• Journal of the Institute of Electronics Engineers of Korea SP
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• v.39 no.4
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• pp.408-417
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• 2002

Gabor cosine and sine functions have widely been used to describe the human visual filters. This paper presents a new method to locally represent image frequency components using these functions. The parameters of basis functions are determined based on dc ripple and the sidelobe strength of step response. The resultant transform consisting of Gabor cosine and sine functions is compared with existing transforms by computing the joint effective width and by applying to the image reconstruction with the limited number of transformed coefficients. The experimental results show that the proposed transform has better performance than DGT and DCT.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.60-65
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• 2003

A new algorithm was developed to interpret joint orientations from a pair of images of the rock slope to overcome the limitation of photographing direction as in the parallel stereophotogrammetric system and to maximize the range of image measurement. This algorithm can be regarded as a modified multistage convergent photographing system. To determine camera parameters in the perspective projection equation that are the major elements in the photogrammetric technique, a new concept was developed by using three ground control points and single ground guide point. This method could be considered to be very simple when compared with other existing methods which use a number of ground control points and complicated analysis processes.

• Journal of Welding and Joining
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• v.28 no.2
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• pp.91-95
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• 2010

Stress distribution and deformation on the CT-type(Cross Tension type) spot welded lap joint subjected to out of plane tensile load were investigated by finite element method. Using the maximum principal stresses at the nugget edge obtained by FEM analysis, evaluated the fatigue strength of the CT-type spot welded lap joints having various dimensions and materials. and also, the influence of the geometrical parameters of CT-type spot welded lap joints on stress distribution and fatigue strength must be evaluated. thus, in this paper, ${\Delta}P-N_f$ curve were obtained by fatigue tests. Using these results, ${\Delta}P-N_f$ curve were systematically rearranged in the $\Delta\sigma-N_f$ relation with the hot spot stresses at the CT-type spot welded lab joints. It was found that the proposed $\Delta\sigma-N_f$ relation could provide a more reasonable fatigue design criterion for the CT-type spot welded lap joints.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.4
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• pp.127-131
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• 2010

Stainless steel sheets are widely used as the structural material for the railroad cars and the commercial vehicles. These kinds of structures used stainless steel sheets are commonly fabricated by using the gas welding. For fatigue design of gas welded joints such as fillet and plug type joint, it is necessary to obtain design information on stress distribution at the weldment as well as fatigue strength of gas welded joints. And also, the influence of the geometrical parameters of gas welded joints on stress distribution and fatigue strength must be evaluated. Thus, in this paper, ${\Delta}P-N_f$ curves were obtained by fatigue tests. Using these results, ${\Delta}P-N_f$ curves were rearranged in the. ${\Delta}{\sigma}-N_f$ relation with the hot spot stresses at the gas welded joints.

• Transactions of The Korea Fluid Power Systems Society
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• v.2 no.1
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• pp.1-8
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• 2005

Recently, swash plate type hydraulic axial piston motors/pumps are being extensively used in the world, because of simple design, light weight and effective cost. Structural problem of the swash plate type motor/pump is that tilting angle of swash plate should be limited to relatively small value and lateral farce on pistons has an undesirable effect in reciprocating motion. To solve these problems, piston rod mechanism, which is commonly used in bent axis type motor/pump, is considered to be applied to the swash plate type motor/pump. In this paper, kinematic analysis was done on the piston rod mechanism. A series of formula were derived and numerical calculations were done for a set of motor parameters.

• Steel and Composite Structures
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• v.21 no.2
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• pp.323-342
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• 2016

To study the effect of collar-plate reinforcement on the static strength of tubular T-joints under axial loading, fundamental research work is carried out from both experimental test and finite element (FE) simulation. Through experimental tests on 7 collar-plate reinforced and 7 corresponding un-reinforced tubular T-joints under axial loading, the reinforcing efficiency is investigated. Thereafter, the static strengths of the above 14 models are analyzed by using FE method, and it is found that the numerical results agree reasonably well with the experimental data to prove the accuracy of the presented FE model. Additionally, a parametric study is conducted to analyze the effect of some geometrical parameters, i.e., the brace-to-chord diameter ratio ${\beta}$, the chord diameter-to-chord wall thickness ratio $2{\gamma}$, collar-plate thickness to chord wall thickness ratio ${\tau}_c$, and collar-plate length to brace diameter ratio $l_c/d_1$, on the static strength of a tubular T-joint. The parametric study shows that the static strength can be greatly improved by increasing the collar-plate thickness to chord wall thickness ratio ${\tau}_c$ and the collar-plate length to brace diameter ratio $l_c/d_1$. Based on the numerical results, parametric equations are obtained from curving fitting technique to estimate the static strength of a tubular T-joint with collar-plate reinforcement under axial loading, and the accuracy of these equations is also evaluated from error analysis.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.2
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• pp.190-196
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• 2000

A hybrid position/force control scheme to regulate the force and position by dual arms is proposed where two arms are treated as one rm in a kinematic viewpoint. The force error calculated from the information of two force/torque sensors attached to the end of each arm is transferred to minimum configuration space coordinates and then is distributed to total system joint coordinates, The position adjustment at the total con-figuration coordinates is computed based on the effective compliance matrix with respect to total joint coordinates which is obtained by coordinate transformation between the task coordinates and the total joint coordinates. The proposed scheme is applied to sawing task. When the trajectory of the saw is planned to follow a line in a horizontal plane 2 position parameters are to be controlled(i.e., two translational positions) Also a certain level of contact force has to be controlled along the vertical direction(i.e. minus z-direction) not to loose the contact with the object to be sawn. We experimentally show that the performance of the velocity and force response are satisfactory. The proposed hybrid control scheme can be applied to arbitrary two cooperating arm system regardless of their kinematic structure and the number of actuated joints.

• Journal of Advanced Navigation Technology
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• v.13 no.4
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• pp.523-531
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• 2009

In this study, we propose a joint source/channel rate control algorithm for video encoder targeting packet erasure channel. Based on the buffer constraints of video communication systems, encoding rate constraint is presented. After defining source distortion models for coded and skipped video frames and a channel distortion model for packet errors and their propagation, an average distortion model of received video is proposed for a given encoding window. Finally, we define an optimization problem to minimize the average distortion for given channel rates and packet loss rates by controlling spatio-temporal parameters of source video and FEC block sizes. Then, we propose a window-based algorithm to solve the problem in real-time.

• Steel and Composite Structures
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• v.18 no.5
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• pp.1177-1195
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• 2015

Six specimens are tested to investigate the cyclic behavior of beam-to-column abnormal joints in steel moment-resisting frames, which are designed according to the principle of strong-member and weak-panel zone. Key parameters include the axial compression ratio of column and the section depth ratio of beams. Experimental results indicate that four types of failure patterns occurred during the loading process. The $P-{\Delta}$ hysteretic loops are stable and plentiful, but have different changing tendency at the positive and negative direction in the later of loading process due to mechanical behaviors of specimens. The ultimate strength tends to increase with the decrease of the section depth ratio of beams, but it is not apparent relationship to the axial compression ratio of column, which is less than 0.5. The top panel zone has good deformation capacity and the shear rotation can reach to 0.04 rad. The top panel zone and the bottom panel zone don't work as a whole. Based on the experimental results, the equation for shear strength of the abnormal joint panel zone is established by considering the restriction of the bottom panel zone to the top panel zone, which is suitable for the abnormal joint of H-shaped or box column and beams with different depths.

• Journal of the Korea Safety Management & Science
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• v.17 no.4
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• pp.143-151
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• 2015

The purpose of this study was to investigate temporal and spatial variations, and moments of the lower extremities of gait while playing the game with smartphone under different curb-heights. Ten male elementary school students(from 10 years to 13 years old) participated in this study. Twelve infrared cameras(Oqus-500) and two force plates(9260AA) were used for collecting data and these were processed via Visual 3D software. In conclusion, with or without smartphone and with different curb-heights, the spatial and temporal parameters of walking were not the same and coefficients of variations were not consistent. The maximum joint moments of the lower extremities with or without smartphone were not statistically significant but those of hip and ankle joint were statistically significant with regard to the different heights of the curbs.