排序方式: 共有49条查询结果,搜索用时 15 毫秒
31.
W. Aslam Farooq Muhammad Sajjad Ul Hasan Muhammad Iftikhar Khan Ahmad Raza Ashraf Muhammad Abdul Qayyum Nafeesah Yaqub Mona A. Almutairi Muhammad Atif Atif Hanif 《Molecules (Basel, Switzerland)》2021,26(5)
A series of cobalt-inserted copper zinc ferrites, Cu0.6CoxZn0.4−xFe2O4 (x = 0.0, 0.1, 0.2, 0.3, 0.4) having cubic spinel structure were prepared by the coprecipitation method. Various characterization techniques, including XRD, FTIR, UV-vis and I–V were used to investigate structural optical and electrical properties, respectively. The lattice constant was observed to be decreased as smaller ionic radii Co2+ (0.74 Å) replaced the higher ionic radii Zn2+ (0.82 Å). The presence of tetrahedral and octahedral bands was confirmed by FTIR spectra. Optical bandgap energy was determined in the range of 4.44–2.05 eV for x = 0.0 to 0.4 nanoferrites, respectively. DC electrical resistivity was measured and showed an increasing trend (5.42 × 108 to 6.48 × 108 Ω·cm) with the addition of cobalt contents as cobalt is more conductive than zinc. The range of DC electrical resistivity (108 ohm-cm) makes these nanomaterials potential candidates for telecommunication devices. 相似文献
32.
Ibad Ali Khan Atif Saeed Alzahrani Shahid Ali Muhammad Mansha Muhammad Nawaz Tahir Majad Khan Hafiz Adil Qayyum Safyan Akram Khan 《Chemical record (New York, N.Y.)》2024,24(1):e202300171
The global rapid transition from fossil fuels to renewable energy resources necessitates the implementation of long-duration energy storage technologies owing to the intermittent nature of renewable energy sources. Therefore, the deployment of grid-scale energy storage systems is inevitable. Sulfur-based batteries can be exploited as excellent energy storage devices owing to their intrinsic safety, low cost of raw materials, low risk of environmental hazards, and highest theoretical capacities (gravimetric: 2600 Wh/kg and volumetric: 2800 Wh/L). However, sulfur-based batteries exhibit certain scientific limitations, such as polysulfide crossover, which causes rapid capacity decay and low Coulombic efficiency, thereby hindering their implementation at a commercial scale. In this review article, we focus on the latest research developments between 2012–2023 to improve the separators/membranes and overcome the shuttle effect associated with them. Various categories of ion exchange membranes (IEMs) used in redox batteries, particularly polysulfide redox flow batteries and lithium-sulfur batteries, are discussed in detail. Furthermore, advances in IEM constituents are summarized to gain insights into different fundamental strategies for attaining targeted characteristics, and a critical analysis is proposed to highlight their efficiency in mitigating sulfur cross-shuttling issues. Finally, future prospects and recommendations are suggested for future research toward the fabrication of more effective membranes with desired properties. 相似文献
33.
A. Qayyum M.N. Akhtar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(1):181-184
Light emission during sputtering of graphite targets with 1–10 keV Ne+, Kr+ and Xe+ beams has been investigated in the 180-600 nm wavelength range. Beside the characteristic lines of sputtered C1 and C1
+, a continuum superimposed with a number of broad structures was observed in the 250-520 nm range, and having a maximum at
386 nm. Mass analysis of the sputtered flux confirmed the presence of negative carbon clusters C
m
-
, C2
- being the dominant one. Ion beam parameters i.e. ion mass, energy, current density and ion dose were varied to identify the origin of the continuum emission. On the basis
of the experimental results, it is suggested that the continuum is predominantly due to the overlapping of various band systems
of sputtered C2 with a small contribution from the heavier sputtered carbon clusters Cm (m>2).
Received 24 September 1999 and Received in final form 11 February 2000 相似文献
34.
Sumaira Qayyum Tasawar Hayat Sumaira Jabeen Ahmed Alsaedi 《Mathematical Methods in the Applied Sciences》2020,43(9):5657-5672
Research on optimization of entropy generation in nanofluid flow gained much interest. In this study, the Walter's-B nanofluid flow is considered to analyze the irreversibility in cubic autocatalysis. Fluid motion is considered in presence of viscous dissipation, magnetohydrodynamics (MHD), radiation, and heat generation absorption. Homotopy analysis method (HAM) is employed to solve nonlinear ordinary differential system. Results show that fluid flow reduces for larger Weissenberg and Hartman numbers. Temperature gradually enhances for larger Weissenberg number and radiation parameter. For higher estimation of thermophoresis parameter, the temperature and concentration are enhanced. Opposite impact of Hartman and Weissenberg numbers is noticed for entropy generation and Bejan number. Disorderedness and Bejan number are reduced near the sheet, while the opposite trend is seen away from the sheet. 相似文献
35.
Integration with weight functions is used in countless mathematical problems such as: approximation theory and spectral analysis, statistical analysis and the theory of distributions. The aim of this paper is to establish a new inequality using weight function which generalizes the inequalities of Barnett et al. in 2001 and Rafiq et al. in 2006. We also discuss some other interesting inequalities in special cases. Perturbed midpoint and trapezoid inequalities are also obtained. Some applications in numerical integration are also given. 相似文献
36.
Kretschmer WP Meetsma A Hessen B Schmalz T Qayyum S Kempe R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(35):8969-8978
Aminopyridinato-ligand-stabilized organoyttrium cations are accessible in very good yield through alkane elimination from trialkyl yttrium complexes with sterically demanding aminopyridines, followed by abstraction of one of the two alkyl functions using ammonium borates. At 80 degrees C and in the presence of small amounts of aluminum alkyl compounds, very high ethylene polymerization activities are observed if very bulky aminopyridinato ligands are used. During these polymerizations a reversible polyethylene chain transfer is observed between the organoyttrium cations and aluminum alkyls. The chain-transfer catalyst system described here is able to produce relatively long-chain (up to 4000 g mol-1) Al-terminated polyethylene with a molecular-weight distribution<1.1. In the synthesis of higher molecular PE a slight increase in polydispersity with increasing chain length (15,600 g mol-1, approximately 1.4) is observed owing to reduced reversibility caused by higher viscosity and precipitation of polymer chains (temperature of 80-100 degrees C). 相似文献
37.
38.
Liu Z Qayyum MF Wu C Whited MT Djurovich PI Hodgson KO Hedman B Solomon EI Thompson ME 《Journal of the American Chemical Society》2011,133(11):3700-3703
We demonstrate a new approach for utilizing CuI coordination complexes as emissive layers in organic light-emitting diodes that involves in situ codeposition of CuI and 3,5-bis(carbazol-9-yl)pyridine (mCPy). With a simple three-layer device structure, pure green electroluminescence at 530 nm from a Cu(I) complex was observed. A maximum luminance and external quantum efficiency (EQE) of 9700 cd/m(2) and 4.4%, respectively, were achieved. The luminescent species was identified as [CuI(mCPy)(2)](2) on the basis of photophysical studies of model complexes and X-ray absorption spectroscopy. 相似文献
39.
Determination of pharmacokinetics of flurbiprofen in Pakistani population using modified HPLC method
Pharmacokinetics of flurbiprofen has been studied in different populations, especially in Caucasian. However, there are very few studies reported from Eastern part of world. Previous studies suggested that genetic and environmental factors may cause inter-individual differences in flurbiprofen disposition, so we investigated the pharmacokinetics of flurbiprofen in Pakistani subjects. A single oral dose of 100 mg of flurbiprofen was administered to 22 healthy male Pakistani adults after overnight fasting for 10 h. Periodical blood sampling was done at 0.25, 0.5, 0.75, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 10, 12, and 24 h after dosing. Plasma concentration of flurbiprofen was determined by a modified high-performance liquid chromatography method, which was simple, sensitive, less time consuming and economical with ordinary internal standard. The method was validated according to ICH guidelines and was found to be sensitive, accurate and precise. The pharmacokinetic parameters observed in Pakistani subjects when compared with other populations (USA, UK, Canadian, French, and Indian) did not show considerable ethnic differences. However, one subject's data was suggestive of being poor metabolizer of flurbiprofen which supports the presence of CYP2C9 polymorphism contributing to inter-individual differences in flurbiprofen disposition. Pharmacogenomic studies are needed to verify this hypothesis. 相似文献
40.