• Journal of the Korea Convergence Society
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• v.10 no.10
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• pp.123-128
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• 2019

The structural analysis for light weight on the brake pedal of the racing spec installed with the balance bars of the four models were performed in this study. By utilizing two materials of steels and aluminum alloys, four shapes were analyzed. It is generally assumed that the magnitude of force a person may incur when riding in a car is 1000 N. The fixed points are designated as the parts at which the bolts and pedals are fixed and the mounting part of the balance bar applied by the stress transmitted through the rod when the pressure of the master cylinder rises and the operation stops. Through this analysis study, it is thought that the vulnerability of each brake pedal model can be investigated and the transmission efficiency of the brake pedal can be increased by light weight. As the design data with the durability of brake pedal obtained on the basis of this study result are utilized, the esthetic sense can be shown by being grafted onto the part of car at real life.

• Computers and Concrete
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• v.27 no.3
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• pp.199-210
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• 2021

The aim of this paper was to examine the continuous and discontinuous contact problems between the functionally graded (FG) layer pressed with a uniformly distributed load and homogeneous half plane using an analytical method and FEM. The FG layer is made of non-homogeneous material with an isotropic stress-strain law with exponentially varying properties. It is assumed that the contact at the FG layer-half plane interface is frictionless, and only the normal tractions can be transmitted along the contacted regions. The body force of the FG layer is considered in the study. The FG layer was positioned on the homogeneous half plane without any bonds. Thus, if the external load was smaller than a certain critical value, the contact between the FG layer and half plane would be continuous. However, when the external load exceeded the critical value, there was a separation between the FG layer and half plane on the finite region, as discontinuous contact. Therefore, there have been some steps taken in this study. Firstly, an analytical solution for continuous and discontinuous contact cases of the problem has been realized using the theory of elasticity and Fourier integral transform techniques. Then, the problem modeled and two-dimensional analysis was carried out by using ANSYS package program based on FEM. Numerical results for initial separation distance and contact stress distributions between the FG layer and homogeneous half plane for continuous contact case; the start and end points of separation and contact stress distributions between the FG layer and homogeneous half plane for discontinuous contact case were provided for various dimensionless quantities including material inhomogeneity, distributed load width, the shear module ratio and load factor for both methods. The results obtained using FEM were compared with the results found using analytical formulation. It was found that the results obtained from analytical formulation were in perfect agreement with the FEM study.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.12
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• pp.1874-1881
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• 2021

Black ice, which occurs mainly on the road, vehicle traffic bridges and tunnel entrances due to the sub-zero temperature due to the slip of the road due to heavy snow, is not recognized because the image of asphalt is transmitted in the driver's view, so the vehicle loses braking power because it causes serious loss of life and property. In this paper, we propose a method to identify the black ice by using infrared camera and to identify the road condition by using deep learning to compensate for the disadvantages of existing black ice detection methods (artificial satellite imaging, checking the pattern of slip by ultrasonic reception, measuring the temperature of the road surface, and checking the difference in friction force of the tire during vehicle driving) and to reduce the size of the sensor to detect black ice.

• Design & Manufacturing
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• v.17 no.1
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• pp.56-63
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• 2023

In this study, the vibration signal of the mold was measured and analyzed to monitor the process information and characteristics during the press molding process. A necklace-type picture frame mold was used for press molding, and the vibration signal was measured by GY-61 acceleration sensor module attached to the surface of the upper (movable) mold base. The change of the vibration signal of the mold according to press speed was analyzed. As a result, the vibration signal had a large change at five sections: "Holder contact", "Punch contact and start of pressing", "End of pressing", "Mold open", and "Demolding". The time difference between "Punch contact and start of pressing" and "End of pressing" means the pressing time which is the actual time the material is molded under pressing pressure. The time intervals for each section, represented by the time interval between "Holder contact" and "Punch contact and start of pressing", can be used to compare and evaluate the press speed applied to the process. By comparing the vibration signals at 60 rpm and 90 rpm, the amplitude at the section of "Punch contact and start of pressing" increased as the press speed increased. This result means that as the press speed increases, more force and pressure is applied to the material. Also, the peak values of the other sections were found to increase as the press speed increased. It was found that the pressing time, the time interval between "Punch contact and start of pressing" and "End of pressing", decreases as the pressing speed increases. Similarly, press speed factor, the time interval between "Holder contact", and "Punch contact and start of pressing", is found to be shorter. Therefore, based on the result of this study, the pressing time, press speed, pressing(punching) pressure of each cycle can be monitored by measuring the vibration signal of the mold. Also, it was confirmed that the level and trend of process information and characterization can be evaluated as the change of the mold vibration during press molding.

• Journal of the Korean Wood Science and Technology
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• v.51 no.3
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• pp.197-206
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• 2023

A truss is a structure in which the members are connected and arranged such that they are primarily subjected to axial loading. A truss has the advantage that it can be used for a longer span because the structure distributes the applied force to its members well, and the load is transmitted only in the axial direction of the members. Trusses manufactured using timber have more advantages than those made of other materials. In this study, the properties of parallel chord trusses composed of timber chord and steel-web members were evaluated. We constructed truss specimens with various lengths by using upper and lower chords of 2 × 4 inch spruce-pine-fir lumber and steel-web members manufactured by S and P companies. The specimens were tested in accordance with KS F 2150. The test results showed that the load at the deflection limit and the deflection limit itself increased from L/180 to L/360 regardless of the length of the specimens. For specimens of the same length, the load at the deflection limit increased as the height of the parallel timber chord truss specimens increased from 200 to 300 mm. Successive installations of the steel-web members (SST) showed almost 2 times the load at each deflection limit compared to that of SAT specimens (alternate installation of the steel-web members). When comparing the three load-deflection limits in terms of the manufacturer of the steel-web members, the load at each deflection limit for SST specimens was higher than that for PST specimens.

• Current Optics and Photonics
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• v.7 no.6
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• pp.721-731
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• 2023

This paper studies various roughness parameters, besides waviness, texture, and nonlinear parameters of Bismarck brown Y (BBY)-doped Poly(methyl methacrylate) (PMMA) films based on the computed values of optical limiting (OL) threshold power and nonlinear refractive index. The films' morphology, grain size, and absorption spectra were investigated using atomic force microscopy in conjunction with ultraviolet-visible (UV-Vis) spectrophotometer. The particle size of the films ranged between 4.11-4.51 mm and polymer films showed good homogeneity and medium roughness, ranging from 1.11-4.58 mm. A polymer film's third-order nonlinear optical features were carried out using the Z-scan methodology. The measurements were obtained by a continuous wave produced from a solid-state laser with a 532 nm wavelength. According to the results, BBY has a nonlinear refractive index of 10^-6 cm²/W that is significantly negative and nonlinear. The optical limiting thresholds are roughly 10.29, 13.52, and 18.71 mW, respectively. The shift of nonlinear optical features with the film's concentration was found throughout the experiment Additionally, we found that the polymer samples have outstanding capabilities for restricting the amount of optical power that may be transmitted through them. We propose that these films have the potential to be used in a wide variety of optoelectronic applications, including optical photodetectors and optical switching.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.12
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• pp.8187-8194
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• 2015

To accelerate a heavy roller coaster train with over 1G force, a lot of thrust is required and linear synchronous motor(LSM) as propulsion method is suitable for this kind of system. To increase the propulsion efficiency of LSM, precise and real-time position information of vehicle is required for accurate phase control. However, the discontinuous position information with relatively long time interval is usually transmitted from the hall-sensors on the track every magnet length. In this paper, the basic motor model based on traditional dq-axis equations is described and the motor dynamic model is produced by considering the cogging force and friction loss. To improve the position accuracy, the position estimator is also proposed for LSM control system. Simulations were performed to check the characteristics of the torque control system which includes the position estimator based on the motor model. Simulation results based on the linearized model show that this control system has an enough bandwidth and phase margin and the executed algorithm achieves an ideal effect to follow the real-time position signal. Therefore, the feasibility of position estimator is also confirmed.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.176-177
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• 2013

Surface plasmon polaritons (SPPs) have attracted the attention of scientists and engineers involved in a wide area of research, microscopy, diagnostics and sensing. SPPs are waves that propagate along the surface of a conductor, usually metals. These are essentially light waves that are trapped on the surface because of their interaction with the free electrons of conductor. In this interaction, the free electrons respond collectively by oscillating in resonance with the light wave. The resonant interaction between the surface charge oscillation and the electromagnetic field of the light constitutes the SPPs and gives rise to its unique properties. In this papers, we studied theoretical and experimental extraordinary transmittance (T) and reflectance (R) of 2 dimensional metal hole array (2D-MHA) on GaAs in consideration of the diffraction orders. The 2d-MHAs was fabricated using ultra-violet photolithography, electron-beam evaporation and standard lift-off process with pitches ranging from 1.8 to $3.2{\mu}m$ and diameter of half of pitch, and was deposited 5-nm thick layer of titanium (Ti) as an adhesion layer and 50-nm thick layer of gold (Au) on the semiinsulating GaAs substrate. We employed both the commercial software (CST Microwave Studio: Computer Simulation Technology GmbH, Darmstadt, Germany) based on a finite integration technique (FIT) and a rigorous coupled wave analysis (RCWA) to calculate transmittance and reflectance. The transmittance was measured at a normal incident, and the reflectance was measured at variable incident angle of range between $30^{\circ}{\sim}80^{\circ}$ with a Nicolet Fourier transmission infrared (FTIR) spectrometer with a KBr beam splitter and a MCT detector. For MHAs of pitch (P), the peaks ${\lambda}$ max in the normal incidence transmittance spectra can be indentified approximately from SP dispersion relation, that is frequency-dependent SP wave vector (ksp). Shown in Fig. 1 is the transmission of P=2.2 um sample at normal incidence. We attribute the observation to be a result of FTIR system may be able to collect the transmitted light with higher diffraction order than 0th order. This is confirmed by calculations: for the MHAs, diffraction efficiency in (0, 0) diffracted orders is lower than in the (${\pm}x$, ${\pm}y$) diffracted orders. To further investigate the result, we calculated the angular dependent transmission of P=2.2 um sample (Fig. 2). The incident angle varies from 30o to 70o with a 10o increment. We also found the splitting character on reflectance measurement. The splitting effect is considered a results of SPPs assisted diffraction process by oblique incidence.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.5
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• pp.315-323
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• 2015

Damage level of coastal structures has been scaled up according to increase of wave height and duration of the storm due to the abnormal global climate change. So, the design criteria for new breakwaters is being intensified and structural strengthening is also conducted for the existing breakwaters. Recently, interlocking concept has been much attention to enhance the structural stability of the conventional caisson structure designed individually to resist waves. The interlocking caisson breakwater may be survival even if unusual high wave occurs because the maximum wave force may be reduced by phase lags among the wave forces acting on each caisson. In this study, the dispersion characteristics of wave forces using interlocking system that connect the upper part of caisson with cable in the normal direction of breakwater was investigated. A simplified linear model was developed for computational efficiency, in which the foundation and connection cables were modelled as linear springs, and caisson structures were assumed to be rigid. From numerical experiments, it can be found that the higher wave forces are transmitted through the cable as the angle of incident wave is larger, and the larger the stiffness of the interlocking cable makes larger wave dispersion effect.

• Applied Microscopy
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• v.2 no.1
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• pp.39-46
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• 1972

There are many kinds of microscopes suitable for general studies; optical microscopes(OM), conventional transmission electron microscopes (TEM), and scanning electron microscopes(SEM). The optical microscopes and the conventional transmission electron microscopes are very familiar. The images of these microscopes are directly formed on an image plane with one or more image forming lenses. On the other hand, the image of the scanning electron microscope is formed on a fluorescent screen of a cathode ray tube using a scanning system similar to television technique. In this paper, the features and some applications of the scanning electron microscope will be discussed briefly. The recently available scanning electron microscope, combining a resolution of about $200{\AA}$ with great depth of field, is favorable when compared to the replica technique. It avoids the problem of specimen damage and the introduction of artifacts. In addition, it permits the examination of many samples that can not be replicated, and provides a broader range of information. The scanning electron microscope has found application in diverse fields of study including biology, chemistry, materials science, semiconductor technology, and many others. In scanning electron microscopy, the secondary electron method. the backscattererd electron method, and the electromotive force method are most widely used, and the transmitted electron method will become more useful. Change-over of magnification can be easily done by controlling the scanning width of the electron probe. It is possible. to continuously vary the magnification over the range from 100 times to 1.00,000 times without readjustment of focusing. Conclusion: With the development of a scanning. electron microscope, it is now possible to observe almost all-information produced through interactions between substances and electrons in the form of image. When the probe is properly focused on the specimen, changing magnification of specimen orientation does not require any change in focus. This is quite different from the conventional transmission electron microscope. It is worthwhile to note that the typical probe currents of $10^{-10}$ to $10^{-12}\;{\AA}$ are for below the $10^{-5}$ to $10^{-7}\;{\AA}$ of a conventional. transmission microscope. This reduces specimen contamination and specimen damage due to heatings. Outstanding features of the scanning electron microscope include the 'stereoscopic observation of a bulky or fiber specimen in high resolution' and 'observation of potential distribution and electromotive force in semiconductor devices'.