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51.
A three-dimensional buckling delamination problem for a rectangular sandwich plate made from elastic and viscoelastic materials is studied. It is supposed that the plate contains interface embedded rectangular cracks and that the edge-surfaces of these cracks have initial infinitesimal imperfections. The evolution of these initial imperfections with an external bi-axial compressed force (for the case where the materials of the layers of the plate are elastic) or with duration of time (for the case where the materials of the layers of the plate are viscoelastic) is investigated. The corresponding boundary value problem is formulated within the framework of the piecewise homogeneous body model with the use of three-dimensional geometrically nonlinear field equations of the theory of viscoelastic bodies. This problem is solved by employing boundary form perturbation techniques, Laplace transform and FEM. According to the initial imperfection criterion, the values of the critical parameters are determined. Numerical results on the critical force and critical time are presented and discussed. In particular, it is established that the values of the critical forces obtained for the buckling delamination around the rectangular embedded interface cracks are significantly greater than those obtained for the corresponding edge and band cracks. 相似文献
52.
53.
Sezen Tekin H. Gul Yaglioglu Ayhan Elmali Ulaş Kürüm Hülya Yanık Duygu Aydın Tekdaş Mahmut Durmuş Vefa Ahsen 《Materials Chemistry and Physics》2013
The nonlinear optical properties (NLO) of Pcs can be modified by substituting different metal atoms into the ring or altering peripheral and axial functionalities. In this study, nonlinear optical absorption properties of tetra-substituted gallium and indium phthalocyanine complexes both in solution and polymeric film have been investigated by open aperture Z-scan measurements with nanosecond pulses at 532 nm. All investigated compounds exhibited reverse saturable absorption for both solution and film experiments. The investigated compounds in the solution showed better nonlinear optical absorption properties than polymeric films. The observed nonlinear optical absorption differences depending on the aggregation are discussed using the ultrafast dynamics and decay processes of excited states found from femtosecond pump-probe spectroscopy with white light continuum experiments. 相似文献
54.
Aslı Yorulmaz Ender S. Poyrazoglu Mehmet Musa Ozcan Aziz Tekin 《European Journal of Lipid Science and Technology》2012,114(9):1083-1093
Phenolic compound distribution of Turkish olive cultivars and their matching olive oils together with the influence of growing region were investigated. One hundred and one samples of olives from 18 cultivars were collected during two crop years from west, south and south‐east regions of Turkey. The olives were processed to oils and both olive and olive oil samples were evaluated for their phenolic compound distribution. The results have shown that main phenolics of Turkish olives were tyrosol, oleuropein, p‐coumaric acid, verbascoside, luteolin 7‐O‐glucoside, rutin, trans cinnamic acid, luteolin, apigenin, cyanidin 3‐O‐glucoside and cyanidin 3‐O‐rutinoside. Oleuropein and trans cinnamic acid were present in higher amounts among all phenolics. Principal component analyses showed that the growing region did not have drastic effect on phenolic profile of olives. The major phenolic compounds of olive oils were tyrosol, syringic acid, p‐coumaric acid, luteolin‐7‐O‐glucoside, trans cinnamic acid, luteolin and apigenin. Luteolin is a predominant phenolic compound in almost all oil samples. Total phenol concentrations of Southeast Anatolian oils were found to be lower than those of the other regions. 相似文献
55.
Nalan Tekin Saadet Kayiran Beyaz Ali Kara Eyüp imek Farida Darkrim Lamari Gülbeden akmak Hasan Yüksel Güney 《Polymer Composites》2012,33(8):1255-1262
Single‐walled carbon nanotube (SWCNT) polyvinylimidazole (PVI) composites have been prepared by in situ emulsion polymerization. Dispersion of raw SWCNTs in the PVI matrix was improved by surface modification of the SWCNTs using nitric acid treatment and air oxidation. The carbonyl‐terminated SWCNTs were covalently bonded to PVI by in situ polymerization and the SWCNT/PVI composite was thus obtained. The morphological and structural characterizations of the surface‐functionalized SWCNTs and SWCNT/PVI composites were carried out by Fourier transform infrared spectroscopy, X‐ray diffraction, conductivity measurements, scanning, and transmission electron microscopy. Thermograms of the materials were determined by the differential scanning calorimetry technique. The characterization results indicate that PVI was covalently bonded to SWCNTs and a new material was then obtained. The functionalized SWCNTs showed homogenous dispersion in the composites, whereas purified SWCNT resulted in poor dispersion and nanotube agglomeration. SWCNT/PVI composites exhibited chemical stability enhancement in many common solvents. I–V curves of the samples exhibit an ohmic character. Conductivity values for pure SWCNTs, pure PVI and SWCNT/PVI composite were measured to be 3.47, 2.11 × 10−9, and 2.3 × 10−3 S/m, respectively. Because of resonance, a large dielectric constant is obtained for SWCNT/PVI composite, which is not observed for ordinary materials. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers 相似文献
56.
Pinar Kosekahya Mustafa Koc Kemal Tekin Murat Uzel Cemile Ucgul Atilgan Mehtap Caglayan Pelin Yilmazbas 《Contact lens & anterior eye》2017,40(5):311-317
Aim
To evaluate changes in the coordinates of the line of sight (LoS) and higher order aberrations (HOAs) of eyes with keratoconus, following corneal cross-linking (CXL).Methods
All patients (93 eyes) underwent detailed ophthalmologic examination and Pentacam HR measurements at baseline and at 3, 6, and 12 months after corneal CXL. LoS coordinates on the horizontal (x) and vertical (y) axes, vertical coma, vertical trefoil, spherical aberration, total root–mean square (RMS), and HOA-RMS values were recorded along with visual acuity and topographical parameters.Results
LoS significantly shifted to the nasal region after corneal CXL in both right and left eyes (p = 0.003 and p = 0.01, respectively). Horizontal axis values of both eyes significantly shifted to the temporal region at postoperative 6th months compared to the baseline measurements (p = 0.02 and p = 0.02, respectively) and remained the same between postoperative 6th months and 12th months (p = 1.00 and p = 0.97, respectively). Total-RMS, HOA-RMS, vertical coma, and spherical aberration values significantly improved after corneal CXL (p < 0.001, p = 0.02, p = 0.04, and p < 0.001, respectively). The improvements in HOAs were significant at postoperative 6th months compared to the baseline measurements (p = 0.003, p = 0.02, p < 0.001, and p = 0.003, respectively) while remained the same between postoperative 6th months and 12th months (p > 0.05 for all values). The changes in horizontal-axis coordinates in left eyes were significantly correlated with anterior elevation, anterior astigmatism, total-RMS and HOA-RMS changes (r2 = 0.20, p = 0.03; r2 = 0.35, p < 0.01; r2 = 0.50, p < 0.001 and r2 = 0.35, p = 0.004; respectively).Conclusions
LoS significantly shifted to the nasal region and HOAs improved after corneal CXL and these changes stabilized 6th months after corneal CXL. It would be more better to perform refractive surgery in crosslinked corneas at least 6th months after corneal CXL. 相似文献57.
Javier Montero-de-Paz Ion Oprea Vitaly Rymanov Sebastian Babiel Luis Enrique García-Muñoz Alvydas Lisauskas Matthias Hoefle Álvaro Jimenez Oleg Cojocari Daniel Segovia-Vargas Merih Palandöken Tolga Tekin Andreas Stöhr Guillermo Carpintero 《Journal of Infrared, Millimeter and Terahertz Waves》2013,34(3-4):251-266
The millimeter-wave spectrum above 70 GHz provides a cost-effective solution to increase the wireless communications data rates by increasing the carrier wave frequencies. We report on the development of two key components of a wireless transmission system, a high-speed photodiode (HS-PD) and a Schottky Barrier Diode (SBD). Both components operate uncooled, a key issue in the development of compact modules. On the transmitter side, an improved design of the HS-PD allows it to deliver an output RF power exceeding 0 dBm (1 mW). On the receiver side, we present the design process and achieved results on the development of a compact direct envelope detection receiver based on a quasi-optical SDB module. Different resonant (meander dipole) and broadband (Log-Spiral and Log-Periodic) planar antenna solutions are designed, matching the antenna and Schottky diode impedances at high frequency. Impedance matching at baseband is also provided by means of an impedance transition to a 50 Ohm output. From this comparison, we demonstrate the excellent performance of the broadband antennas over the entire E-band by setting up a short-range wireless link transmitting a 1 Gbps data signal. 相似文献
58.
Behic Mert Hakan Erinc Kubra Sahin Aziz Tekin 《Journal of the American Oil Chemists' Society》2013,90(1):17-26
In this study, two different groups of fat samples were prepared in a way that samples of each group had different trans fatty acid (TFA) composition but similar solid fat content (SFC). Samples of the first group (named group A) had TFA between 0.0 and 56.23 %, while the samples of the second group (group B) contained trans isomers ranging from 0.0 to 44.4 %. A polarized microscope was used to monitor the differences between the samples in terms of crystal size and crystal number during isothermal crystallization. In general, increasing TFA resulted in formation of larger crystals in a shorter time. Similar findings were also observed when small deformation time and frequency sweep experiments were conducted. A higher TFA content led to higher complex modulus values during isothermal crystallization. On the other hand, when the samples were stored at 4 °C for 48 h, the samples with the lower trans isomer had higher hardness values. 相似文献
59.
Factors affecting the electrical resistivity of soybean oil methyl ester (which is important in some industrial applications)
were investigated by the addition of polar constituents [free fatty acids (FFA), water, phospholipids, monoglyceride, sterol,
tocopherol, peroxides, and β-carotene] to aluminapurified soybean oil methyl ester (APSBOMe). Investigation of measuring conditions
showed that reproducible results were obtained when the potential was greater than 25 V, and the charging time was greater
than 10 s. The resistivity of APSBOMe increased logarithmically as temperature decreased linearly. FFA had little effect on
resistivity. Saturation with water lowered the resistivity of APSBOMe much more than that of alumina-purified soybean oil
(APSBO). Phospholipids reduced the resistivity significantly when added to dry ester, but the addition of water affected the
resistivity of the samples containing phospholipids only slightly. Monoglyceride, sterol, tocopherol, and hydroperoxide affected
the resistivity of dry methyl ester similarly, but only monoglyceride showed a significant synergistic effect with water.
Diacylperoxide and β-carotene had little effect on the resistivity of the ester. 相似文献
60.
Nasim Jalilnejad Falizi Tülay Güngren Madenolu Mithat Yüksel Nalan Kabay 《国际能源研究杂志》2019,43(6):2188-2199
In this study, a strong acidic‐type cation exchange resin was used in the transesterification of corn oil to fatty acid methyl esters (FAME). The gel‐type cation exchange resin (Purolite‐PD206) was used in H+ and Na+ forms to utilize ion‐exchange resin as effective heterogeneous catalyst in the production of biodiesel. Effect of ionic forms of ion exchange resin on free fatty acid (FFA) conversion and composition was investigated by using different amounts of ion exchange resin (12, 16, and 20 wt%), various mole ratios of methanol to oil (1:6, 1:12, and 1:18 mol/mol), reaction temperatures (63, 65, and 67°C), and reaction time (24, 36, and 48 h) during transesterification reaction. The highest FFA conversions of 73.5% and 79.45% were obtained at conditions of 20 wt% of catalyst, 65°C of reaction temperature, 18:1 as methanol to oil ratio, and 48 h of reaction time for H+ and Na+ forms of ion exchange resin, respectively. These results were obtained from regression equations established by using analysis of variance (ANOVA) model according to the experimental results of selected parameters. Gas chromatography analysis revealed that FAME is mainly composed of C16:0 (palmitic), C18:1 (oleic), and C18:2 (linoleic) acids of methyl ester. 相似文献