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61.
Ramazan Gürbüz 《International Journal of Mathematical Education in Science & Technology》2013,44(6):743-767
The purpose of this study is to investigate and compare the effects of activity-based and traditional instructions on students’ conceptual development of certain probability concepts. The study was conducted using a pretest–posttest control group design with 80 seventh graders. A developed ‘Conceptual Development Test’ comprising 12 open-ended questions was administered on both groups of students before and after the intervention. The data were analysed using analysis of covariance, with the pretest as covariate. The results revealed that activity-based instruction (ABI) outperformed the traditional counterpart in the development of probability concepts. Furthermore, ABI was found to contribute students’ conceptual development of the concept of ‘Probability of an Event’ the most, whereas to the concept of ‘Sample Space’ the least. As a consequence, it can be deduced that the designed instructional process was effective in the instruction of probability concepts. 相似文献
62.
The Dirac equation, with position-dependent mass, is solved approximately for the generalized Hulthén potential with any spin-orbit quantum number κ. Solutions are obtained by using an appropriate coordinate transformation, reducing the effective mass Dirac equation to a Schrödinger-like differential equation. The Nikiforov-Uvarov method is used in the calculations to obtain energy eigenvalues and the corresponding wave functions. Numerical results are compared with those given in the literature. Analytical results are also obtained for the case of constant mass and the results are in good agreement with the literature. 相似文献
63.
We study the approximate analytical solutions of the Dirac equation for the generalized Woods-Saxon potential with the pseudo-centrifugal term. We apply the Nikiforov-Uvarov method (which solves a second-order linear differential equation by reducing it to a generalized hypergeometric form) to spin- and pseudospin-symmetry to obtain, in closed form, the approximately analytical bound state energy eigenvalues and the corresponding upper- and lower-spinor components of two Dirac particles. The special cases κ = ±1 (s = $ \tilde l $ = 0, s-wave) and the non-relativistic limit can be reached easily and directly for the generalized and standard Woods-Saxon potentials. We compare the non-relativistic results with those obtained by others. 相似文献
64.
Synthesis of (2S)-3-(2,4,5-trifluorophenyl)propane-1,2-diol by the Sharpless asymmetric epoxidation reaction has been achieved. 2,4,5-Trifluorobenzaldehyde with methyl 2-(triphenyl-λ5-phosphanylidene)acetate gave methyl (E)-3-(2,4,5-trifluorophenyl)acrylate in 83% yield. The reduction of ester group with DibalH followed by Sharpless asymmetric epoxidation gave ((2R,3R)-3-(2,4,5-trifluorophenyl)oxiran-2-yl)methanol. Pd/C-catalyzed hydrogenation of epoxy alcohol furnished (2S)-3-(2,4,5-trifluorophenyl)propane-1,2-diol with >90% ee and 71% yield. 相似文献
65.
Ramazan Gürkan 《International journal of environmental analytical chemistry》2019,99(10):977-995
The present study describes chelation of Pb(II) with ascorbic acid and formation of a charge-transfer sensitive ion-pair in the presence of Rhodamine 6G at pH 5.5, and then its extraction to the micellar phase of non-ionic surfactant, PONPE 7.5 by an ultrasound-assisted cloud point extraction method before analysis by FAAS. The various variables affecting ion-pair formation and extraction efficiency were studied and optimised. Under the optimised conditions, the good linear relationships in the ranges of 0.4–150 μg L?1 and 0.8–120 μg L?1 for solvent-based calibration and matrix-matched calibration curves, respectively, were achieved with a pre-concentration factor of 71.4 from pre-concentration of 50-mL sample. Moreover, the limits of detection with good sensitivity enhancements of 124 and 114.5 were 0.13 and 0.24 μg L?1, respectively, while the intra-day and inter-day precision (as RSD%, for five replicate measurements of 5 and 100 μg L?1 in the same day and three succeed days) were in range of 2.8–5.4% and 3.7–6.3%, respectively. The matrix effect on triplicate determination of 50 µg L?1 Pb(II) was also investigated. The accuracy of the method was statistically verified by the analysis of two certified reference materials (CRMs) after digestion with acid mixtures (HNO3-H2O2-HF and HNO3-H2O2) and dilution at suitable ratios. It has been observed that there is statistically not a significant difference between the certified- and found-values. The accuracy was also controlled using the pre-treated sample solutions spiked at different concentration levels, and the good spiked recoveries were obtained in range of 90–102.8%. The method was successfully applied to the determination of trace amounts of lead in water and food matrices with satisfactory results. 相似文献
66.
Exact solutions of the D-dimensional Schrödinger equation for a ring-shaped pseudoharmonic potential
A new non-central potential, consisting of a pseudoharmonic potential plus another recently proposed ring-shaped potential, is solved. It has the form $ V(r,\theta ) = \tfrac{1} {8}\kappa r_e^2 \left( {\tfrac{r} {{r_e }} - \tfrac{{r_e }} {r}} \right)^2 + \tfrac{{\beta cos^2 \theta }} {{r^2 sin^2 \theta }} A new non-central potential, consisting of a pseudoharmonic potential plus another recently proposed ring-shaped potential,
is solved. It has the form . The energy eigenvalues and eigenfunctions of the bound-states for the Schr?dinger equation in D-dimensions for this potential are obtained analytically by using the Nikiforov-Uvarov method. The radial and angular parts
of the wave functions are obtained in terms of orthogonal Laguerre and Jacobi polynomials. We also find that the energy of
the particle and the wave functions reduce to the energy and the wave functions of the bound-states in three dimensions.
相似文献
67.
Ramazan Benrashid Gordon L. Nelson 《Journal of polymer science. Part A, Polymer chemistry》1994,32(10):1847-1865
Siloxane urethane block copolymers were prepared with siloxanes as the soft segment. Films were cast from a variety of solvents. Solvent has an effect on the segregation of soft and hard segments. Surface studies, including ESCA, EDS, and FT-IR, show well segregated block copolymers with enhanced siloxane on the surface. DSC studies show a low mp (-44°C) for the soft segment and a Tg for the hard segment above room temperature. These materials show higher thermal stability compared to polyether urethane block copolymers. These copolymers also show relatively good resistance to exposure to oxygen plasma and show improved flame retardancy compared to nonsiliconated, polyether polyurethane block copolymers. © 1994 John Wiley & Sons, Inc. 相似文献
68.
Gup R Kirkan B 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,62(4-5):1188-1195
Two types of copper(II) and nickel(II) complexes derived from benzophenone anthranoylhydrazone (L1), 2-acetonaftanone anthranoylhydrazone (L2), 4-phenylacetonaftonone anthranoylhydrazone (L3), benzophenone salicyoylhydrazone (L4), 2-acetonaftanon salicyoylhydrazone (L5), 4-phenylacetonaftanon salicyoylhydrazone (L6) and bidentate heterocyclic base [1,10-phenanthroline (phen)] with general stoichiometry [ML2] and [ML(phen)]Cl have been synthesized and characterized by elemental analysis, infrared spectra, UV-vis electronic absorption spectra and magnetic susceptibility measurements. The effect of varying pH and solvent on the absorption behavior of both ligands and complexes have been investigated. According to the IR spectra, the ligands act as monobasic bidentate and coordination takes place in the enol tautomeric form. 相似文献
69.
An alternative approximation scheme has been used in solving the Schr?dinger equation to the more general case of exponential
screened Coulomb potential, V(r) = −(a/r)[1 + (1 + br)e
−2br
]. The bound state energies of the 1s, 2s and 3s-states, together with the ground state wave function are obtained analytically upto the second perturbation term.
相似文献
70.
The supersymmetric solutions of PT -symmetric and Hermitian/non-Hermitian forms of quantum systems are obtained by solving the Schr?dinger equation for the
Exponential-Cosine Screened Coulomb potential. The Hamiltonian hierarchy inspired variational method is used to obtain the
approximate energy eigenvalues and corresponding wave functions.
相似文献