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111.
M. Shyam Sundar 《合成通讯》2014,44(24):3582-3593
A biphenyl-based ligand attached was synthesized and screened in copper-mediated Michael reaction. The catalyst system works well with carbon or sulfur nucleophiles as Michael donors and cyclohexenone or chalcones as the acceptors under mild and neutral reaction conditions in a chemoselective manner. 相似文献
112.
T. V. Sundar V. Parthasarathi K. Sarkunam M. Nallu B. Walfort H. Lang 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(7):o464-o466
The title compounds, C15H16ClN2O+·Br−·1.5H2O and C15H16BrN2O+·Br−·1.5H2O, are isomorphous. The benzene ring is oriented nearly normal to the pyridine ring in both compounds. The molecular packing is mainly influenced by intermolecular O—H⋯O and O—H⋯Br interactions, as well as weak intramolecular C—H⋯O interactions. The H2OBr− units form an extended water–bromide chain, with a bridging water molecule on a twofold axis. 相似文献
113.
Gaurangi Gogoi Ching Thian Moi Anindya Sundar Patra Devipriya Gogoi Peela Nageswara Rao Mohammad Qureshi 《化学:亚洲杂志》2019,14(24):4607-4615
One of the major limiting factors for efficient photoelectrochemical water oxidation is the fast recombination kinetics of photogenerated charge carriers. Herein, we propose a model system that utilizes ZnIn2S4 and hierarchical VS2 microflowers for efficient charge separation through a Z‐scheme pathway, without the need for an electron mediator. An impressive 18‐fold increase in photocurrent was observed for ZnIn2S4–VS2 compared to ZnIn2S4 alone. The charge‐transfer dynamics in the composite were found to follow a Z‐scheme pathway, which resulted in decreased charge recombination and greater accumulation of the surface charge. Furthermore, slow kinetics of the surface reaction in the ZnIn2S4–VS2 composite correlated to an increased surface‐charge capacitance. This feature of the composite material facilitated partial storage of the photogenerated charge carriers (e?/h+) under illumination and dark‐current conditions, thus storing and utilizing solar energy more efficiently. 相似文献
114.
Excimer laser decoating of chromium titanium aluminium nitride to facilitate re-use of cutting tools
M. Sundar D. Whitehead P.T. Mativenga L. Li K.E. Cooke 《Optics & Laser Technology》2009,41(8):938-944
This work reports on the technical feasibility and establishment of a process window for removing chromium titanium aluminium nitride (CrTiAlN) coating from steel substrates by laser irradiation. CrTiAlN coating has high hardness and oxidation resistance, with applications for use with cutting tools. The motivation for removing such coatings is to facilitate re-use of tooling by enabling regrinding or reshaping of a worn tool and hence promote sustainable material usage. In this work, laser decoating was performed using an excimer laser. The effect of laser fluence, number of pulses, frequency, scanning speed and laser beam overlap on the decoating performance was investigated in detail. The minimum threshold laser fluence for removing the CrTiAlN coating was lower than that of the steel substrate and this factor is beneficial in controlling the decoating process. Successful laser removal of CrTiAlN coating without noticeable damage to the steel substrate was demonstrated. 相似文献
115.
Positron lifetime has been measured as a function of temperature in Sidoped GaAs single crystals subjected to various heat
treatments. Defects produced by these heat treatments trap positrons. In all the GaAs samples containing defects positron
lifetime was found to decrease with temperature in the range from 375 K to 16 K. The decrease is explained as due to the decrease
in the trapping rate. The trapping rate is mainly controlled by the diffusion of the positron to the trap. The diffusion constant
is determined mainly by the scattering from charged Si impurities. 相似文献
116.
This paper reports the performance studies of Nd:YAG rods with different diameters and doping concentration in the CW diode-side-pumped geometry. We have used p-polarized diodes to pump the active medium and we studied the performance of different rods in terms of thermal lensing, its fluorescence profile, power output, and M2 factor of the laser beam. We achieved a maximum of 378 W of output power for an input pump power of 757 W, which corresponds to optical conversion efficiency close to 50%. The slope efficiency of the system was 56.4%. These efficiencies are the highest reported to the best of our knowledge and we achieved with Nd:YAG rod at 1.1-at% doping. 相似文献
117.
A stochastic partial differential equation in which the square root of the solution appears as the diffusion coefficient
is studied as a particular case of stochastic evolution equations. Weak existence of a solution is proved by the Euler approximation
scheme. The super-Brownian motion on [0, 1] is also studied as a Hilbert-space-valued equation. In this set up, weak existence,
pathwise uniqueness, and positivity of solutions are obtained in any dimension d .
Accepted 23 October 1998 相似文献
118.
Ghulam Mohmad Subhajit Sarkar Ashmita Biswas Kingshuk Roy Dr. Ramendra Sundar Dey 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(55):12664-12673
The design and synthesis of metal-free catalysts with superior electrocatalytic activity, high durability, low cost, and under mild conditions is extremely desirable but remains challenging. To address this problem, a polymer-assisted electrochemical exfoliation technique of graphite in the presence of an aqueous acidic medium is reported. This simple, cost-effective, and mass-scale production approach could open the possibility for the synthesis of high-quality nitrogen-doped graphene–polypyrrole (NG-PPy). The NG-PPy catalyst displays an improved half wave potential (E1/2=0.77 V) in alkaline medium compared with G-PPy (E1/2=0.66 V). Most importantly, this catalyst demonstrates excellent stability with high methanol tolerance, and it outperforms the commercial Pt/C catalyst and other previously reported metal-free catalysts. The content of graphitic nitrogen atoms is the key factor for the enhancement of electrocatalytic activity towards oxygen reduction reactions (ORR). Interestingly, the NG-PPy catalyst can be used as a cathode material in a zinc–air battery, which demonstrates a higher peak power density (59 mW cm−2) than G-PPy (36.6 mW cm−2), highlighting the importance of the low-cost material synthesis approach towards the development of metal-free efficient ORR catalysts for fuel cell and metal–air battery applications. Remarkably, the polymer-assisted electrophoretic exfoliation of graphite with a high yield (≈88 wt %) of few-layer graphene flakes could pave the way towards the mass production of high-quality graphene for a variety of applications. 相似文献
119.
Anirudh Pradhan Shyam Sundar Kumhar 《International Journal of Theoretical Physics》2009,48(5):1466-1477
The present study deals with spatially homogeneous and locally rotationally symmetric (LRS) Bianchi type II cosmological models
with bulk viscous fluid distribution of matter and decaying vacuum energy density Λ. To get the deterministic models of the
universe, we assume that the expansion (θ) in the model is proportional to the shear (σ). This leads to condition R=mS
n
, where R and S are metric potentials, m and n are constants. We have obtained two types of models of the universe for two different values of n. The vacuum energy density Λ for both models is found to be a decreasing function of time and it approaches a small positive
value at late time which is supported by recent results from the observations of (SN Ia). Some physical and geometric behaviour
of these models are also discussed. 相似文献
120.
Balabhaskar Balasundaram Shyam Sundar Chandramouli Svyatoslav Trukhanov 《Optimization Letters》2010,4(3):311-320
This article studies a degree-bounded generalization of independent sets called co-k-plexes. Constant factor approximation algorithms are developed for the maximum co-k-plex problem on unit-disk graphs. The related problem of minimum co-k-plex coloring that generalizes classical vertex coloring is also studied in the context of unit-disk graphs. We extend several
classical approximation results for independent sets in UDGs to co-k-plexes, and settle a recent conjecture on the approximability of co-k-plex coloring in UDGs. 相似文献