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排序方式: 共有328条查询结果,搜索用时 15 毫秒
31.
32.
Esmail Vessally Akram Hosseinian Ladan Edjlali Ebrahim Ghorbani-Kalhor Rahim Hosseinzadeh-Khanmiri 《Journal of the Iranian Chemical Society》2017,14(11):2339-2353
Indole derivatives are an important class of heterocycle found in a large number of natural products and synthetic pharmaceuticals. Given the low cost and easy availability of N-propargyl anilines, synthesis of indole cores from these versatile structural motifs has attracted a lot of attention in the past decade. In this review, we summarize the most representative and interesting reports on this rapidly advancing area, with special emphasis on mechanistic aspects of the reactions. 相似文献
33.
Zal U��yun Wan Mahmood Che Abd Rahim Mohamed Zaharudin Ahmad Abdul Kadir Ishak 《Journal of Radioanalytical and Nuclear Chemistry》2011,287(1):255-260
A total of eight sediment cores with 50 cm length were taken in the Sabah and Sarawak coastal waters using a gravity corer in 2004 to estimate sedimentation rates using four mathematical models of CIC, Shukla-CIC, CRS and ADE. The average of sedimentation rate ranged from 0.24 to 0.48 cm year?1, which is calculated based on the vertical profile of 210Pbex in sediment core. The finding also showed that the sedimentation rates derived from four models were generally shown in good agreement with similar or comparable value at some stations. However, based on statistical analysis of paired sample t-test indicated that CIC model was the most accurate, reliable and suitable technique to determine the sedimentation rate in the coastal area. 相似文献
34.
Rahim MK Fukaminato T Kamei T Tamaoki N 《Langmuir : the ACS journal of surfaces and colloids》2011,27(17):10347-10350
The gliding motility of microtubules driven by kinesin on the surface of an azobenzene monolayer presenting lysine terminal groups is reversibly and repeatedly altered upon photoisomerization of the monolayer. 相似文献
35.
Hammond C Lopez-Sanchez JA Ab Rahim MH Dimitratos N Jenkins RL Carley AF He Q Kiely CJ Knight DW Hutchings GJ 《Dalton transactions (Cambridge, England : 2003)》2011,40(15):3927-3937
The reaction of glycerol with urea to form glycerol carbonate is mostly reported in the patent literature and to date there have been very few fundamental studies of the reaction mechanism. Furthermore, most previous studies have involved homogeneous catalysts whereas the identification of heterogeneous catalysts for this reaction would be highly beneficial. This is a very attractive reaction that utilises two inexpensive and readily available raw materials in a chemical cycle that overall, results in the chemical fixation of CO(2). This reaction also provides a route to up-grade waste glycerol produced in large quantities during the production of biodiesel. Previous reports are largely based on the utilisation of high concentrations of metal sulfates or oxides, which suffer from low intrinsic activity and selectivity. We have identified heterogeneous catalysts based on gallium, zinc, and gold supported on a range of oxides and the zeolite ZSM-5, which facilitate this reaction. The addition of each component to ZSM-5 leads to an increase in the reaction yield towards glycerol carbonate, but supported gold catalysts display the highest activity. For gold-based catalysts, MgO is the support of choice. Catalysts have been characterised by XRD, TEM, STEM and XPS, and the reaction has been studied with time-on-line analysis of products via a combination of FT-IR spectroscopy, HPLC, (13)C NMR and GC-MS analysis to evaluate the reaction pathway. Our proposed mechanism suggests that glycerol carbonate forms via the cyclization of a 2,3-dihydroxypropyl carbamate and that a subsequent reaction of glycerol carbonate with urea yields the carbamate of glycerol carbonate. Stability and reactivity studies indicate that consecutive reactions of glycerol carbonate can limit the selectivity achieved and reaction conditions can be selected to avoid this. The effect of the catalyst in the proposed mechanism is discussed. 相似文献
36.
This study reports the results of a numerical investigation of three-dimensional turbulent buoyant recirculating flow within
rooms with heated obstruction. The study involves the solution of partial differential equations for the conservation of mass,
momentum, energy, concentration, turbulent energy and its dissipation rate. These equations were solved together with algebraic
expressions for the turbulent viscosity and heat diffusivity using k-ε turbulence model by performing simulations on FLUENT
6.3. The CFD method was validated via comparing with the available experimental data. A comparison with experimental results
shows good agreement. This means that the present computer code has a good capability to simulate 3D airflow and effect of
obstruction within room. The present study demonstrates the flow behavior, thermal distribution and CO2 concentration inside the room in the presence of heat flux obstruction. Two different configurations of ventilation system
have been studied. Mixing and Displacement ventilation system have been used in two geometries depending on location of opening
inlet. The ventilation effectiveness for heat removal (ET) is used to evaluate the indoor climate and average temperature is an important parameter in designs the ventilation systems.
Two notable points are presented; first, mixing ventilation is depending on throw of jet. CO2 concentration and temperature distribution have been effected in upper zone more than occupied zone with presence the obstruction.
Second notable points are presented; in displacement ventilation buoyancy effect is considerable. Vertical temperature gradient
above the obstruction implies that both fresh air and CO2 concentration. 相似文献
37.
Wavelength tunable emitters and detectors in the mid-IR wavelength region allow applications including thermal imaging and
gas spectroscopy. One way to realize such tunable devices is by using a resonant cavity. By mechanically changing the cavity
length with MEMS mirror techniques, the wavelengths may be tuned over a considerable range. 相似文献
38.
Godwin Chidi Ugwunnadi Abdul Rahim Khan Mujahid Abbas 《Journal of Fixed Point Theory and Applications》2018,20(2):82
We introduce a hybrid proximal point algorithm and establish its strong convergence to a common solution of a proximal point of a lower semi-continuous mapping and a fixed point of a demicontractive mapping in the framework of a CAT(0) space. As applications of our new result, we solve variational inequality problems for these mappings on a Hilbert space. Illustrative example is given to validate theoretical result obtained herein. 相似文献
39.
E. Fazio E. Piperopoulos S.H. Abdul Rahim M. Lanza G. Faggio G. Mondio F. Neri A.M. Mezzasalma C. Milone S. Santangelo 《Current Applied Physics》2013,13(4):748-752
Pristine and annealed multi-walled C nanotubes are preliminarily tested as catalysts towards the degradation of p-coumaric acid with better performances than the widely used activated carbon. In order to clarify the origin of their different catalytic efficiency, the samples are analysed by means of high-resolution transmission electron microscopy, X-ray photoemission, reflection electron energy loss and micro-Raman spectroscopy. Chemical composition, mass density, bonding configurations and threefold- to fourfold-coordinated carbon bonding ratios are determined. The comparative discussion of the results obtained leads to attribute the higher catalytic activity of the pristine nanotubes to their larger sp2/sp3 carbon bonding fraction and greater amount of oxygen containing functional groups. 相似文献
40.
S. Schwarz C. G. Schaeffer A. Rahim J. Bruns K. Petermann 《Optical and Quantum Electronics》2013,45(7):775-781
The design of three different filter structures for the separation of 8 sub-channels in an optical OFDM system are compared. They are based on serial, serial-parallel and parallel filtering and can be realized as planar lightwave circuits. We investigate the tolerance towards phase errors in these structures using a Monte-Carlo simulation. 相似文献