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51.
Tertiary alcohols as well as primary and secondary benzylic alcohols react efficiently with nitriles to give the corresponding amides in good to excellent yields in the presence of P2O5/SiO2 (60% w/w). 相似文献
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Simple Approach to Predict Corrosion Inhibition Efficiency of Imidazole and Benzimidazole Derivatives as well as Linear Organic Compounds Containing Several Polar Functional Groups
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Mohammad Hossein Keshavarz Karim Esmaeilpour Ahmad Nozad Golikand Zeinab Shirazi 《无机化学与普通化学杂志》2016,642(16):906-913
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Jalil?Etminan Hengameh?Keshavarz Ravi?R.?MazumdarEmail author 《Wireless Networks》2016,22(8):2501-2509
Prior work has addressed the effects of multipath fading and path loss separately for broadcast and multiple-access channels. It has been shown that the number of simultaneously active users are of the order \(\Theta (\ln (\ln (n)))\) for random channel gains with exponentially-decaying tails, where n is the total number of users. Furthermore, it has been shown that assuming path loss is dominant and ignoring multipath fading, the user capacity (i.e. the maximum number of simultaneously active users in a wireless system) of multi-user channels is of the order \(\Theta (\ln (n))\) when the users are spatially distributed on the plane with a Gaussian or Uniform distribution. In this paper, we study the shadowing effects on the number of active users for broadcast and multiple-access channels in which the users are randomly distributed on the plane. It is shown that as the total number of users in the multi-user channel goes to infinity, the number of active users is of the order \(\Theta (\sqrt{\ln (n)}).\) 相似文献
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Seyyed Hamid Ahmadi Mohammad Hossein Keshavarz Hamid Reza Hafizi Atabak 《无机化学与普通化学杂志》2019,645(2):120-125
Plastic Bonded Explosives (PBXs) are explosive materials, in which sensitive explosive powders with high detonation performance are bound together in a matrix using small quantities of a synthetic polymer. They provide good thermal stability and improve cook‐off properties with negligible shrinkage. Laser‐induced breakdown spectroscopy (LIBS) has been introduced as a novel method for assessment of thermal aging in PBXs. Thermal aging of fifteen samples of PBXs with the same composition has been studied in two temperatures 60 and 70 °C for 5 period times during 29 d. Dynamical mechanical analysis (DMA) has also been done on different aged samples in order to validate the LIBS results. Among different molecular bands, LIBS data showed that the changes in line intensity in CN and AlO molecular radiations could be used to assess aging effects. Principle component analysis (PCA) chemometric method was also implemented in order to obtain more accurate discrimination between different samples. Since there is a good agreement for the outputs of LIBS data and DMA results, LIBS technique can be introduced a reliable method for assessment of thermal aging of PBXs. 相似文献
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Mohammad Peydayesh Gholam Reza Esfandyari Toraj Mohammadi Eskandar Keshavarz Alamdari 《Chemical Papers》2013,67(4):389-397
An experimental study on the removal of Cd2+ and Zn2+ through a supported liquid membrane using a mixture of mono-(2-etylhexyl) ester of phosphoric acid (M2EHPA) and bis-(2-etylhexyl) ester of phosphoric acid (D2EHPA) as carriers is presented. Parameters affecting the Cd2+ and Zn2+ pertraction such as feed concentration, carrier concentration, pH of the stripping phase, and TBP (tributyl phosphate) concentration were analyzed using the Taguchi method. Optimal experimental conditions for Cd2+ and Zn2+ pertraction were obtained using the analysis of variance (ANOVA) after a 6 h separation with the initial feed concentration of 8.9 × 10?4 mol L?1, carrier concentration of 20 vol. %, TBP concentration of 4 vol. %, and pH of 0.5. Then, under optimum conditions, a comparison of M2EHPA, D2EHPA, and bis-(2,4,4-trimethylpentyl)monothiophosphinic acid (Cyanex 302) was performed. Effective pertraction of Cd2+ and Zn2+ using these carriers was observed in the following order: mixture of M2EHPA and D2EHPA, D2EHPA, Cyanex 302. It was also found that the presence of one metal ion in the feed solution reduces the pertraction rate of the other one. 相似文献
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Rasool Keshavarz Masoud Movahhedi Abdolali Abdipour 《AEUE-International Journal of Electronics and Communications》2012,66(7):569-574
A new wideband asymmetric microstrip coupled-line coupler with 3 dB coupling value and quadrature phase difference is presented. Compared with the conventional edge-coupled couplers, this structure, consisting of two different transmission lines (interdigital and conventional microstrip transmission lines) as coupled lines, achieves wider operating bandwidth and larger coupling level. The coupled-line length of the proposed structure is approximately λg/4. To characterize the structure, an equivalent circuit model has been established. A 3 dB designed and fabricated coupler with 0.2 mm spacing between coupled lines exhibits an amplitude balance of 2 dB from 2.2 GHz to 4.2 GHz. Good agreements between the full-wave simulation and equivalent circuit model results has been achieved and verified the effectiveness of the proposed circuit model. Also, measurement results have been presented. 相似文献
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In this paper, a new numerical method for solving fractional differential equations is presented. The fractional derivative is described in the Caputo sense. The method is based upon Bernoulli wavelet approximations. The Bernoulli wavelet is first presented. An operational matrix of fractional order integration is derived and is utilized to reduce the initial and boundary value problems to system of algebraic equations. Illustrative examples are included to demonstrate the validity and applicability of the technique. 相似文献
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Mehdi Keshavarz Hedayati Franz Faupel Mady Elbahri 《Applied Physics A: Materials Science & Processing》2012,109(4):769-773
Metamaterials and plasmonics as a new pioneering field in photonics joins the features of photonics and electronics by coupling photons to conduction electrons of a metal as surface plasmons (SP). This concept has been implemented for a variety of applications including negative index of refraction, magnetism at visible frequency, cloaking devices amongst others. In the present work, we used plasmonic hybrid material in order to design and fabricate a broad-band perfect plasmonic metamaterial absorber in a stack of metal and Copper-PTFE (Polytetrafluoroethylene) nanocomposite showing an average absorbance of 97.5?% in the whole visible spectrum. Our experimental results showed that the absorption peak of the stacks can be tuned upon varying the thickness and type of the spacer layer due to the sensitivity of plasmon resonance to its environment. To the best of our knowledge, this is the first report of a plasmonic metamaterial absorber based on copper with absorption around 100?% in the entire visible and near-Infrared (NIR). 相似文献