• Wind and Structures
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• v.7 no.3
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• pp.187-202
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• 2004

Wind tunnel experiments are often performed for the identification of aeroelastic parameters known as flutter derivatives that are necessary for the prediction of flutter instability for flexible structures. Experimental determination of all the eighteen flutter derivatives for a section model facilitates complete understanding of the physical mechanism of flutter. However, work in the field of identifying all the eighteen flutter derivatives using section models with all three degree-of-freedom (DOF) has been limited. In the current paper, all eighteen flutter derivatives for a streamlined bridge deck and an airfoil section model were identified by using a new system identification technique, namely, Iterative Least Squares (ILS) approach. Flutter derivatives of the current bridge and the Tsurumi bridge are compared. Flutter derivatives related to the lateral DOF have been emphasized. Pseudo-steady theory for predicting some of the flutter derivatives is verified by comparing with experimental data. The three-DOF suspension system and the electromagnetic system for providing the initial conditions for free-vibration of the section model are also discussed.

• Journal of Korean Dental Science
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• v.13 no.2
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• pp.73-80
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• 2020

Purpose: The purpose of this case study series was to introduce successful implant cases that used the palatal bone in patients with severe maxillary alveolar bone atrophy or defects. Case Presentation: In this case series study, a total of four patients underwent implant placement in the palatal bone of the maxilla. A total of 6 implants were installed using the palatine bone. The patients' ages ranged from 40 to 73 years with an average age of 63.5 years. The patients had maxillary sinus-related diseases, such as maxillary sinusitis, oroantral fistula, and dentigerous cysts, prior to implantation. To achieve initial stability, the implants were placed on the palatal side, and buccally tilted. The average postoperative recovery period was 8 months. No postoperative complications occurred in any of the cases, and the approach was used without reported issues. Conclusion: Implant treatment by securing the initial fixation in the palatal bone is a good alternative when an implant must be installed in a patient who requires extensive and invasive bone graft.

• Bulletin of the Korean Mathematical Society
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• v.26 no.2
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• pp.127-134
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• 1989

This paper proposes a deformation method for solving practical nonlinear programming problems. Utilizing the nonlinear parametric programming technique with Quasi-Newton method [6,7], the method solves the problem by imbedding it into a suitable one-parameter family of problems. The approach discussed in this paper was originally developed with the aim of solving a system of structural optimization problems with frequently appears in various kind of engineering design. It is assumed that we have to solve more than one structural problem of the same type. It an optimal solution of one of these problems is available, then the optimal solutions of thel other problems can be easily obtained by using this known problem and its optimal solution as the initial problem of our parametric method. The method of nonlinear programming does not generally converge to the optimal solution from an arbitrary starting point if the initial estimate is not sufficiently close to the solution. On the other hand, the deformation method described in this paper is advantageous in that it is likely to obtain the optimal solution every if the initial point is not necessarily in a small neighborhood of the solution. the Jacobian matrix of the iteration formula has the special structural features [2, 3]. Sectioon 2 describes nonlinear parametric programming problem imbeded into a one-parameter family of problems. In Section 3 the iteration formulas for one-parameter are developed. Section 4 discusses parametric approach for Quasi-Newton method and gives algorithm for finding the optimal solution.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1900-1907
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• 2012

Since the subpanels of polygonal-section shell have the corners of an obtuse angle larger than 90 degree unlike general plate or box-section structures, this could have an influence on forming nodal lines against local plate buckling or stress distributions. However, there is not sufficient material in the relevant study results or design recommendations. The very feasible models of the initial imperfections were acquired through the literature studies and then the parametric studies were conducted along with the initial imperfection models by using the finite element method. The parameters like the size of residual stresses, the portion of compressive residual stresses, and steel grades were considered. From the parametric studies, it was found that the maximum residual stress is more influential factor than the distribution pattern of residual stresses. In addition, The design strength equations for the simply supported plates can be applicable to the determination of the local buckling strength of the polygonal cross-section shell structures.

• Journal of Cerebrovascular and Endovascular Neurosurgery
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• v.25 no.2
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• pp.175-181
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• 2023

Objective: Endovascular treatment of cerebrovascular diseases is often challenging due to small caliber, tortuous distal vessels. Several devices and techniques have evolved to overcome these challenges. Recently, a low profile dual lumen microballoon catheter, specifically designed for distal navigation is employed for neurovascular procedures. Due to its recent advent, scarce data is available on clinical utility and safety of Scepter Mini. The aim of this case series is to report our initial experience with Scepter Mini in the management of various cerebrovascular diseases. Methods: All interventional neurovascular cases performed using Scepter Mini between January 2020 till April 2021 were included. Data regarding patient demographics, procedural details and complications was retrospectively collected from patient's electronic medical record and procedure reports. Results: Total twelve embolization procedures were performed in eleven patients, including six brain arteriovenous malformation, two dural arteriovenous fistula, one vein of Galen malformation and three hyper-vascular glomus tumor embolizations. All procedures were successfully performed with adequate penetration of the embolic agent. Complete embolization was performed in six procedures, while intended partial embolization was performed in the rest of procedures. Scepter Mini was solely used in ten procedures, however in the other two embolization procedures it was used as an additional conjunct tool to complete the intended embolization. No balloon related complication was observed in any procedure. Conclusions: Scepter Mini dual lumen microballoon catheter is safe and feasible for delivery of liquid embolic agents for cerebrovascular embolization procedures.

• International Journal of Highway Engineering
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• v.20 no.3
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• pp.65-73
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• 2018

PURPOSES : In this study, the propriety of expansion joint spacing of airport concrete pavement was examined by using weather and material characteristics. METHODS : A finite element model for simulating airport concrete pavement was developed and blowup occurrence due to temperature increase was analyzed. The critical temperature causing the expansion of concrete slab and blow up at the expansion joint was calculated according to the initial vertical displacement at the joint. The amount of expansion that can occur in the concrete slab for 20 years of design life was calculated by summing the expansion and contraction by temperature, alkali-silica reaction, and drying shrinkage. The effective expansion of pavement section between adjacent expansion joints was calculated by subtracting the effective width of expansion joint from the summation of the expansion of the pavement section. The temperature change causing the effective expansion of pavement section was also calculated. The effective expansion equivalent temperature change was compared to the critical temperature, which causes the blowup, according to expansion joint spacing to verify the propriety of expansion joint applied to the airport concrete pavement. RESULTS : When an initial vertical displacement of the expansion joint was 3mm or less, the blowup never occurred for 300m of joint spacing which is used in Korean airports currently. But, there was a risk of blow-up when an initial vertical displacement of the expansion joint was 5mm or more due to the weather or material characteristics. CONCLUSIONS : It was confirmed that the intial vertical displacement at the expansion joint could be managed below 3mm from the previous research results. Accordingly it was concluded that the 300m of current expansion joint spacing of Korean airports could be used without blowup by controling the alkali-silica reaction below its allowable limit.

• Proceedings of the KSR Conference
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• 2003.10b
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• pp.495-500
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• 2003

The effect of initial combined load on the lateral free vibration of arches is investigated. For the analysis, P-M interaction curves for the arches are obtained. The arches are circular arches which have constant cross-section and simply supported. Also, the arches are subjected both radial uniform distributed load which results in an axial compression on the cross-section and end moments that cause uniform bending action at the same time. All analysis are performed by finite element method based on Kang and Yoo's curved beam theory.

• Proceedings of the KSEEG Conference
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• 2002.04a
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• pp.163-166
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• 2002

Initial velocity model close to real velocity structure of the subsurface governs the quality of image of prestack depth migration. Geophysicists employ velocity estimation tools such as velocity analysis (curvature method, coherency inversion), tomography and waveform inversion. We present a reflection tomography that parameterizes the subsurface into the movable blocks. By interpreting the depth-migrated section or stacked section, we can design an initial constant velocity model having only impedance boundaries. We use shooting-raytracing method that allows us to calculate the Jacobian-matrix efficiently.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.10a
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• pp.452-461
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• 2003

The effect of initial combined load on the lateral free vibration of arches is investigated. For the analysis, P-M interaction own for the arches are obtained. The arches are circular arches which have constant cross-section and simply supported. Also, the arches are subjected both radial uniform distributed load which results in an axial compression on the cross-section and end moments that cause uniform bending action at the same time. All analysis are performed by finite element method based on Kang and Yoo's curved beam theory.

• Journal of Ocean Engineering and Technology
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• v.17 no.6
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• pp.16-22
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• 2003

In this paper, the method of determining the economically-optimal design section of rubble mound breakwater, using ADS program, was studied to supplement the deterministic approach. First of all, the design waves are computed, according to the return periods, using the Weibull distribution from the data of waves at the location of the breakwater. In order to take an optimal section, according to the return periods, the ADS program was used. The restriction conditions and objective functions are decided from the references of the specifications and standard manuals for Coastal and Harbor Construction Work. Results from this study support the ADS program as an appropriate method for determining the economically-optimal section of rubble mound breakwater, comparing the construction costs and the initial and damage repair costs for its life time.