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Öğe Biomechanical evaluation of sagittal maxillary internal distraction osteogenesis in unilateral cleft lip and palate patient and noncleft patients A three-dimensional finite element analysis(E H Angle Education Research Foundation, Inc, 2014) Olmez, Sultan; Dogan, Servet; Pekedis, Mahmut; Yildiz, HasanObjective: To compare the pattern and amount of stress and displacement during maxillary sagittal distraction osteogenesis (DO) between a patient with unilateral cleft lip and palate (UCLP) and a noncleft patient. Materials and Methods: Three-dimensional finite element models for both skulls were constructed. Displacements of the surface landmarks and stress distributions in the circummaxillary sutures were analyzed after an anterior displacement of 6 mm was loaded to the elements where the inferior plates of the distractor were assumed to be fixed and were below the Le Fort I osteotomy line. Results: In sagittal plane, more forward movement was found on the noncleft side in the UCLP model (-6.401 mm on cleft side and -6.651 mm on noncleft side for the central incisor region). However, similar amounts of forward movement were seen in the control model. In the vertical plane, a clockwise rotation occurred in the UCLP model, whereas a counterclockwise rotation was seen in the control model. The mathematical UCLP model also showed higher stress values on the sutura nasomaxillaris, frontonasalis, and zygomatiomaxillaris on the cleft side than on the normal side. Conclusions: Not only did the sagittal distraction forces produce advancement forces at the intermaxillary sutures, but more stress was also present on the sutura nasomaxillaris, sutura frontonasalis, and sutura zygomaticomaxillaris on the cleft side than on the noncleft side.Öğe Biomechanics of the Femoral Head Cartilage and Subchondral Trabecular Bone in Osteoporotic and Osteopenic Fractures(Springer, 2021) Pekedis, Mahmut; Ozan, Firat; Yildiz, HasanThis study aimed to investigate the relationship between the micro structural properties of the subchondral trabecular bone (STB) and the macro mechanical properties of the articular cartilage (AC) in patients with osteoporotic (OP) and osteopenic (OPE) fractures. Sixteen femoral head samples (OP;OPE, n = 8 each) were obtained from female patients who underwent hip hemiarthroplasty. STB and AC specimens were harvested from those heads. Bone specimens were scanned using mu-CT to determine the micro structural properties. In-situ nondestructive compressive tests were performed for the cartilages to obtain elastic properties. The finite element technique was implemented on STB models created from mu-CT data to compute apparent elastic modulus. In addition, dynamic cyclic destructive tests were performed on STB and AC specimens to assess failure cycles. The results demonstrated that STB specimens in OPE group have more interconnected structure and higher cyclic dynamic strength than those in OP group. Furthermore, bone mineral density, failure cycle, and trabecular number of STB were positively correlated with the cartilage failure cycle, which indicates that STB alteration may affect the macroscopic mechanical properties of AC. The findings suggest that STB loss correlates with a decrease in cartilage strength and that improving of bone quality may prevent cartilage weakness.Öğe Buckling analysis of laminated composite circular plates with holes(Sage Publications Ltd, 2006) Baltaci, Aysun; Sarikanat, Mehmet; Yildiz, HasanIn this study, buckling analysis of laminated composite circular plates having circular holes and subjected to uniform radial load is investigated by using the finite element method. The effects of hole sizes, location of the holes, thickness variations and boundary conditions on the critical buckling load, and the buckling mode shapes of the composite plates are determined. Eight node isoparametric shell elements with 24 degrees of freedom are used during the investigation.Öğe Characterization of the mechanical properties of human parietal bones preserved in modified larssen solution, formalin and as fresh frozen(Springer France, 2021) Pekedis, Mahmut; Yoruk, Mustafa Deniz; Binboga, Erdal; Yildiz, Hasan; Bilge, Okan; Celik, ServetPurpose Although the fresh frozen (FF) cadaver is preferred for surgical applications, it is limited due to short usage time, unsuitable for reuse and the risk of infection. Due to its limited use, FF cadavers, which are covered by import in countries with insufficient body donation cause low-cost effectiveness. With the increase of real human tissue specimen necessities for surgical training, long-term preservation of the cadavers is crucial due to changes in mechanical properties. Therefore, studies on embalming solutions have increased in recent years. Methods We quantify the biomechanical properties of human parietal bones preserved via modified larssen solution (MLS) and compare the results with the specimens preserved as FF and fixed with 10% formalin-based solution (F10). The rectangular samples of 24 parietal bones of male individuals were resected from MLS-embalmed, F10-embalmed and FF cadavers to form three groups each containing eight samples. These specimens were tested longitudinally to identify mechanical properties. Results The tensile test results showed that there is not a significant difference between the groups in terms of stiffness, elastic modulus, strain at ultimate stress, failure strain and effective plastic strain. However, the yield stress, ultimate stress, yield strain, failure stress and total energy and post-yield properties are significantly lower in F10 than MLS and FF groups. Conclusion It is observed that the mechanical properties of MLS preserved and FF parietal bones have almost similar properties. Thus, it can be concluded that MLS is a suitable fixative solution for bone studies and bone-related surgical anatomy training applications.Öğe Characterization of the mechanical properties of human parietal bones preserved in modified larssen solution, formalin and as fresh frozen (May, 10.1007/s00276-021-02762-1, 2021) [Correction](Springer France, 2021) Pekedis, Mahmut; Yoruk, Mustafa Deniz; Binboga, Erdal; Yildiz, Hasan; Bilge, Okan; Celik, Servet[No Abstract Available]Öğe Chemical composition and nutritional value of a wild edible ectomycorrhizal mushroom, Tricholoma anatolicum(Tubitak Scientific & Technical Research Council Turkey, 2011) Kalmis, Erbil; Yildiz, Hasan; Ergonul, Bulent; Kalyoncu, Fatih; Solak, Mehmet HalilThe chemical composition and nutritional value of a wild edible ectomycorrhizal mushroom from southwestern Anatolia, Tricholoma anatolicum, were analyzed. Moisture, crude oil, protein, ash, total carbohydrate content, and mineral composition of the mushrooms studied, including Fe, Na, K, Zn, Cu, Ca, Cd, and Pb, were determined. The energy values of the samples were also calculated. The analyses were conducted during the 3 different growing stages of the mushrooms: mycelium, young fruiting bodies, and mature fruiting bodies. The highest values for moisture and crude oil contents were found to be in the mycelium, ash, and carbohydrate content of young fruiting bodies. In addition, Na content was found to be the highest in mycelium. The highest values for Fe were found in the young fruiting bodies, and K, Zn, Cu, and Ca were at their highest values in mature bodies. None of the samples contained heavy metals Cd or Pb.Öğe Color and lycopene content of tomato puree affected by electroplasmolysis(Taylor & Francis Inc, 2007) Yildiz, Hasan; Baysal, TanerTomato puree was produced using three different breaking methods, namely heating by steam injection, by electroplasmolysis, and combination of both steam injection and electroplasmolysis. In electroplasmolysis, the tomato pulp was treated at the electric field strength of 68 V/cm for 1.5 seconds. L, a, b, a/b, tomato color index, total color difference, chroma difference, hue angle, and lycopene content of purees were measured. Puree samples breaked by electroplasmolysis had better color values and the highest lycopene content. The a/b, tomato color index, and lycopene content of these samples were as 2.00; 49.94 and 273.9 mg/kg, respectively.Öğe Constitutive Modeling of Bovine Tendon(Ieee, 2017) Atakan, Burak; Dundar, Samim; Yildiz, HasanIn this study, tendons that holds skeletal and muscular system together are investigated with the help of hyperelastic material models and results of different material models are interpreted with the help of computer aided engineering programs. Axial forces are applied to bovine tendons in order to obtain stress-strain curve while doing constitutive modelling. After that, curve fitting methods are used to get the Mooney-Rivlin and Ogden constants. Constitutive model is formed by finite element model with the help of computer aided engineering programs and results of Mooney-Rivlin and Ogden models are examined.Öğe Continuous Atmospheric Plasma Oxidation of Carbon Fibres: Influence on the Fibre Surface and Bulk Properties and Adhesion to Polyamide 12(Springer, 2010) Erden, Seckin; Ho, Kingsley K. C.; Lamoriniere, Steven; Lee, Adam F.; Yildiz, Hasan; Bismarck, AlexanderContinuous atmospheric plasma oxidation (APO) was used to introduce oxygen functionalities to the surface of carbon fibres in an attempt to enhance interfacial adhesion between carbon fibres and polyamide-12 (PA-12). APO only affects the surface properties of the fibres while their bulk properties remained unchanged. Contact angle and zeta-potential measurements demonstrated that APO-treated fibres became significantly more hydrophilic due to the introduction of polar oxygen-containing groups on the fibre surface, which also resulted in an increase of surface energy on the carbon fibres. The interfacial shear strength of single carbon fibre/PA-12 model composites, determined by single fibre fragmentation tests, showed an increase from 40 to 83 MPa with up to 4 min of APO treatment time which confirms that the fibre/matrix interfacial adhesion was enhanced. This highlights that the incorporation of APO into composite manufacturing will allow tailoring of the fibre/matrix interface.Öğe Damage diagnosis of a laminated composite beam and plate via model based structural health monitoring techniques(Gazi Univ, Fac Engineering Architecture, 2016) Pekedis, Mahmut; Yildiz, HasanIn this study, model based damage identification algorithms were applied for a delaminated composite beam and plate. Initially, natural frequencies of healthy and delaminated beam were measured via experimental modal analysis. Next, the natural frequencies obtained by experimental method were verified with the finite element analysis. Once the validation has been fulfilled, the next step was to apply the finite element analysis to extract the mode shapes. Then, the curvatures mode shapes were obtained from the mode shapes, and these parameters were used in the gapped smooth method (GSM) and strain energy method (SEM) to detect the location and size of the delamination. The damage diagnosis technique for composite plate was evaluated for two cases. In the first case, it was assumed that the initial health information of a structure is known. However, the information of an undamaged structure may not be available during the diagnosis process for some circumstances. Therefore, the diagnosis was conducted by evaluating the curvatures of damaged structure using surface fit techniques in order to predict the initial status for the second case. Both of the two damage detection algorithms were evaluated for these two cases. The results show that, the delamination of laminated composite beam and plate could be predicted non-destructively by employing the data obtained from experimental or numerical technique in model based SHM approach for laboratory conditions.Öğe Damping effects of rubber layer in laminated composite circular plate during forced vibration(Springer, 2007) Baltaci, Aysun; Sarikanat, Mehmet; Yildiz, Hasan; Inan, E; Kiris, AIn this study, the effects of the location of the rubber between composite layers which is located to supply damping on the vibration frequency of laminated composite circular plates having different fiber directions are investigated by using the finite element method. The laminated composite circular plate having free outer edge is manufatured as having a central hole. Hybrid composite circular plate is clamped at the inner edge and subjected to transverse impuls load on a location at the outer edge. The best location of the rubber layer in terms of the damping capability are determined by using finite element analysis.Öğe Determination of the critical load and energy release rate in mode II delamination using a meshfree method(Walter De Gruyter Gmbh, 2014) Pekbey, Yeliz; Hesar, Goudarz Ghanizadeh; Yildiz, Hasan; Maleki, Farshid KhosraviSimulation of fracture by using numerical methods is important to treat geometries that change in time. In this study, both numerical and experimental investigations are presented for the delamination under mode II loading, detailing the derivation of the formulations in numerical simulations of fracture. The simulation of the delamination under mode II loading based on the cohesive segments model was investigated by using a mesh-free method. Then, an experimental investigation was used to verify the meshfree method's results. For tests under mode II loading, three-point end-notched flexure specimens, which are made of carbon/epoxy laminate (AS4/3501-6) which consists of 10 plies in [0](10) and [0/90/0/90/0](s) lay-up with delamination inserted in the middle of the laminate, were used for the interlaminar fracture toughness tests. The problem was solved for [0] 10, [0/45/-45/90/0](s), [0/90/0/90/0](s), [0/90/0/90/30](s), [0/90/0/90/45](s) and [0/90/0/90/60](s) laminates with midplane delaminations, and the results were verified for different composite materials. The critical fracture force, which can be experimentally measured, was used to calculate the mode II delamination fracture toughness of the carbon/epoxy laminate. In addition, values of the integral for 209 (11x19) and 253 (11x23) background meshes with equivalent interval sizes were compared. For a relatively fine background mesh, the critical load was converged. Results obtained from the meshfree element-free Galerkin method showed very good agreement with experimental data for single-mode delamination under mode II loading. The results presented will help in the implementation of mesh design techniques that protect numerical accuracy while minimizing computational expense.Öğe Determination of the effects of axial load on the natural frequency of a composite beam with the finite element method(Sage Publications Ltd, 2006) Sarikanat, Mehmet; Yildiz, Hasan; Baltaci, AysunThe effects of axial load on the natural frequency in simply supported thick composite beams are determined using the finite element method. The material properties of the elements are calculated with two different average value methods (arithmetic and weighted average) and the effects of axial load on the natural frequency of the beam are examined. A computer program is developed to analyze the effect of axial load on the natural frequency. The finite element method is used to determine the axial load effects on the natural frequency of a fiber reinforced composite beam. The results are obtained and compared with the analytical solutions by taking different element numbers in the thickness direction. With the help of these two methods, eight-node brick elements are used in multilayer finite element analyses. It has been observed that the results obtained by the arithmetic average method are quite close to the analytic results.Öğe Development and analysis of modular uniaxial leg adapter(Taylor & Francis Ltd, 2007) Dincel, Ozan; Gursel, K. Turgut; Yildiz, HasanThe adapters of modular prostheses are the structural components mostly likely to fail during the use of prostheses because of the high forces and moments occurring during the human gait. In this study, structural performance of a modular uniaxial leg adapter during gait is analysed utilizing computer software. By analysing the results, the relevant product was redesigned in order to prevent possible failures. Subsequently, the developed modular uniaxial leg adapter was tested in accordance with ISO 10328 in order to ensure the safety of the design. Further, the test results are compared with a finite element analysis to evaluate the performance of the numerical analysis.Öğe The effect of head trauma on fracture healing: biomechanical testing and finite element analysis(Turkish Assoc Orthopaedics Traumatology, 2010) Ozan, Firat; Yildiz, Hasan; Bora, Osman Arslan; Pekedis, Mahmut; Coskun, Gulnihal Ay; Gore, OyaObjectives: We aimed to evaluate the effect of head trauma on fracture healing with biomechanical testing, to compare the results obtained from a femur model created by finite element analysis with experimental data, and to develop a finite element model that can be employed in femoral fractures. Methods: Twenty-two Wistar albino rats were randomized into two groups. The control group was subjected to femoral fracture followed by intramedullary fixation, whereas the head trauma group was subjected to femoral fracture followed by intramedullary fixation along with closed blunt head trauma. Bone sections obtained with computed tomography from rat femurs were transferred into a computer and a 3D mathematical model of femur was created. At the end of week 4, femurs were examined by biomechanical testing and finite element analysis. Results: The mean maximum fracture load was significantly higher in the head trauma group than in control group (p < 0.05). Maximum strain values were also significantly high in the head trauma group (p < 0.05). There was no significant difference between the groups with regard to maximum deformation (p > 0.05). The head trauma group had significantly higher mean bending rigidity than the control group (p < 0.05). The head trauma group showed no significant difference from the control group in terms of strain energy and elasticity module (p > 0.05). There was no significant difference between experimental biomechanical test and finite element analysis (p > 0.05). Conclusion: Noninvasive methods such as finite element analysis are useful in examination of the mechanical structure of bones. Experimental biomechanical test and finite element analysis methods suggest that head trauma contributes to fracture healing.Öğe Effects of electrical pretreatment conditions on osmotic dehydration of apple slices: Experimental investigation and simulation(Elsevier Sci Ltd, 2016) Yildiz, Hasan; Icier, Filiz; Eroglu, Salih; Dagci, GamzeElectrical pretreatments at 9 different conditions consisting of the combination of 3 different voltage gradients (20, 27, and 32 V/cm) and 3 different application times (10, 20, and 30 s) were applied on apple slices. Apple slices were osmotically dehydrated in 50% sucrose solution at 40 degrees C until their total dry matter content (TDM) reached to 40%. The effect of pretreatment conditions on the change of water loss and solid gain during osmotic dehydration was investigated, and effective diffusion coefficients were determined. The time needed to reach up to 40% TDM content was predicted by using the numeric solution of unsteady state mass transfer equations and diffusion coefficients via MATLAB code written. The electrical pretreatments reduced the osmotic dehydration time by in the range of 26-64%. The final water and solid distributions of apple slices were simulated in ANSYS. Modeling and simulation results were in good agreement with experimental data (p < 0.05). Industrial relevance: Since the electrical pretreatment both shortens the osmotic dehydration time and increases the water removed per unit energy used, its application prior to osmotic dehydration processes in the commercial productions will be economical. The proposed modeling and simulation approach for assessment of the effects of electrical pretreatments on osmotic dehydration characteristics may provide valuable information on the scaling up of these conditions in the industrial scale systems. (C) 2016 Elsevier Ltd. All rights reserved.Öğe Finite element analysis of the Anterior Drawer Test for foot Ankle(Current Biology Ltd, 2011) Pekedis, Mahmut; Yildiz, HasanÖğe The finite element method-based pattern recognition approach for the classification of patient-specific gunshot injury(Sage Publications Ltd, 2022) Pekedis, Mahmut; Ozan, Firat; Koyuncu, Semmi; Yildiz, HasanViolence related injuries and deaths mostly caused by firearms are a major problem throughout the world. Understanding the factors that control the extent of hard-soft tissue wound patterns using computer imaging techniques, numerical methods, and machine learning algorithms may help physicians to diagnose and treat those injuries more properly. Here, we investigate the use of computational results coupled with the pattern recognition algorithms to develop an approach for forensic applications. Initially, computer tomography (CT) images of the patient whose leg was shot by a 9 x 19 parabellum bullet are used to construct the FE models of that patient's femoral bone and the surrounding soft tissues. Then, Hounsfield units-based material properties are assigned to elements of the bone. To simulate the full range of loading conditions encountered in ballistic events, a constitutive model that captures the strain-rate dependent response is implemented. The entrance pathway vector of the bullet is directed in accordance with the patient's wound and the simulations are deployed for the cases having various inlet velocities such as 150, 200, 250, 300, and 350 m/s. Once the FE results for each case are obtained, they are processed with supervised machine learning algorithms to classify the wound and inlet velocity correspondence. The results demonstrate that they can be diagnosed with a percent accuracy of 97.3, 97.5, and 98.3 for the decision tree (DT), k-nearest neighbors (kNN) and support vector machine (SVM) classifier, respectively. This approach may provide a useful framework in classifying the wound type, predicting the bullet impact velocity and its firing distance.Öğe Greater Trochanteric Fixation Using a Cable System for Partial Hip Arthroplasty: A Clinical and Finite Element Analysis(Hindawi Publishing Corporation, 2014) Ozan, Firat; Koyuncu, Semmi; Pekedis, Mahmut; Altay, Taskin; Yildiz, Hasan; Toker, GokhanThe aim of the study was to investigate the efficacy of greater trochanteric fixation using a multifilament cable to ensure abductor lever arm continuity in patients with a proximal femoral fracture undergoing partial hip arthroplasty. Mean age of the patients (12 men, 20 women) was 84.12 years. Mean follow-up was 13.06 months. Fixation of the dislocated greater trochanter with or without a cable following load application was assessed by finite element analysis (FEA). Radiological evaluation was based on the distance between the fracture and the union site. Harris hip score was used to evaluate final results: outcomes were excellent in 7 patients (21.8%), good in 17 patients (53.1%), average in 5 patients (15.6%), and poor in 1 patient (9.3%). Mean abduction angle was 20.21 degrees. Union was achieved in 14 patients (43.7%), fibrous union in 12 (37.5%), and no union in 6 (18.7%). FEA showed that the maximum total displacement of the greater trochanter decreased when the fractured bone was fixed with a cable. As the force applied to the cable increased, the displacement of the fractured trochanter decreased. This technique ensures continuity of the abductor lever arm in patients with a proximal femoral fracture who are undergoing partial hip arthroplasty surgery.Öğe In vivo investigation of calcium phosphate coatings on Ti6-Al-4V alloy substrates using lactic acid - sodium lactate buffered synthetic body fluid(Turkish Assoc Orthopaedics Traumatology, 2013) Havitcioglu, Hasan; Cecen, Berivan; Pasinli, Ahmet; Yuksel, Mithat; Aydin, Ibrahim; Yildiz, HasanObjective: The aim of this study was to evaluate the mode of failure and biomechanical characteristics of Ti-6Al-4V anchors biomimetically coated with calcium phosphate (CaP) for soft tissue fixation to bone in an animal model. Methods: The current study included 14 adult New Zealand white rabbits equally divided into two groups. Calcium phosphate-coated Ti-6Al-4V anchors were used in the test group and non-coated Ti-6Al-4V anchors in the control group. Anew approach was applied to synthesize the CaP coatings via the biomimetic growth in the Lac-SBF containing Ca2+ and PO43- ions, Na-lactate and lactic acid (HL). Titanium anchors were implanted into the right tibia, followed by biomechanical tensile strength tests. Histological studies were carried out after removal of anchors (bone-implant surface). Results: The CaP-coated Ti-6Al-4V anchors had significantly higher tensile strength (p=0.003) and displacement values (p=0.004) than the non-coated anchors. Control group scores were higher than those of the test group (14 and 9, respectively) in tensile strength tests. Conclusion: The new CaP coating can be used in orthopedic surgery as catalyzer to improve bone ingrowth. We believe that our research will form a model for further research on biomimetic coatings on Ti-6Al-4V substrates.
