• Progress in Superconductivity and Cryogenics
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• v.18 no.2
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• pp.30-36
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• 2016

For the magnetic field analysis or design, it is important to know the behavior of the magnetic field in an interesting space. Magnetic field mapping becomes a useful tool for the study of magnetic field. In this paper, a numerical way for mapping the magnetic field within the cylindrical center volume of magnet is presented, based on the solution of the Laplace's equation in the cylindrical coordinate system. The expression of the magnetic field can be obtained by the magnetic flux density, which measured in the mapped volume. According to the form of the expression, the measurement points are arranged with the parallel cylindrical line (PCL) method. As example, the magnetic flux density generated by an electron cyclotron resonance ion source (ECRIS) magnet and a quadrupole magnet were mapped using the PCL method, respectively. The mapping results show the PCL arrangement method is feasible and convenience to map the magnetic field within a cylindrical center volume generated by the general magnet.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.35.3-35
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• 2001

Developed is an optical auto-inspection system to detect some microscopic defects on the Inside surface of the hydraulic automobile brakes at the production line. A small cylindrical detection module with a solid laser source at its center has two rings of optical fibers to separately collect light reflected and scattered from the defects on the surface. The cylindrical brake part rotates with respect to the detection module that will move parallel to the rotational axis of the cylinder. Thus, the optical module can scan the whole inside surface area. The automatic detection of the defects is to compare the intensity distributions ...

• Progress in Superconductivity and Cryogenics
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• v.17 no.2
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• pp.31-35
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• 2015

Mapping is a useful tool in the magnetic field analysis and design. In some specific research area, such as the nuclear magnetic resonance (NMR) or the magnetic resonance imaging (MRI), it is important to map the magnetic field in the interesting space with high accuracy. In this paper, an indirect mapping method in the center volume of an air-core solenoid is presented, based on the solution of the Laplace's equation for the field. Through the mathematical analysis on the mapping calculation, we know that the condition number of the matrix, generated by the measurement points, can greatly affect the error of mapping result. Two different arrangement methods of the measurement points in field mapping are described in this paper: helical cylindrical line (HCL) method and parallel cylindrical line (PCL) method. According to the condition number, the HCL method is recommended to measure the field components using one probe. As a simple example, we mapped the magnetic fields in a MRI main magnet system. Comparing the results in the different methods, it is feasible and convenient to apply the condition number to reduce the error in the field mapping calculation. Finally, some guidelines were presented for the magnetic field mapping in the center volume of the air-core solenoid.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.6
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• pp.459-467
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• 2016

Using a line scan camera and a Galvano mirror, we constructed a high-speed line-scanning microscope that can generate 2D images ($8000{\times}8000pixels$) without any moving parts. The line scanner consists of a Galvano mirror and a cylindrical lens, which creates a line focus that sweeps over the sample. The measured resolutions in the x (perpendicular to line focus) and y (parallel to line focus) directions are both $2{\mu}m$, with a 2X scan lens and a 3X relay lens. This optical system is useful for measuring defects, such as spalling, chipping, delamination, etc., on the surface of carbon fiber reinforced plastic (CFRP) holes after machining in conjunction with adjustments in the angle of LED lighting. Defects on the inner wall of holes are measured by line confocal laser scanning. This confocal method will be useful for analyzing defects after CFRP machining and for fast 3D image reconstruction.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.8
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• pp.1527-1533
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• 2002

When a mechanism transfers a motion to an intersected shaft, a cylindrical cam mechanism may be the best choice among the mechanisms. The cylindrical cam with a roller follower provides to transfer the motions to the intersect shafts simply without other connecting equipments of the intersect shafts. Typical example may be a roller-gear-cam mechanism. But the shape of the cam must be exactly defined in order to satisfy the conditions for the prescribed motion of the follower. This paper proposes a new method for the shape design of the cylindrical cams and also a CAD program is developed by using the proposed method. The relative velocity method calculates the relative velocity of the follower versus the cam at a center of roller, and then determines a contact point by using the geometric relationships and the kinematic constraints. The constraint used in the relative velocity method is that the relative velocity must be parallel to a common tangent line at the contact point of two independent bodies, i. e. the cam and the follower. Then, the shape of the cam is defined by the coordinate transformation of the trace of the contact points. Finally, this paper presents an example in order to prove the accuracy of the proposed methods in this paper and the application of the CAD program"CamDesign".

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.314-319
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• 2002

The Automation and Control Group at the University of Brasilia is developing an automatic welding station based on an industrial robot and a controllable welding machine. Several techniques were applied in order to improve the quality of the welding joints. This paper deals with the implementation of a laser-based computer vision system to guide the robotic manipulator during the welding process. Currently the robot is taught to follow a prescribed trajectory which is recorded a repeated over and over relying on the repeatability specification from the robot manufacturer. The objective of the computer vision system is monitoring the actual trajectory followed by the welding torch and to evaluate deviations from the desired trajectory. The position errors then being transfer to a control algorithm in order to actuate the robotic manipulator and cancel the trajectory errors. The computer vision systems consists of a CCD camera attached to the welding torch, a laser emitting diode circuit, a PC computer-based frame grabber card, and a computer vision algorithm. The laser circuit establishes a sharp luminous reference line which images are captured through the video camera. The raw image data is then digitized and stored in the frame grabber card for further processing using specifically written algorithms. These image-processing algorithms give the actual welding path, the relative position between the pieces and the required corrections. Two case studies are considered: the first is the joining of two flat metal pieces; and the second is concerned with joining a cylindrical-shape piece to a flat surface. An implementation of this computer vision system using parallel computer processing is being studied.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.407-410
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• 2002

Monochromatic x-ray CT has several advantages over conventional CT, which utilizes bremsstrahlung white x-rays from an x-ray tube. There are several methods to produce such monochromatic x-rays. The most popular one is crystal diffraction monochromatization, which has been commonly used because of the fact that the energy spread is very narrow and the energy can be changed continuously. The alternative method is the use of fluorescent x-ray, which has several advantages such as large beam size and fast energy change. We have developed a parallel-beam and a fan-beam monochromatic x-ray CT, and compared some characteristics such as accuracy of CT numbers between those systems. The fan beam monochromatic x-rays were generated by irradiating target materials by incident white x-rays from a bending magnet beam line NE5 in 6.5 GeV Accumulation Ring at Tukuba. The parallel beam monochromatic x-rays were generated by using a silicon double crystal monochromator at the bending magnet beam line BL-20BM in Spring-8. A Cadmium telluride (CdTe) 256 channel array detector with 512mm sensitive width capable of operating at room temperature was used in the photon counting mode. A cylindrical phantom containing eight concentrations of gadolinium was used for the fan beam monochromatic x-ray CT system, while a phantom containing acetone, ethanol, acrylic and water was used for the parallel monochromatic x-ray CT system. The linear attenuation coefficients obtained from CT numbers of those monochromatic x-ray CT images were compared with theoretical values. They showed a good agreement within 3%. It was found that the quantitative measurement can be possible by using the fan beam monochromatic x-ray CT system as well as a parallel beam monochromatic X-ray CT system.

• Progress in Medical Physics
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• v.20 no.2
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• pp.72-79
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• 2009

Scatter correction for I-131 plays a very important role to improve image quality and quantitation. I-131 has multiple and higher energy gamma-ray emissions. Image quality and quantitative accuracy in I-131 imaging are degraded by object scatter as well as scatter and septal penetration in the collimator. The purpose of this study was to estimate scatter and septal penetration and investigate two scatter correction methods using Monte Carlo simulation. The gamma camera system simulated in this study was a FORTE system (Phillips, Nederland) with high energy, general-purpose, parallel hole collimator. We simulated for two types of high energy collimators. One is composed of lead, and the other is composed of artificially high Z number and high density. We simulated energy spectrum using a point source in air. We estimated both full width at half maximum (FWHM) and full width at tenth maximum (FWTM) using line spread function (LSF) in cylindrical water phantom. We applied two scatter correction methods, triple energy window scatter correction (TEW) and extended triple energy window scatter correction (ETEW). The TEW method is a pixel-by pixel based correction which is easy to implement clinically. The ETEW is a modification of the TEW which corrects for scatter by using abutted scatter rejection window, which can overestimate or the underestimate scatter. The both FWHM and FWTM were estimated as 41.2 mm and 206.5 mm for lead collimator, respectively. The FWHM and FWTM were estimated as 27.3 mm and 45.6 mm for artificially high Z and high density collimator, respectively. ETEW showed that the estimation of scatter components was close to the true scatter components. In conclusion, correction for septal penetration and scatter is important to improve image quality and quantitative accuracy in I-131 imaging. The ETEW method in scatter correction appeared to be useful in I-131 imaging.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.4 no.3_4
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• pp.79-91
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• 1971

A boat seine has been used as a major fishing gear for catching anchovy (Engraulis japonica) in the southern coastal waters of Korea since 1920s. The original seine was operated by two rowing boats as the haul seine. The rowing boats were, in recent, replaced by powered boats. The net size was enlarged by more than three times the original nit as they began to by operated in the deeper waters of approximately sixty meters. However, there are many problems in the efficiency of the fishing gear to be improved. The authors studied on the hydrodynamic resistance and performance of the boat seine net of the 1/10 scale model in tow. The results are summaried as follows. 1. The hydrodynamic resistance converted from model experiment into the full scale is: $$R_1=30,000\;v^{1.2}\;(0.2{\leqq}v{\leqq}1.0)$$ $$R_2=16,000\;v^2\;(0.2{\leqq}v{\leqq}0.6)$$ where $R_1$ and $R_2$ denote the resistance of whole gear and of bag net in kg respectively, and v the speed of flow in m/sec. 2. In the extension wing, approximately seventy percent of the length of the ground rope from the towing end to the inside-wing slopes down from sea level toward the sea bottom, while the thirty percent of the inside of it remains parallel with th: 5:a level. The performance is regarded to b: inefficient for driving fish shoal into the inside-wing, especially for the shoal diving suddenly. 3. At the towing speed higher than 0.2 m/sec, the trailing edge of the inside-wing is blown backward beyond the seaming line connecting the inside-wing and the mouth of the bag net. It is regarded as an unreasonable performance to drive the fish shoal smoothly into the bag net. 4. At the towing speed higher than 0.2 m/sec, the posterior end of the lower bosom is lifted up above the level of the ground rope of the inside-wing. It is considered that the fish shoal diving suddenly can escape through the discrepancy between the lower bosom and the sea bottom, even if the ground rope of the inside-wing sweeps the sea bottom. 5. The angle of inclination of the upper bosom is estimated as $35\~40^{\circ}$. It seems that the inclination is too steep to drive smoothly the fish shoal diving toward the sea bottom into the bag net. 6. In structure, circumference of the posterior section of the bag net is wider by 1.3 times that of the anterior section. Actually in towing at a speed higher than 0.2m/sec, however, the circumference of the posterior section becomes smaller than that of the anterior section. It is recommended to be designed in a long cylindrical form.