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排序方式: 共有403条查询结果,搜索用时 15 毫秒
1.
Large eddy simulation of the free-shear flows has been performed using an algebraic subgrid stress model. The test cases considered are the temporal planar jet and mixing layer. The results are compared with that of the Smagorinsky, dynamic Smagorinsky, mixed models and the DNS data. For the mean flow quantities none of the models perform exceptionally better over the others. However, both the algebraic and mixed models predict better statistics for the turbulent quantities than the linear models. The results also demonstrate the capability of the algebraic model in depicting backscatter of energy explicitly, which is consistent in both the cases considered. 相似文献
2.
The counter current heat exchanger theory with periodic inlet temperatures has been applied to analyze the thermal performance of a water heating system. The theoretical results obtained are in agreement with the experimental data reported in the literature. 相似文献
3.
A theory has been proposed to evaluate the burning rate of a single carbon particle in a continuously operated coal-fired fluidized bed. Experimental verification was carried out in a laboratory scale 200 mm × 200 mm combustor. The burning rate increases with the increase of the fluidization velocity and the size of the bed material. The predicted data on burning rate agree fairly well with the experimental values. The gas concentration in the bed and freeboard has also been measured and it is seen that the consumption of oxygen mostly takes place in the bed. 相似文献
4.
Tip wear of silicon probes used for an atomic force microscope (AFM) is a critical issue. Wear can result in an increase of
tip radius and adhesion between tip and sample, thus reducing the image resolution and introducing artifacts. In order to
reduce adhesion, friction, and wear so as to reduce tip related artifacts, liquid lubricant (Z-TETRAOL), self-assembled monolayers
(pentafluorophenyltriethoxysilane (PFPTES)), and fluorocarbon polymer (Fluorinert™) were applied on the silicon probe. A comprehensive
investigation of adhesion, friction, and wear of the uncoated/coated tips in both ambient air and various humidity levels
as well as the influence of the coatings on the image resolution was performed. Experiments showed that the coatings reduced
the adhesion, friction, and wear of the silicon tip, improved the initial image resolution, and exhibited less deterioration
as compared to that of uncoated tip in the long-term test. 相似文献
5.
Healthy hair and skin is highly desired. Characterization of their morphological, frictional, and adhesive properties (tribological properties) is essential to enhance understanding of hair and skin and to advance the science. Literature on the tribological characterization of hair and skin is scarce to date. The paper presents nanotribological data and analysis on hair (Caucasian, Asian, and African hair at virgin, chemo-mechanically damaged, and treated conditions) and synthetic hair and skin, as well as roughness data of human skin replica. Roughness statistics are presented to characterize the vertical and spatial surface parameters. Average coefficient of friction values were determined for each ethnicity and hair type, and are discussed. The directionality dependence of friction is also discussed. Magnitude and spatial distribution of adhesive force are used to estimate thickness and distribution of the conditioner film. 相似文献
6.
We report on the development of an electrostatic ion trap for high-resolution mass spectrometry. The trap works on purely electrostatic fields and hence trapping and storing of ions is not mass restrictive, unlike other techniques based on Penning, Paul, or radio frequency quadrupole ion traps. It allows simultaneous trapping and studying of multiple mass species over a large mass range. Mass spectra were recorded in "dispersive" and "self-bunching" modes of ions. Storage lifetimes of about 100 ms and mass resolving power of about 20,000 could be achieved from the fifth harmonic Fourier transform spectrum of Xe ions recorded in the self-bunching mode. 相似文献
7.
Since the very first resolution of racemic tartaric acid by Pasteur, the importance of resolution and methodology has been on a path of continuous understanding and expansion. The science and chemistry of achieving such targets has changed a lot. The advent of chromatography changed the direction by involving synthetic, semisynthetic, or naturally occurring chiral materials for a direct approach to resolution, where rapid and reversible association occurs to form diastereomers with different stabilities and partition coefficients responsible for overall enantioseparation. It has now reached a stage where the separation of excess enantiomers from nonracemic mixtures has been achieved in a totally achiral environment, which does not appear to be in line with the prevalent concepts of basic stereochemistry. Caution should be exercised when enantiomerically enriched mixtures – obtained by enantioselective synthesis – are chromatographed for purification in preparative organic synthesis. 相似文献
8.
Surjyanarayan Mandal Snigdha Das Mandal Krishna Chuttani Krutika K Sawant Bharat Bhushan Subudhi 《Drug development and industrial pharmacy》2016,42(8):1340-1350
Background: The present study is to investigate the neuroprotective effect of ibuprofen by intranasal administration of mucoadhesive microemulsion (MMEI) against inflammation-mediated by dopaminergic neurodegeneration in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of Parkinson’s disease (PD).Methods: Ibuprofen-loaded polycarbophil-based MMEI was developed by using response surface methodology (RSM). Ibuprofen with dose of 2.86 mg/kg/day was administered intranasally to male C57BL/6 mice for two consecutive weeks which were pre-treated with four intraperitoneal injections of MPTP (20?mg/kg of body weight) at 2?h intervals. Immunohistochemistry was performed.Results: Optimal MMEI was stable and non-ciliotoxic with 66.29?±?4.15?nm as average globule size and??20.9?±?3.98?mV as zeta potential. PDI value and transmission electron microscopy result showed the narrow globule size distribution of MMEI. The result showed that all three independent variables had a significant effect (p?<?0.05) on the responses. Rota-rod and open-field test findings revealed the significant improvement in motor performance and gross behavioral activity of the mice. The results from in vivo study and immunohistochemistry showed that nasal administration of Ibuprofen significantly reduced the MPTP-mediated dopamine depletion. Furthermore TH neurons count in the substantia nigra and the density of striatal dopaminergic nerve terminals were found to be significant higher for ibuprofen treated groups.Conclusion: Findings of the investigation revealed that Ibuprofen through developed MMEI was shown to protect neurons against MPTP-induced injury in the Substantia nigra pars compacta (SNpc) and striatum and hence, could be a promising approach for brain targeting of Ibuprofen through intranasal route to treat PD. 相似文献
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10.
Microsystem Technologies - 相似文献