• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.289-297
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• 2000

The determination of surface topography is believed to be extremely important in the areas of contact mechanics, adhesion and friction. In order to describe topography of various frictional surface, the harding test was carried out under different experimental conditions in try friction. And fractal descriptors was applied to frictional surface of laser modified steel with image processing system These descriptors to analyze surface structure are fractal dimension. Surface fractal dimension can be determined by sum of intensity difference of surface pixel. Topography of frictional surface can be effectively obtained by fractal dimensions.

• Bulletin of the Korean Chemical Society
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• v.8 no.5
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• pp.403-405
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• 1987

A dynamic laser light scattering system has been constructed using a personal computer. The intensity of the scattered light was detected with a photomultiplier tube and a photon counter. The BCD output of the photon counter which is proportional to the intensity of scattered light is fed into a personal computer via an interface card. The personal computer was programmed as an autocorrelator in machine language. The data acquisition rate of the system was about 600 samples/s which is adequate for studies on the molecular dynamics of concentrated polymer solutions, polymer latices with large particle size, and polymer glass systems. The constructed system was tested with polystyrene latex and the measured diameter of the latex particle agrees well with the supplier's value.

• Korean Journal of Acupuncture
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• v.32 no.1
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• pp.30-38
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• 2015

Objectives : The aim of the study is to investigate the effects of low level laser treatment (LLLT) on the gait behavior in the rat model of arthritis. Methods : Knee arthritis was induced by the injection of $125{\mu}l$ of Complete Freund's Adjuvant(CFA) into the right hind knee joint cavity. Arthritic rats were divided 3 groups; arthritis group was used for control(CON), 10 min of laser treated group(LSR10), and 30 min of laser treated group(LSR30). LLLT was applied to KI 1 for 11 times under gaseous anesthesia. We performed several analyses under catwalk test including stand and swing time, duty cycle of paw steps, intensity and print area of steps, and stride length. Results : Stand and duty cycle of paw steps were increased significantly at 12 days after arthritis induction in LSR30 group. Swing time was decreased significantly at 12 days after arthritis induction in LSR10 group. In the analysis of intensity, print area and stride length, however, results did not show statistical significance during the time point of experiments. Conclusions : The data suggest that LLLT on the rat model of CFA induced arthritis showed beneficial effects by increase of stand time and duty cycle of paw steps and decrease of swing time. Therefore, LLLT could be useful option to improve gait discomfort in arthritis patients.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.11
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• pp.51-57
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• 2001

A light beam reflected from a machined surface generally containes information concerning about its surface roughness. This study examines and proposes a surface roughness measurement technique for on-machine measurement of machined surfaces. The technique is based on the measurement of a reflected laser beam pattern and the statistical analysis of its light intensity distribution. The surface roughness was found to be closely related to the standard deviation of the light intensity on the primary axis of the reflected pattern. An image acquisition device is made up of a laser diode, a half mirror, a screen, and a CCD camera. The exact image with the primary and secondary axes of a reflected laser beam pattern is calculated through such image processing algorithm as thresholding, edge detection, image rotation, segmentation, etc. A median filter and a surrounding light correction algorithm are improve the image quality and reduce the measuring error. Using the developed measuring device the effect of screen materials and workpiece and workpiece materials was investigated. Experimental results regarding to relatively high-quality surfaces machined by grinding, polishing, lapping processes have shown the measurement error is within 10% in the range of $0.1{mu}m~0.8{\mu}m R_q.$Therefore, the proposed method is thought to be effectively used when quick measurements is needed with workpieces fixed on the machine.

• Korea-Australia Rheology Journal
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• v.19 no.2
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• pp.61-66
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• 2007

The aggregation characteristics of red blood cells (RBCs) are known as important factors in the microvascular flow system, and increased RBC aggregation has been observed in various pathological diseases, such as thrombosis and myocardial infarction. This paper describes a simple microfluidic device for measuring the RBC aggregation by integrating a microfluidic slit rheometry and laser-backscattering technique. While a decreasing-pressure mechanism was applied to the microfluidic rheometry, a syllectogram (the light intensity versus time) showed an initial increase and a peak caused by the high shear stress-induced disaggregation, immediately followed by a decrease in the light intensity due to RBC aggregation. The critical shear stress (CST) corresponding to the peak intensity was examined as a new index of the RBC aggregation characteristics. The CST of RBCs increased with increasing aggregation-dominating protein (fibrinogen) in the blood plasma. The essential feature of this design was the combination of the rheometric-optic characterization of RBC aggregation with a microfluidic chip, which may potentially allow cell aggregation measurements to be easily carried out in a clinical setting.

• Journal of Sensor Science and Technology
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• v.13 no.3
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• pp.252-257
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• 2004

$Y_{2}O_{3}:Eu^{3+}$ thin films have been grown on $Al_{2}O_{3}$(0001) substrates by a pulsed laser deposition (PLD) method. The phosphor thin films were deposited at a substrate temperature of 500, 600, and $700^{\circ}C$ under the oxygen pressure of 100, 200, and 300 mTorr. The crystallinity, surface roughness and photoluminescence of the films are highly dependent on the substrate temperature and oxygen pressure. The films grown on $Al_{2}O_{3}$(0001) substrate even under the different substrate temperatures and oxygen pressures exhibited (222) preferred orientation. The luminescent spectra exhibited strong luminescence of ${^{5}D_{0}}-{^{7}F_{2}}$ transition within $Eu^{+3}$ peaking at 612 nm. The crystallinity and luminescence intensity of the films have been improved as the substrate temperature increasing. With increase of oxygen pressure from 50 to 300 mTorr, the crystallinity of the films has been uniformly decreased. The photoluminescence intensity and surface roughness have similar behaviors as a function of oxygen pressure. At 200 mTorr, both photoluminescence intensity and surface roughness show a maximum.

• 한국전자현미경학회:학술대회논문집
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• 2000.05a
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• pp.27-30
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• 2000

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.1
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• pp.31-37
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• 2011

Recently, the technology of surface treatment is being more important which affects the material cost reduction and substitution to the expensive material. The material used for the mechanical processing should have not only high intensity, but also strength toughness, wear resistance and corrosion resistance. In order to increase the durability and have better quality of the parts using such kind of tooling material, various kinds of research of the surface hardening through many kinds of heat resources is being done and practically applied. In this study, the characteristics of hardening surface zone for high strength of the press die material through laser beam irradiation are researched. In this study, it is experimentally observed by the status of the surface morphology, tensile strength, the hardness distribution of the base metal and wear condition by the surface hardness pattern by the laser beam based on the process parameters of $CO_2$ laser by using SM45C and STD11 used for press tool. Through this research, the characteristics of surface hardened zone for high strength of the thin metal by laser beam irradiation is done.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.652-655
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• 2001

In this paper, I have studied minimization of the kerf-width and surface burning which are occurred after the singulation process of multi layer $\mu$-BGA( thickness 1.1 mm, 0.9 mm) with a pulsed Nd:YAG( = 532 nm, repetition rate = 10 Hz) laser. The thermal energy of a pulsed Nd:YAG laser is used to cut the copper layer. I have studied are minimization of the surface burning and kerf-width using a photo resist, $N_2$blowing and polyester double sided tape as a cutting parameter. The $N_2$blowing reduces a laser energy loss by debris and suppresses a surface carbonization. Also, I have studied characters of cutting with a choice of side of laser beam incidence. The SEM(Scanning Electron Microscope), non-contact 3D inspector and high-resolution microscope are used to measure kerf width and surface state. The optimum value of 1.1 mm $\mu$-BGA singulation is 524 $\mu$m that is reduced kerf width of 60 % with $N_2$blowing. And I obtained reduction of carbonization of 68 % with a polyester double side tape in 0.9 mm $\mu$-BGA. I used laser intensity of 1.91$\times$10$^{6}$ / $\textrm{cm}^2$ in this study.

• IEMEK Journal of Embedded Systems and Applications
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• v.11 no.6
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• pp.379-392
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• 2016

This paper presents the design and simulation of a laser power beaming (LPB) system for an electric vehicle that establishes an optimal power transmission path based on the received signal strength. The LPB system is possible to transfer power from multiple transmitters to a single receiver according to the characteristics of the laser and the solar panel. When the laser beams of multiple transmitters aim at a solar panel at the same time, the received power is the sum of all energy at a solar panel. Our proposed LPB system consists of multiple transmitters and multiple receivers. The transmitter sends its power characteristics as optically coded pulses with a class 1 laser beam and powers as a high-intensity laser beam. By using the attenuated power level, the receiver can estimate the maximum receivable powers from the transmitters and select optimal transmitters. Throughout the simulation, we verified the possibility that different LPB receivers were achieved their required power by the optimal allocation of the transmitter among the various transmitters.