• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2007.10a
• /
• pp.128-131
• /
• 2007

It is very important that there are saving resource and energy in the future as well as in these day. Weight saving of structural parts, which are formed by extrusion, plays a key role in manufacturing field. Especially these aluminum parts used in the car need other processes to vary the cross section in the axial direction. Thus, applications of these parts are limited by high cost. if the cross section of the parts is variable by only extrusion, application of extruded aluminum parts will more increase. Therefore, a new CNC extruder which can control the section area of a car part was invented the nation's first. Using the extrusion machine, the experiment and FE analysis were performed during the varied section extrusion process.

• International Journal of Highway Engineering
• /
• v.15 no.3
• /
• pp.23-29
• /
• 2013

PURPOSES: This paper aims to give a guideline and the way to apply the advanced composite materials theory to the road structures with different cross sections to the practicing engineers. METHODS: To simple but exact method of calculating natural frequencies corresponding to the modes of vibration of road structures with different cross sections and arbitrary boundary conditions. The effect of the $D_{22}$ stiffness on the natural frequency is rigorously investigated. RESULTS: Simple method of vibration analysis for calculating the natural frequency of the different cross sections is presented. CONCLUSIONS: Simple method of vibration analysis for calculating the natural frequency of the different cross sections is presented. This method is a simple but exact method of calculating natural frequencies of the road structures with different cross sections. This method is extended to be applied to two dimensional problems including composite laminated road structures.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.28 no.4
• /
• pp.1-12
• /
• 2024

In this study, a determination method of structural member section based on Nonlinear behaviors of steel cable-stayed bridges and the Harmony Search algorithm was presented. The Harmony Search algorithm determines the structural member section of cable-stayed bridges by repeating the process of setting the initial value, initializing the harmony memory, configuring the new harmony memory, and updating the harmony memory to search for the optimal value. The nonlinear initial shape analysis of a three-dimensional steel cable-stayed bridge was performed with the cross-section of the main member selected by the Harmony Search algorithm, and the optimal cross-section of the main members of the cable-stayed bridge, such as pylons, girders, cross-beams, and cables, reflecting the complex behavior characteristics and the nonlinearity of each member was determined in consideration of the initial tension and shape. The total weight was used as the objective function for determining the cross-section of the main member of the cable-stayed bridges, and the load resistance ability and serviceability based on the ultimate state design method were used as the restraint conditions. The width and height ratio of the girder and cross-section were considered additional restraint conditions. The optimal sections of the main members were made possible to be determined by considering the geometry and material nonlinearity of the pylons, girders, and cross-sections and the nonlinearity of the cable members. As a result of determining the optimal cross-section, it was confirmed that the proposed analysis method can determine the optimal cross-section according to the various constraint conditions of the cable-stayed bridge, and the structural member section of the cable-stayed bridge considering the nonlinearity can be determined through the Harmony Search algorithm.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.23 no.4
• /
• pp.338-346
• /
• 2013

Equations of motion of a rotating blade considering pre-twist angle, cross section taper and a concentrated mass are derived using the hybrid deformation variable modeling method. For the modeling of a concentrated mass which is located at an arbitrary position of the blade, a Dirac delta function is employed for the mass density function. The final equations for the vibration analysis are transformed into a dimensionless form using several dimensionless parameters. The effects of the dimensionless parameters on the vibration characteristics of the rotating blade are investigated through numerical analysis.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1997.03a
• /
• pp.130-135
• /
• 1997

A kinematically admissible velocity field is developed for the analysis of twisting of extruded products. The twisting of extruded product is caused by the linearly increased rotational velocity from the center on the cross-section of the workpiece at the die exit. In the analysis, the rotational velocity in angular direction is assumed by the multiplication of radial distance and angular velocity. The angular velocity is zero at the die entrance and is increased linearly by longitudinal distance from die entrance. The increase rate of angular velocity is determined by the minimization of plastic work. The results of the analysis show that the angular velocity of the extruded product changes with the aspect ratio of product and increases with the decreases in die length and in eccentricity of gravity center of the cross-section of workpiece at die entrance from that of the cross-section at the die exit.

• Journal of Preventive Medicine and Public Health
• /
• v.24 no.1 s.33
• /
• pp.29-36
• /
• 1991

A multiple regression analysis using ordinary least square (OLS) is frequently used for the projection of health expenditure as well as for the identification of factors affecting health care costs. Data for the analysis often have mixed characteristics of time series and cross section. Parameters as a result of OLS estimation, in this case, are no longer the best linear unbiased estimators (BLUE) because the data do not satisfy basic assumptions of regression analysis. The study theoretically examined statistical problems induced when OLS estimation was applied with the time series cross section data. Then both the OLS regression and time series cross section regression (TSCS regression) were applied to the same empirical da. Finally, the difference in parameters between the two estimations were explained through residual analysis.

• Proceedings of the KIEE Conference
• /
• 2005.07c
• /
• pp.2094-2096
• /
• 2005

In this paper, we studied the cross section analysis based on the short circuit conditions of the low voltage bare wires. The copper wires prepared for the experiment were 1.2mm 1.6mm and 2.0mm in diameter. Through the cross section analysis(CSA), it was confirmed that the dendrite structure grew at the angle of about $40^{\circ}$ or $60^{\circ}$ when the fusing current was applied to the wires. The larger the fusing current is, the more decreased the growth angle of the dendrite structure is. It was confirmed that the dendrite structure was arranged like the columnar structure. In this paper, the characteristics analysis of short circuit was carried out in the range of transient duration.

• Clinics in Shoulder and Elbow
• /
• v.21 no.2
• /
• pp.67-74
• /
• 2018

Background: Fatty degeneration of rotator cuff is a well-known predictor of postoperative outcome. The purpose of this study was to evaluate the clinical features of rotator cuff tears involving subscapularis, and investigate whether fatty degeneration quantified from only the upper subscapularis correlates better with clinical outcomes than quantified from the whole subscapularis. Methods: We retrospectively analyzed 315 consecutive patients who underwent arthroscopic repair for rotator cuff tears involving subscapularis with a minimum follow-up of 1 year. Preoperative and postoperative visual analogue score for pain, range of motion and functional scores were assessed. Integrity of the repaired tendon was assessed at the 1-year follow-up with either magnetic resonance imaging or ultrasonography. Results: The mean Goutallier grade of whole cross-section was significantly lower than that of upper cross-section (1.59 vs. 1.71, p<0.05), but significantly higher than that of lower cross-section (1.59 vs. 1.01, p<0.05). In analysis of 37 re-tears, the occupancy of severe fatty degeneration in upper cross-section was 86.5%, which was significantly higher than that seen in whole cross-section (56.8%, p<0.05). We calculated the cut-off tear size for prediction of re-tears as 19.0 mm for retraction and 11.0 mm for superior-inferior. The cut-off Goutallier grade was 2.5 for both whole and upper cross-sections, but area under the curve was greater in the upper cross-section than the whole (0.911 vs. 0.807). Conclusions: As fatty degeneration of upper subscapularis demonstrated a more distinct spectrum than whole subscapularis, we suggest that measuring fatty degeneration of upper subscapularis can be a more useful method to predict clinical prognosis.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.14 no.4
• /
• pp.118-125
• /
• 2015

The roll-forming process is a highly productive incremental forming process and is suitable for manufacturing thin, high-strength steel products. Recently, this process has been considered one of the most productive processes in manufacturing high-strength steel automotive structural parts. However, it is very difficult to develop the roll-forming process when the cross-sectional shape of the product changes in the longitudinal direction. In this study, a roll-forming process for manufacturing high-strength steel automotive parts with a linearly variable symmetric hat-type cross-section was developed. The forming rolls were designed by the 3D CAD system, CATIA. Additionally, the designed forming rolls were modified by the simulation through the 3D elastic-plastic finite element analysis software, MARC. The results of the finite element analysis show that the final roll-forming roll can successfully produce the desired high-strength steel automotive part with a variable cross-section.

• Composites Research
• /
• v.17 no.4
• /
• pp.25-31
• /
• 2004

In this study, a refined beam analysis model has been developed for multi-celled composite blades with elliptic cross-sections. Reissner's semi-complimentary energy functional is introduced to describe the beam theory and also to deal with the mixed-nature of the formulation. The wail of elliptic sections is discretized into finite number of elements along the contour line and Gauss integration is applied to obtain the section properties. For each cell of the section, a total of four continuity conditions are used to impose proper constraints for the section. The theory is applied to single- and double-celled composite blades with elliptic cross-sections and is validated with detailed finite element analysis results.