eng
University of Tehran
Journal of Sciences, Islamic Republic of Iran
1016-1104
2345-6914
2007-12-01
18
4
303
395
35065
Synthesis of Binary Ti-Si Mixed Oxides Nanoparticles with Rutile Structure as Selective Catalyst for Epoxidation of Alkenes
F. Farzaneh
1
Department of Chemistry, Alzahra University, Vanak, Tehran, Islamic Republic of Iran
The nanoparticles of Ti-Si mixed oxides (NTSO) with Rutile structure were prepared by sol-gel method in a mixture of alcohol and water as solvent. The solid product was characterized by XRD, FTIR, SEM, TEM, UV, TGA and laser Raman spectroscopy. The catalytic activity of NTSO (5-10 nm) was investigated in the epoxidation of cis stilbene, trans stilbene, and norbornene by using oxidants such as tert-butylhydroperoxide (TBHP), molecular oxygen (O2)/isobutyraldehyde (IBA) and hydrogen peroxide (H2O2). It was found that epoxides of trans-stilbene andnorbornenewereformedquantitativelywiththegreenH2O2oxidantduring12h.
https://jsciences.ut.ac.ir/article_35065_7dd368e2a660d1b78517bb5587f186ec.pdf
Epoxidation
Alkenes
Ti-Si mixed oxides
nanoparticles
Heterogeneous catalysis
eng
University of Tehran
Journal of Sciences, Islamic Republic of Iran
1016-1104
2345-6914
2007-12-01
18
4
311
316
35073
Complete Convergence and Some Maximal Inequalities for Weighted Sums of Random Variables
M. Amini
1
Department of Statistics, Faculty of Mathematical Sciences, Ferdowsi University of Mashhad, Mashhad, Islamic Republic of Iran
Let be a sequence of arbitrary random variables with and , for every and be an array of real numbers. We will obtain two maximal inequalities for partial sums and weighted sums of random variables and also, we will prove complete convergence for weighted sums , under some conditions on and sequence .
https://jsciences.ut.ac.ir/article_35073_d621f17bd3310b1e9969d451974cb757.pdf
eng
University of Tehran
Journal of Sciences, Islamic Republic of Iran
1016-1104
2345-6914
2007-12-01
18
4
317
321
35075
A Computational Meshless Method for Solving Multivariable Integral Equations
E. Babolian
1
Department of Mathematics, Teacher Training University, Tehran, Islamic Republic of Iran
In this paper we use radial basis functions to solve multivariable integral equations. We use collocation method for implementation. Numerical experiments show the accuracy of the method.
https://jsciences.ut.ac.ir/article_35075_efa1cb388921b5a382f132d3c315a55d.pdf
eng
University of Tehran
Journal of Sciences, Islamic Republic of Iran
1016-1104
2345-6914
2007-12-01
18
4
323
328
35076
On the U-WPF Acts over Monoids
A. Golchin
1
Department of Mathematics, University of Sistan and Baluchestan, Zahedan, Islamic Republic of Iran
Valdis Laan in [5] introduced an extension of strong flatness which is called weak pullback flatness. In this paper we introduce a new property of acts over monoids, called U-WPF which is an extension of weak pullback flatness and give a classification of monoids by this property of their acts and also a classification of monoids when this property of acts implies others. We also show that regularity and strong faithfulness of acts both imply U-WPF. An equivalent of that over monoids for which torsion freeness implies U-WPF is given too.
https://jsciences.ut.ac.ir/article_35076_7179cbf62319b0387870e23cc9c2338f.pdf
U-WPF
Strongly faithful
Regular
eng
University of Tehran
Journal of Sciences, Islamic Republic of Iran
1016-1104
2345-6914
2007-12-01
18
4
329
337
35077
Nonlinear Two-Phase Stefan Problem
K. Ivaz
1
Department of Mathematics, University of Tabriz, Tabriz, Islamic Republic of Iran
In this paper we consider a nonlinear two-phase Stefan problem in one-dimensional space. The problem is mapped into a nonlinear Volterra integral equation for the free boundary.
https://jsciences.ut.ac.ir/article_35077_32721d24440447cca51b48fcd81190bb.pdf
Free boundary problems
integral equation
eng
University of Tehran
Journal of Sciences, Islamic Republic of Iran
1016-1104
2345-6914
2007-12-01
18
4
339
345
35078
Derivations on Certain Semigroup Algebras
M. Lashkarizadeh Bami
1
Department of Mathematics, University of Isfahan, Isfahan, Islamic Republic of Iran
In the present paper we give a partially negative answer to a conjecture of Ghahramani, Runde and Willis. We also discuss the derivation problem for both foundation semigroup algebras and Clifford semigroup algebras. In particular, we prove that if S is a topological Clifford semigroup for which Es is finite, then H1(M(S),M(S))={0}.
https://jsciences.ut.ac.ir/article_35078_5dc248c0cdd852f58b420f59cb5d150c.pdf
Foundation semigroup
Semigroup algebra
Derivation
First order cohomology
Clifford semigroup
eng
University of Tehran
Journal of Sciences, Islamic Republic of Iran
1016-1104
2345-6914
2007-12-01
18
4
347
354
35079
Modified Progressive Type-II Censoring Procedure in Life-Testing under the Weibull Model
M. Khodadadi
1
Department of Statistics, Faculty of Mathematical Sciences, Shahid Beheshti University, Tehran, Islamic Republic of Iran
In this paper we introduce a new scheme of censoring and study it under the Weibull distribution. This scheme is a mixture of progressive Type II censoring and self relocating design which was first introduced by Srivastava [8]. We show the superiority of this censoring scheme (PSRD) relative to the classical schemes with respect to “asymptotic variance”. Comparisons are also made with respect to the total expected time under experiment (TETUE) as an important feature of time and cost saving. These comparisons show that TETUE(SRD) < TETUE(PSRD) < TETUE(PC2) if 0 < β < 1, TETUE(PSRD) = TETUE(SRD) < TETUE(PC2) if β = 1 and TETUE(PSRD) is the best among all the designs if β = 2 (Rayleigh distribution case).
https://jsciences.ut.ac.ir/article_35079_97b138e63d61d51fa7c1effe3f11847d.pdf
Asymptotic variance
Fisher information matrix
Maximum likelihood
Self relocating design (SRD)
Total expected time under experiment
eng
University of Tehran
Journal of Sciences, Islamic Republic of Iran
1016-1104
2345-6914
2007-12-01
18
4
355
360
35080
Essentially Retractable Modules
M.R. Vedadi
1
Department of Mathematical Sciences, Isfahan University of Technology, Isfahan 84156-83111, Islamic Republic of Iran
We call a module essentially retractable if HomR for all essential submodules N of M. For a right FBN ring R, it is shown that: (i) A non-zero module is retractable (in the sense that HomR for all non-zero ) if and only if certain factor modules of M are essentially retractable nonsingular modules over R modulo their annihilators. (ii) A non-zero module is essentially retractable if and only if there exists a prime ideal such that HomR. Over semiprime right nonsingular rings, a nonsingular essentially retractable module is precisely a module with non-zero dual. Moreover, over certain rings R, including right FBN rings, it is shown that a nonsingular module M with enough uniforms is essentially retractable if and only if there exist uniform retractable R-modules and R-homomorphisms with .
https://jsciences.ut.ac.ir/article_35080_daa38f2a160fc3e3a8b0aafa70c41eff.pdf
Dual module
Essentially retractable
Homo-related