• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2005.09a
• /
• pp.29-34
• /
• 2005

A optical head unit for nano optical probe away was developed. The optical probe array is generated by Talbot effect. The shape and thickness of microlens array(MLA) were designed to minimize the spot size at the foci of MLA. To increase the optical efficiency of the system and obtain the large tolerance for fabrication, aperture size was theoretically optimized. Then microlens illuminated aperture array(MLIAA) as an optical head unit was fabricated using a ultra violet(UV) molding process on aluminum aperture array. In this process, Al aperture array was fabricated separately using the photolithography and reactive ion etching(RIE) process. Optical properties of the generated optical probes were measured and compared at Talbot distance from the aperture array having a diameter of $1{\mu}m$ and MLIAA.

• Journal of Ocean Engineering and Technology
• /
• v.24 no.6
• /
• pp.61-70
• /
• 2010

This study presents free vibration analyses of perforates steel plates with various cutouts. Four different parameters (shape, size, curvature radius ratio, and rotation of cutouts) were considered to investigate the effects of those parameters on the free vibration characteristics, such as natural frequencies of the perforated steel plates. Three different shapes of cutouts are circle, square, and triangle, and the considered sizes are 5, 10, 15, 20, and 25 mm. For the triangular and square cutouts, the characteristic radii of the inscribed circles of those cutouts were defined. In addition, the curvature radius ratio was defined as the ratio of curvature radius of bluntness and the characteristic radius. Then, total seven different curvature radius ratios (0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1) were considered. To investigate the rotation effect of the cutouts, it was considered four rotations ($0^{\circ}$, $15^{\circ}$, $30^{\circ}$, and $45^{\circ}$) for the square cutouts and three rotations (0, 15, and 30) for the triangular cutouts. All the free vibration analyses were conducted using a general purpose finite element program. From the analyses we found that the most influential parameter for the free vibration response of the perforated plates is the size of cutout. The other factors such as the shape, curvature radius ratio, and rotation are minors; they mainly change the natural frequency as long as the size effect is accompanied.

• Journal of Magnetics
• /
• v.15 no.4
• /
• pp.179-184
• /
• 2010

We have investigated the effects of post annealing on iron oxide nanoparticles synthesized by the novel hydrothermal synthesis method with the $FeSO_4{\cdot}7H_2O$. To investigate the post annealing effect, the as-synthesized iron oxide nanoparticles were annealed at different temperatures in a vacuum chamber. The morphological, structural and magnetic properties of the iron oxide nanoparticles were investigated with high resolution X-ray powder diffraction (XRD), high resolution transmission electron microscopy (HRTEM), Mossbauer spectroscopy, and vibrating sample magnetometer analysis. According to the XRD and HRTEM analysis results, as-synthesized iron oxide nanoparticles were only magnetite ($Fe_3O_4$) phase with face-centered cubic structure but post annealed iron oxide nanoparticles at $700^{\circ}C$ were mainly magnetite phase with trivial maghemite ($\gamma-Fe_2O_3$) phase which was induced in the post annealing treatment. The crystallinity of the iron oxide nanoparticles is enhanced by the post annealing treatment. The particle size of the as-synthesized iron oxide nanoparticles was about 5 nm and the particle shape was almost spherical. But the particle size of the post annealed iron oxide nanoparticles at $700^{\circ}C$ was around 25 nm and the particle shape was spherical and irregular. The as-synthesized iron oxide nanoparticles showed superparamagnetic behavior, but post annealed iron oxide nanoparticles at $700^{\circ}C$ did not show superparamagnetic behavior due to the increase of particle size by post annealing treatment. The saturation of magnetization of the as-synthesized nanoparticles, post annealed nanoparticles at $500^{\circ}C$, and post annealed nanoparticles at $700^{\circ}C$ was found to be 3.7 emu/g, 6.1 emu/g, and 7.5 emu/g, respectively. The much smaller saturation magnetization value than one of bulk magnetite can be attributed to spin disorder and/or spin canting, spin pinning at the nanoparticle surface.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.43 no.1
• /
• pp.51-64
• /
• 2019

This study provides basic information for the convenient size selection of shirts in the online purchasing environment. The preferred shirt fit was compared according to body size group. The subjects were 111 students majoring in clothing. After setting a virtual model with her own body sizes, subjects chose the best preferred fit among four sizes shirts which included the shirt suitable to her bust circumference, one size smaller shirt, one size larger shirt, and a two size larger shirt. They generally preferred the original size, but the preferred shirt fit was different by the body characteristics such as stature, waist height, or the ratio of Biacromion and drop. Shirt length was affected by stature and sleeve length was affected by waist height. The shoulder ease was mostly affected by the ratio of the shoulder length. Waist fit and hip fit were influenced by waist and hip. Therefore, the body parts affecting the preferred fit of each shirt part were different and the effect of body shape was stronger than body size.

• Korean Journal of Materials Research
• /
• v.20 no.10
• /
• pp.550-554
• /
• 2010

This work presents a fabrication procedure to make large-area, size-tunable, periodically different shape metal arrays using nanosphere lithography (NSL) combined with ashing and annealing. A polystyrene (PS, 580 ${\mu}m$) monolayer, which was used as a mask, was obtained with a mixed solution of PS in methanol by multi-step spin coating. The mask morphology was changed by oxygen RIE (Reactive Ion Etching) ashing and temperature processing by microwave heating. The Au or Pt deposition resulted in size tunable nano patterns with different morphologies such as hole and dots. These processes allow outstanding control of the size and morphology of the particles. Various sizes of hole patterns were obtained by reducing the size of the PS sphere through the ashing process, and by increasing the size of the PS sphere through annealing treatment, which resulted in tcontrolling the size of the metallic nanoparticles from 30 nm to 230 nm.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2006.05a
• /
• pp.197-198
• /
• 2006

In the solid freeform fabrication (SFF) system using selective laser sintering (SLS), polyamide-12 powder is currently recognized as general material. In this study, some kinds of polyamide-6 powders with different shape and particlesize were fabricated to investigate the formability, the microstructure and mechanical properties. Also, to develop a more elaborate and rapid system, this study employs a new SLS device with a 3-axis dynamic focusing scanner system instead of the existing fe lens used in commercial SLS. Polyamide-6 powders having the average size of 100 m were treated thermally in order to keep the spherical symmetry in shape. These polyamide-6 powders were mixed with polyamide-12 powders having the average size of 50 m to give the bimodal distribution of size. These mixed powders showed the better fabrication in the selective laser sintering process because the smaller particles of polyamide-11 played an important role in the compact packing of powders by filling the void space between the large particles of polyamide-6. Also, Experiments have performed to evaluate the effect of a scanning path and sintering parameters by fabricating the various 3D objects.

• Journal of the Korean Vacuum Society
• /
• v.2 no.2
• /
• pp.199-208
• /
• 1993

The effect of nucleation free energy related to Si surface states on diamond film growth behavior has been studied. Ar first, the three kinds of diamond thin films (A, B, C) were deposited on various Si substrates (A-Si, B-Si, C-Si) whose surfaces were polished with 1 ${\mu}m$ diamond paste, 6 ${\mu}m$ Al_2O_3$ powder and 12 ${\mu}m$ Al_2O_3$ powder respectively. And then, relative nucleation free energy calculated is ${\Delta}G_{A-Si}<{\Delta}G_{B-Si}<{\Delta}G_{C-Si}$. Although there are some difference in grain size, shape and nucleated size, the thin films on A-Si and B-Si were diamond including a small amount of DLC which was confirmed by AES, SEM, XRD, and RHEED. Namely, the diamonds of films (B) were not nucleated in scratches but in dents and larger in grain size compare with the film (C) of which diamond sere nucleated not only scratches but also dents. And, the sphere diamond which is not general shape was grown on C-Si. After all, the sphere was turned out to be the diamond including much graphite as a result of the AES in situ depth profiling. Consequently, the diamond shape and quality grown on Si were Changed from the crystal which the (100) and (110) planes were predominent to the crystal in which (111) plane was predominent, and newt to sphere shape diamond including much graphite according as the nucleation free energy increases.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.32 no.6
• /
• pp.454-457
• /
• 2019

Controlling the shape of Ag nanoparticles (NPs) is very difficult. In the present work, urchin Ag NPs with different sizes and pod length control have been synthesized successfully in high yield by the concentration of a reducing agent. Unique Ag NPs were observed by TEM and SEM. These nanocrystals exhibit tunable surface plasmon resonance properties from the visible to near-infrared regions. They were applied to surface-enhanced Raman scattering (SERS) substrates using rhodamine 6G (R6G), benzenethiol (BT), and 4-amino benznethiol (4-ABT) molecules. The enhanced local field effect due to the sharp pod length, size, and surface plasmon of the urchin Ag NPs resulted in enhanced SERS properties and can serve as high-sensitivity substrates for SERS measurements.

• Journal of the Korean Geotechnical Society
• /
• v.39 no.1
• /
• pp.27-38
• /
• 2023

In this study, the impact of pile tip geometry, including shape, size, and angle, on the drivability and stress concentration during pile driving was investigated using 3D printing technology and finite element numerical analysis. A series of field loading tests were conducted on a test pile with various pile tip conditions, including width, angle, and shape. The changes in settlement were quantified as a ratio to the settlement of a conventional pile tip case and large deformation finite element analysis was used to investigate the maximum stress on a pile tip and the location of possible damage during pile driving. The results showed that by modifying the shape, size, and angle of the pile tip, the drivability of the pile could be improved and the maximum stress concentration around the pile tip could be significantly reduced, thereby ensuring the structural integrity of the pile during pile driving.

• Applied Science and Convergence Technology
• /
• v.26 no.5
• /
• pp.129-132
• /
• 2017

We report a chemical vapor deposition approach and optimized growth condition to the synthesis of single layer molybdenum disulfide ($MoS_2$). Obtaining large grain size with continuous $MoS_2$ atomically thin films is highly responsible to the growth distance between molybdenum trioxide source and receiving silicon substrate. Experimental results indicate that triangular shape $MoS_2$ grain size could be enlarged up to > 80um with the precisely controlled the source-to-substrate distance under 7.5 mm. Furthermore, we demonstrate fabrication of a memory device by employing poly(methyl methacrylate) (PMMA) as insulating layer. The fabricated devices have a PMMA-$MoS_2$/metal configuration and exhibit a bistable resistance switching behavior with high/low-current ratio around $10^3$.