• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.581-584
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• 2008

A generation of a particle beam is the key technique in a flow cytometry that measures the fluorescence and light scattering of individual cell and other particulate or molecular analytes in biomedical research. Recent methods performing this function require a laborious and time-consuming assembly. In the present work, we propose a novel device for the generation of an axisymmetrical focusing beam of microparticles (3-D focusing) in a single capillary without sheath flows. This work uses the concept that the particles migrate toward the centerline of the channel when they lag behind the parabolic velocity profile. Particle focusing of spherical particles was successfully made with a beam diameter of about 10 ${\mu}$m. Proposed device provides crucial solutions for simple and innovative 3-D particle focusing method for the applications to the MEMS-based micro-flow cytometry. We believe that this device can be utilized in a wide variety of applications, such as biomedical/ biochemical engineering.

• Journal of the Optical Society of Korea
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• v.13 no.1
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• pp.22-27
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• 2009

Target design study to improve the quality of an accelerated proton beam from the interaction of a high-intensity short pulse laser with an overdense plasma slab has been accomplished by using a two-dimensional, fully electromagnetic and relativistic particle-in-cell (PIC) simulation. The target consists of a thin core part and a thick peripheral part of equivalent plasma densities, while the ratio of the radius of the core part to the laser spot size, and the position of the peripheral part relative to the fixed core part were varied. The positive effects of this core-peripheral target structure could be expected from the knowledge of the typical target normal sheath acceleration (TNSA) mechanism in a laser-plasma interaction, and were apparently evidenced from the comparison with the case of a conventional simple planar target and the case of the transversal size reduction of the simple planar target. Improvements of the beam qualities including the collimation, the forward directionality, and the beam divergence were verified by detailed analysis of relativistic momentum, angular directionality, and the spatial density map of the accelerated protons.

• Journal of Satellite, Information and Communications
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• v.7 no.2
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• pp.25-29
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• 2012

In this paper, we implemented LED beam forming communication system controlled by stepping motor. ATMega1284 was used as a MCU of main control board which has two main external IO, one is RS232 for connection with PC, the other is PORT for connection with motor driving board. Stepping motor rotated 360 degree when provided 160 clock and its rotation radius was increased by Archimedian Spiral. So LED can provide its light anywhere in the space and its beam forming was controlled by PC connected with RS232 of main control board. The action of beam forming was verified via actual HW/SW implementation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.322-325
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• 2005

The shrinking critical dimensions of modern technology place a heavy requirement on optimizing feature shapes at the micro- and nano scale. In addition, the use of ion beams in the nano-scale world is greatly increased by technology development. Especially, Focused ion Beam (FIB) has a great potential to fabricate the device in nano-scale. Nevertheless, FIB has several limitations, surface swelling in low ion dose regime, precipitation of incident ions, and the re-deposition effect due to the sputtered atoms. In recent years, many approaches and research results show that the re-deposition effect is the most outstanding effect to overcome or reduce in fabrication of micro and nano devices. A 2D string based simulation software AMADEUS-2D $(\underline{A}dvanced\;\underline{M}odeling\;and\;\underline{D}esign\;\underline{E}nvironment\;for\;\underline{S}putter\;Processes)$ for ion milling and FIB direct fabrication has been developed. It is capable of simulating ion beam sputtering and re-deposition. In this paper, the 2D FIB simulation is demonstrated and the characteristics of ion beam induced direct fabrication is analyzed according to various parameters. Several examples, single pixel, multi scan box region, and re-deposited sidewall formation, are given.

• Structural Engineering and Mechanics
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• v.74 no.3
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• pp.313-323
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• 2020

Non-destructive tests are commonly used in construction industry to access the quality and strength of concrete. However, till date there is no non-destructive testing method that can be adopted to evaluate the bond condition of reinforced concrete beams. In this regard, the presented research work details the use of ultra-sonic pulse velocity test method to evaluate the bond condition of reinforced concrete beam. A detailed experimental research was conducted by testing four identical reinforced concrete beam samples. The samples were loaded in equal increments till failure and ultra-sonic pulse velocity readings were recorded along the length of the beam element. It was observed from experimentation that as the cracks developed in the sample, the ultra-sonic wave velocity reduced for the same path length. This reduction in wave velocity was used to identify the initiation, development and propagation of internal micro-cracks along the length of reinforcement. Using the developed experimental methodology, researchers were able to identify weak spots in bond along the length of the specimen. The proposed method can be adopted by engineers to access the quality of bond for steel reinforcement in beam members. This allows engineers to carryout localized repairs thereby resulting in reduction of time, cost and labor needed for strengthening. Furthermore, the methodology to apply the proposed technique in real-world along with various challenges associated with its application have also been highlighted.

• Imaging Science in Dentistry
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• v.45 no.4
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• pp.205-211
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• 2015

Purpose: This study was performed to compare the accuracy of micro-computed tomography (CT) and cone-beam computed tomography (CBCT) in detecting accessory canals in primary molars. Materials and Methods: Forty-one extracted human primary first and second molars were embedded in wax blocks and scanned using micro-CT and CBCT. After the images were taken, the samples were processed using a clearing technique and examined under a stereomicroscope in order to establish the gold standard for this study. The specimens were classified into three groups: maxillary molars, mandibular molars with three canals, and mandibular molars with four canals. Differences between the gold standard and the observations made using the imaging methods were calculated using Spearman's rho correlation coefficient test. Results: The presence of accessory canals in micro-CT images of maxillary and mandibular root canals showed a statistically significant correlation with the stereomicroscopic images used as a gold standard. No statistically significant correlation was found between the CBCT findings and the stereomicroscopic images. Conclusion: Although micro-CT is not suitable for clinical use, it provides more detailed information about minor anatomical structures. However, CBCT is convenient for clinical use but may not be capable of adequately analyzing the internal anatomy of primary teeth.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.2
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• pp.175-180
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• 2009

In this article, we fabricated polytetrafluoroethylene(PTFE) nozzle treated by ion beam, in order to fabricate polymer based electrospray micro thruster with super hydrophobic nozzle. To obtain the super hydrophobic surface, PTFE surface is treated by argon and oxygen plasma treatment process. The optimal condition is investigated argon and oxygen flow rate as well as the paalied energy level for the treatment process. Fabricated nozzle was evaluated by measuring contact angle, and the surface morphology was examined by using scanning electron microscope(SEM) and atomic force microscope(AFM). We observe that jetting becomes more stable and repeatable on the treated nozzle. And to evaluate performance of fabricated nozzle, we measure micro scale thrust using a cantilever and a nozzle treated by ion beam laser displacement sensor.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.4
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• pp.314-317
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• 2009

This paper describes the temperature characteristics of polycrystalline 3C-SiC micro resonators. The $1.2{\mu}m$ and $0.4{\mu}m$ thick polycrystalline 3C-SiC cantilever and doubly clamped beam resonators with $60{\sim}100{\mu}m$ lengths were fabricated using a surface micromachining technique. Polycrystalline 3C-SiC micro resonators were actuated by piezoelectric element and their fundamental resonance was measured by a laser vibrometer in vacuum at temperature range of $25{\sim}200^{\circ}C$. The TCF(Temperature Coefficient of Frequency) of 60, 80 and 100 On long cantilever resonators were -9.79, -7.72 and -8.0 ppm/$^{\circ}C$. On the other hand, TCF of 60, 80 and $100{\mu}m$ long doubly clamped beam resonators were -15.74, -12.55 and -8.35 ppm/$^{\circ}C$. Therefore, polycrystalline 3C-SiC resonators are suitable with RF MEMS devices and bio/chemical sensor applications in harsh environments.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.636-639
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• 2003

It is difficult to machine below 10 micrometers by conventional machining methods, such as micro-EDM. However, ultra micro machining using focused ion beam(FIB) is able to machine to 50 nanometers. In addition, 3 dimensional structures can be made by a combination of FIB and CVD to the level of 10 nanometers. Die ＆ moulds techniques are better than one-to-one machining techniques in the mass production of ultra size structures, in regards to production costs. In this case, the machining precision of die ＆ moulds affects produced parts. Also, it is advantageous to machine die ＆ moulds to the 10 micrometer level by FIB technique rather than other techniques. In this paper, the grooving characteristics for die ＆ mould materials by FIB were carried out experimentally in order to compare the machining characteristics of FIB with conventional machining methods. The results showed that the machining parameters and the scanning path of FIB affects the precision. The machined width and depth of the groove varied depending on the required depth due to the redeposition of the sputtered ion material accumulating on both the bottom and the side of the wall.

• Laser Solutions
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• v.18 no.4
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• pp.1-5
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• 2015

For continuous laser micro patterning on three-dimensional free form surface, innovative laser system is developed. The two axis galvanometer is combined with the dynamic focusing unit to increase optical distance. Also, it is synchronized with the 3 axis mechanical system. To determine laser machining sequence, laser CAM system is developed. It can make possible of 3D surface micro patterning under $25{\mu}m$ pattern width. The uniformity of pattern width is about 2.8% and it is validated that focal plane is well conserved by the dynamic focusing unit. Velocity and positional information of 1 axis is stage is fed to the scanner control board by the encoder signal and it makes possible real time synchronization. With this system, possible patterning volume is enlarged from $40{\times}40mm^2$ to $40{\times}120{\times}30mm^3$.