排序方式: 共有71条查询结果,搜索用时 31 毫秒
51.
Khosrow Zamani Shirindokht Bagheri 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1913-1918
Different types of 4,5-disubstituted 1,2,4-triazole-3-thiones were prepared by microwave irradiation as well as by a classical method. The beneficial effect of microwave irradiation on the dehydrative cyclization of thiosemicarbazides in different reaction media is described. Our results show that the effect of microwave irradiation on the reaction studied was the shortening of reaction times (from 2–9 h to 2–4 min) and a minor decrease (1–4%) in yields. The structure of the new compounds was established by FTIR, MS, and 1H NMR spectral data. 相似文献
52.
Mehdi Baneshi Khosrow Jafarpur Mojtaba Mahzoon 《Applied Physics A: Materials Science & Processing》2009,97(4):777-789
This paper reports on a study that explored the application of the entropy generation minimization method to solid mechanics.
After reviewing the definition of thermodynamic process and the principles of continuum mechanics, the constitutive equations
of four categories of solid behaviors namely thermoelasticity, thermoviscoelasticity, thermoplasticity, and thermoviscoplasticity
are discussed. Based on the computation of entropy generation due to mechanical harmonic loading in these four categories,
a problem is presented. Several nondimensional parameters are defined using material, loading, and geometric parameters. The
effects of nondimensional parameters on entropy generation due to heat conduction and internal dissipation are obtained and
the solutions to minimize entropy generation are discussed. 相似文献
53.
This paper presents computational experience with a rather straight forward implementation of an edge search algorithm for obtaining the globally optimal solution for linear programs with an additional reverse convex constraint. The paper's purpose is to provide a collection of problems, with known optimal solutions, and performance information for an edge search implementation so that researchers may have some benchmarks with which to compare new methods for reverse convex programs or concave minimization problems. There appears to be nothing in the literature that provides computational experience with a basic edge search procedure. The edge search implementation uses a depth first strategy. As such, this paper's implementation of the edge search algorithm is a modification of Hillestad's algorithm [11]. A variety of test problems is generated by using a modification of the method of Sung and Rosen [20], as well as a new method that is presented in this paper. Test problems presented may be obtained at ftp://newton.ee.ucla.edu/nonconvex/pub/. 相似文献
54.
Smriti Singh Dan Eugen Demco Khosrow Rahimi Radu Fechete Jos Carlos Rodriguez‐Cabello Martin Mller 《Macromolecular rapid communications》2016,37(2):181-186
The investigation of the coacervation (self‐aggregation) behavior of biomicrogels which can potentially be used as drug carriers is an important topic, because self‐aggregation can not only cause loss of activity, but also toxicity and immunogenicity. To study this effect microgels from elastin‐like recombinamer are synthesized using miniemulsion technique. The existence of coacervation for such microgels, at different concentrations and temperatures, is studied and proved by cryo‐field emission scanning clectron microscopy (cryo‐FESEM), cryo‐transmission electron microscopy (cryo‐TEM), and by a novel 1H high‐resolution magic angle sample spinning (HRMAS), nuclear magnetic resonance (NMR) spectroscopy, and relaxometry methods. The findings by 1H HRMAS NMR spectroscopy and relaxometry show simultaneous processes of volume phase temperature transition and coacervation with different sensitivity for hydrophobic and hydrophilic amino acid side‐chains in the microgel. The coacervation process is more evidential by the behavior of glycine α‐CH2, 1H NMR peak as compared to the proline β‐CH2.
55.
Majid Rafipoor Farhad Salimi Khosrow Jarrahian Seyyed Saeed Ghorashi 《Journal of Dispersion Science and Technology》2014,35(1):56-63
In this research, polyacrylamide-based gels were made at 25°C and aged in an oven at 90°C for 24 hours. The bottle testing results indicated that gel composed of 15000 ppm partially hydrolyzed polyacrylamide (PHPA) and 2500 ppm chromium(III) acetate exhibited an acceptable strength. The strain sweep test results showed that elastic modulus is fixed on 6 Pa below strain of 100%. According to frequency test results, linear viscoelasticity region was observed at the frequency limits from 0.1 to 10 s?1. Moreover, elastic modulus decreased from 8 Pa at 25°C to 4 Pa at 90°C. Furthermore, gelation time for gelant with the same composition was obtained (14, 13, and 20 minutes) in sequence. 相似文献
56.
Khosrow Jadidi Ramin Ghahremanzadeh Peiman Mirzaei Ayoob Bazgir 《Journal of heterocyclic chemistry》2011,48(5):1014-1018
A one‐pot, three‐component method for the efficient and simple synthesis of novel 2′‐amino‐8′,9′‐dihydro‐3′H‐spiro[indoline‐3,5′‐pyrimido[4,5‐b]quinoline]‐2,4′,6′(7′H,10′H)‐trione derivatives in aqueous media is reported. J. Heterocyclic Chem., (2011). 相似文献
57.
Khosrow Maleknejad Iraj Najafi Khalilsaraye Mahdieh Alizadeh 《Numerical Algorithms》2014,65(2):355-374
In this paper, we present an existence of solution for a functional integro-differential equation with an integral boundary condition arising in chemical engineering, underground water flow and population dynamics, and other field of physics and mathematical chemistry. By using the techniques of noncompactness measures, we employ the basic fixed point theorems such as Darbo’s theorem to obtain the mentioned aim in Banach algebra. Then this paper presents a powerful numerical approach based on Sinc approximation to solve the equation. Then convergence of this technique is discussed by preparing a theorem which shows exponential type convergence rate and guarantees the applicability of that. Finally, some numerical examples are given to confirm efficiency and accuracy of the numerical scheme. 相似文献
58.
Khalil Faghihi Khosrow Zamani Azizollah Mirsamie Mohammad Reza Sangi 《European Polymer Journal》2003,39(2):247-254
Rapid and highly efficient synthesis of novel optically active poly(amide-imide)s (PAIs) 6(a-f) was achieved using microwave irradiation. These were made from the polycondensation reactions of 4,4′-carbonyl-bis(phthaloyl-l-alanine) diacid chloride [N,N′-(4,4′-carbonyldiphthaloyl)] bisalanine diacid chloride 5 with six different derivatives of hydantoin and thiohydantoin compounds 4(a-f) in the presence of a small amount of a nonpolar organic medium that acts as a primary microwave absorber. Hydantoin and thiohydantoin derivatives 4(a-e) were synthesis from the reactions between benzil or benzil derivatives 3(a-e) with urea and thiourea. 5,5-Dimethylhydantoin 4f was synthesis from the reactions between acetone cyanohydrin 3f and ammonium carbonate. The polycondensation proceeded rapidly, and was completed within 10 min giving a series of PAIs with an inherent viscosity about 0.25-0.45 dL/g. The resulting PAIs 6(a-f) were obtained in a high yield and were optically active and thermally stable. All of the above compounds were fully characterized by means of Fourier transform infrared spectroscopy, elemental analyses, inherent viscosity (ηinh), solubility tests and specific rotation. Thermal properties of the PAIs 6(a-f) were investigated using thermal gravimetric analysis. 相似文献
59.
Javad Zolgharnein Ghasem Shahmoradi Khosrow Zamani Saeid Amani 《Journal of inclusion phenomena and macrocyclic chemistry》2007,59(1-2):99-103
The complexation reaction of phenylaza-15-crown-5, and 4-nitrobenzo-15-crown-5, benzo-15-crown-5 and dibenzopyrdino-18-crwon-6,
dibenzo-18-crown-6,dicyclohexyl-18-crown-6(cis and trans), and 18-crown-6 with Na+ ion in methanol have been studied by potentiometric method. The Na+ ion-selective electrode has been used both as indicator and reference electrode. The stoichiometry and stability constants
of complexes of these crown ethers with sodium ion were evaluated by MINIQUAD program. The major trend of stability of resulting
complexes of these macrocycle with Na+ ion varied in the order DCY18C6 > DB18C6 > 18C6 > DBPY18C6 > phenylaza-15C5 > benzo-15C5 > 4-nitrobenzo-15C5. The obtained
results in particular stability constant of complexes of DBPY18C6, phenylaza-15C5 and 4-nitrobenzo-15C5 with sodium ion in
comparison with other crowns ether are novel, and interesting. 相似文献
60.
Khosrow Moshirvaziri Mahyar A. Amouzegar Stephen E. Jacobsen 《Journal of Global Optimization》1996,8(3):235-243
A method of constructing test problems for linear bilevel programming problems is presented. The method selects a vertex of the feasible region, far away from the solution of the relaxed linear programming problem, as the global solution of the bilevel problem. A predetermined number of constraints are systematically selected to be assigned to the lower problem. The proposed method requires only local vertex search and solutions to linear programs. 相似文献