• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.435-435
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• 2010

A inclined slot-excited plasma source is newly designed and constructed for higher flux HNB(Hyperthermal Neutral Beam) generation. The present source is different from the vertical SLAN(SLot ANtenna) sources [1] in two aspects. One is that the slots are inclined, and the other is that the magnetic field is configured to a cusp type. These modifications are intended to make the source plasma operated in sub-milli-torr pressure regime and as thin as possible, both of which is to get higher HNB flux by decreasing the re-ionization rate of the reflected atoms from the neutralizer [2]. The plasma is generated in a quartz tube of internal diameter 170 mm enclosed in a aluminum application chamber of larger diameter 250 mm. The microwave power is fed to the plasma chamber by 8 inclined slots cut into the application chamber wall. The slots are coupled the chamber to a WR280 waveguide wound around it to form a ring resonator. In order to make two slots $\lambda_g/2$ apart in phase, the adjacent slots are rotated in opposite directions. The rotation angle of the slots are set to $60^{\circ}$ from the chamber axis. Between the quartz chamber and the aluminum cylindrical chamber 8 NdFeB magnets are equally spaced and fixed to form the cusp magnetic field confinement and ECR (Electron Cyclotron Resonance) field. In this presentation, the magnetic and electromagnetic simulations, and the measured plasma parameters are given for both the inclined and the vertical slot-excited plasma sources. We also discuss how the sources can be tailored to suit better-performing HNB sources.

• Korean Journal of Materials Research
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• v.15 no.1
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• pp.25-30
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• 2005

The microstructural changes by hot extrusion of AZ31B magnesium alloy were observed, and the relation to the tensile property was examined. The tensile properties as oriented longitudinal(L), half transverse(HT) and long transverse(LT) to the extrusion direction were investigated at $20^{\circ}C,\;100^{\circ}C,\;200^{\circ}C,\;300^{\circ}C\;and\;400^{\circ}C$, respectively. As the results, many recrystallized small grains distributed uniformly in large banded microstructures formed along the extrusion direction. The grain size of as-extruded specimen was around $30\~150\;{\mu}m$. As increasing the test temperature the tensile and yield strength with respect to the angle between the axis of the tensile and the longitudinal direction in extrusion was decreased, but their elongation were increased and their deviation between L and LT specimens have disappeared from $300^{\circ}C$. This mechanical anisotropy was reduced at elevated temperatures and almost disappeared at $400^{\circ}C$. It was considered that the homogenization was occured by the recrystallization and the change of slip system was occurred during tensile test process in elevated temperatures.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.9
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• pp.1071-1076
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• 2011

NC machines are generally used for machining operations because of their position accuracy, path accuracy, and machining reaction force. However, some NC machines require a very large space and are expensive. Recently, industrial articulated robot arms with large handling capability and wrist torque have been developed and the corresponding sensor technology has been improved. A machining robot for three-dimensional large curved objects was developed on the basis of an automatic-path-generation method. A self-position-compensation method with a laser displacement sensor was adopted for the six-axis robot developed, because the large articulated robot arms had poor position accuracy. An automatic-path-generation method using specific points was adopted to reduce the number of teaching points and time. In order to determine the proper machining conditions, various machining conditions such as tool rotation speed, cutting angle, cutting depth, and tool moving speed, were evaluated.

• Journal of Biomedical Engineering Research
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• v.19 no.2
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• pp.143-152
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• 1998

In this paper, we present the performances of a Doppler system using single channel RF(Radio Frequency) sampling. This technique consists of undersampling the ultrasonic blood backscattered RF signal on a single channel. Conventional undersampling method in Doppler imaging system have to use a minimum of two identical parallel demodulation channels to reconstruct the multigate analytic Doppler signal. However, this system suffers from hardware complexity and problem of unbalance(gain and phase) between the channels. In order to reduce these problems, we have realized a multigate pulsed Doppler system using undersampling on a single channel, It requires sampling frequency at $4f_o$(where $f_o$ is the center frequency of the transducer) and 12bits A/D converter. The proposed " single-Channel RF Sampling" method aims to decrease the required sampling frequency proportionally to $4f_o$/(2k+1). To show the influence of the factor k on the measurements, we have compared the velocity profiles obtained in vitro and in vivo for different intersequence delays time (k=0 to 10). We have used a 4MHz center frequency transducer and a Phantom Doppler system with a laminar stationary flow. The axial and volumetric velocity profiles in the vessel have been computed according to factor k and have been compared. The influence of the angle between the ultrasonic beam and the flow axis direction, and the fluid viscosity on the velocity profiles obtained for different values of k factor is presented. For experiment in vivo on the carotid, we have used a data acquisition system with a sampling frequency of 20MHz and a dynamic range of 12bits. We have compared the axial velocity profiles in systole and diastole phase obtained for single channel RF sampling factor.ng factor.

• Journal of Korean Neurosurgical Society
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• v.60 no.5
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• pp.560-566
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• 2017

Objectvie : The global sagittal postural patterns as characterized by Roussouly classification have been previously described in various ethnicities, there were no studies investigated in Koreans. To analyze the distribution of the global sagittal postural patterns in Korean adults using Roussouly classification, the author prospectively studied. Methods : 252 asymptomatic Korean adults was recruited. Data was obtained by reviewing the films for each subject. Spinopelvic parameters were measured and sagittal postural patterns were then determined according to Roussouly classification. We compared the data across different ethnicities from our study and a previous study to further characterize Korean sagittal postures. Results : The subject included 151 males and 101 females, with mean age of $33.2{\pm}8.2years$. The average descriptive results were as below : thoracic kyphosis $28.6{\pm}7.7^{\circ}$, lumbar lordosis $48.3{\pm}10.2^{\circ}$, sacral slope $37.8{\pm}5.8^{\circ}$, pelvic incidence $45.1{\pm}7.5^{\circ}$, pelvic tilt $9.4{\pm}6.7^{\circ}$, spinosacral angle $130.1{\pm}5.4^{\circ}$, and sagittal vertical axis $16.25{\pm}22.5mm$. 125 subjects among 252 (49.6%) belonged to Roussouly type 3 (namely neutral). There were also 58 (23%), 33 (13.1%), and 36 (14.3) subjects in type 1, 2, and 4 (namely non-neutral), respectively. Conclusion : Enrolling 252 asymptomatic Korean adults, this prospective study found that 49.6% of asymptomatic Korean adults possessed a sagittal posture of Roussouly type 3. All radiologic parameters follows general concept of spinal sagittal balance pattern. Overall, this study might be a basis for further investigation of spinal sagittal balance.

• Nuclear Engineering and Technology
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• v.43 no.2
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• pp.133-140
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• 2011

In this paper, a deformation measurement technology for nuclear fuel rods is proposed. The deformation measurement system includes a high-definition CMOS image sensor, a lens, a semiconductor laser line beam marker, and optical and mechanical accessories. The basic idea of the proposed deformation measurement system is to illuminate the outer surface of a fuel rod with a collimated laser line beam at an angle of 45 degrees or higher. For this method, it is assumed that a nuclear fuel rod and the optical axis of the image sensor for observing the rod are vertically composed. The relative motion of the fuel rod in the horizontal direction causes the illuminated laser line beam to move vertically along the surface of the fuel rod. The resulting change of the laser line beam position on the surface of the fuel rod is imaged as a parabolic beam in the high-definition CMOS image sensor. An ellipse model is then extracted from the parabolic beam pattern. The center coordinates of the ellipse model are taken as the feature of the deformed fuel rod. The vertical offset of the feature point of the nuclear fuel rod is derived based on the displacement of the offset in the horizontal direction. Based on the experimental results for a nuclear fuel rod sample with a formation of surface crud, an inspection resolution of 50 ${\mu}m$ is achieved using the proposed method. In terms of the degree of precision, this inspection resolution is an improvement of more than 300% from a 150 ${\mu}m$ resolution, which is the conventional measurement criteria required for the deformation of neutron irradiated fuel rods.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.10
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• pp.19-26
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• 2021

In fine-particle injection processing, hard fine particles, such as silicon carbide or aluminum oxide, are injected - using high-pressure air, and a small amount of material is removed by applying an impact to the workpiece by spraying at high speeds. In this study, a two-axis stage device capable of sequence control was developed to spray various shapes, such as circles and squares, on the surface during the micro-particle jetting process to understand the surface-shape micro-particle-processing characteristics. In the experimental device, two stepper motors were used for the linear movement of the two degree-of-freedom mechanism. The signal output from the microcontroller is - converted into a signal with a current sufficient to drive the stepper motor. The stepper motor rotates precisely in synchronization with the pulse-signal input from the outside, eliminating the need for a separate rotation-angle sensor. The major factors of the processing conditions are fine particles (silicon carbide, aluminum oxide), injection pressure, nozzle diameter, feed rate, and number of injection cycles. They were identified using the ANOVA technique on the design of the experimental method. Based on this, the surface roughness of the spraying surface, surface depth of the spraying surface, and radius of the corner of the spraying surface were measured, and depending on the characteristics, the required spraying conditions were studied.

• Journal of Korean Neurosurgical Society
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• v.64 no.6
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• pp.901-912
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• 2021

Objective : In the cervical spine, many surgical procedures have been developed to achieve optimal results for various disorders, including degenerative diseases, traumatic injury, and tumor. In this study, we report our experience and follow-up results with a new surgical technique for cervical spine entitled posterior floating laminotomy (PFL) in comparison with conventional laminectomy and fusion (LF). Methods : Data for 85 patients who underwent conventional LF (n=66) or PFL (n=19) for cervical spine disorders between 2012 and 2019 were analyzed. Radiological parameters, including cervical lordosis (CL), T1 slope (T1S), segmental lordosis (SL), and C2-7 sagittal vertical axis (SVA), were measured with lateral spine X-rays. Functional outcomes, comprising the modified Japanese Orthopaedic Association (mJOA), neck disability index (NDI), and visual analog scale (VAS) scores, were also measured. For the patients who underwent PFL, postoperative magnetic resonance image (MRI) was performed in a month after the surgery, and the degree of decompression was evaluated at the T2-weighted axial image, and postoperative computed tomography (CT) was conducted immediately and 1 year after the operation to evaluate the gutter fusion. Results : There was no difference in CL, T1S, SL, and C2-7 SVA between the groups but there was a difference in the preoperative and postoperative SL angles. The mean difference in the preoperative SL angle compared with that at the last follow-up was -0.3° after conventional LF and 4.7° after PFL (p=0.04), respectively. mJOA, NDI, and VAS scores showed significant improvements (p<0.05) during follow-up in both groups. In the PFL group, postoperative MRI showed sufficient decompression and postoperative CT revealed gutter fusion at 1 year after the operation. Conclusion : PFL is a safe surgical method which can preserve postoperative CL and achieve good clinical outcomes.

• Journal of Conservation Science
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• v.37 no.4
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• pp.312-321
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• 2021

Underwater archaeology relies heavily on photography and video image recording during surveillances and excavations like ordinary archaeological studies on land. All underwater images suffer poor image quality and distortions due to poor visibility, low contrast and blur, caused by differences in refractive indices of water and air, properties of selected lenses and shapes of viewports. In the Yellow Sea (between mainland China and the Korean peninsula), the visibility underwater is far less than 1 m, typically in the range of 30 cm to 50 cm, on even a clear day, due to very high turbidity. For photographing 1 m x 1 m grids underwater, a very wide view angle (180°) fisheye lens with an 8 mm focal length is intentionally used despite unwanted severe barrel-shaped image distortion, even with a dome port camera housing. It is very difficult to map wide underwater archaeological excavation sites by combining severely distorted images. Development of practical compensation methods for distorted underwater images acquired through the fisheye lens is strongly desired. In this study, the source of image distortion in underwater photography is investigated. We have identified the source of image distortion as the mismatching, in optical axis and focal points, between dome port housing and fisheye lens. A practical image distortion compensation method, using customized image processing software, was explored and verified using archived underwater excavation images for effectiveness in underwater archaeological applications. To minimize unusable area due to severe distortion after distortion compensation, practical underwater photography guidelines are suggested.

• Nano
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• v.13 no.11
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• pp.1850125.1-1850125.12
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• 2018

To reduce the imbalance of impedance matching between the magnetic metal nanowires and free space, $Fe/TiO_2$ core/shell nanowire arrays with different diameters were fabricated in the templates of anodic aluminum oxide membranes by electrodeposition. The influences of the microstructure on the microwave absorption properties of the $Fe/TiO_2/Al_2O_3$ composites were studied by the transmission/reflection waveguide method. It was demonstrated experimentally that both the interfacial polarization and the diameter of the $Fe/TiO_2$ core/shell nanowires have critical effects on the microwave absorption properties. We also investigated the angle dependence of the microwave absorption properties. Due to the interfacial polarization and associated relaxation, the $Fe/TiO_2/Al_2O_3$ composites exhibited optimal microwave absorption properties when microwave propagation direction was accordant with the axis of the nanowires. Finally, we managed to obtain an optimal reflection loss of below -10 dB (90% absorption) over 10.2-14.8 GHz, with a thickness of 3.0 mm and the minimum value of -39.4 dB at 11.7 GHz.