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71.
Water was a suitable medium for Paal–Knorr pyrrole cyclocondensation. Hexa-2,5-dione was reacted with several aliphatic and aromatic primary amines, affording N-substituted 2,5-dimethyl pyrrole derivatives in good to excellent yields. An efficient, green method using water either as environmentally friendly solvent or catalyst was presented. 相似文献
72.
Image processing, in particular image enhancement techniques have been the focal point of considerable research activity in the last decade. With the aid of an existing image enhancement technique, adaptive unsharp masking (AUM), we propose a novel kernel to be used in AUM filtering in order to enhance discontinuities which occur on the edges of targets of interest in infrared (IR) images. The proposed method uses an adaptive filter approach where an objective function is minimized by using descent algorithms. The output IR image has better sharpness and contrast adjustment for the detection of targets in terms of objective quality metrics. Hence, the proposed method ensures that the edges of the targets in IR images are sharper and that the quality of contrast adjustment has its optimum level in terms of peak signal-to-noise ratios. 相似文献
73.
We demonstrate a Raman laser using cold (87)Rb atoms as the gain medium in a high-finesse optical cavity. We observe robust continuous wave lasing in the atypical regime where single atoms can considerably affect the cavity field. Consequently, we discover unusual lasing threshold behavior in the system causing jumps in lasing power, and propose a model to explain the effect. We also measure the intermode laser linewidth, and observe values as low as 80 Hz. The tunable gain properties of this laser suggest multiple directions for future research. 相似文献
74.
Elemental‐Sulfur‐Mediated Facile Synthesis of a Covalent Triazine Framework for High‐Performance Lithium–Sulfur Batteries
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Dr. Siddulu Naidu Talapaneni Tae Hoon Hwang Sang Hyun Je Dr. Onur Buyukcakir Prof. Jang Wook Choi Prof. Ali Coskun 《Angewandte Chemie (International ed. in English)》2016,55(9):3106-3111
A covalent triazine framework (CTF) with embedded polymeric sulfur and a high sulfur content of 62 wt % was synthesized under catalyst‐ and solvent‐free reaction conditions from 1,4‐dicyanobenzene and elemental sulfur. Our synthetic approach introduces a new way of preparing CTFs under environmentally benign conditions by the direct utilization of elemental sulfur. The homogeneous sulfur distribution is due to the in situ formation of the framework structure, and chemical sulfur impregnation within the micropores of CTF effectively suppresses the dissolution of polysulfides into the electrolyte. Furthermore, the triazine framework facilitates electron and ion transport, which leads to a high‐performance lithium–sulfur battery. 相似文献
75.
Michelle M. H. Şeref Onur Şeref Aydın Alptekinoğlu S. Selçuk Erengüç 《Computational Management Science》2016,13(4):597-626
Advance selling of goods and services is a form of separating purchase from consumption. It is often employed when consumers are uncertain about their consumption utilities until a short time period before consumption. A book to be released, a concert to attend, or a cruise to take are some examples. Invariably, in consumers’ mind inventory availability (of copies, seats, or rooms) is a concern. In this paper we study a retailer’s inventory and pricing decisions in an advance selling scenario that involves consumers who are strategic. Some consumers not only consider advance and spot prices, but also the uncertainty in future availability of the product (during the spot period) and in their consumption utility from it. We characterize the optimal inventory management and pricing policies, and discuss several interesting aspects of the solution. For example, it can be optimal for the retailer to limit advance sales even if there is more demand for it, and it can be optimal for the retailer to limit its inventory even though there is more capacity to keep it, but not both. 相似文献
76.
Onur ahin Orhan Büyükgüngr Dursun Ali Kse Hacali Necefoglu 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(10):m317-m320
The title compound, [Co(C7H5O3)2(C6H6N2O)2(H2O)2], forms a three‐dimensional hydrogen‐bonded supramolecular structure. The CoII ion is in an octahedral coordination environment comprising two pyridyl N atoms, two carboxylate O atoms and two O atoms from water molecules. Intermolecular N—H...O and O—H...O hydrogen bonds produce R22(8), R22(12) and R22(14) rings, which lead to two‐dimensional chains. An extensive three‐dimensional supramolecular network of C—H...O, N—H...O and O—H...O hydrogen bonds and C—H...π interactions is responsible for crystal structure stabilization. This study is an example of the construction of a supramolecular assembly based on hydrogen bonds in mixed‐ligand metal complexes. 相似文献
77.
Hadi Naslhajian S. Morteza F. Farnia Ayda Sheykhi Onur Şahin Okan Zafer Yeşilel 《Journal of Coordination Chemistry》2017,70(17):2940-2949
A new decavanadate polyoxovanadate nanocluster, [2-ampH]6[V10O28]?2H2O (1), was synthesized through reaction between ammonium vanadate and 2-aminopyridine at pH = 2. Nanocluster 1 was characterized by IR, elemental analysis, and X-ray crystallography. 1 was found to adsorb and desorb dyes and may have widespread application in wastewater treatment. The utility of 1 for adsorption of methylene blue was studied. The adsorbed dyes can be easily desorbed, and 1 has full efficiency after five cycles. 相似文献
78.
In this research, we present a new approach based on variational iteration method for solving nonlinear time-fractional partial differential equations in large domains. The convergence of the method is shown with the aid of Banach fixed point theorem. The maximum error bound is specified. The optimal value of auxiliary parameter is obtained by use of residual error function. The fractional derivatives are taken in the Caputo sense. Numerical examples that involve the time-fractional Burgers equation, the time-fractional fifth-order Korteweg–de Vries equation and the time-fractional Fornberg–Whitham equation are examined to show the appropriate properties of the method. The results reveal that a new approach is very effective and convenient. 相似文献
79.
Synthesis of a series of 3-acetylcoumarin-derived chalcones (1a–16a) was catalyzed with Amberlyst 26A in ethanol. Using reusable Amberlyst 26A and biobased solvent ethanol make this method highly ecofriendly and simple. Amberlyst 26A was found to be a highly effective catalyst for cross aldol reaction. The results shown that the method is operationally simple to implement with a wide scope of substrates. 相似文献
80.
Özge Dağlı Dursun Ali Köse Gülçin Alp Avcı Onur Şahin 《Journal of Thermal Analysis and Calorimetry》2017,129(3):1389-1402
Coordination complexes of transition metal cations (CoII, NiII, CuII and ZnII) containing coumarilate and N,N′-diethylnicotinamide were synthesized. The structural characterization and thermal behaviour analysis of novel samples synthesized were conducted through elemental analysis, magnetic susceptibility, solid-state UV–Vis, direct and injection probe mass spectra, FTIR spectra, thermoanalytic TG-DTG/DTA and single crystal X-ray diffraction methods. The structural details of single crystals of [Co(dena)2(H2O)4](coum)2 (I) and [Cu(coum)2(dena)2(H2O)2] (III) complexes were resolved completely. Moreover, the results of analysis obtained for [Ni(coum)2(dena)2(H2O)2] (II) and [Zn(dena)2(H2O)4](coum)2 (IV) complexes were interpreted considering the samples with crystal structures defined and made assumptions about the structural details. It was determined that the complex of CoII metal cation has salt-type structure and the coordination number of metal is accomplished to six as the sum of 4 mol of water and also 2 mol of N,N′-diethylnicotinamide ligands in trans position located within the coordination sphere. It was observed that 2 mol of coumarilate anions are located outside the coordination sphere and have stabilized to the charge (2+) of metal. The CuII complex has totally molecular structure, and the coordination sphere of metal cation was 6 as the sum of 2 mol of water, 2 mol of N,N′-diethylnicotinamide and 2 mol of monoanionic monodentate coumarilate ligands. All ligands have been located in –trans position. The geometry of both complex structures is distorted octahedral. It is assumed that the NiII complex structure is isostructural with CuII complex structure and also does ZnII complex with CoII structure. It was determined that the decomposition products obtained from thermal analysis are the oxides of related metal cations. 相似文献