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21.
Despite the importance of air–oil slug flows to many industrial applications, their available data reported in the literature are limited compared to air–water slug flows. The main objective of the present study is to explain how air–oil slug flow parameters can be experimentally investigated using hot-film anemometry, capacitance sensors and image processing. Experiments were performed using air–oil slug flow through a horizontal pipe for air superficial velocities ranged from 0.01 m/s to 0.65 m/s and oil superficial velocities ranged from 0.03 m/s to 2.3 m/s. The signal obtained from the hot-film anemometer was used to determine the time-averaged local void fraction and liquid velocity and turbulence intensity for air–oil slug flow. The capacitance signals along with the data obtained by image processing of the flow were used to determine the elongated bubble length and velocity. The measurements techniques used found to describe in detail the internal structure of the slug flow. Finally, the experimental results were compared to existing models and correlations. 相似文献
22.
Manoj Kumar Chandra Mohan Sang Kyun Shim June Key Lee Nakwon Jang Naesung Lee Wael Z. Tawfik 《Molecules (Basel, Switzerland)》2021,26(13)
The far ultraviolet C (UVC) light sources based on carbon nanotube (CNT) field emitters as excitation sources have become promising light sources for sterilization, disinfection, and water purification. However, the low light extraction efficiency of UVC–CNT light sources still hinders the practical application of these structures. Herein, we report an optimized aluminum (Al) reflector to enhance the light extraction efficiency of UVC–CNT light sources. Optical analysis of UVC-CNT light sources covered by the Al reflectors with various thicknesses ranging from 30 to 150 nm was performed to realize the optimized reflector. The UVC-CNT light sources exhibit the highest light extraction efficiency when the Al reflector layer has an optimized thickness of 100 nm. For comparison, the cathodoluminescence (CL) spectra were recorded for UVC–CNT light sources with and without the optimized Al reflector. The measured light output power and the estimated power efficiency of the UVC–CNT light-source-tube with Al reflector were enhanced by about 27 times over the reference. This enhancement is mainly attributed to the outstanding reflection effect of the Al reflector. 相似文献
23.
Selim G. Akl 《BIT Numerical Mathematics》1982,22(2):129-134
The convex hull of a finite set of points in the plane can be computed in constant time using a polynomial number of processors.This work was supported by the Natural Sciences and Engineering Research Council of Canada under Grant NSERC - A3336. 相似文献
24.
In this article, we study the energy decay rate for an elastic Timoshenko system. This system consists of two coupled wave equations. Only the equation about the rotation angle is damped by one locally distributed feedback at the neighbourhood of the boundary. The equation for the transverse displacement of the beam is only indirectly damped through the coupling. First, we establish an exponential energy decay rate in the case of the same speed of propagation. Next, when the wave speeds are different, a polynomial-type decay rate is obtained. These results are proved by verifying the frequency domain conditions. 相似文献
25.
Sarah A. Alkhalaf Ahmed R. Ramadan Christian Obuekwe Ashraf M. El Nayal Nasser Abotalib Wael Ismail 《Molecules (Basel, Switzerland)》2021,26(14)
We followed a comparative approach to investigate how heavy vacuum gas oil (HVGO) affects the expression of genes involved in biosurfactants biosynthesis and the composition of the rhamnolipid congeners in Pseudomonas sp. AK6U. HVGO stimulated biosurfactants production as indicated by the lower surface tension (26 mN/m) and higher yield (7.8 g/L) compared to a glucose culture (49.7 mN/m, 0.305 g/L). Quantitative real-time PCR showed that the biosurfactants production genes rhlA and rhlB were strongly upregulated in the HVGO culture during the early and late exponential growth phases. To the contrary, the rhamnose biosynthesis genes algC, rmlA and rmlC were downregulated in the HVGO culture. Genes of the quorum sensing systems which regulate biosurfactants biosynthesis exhibited a hierarchical expression profile. The lasI gene was strongly upregulated (20-fold) in the HVGO culture during the early log phase, whereas both rhlI and pqsE were upregulated during the late log phase. Rhamnolipid congener analysis using high-performance liquid chromatography-mass spectrometry revealed a much higher proportion (up to 69%) of the high-molecularweight homologue Rha–Rha–C10–C10 in the HVGO culture. The results shed light on the temporal and carbon source-mediated shifts in rhamonlipids’ composition and regulation of biosynthesis which can be potentially exploited to produce different rhamnolipid formulations tailored for specific applications. 相似文献
26.
Wael A. A. Arafa 《Journal of heterocyclic chemistry》2019,56(4):1403-1412
A series of non‐heme Mn‐complexes has been synthesized by the sonication of manganese (II)chloride and bis‐amides (condensation products of 2‐picolinic acid and o‐phenylenediamines). The Mn‐complexes effectively promote the oxidation of unactivated aliphatic and benzylic C─H and N‐bearing heterocycles substrates with low catalyst loading using eco‐friendly hydrogen peroxide in the presence of acetic acid as additive under ultrasonic irradiation. Chromatographic studies revealed that the corresponding ketones are the only detectable products. Noteworthy, the presence of electron donors in the catalyst structure significantly increased the reaction yields. The substantial lowering of the oxidation reaction yields by adding ionol (2,6‐di‐tert‐butyl‐4‐methylphenol) as a free radical trap suggesting a free radical reaction pathway. 相似文献
27.
Elhelw Mohamed El-Maghlany Wael M. 《Journal of Thermal Analysis and Calorimetry》2020,140(5):2563-2573
Journal of Thermal Analysis and Calorimetry - An evaluation of using a thermal storage system utilized with air conditioning cycle in Egypt is the main aim of this paper. This study includes the... 相似文献
28.
Wael A. El-Sayed Mahmoud M. M. Ramiz Adel A.-H. Abdel-Rahman 《Monatshefte für Chemie / Chemical Monthly》2008,139(12):1499-1505
New C-furyl glycosides were synthesized in order to increase the number of compounds screened for antimicrobial activity. The antimicrobial
activity showed that the bromo as well as the nitro derivatives were the most active compounds.
Correspondence: Adel A.-H. Abdel-Rahman, Faculty of Science, Department of Chemistry, Menoufia University, Shebin El-Koam,
Egypt. 相似文献
29.
Mamdouh W Kelly RE Dong M Kantorovich LN Besenbacher F 《Journal of the American Chemical Society》2008,130(2):695-702
A novel supramolecular nanostructure formed by the coadsorption of the complementary nucleobases guanine (G) and uracil (U) at the liquid (1-octanol solvent)/solid (graphite) interface is revealed by scanning tunneling microscopy (STM). The GU supramolecular structure is distinctly different from the structures observed by STM when the individual nucleobases (NB) are adsorbed on graphite in the control experiments. Using a systematic methodology and ab initio density functional theory (DFT), an atomistic structural model is proposed for the supramolecular coadsorbed GU structure, which consists of a periodic repetition of cyclic units based on the strongest GU base pairing. 相似文献
30.
Anirudra Parajuli Daniel H. Kwak Luca Dalponte Dr. Niina Leikoski Tomas Galica Ugochukwu Umeobika Dr. Laurent Trembleau Andrew Bent Prof. Kaarina Sivonen Matti Wahlsten Dr. Hao Wang Dr. Ermanno Rizzi Prof. Gianluca De Bellis Prof. James Naismith Prof. Marcel Jaspars Prof. Xinyu Liu Dr. Wael Houssen Dr. David Peter Fewer 《Angewandte Chemie (International ed. in English)》2016,55(11):3596-3599
Cyanobactins are a rapidly growing family of linear and cyclic peptides produced by cyanobacteria. Kawaguchipeptins A and B, two macrocyclic undecapeptides reported earlier from Microcystis aeruginosa NIES‐88, are shown to be products of the cyanobactin biosynthetic pathway. The 9 kb kawaguchipeptin (kgp) gene cluster was identified in a 5.26 Mb draft genome of Microcystis aeruginosa NIES‐88. We verified that this gene cluster is responsible for the production of the kawaguchipeptins through heterologous expression of the kgp gene cluster in Escherichia coli. The KgpF prenyltransferase was overexpressed and was shown to prenylate C‐3 of Trp residues in both linear and cyclic peptides in vitro. Our findings serve to further enhance the structural diversity of cyanobactins to include tryptophan‐prenylated cyclic peptides. 相似文献