Umut Topal

Reverse-flow submental artery flap for periorbital soft tissue and socket reconstruction

The submental artery island flap is a recently described local flap that may be used for reconstruction of the lower and middle thirds of the face and oral cavity. The reverse‐flow manner of the flap has been used in limited cases because of possible drawbacks such as venous congestion. We present our experience with the use of reverse‐flow submental artery flap and describe the surgical technique.

Effect of Amniotic Fluid on Peri-implant Capsular Formation

Although commonly used biomaterials are physically and chemically stable, nonimmunogenic, and nontoxic, implanted and blood-contact biomaterials trigger a wide variety of unwanted responses, including inflammation, thrombosis, infection, and fibrosis. Peri-implant fibrosis is the response most commonly seen by plastic surgeons. In this study, the authors hypothesized that as hyaluronic acid (HA) reduces scar formation by inhibiting the activity of mononuclear phagocytes and lymphocytes, human amniotic fluid (HAF), which contains high concentrations of HA, HA-stimulating activator (HASA), and other factors, might prevent the formation of fibrous capsules and capsule contracture when applied intraluminally. Two 1 x 1-cm silicone blocks were placed dorsally into separate surgically created pockets underneath the panniculus carnosus muscle, distant from the incisions, in each of the 10 rats in the study. At the time of implant insertion, 2 ml of HAF was instilled into the cranially located pockets in group 1, whereas 2 ml of saline solution was instilled into the caudally located pockets in group 2. After 6 months, intracapsular static and dynamic pressure measurements were made, and then all the peri-implant capsules were excised and fixed in 10% neutral buffered formaldehyde. The thicknesses of the capsules were measured in three different areas of each section, and a mean was calculated. Capsular firmness, according to the static and dynamic pressure readings, was significantly greater in the control group, which had saline solution introduced into the pocket, than in the treatment group, which had HAF used in the same manner. The mean total thickness of the capsules surrounding the implants was 876.7 μm in the control group, as comparied with 466.8 μm in the HAF-treated group. This difference was statistically significant (p < 0.001). Because of its ability to reduce capsular thickness and firmness and also because it can be stored in a freezer if it is prepared in a cell-free manner, HAF would appear to be a useful adjunct in the prevention of capsular contracture formation.

Strength Optimization of Laminated Composite Plates

A procedure to select the optimum fiber orientations and determine the maximum load-bearing capacity of the simply supported symmetrically laminated plates combined the bidirectional tension loads and bending moments is described. The fiber orientation is considered a design variable. The optimization problem consists of two stages. The objective of the first stage is to maximize the strength of the laminated plates by determining the fiber orientations optimally while the objective of the second stage is to maximize each of the bidirectional tension loads and bending moments subject to the Tsai—Wu failure criterion for the optimum fiber orientations obtained from the first stage. The modified feasible direction method (MFD) is used as an optimization procedure. Therefore, a FORTRAN program is used for the finite element analysis and optimization routine. Also, the optimum fiber orientations are obtained using the golden section (GS) method to compare the results. Finally, the effect of the different plate aspect ratio, width-to thickness ratio, the uncertainties in the material properties and the uncertainties in the fiber orientations on the optimum results is investigated and the results are compared.

Frequency optimization of laminated composite plates with different intermediate line supports

Abstract This paper deals with frequency optimization of symmetrically laminated 4-layered angle-ply plates with one or two different intermediate line supports. The design objective is the maximization of the fundamental frequency and the design variable is the fiber orientation in the layers. The first order shear deformation theory and nine-node isoparametric finite element model are used for finding the natural frequencies of laminates. The modified feasible direction method is used for the optimization routine. For this purpose, a program based on FORTRAN is used. Finally, the numerical analysis is carried out to investigate the effects of location of the internal line supports, plate aspect ratios and boundary conditions on the optimal designs and the results are compared.

Frequency optimization of laminated composite annular sector plates

This paper deals with frequency optimization of symmetrically laminated angle-ply annular sector plates. The design objective is the maximization of the fundamental frequency and the design variable is the fiber orientation in the layers. The first order shear deformation theory is used for the finite element solution of laminates. Nine-node Lagrangian rectangular plate element which have five degrees of freedom per node is used for the finite element solution of the laminated annular sector plates. The modified feasible direction method is used for the optimization routine. For this purpose, a program based on FORTRAN is used. The numerical analysis is carried out to investigate the effects of annularity, boundary conditions and sector angle on the optimal designs and the results are shown in tabular and graphical forms. Finally, the obtained results are compared. It can be shown that the parameters have a key role on the optimum design of laminated annular sector plates.

Frequency optimization of laminated composite spherical shells

Abstract This paper deals with frequency optimization of symmetrically laminated angle-ply spherical shells. The design objective is the maximization of the fundamental frequency, and the design variable is the fiber orientation in the layers. The first-order shear deformation theory and nine-node isoparametric finite element model are used for the finite element solution of the laminates. The modified feasible direction (MFD) method is used for the optimization routine. For this purpose, a program based on FORTRAN is used. Finally, the numerical analysis is carried out to investigate the effects of geometrical parameters and boundary conditions on the optimal designs, and the results are compared.

FREE VIBRATION ANALYSIS OF LAMINATED PLATES USING FIRST-ORDER SHEAR DEFORMATION THEORY

This paper deals with free vibration analysis of simply supported laminated composite plates using first-order shear deformation theory (FSDT). The displacement field of a laminated composite plate is given for FSDT. The numerical studies are conducted to determine the effect of width-to-thickness ratio, degree of orthotropy, fiber orientation, aspect ratio on the nondimension- alized fundamental frequency for laminated composite plates. Also, the effect of shear deformation, rotatory inertia and shear correction coefficient on the nondimensionalized fundamental frequency is examined. A MATLAB code is written for free vibration of laminated plates. However, the problem is modeled using finite element package program ANSYS for different meshes. Finally, the results are given in graphical and tabular form and compared.

Thermal buckling load optimization of laminated folded composite plates

Abstract In this study, thermal buckling load optimization of symmetrically laminated composite folded plates subjected to uniformly distributed temperature load is investigated. The objective function is to maximize the critical temperature capacity of laminates and the fiber orientation is considered as a design variable. The first-order shear deformation theory is used to study thermal buckling response of the laminates. The modified feasible direction method is used as the optimization routine. For this purpose, a program based on Fortran is used for the optimization. Finally, the significant effects of crank angles, plate lengths and boundary conditions on the optimum results are demonstrated and the results are compared.

Frequency optimization of laminated skewed open cylindrical shells

Abstract This paper deals with frequency optimization of symmetrically laminated skewed open cylindrical shells. The design objective is the maximization of the fundamental frequency and the design variable is the fiber orientations. The first-order shear deformation theory (FSDT) is used for the finite element solution of the shells. The modified feasible direction (MFD) method is used for the optimization routine. For this purpose, a program based on FORTRAN is used. Finally, the numerical analysis is carried out to investigate the effect of skew angles, length to radius ratios, subtended angle and boundary conditions on, the optimal designs and the results are compared.

Thermal buckling load optimization of laminated general quadrilateral and trapezoidal thin plates

Abstract This paper deals with thermal buckling load optimization of symmetrically laminated angle-ply general quadrilateral and trapezoidal thin plates. The objective function is to maximize the critical temperature capacity of the quadrilateral and trapezoidal laminated plates and the fiber orientation is considered as a design variable. The mathematical formulation is based on the classical laminated plate theory for the frequency analysis. The modified feasible direction method is used as the optimization routine. Therefore, a program based on FORTRAN is used. Finally, the significant effects of aspect ratios, boundary conditions, taper ratios and unsymmetric trapezoidal plates on the optimal results are investigated and the results are compared.