排序方式: 共有140条查询结果,搜索用时 15 毫秒
31.
In 1999 Nina Zorboska and in 2003 P. S.Bourdon, D. Levi, S.K.Narayan and J.H. Shapiro investigated the essentially normal composition operator ${C_\varphi }$ , when φ is a linear-fractional self-map of D. In this paper first, we investigate the essential normality problem for the operator T w ${C_\varphi }$ on the Hardy space H 2, where w is a bounded measurable function on ?D which is continuous at each point of F(φ), φ ∈ S(2), and T w is the Toeplitz operator with symbol w. Then we use these results and characterize the essentially normal finite linear combinations of certain linear-fractional composition operators on H 2. 相似文献
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Mohammad Rahimizadeh Mehdi Pordel Mahsa Ranaei Mehdi Bakavoli 《Journal of heterocyclic chemistry》2012,49(1):208-211
Nucleophilic substitution of hydrogen in nitro derivative of imidazo[1,2‐a]pyridine has been used as a key step in the one‐pot synthesis of a new highly fluorescent heterocyclic system pyrido [1″,2″:1′,2′]imidazo[4′,5′:5,6]pyrido[2,3‐b]indole. J. Heterocyclic Chem., (2012). 相似文献
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Mohammad Bakherad Ali Keivanloo Elmira Moradian Amir H. Amin Rahele Doosti Mahsa Armaghan 《Journal of the Iranian Chemical Society》2018,15(12):2811-2819
The new catalyst silica-caffeine hydrogen sulfate [SiO2-caff.]HSO4 was conveniently prepared from commercially available 3-chloropropyltriethoxysilane via immobilization on silica followed by reaction with caffeine. The catalyst prepared was then characterized by the FT-IR spectroscopy, TGA, EDX, and SEM techniques. It was found that this heterogeneous catalyst was a highly efficient one for the synthesis of tetrahydrobenzo[b]pyrans in good-to-high yields, and could be recovered by a simple filtration of the reaction solution and reused for five consecutive runs. The attractive features of this method are simple procedure, clean reaction, easy work-up, use of a reusable catalyst, and performing a multi-component reaction. 相似文献
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Parisa Izadiyan Bahram Hemmateenejad S. Mohsen Taghavi Mahsa Izadiyan 《Journal of the Iranian Chemical Society》2018,15(2):259-268
Local names are not reliable sources for identification of plants, because they differ significantly from one region to another. Apart from confusing nomenclature, the similar appearance and fragrance of Shirazi thyme and Thymus species cause misidentification. In order to prevent the adverse events in relation to the use of improper herbal products, easy-to-use quality control (QC) methodology was developed to classify these culinary plants. Fourier transform infrared (FT-IR) fingerprinting technique was applied for classification of these plants on the basis of their biochemical compositions. Powerful PLS-DA classification model with classification accuracy of 100% was obtained. For the first time in the present study, it was revealed that Shirazi thyme samples have higher antioxidant activity [average IC50 of 37.03 (µg/ml)] compared to different Thymus species [average IC50 of 148.35 (µg/ml)]. FT-IR fingerprint profiles were also used to construct a predictive model for antioxidant activity of the plants based on a reliable PLSR model. The developed PLSR model revealed that IR wavenumbers of 1000–1200, 1700, and 3200–3500 cm?1 are important for antioxidant activity prediction of the analyzed plants. The applied approach has the potential for being used in QC programs not only for fraud mitigation and detection, but also for estimation of antioxidant activity of the culinary plants. 相似文献
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The application of p-aminophenol as a suitable mediator, as a sensitive and selective voltammetric sensor for the determination of hydrazine using square wave voltammetric method were described. The modified multiwall carbon nanotubes paste electrode exhibited a good electrocatalytic activity for the oxidation of hydrazine at pH = 7.0. The catalytic oxidation peak currents showed a linear dependence of the peaks current to the hydrazine concentrations in the range of 0.5–175 μmol/L with a correlation coefficient of 0.9975. The detection limit (S/N = 3) was estimated to be 0.3 μmol/L of hydrazine. The relative standard deviations for 0.7 and 5.0 μmol/L hydrazine were 1.7 and 1.1%, respectively. The modified electrode showed good sensitivity and selectivity. The diffusion coefficient (D = 9.5 × 10–4 cm2/s) and the kinetic parameters such as the electron transfer coefficient (α = 0.7) of hydrazine at the surface of the modified electrode were determined using electrochemical approaches. The electrode was successfully applied for the determination of hydrazine in real samples with satisfactory results. 相似文献
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Omid Bagheri Faranak Sadegh Majid Moghadam Shahram Tangestaninejad Valiollah Mirkhani Iraj Mohammadpoor‐Baltork Mahsa Safiri 《应用有机金属化学》2014,28(5):337-346
The tetrakis(4‐N‐methylpyridinium)porphyrinatopalladium(II) iodide, [Pd(TMPyP)]I4, supported on Dowex 50WX8 and Amberlite IR‐120 ion‐exchange resins, was used as heterogeneous, recyclable and active catalyst for the Suzuki–Miyaura and Heck cross‐coupling reactions. These catalysts were applied to coupling of various aryl halides with phenylboronic acid and styrene in Suzuki and Heck reactions, respectively, and the corresponding products were obtained in excellent yields and short reaction times. The catalysts could be recovered easily by simple filtration and reused several times without significant loss of their catalytic activity. The catalysts were characterized by diffuse‐reflectance UV–visible spectroscopy and scanning electron microscopy, and their stability was confirmed by TGA. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Omid Bozorg Haddad Mahsa Mirmomeni Mahboubeh Zarezadeh Mehrizi Miguel A. Mariño 《Computational Optimization and Applications》2010,47(1):97-128
Effective project management requires the development of a realistic plan and a clear communication of the plan from the beginning
to the end of the project. The critical path method (CPM) of scheduling is the fundamental tool used to develop and interconnect
project plans. Ensuring the integrity and transparency of those schedules is paramount for project success. The complex and
discrete nature of the solution domain for such problems causes failing of traditional and gradient-based methods in finding
the optimal or even feasible solution in some cases. The difficulties encountered in scheduling construction projects with
resource constraints are highlighted by means of a simplified bridge construction problem and a basic masonry construction
problem. The honey-bee mating optimization (HBMO) algorithm has been previously adopted to solve mathematical and engineering
problems and has proven to be efficient for searching optimal solutions in large-problem domains. This paper presents the
HBMO algorithm for scheduling projects with both constrained and unconstrained resources. Results show that the HBMO algorithm
is applicable to projects with or without resource constraints. Furthermore, results obtained are promising and compare well
with those of well-known heuristic approaches and gradient-based methods. 相似文献
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Mahsa Fatehi Mahmood Haji Shaabani Derek Thompson 《Complex Analysis and Operator Theory》2018,12(7):1767-1778
In this paper, we study quasinormal and hyponormal composition operators \(W_{\psi ,\varphi }\) with linear fractional compositional symbol \(\varphi \) on the Hardy and weighted Bergman spaces. We characterize the quasinormal composition operators induced on \(H^{2}\) and \(A_{\alpha }^{2}\) by these maps and many such weighted composition operators, showing that they are necessarily normal in all known cases. We eliminate several possibilities for hyponormal weighted composition operators but also give new examples of hyponormal weighted composition operators on \(H^2\) which are not quasinormal. 相似文献