• Polymer(Korea)
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• 제26권6호
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• pp.718-727
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• 2002

In this work, an Ar+ beam was irradiated on carbon fiber surfaces to improve the interfacial shear strength (IFSS) of the resulting composites using an ion assisted reaction (IAR) method h single fiber pull-out test was executed to investigate the basic characteristics of the single Carbon fiber/matrix interface. Based on Greszczuk's geometrical model, the debonding force for pull-out of the fiber from the resins was discussed with the applied ion beam energy as a result, it was known that an ion beam treatment produced the functional groups on fiber surface and etching lines along the fiber axis direction, resulting in increasing the adhesion forces between fibers and matrix, which caused the improvement of the IFSS in a composite system. And, it was also found that the maximum IFSS was shown at 0.8 keV ion beam energy in this system.

• Journal of Navigation and Port Research
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• 제30권1호
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• pp.105-111
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• 2006

A LMTT (Linear Motor-based Transfer Technology) is a horizontal transfer system for the yard automation This system is based on PMLSM (Permanent Magnetic Linear Synchronous Motor) that consists of stator modules on the rail and shuttle car. In this research, the kriging interpolation method using sequential sampling is utilized to find the optimum design of a mover in LMTT. The design variables are considered as the transverse, longitudinal and wheel beam's thicknesses. The objective function is set up as weight, while the constant functions are set up as the stresses generated by four loading conditions. The optimum results obtained by the suggested method are compared with those determined by the GENESIS.

• Transactions of the Korean Society of Mechanical Engineers A
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• 제36권10호
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• pp.1241-1248
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• 2012

The objective of this study is to evaluate the thermal damage characterization of a silicon wafer subjected to a CW laser beam. The variation in temperature and stress during laser beam irradiation has been predicted using a three-dimensional numerical model. The simulation results indicate that the specimen might crack when a 93-$W/cm^2$ laser beam is irradiated on the silicon wafer, and surface melting can occur when a 186-$W/cm^2$ laser beam is irradiated on the silicon wafer. In experiments, straight cracks in the [110] direction were observed for a laser irradiance exceeding 102 $W/cm^2$. Furthermore, surface melting was observed for a laser irradiance exceeding 140 $W/cm^2$. The irradiance for surface melting is less than that in the simulation results because multiple reflections and absorption of the laser beam might occur on the surface cracks, increasing the absorbance of the laser beam.

• Journal of the Korea Convergence Society
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• 제11권9호
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• pp.169-173
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• 2020

The structural analysis was performed at this study when the axle was loaded by using a total of three automotive support beam models, models A, B and C. Comparing with three models A, B, and C, the equivalent stress is considered to be good for its durability because model C is less than the yield stress of the material. The maximum equivalent stresses happening at models A and B are 1.8 times and 2.5 times higher than the yield stress, respectively, indicating that the material is fractured. So, it does not seem to be efficient as a support beam. Model C can be applied efficiently to the improvement design of axle support beams in terms of durability compared to models A and B. The strength of automotive support beam can be evaluated by applying this research result to the automotive part. And it is seen that this study is adequate at the efficient design and aesthetic convergence practically.

• Nuclear Engineering and Technology
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• 제21권1호
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• pp.40-47
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• 1989

For the effective design of a beam forming structure of the negative-ion-based neutral beam injector, a computer program based on a particle simulation model is developed for the calculation of charged particle motions in the electrostatic fields. The motions of negative ions inside the acceleration tube of a multiple-aperture triode are computed at finite time steps. The electrostatic potentials are obtained from the Poisson's equation by the finite difference method. The successive overrelaxation method is used to solve the matrix equation. The particle and force weighting methods are used on a cloud-in-cell model. The optimum design of the beam forming structure has been studied by using this computer code for the various conditions of elctrodes. The effects of the acceleration-deceleration gap distance, the thickness of the deceleration electrode and the shape of the acceleration electrode on beam trajectories are exmined to find the minimum beam divergence. Some numerical illustrations are presented for the particle movements at finite time steps in the beam forming tubes. It is found in this particle simulation modelling that the shape of the acceleration electrode is the most significant factor of beam divergence.

• Journal of Internet Computing and Services
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• 제23권3호
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• pp.13-20
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• 2022

IEEE 802.11ay Wi-Fi is the next generation wireless technology and operates in mmWave band. It supports the MU-MIMO (Multiple User Multiple Input Multiple Output) transmission in which an AP (Access Point) can transmit multiple data streams simultaneously to multiple STAs (Stations). To this end, the AP should perform MU-MIMO beamforming training with the STAs. For efficient MU-MIMO beamforming training, it is important for the AP to estimate signal strength measured at each STA at which multiple beams are used simultaneously. Therefore, in the paper, we propose a deep learning-based link quality estimation scheme. Our proposed scheme estimates the signal strength with high accuracy by utilizing a deep learning model pre-trained for a certain indoor or outdoor propagation scenario. Specifically, to estimate the signal strength of the multiple concurrent beams, our scheme uses the signal strengths of the respective single beams, which can be obtained without additional signaling overhead, as the input of the deep learning model. For performance evaluation, we utilized a Q-D (Quasi-Deterministic) Channel Realization open source software and extensive channel measurement campaigns were conducted with NIST (National Institute of Standards and Technology) to implement the millimeter wave (mmWave) channel. Our simulation results demonstrate that our proposed scheme outperforms comparison schemes in terms of the accuracy of the signal strength estimation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.832-834
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• 2017

In this paper, the finite element models for composite lattice structures were verified through natural frequency test. Finite element models of composite lattice structure were generated using beam, shell and solid element. Natural frequencies were measured using impact test method under free-boundary condition. The natural frequencies of finite element analysis for shell and solid element showed a good agreement with experimental results. But beam element did not show a good agreement with experimental results, because beam element could not consider the degradation of mechanical properties of non-intersection parts for composite lattice structure.

• The Korean Journal of Nuclear Medicine
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• 제39권1호
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• pp.1-8
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• 2005

This paper is described on the development of KOTRON-13 and recent status of PET cyclotron by commercial cyclotron companies. KIRAMS has developed medical cyclotron which is KIRAMS-13. Samyoung Unitech produces KOTRON-13 with transfered technology by KIRAMS. As a part of Regional Cyclotron Installation Protect, KOTRON-13 cyclotrons and $[18F]FDG$ production modules are being installed at regional cyclotron centers in Korea. The medical concern with radiation technology has been growing for the last several years. Early cancer diagnosis through the cyclotron and PET-CT have been brought to public attention by commercial cyclotron models in the world. The new commercial cyclotron models are introduced compact low energy cyclotrons developed by CTI, GE, Sumitomo in recent. It produces different short-lived radioisotopes, such as $[^{18}F],\;[^{11}C],\;[^{13}N]\;and\;[^{15}O]$. For the better reliability acceleration particle is proton only. The characteristics of new model cyclotrons are changed to lower energy corresponding to less 13 MeV. New models have self-shielding and low power consumption. Design criteria for the different types of commercial cyclotrons are described with reference to hospital demands.

• Journal of the Korean Magnetics Society
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• 제14권2호
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• pp.65-70
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• 2004

Read out signal and temperature distribution of magnetic amplifying magnetooptical disk were studied. Temperature distribution of recording layer and adjacent layers were calculated when the disk was at rest. Mark size, length and location were simulated from a chain of recording beam pulses. In addition, signal amplitude depending on the shape of the marks, readout signals from the recording layer and amplified marks of the readout layer, were simulated. Simplified thermal conduction model was used to calculate the temperature distribution of recording and adjacent layers as a function of time as well as to calculate the mark size, length and location. Readout signal was calculated by the convolution of the disk reflectivity and the Gaussian beam intensity. Readout signal from the mark in the readout layer amplified to the size of the laser beam fumed out to be twice as large as the signal from the crescent shaped mark in the recording layer.

• Journal of Broadcast Engineering
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• 제11권4호
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• pp.521-532
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• 2006

Recently, many research initiatives have been underway to improve reception performance of ATSC based DTV signal in mobile channel by adopting multiple antennas. In this paper, we propose a new mobile channel model which can be applicable to any array geometry. And then we propose new channel estimation algorithm which uses PN5l1 sequence in field synch. The proposed algorithm is to estimate channel by correlating the input signal in If frequency band and finding maximum peak, which does not need complicated synchronization circuit. Finally, we propose new receiver structures which can be implemented at the front-end of the existing receiver with no modification. With computer simulation, we verify the performance of the proposed model and verify the performance of the receiver structure with computer simulation.