• Journal of the Korean Wood Science and Technology
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• v.48 no.6
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• pp.807-819
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• 2020

The aim of this study was to investigate the anatomical characteristics of Quercus mongolica infested by oak wilt disease. To analysis the anatomical characteristics of the wood specimens infested by the oak wilt, the anatomical structures of an infected wood, a dead wood, and sound wood were observed at 10-year-old intervals from 10 to 50 annual rings using both an optical and a scanning electron microscope. The fiber length was measured in units of 5 annual rings from the pith, and the diameter of the vessel element and the ratio of the vessel including the tyloses were measured for each 10 annual ring. In the cross section, on the infected and dead wood specimens, mycelium was also observed with the tyloses in the vessel. There was no signification difference between the wood specimens in the fiber length and the vessel diameter of the vessel element. The fiber length was not difference after 20-30 annual rings which is a part of juvenile wood. The average of the vessel ratio including tyloses in the infected wood was the highest. Especially, the ratio of tyloses was the highest 40-50 annual rings in the infected wood and the dead wood. Therefore, the large difference between the infested wood by oak wilt and the sound wood was the ratio of tyloses. This result can be used as a basic data to utilize the infested wood.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.5
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• pp.286-291
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• 2014

In this study, novel ultrasonic rotary motor of hexadecagon shape stator was proposed. Stator of the hexadecagon ultrasonic motor was composed of an elastic ring and ceramics. The elastic ring had sixteen sides and sixteen angular points. Eight ceramics were attached on the outer surface of the eight sides of the ring. When rotor of cylindrical shaft was inserted inside of the ring stator, central lines of the sixteen sides of the stator hold the shaft by the slight pressures(frictions). This slight pressure was a preload of the motor and it could be controlled by radius and thickness of the ring. When two sinusoidal voltages which have 90 degree phase difference were applied to each four ceramics, elliptical displacements of inner surface of the ring were obtained. These elliptical displacements of the inner surface rotated the shaft rotor through the frictions. The proposed hexadecagon ultrasonic motor was designed and analyzed by using the finite element method (FEM), depending on materials of the elastic ring. Based on the FEM results, one model of motor which showed maximum displacement at contact points was chosen and fabricated. And characteristics of the motor were compared with simulated results. When the motor was fabricated with these results, EL20ET0.5CT0.5CW2 model showed 115[rpm] speed about input voltage of 60[Vrms] at 65.6[kHz]. And the maximum torque of 6[gfcm] was obtained. From these results, the hexadecagon shaped ultrasonic motor can be used to actuator for optical device which needs detailed position control. Also it can be used to medical and portable device by reducing size and weight.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.4
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• pp.77-86
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• 2008

The reliability of leaded and lead-free solders of BGA type packages on a printed circuit board was investigated by employing the standard drop test and 4-point bending test. Tested solder joints were examined by optical microscopy to identify associated failure mode. Three-dimensional finite element analysis(FEM) with ANSYS Workbench v.11 was carried out to understand the mechanical behavior of solder joints under the influence of bending or drop impact. The results of numerical analysis are in good agreement with those obtained by experiments. Packages in the center of the PCB experienced higher stress than those in the perimeter of the PCB. The solder joints located in the outermost comer of the package suffered from higher stress than those located in center region. In both drop and bending impact tests, the lead-free solder showed better performances than the leaded solders. The numerical analysis results indicated that stress and strain behavior of solder joint were dependent on various effective parameters.

• Korean Journal of Optics and Photonics
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• v.28 no.1
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• pp.28-32
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• 2017

In this research, we designed an LSPR sensor based on a thin-film multilayer comprising $TiO_2$ and $SiO_2$. The thickness of the overall substrate layer of the suggested multilayer LSPR sensor is limited to 100 nm, and the number of repeating $TiO_2$ and $SiO_2$ thin films is 1-4 within a limited thickness. Additionally, a nanowire structure with a gold thin film of 40 nm, height of 40 nm, period of 600 nm, and line width of 300 nm was formed on the multilayer. To design the variable wavelength-type SPR, the angle was fixed at $75^{\circ}$ and the wavelength was changed. We then simulated the system with the finite-element method (FEM) using Maxwell's equations. It was confirmed that the resonance wavelength became shorter as the number of multilayers increased when the refractive index was fixed. We found that the wavelength changes were more sensitive. However, no changes were observed when the number of the multilayers was three or higher.

• Journal of Astronomy and Space Sciences
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• v.29 no.2
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• pp.233-244
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• 2012

The Korea Astronomy and Space Science Institute and the Department of Astronomy at the University of Texas at Austin are developing a near infrared wide-band high resolution spectrograph, immersion grating infrared spectrometer (IGRINS). The compact white-pupil design of the instrument optics uses seven cryogenic mirrors, including three aspherical off-axis collimators and four flat fold mirrors. In this study, we introduce the optomechanical mount designs of three off-axis collimating mirrors and one flat slit-viewer fold mirror. Two of the off-axis collimators are serving as H and K-band pupil transfer mirrors, and are designed as system alignment compensators in combination with the H2RG focal plane array detectors in each channel. For this reason, the mount designs include tip-tilt and parallel translation adjustment mechanisms to properly perform the precision alignment function. This means that the off-axis mirrors' optomechanical mount designs are among the most sensitive tasks in all IGRINS system hardware. The other flat fold mirror is designed within its very limitedly allowed work space. This slit-viewer fold mirror is mounted with its own version of the six-point kinematic optics mount. The design work consists of a computer-aided 3D modeling and finite element analysis (FEA) technique to optimize the structural stability and the thermal behavior of the mount models. From the structural and thermal FEA studies, we conclude that the four IGRINS mirror mounts are well designed to meet all optical stability tolerances and system thermal requirements.

• Journal of Digital Contents Society
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• v.10 no.2
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• pp.199-207
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• 2009

The Q-switching the shutter or the different optical science element puts in within the laser light resonator and the storehouse departs from the within the resonator it loses the mortar and the reversal distribution which when is sufficient creates from within the active medium, opens the shutter instantaneously and it is to do to be made to emit with the light where the energy which is accumulated within the resonator is strong very. Like this Q-switching of laser resonator--It decreases factor increasing suddenly to make. To method of Laser Q-switching mechanical switching methods, electro-optic switching methods and switching by saturable absorber methods, acousto-optic switching method etc. 4 kind are being used on a large scale. In these people the conversion which is electric in compliance with the effect which is electrooptics is widely being used the Q-switching pulse of short pulse width because being it will be able to create. Consequently, Pockel cell where it has the quality of electrooptics effect) the Q-it is become known that it is suitable it uses with switch. From the research which it sees FET and one-chip microprocessor where it is a switching element and pulse transfomer to plan and produce pockel cell Q-switch driving gears, pulse style Nd: It applied in YAG Laser system and it investigated and researched the operating characteristic of the Q-switch. Also, the Q-switch leads and Nd where it is output: YAG with forecast in compliance with a theoretical calculation it comes to buy laser beam side politics it compared and laser beam qualities which had become Q-switching it analyzed.

• The Journal of the Acoustical Society of Korea
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• v.42 no.5
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• pp.441-451
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• 2023

Ultrasound transducers are an essential component of combined photoacoustic and ultrasound imaging systems and play an important role in image evaluation. However, ultrasound transducers are opaque; therefore, light must bypass the ultrasound transducer to reach the target point to produce a photoacoustic image. Providing different paths for the optical and acoustic signals results in a complicated system design, increasing the system volume. To overcome these problems, an optically Transparent Ultrasound Transducer (TUT) was developed. Unlike conventional opaque ultrasound transducers, optically TUT can be fabricated by a variety of manufacturing methods and they are suitable for use with specific piezoelectric elements and serve various purposes. In this study, a comparative analysis of the results of using Lithium Niobate (LNO), Lead Magnesium Niobate-Lead Titanate (PMN-PT), and Polyvinylidene Difluoride (PVDF), which are materials used in piezoelectric element-based TUT. LNO is a piezoelectric element widely used in TUT, and PMN-PT has been actively studied recently with a higher transmission and reception rate than LNO. Existing TUT have lower ultrasound resolution than photoacoustic resolution, but they have recently been manufacturing focused TUT with high ultrasound resolution using PVDF. A comparative analysis of the production results of these TUT was performed.

• The Journal of the Convergence on Culture Technology
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• v.8 no.3
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• pp.313-321
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• 2022

As 5G is getting developed, people are getting interested in immersive content. Some predicts that immersive content may be implemented in real life such as holograms, which were only possible in movies. Holograms, which has been studied for a long time since Dennis Gabor published the basic theory in 1948, are constantly developing in a new direction with digital technology. It is developing from a traditional optical hologram, which is produced by recording the interference pattern of light to a computer generated hologram (CGH) and a digital hologram printer. In order to produce a hologram using a digital hologram printer, holographic element (Hogel) image must first be created using multi-view images. There are a method of directly photographing an actual image and a method of modeling an object using 3D graphic production tool and rendering the motion of a virtual camera to acquire a series of multi-view images. In this paper, we propose a new method of getting image, which is one of the visual effect, VFX, producing multi-view images using chroma key composition. We shoot on the green screen of actual object, suggest the overall workflow of composition with 3D computer graphic(CG) and explain the role of each step. We expected that it will be helpful in researching a new method of image acquisition in the future if all or part of the proposed workflow to be applied.

• Journal of the Korean Society for Heat Treatment
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• v.11 no.2
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• pp.140-149
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• 1998

The graphitization is affected by the addition of small amount of the elements, such as Si, Al, Ni, B, Cr and Mn etc. Boron is well known as the most effective element for the graphitization of cementite in high carbon steels. But a study on quantitative analysis of B effect on the graphitization is few reported. Therefore the effect of boron addition in Fe-0.65%C-1.0%Si-0.5%Mn steels on the graphitization is investigated quantitatively using hardness tester, optical microscope and scanning electron microscope, neutron induced microscopic radiography. The graphitization in high carbon steels is promoted with 0.003~0.005%B addition. But the graphitization in steels which has no boron takes long holding time at $680{\sim}720^{\circ}C$. The hardness of quenched steel containing 0.003%B is higher than that of 0.005%B added steel due to complete dissolution of fine graphites into the austenite. The 0.003%B added high carbon steel graphitized at $680^{\circ}C$ for 25hr is useful steel for the agricultural implements and automobile parts which needed a good formability and high hardness.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.4
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• pp.495-501
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• 2014

Piezoresistive-type, capacitive-type, and optical-type sensors have mainly been used for measuring a strain. However, in building a sensor network for remote monitoring using these conventional sensors there are disadvantages such as the complexity of a measuring system including wireless communication circuitry and high cost. In this paper, we demonstrates a highly-sensitive surface acoustic wave (SAW) strain sensor which is advantageous to harsh environments and wireless network. We designed and fabricated the SAW strain sensor. The SAW strain sensor attached on a specimen was tested with a tensile tester. The strain on the sensor surface was measured with a commercial strain gauge and compared with that obtained from strain analysis. The central frequency shift of the SAW sensor was measured with a network analyzer. The sensitivity of the SAW strain sensor is 134 $Hz/{\mu}{\varepsilon}$ which is high compared to previous results.