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排序方式: 共有1311条查询结果,搜索用时 15 毫秒
91.
S.K. Arora Vipul Patel R.G. Patel Brijesh Amin Anjana Kothari 《Journal of Physics and Chemistry of Solids》2004,65(5):965-973
The a.c. and d.c. conductivity of SrC4H4O6·3H2O are measured and are found to lie between usual conductivities of semiconductor and insulator. Temperature dependence of d.c. conductivity shows intrinsic conduction, which is confirmed by the slope of versus data. Due to application of thermal energy, noticeable conductivity peaks imply liberation of water molecules during dehydration and the formation of strontium oxalate. The conductivity plot has a nature similar to the intrinsic-to-extrinsic transition found in normal semiconductors. There occurs Efros hopping conduction in our samples. 相似文献
92.
93.
Il'ichev E Grajcar M Hlubina R IJsselsteijn RP Hoenig HE Meyer HG Golubov A Amin MH Zagoskin AM Omelyanchouk AN Kupriyanov MY 《Physical review letters》2001,86(23):5369-5372
We have measured the current-phase relationship I(varphi) of symmetric 45 degrees YBa2Cu3O7-x grain boundary Josephson junctions. Substantial deviations of the Josephson current from conventional tunnel-junction behavior have been observed: (i) The critical current exhibits, as a function of temperature T, a local minimum at a temperature T*. (ii) At T approximately T*, the first harmonic of I(phi) changes sign. (iii) For T相似文献
94.
A method for inverting the Laplace transform is presented, using a finite series of the classical Legendre polynomials. The
method recovers a real valued function f(t) in a finite interval of the positive real axis when f(t) belongs to a certain
class
and requires the knowledge of its Laplace transform F(s) only at a finite number of discrete points on the real axis s>0.
The choice of these points will be carefully considered so as to improve the approximation error as well as to minimize the
number of steps needed in the evaluations. The method is tested on few examples, with particular emphasis on the estimation
of the error bounds involved. 相似文献
95.
I.H. Gul A.Z. AbbasiF. Amin M. Anis-ur-RehmanA. Maqsood 《Journal of magnetism and magnetic materials》2007
Nanoparticles of Co1−xZnxFe2O4 with stoichiometric proportion (x) varying from 0.0 to 0.6 were prepared by the chemical co-precipitation method. The samples were sintered at 600 °C for 2 h and were characterized by X-ray diffraction (XRD), low field AC magnetic susceptibility, DC electrical resistivity and dielectric constant measurements. From the analysis of XRD patterns, the nanocrystalline ferrite had been obtained at pH=12.5–13 and reaction time of 45 min. The particle size was calculated from the most intense peak (3 1 1) using the Scherrer formula. The size of precipitated particles lies within the range 12–16 nm, obtained at reaction temperature of 70 °C. The Curie temperature was obtained from AC magnetic susceptibility measurements in the range 77–850 K. It is observed that Curie temperature decreases with the increase of Zn concentration. DC electrical resistivity measurements were carried out by two-probe method from 370 to 580 K. Temperature-dependent DC electrical resistivity decreases with increase in temperature ensuring the semiconductor nature of the samples. DC electrical resistivity results are discussed in terms of polaron hopping model. Activation energy calculated from the DC electrical resistivity versus temperature for all the samples ranges from 0.658 to 0.849 eV. The drift mobility increases by increasing temperature due to decrease in DC electrical resisitivity. The dielectric constants are studied as a function of frequency in the range 100 Hz–1 MHz at room temperature. The dielectric constant decreases with increasing frequency for all the samples and follow the Maxwell–Wagner's interfacial polarization. 相似文献
96.
Michael A. Olatunji Mayeen U. Khandaker Ekramul H. N. M. Mahmud Yusoff Md. Amin Janet A. Ademola Deborah O. Olorode 《Journal of Radioanalytical and Nuclear Chemistry》2018,316(3):933-945
Polypyrrole is incorporated with activated carbon in large size dopant solution and investigated for 137Cs removal studies. Adsorption experiments showed optimum conditions within 240 min contact time, pH 6, 0.2 g adsorbent and?≤?100 mg/l adsorbate dose, respectively, while the kinetic data followed pseudo-first-order model. Isotherm data were reproducible by the Langmuir isotherm yielding 23 mg/g maximum sorption capacity. Regeneration of adsorbent was attempted and indicated promising results within three cycles. The surface behavior has also been examined and revealed a well-ordered structure under gamma irradiation. This is a cheap adsorbent to consider and has also proven to possess higher sorption capacity than most highly-cost inorganic materials in use. 相似文献
97.
Reza Pourgholi Amin Esfahani Morteza Abtahi 《Journal of Applied Mathematics and Computing》2013,41(1-2):61-79
In this paper, we will first study the existence and uniqueness of the solution of a two-dimensional inverse heat conduction problem (IHCP) which is severely ill-posed, i.e., the solution does not depend continuously on the data. We propose a stable numerical approach based on the finite-difference method and the least-squares scheme to solve this problem in the presence of noisy data. We prove the convergence of the numerical solution, then to regularize the resultant ill-conditioned linear system of equations, we apply the Tikhonov regularization 0th, 1st and 2nd method to obtain the stable numerical approximation to the solution. The stability and accuracy of the scheme presented is evaluated by comparison with the Singular Value Decomposition (SVD) method. 相似文献
98.
99.
Desai Namita D. Singh Pirthipal P. Amin Purnima D. Jain Satishkumar P. 《Chromatographia》2009,69(3-4):385-388
This paper discusses the development of a stability-indicating reversed-phase LC method for analysis of cholecalciferol as the bulk drug and in formulations. The mobile phase was acetonitrile–methanol–water 50:50:2 (v/v). The calibration plot for the drug was linear in the range 0.4–10 μg mL−1. The method was accurate and precise with limits of detection and quantitation of 64 and 215 ng, respectively. Mean recovery was 100.71%. The method was used for analysis of cholecalciferol in pharmaceutical formulations in the presence of its degradation products and commonly used excipients.
相似文献100.
A procedure for the colorimetric assay of praziquantel has been developed. The method is based on the formation of charge-transfer
complexes with p-chloranil (I), dichloronitrophenol (II), 2,3-dichloro-5,6 dicyano-p-benzoquinone (III), 7,7,8,8-tetracyanoquinodimethane
(IV) and tetracyanoethylene (V) as π-acceptors to give highly coloured species. The coloured products are measured spectrophotometrically
at 550, 425, 460, 844 and 393 nm for I, II, III, IV and V, respectively. Optimization of the different reaction conditions
is described. The colour system obeyed Beer’s law in non-aqueous media in the concentration range 2.0–48 μg ml−1. It was stable for at least 4.0 h. The detection limit was found to be 0.6 μg ml−1. Applications of the procedure to the analysis of various pharmaceutical samples gave reproducible and accurate results.
Further, the validity of the procedure was confirmed by applying the standard addition technique. The total average recovery
was 100.2%.
Received June 10, 2000. Revision December 23, 2000. 相似文献