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71.
Şenol Durmuşoğlu İbrahim Uslu Tuncay Tunç Selda Keskin Arda Aytimur Ahmet Akdemir 《Journal of Polymer Research》2011,18(6):1999-2004
Boron doped poly(vinyl) alcohol/ bismuth - lanthanum acetate (PVA/Bi-La) nanofibers were prepared by electrospinning using
PVA as a precursor. The effect of boron doping was investigated in terms of solution properties, morphological changes and
thermal characteristics. The fibers were characterized by FT-IR, XRD, SEM and BET. The addition of boron did not only increase
the thermal stability of the fibers, but also their diameters, which yielded stronger fibers. XRD analyses showed that boron
doping increased the peak intensities and indicated that the boron doping enhanced the crystallite size. Moreover, no shifts
were noticed in diffraction angles for boron doped and undoped samples. Therefore, boron doping did not significantly alter
the lattice spacing. The SEM micrograph of the fibers showed that the addition of boron resulted in the formation of cross
linked bright surfaced fibers. Also, grain diameters of boron doped and undoped nanocrystalline sintered powders were measured
as 170 nm and 120 nm respectively. The BET results show that boron undoped and doped Bi2O3-La2O3 nanocrystalline powder ceramic structures sintered at 800 °C have surface areas of 20.44 m2/g and 12.93 m2/g, respectively. 相似文献
72.
Tuncay Tunç Şemsettin Altındal İlbilge Dökme Habibe Uslu 《Journal of Electronic Materials》2011,40(2):157-164
In this study, the temperature-dependent mean density of interface states (NSS)(N_{\rm SS}) and series resistance (RS)(R_{\rm S}) profiles of Au/PVA (Ni,Zn-doped)/n-Si(111) structures are determined using current–voltage (I−V) and admittance spectroscopy [capacitance–voltage (C–V) and conductance–voltage G/ω–V] methods. The other main electronic parameters such as zero-bias barrier height (FB0)(\Phi_{{\rm B}0}), ideality factor (n), and doping concentration (N
D) are also obtained as a function of temperature. Experimental results show that the values of FB0\Phi_{\rm{B}0}, n, R
S, and N
SS are strongly temperature dependent. The values of FB0\Phi_{\rm{B}0} and R
S increase with increasing temperature, while those of n and N
SS decrease. The C–V plots of Au/PVA (Ni,Zn-doped)/n-Si(111) structures exhibit anomalous peaks in forward bias (depletion region) at each temperature, and peak positions shift
towards negative bias with increasing temperature. The peak value of C has been found to be strongly dependent on N
SS, R
S, and temperature. The experimental data confirm that the values of N
SS, R
S, temperature, and the thickness and composition of the interfacial polymer layer are important factors that influence the
main electrical parameters of the device. 相似文献
73.
Tuncay Tunç ?emsettin Altindal ?brahim Uslu ?lbilge Dökme Habibe Uslu 《Materials Science in Semiconductor Processing》2011,14(2):139-145
Current–voltage (I–V) characteristics of Au/PVA/n-Si (1 1 1) Schottky barrier diodes (SBDs) have been investigated in the temperature range 80–400 K. Here, polyvinyl alcohol (PVA) has been used as interfacial layer between metal and semiconductor layers. The zero-bias barrier height (ΦB0) and ideality factor (n) determined from the forward bias I–V characteristics were found strongly dependent on temperature. The forward bias semi-logarithmic I–V curves for different temperatures have an almost common cross-point at a certain bias voltage. The values of ΦB0 increase with the increasing temperature whereas those of n decrease. Therefore, we have attempted to draw ΦB0 vs. q/2kT plot in order to obtain evidence of a Gaussian distribution (GD) of the barrier heights (BHs). The mean value of BH and standard deviation (σ0) were found to be 0.974 eV and 0.101 V from this plot, respectively. Thus, the slope and intercept of modified vs. q/kT plot give the values of and Richardson constant (A?) as 0.966 eV and 118.75 A/cm2K2, respectively, without using the temperature coefficient of the BH. This value of A* 118.75 A/cm2K2 is very close to the theoretical value of 120 A/cm2K2 for n-type Si. Hence, it has been concluded that the temperature dependence of the forward I–V characteristics of Au/PVA/n-Si (1 1 1) SBDs can be successfully explained on the basis of the Thermionic Emission (TE) theory with a GD of the BHs at Au/n-Si interface. 相似文献
74.
B. Dogan-Topal Dilek Kul Sibel A. Ozkan B. Uslu 《Journal of Applied Electrochemistry》2011,41(11):1253-1260
The electrochemical oxidation of fulvestrant was made on highly boron-doped diamond electrode using differential pulse adsorptive
stripping voltammetry. The highest current intensities were obtained by applying +1.10 V during 150 s for boron-doped diamond
electrode. For boron-doped diamond electrode, linear responses were obtained for the concentrations between 1 × 10−6 and 8 × 10−5 M in standard samples and between 1 × 10−6 and 4 × 10−5 M in serum samples. The repeatability of the method was 0.55 RSD% for differential pulse adsorptive stripping voltammetry.
The analytical values of the method are demonstrated by quantitative determination of fulvestrant in pharmaceutical formulations
and human serum, without the need for separation or complex sample preparation, since there was no interference from the excipients
and endogenous substances. Selectivity, reproducibility, and accuracy of the developed methods were demonstrated by recovery
studies. 相似文献
75.
76.
77.
Ethanol has been considered as an alternative fuel for diesel engines. On the other hand, injection timing is a major parameter that sensitively affects the engine performance and emissions. Therefore, in this study, the influence of advanced injection timing on the engine performance and exhaust emissions of a single cylinder, naturally aspirated, four stroke, direct injection diesel engine has been experimentally investigated when using ethanol‐blended diesel fuel from 0 to 15% with an increment of 5%. The original injection timing of the engine is 27° crank angle (CA) before top dead center (BTDC). The tests were conducted at three different injection timings (27, 30 and 33° CA BTDC) for 30 Nm constant load at 1800 rpm. The experimental results showed that brake‐specific energy consumption (BSEC), brake‐specific fuel consumption (BSFC), NOx and CO2 emissions increased as brake‐thermal efficiency (BTE), smoke, CO and HC emissions decreased with increasing amount of ethanol in the fuel mixture. Comparing the results with those of original injection timing, NOx emissions increased and smoke, HC and CO emissions decreased for all test fuels at the advanced injection timings. For BSEC, BSFC and BTE, advanced injection timings gave negative results for all test conditions. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
78.
79.
Ertan Durmusoglu M. Yavuz Corapcioglu Kagan Tuncay 《Canadian Metallurgical Quarterly》2006,6(4):269-278
Municipal solid waste (MSW) landfills are not only used to dispose the refuse in most economical way but also utilized as a viable land in today’s waste management strategy. Settlement prediction is an important issue in order to guarantee the integrity of any postclosure structure on landfills. In this study, landfill settlement in saturated and unsaturated landfills is investigated by developing a one-dimensional mathematical model and performing numerical experiments. Under the saturated conditions, the landfill is considered to be completely liquid saturated by preventing gas generation at all times. On the other hand, for the unsaturated case, we assume that a gas mixture comprised of methane and carbon dioxide is generated as a result of microbial decomposition of MSW deposited. The gas generation is assumed to follow a first-order kinetic approach. The liquid phase and gas mixture are considered compressible as well as the solid matrix (landfill body). After the governing equations were discretized using the Galerkin finite-element method, the Gaussian elimination technique is employed for a solution. In saturated landfills, the settlement is mainly caused by the overburden weight of the waste deposited. Further, the mass loss due to waste decomposition contributes for an additional settlement in unsaturated landfills. The predicted settlements are within the range reported in the literature. The model developed can simulate porosity, pressures, saturations, and stress profiles in settling landfills as well as to predict the transient and ultimate settlements in saturated and unsaturated landfills. 相似文献
80.
Abacavir (I), a drug used in the treatment of HIV, is electrochemically reduced at the dropping mercury electrode in a four-electron process, similar to structurally related adenine (III) and adenosine triphosphate (IV). To undergo the reduction, the species is protonated in the vicinity of the electrode. The protonations take place on the 6-amino group and on one of the pyrimidine ring nitrogens. The role of covalent hydration of the pyrymidine ring has been interpreted. Best suited as supporting electrolytes for analytical purposes are solutions of 0.1-1.0 M sulfuric, perchloric, or hydrochloric acids. Procedures of analyses of tablets containing I were established and validated, based on peak currents obtained by linear sweep, differential pulse, or square-wave voltammetry with a hanging mercury drop electrode as indicator electrode. The procedure proved to be more sensitive and more reliable than that based on oxidation on a glassy carbon electrode, proposed previously. 相似文献