Browsing by Author "Atas, A"
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Item Experimental investigation on low-velocity impact response of wood skinned sandwich composites with different core configurationsDemircioglu, TK; Balikoglu, F; Inala, O; Arslan, N; Ay, I; Atas, AIn this paper, an experimental investigation on the low-velocity impact response of wood skinned hybrid sandwich composites was presented. Several alternative design configurations were developed by using rubber-cork and E-glass composite layers between the foam core and wood skin in order to improve the impact performance of conventional sandwich composites. Low-velocity impact (LVI) testing was performed using a drop weight test machine at different impact energies and destructive cross-sectioning was performed to examine the interior damage growth and penetration depth of the specimens. The impact performance of the specimens was evaluated in terms of energy absorption capacity, maximum contact force and penetration depth. The multi-core design concept significantly improved the energy absorption capacity with a reduced extent of impact induced damage. The proportion of recyclable materials in each configuration and the energy absorption level per unit cost were also presented for the interest of product designers.Item Mechanical performance of marine sandwich composites subjected to flatwise compression and flexural loading: Effect of resin pinsBalikoglu, F; Demircioglu, TK; Yildiz, M; Arslan, N; Atas, AMechanical performance of marine sandwich panels comprising E-glass/vinyl ester face sheets and perforated poly-vinyl chloride foam core was evaluated and compared with conventional foam core sandwich panels. Circular holes through the foam core thickness were drilled with 12 different arrangements in square patterns and the holes were filled with the resin during the infusion process which created the through-the-thickness solid resin pins. The effect of each pattern on the flatwise compression and core shear properties of the sandwich panels were experimentally investigated. The three-point bending maximum failure load of perforated foam core sandwich panels was increased over 133.8% by increasing the diameter of the resin pins at the expense of increased panel weight up to 67%. The flatwise compression stress to induce core crushing was significantly increased by reinforcing the resin pins.Item Compression after low velocity impact tests of marine sandwich composites: Effect of intermediate wooden layersBalikoglu, F; Demircioglu, TK; Inal, O; Arslan, N; Atas, AIn the present work, compression after impact (CAI) behavior of sandwich composite materials with intermediate wooden layers was investigated. Sandwich panels were manufactured by using vacuum assisted resin transfer molding (VARTM) method with pinewood and ashwood intermediate layers. 15 and 25 mm thick PVC foams with a same density of 80 kg/m(3) were chosen in conjunction with the face sheets composed of non-crimp biaxial E-glass fabrics and bisphenol-A epoxy vinyl ester resin material system. Impact tests were performed under 30 J (low) and 60 J (high) energy levels with conical and hemispherical impactors. CAI tests were conducted in accordance with the ASTMC364/C364M-07 standard. Using pinewood and ashwood intermediate layers increased the residual CAI strength and decreased the depth of the impact damage. The intermediate wooden layers have also a potential to reduce the thickness of the composite face sheets and foam core which may increase the proportion of the recyclable wooden materials within the sandwich structure. (C) 2017 Elsevier Ltd. All rights reserved.Item Acoustic Characteristics of Turkish Speaking Children Ages between 4 and 14 Years OldAkmese, PP; Kayikci, MEK; Atas, APurpose: The present study aims to establish and characterize the pediatric acoustic values of native Turkish-speaking children and the relationship of those measures with physical characteristics like height and weight. Material and Methods: This study included 203 individuals aged between 4 to 14 years. Results: It was found that despite the slight variations in the voice parameters of 4-to-14-year old children who had normal development, the principal change started after 8 years of age in boys and 10 years of age in girls, the fundamental frequency started to decrease in both sexes after those ages. Male and female children showed statistically significant levels of differentiation in voice characteristics beginning as of 13 years of age. Discussion: It is considered that the normative data obtained from 4 to 14 years of age native Turkish speakers could be used to determine the voice disorders of children.Item Improving four-point bending performance of marine composite sandwich beams by core modificationBalikoglu, F; Arslan, N; Demircioglu, TK; Inal, O; Iren, M; Atas, AThe aim of this study was to improve four-point bending performance of foam core sandwich composite beams by applying various core machining configurations. Sandwich composites have been manufactured using perforated and grooved foam cores by vacuum-assisted resin transfer moulding method with vinyl-ester resin system. The influence of grooves and perforations on the mechanical performance of marine sandwich composite beams was investigated under four-point bending test considering the weight gain. Bending strength and effective bending stiffness increased up to 34% and 61%, respectively, in comparison to a control beam without core modification. Analytical equations were utilised for calculating the mid-span deflection, equivalent bending stiffness and ultimate bending strength of the sandwich beams. Finite element analysis was also performed to analyse the flexural response of the specimens taking into account the combined effect of orthotropic linear elasticity of the face sheet and the non-linear behaviour of the foam core.Item Anthropometric findings from birth to adulthood and their relation with karyotpye distribution in Turkish girls with Turner syndromeSari, E; Bereket, A; Yesilkaya, E; Bas, F; Bundak, R; Aydin, BK; Darcan, S; Dündar, B; Büyükinan, M; Kara, C; Adal, E; Akinci, A; Atabek, ME; Demirel, F; Çelik, N; Öakan, B; Özhan, B; Orbak, Z; Ersoy, B; Dogan, M; Atas, A; Turan, S; Göksen, D; Tarim, Ö; Yüksel, B; Ercan, O; Hatun, S; Simsek, E; Ökten, A; Abaci, A; Döneray, H; Özbek, MN; Keskin, M; Önal, H; Akyürek, N; Bulan, K; Tepe, D; Emeksiz, HC; Demir, K; Kizilay, D; Topaloglu, AK; Eren, E; Özen, S; Demirbilek, H; Abali, S; Akin, L; Eklioglu, BS; Kaba, S; Anik, A; Bas, S; Unuvar, T; Saglam, H; Bolu, S; Özgen, T; Dogan, D; Çakir, ED; Sen, Y; Andiran, N; Çizmecioglu, F; Evliyaoglu, O; Karagüzel, G; Pirgon, Ö; Çatli, G; Can, HD; Gürbüz, F; Binay, Ç; Bas, VN; Fidanci, K; Gül, D; Polat, A; Acikel, C; Cinaz, P; Darendeliler, FTo evaluate the anthropometric features of girls with Turner syndrome (TS) at birth and presentation and the effect of karyotype on these parameters. Data were collected from 842 patients with TS from 35 different centers, who were followed-up between 1984 and 2014 and whose diagnosis age ranged from birth to 18 years. Of the 842 patients, 122 girls who received growth hormone, estrogen or oxandrolone were excluded, and 720 girls were included in the study. In this cohort, the frequency of small for gestational age (SGA) birth was 33%. The frequency of SGA birth was 4.2% (2/48) in preterm and 36% (174/483) in term neonates (P<0.001). The mean birth length was 1.3cm shorter and mean birth weight was 0.36kg lower than that of the normal population. The mean age at diagnosis was 10.1 +/- 4.4 years. Mean height, weight and body mass index standard deviation scores at presentation were -3.1 +/- 1.7, -1.4 +/- 1.5, and 0.4 +/- 1.7, respectively. Patients with isochromosome Xq were significantly heavier than those with other karyotype groups (P=0.007). Age at presentation was negatively correlated and mid-parental height was positively correlated with height at presentation. Mid-parental height and age at presentation were the only parameters that were associated with height of children with TS. The frequency of SGA birth was found higher in preterm than term neonates but the mechanism could not be clarified. We found no effect of karyotype on height of girls with TS, whereas weight was greater in 46,X,i(Xq) and 45,X/46,X,i(Xq) karyotype groups. (c) 2016 Wiley Periodicals, Inc.Item Growth curves for Turkish Girls with Turner Syndrome: Results of the Turkish Turner Syndrome Study GroupDarendeliler, F; Yesilkaya, E; Bereket, A; Bas, F; Bundak, R; Sari, E; Aydin, BK; Darcan, S; Dündar, B; Büyükinan, M; Kara, C; Mazicioglu, MM; Adal, E; Akinci, A; Atabek, ME; Demirel, F; Çelik, N; Özkan, B; Özhan, B; Orbak, Z; Ersoy, B; Dogan, M; Atas, A; Turan, S; Göksen, D; Tarim, Ö; Yüksel, B; Ercan, O; Hatun, S; Simsek, E; Ökten, A; Abaci, A; Döneray, H; Özbek, MN; Keskin, M; Önal, H; Akyürek, N; Bulan, K; Tepe, D; Emeksiz, HC; Demir, K; Kizilay, D; Topaloglu, AK; Eren, E; Özen, S; Demirbilek, H; Abali, S; Akin, L; Eklioglu, BS; Kaba, S; Anik, A; Bas, S; Ünüvar, T; Saglam, H; Bolu, S; Özgen, T; Dogan, D; Çakir, ED; Sen, Y; Andiran, N; Çizmecioglu, F; Evliyaoglu, O; Karagüzel, G; Pirgon, Ö; Çatli, G; Can, HD; Gürbüz, F; Binay, Ç; Bas, VN; Saglam, C; Gül, D; Polat, A; Açikel, C; Cinaz, PObjective: Children with Turner syndrome (TS) have a specific growth pattern that is quite different from that of healthy children. Many countries have population-specific growth charts for TS. Considering national and ethnic differences, we undertook this multicenter collaborative study to construct growth charts and reference values for height, weight and body mass index (BMI) from 3 years of age to adulthood for spontaneous growth of Turkish girls with TS. Methods: Cross-sectional height and weight data of 842 patients with TS, younger than 18 years of age and before starting any therapy, were evaluated. Results: The data were processed to calculate the 3rd, 10th, 25th, 50th, 75th, 90th and 97th percentile values for defined ages and to construct growth curves for height-for-age, weight-for-age and BMI-for-age of girls with TS. The growth pattern of TS girls in this series resembled the growth pattern of TS girls in other reports, but there were differences in height between our series and the others. Conclusion: This study provides disease-specific growth charts for Turkish girls with TS. These disease-specific national growth charts will serve to improve the evaluation of growth and its management with growth-promoting therapeutic agents in TS patients.Item Turner Syndrome and Associated Problems in Turkish Children: A Multicenter StudyYesilkaya, E; Bereket, A; Darendeliler, F; Bas, F; Poyrazoglu, S; Aydin, BK; Darcan, S; Dündar, B; Büyükinan, M; Kara, C; Sari, E; Adal, E; Akinci, A; Atabek, ME; Demirel, F; Çelik, N; Özkan, B; Özhan, B; Orbak, Z; Ersoy, B; Dogan, M; Atas, A; Turan, S; Göksen, D; Tarim, Ö; Yüksel, B; Ercan, O; Hatun, S; Simsek, E; ÖOkten, A; Abaci, A; Döneray, H; Özbek, MN; Keskin, M; Önal, H; Akyürek, N; Bulan, K; Tepe, D; Emeksiz, HC; Demir, K; Kizilay, D; Topaloglu, AK; Eren, E; Özen, S; Abali, S; Akin, L; Eklioglu, BS; Kaba, S; Anik, A; Bas, S; Ünüvar, T; Saglam, H; Bolu, S; Özgen, T; Dogan, D; Çakir, ED; Sen, Y; Andiran, N; Çizmecioglu, F; Evliyaoglu, O; Karagüzel, G; Pirgon, Ö; Çatli, G; Can, HD; Gürbüz, F; Binay, C; Bas, VN; Fidanci, K; Polat, A; Gül, D; Açikel, C; Demirbilek, H; Cinaz, P; Bondy, CObjective: Turner syndrome (TS) is a chromosomal disorder caused by complete or partial X chromosome monosomy that manifests various clinical features depending on the karyotype and on the genetic background of affected girls. This study aimed to systematically investigate the key clinical features of TS in relationship to karyotype in a large pediatric Turkish patient population. Methods: Our retrospective study included 842 karyotype-proven TS patients aged 0-18 years who were evaluated in 35 different centers in Turkey in the years 2013-2014. Results: The most common karyotype was 45, X (50.7%), followed by 45, X/46, XX (10.8%), 46, X, i(Xq) (10.1%) and 45, X/46, X, i(Xq) (9.5%). Mean age at diagnosis was 10.2 +/- 4.4 years. The most common presenting complaints were short stature and delayed puberty. Among patients diagnosed before age one year, the ratio of karyotype 45, X was significantly higher than that of other karyotype groups. Cardiac defects (bicuspid aortic valve, coarctation of the aorta and aortic stenosis) were the most common congenital anomalies, occurring in 25% of the TS cases. This was followed by urinary system anomalies (horseshoe kidney, double collector duct system and renal rotation) detected in 16.3%. Hashimoto's thyroiditis was found in 11.1% of patients, gastrointestinal abnormalities in 8.9%, ear nose and throat problems in 22.6%, dermatologic problems in 21.8% and osteoporosis in 15.3%. Learning difficulties and/or psychosocial problems were encountered in 39.1%. Insulin resistance and impaired fasting glucose were detected in 3.4% and 2.2%, respectively. Dyslipidemia prevalence was 11.4%. Conclusion: This comprehensive study systematically evaluated the largest group of karyotype-proven TS girls to date. The karyotype distribution, congenital anomaly and comorbidity profile closely parallel that from other countries and support the need for close medical surveillance of these complex patients throughout their lifespan.