• Journal of the Korean Orthopaedic Association
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• v.55 no.6
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• pp.495-502
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• 2020

Purpose: The aim of this study was to assess the effectiveness of domestically developed volar locking plate which has the concept of double-tiered subchondral support (DSS) in maintaining the reduction after distal radial fracture surgery. Materials and Methods: From July 2017 to December 2018, 54 patients were assessed. Plain radiographs were obtained immediately after surgery and at the last follow-up, and the radiographic parameters were measured in those images: radial length, radial inclination, volar tilt, ulnar variance, and distal dorsal cortical distance. The patients were subdivided into their age, type of fracture, and the position of the plate to evaluate the influence of each factors on the reduction maintenance. Results: Distal dorsal cortical distance in radiographs after the surgery was 5.91 mm (standard deviation, ±1.95 mm) on average. Significant differences in the radial length (p=0.038) and ulnar variance (p=0.001) were observed between immediately after surgery and at the last follow-up. When the parameters were evaluated by dividing the patients into subgroups according to the three specific factors, the ulnar variance showed a significant increase at the last follow-up when the patients were included 65-years-old or older. AO/OTA type C3 fracture, and Soong classification grade 0 plate position (p=0.007, p=0.012, p=0.046, respectively). Conclusion: Using the domestically developed DSS-type volar locking plate, significant reduction after distal radial fracture surgery could be maintained successfully. On the other hand, further study will be needed to determine about the reduction loss of the lunate facet identified in special cases that deal with fractures in elderly patients, unstable AO/OTA type C3 distal radial fractures, and Soong classification grade 0 plate position.

• Journal of Mechanical Science and Technology
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• v.17 no.1
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• pp.64-76
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• 2003

In this work, a new penalty formulation is proposed for the analysis of Mindlin-Reissner plates by using the element-free Galerkin method. A penalized weak form for the Mindlin-Reissner Plates is constructed through the exterior penalty method to enforce the essential boundary conditions of rotations as well as transverse displacements. In the numerical examples, some typical problems of Mindlin-Reissner plates are analyzed, and parametric studies on the order of integration and the size of influence domain are also carried out. The effect of the types of background cells on the accuracy of numerical solutions is observed and a proper type of background cell for obtaining optimal accuracy is suggested. Further, optimal order of integration and basis order of Moving Least Squares approximation are suggested to efficiently handle the irregularly distributed nodes through the triangular type of background cells. From the numerical tests, it is identified that unlike the finite element method, the proposed element-free Galerkin method with penalty technique gives highly accurate solution without shear locking in dealing with Mindlin-Reissner plates.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.3
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• pp.57-64
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• 2001

For the dynamic nonlinear analysis of stiffened plate and shell structures, total Lagrangian formulation is presented based upon the degenerated shell element considering finite rotation effects. Assumed strain concept is adopted in order to overcome shear locking phenomena and to eliminate spurious zero energy mode. In the elasto-plastic analysis, the return mapping algorithm based on the consistent elasto-plastic tangent modulus is applied to collapse analysis of shell structures. Newmark integration method is used for dynamic nonlinear analysis of shell structures under dynamic forces.

• Structural Engineering and Mechanics
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• v.15 no.1
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• pp.83-114
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• 2003

A new simple 3-node triangular flat-shell element with standard nodal DOF (6 DOF per node) is proposed for the linear and geometrically nonlinear analysis of very thin to thick plate and shell structures. The formulation of element GT9 (Long and Xu 1994), a generalized conforming membrane element with rigid rotational freedoms, is employed as the membrane component of the new shell element. Both one-point reduced integration scheme and a corresponding stabilization matrix are adopted for avoiding membrane locking and hourglass phenomenon. The bending component of the new element comes from a new generalized conforming Kirchhoff-Mindlin plate element TSL-T9, which is derived in this paper based on semiLoof constrains and rational shear interpolation. Thus the convergence can be guaranteed and no shear locking will happen. Furthermore, a simple hybrid procedure is suggested to improve the stress solutions, and the Updated Lagrangian formulae are also established for the geometrically nonlinear problems. Numerical results with solutions, which are solved by some other recent element models and the models in the commercial finite element software ABAQUS, are presented. They show that the proposed element, denoted as GMST18, exhibits excellent and better performance for the analysis of thin-think plates and shells in both linear and geometrically nonlinear problems.

• Neurospine
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• v.15 no.4
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• pp.368-375
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• 2018

Objective: To evaluate the results of operative management of subaxial spine injuries managed with 2-level anterior cervical corpectomy and fusion with a cervical locking plate and autologous bone-filled titanium mesh cage. Methods: This study included 23 patients with a subaxial spine injury who matched the inclusion criteria, underwent 2-level anterior cervical corpectomy and fusion at our institution between 2013 and 2016, and were followed up for neurological recovery, axial pain, fusion, pseudarthrosis, and implant failure. Results: According to Allen and Ferguson classification, there were 9 cases of distractive extension; 4 of compressive extension; 3 each of compressive flexion, vertical compression, and distractive flexion; and 1 of lateral flexion. Sixteen patients had a score of 6 on the Subaxial Injury Classification system, and the rest had a score of more than 6. The mean follow-up period was 19 months (range, 12-48 months). Neurological recovery was observed in most of the patients (78.21%). All patients experienced relief of axial pain. None of the patients received a blood transfusion. Twenty-one patients (91.3%) showed solid fusion and 2 (8.69%) showed possible pseudarthrosis, with no complications related to the cage or plate. Conclusion: Two-level anterior cervical corpectomy and fusion, along with stabilization with a cervical locking plate and autologous bone graft-filled titanium mesh cage, can be considered a feasible and safe method for treating specific subaxial spine injuries, with the benefits of high primary stability, anatomical reduction, and direct decompression of the spinal cord.

• Steel and Composite Structures
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• v.35 no.1
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• pp.129-145
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• 2020

In typical, structural topology optimization plays a significant role to both increase stiffness and save mass of structures in the resulting design. This study contributes to a new numerical approach of topologically optimal design of Mindlin-Reissner plates considering Winkler foundation and mathematical formulations of multi-directional variable thickness of the plate by using multi-materials. While achieving optimal multi-material topologies of the plate with multi-directional variable thickness, the weight information of structures in terms of effective utilization of the material at the appropriate thickness location may be provided for engineers and designers of structures. Besides, numerical techniques of the well-established mixed interpolation of tensorial components 4 element (MITC4) is utilized to overcome a well-known shear locking problem occurring to thin plate models. The well-founded mathematical formulation of topology optimization problem with variable thickness Mindlin-Reissner plate structures by using multiple materials is derived in detail as one of main achievements of this article. Numerical examples verify that variable thickness Mindlin-Reissner plates on Winkler foundation have a significant effect on topologically optimal multi-material design results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.2
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• pp.302-309
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• 2003

Hybrid-Trefftz plate bending elements are known to be robust and free of shear locking in the thin limit because of Internal displacements fields and linked boundary displacements. Also, their finite element approximation is very simple regardless to boundary shape since all element matrices can be calculated using only boundary integrals. In this study, new hybrid-Trefftz variational formulation based on the total potential energy principle of internal displacements and displacement consistency conditions at the boundary is derived. And flat shell elements are derived by combining hybrid-Trefftz bending stiffness and plane stress stiffness with drilling dofs.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.169-176
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• 2002

This paper is concerned with development of an enhanced quadratic Mindlin plate bending element. The behavior of the proposed plate element is further improved by the coupled use of non-conforming displacement modes, the selectively reduced integration scheme, and the assumed shear strain fields. The improvement may be attributable to the fact that the merits of these improvement techniques are merged in the formation of the new element in a complementary manner. The proposed quadratic finite element passes the patch tests, does not show spurious mechanism, and does not produce shear locking phenomena even with distorted meshes. It is shown that the element produces reliable solutions through numerical tests for standard benchmark problems. It is also noted that the element is applicable to transient dynamic analysis of Mindlin plates.

• Korean Journal of Optics and Photonics
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• v.15 no.5
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• pp.455-460
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• 2004

We have developed a mode-locked ultra-short pulse C $r^{4+}$:YAG laser, as well as a continuous wave C $r^{4+}$:YAG laser. The laser was pumped by a Nd:YAG laser and its characteristics were investigated. In continuous wave mode, we obtained as much as 600 mW at 1.436 ${\mu}{\textrm}{m}$ with pumping power of 6 W, by using an output coupler with a reflectivity of 98%. The power slope efficiency was 10%, when the gain medium was cooled to 19$^{\circ}C$. The tuning range was varied from 1.39 ${\mu}{\textrm}{m}$ to 1.55 ${\mu}{\textrm}{m}$ and the maximum power was 400 mW at 1.492 ${\mu}{\textrm}{m}$ with a 3-plate birefringent filter. The C $r^{4+}$:YAG laser was mode-locked by a Kerr lens mode locking method. Mode locking at 1.436 ${\mu}{\textrm}{m}$was initiated by slightly rocking a mirror mount. But the pulses were very unstable because of the strong water absorption at this region. So we shifted the lasing wavelength to 1.492 ${\mu}{\textrm}{m}$ by using a 3-plate birefringent filter. Then we obtained stable state mode-locking with the maximum average power of 280 mW for a pumping power of 6 W. The pulse width of 43 fs was measured using an autocorrelator and the repetition rate was 104.5 MHz.

• Structural Engineering and Mechanics
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• v.76 no.4
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• pp.435-449
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• 2020

This work presents the formulation of the isogeometric collocation method to solve the strong form equation of a unified and integrated approach of Reissner Mindlin plate theory (UI-RM). In this plate theory model, the total displacement is expressed in terms of bending and shear displacements. Rotations, curvatures, and shear strains are represented as the first, the second, and the third derivatives of the bending displacement, respectively. The proposed formulation is free from shear locking in the Kirchhoff limit and is equally applicable to thin and thick plates. The displacement field is approximated using the B-splines functions, and the strong form equation of the fourth-order is solved using the collocation approach. The convergence properties and accuracy are demonstrated with square plate problems of thin and thick plates with different boundary conditions. Two approaches are used for convergence tests, e.g., increasing the polynomial degree (NELT = 1×1 with p = 4, 5, 6, 7) and increasing the number of element (NELT = 1×1, 2×2, 3×3, 4×4 with p = 4) with the number of control variable (NCV) is used as a comparable equivalent variable. Compared with DKMQ element of a 64×64 mesh as the reference for all L/h, the problem analysis with isogeometric collocation on UI-RM plate theory exhibits satisfying results.