace or the thickness of the central word stem, an image of the Manchu script was manually inspected, and one copy of the desired letter was selected as a region of interest. This selected region of interest was used as a template to match all other occurrences of the same letter within the Manchu script image. Although the dataset in this study contained only 4,000 images of five Manchu script letters, these letters were collected from twenty-eight writing styles. A full dataset of Manchu letters is expected to be obtained through this process. The collected dataset was normalized and trained using a simple convolutional neural network to verify its effectiveness.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.16 no.4
• /
• pp.153-158
• /
• 2016

In this paper, TE(transverse electric) scattering problems by a conductive strip grating between grounded double dielectric layer are analyzed by applying the PMM(point matching method) known as a numerical method of electromagnetic fileld. The boundary conditions are applied to obtain the unknown field coefficients, the scattered electromagnetic fields are expanded in a series of Floquet mode functions, and the conductive boundary condition is applied to analysis of the conductive strip. The numerical results for normalized reflected power are analyzed by according as the width and spacing of conductive strip, the relative permittivity and thickness of the double dielectric layers, and incident angles. The most normalized reflected powers of the sharp variations in minimum values are scattered in direction of the other angles except incident angle. The numerical results for the presented structure of this paper having a grounded double dielectric layer are shown in good agreement compared to those of the existing papers.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.28 no.4
• /
• pp.261-268
• /
• 2017

In this paper, we propose an FSSH(Folded Slot Spherical Helix) magnetic dipole antenna with a form factor easy to build and study its radiation properties. The number of folded arms, the gap between them and the metal thickness are tuned to achieve relatively simple structure to realize whereas maintaining high radiation efficiency at an electrically small size. The proposed design shows wide radiation efficiency bandwidth and it is confirmed by circuit simulation that the non-Foster impedance matching techniques could be utilized for its practical use. The prototype of the proposed antenna is built with the aid of an SLS(Selective Laser Sintering) 3D printing technology. The measured result shows lower Q impedance characteristic due to high resistive loss of the copper tape joints.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.9 no.3
• /
• pp.602-608
• /
• 2005

We have studied to obtain the SAW filter for the Single Phase Unidirectional Transduce. (SPUDT), was formed on the Langasite substrate and was evaporated by Aluminum-Copper alloy and then we performed computer-simulated by simulator. We can fabricate that the block weighted type IDT as an input transducer of the filter and the withdrawal weighted type IDT as an output transducer of the filter from the results of our computer-simulations. Also, we have performed to obtain the properly conditions about impedance matching of the SAW filter for SPUDT. We have employed that the number of pairs of the input and output IDT are 50 pairs and the thickness and the width of reflector are 5000A and $3.6{\mu}m$, respectively. And the width of IDT' fingers is $2.4{\mu}m$, and the space between IDT' finger and reflector is $2.0{\mu}m$. Frequency response of the fabricated SAW filter has the property that the center frequency is about 190MHz and bandwidth at the 3dB is probably 7.7MHz after when we have matched impedance. Also, we could obtain that ripple characteristics is less than 0.4dB and standing wave ratio is probably 1.5 after when we have matched impedance.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.550-551
• /
• 2013

Large-area RF-driven ion source is being developed at Germany for the heating and current drive of ITER plasmas. Negative hydrogen (deuterium) ion sources are major components of neutral beam injection systems in future large-scale fusion experiments such as ITER and DEMO. RF ion sources for the production of positive hydrogen ions have been successfully developed at IPP (Max-Planck- Institute for Plasma Physics, Garching) for ASDEX-U and W7-AS neutral beam injection (NBI) systems. In recent, the first NBI system (NBI-1) has been developed successfully for the KSTAR. The first and second long-pulse ion sources (LPIS-1 and LPIS-2) of NBI-1 system consist of a magnetic bucket plasma generator with multi-pole cusp fields, filament heating structure, and a set of tetrode accelerators with circular apertures. There is a development plan of large-area RF ion source at KAERI to extract the positive ions, which can be used for the second NBI (NBI-2) system of KSTAR, and to extract the negative ions for future fusion devices such as ITER and K-DEMO. The large-area RF ion source consists of a driver region, including a helical antenna (6-turn copper tube with an outer diameter of 6 mm) and a discharge chamber (ceramic and/or quartz tubes with an inner diameter of 200 mm, a height of 150 mm, and a thickness of 8 mm), and an expansion region (magnetic bucket of prototype LPIS in the KAERI). RF power can be transferred up to 10 kW with a fixed frequency of 2 MHz through a matching circuit (auto- and manual-matching apparatus). Argon gas is commonly injected to the initial ignition of RF plasma discharge, and then hydrogen gas instead of argon gas is finally injected for the RF plasma sustainment. The uniformities of plasma density and electron temperature at the lowest area of expansion region (a distance of 300 mm from the driver region) are measured by using two electrostatic probes in the directions of short- and long-dimension of expansion region.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.17 no.2
• /
• pp.83-88
• /
• 2017

In this paper, TE(transverse electric) scattering problems by a conductive strip grating between a double dielectric layer are analyzed by applying the PMM(point matching method) known as a numerical method of electromagnetic fileld. The boundary conditions are applied to obtain the unknown field coefficients, the scattered electromagnetic fields are expanded in a series of Floquet mode functions, and the conductive boundary condition is applied to analysis of the conductive strip. The numerical results for the normalized reflected and transmitted power are analyzed by according as the width and spacing of conductive strip, the relative permittivity and thickness of the double dielectric layers, and incident angles. The most normalized reflected powers of the sharp variations in minimum values are scattered in direction of the other angles except incident angle. The numerical results for the presented structure of this paper are shown in good agreement compared to those of the existing papers.

• Korean Journal of Optics and Photonics
• /
• v.8 no.3
• /
• pp.189-193
• /
• 1997

Aspheric pick-up lenses are increasingly used in consumer products such as computer and multimedia, as their mass production has become possible owing to the injection molding process. However still much work needs to be done for more effective manufacture of aspheric lenses, one area of which is the in-line inspection of produced lenses. In this paper, we present a lateral-shearing interferometer that has specially been designed to have a high immunity to external vibration and atmospheric disturbance. The interferometer comprises four prisms. They are directly attached to each other using an immersion oil so that relative sliding motions between the prisms are allowed. Their relative displacement can readily generate necessary lateral-shearing and phase-shifting to determine the wavefront of the beam collimated by the lens under inspection. A special phase-measuring algorithm of arbitrary-bucket is adopted to compensate the phase-shifting error caused by the thickness reduction in the immersion oil. Zernike polynomial fitting has done for determinating quantitative aberration of aspheric pick-up lenses. The interferometer built in this work is robust to external mechanical vibration and atmospheric disturbance so that experimental results show that it has a repeatability of less than λ/100.

• Resources Recycling
• /
• v.9 no.6
• /
• pp.31-35
• /
• 2000

The complex permeability, the complex permittivity and the reflection loss are investigated in the composite microwave absorbers which are mixed with the wasted Mn-Zn ferrite and the industrial cement. The cement has larger the complex permittivity than that of the rubber. The complex permittivity is decreasing with the increment of the mixing ratio of Mn-Zn ferrite to cement (F/C in weight) and the complex permeability is increasing with the increment of F/C. The maximum reflection loss is above -40 dB at all samples. The matching frequency is in the range of 1.3 GHz to 2.9 GHz and is decreasing with the increment of F/C from 1 to 3. The matching thickness is increasing with the increment of F/C. The wasted Mn-Zn ferrite and the cement is very useful material for the composite microwave absorber.