• Journal of the Korean Society of Visualization
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• v.8 no.1
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• pp.31-38
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• 2010

An experimental study to evaluate dynamic structures of flow and turbulence characteristics in bubble-driven liquid flow in a rectangular tank with a varying flow rate of compressed air is conducted. Liquid flow fields are measured by time-resolved particle image velocimetry (PIV) with fluorescent tracer particles to eliminate diffused reflections, and by an image intensifier to acquire enhanced clean particle images. Instantaneous vector fields are investigated by using the two frame cross-correlation function and bad vectors are eliminated by magnitude difference technique. By proper orthogonal decomposition (POD) analysis, the energy distributions of spatial and temporal modes are acquired. When Reynolds number increases, bubble-induced turbulent motion becomes dominant rather than the recirculating flow near the side wall. The total kinetic energy transferred to the liquid from the rising bubbles shows a nonlinear relation regarding the energy input because of the interaction between bubbles and free surface.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.98-99
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• 2012

Deposition of thin films using magnetron sputtering plasmas is a well-developed, classical technology. However, detailed investigations using advanced diagnostics are insufficient in magnetron sputtering, in comparison with plasma-aided dry etching and plasma-enhanced chemical vapor deposition. In this talk, we will show examples of diagnostic works on magnetron sputtering employing metal targets. Diagnostic methods which have fine spatial resolutions are suitable for magnetron sputtering plasmas since they have significant spatial distributions. We are using two-dimensional laser-induced fluorescence spectroscopy, in which the plasma space is illuminated by a tunable laser beam with a planer shape. A charge-coupled device camera with a gated image intensifier is used for taking the picture of the image of laser-induced fluorescence formed on the planer laser beam. The picture of laser-induced fluorescence directly represents the two-dimensional distribution of the atom density probed by the tunable laser beam, when an intense laser with a relatively wide line-width is used. When a weak laser beam with a relatively narrow linewidth is used, the laser-induced fluorescence represents the density distribution of atoms which feel the laser wavelength to be resonant via the Doppler shift corresponding to their velocities. In this case, we can obtain the velocity distribution function of atoms by scanning the wavelength of the laser beam around the line center.

• Korean Journal of Construction Engineering and Management
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• v.5 no.4 s.20
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• pp.139-146
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• 2004

Resent removal work for road signs has been labor intensive and required times since it has been done manually using shaving type equipment. While traditional process is conducting, there are traffic jams caused by the passing control, and happened unexpected accidents to workers working at dangerous road circumstance. Besides, in current shaving method, there are high potentialities on the air pollution as well as the explosive accident occurred by using a propane gas. So, as an alternative, we have studied to develop the automatic erasing equipment made up with a high pressure water-jet system and automatic control system, mobile system; Wate-rjet system consists of an intensifier and nozzles to give a high pressure and spray on the sign, and automatic control system is composed of one axis robot using a hydraulic servo actuator controlled by a lever, And as a mobile system, a truck plays an important role for the transport of equipment and the forward movement in a removal process. In this paper, we have analyzed the characteristics of road signs and have investigated current erasing methods in the field. And we have organized and designed automatic erasing equipment, and we have made a basic experiment to find out the optimal spray condition as like the spray distance, spray angle and injection pressure.

• Journal of Applied Reliability
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• v.11 no.3
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• pp.235-244
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• 2011

Hydraulic hose assemblies deliver a fluid power in various oil pressure equipment such as construction machinery, automobile, aircraft, industrial machinery, machine tools and machinery for ships. Also, they are widely used as pipes in oil pressure circuit. When we estimate their lifetime, it is essential to conduct an accelerated life test by choosing the factor that suits the usage condition of the test object since traditional test method for estimating lifetime under the influence of various external factors incurs hardship in terms of time and expenses. The objective of this study is to propose an acceleration model that takes both temperature and pressure without flexing condition into consideration. The lifetime is estimated by applying the proposed temperature-nonthermal acceleration model to the test data. And we compare the proposed temperature-nonthermal acceleration model and the accelerated life equation suggested by John(1994).

• Transactions on Electrical and Electronic Materials
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• v.12 no.6
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• pp.241-244
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• 2011

An isolator transmits light in the forward direction and blocks light from passing in the reverse direction. It is regarded an essential optical component in medical, industrial, and research lasers for blocking reflection beams that cause optical damage and noise. It is also used as a communicative light intensifier to expand the lifespan of devices and enhance transmission quality. This study analyzed the characteristics of the core components in the construction of a polarization-independent isolator, namely, the walk-off polarizer and the Faraday rotator. Measurement of the extinction ratio of the resultant walk-off polarizer revealed that the ratio between the vertical and horizontal rays was 1,050:1 with a laser output of 0.032 W and 1,010:1 with a laser output of 2.68 W, thus presenting ratios similar to 1,000:1. In addition, the walk-off polarizer and Faraday rotator constructed in this study were used to compare output changes according to changes in power of input light and to check the penetration ratio. Results from the study presented variations in output value according to changes in power of input light. However, the average penetration ratio remained relatively consistent (~81.4%).

• Journal of the Korean Society of Visualization
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• v.6 no.1
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• pp.41-46
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• 2008

In this paper, the recirculation flow motion and mixing characteristics driven by air bubble stream in a rectangular water tank is studied. The time-resolved PIV technique is adopted for the quantitative visualization and analysis. 488 nm Ar-ion CW laser is used for illumination and orange fluorescent ($\lambda_{ex}=540nm,\;\lambda_{em}=560nm$) particle images are acquired by a PCO 10bit high-speed CCD camera (1280$\times$1024). To obtain clean particle images, 545 nm long pass optical filter and an image intensifier are employed and the flow rates of compressed air is 3 l/min at 0.5 MPa. The recirculation and mixing flow field is further investigated by time-resolved POD analysis technique. It is observed that the large scale recirculation resulting from the interaction between rising bubble stream and side wall is the most dominant flow structure and there are small scale vortex structures moving along with large scale recirculation flow. It is also verified that the sum of 20 modes of velocity field has about 67.4% of total turbulent energy.

• Journal of radiological science and technology
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• v.26 no.1
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• pp.31-37
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• 2003

The conclusions after appraisal usefulness of korean 30 kHz inverter type X-ray equipments which are currently used in the clinics are like those followings. 1. The specific characters of mA, kVp, msec in the radiography keep very good accuracy and showed good waveform also under KS regulations. 2. The output of the X-ray equipment is showed 1.7 times higher than single-phase. 3. mA, kVp of the fluoroscopy and Sopt film exposure mA, kVp showed appropriated results under the regulations. 4. As we consider the conversion factor of image intensifier tube used for two years, it showed pretty high results, 310 at 75 kV, and knew that the conversion factor which followed by increasing kVp increased its computations like Kim's experimentation. Those X-ray equipment showed excellent results in the appraisal while those were operating so we think that those X-ray equipments will be substitute for expensive foreign equipment in korean domestic medical equipment in the future.

• Journal of Korean Foot and Ankle Society
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• v.19 no.4
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• pp.165-170
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• 2015

Purpose: The purpose of this study is to analyze the measurement differences of simple radiographs according to radiation projection angle using a phantom and to propose methods for objective analysis of simple radiographs. Materials and Methods: We took simple radiographs with different projection angles using a C-arm image intensifier and measured five parameters of the foot on the simple radiographic images. Five parameters include lateral tibiocalcaneal angle, lateral talocalcaneal angle, naviculocuboid overlap, lateral talo-first metatarsal angle, and lateral calcaneo-first metatarsal angle. Intraobserver and interobserver reliability were verified, and then intraclass correlations of parameters were analyzed. Results: Radiographic parameters of the foot showed high intraobserver and interobserver reliability. Lateral tibiocalcaneal angle has a strong negative linear relationship with rotation and a moderate negative linear relationship with tilt. Lateral talocalcaneal angle has a moderate positive linear relationship with rotation and a strong positive linear relationship with tilt. Naviculocuboid overlap has a strong positive linear relationship with rotation and a moderate positive linear relationship with tilt. Lateral talo-first metatarsal angle does not have a linear relationship with rotation and a moderate negative linear relationship with tilt. Lateral calcaneo-first metatarsal angle has a moderate positive linear relationship with rotation and tilt. Conclusion: More precise evaluation of the foot with a simple radiograph can be performed by understanding the changes of radiographic parameters according to radiation projection angle.

• Journal of the Korean Society of Radiology
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• v.10 no.5
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• pp.359-365
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• 2016

Fluoroscopy is performed when tissue or organ in the human body is examined, and it is used for diagnosis and procedure in back ailments. With regard to fluoroscopy equipment, distortion occurs on the peripheral part of fluoroscopic image rather than on its central part. This study measured distortion factors of vertical spacing ratio and distortion factor of diagonal spacing ratio before and after correction by applying a correction algorithm. According to measuring the vertical spacing ratio, post-correction standard deviation decreased by 0.04 in comparison with pre-correction one. Also measuring the diagonal spacing ratio, post-correction standard deviation decreased by 0.06 in comparison with pre-correction one. Consequently, the distortion of fluoroscopic image decreased after correction. A decrease in the distortion of image through the application of correction algorithm and the improvement of performance will be helpful in finding a correct position of lumbar puncture in nucleoplasty to treat lumbar disc herniation in the future.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.189-191
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• 2002

In the proton therapy using a gantry system, periodical verification of iso-center position is very important to assure precision of patient positioning system at any gantry angles in proton treatment. In the gantry system, there are three different types of iso-center; 1) in a geometrical view, 2) in an X-ray beam's eye view, 3) in a proton beam's eye view. Idealistically, they would be an identical point. They could, however, be different points. It may be a source of errors in patient positioning. At PMRC, we have established a system of verification for iso-center positions using a stainless ball of 2-cm in diameter and an imaging plate. This system provides the relation among a center of a patient target position, a center of proton irradiation field, and/or a center of X-ray field in accuracy of 50$\square$m in the 2) and 3) views, as images of a center of the stainless ball and a center of a 100 mm${\times}$100 mm-aperture brass collimator recorded on the imaging plate, which is setup at 1-cm behind the ball. In addition, it provides simultaneously the images of the ball and the collimator on an imaging intensifier (II), which is setup downstream of the proton or X-ray beam. We present a method of quality assurance (QA) for calibration of iso-center position in a rotation gantry system at PMRC and the performance of this system. A proton beam position on the 1$\^$st/ scatterer in the nozzle of the gantry affects less sensitive (reduced by a factor of 1/5) to the results of the iso-center position. The effect is systematically correctable. The effect of the nozzle (or the collimator) position is less than 0.5 mm at the maximum extraction (390 mm).