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401.
Zirconium phosphonates layered structure (ZPLS) materials with various organic pendant groups have been synthesized. Their
physical properties were investigated by means of SEM, BET, XRD, TGA/DTA and FT-IR. These properties, crystallinity in particular,
depended strongly on preparation conditions and the nature of the pendant. In general, samples with a sulfonic acid pendant
were not as crystalline as the carboxylic acid analogs. Crystalline samples exhibited a plate-like morphology as commonly
observed for layered structure materials. Interlayer spacing of these materials was roughly proportional to the size of the
pendant. In comparison with a conventional cation exchanged resin (Amberlyst 15), the layered structures with a sulfonic acid
pendant showed similar IR characteristics, but much better thermal stability. 相似文献
402.
A stochastic model representing the state of the catalyst surface is developed for several possible reaction mechanisms. With
the pseudo-steady state assumption, the fresh catalyst solution was used for the initial value of deactivating system The
deactivation functions obtained from the present study shows a good agreement with the model proposed by Nam and Froment[1].
When the reaction requires more than one site, the reaction becomes structure sensitive. However, for a single site reaction
requiring one site only, the reaction belongs to the class of structure-insensitive reaction Deactivation reactions can also
be classified by this manner. 相似文献
403.
B. N. Gikal S. N. Dmitriev G. G. Gul’bekyan S. L. Bogomolov O. N. Borisov V. A. Buzmakov I. A. Ivanenko N. Yu. Kazarinov I. V. Kalagin I. V. Kolesov A. I. Papash S. V. Pashchenko A. V. Tikhomirov M. V. Khabarov 《Atomic Energy》2007,103(6):946-956
An accelerator complex has been developed on the basis of the DTs-60 cyclotron for performing scientific and applied research
and for commercial application in nanotechnology. The complex was designed and constructed at the Laboratory of Nuclear Reactions
of the Joint Institute for Nuclear Research for the Interdisciplinary Scientific and Research Center at the L. N. Gumelev
Eurasian National University (Kazakhstan). Intense beams of heavy ions of Ne, Ar, Kr, and other elements have been obtained
and accelerated in the cyclotron. Various polymer films have been irradiated and several control batches of track membranes
have been prepared in a wide range of densities of the openings. The complex is a unifying factor in the development of technologies,
science, and science-intensive business and is intended for producing track filters, developing commercial technologies using
nano-and microstructures based on nuclear membranes and for creating a scientific environment in Kazakhstan.
__________
Translated from Atomnaya énergiya, Vol. 103, No. 6, pp. 357–364, December, 2007. 相似文献
404.
The management of resources has been claimed to be as important as scheduling methods. Inefficiency in managing resources may bring about severe delays and cost overruns caused by resource shortages in some cases and/or idle resources in others. Therefore, resources should be utilized efficiently to prevent project failures. Resource leveling is one of the approaches that are used for the management of resources. It aims to minimize fluctuations, peaks, and valleys in resource utilization without changing the completion time of a project and the number of resources required. Although the main principle behind traditional resource leveling is achieving an even flow of resources while the original project duration remains unchanged, the literature supports the need to develop an efficient model that discriminates among the activities that are selected for participation in resource leveling. For this purpose, this study has developed a model that considers the float consumption rates of activities in resource leveling. The float consumption rate is the percentage that is set to determine the maximum amount of float which will be consumed to shift the start time of the activity. The proposed model allows a scheduler to assign float consumption rates to each activity that can be used during the resource leveling procedure. When the required information is inputted, the proposed model automatically changes the required daily resources as it shifts the noncritical activities along their available total float times. The proposed model is expected to minimize the likelihood of severe delays and cost overruns. The model is demonstrated by constructing a network and its resource utilization histograms. 相似文献
405.
ABSTRACTThe present study involved the preparation of ibuprofen-containing controlled release tablets formulated from either the established granular product, Ethocel®Standard Premium, or the novel finely-milled product, Ethocel®Standard FP Premium. The tablets were prepared by either direct compression or wet granulation. The aim was to explore the influence of different parameters on the kinetics and mechanisms of ibuprofen release from the tablets. These parameters were; polymer particle size, polymer molecular weight, drug : polymer ratio, preparation methodology and partial replacement of lactose with the coexcipient—hydroxypropyl methylcellulose (HPMC). The derived drug release data were analyzed with reference to various established mathematical models while the f2-metric technique was used in order to determine profile equivalency. It was found that drug release was mostly modulated by several interactive factors apparently exhibiting crosstalk. Nevertheless, it was possible to identify some simple rules. Incorporation of Ethocel® FP polymers and application of the wet granulation technique facilitated greater efficiency in controlling ibuprofen release behavior from the matrices. Furthermore, drug release profiles could be modulated by partial substitution of the primary excipient with HPMC. Polymer concentrations and particle sizes, rather than viscosity grade, were found to be decisive factors in controlling drug release rates. 相似文献
406.
Muhammad Atif Makhdoom Muhammad Kamran Gul Hameed Awan Sehrish Mukhtar 《Metallurgical and Materials Transactions A》2013,44(12):5505-5512
Shielded metal arc welding was applied to AISI 1045 medium carbon steel. The microstructural changes and electrochemical corrosion behavior of the heat-affected zone (HAZ), base metal (BM), and weld zone (WZ) were investigated. The effect of welding passes on microstructural changes of BM, HAZ, and WZ were elucidated using optical microscopy, potentiodynamic Tafel scan, and linear polarization resistance (LPR) methods in plain water and 3.5 pct (w/v) NaCl solution under standard temperature and pressure using corrosion kinetic parameters. From microstructural observations, the variations in ferrite morphology in the BM and WZ showed dissimilar electrochemical corrosion behavior and a corrosion rate than that of HAZ. 相似文献
407.
Erum Pervaiz I. H. Gul Humaira Anwar 《Journal of Superconductivity and Novel Magnetism》2013,26(2):415-424
This paper presents a low temperature (130 and 160 °C) synthesis route to prepare the spinel phase CoFe2O4 nanoparticles and nanorods. A one-dimensional (1-D) structure of Co-ferrite was successfully synthesized using Cetyl Trimethyl Ammonium Bromide (CTAB) as a surfactant at temperature 160 °C. Structural, electrical, and magnetic measurements have been performed using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), and the Vibrating Sample Magnetometer (VSM). XRD patterns show a pure spinel (fcc) structure, showing a complete phase formation at a low temperature of 160 °C, without any subsequent sintering. Average crystallite sizes have been calculated by Sherrer’s and Williamson-Hall methods. As prepared CoFe2O4 nanorods exhibited a uniform shape of diameter 60–80 nm and 600–900 nm in length. The FTIR spectrum for Co-ferrite nanorods shows two intrinsic lattice absorption bands for tetrahedral and octahedral sublattices. DC electrical resistivity of CoFe2O4 nanorods is high up to ~108 (Ω-cm), as compared to CoFe2O4 nanoparticles (~107 Ω-cm) at 373 K. Dielectric parameters were measured using a LCR meter, in the frequency range of 1 kHz to 5 MHz. The real and imaginary part of the dielectric constant (ε′ and ε″) and dielectric loss tangent (tanδ) reduces for CoFe2O4 nanorods in comparison to nanoparticles, and has a value of 13.6 and 0.0416, respectively. Magnetic properties were characterized by VSM under a field of 10 kOe and showed that the 1-D structure reduces the magnetization of nanocrystalline CoFe2O4 from 65 emu/gm to 54 emu/gm. 相似文献
408.
Khan Noureen Amir Rahman Gul Nguyen Tung M. Shah Anwar Ul Haq Ali Pham Cham Q. Tran Minh Xuan Nguyen Dang Le Tri 《Topics in Catalysis》2023,66(1-4):149-181
Topics in Catalysis - Carbon emission from burning fossil fuels associated with anthropogenic activities has caused severe environmental issues and extreme weather events linked to human-induced... 相似文献
409.
Khan S Kazi TG Kolachi NF Baig JA Afridi HI Shah AQ Kumar S Shah F 《Journal of hazardous materials》2011,190(1-3):738-743
The distribution of vanadium (V) species in soil (test soil), vegetables and grasses, collected from the vicinity of a thermal power plant has been studied. For comparison purpose soil (control soil), same vegetable and grass samples were collected from agricultural land devoid of any industrial area. A simple and efficient ultrasonic assisted extraction method has been developed for the extraction of V(5+) species from soil, vegetable and grass samples using Na(2)CO(3) in the range of 0.1-0.5 mol/L. For comparison purpose same sub samples were also extracted by conventional heating method. The total and V species were determined by electrothermal atomic absorption spectrometry using different modifiers. The validity of V(5+) and V(4+) determination had been confirmed by the spike recovery and total amount of V by the analysis of CRM 1570 (spinach leave) and sub samples of agricultural soil. The concentration of total V was found in the range of 90-215 and 11.4-42.3 μg/g in test and control soil samples, respectively. The contents of V(5+) and total V in vegetables and grasses grown around the thermal power plant were found in the range of 2.9-5.25 and 8.74-14.9 μg/g, respectively, which were significantly higher than those values obtained from vegetables and fodders grown in non exposed agricultural site (P<0.01). Statistical evaluations indicate that the sum of concentrations of V(5+) and V(4+) species was not significantly different from total concentration of V in same sub samples of vegetable, grass and soil of both origins, at 95% level of confidence. 相似文献
410.
Imdad Ullah Ahmad Naveed Afzal Shah Amin Badshah Zia-ur-Rehman Gul Shahzada Khan Arif Nadeem 《Journal of surfactants and detergents》2014,17(2):243-251
Two new cationic surfactants, N-(dodecanoyl(ethylammonio)carbonothioyl)-N-ethylbenzenaminium bromide and N-(dodecanoyl(ethylammonio)carbonothioyl)-N-ethyl-N-phenylbenzenaminium bromide were synthesized with a high yield by the reaction of appropriate amounts of lauryl chlorides, potassium thiocyanate, amine and alkyl halides. The structures were characterized by 1H-NMR, 13C-NMR, FTIR and UV–Vis spectroscopy. Cyclic, square wave and differential pulse voltammetry were used to investigate the electrochemical fate of both surfactants over a wide pH range. 相似文献