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51.
Poornima Sharma Debraj Gangopadhyay Sima Umrao Shiv Kumar A. K. Ghosh P. C. Mishra Ranjan K. Singh 《Journal of Raman spectroscopy : JRS》2016,47(4):468-475
Polymorphism is an important characteristic which affects the activity, solubility and other physical properties of a compound and can be induced by varying temperature, pressure and solvent. The presence and conversion of α to β polymorphic forms of an anti‐rheumatic drug leflunomide have been studied by temperature‐dependent and in situ Raman observations. Both α and β polymorphs were found to co‐exist in the temperature interval 367–372 K. The α form alone exists below 367 K and the β form alone above 373 K. The CO stretching band clearly demonstrates the α → β conversion because of breaking of N–H···O bond and formation of N–H···N bond. On cooling the Raman spectra suggest the irreversibility of this conversion. Thermodynamic stability, crystal parameters and surface morphology of both forms in the leflunomide powder used for the present study have been verified by differential scanning calorimetry, X‐ray powder diffraction and scanning electron microscopy. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
52.
53.
Ramin Rabbani Sima Saeedi Md Nazimuddin Hctor Barbero Nathalie Kyritsakas Travis A. White Eric Masson 《Chemical science》2021,12(46):15347
A cucurbit[8]uril (CB[8])-secured platinum terpyridyl chloride dimer was used as a photosensitizer and hydrogen-evolving catalyst for the photoreduction of water. Volumes of produced hydrogen were up to 25 and 6 times larger than those obtained with the corresponding free and cucurbit[7]uril-bound platinum monomer, respectively, at equal Pt concentration. The thermodynamics of the proton-coupled electron transfer from the Pt(ii)–Pt(ii) dimer to the corresponding Pt(ii)–Pt(iii)–H hydride key intermediate, as quantified by density functional theory, suggest that CB[8] secures the Pt(ii)–Pt(ii) dimer in a particularly reactive conformation that promotes hydrogen formation.The cucurbit[8]uril macrocycle can secure a platinum terpyridyl complex into a particularly reactive dimer that catalyzes the photoreduction of water. 相似文献
54.
A novel Ni‐based metal–organic framework (Ni‐MOF) with a Schiff base ligand as an organic linker, Ni3(bdda)2(OAc)2?6H2O (H2bdda = 4,4′‐[benzene‐1,4‐diylbis(methylylidenenitrilo)]dibenzoic acid), was synthesized and characterized using powder X‐ray powder diffraction, thermogravimetric analysis, Brunauer–Emmett–Teller measurements, inductively coupled plasma atomic emission spectroscopy, transmission electron microscopy, elemental analysis and Fourier transform infrared spectroscopy. The synthesized Ni‐MOF exhibited a high catalytic activity in benzyl alcohol oxidation using tert‐butyl hydroperoxide under solvent‐free conditions. Also, the efficiency of the catalyst was investigated in the cascade reaction of oxidation–Knoevanagel condensation under mild conditions. The Ni‐MOF catalyst could be recovered and reused four times without significant reduction in its catalytic activity. 相似文献
55.
A nonparametric structural damage detection methodology based on neural networks method is presented for health monitoring
of structure-unknown systems. In this approach appropriate neural networks are trained by use of the modal test data from
a ‘healthy’ structure. The trained networks which are subsequently fed with vibration measurements from the same structure
in different stages have the capability of recognizing the location and the content of structural damage and thereby can monitor
the health of the structure. A modified back-propagation neural network is proposed to solve the two practical problems encountered
by the traditional back-propagation method, i.e., slow learning progress and convergence to a false local minimum. Various
training algorithms, types of the input layer and numbers of the nodes in the input layer are considered. Numerical example
results from a 5-degree-of-freedom spring-mass structure and analyses on the experimental data of an actual 5-storey-steel-frame
demonstrate that neural-networks-based method is a robust procedure and a practical tool for the detection of structural damage,
and that the modified back-propagation algorithm could improve the computational efficiency as well as the accuracy of detection
Project supported by the National Natural Science Foundation of China (No. 59908003) and the Natural Science Foundation of
Hubei Province (No. 99J035). 相似文献
56.
Murugappan Senthilvelan Meng Yu Daniel Iancu Mihai Sima Michael Schulte 《Analog Integrated Circuits and Signal Processing》2011,69(2-3):191-206
Wireless protocols strive to increase spectral efficiency and achieve high data throughput. Low-density parity-check (LDPC) codes are advanced forward error correction (FEC) codes that use iterative decoding techniques to achieve close to the Shannon capacity. Due to their superior performance, state-of-art wireless protocols, such as WiMAX and LTE Advanced, are adopting LDPC codes. LDPC codes come with the high cost of drastically increased computational effort for decoding. Among the proposed decoding algorithms, the belief propagation (BP) algorithm leads to a good approximation of an optimal decoder; however, it uses compute-intensive hyperbolic trigonometric functions. To reduce the computational complexity, typical LDPC decoder implementations use simplified algorithms, such as the min-sum algorithm, at the expense of reduced signal processing performance. Efficient and accurate methods to compute hyperbolic trigonometric functions can facilitate the use of the BP algorithm in real-time LDPC decoder implementations. This paper investigates hyperbolic COordinate Rotation DIgital Computer (CORDIC) instruction set architecture (ISA) extensions for software-defined radio (SDR) processors to compute the hyperbolic trigonometric functions for LDPC decoding efficiently. The CORDIC ISA extensions are evaluated on the low-power multi-threaded Sandbridge Sandblaster? SB3000 platform. The computational performance, numerical accuracy, hardware estimates, power consumption estimates, and memory requirements with the CORDIC ISA extensions are compared to a baseline implementation without these extensions on the SB3000. 相似文献
57.
Kosareva O Daigle JF Panov N Wang T Hosseini S Yuan S Roy G Makarov V Chin SL 《Optics letters》2011,36(7):1035-1037
Experimentally measured conical emission rings on the blue side of the filament supercontinuum of a 800 nm 50 fs pulse in air are reproduced in simulations with plasma and the third-order Kerr as the nonlinear terms. This agreement indicates plasma as the dominant mechanism arresting the self-focusing collapse. The higher order Kerr terms with the recently measured coefficients stop the collapse at a lower intensity than the plasma does and lead to the spherical angle-wavelength spectrum without blueshifted rings. 相似文献
58.
Askari Azam Entezari Amir Arsalan Pordel Mehdi Beigoli Sima Nezafat Yazdi Zeinab Jahani Moghaddam Arya Chamani Jamshidkhan 《Journal of the Iranian Chemical Society》2020,17(1):135-149
Journal of the Iranian Chemical Society - Evaluating the binding interaction between biomacromolecules and various chemical compounds is one of the most biologically researched topics. The present... 相似文献
59.
Sergiu Sima Julia Cruz-Doblas Martin Cismondi Catinca Secuianu 《Central European Journal of Chemistry》2014,12(9):918-927
The phase behavior of the carbon dioxide + cycloalkane mixtures usually receives low attention, though these systems are important for many industries, e.g. the carbon capture and storage. In this paper calculations results for the carbon dioxide + cyclopentane binary system are presented, based on SRK and PR cubic equations of state with classical van der Waals mixing rules. A single set of binary parameters for each model was proposed to predict the global phase behavior of the system in a wide range of pressure and temperature. Albeit the thermodynamic models used are simple, they are able to represent fairly well the phase behavior of the system analyzed in this paper. 相似文献
60.
Beigoli Sima Hekmat Azadeh Farzanegan Fahimeh Darroudi Majid 《Journal of Sol-Gel Science and Technology》2021,98(3):508-516
Journal of Sol-Gel Science and Technology - Considering the existing various sources that can supply the nano-biomaterials that are related to the Amorphous Calcium Phosphate (ACP) family, Aloe... 相似文献