• Structural Engineering and Mechanics
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• v.45 no.2
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• pp.211-232
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• 2013

In this study a multi-objective optimization problem is solved. The objectives used here include simultaneous minimum construction cost in term of sections weight, minimum structural damage using a damage index, and minimum non-structural damage in term of inter-story drift under the applied ground motions. A high-speed and low-error neural network is trained and employed in the process of optimization to estimate the results of non-linear time history analysis. This approach can be utilized for all steel or concrete frame structures. In this study, the optimal design of a planar eccentric braced steel frame is performed with great detail, using the presented multi-objective algorithm with a discrete population and then a moment resisting frame is solved as a supplementary example.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.7
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• pp.595-600
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• 2016

An orbital grinding system uses a special motion to machine crankshafts in ships. When a crankshaft is operated, eccentric pins rotate and a grinding wheel moves in order to grind the pins. Thermal error caused by heat generated in the grinding process decreases the quality of the final product. In this study, the thermal error of an orbital grinding system caused by heat generation was investigated in order to predict the extent of thermal error that can occur during the grinding process. Since the machine position changes during orbital grinding, the pin part is divided into 30 degree intervals and heat is generated. Total thermal error was measured by summing the thermal errors associated with the pin and the grinding wheel. Total thermal error was found to reach a maximum at 60 degrees and a minimum at 210 degrees because of the shape of the crankshaft.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.154-162
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• 1991

In this study, the simulation program is developed where the tooth profile error in internal gear shaping is calculated considering several factors which affect it. This factors are the circular feed of the pinion cutter, the interference by the geometric conditions of the cutter and the internal gear, the deviation from the theoretical involute profile of the cutter and the eccentricity of the cutter and the internal gear. With this program, the effects are investigated which the geometric conditions and the cutting conditions in internal gear shaping have on the tooth profile error of the internal gear. The condition for the minimization of it is derived and then the results of simulation are adequately verified by measurements of internal gears cut by a pinion cutter.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.468-473
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• 2002

This paper presents the methodology for measuring eccentricity of the cylindricaliy machined part using CCS(Cylindrical Capacity Spindle Sensor) signal in the CNC turning process. In order to investigate the relationships between CCS orbits and eccentricities, the initial conditions for various eccentricity state and machining process is applied to the experimental strategy. AS a result, it is considered the linearities of CCS signal and magnitude of eccentricity of machined cylindrical surfaces based on the possibility as a automatic detection apparatus for the CNC lathe.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1659-1662
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• 2003

The mass measurement of solid density standards using weight exchanger is described. KRISS(Korea Research Institute od Standards and Science) has several solid density standards. Their mass have been measured manually only using a mass comparator(Mettler, 1kg - 0.01mg). However, the uncertaity of the manual mass measurement is up to 300 microgarm much more than 32 microgram of advanced NMIS(National Metrology Institutes) for 1 kg silicon sphere which is primary density standards due to an eccentric error and buoyancy correction error. The new system with a weight exchanger is designed and built to improve the measurement accuracy. It comprises a weight exchager, a mass comparator, air density instruments, and application program for automatic measurement. It is evaluated by measuring several elements in an air tight chamber to verify the performance of it.

• Coupled systems mechanics
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• v.13 no.3
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• pp.201-217
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• 2024

This study aims to develop a new model to obtain the minimum area in circular isolated footings with eccentric column taking into account that the surface in contact with the ground works partially in compression, i.e., a part of the contact area of the footing is subject to compression and the other there is no pressure (pressure zero). The new model is formulated from a mathematical approach based on a minimum area, and it is developed by integration to obtain the axial load "P", moment around the X axis "M_x" and moment around the Y axis "M_y" in function of σ_max (available allowable soil pressure) R (radius of the circular footing), α (angle of inclination where the resultant moment appears), y₀ (distance from the center of the footing to the neutral axis measured on the axis where the resultant moment appears). The normal practice in structural engineering is to use the trial and error procedure to obtain the radius and area of the circular footing, and other engineers determine the radius and area of circular footing under biaxial bending supported on elastic soils, but considering a concentric column and the contact area with the ground works completely in compression. Three numerical problems are given to determine the lowest area for circular footings under biaxial bending. Example 1: Column concentric. Example 2: Column eccentric in the direction of the X axis to 1.50 m. Example 3: Column eccentric in the direction of the X axis to 1.50 m and in the direction of the Y axis to 1.50 m. The new model shows a great saving compared to the current model of 44.27% in Example 1, 50.90% in Example 2, 65.04% in Example 3. In this way, the new minimum area model for circular footings will be of great help to engineers when the column is located on the center or edge of the footing.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.28 no.1
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• pp.7-16
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• 1998

The Scanora/sup (R)/ X-ray unit uses the principles of narrow beam radiography and spiral tomography. Starting with a panoramic overview as a scout image. multiple tomographic projections could be selected. This study evaluated the accuracy of spiral tomography in comparison to routine panoramic radiography for dental implant treatment planning. An experimental study was performed on a cadaver mandible to assess the accuracy of panoramic radiography and spiral tomography film images for measurement of metallic spheres. After radiographic images of the metallic spheres on the surgical stent were measured and corrected for a fixed magnification of radiographic images. following results were obtained. 1. In the optimal position of the mandible. the minimal horizontal and vertical distortion was evident in the panoramic radiography images. The mean horizontal and vertical magnification error in anterior sites was 5.25％ and 0.75％. respectively. The mean horizontal and vertical magnification error in posterior sites was 0.50％ and 1.50％. respectively. 2. In the displaced forward or in an eccentric position of the mandible. the magnification error of the panoramic radiography images increased significantly over the optimal position. Overall, the mean horizontal magnification error of the anterior site in the different positions changed dramatically within a range of -17.25％ to 39.00％, compared to the posterior range of -5.25％ to 8.50％. However, the mean vertical magnification error stayed with the range of 0.5％ to 3.75％ for all the mandibular positions. 3. The magnification effects in the tomographic scans were nearly identical for the anterior and posterior with a range of 2.00％ to 5.75％ in the horizontal and 4.50％ to 5.50％ in the vertical dimension, respectively. 4. A statistically significant difference between the anterior and posterior measurements was found in the horizontal measurements of the panoramic radiography images of the displaced forward and backward position of the mandible(P<0.05). Also a significant difference between the optimal panoramic and tomographic projections was found only in the vertical measurement(P<0.05).

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.2
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• pp.206-215
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• 2013

In this paper, a synchronization control technique of dual-servo motor driven press system is proposed. An independent cascade PID control technique has been applied to the conventional press system for advancement of control stability. However, it is not easy to reduce synchronous error using the independent cascade PID control technique when some different load disturbances are involved in each motor. The eccentric error of the slide caused by the problem degrade the control performance of the BDC(Bottom Dead Center). In order to achieve reduction of the synchronous error between two servo motors and accurate position control simultaneously, a new control scheme comprised with cascade PID control loop and cross-coupling loop is proposed. In simulation using Matlab SIMULINK, the AC servo system is designed. The control performance of proposed technique is compared with conventional control technique to the model of AC servo system. Also, the sub-scale model of dual-servo motor driven press system which can replicate the slide motion is constructed for experimental verification for the performance of the proposed control technique. The cross-coupling control technique reveals more precise and stable performances in the position and synchronization controls.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.3
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• pp.159-166
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• 2022

In this study, slender reinforced concrete columns subjected to high temperatures and eccentric axial loads are evaluated by finite element analysis employing Abaqus (a finite element analysis program). Subsequently, the analysis results are compared and assessed. The sequentially coupled thermal stress analysis provided by Abaqus was employed to reflect the condition of an axially loaded column exposed to fire. First, heat transfer analysis was performed on the column cross-section. After verifying the results, another analysis was conducted: the cross-section was transformed into a three-dimensional element and then structural analyzed. In the analysis process, the column was modeled by accounting for the effects of tension stiffening and initial imperfection that could affect convergence and accuracy. The analysis results were compared with 74 experimental records, and an average error of 6% was observed based on the fire exposure and resistance. The foregoing indicates that the fire resistance performance of reinforced concrete columns can be predicted through finite element analysis.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.60 no.4
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• pp.206-213
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• 2011

Line sleeves, which used to connect ACSR cables when transmission lines were constructing, sometimes cause power transmission failure due to deterioration and corrosion. Therefore, power transmission line should be inspected regularly to prevent national disaster. Current inspection tool detects insertion length of transmission line on line sleeves, the inspection tool includes enormous error by operator. Moreover, the system is not controlled remotely, negligent accident would be caused while inspecting. To deal with those problems, KEPCO reviewed several ways to inspect line sleeves and proposes new method to inspect line sleeve by measuring magnetic flex which penetrate junction of steel and aluminum sleeve. The developed inspection tool is reliable enough to detect eccentric sleeves. Also, the developed inspection device was applied on actual transmission line and verified its effectiveness.