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141.
Parviz Holakooei Ferruccio Carlo Petrucci Renzo Tassinari Carmela Vaccaro 《X射线光谱测定》2013,42(2):105-115
An outstanding style of Persian tilework, which emerged from the north‐eastern Iran in the 15th century, was extensively used for decorating architectural facades during the Safavid period (from the 16th through the 18th century). This type of tilework, the so‐called haft rang, technically comprises of forming a clay body and firing two glazed layers on top of the body. In the present paper, the first analytical data concerning haft rang tiles is provided. To do so, forty three samples of Safavid haft rang bodies were analysed by wavelength dispersive x‐ray fluorescence (WDXRF) and the obtained data were handled by principal component analysis (PCA). The results showed that the 17th century haft rang tiles wherever found are local products; that is, Safavid tile‐makers have used local clay sources to make the bodies of haft rang tiles. The analytical data also showed that old tileworks, in general sense, can be simply replaced by newly manufactured tiles or, at least, all tilework revetments in an individual edifice might not have been produced in an identical workshop. Moreover, WDXRF was used as an accurate and precise method to determine the chemical composition and to support compositional classification in provenance studies and can be considered as a reliable alternative for studying the provenance of archaeological ceramics. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
142.
143.
A novel carbon nanotube field effect transistor with symmetric graded double halo channel (GDH–CNTFET) is presented for suppressing band to band tunneling and improving the device performance. GDH structure includes two symmetric graded haloes which are broadened throughout the channel. The doping concentration of GDH channel is at maximum level at drain/source side and is reduced gradually toward zero at the middle of channel. The doping distribution at source side of channel reduces the drain induced barrier lowering (DIBL) and the drain side suppresses the band to band tunneling effect. In addition, broadening the doping throughout the channel increases the recombination of electrons and holes and acts as an additional factor for improving the band to band tunneling. Simulation results show that applying this structure on CNTFET enhances the device performance. In comparison with double halo structure with equal saturation current, the proposed GDH structure shows better characteristics and short channel parameters. Furthermore, the delay and power delay product (PDP) analysis versus on/off current ratio shows the efficiency of the proposed GDH structure. 相似文献
144.
At nanometer regime, fabricating the structures with non-overlapped channel and abrupt doping profile is very complicated and sometimes impossible. So, the resultant device experiences some non-ideal effects which have to be predicted and well addressed by simulation before fabrication. In this paper the effects of overlap between gate and source/drain regions on the performance of carbon nanotube field effect transistors have been investigated. The overlapped structure has been simulated with various doping profiles at drain/source and gate region junction tip. The device performance has been investigated in terms of ON current, Off current, ON/Off current ratio, subthreshold swing, delay, and power delay product (PDP). Simulations show that depending on the variations in the effective channel length, the overlap deteriorates some device characteristics and enhances the others. Where the effective channel length decreases (increases), the overlap deteriorates (enhances) the current ratio and subthreshold swing but enhances (deteriorates) the delay and PDP compared to non-overlapped structure. Furthermore, the overlapped structure with graded profile results in lower current ratio and higher subthreshold swing compared to overlapped structure with abrupt profile. At a fixed current ratio, the delay and PDP of overlapped structure with graded profile are more than overlapped structure with abrupt profile but at a fixed channel length, both profiles have approximately equal delay and PDP. 相似文献
145.
The method of manufactured solutions (MMS) is used to verify the convergence properties of a low-Mach number, variable-density flow code. Three MMS problems relevant to combustion applications are presented and tested on a variety of structured and unstructured grids. Several issues are investigated, including the use of tabulated state properties (i.e., density) and the effect of sub-iterations in the time-advancement method. The MMS implementations provide a quantitative framework to evaluate the impact of these practices on the code’s convergence and order-of-accuracy. Simulation results show that linear interpolation of the equation-of-state causes numerical fluctuations that impede convergence and reduce accuracy. Likewise, the sub-iterative time-advancement scheme requires a significant number of outer iterations to subdue splitting errors in highly nonlinear combustion problems. These findings highlight the importance of careful code and solution verification in the simulation of variable-density flows. 相似文献
146.
Foroutan-Nejad C Badri Z Shahbazian S Rashidi-Ranjbar P 《The journal of physical chemistry. A》2011,115(45):12708-12714
The electron density versus NICS(zz) (the out-of-plane component of nucleus-independent chemical shifts (NICS)) scan for assessing magnetic aromaticity among similar molecules with different ring sizes is improved by scanning the Laplacian of electron density versus NICS(zz) to include molecules containing different types of atoms. It is demonstrated that the new approach not only reproduces the results of the previous method but also surpasses that in the case of species with different atom types. The relative positions of curves in the plots of the Laplacian of electron density versus NICS(zz) correlate well with the ring current intensities of these molecules both near and far from the ring planes of the considered molecules. Accordingly, relative magnetic aromaticity of a number of planar hydrocarbons and a group of double aromatic metallic/semimetallic species are studied and discussed. 相似文献
147.
The aim of this paper is to present an efficient numerical procedure for solving the two-dimensional nonlinear Volterra integro-differential
equations (2-DNVIDE) by two-dimensional differential transform method (2-DDTM). The technique that we used is the differential
transform method, which is based on Taylor series expansion. Using the differential transform, 2-DNVIDE can be transformed
to algebraic equations, and the resulting algebraic equations are called iterative equations. New theorems for the transformation
of integrals and partial differential equations are introduced and proved. The reliability and efficiency of the proposed
scheme are demonstrated by some numerical experiments. 相似文献
148.
Application of a nanostructured sensor based on graphene‐ and ethyl 2‐(4‐ferrocenyl[1,2,3]triazol‐1‐yl)acetate‐modified carbon paste electrode for determination of methyldopa in the presence of phenylephrine and guaifenesin 下载免费PDF全文
Hadi Beitollahi Kaveh Movlaee Mohammad Reza Ganjali Parviz Norouzi Rahman Hosseinzadeh 《应用有机金属化学》2018,32(4)
We introduce a new method to determine methyldopa without the interference of phenylephrine and guaifenesin. For this purpose, a carbon paste electrode was modified with graphene and ethyl 2‐(4‐ferrocenyl[1,2,3]triazol‐1‐yl)acetate. According to electrochemical studies, oxidation current of methyldopa on the surface of the modified electrode increased and shifted towards negative potentials. This modified electrode demonstrated two linear ranges of 0.4–30.0 μM and 30.0–500.0 μM with a detection limit of 0.08 μM. No change was observed in the sensitivity of the modified electrode towards methyldopa in the presence of phenylephrine and guaifenesin, which enables the simultaneous or independent measurement of the three moieties. The efficiency of the proposed modified electrode was evaluated through the determination of these substances in real samples. 相似文献
149.
Mehdi Asadi Mostafa Ebrahimi Mohammad Mahdavi Mina Saeedi Parviz Rashidi Ranjbar Farshad Yazdani 《合成通讯》2013,43(17):2385-2392
Heating a mixture of isatoic anhydride, amines, and N,N′-dialkyl carbodiimides under solvent-free conditions provided novel 3-alkyl-2-(alkylamino)quinazolin-4(3H)-one derivatives for the first time. The products were obtained in moderate to good yields without formation of any by-products. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file. 相似文献
150.