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91.
Dinesh Patidar Kuldeep S. Rathore Kananbala Sharma T.P. Sharma 《Journal of Modern Optics》2013,60(18):3041-3047
A thin film of zinc selenide (ZnSe) was deposited onto a clean glass substrate using a vacuum evaporation technique. This thin film was characterized through X-ray diffraction, which indicated that the film was polycrystalline in nature. Absorption and transmission spectra of this thin film were recorded using a spectrophotometer. The energy band gap, refractive index and extinction coefficient were determined using these spectra. It was found that the energy band gap of ZnSe film was 2.55 eV. It was also observed that the refractive index and extinction coefficient of the film decreased with the increase of wavelength. The conductivity of this thin film was determined by current–voltage measurement using an electrometer over the temperature range from room temperature to 413 K. It was observed that conductivity increased with increase in temperature. This is explained on the basis of structural changes occurring due to the change in grain size and the increase in carrier density. 相似文献
92.
Lin LC Berger AH Martin RL Kim J Swisher JA Jariwala K Rycroft CH Bhown AS Deem MW Haranczyk M Smit B 《Nature materials》2012,11(7):633-641
One of the main bottlenecks to deploying large-scale carbon dioxide capture and storage (CCS) in power plants is the energy required to separate the CO(2) from flue gas. For example, near-term CCS technology applied to coal-fired power plants is projected to reduce the net output of the plant by some 30% and to increase the cost of electricity by 60-80%. Developing capture materials and processes that reduce the parasitic energy imposed by CCS is therefore an important area of research. We have developed a computational approach to rank adsorbents for their performance in CCS. Using this analysis, we have screened hundreds of thousands of zeolite and zeolitic imidazolate framework structures and identified many different structures that have the potential to reduce the parasitic energy of CCS by 30-40% compared with near-term technologies. 相似文献
93.
In order to identify the essential structural features and physicochemical properties for acetylcholinesterase (AChE) inhibitory activity in some carbamate derivatives, the systematic QSAR (Quantitative Structure Activity Relationship) studies (CoMFA, advance CoMFA and CoMSIA) have been carried out on a series of (total 78 molecules) taking 52 and 26 molecules in training and test set, respectively. Statistically significant 3D-QSAR (three-dimensional Quantitative Structure Activity Relationship) models were developed on training set molecules using CoMFA and CoMSIA and validated against test set compounds. The highly predictive models (CoMFA q(2)=0.733, r(2)=0.967, predictive r(2)=0.732, CoMSIA q(2)=0.641, r(2)=0.936, predictive r(2)=0.812) well explained the variance in binding affinities both for the training and the test set compounds. The generated models suggest that steric, electrostatic and hydrophobic interactions play an important role in describing the variation in binding affinity. In particular the carbamoyl nitrogen should be more electropositive; substitutions on this nitrogen should have high steric bulk and hydrophobicity while the amino nitrogen should be electronegative in order to have better activity. These studies may provide important insights into structural variations leading to the development of novel AChE inhibitors which may be useful in the development of novel molecules for the treatment of Alzheimer's disease. 相似文献
94.
Suvarcha Chauhan Kundan Sharma Kuldeep Kumar Girish Kumar 《Journal of surfactants and detergents》2014,17(1):161-168
Densities (d) and sound velocities (v) of an ethoxylated alkyl phenol surfactant in aqueous solutions of two amino acids, namely glycine and leucine, have been measured over a temperature range of 25–40 °C at intervals of 5 °C by using density and sound analyzers. Experimental data have been used to calculate the isentropic compressibilities (κs), apparent molar volumes (?v) and apparent molar adiabatic compressions (?κ) in order to explain amino acid–surfactant interactions. The results have been discussed in terms of the effect of amino acids on the micellization behavior of the surfactant. A comparative study of both the amino acids has been carried out and is found that both amino acids produce a decrease in the CMC value of nonionic surfactant but to different extents. 相似文献
95.
A methodology is proposed for the characterization of fire resistive materials with respect to thermal performance models. Typically in these models, materials are characterized by their densities, heat capacities, thermal conductivities, and any enthalpies (of reaction or phase changes). For true performance modelling, these thermophysical properties need to be determined as a function of temperature for a wide temperature range from room temperature to over 1000°C. Here, a combined experimental/theoretical/modelling approach is proposed for providing these critical input parameters. Particularly, the relationship between the three‐dimensional microstructure of the fire resistive materials and their thermal conductivities is highlighted. Published in 2005 by John Wiley & Sons, Ltd. 相似文献
96.
Richard G. Gann Anthony Hamins Kevin McGrattan Harold E. Nelson Thomas J. Ohlemiller Kuldeep R. Prasad William M. Pitts 《Fire Technology》2013,49(3):679-707
The National Institute of Standards and Technology (NIST) conducted an extensive investigation of the collapse of the three tall World Trade Center (WTC) buildings. A central part of this investigation was the reconstruction and understanding of the initiation and spread of the fires. This paper describes the reconstruction of the fires, the thermal environment they created within the buildings, and the raising of the temperatures of the structural components. NIST analyzed thousands of documents, interviews, photographs, and videos to obtain information on the layout of the floors and the progress of the fires. Experiments provided information on the factors likely to have determined the fire growth. Simulations using the Fire Dynamics Simulator gave good agreement with the fire spread as observed at the windows. Imposition of the probable thermal environment on the structural steel produced maps of the probable temperature profile of the steel as the fires progressed. For WTC 1 and WTC 2, even in the vicinity of the fires, it was unlikely that the columns and floor trusses with intact insulation heated to temperatures where significant loss of strength occurred. This was in part due to the short time between aircraft impact and building collapse. There were regions of the towers in which the loss of structural strength of floors and columns, whose insulation had been damaged by aircraft impact, was likely. For WTC 7, even though the insulation was intact, the long periods of heating resulted in floor components whose temperatures exceeded 600°C, but columns did not exceed 300°C. 相似文献
97.
Joginder Paul Sumit Bhardwaj Kuldeep Kumar Sharma Ravinder Kumar Kotnala Ravi Kumar 《Journal of Materials Science》2014,49(17):6056-6066
We present the structural, dielectric, ferroelectric, magnetic and magnetoelectric studies of lead free; single phase Bi4?x Sm x Ti3?x Co x O12?δ (0 ≤ x ≤ 0.07) ceramics, synthesized using a standard solid-state reaction technique. Raman spectroscopy analysis reveals the relaxation of distortion in TiO6 octahedron. Field emission scanning electron microscopy confirmed the growth of plate-like grains. It is observed that with the substitution of Sm3+ and Co3+ ions the dielectric constant, loss tangent and ferroelectric transition temperature decreases. Electrical dc resistivity, remnant polarization and magnetization increases with increasing Sm3+ and Co3+ contents. The magnetoelectric coupling co-efficient, α = 0.65 mV cm?1 Oe?1 is realized for Bi4?x Sm x Ti3?x Co x O12?δ (x = 0.07) ceramic sample. Our results clearly demonstrate the lead free, multiferroic nature of Sm/Co-substituted Bi4Ti3O12, which may find useful application in designing cost-effective electromagnetic devices. 相似文献
98.
A Comparative Study on the Aggregation and Thermodynamic Properties of Anionic Sodium Dodecylsulphate and Cationic Cetyltrimethylammonium Bromide in Aqueous Medium: Effect of the Co-solvent N-Methylacetamide 下载免费PDF全文
Suvarcha Chauhan Kuldeep Kumar Dilbag S. Rana Rajender Kumar Mohinder S. Chauhan 《Journal of surfactants and detergents》2016,19(1):193-200
The effect of co‐solvent N‐methylacetamide (NMA) (0.035, 0.046, 0.127, and 0.258 mol kg?1) on the micellization behaviour of anionic surfactant sodium dodecylsulphate (SDS) (3.21–10.35 mmol kg?1) and cationic surfactant cetyltrimethylammonium bromide (CTAB) (0.19–3.72 mmol kg?1) in aqueous solution was explored by employing conductivity measurements at different temperatures (298.15–313.15 K). The critical micelle concentration (CMC) values for SDS and CTAB in aqueous solutions of NMA were determined from the conductivity versus surfactant concentration plots. The variations in the CMC values of SDS with NMA concentration are in striking contrast to those observed in the case of CTAB. The various relevant thermodynamic parameters of micellization, viz. standard enthalpy change, ΔHmo, standard entropy change, ΔSmo, and standard Gibbs free energy change, ΔGmo, were determined using the temperature variation of the CMC values and counterion binding. The results not only relate these thermodynamic parameters to the consequences of intermolecular interactions but are also able to differentiate between SDS–water–NMA and CTAB–water–NMA systems in terms of contributions from head groups as well as alkyl chains of surfactants. 相似文献
99.
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