• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.463-466
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• 2001

In recent year, Ferroelectric $BLT(Bi_{4-x}La_{x}Ti_{3}O_{12})$ is a promising candidate materials. This study was practiced to make good conditions of BL T targets. In this study, calcination and sintering temperature were kept at $750^{\circ}C$, $1100^{\circ}C$ for 2 hour respectively. the density obtained 7.612, 7.98, $7.877g/cm^{3}$ as $La_{2}O_{3}$ contents were 0.0mol%, 0.25mol%, 0.5mol%. Especially, the lanthanum content of 0.5 mol% measured C-axis (117) preferred orientation more than the others targets in the XRD. In $\varepsilon_{r}-f$ relationship using by HP 4194 A impedance analyzer, the 0.5 mol% observed above 200 relative dielectric constant. but the dissipation factor was higher than others targets at 100Hz~13MHz range. SEM photograph with the content of $La_{2}O_{3}$ was observed like rod and plate types.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11b
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• pp.109-116
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• 2000

The objective of this study is to measure rim surface adhesion and to calculate motion resistance produced by the adhesion acting on the rim section of a circular wheel under sticky soil condition. The mechanisms of generating motion resistance by the adhesion on a circular wheel were analyzed through wheel motion. Experiments were conducted in an indoor soil bin that contains loam soil. A circular steel wheel was used for experiments. A part of the wheel rim was cut off, and transducers which can measure normal and tangential forces were installed in this section. Calculated motion resistance at a part of the rim section was superposed for one wheel rotation as motion resistance produced by the rim surface adhesion. The motion resistance increased with increasing the dynamic load. Ratio of the motion resistance to total motion resistance measured by an axis transducer was about 23 to 46 % in this study.

• Journal of the Korean Society for Advanced Composite Structures
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• v.3 no.4
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• pp.27-37
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• 2012

The construction of a moment connection for a rectangular hollow section (RHS) column and a H-shaped beam is difficult because the RHS is a closed section. When a inner diaphragm is used for such a connection, in general, it is installed after cutting the HSS columns, which results in increased construction work. This paper suggests a new fabrication method to overcome such problems: An inner diaphragm is welded to inside a C-shaped section first, and then a column is fabricated by welding two C-shaped sections. This fabrication method is superior to a classic method in terms of constructibility. An experimental and a numerical study using Ansys 9.0 were performed in order to compare the strength of connections with respect to the presence of concrete, the corner shape of diaphragm, and the axis of loading. The experimental results including initial stiffness and ultimate loads are reported and the analytical results including load transfer mechanism, degree of stress concentration, and strain distribution are also reported.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.80-80
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• 2000

The GPS can provide accurate position information on the earth. But GPS receiver can't give position information inside buildings. DR(Dead-Reckoning) or INS(Inertial Navigation System) gives position information continuously indoors as well as outdoors, because they do not depend on the external navigation information. But in general, the inertial sensors severely suffer from their drift errors, the error of these navigation system increases with time. GPS and DR sensors can be integrated together with Kalman filter to overcome these problems. In this paper, we developed a personal navigation system which can be carried by person, using GPS and electronic pedometer. The person's footstep is detected by an accelerometer installed in vertical direction and the direction of movement is sensed by gyroscope and magnetic compass. In this case the step size is varying with person and changing with circumstance, so determining step size is the problem. In order to calculate the step size of detected footstep, the neural network method is used. The teaming pattern of the neural network is determined by human walking pattern data provided by 3-axis accelerometer and gyroscope. We can calculate person's location with displacement and heading from this information. And this neural network method that calculates step size gives more improved position information better than fixed step size.

• 한국연소학회:학술대회논문집
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• 2006.04a
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• pp.79-85
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• 2006

In this study, to increase the mixing between flue gas and reducing agent, new shapes of $NH_3$ ejection nozzles are designed and experimentally and numerically tested. The nozzles have six holes perpendicular to the ambient flue gas flow and the tilting angle between direction of ambient flow and the hole axis is varied. To evaluate the mixing efficiency of the proposed nozzles, numerical and experimental tests are applied to several flow conditions comparing with single hole nozzle, which is commonly used in conventional SCR process. From the results the nozzle with tilted multi-holes has the large region of high turbulent intensity compared with conventional single hole nozzle. This is originated from the high vorticity near the upstream of the jet flow issuing from the hole. The high turbulent intensity and vorticity magnitude lead to enhanced mixing between flue gas and reducing agent. Hence, the most suitable moral ratio between NOx and reducing agent for the catalytic reaction can be obtained on behalf of the intensified scalar mixing within shorter physical mixing length.

• Proceedings of the KOSOMBE Conference
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• v.1998 no.11
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• pp.255-256
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• 1998

In this paper, we propose the multi-axial classification system using parallel coding method that is systemic and flexible properties for representing dental clinical behavior. The methodology and organization of this thesis as follows. First, an analysis of other classification systems. Second, the domain of medical behavior and axises using selected elements was were determined. Third, the new code system is constructed of these common factors in properties of prediction of hierarchy, brevity, simplicity, flexibility and mnemonic usage. Finally, the framework of classification system for dental was made using multi-axial code system. The result of the this study, the eight bases axis of multi-axial code system is composed and can be basic information of research for construction of classification system of all medical domain.

• Progress in Superconductivity
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• v.8 no.1
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• pp.8-15
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• 2006

The size of the superconducting domains and the critical current density inside these domains have to be enhanced for most of cryomagnetic applications of melt-textured YBCO bulks. To enlarge the size of the domains we studied the multi-seeding technique based on a well-established procedure for preparing high quality YBCO monoliths using self-made SmBCO seeds. The distance between the seeds was optimised as a result of the investigation of the effects of various seed distances on the characteristics of the grain boundary Junctions. The influences of a-b plane intersections and c-axis misalignments were researched. Thereby, a small range of tolerance of the misorientations between the seed crystals was found. Field mapping was applied to control the materials quality and the superconductor's grain structure was investigated using polarisation microscopy. YBCO function elements with iou. seeds in a line and an arrangement of making type (100)/(100) and (110)/(110) boundary junctions, respectively, were processed. The trapped field profile in both sample types shows single domain behaviour. To demonstrate the potential of the multi-seeding method a ring-shaped sample was processed by placing sixteen seeds in a way to make both (100)/(100) and (110)/(110) grain junctions at the same time. The results up to now are very promising to prepare large single domain melt-textured YBCO semi-finished products in complex shapes.

• Progress in Superconductivity
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• v.8 no.2
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• pp.132-137
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• 2007

We have studied superconducting parameters of $MgB_2$ single crystals from reversible magnetization measurements with the magnetic field both parallel and perpendicular to the c-axis of the crystals. The temperature dependence of the London penetration depth, ${\lambda}_{ab}{^{-2}}(T)$, obtained from the Hao-Clem analysis on reversible magnetization, shows a clear discrepancy from single-band theories. It is also found that the anisotropies of the London penetration depth, ${\gamma}_{\lambda}$, slowly increases with temperature while the anisotropy of the upper critical field, ${\gamma}_H$, decreases with temperature. These behaviors are in sharp contrast with the behavior of superconductors with a single band. The temperature dependence of ${\lambda}_{ab}{^{-2}}$, and the opposite temperature dependences of ${\gamma}_{\lambda}\;and\;{\gamma}_H$ can be well explained with the theory of the two-band superconductivity.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.10
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• pp.45-52
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• 2001

This paper presents a study on the position tracking control of a robot system on the uncertain elastic base. The elastic bathe is a nonholonomic system but it can be changed into holonomic system, which is much easier to analyze, by modeling an elastic base as a virtual robot that has passive joints. Also, Jacobian operators, which represent the overall robot system including base movement, are defined and applied to the changed model. However, because base movements are not known, the exact Jacobian operators can＇t be estimated. The control algorithm proposed is that uses only Jacobians of a real robot as approximate Jacobian operators. Therefore the approximate Jacobian operators compensate the measured errors from external sensors. The proposed control strategy is evaluated by the simulation and experiment of a single-axis robot system on the elastic base.

• Transactions of Materials Processing
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• v.1 no.1
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• pp.66-74
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• 1992

According to the variation of hydrostatic pressure on the central axis of deformable material, the V-shaped central bursting defect may be created in extrusion or drawing processes. The process factors which affect the generation of defects are semi-angle of die, reduction ratio of cross-sectional area, friction factor, material properties and so on. The combination of these factors can determine the possibility of defect creation and the shape of various round holes which have been created inside already. By the rigid plastic finite element method, this paper describes the observations of change in shape of round holes with process conditions such as semi-angle of die, reduction ratio of cross-sectional area and friction factor at the non-steady state of axisymmetrical extrusion process when the round hole is already existed inside the original billet. Also, the effects of process factors are investigated to prevent the possible defects.