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61.
The thermal performance of variable cross-section fins is considered using the Maxwell–Cattaneo–Vernotte (MCV) heat conduction model. Four different fins, namely rectangular, triangular, convex, and concave fins, with a periodic thermal condition are examined. The governing equations are hyperbolic and are solved numerically using an implicit finite difference method. In the MCV model, the thermal wave propagates with a finite speed, and hence sharp discontinuities appear in the temperature profiles. In this study, temperature profiles at various times, heat transfer rates, and thermal efficiencies of Fourier and non-Fourier fins are presented. In addition, the effect of relaxation time is considered. The results show that the effects of cross-sectional area and relaxation time are considerable on the thermal performance of various non-Fourier fins. To validate our findings, the results for non-Fourier fins with constant cross-sectional area obtained from this study are compared to those of other numerical solutions. This comparison confirms the correctness of the current results. 相似文献
62.
Preparation of bis-aminothiazoles under different conditions including synthesis in EtOH under ultrasound irradiation and also in water in the presence of Fe(SD)3 as Lewis acid-surfactant-combined catalyst (LASC) under ultrasound irradiation has been studied. The results were compared with the traditional reflux method. Also, the results confirmed the efficiency of the synthesis in water and under ultrasound irradiation technique. Moreover, the antibacterial activity of products was investigated using the well-diffusion method against bacterial strains including Micrococcus luteus, Escherichia coli, Pseudomonas aeruginosa and Bacillus subtilis. All of the products showed good antibacterial activity against M. luteus and E. coli. Most of the products showed antibacterial activity higher than erythromycin against M. luteus, E. coli, and B. subtilis. 相似文献
63.
Hassan Rezazadeh Hossein Arabalibeik Fateme Alipour Pezhman Pasyar Vahid Sadeghi 《Contact lens & anterior eye》2018,41(6):489-495
Purpose
To introduce a method for estimation of the rigid gas-permeable contact lens (RGP) movement.Materials and methods
Videos captured from normal blinking of keratoconus patients while wearing RGP lenses were used for this study. The videos are recorded using the CCD camera of a smart phone attached to the eyepiece of the slit lamp. The algorithm starts with extracting two frames of the video related to the highest and lowest positions of the lens during blinking, followed by an appropriate edge detection method. In the next step circular Hough transform is used to find the center of lens and to segment it in each image. Finally the lens movement is estimated by measuring vertical displacement of the lens center between these two frames.Results
Mean and standard deviation of the difference between real movement and results of the algorithm for 20 cases are ?8.66% and 10.71% respectively. The results are highly correlated with Pearson coefficient 0.986?P?<?0.001. Bland-Altman plot with 95% levels of agreement (LoA) shows an agreement between exact manual measurement method and the proposed algorithm.Conclusion
The proposed algorithm shows a relatively high accuracy as the first attempt and compared to the routine qualitative visual estimation. Considering the importance of the lens movement, although this system was not tested on a series of RGP fitting patients yet, semi-automatic measurement may potentially help practitioners decide the appropriate RGP lens fit and reduce the fitting time. 相似文献64.
Wang X Azimi H Mack HG Morana M Egelhaaf HJ Meixner AJ Zhang D 《Small (Weinheim an der Bergstrasse, Germany)》2011,7(19):2793-2800
The effect of the additive 1,8-octanedithiol (ODT) on the nanometer-scale morphology and local photophysical properties of low-bandgap polymer blends of poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b'] dithiophene)- alt-4,7(2,1,3-benzothiadiazole)] (PCPDTBT) and [6,6]-phenyl C(61) -butyric acid methyl ester (PCBM) is investigated. Phase separations of the PCPDTBT:PCBM blend film induced by ODT are visualized by the morphological changes from fibril-shaped features to spherical bumps, by the dramatically increased photoluminescence emission from PCPDTBT that was originally largely quenched, and by the fluctuations of spectral features at different locations of the sample surface. The correlations between the morphology and the local photophysical properties of the blend film with/without ODT at both the micrometer and nanometer scales are revealed by confocal and high-resolution near-field spectroscopic mapping techniques. 相似文献
65.
Chahrokh Azimi Pierre Desvarreux Yves Guerpillon Françoise Keime 《Bulletin of Engineering Geology and the Environment》1982,25(1):143-150
Bulletin of Engineering Geology and the Environment - La détermination des propriétés mécaniques de sols tels qu'éboulis, dépôts glaciaires qui sont non... 相似文献
66.
Azimi S Rocher V Muller M Moilleron R Thevenot DR 《The Science of the total environment》2005,337(1-3):223-239
Total atmospheric deposition, i.e., both wet and dry deposition, was sampled during 11 months in the "Ile-de-France" region, France. Monthly fluxes of aliphatic hydrocarbons (AHs), polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs) were studied at three representative sites (two urbanised and one semiurban). A combination of spatial and temporal variability of total fluxes and pollutant fingerprints allows a better understanding of atmospheric pollutant dynamics over this region. In the whole studied area, aggregated total atmospheric fluxes of AHs, PAHs and HMs range from 19 to 33 mg m(-2) y(-1), 99 to 161 mug m(-2) y(-1) and 48 to 103 mg m(-2) y(-1), respectively. The highest values are observed in Paris centre, reflecting the importance of the urban centre as a source of pollutants, with a decline in many atmospheric deposits when moving away from urban areas. The seasonal distribution of these pollutants suggests the impact of residential heating on urban atmospheric deposition of hydrocarbons and the increase of dust loads containing HMs during summer. The qualitative study performed on atmospheric deposition data highlights the main sources of pollutants. Aliphatic fingerprints suggest a marked contribution of biogenic inputs to aliphatic contamination in the whole Ile-de-France region and slight petroleum inputs in urban areas. Aromatic fingerprints, characterised by the great predominance of phenanthrene, fluoranthene and pyrene, associated with some specific ratio values, suggest the mixture of petrogenic and pyrolytic contaminations of atmospheric deposition in the whole "Ile-de-France" region. HM distribution shows the presence of anthropogenic sources of Al and Fe in this area and the stationary sources (incinerators and plants) as a significant source of Si, S and Sb in the urban atmosphere. Moreover, a pollutant mix phenomenon, occurring in such an urban atmosphere, shows a significant influence on atmospheric deposition at the semiurban site. 相似文献
67.
There has been a growing interest to model and analyze Vehicle-Bridge Interaction (VBI) of intricate vehicles on bridges. The objective of such an analysis is to realistically investigate the dynamic effects of moving vehicles particularly in case of high-speed trains, where the vehicle acceleration is a design criterion and should be calculated appropriately. One method of analysis is to eliminate the wheel degrees of freedom (DOF) that are in direct contact with the bridge surface resulting in a VBI element, which is a modified beam element acted upon directly by wheel(s) of a running vehicle. The contact force is the mutual force between the wheel and the bridge. The available formulation in the literature is used to formulate the contact forces, which are related to those in the beam element DOFs by the Hermitian interpolation functions. Considering suitable interpolation functions between the beam element displacement vector and those for contact points and also a new formulation for the contact points, a new formulation is proposed for the structural properties of the VBI element, resulting in a new element capable of capturing bridge and vehicle responses more realistically. A study is conducted on the model variables and their effects on the bridge dynamic amplification factor and also bridge and vehicle accelerations, in order to compare the new VBI method with the existing one. The studied parameters include vehicle and bridge damping, frequency parameter, system mass parameter, and a new parameter called vehicle mass parameter. Results generally demonstrate noticeable differences particularly for high speed vehicles. In addition, it is observed that the effect of shear deformations in a simply-supported bridge might not be negligible and should be considered for moving vehicle analysis. For double girder open-deck steel railway bridges, the difference in midspan deflection of models including or excluding shear deformation can vary from 18% to 8% for 4.0 m and 30.0 m spans, respectively, for a sample vehicle. 相似文献
68.
Gholam Hossein Shahverdizadeh Fateme Hakimi Babak Mirtamizdoust Aliakbar Soudi Pejman Hojati-Talemi 《Journal of Inorganic and Organometallic Polymers and Materials》2012,22(4):903-909
A novel Pb(II) complex, {[Pb2(tpmba)2(NO3)4]·MeOH} n (1), was obtained by the reaction of a tripodal ligand, N,N′,N″-tris(pyrid-3-ylmethyl)-1,3,5-benzenetricarboxamide (tpmba), with Pb(NO3)2. The structure of complex was determined by X-ray crystallography. The results of structural analysis of the complex reveal that 1 is a M2L2 cage-like with a methanol molecule beside the cage. An entirely different structure and topology between 1 and similar complexes indicate that the nature of organic ligands affects the structure of assemblies. The results indicate that the framework of this complex is predominated by the nature of the organic ligand, anions, solvent and geometric need of the metal ions. It was found that the coordination number of PbII ions is eight, (PbN3O5) has a stereo-chemically active electron lone pair and the coordination sphere is hemi-directed. PbO nanoparticles are obtained by thermolysis of 1 at 180 °C with oleic acid as a surfactant. Scanning electron microscopy shows that the size of the PbO particles is ~30 nm. 相似文献
69.
This study presents an optimization methodology and results for the structure of gas adsorbents at a pore level by evaluating the effect of pore geometry, size and overall adsorbent porosity on ultimate working capacity of adsorbents used in pressure swing adsorption (PSA) processes. Three model pore network topologies are studied: parallel, grid-like and branched structures. These are “near” optimal structures for an adsorbent particle and their relative performance is compared in a two-step PSA cycle. The macropore network of such structured adsorbents is optimized through maximization of an objective function i.e. working capacity WC, defined as the number of moles adsorbed per unit volume of slab. Molecular and Knudsen diffusion are considered as the sole transport mechanisms in the macropore channels. An unexpected finding of this optimization technique is that the branched structure with a porosity of less than 50% represents an optimum structure with highest working capacity for the system considered. Furthermore, for faster cycles the advantage of branched structures is more obvious, reflecting the advantages of the pore network in facilitating diffusion more efficiently than other structures. A macropore channel density (defined as the density of macropores per metre of external surface) of below 10 is suggested for optimum performance for both “fast” and “slow” PSA cycles. The theoretical results of this study will be used as a priori results for the design of adsorbents at the macro-scale (bed) level. 相似文献
70.
Ultraviolet disinfection is a physical method of disinfecting secondary treated wastewaters. Bioflocs formed during secondary treatment harbor and protect microbes from exposure to ultraviolet (UV) light, and significantly decrease the efficiency of disinfection at high UV doses causing the tailing phenomena. However, the exact mechanism of tailing and the role of biofloc properties and treatment conditions are not widely understood. It is hypothesized that sludge bioflocs are composed of an easily disinfectable loose outer shell, and a physically stronger compact core inside that accounts for the tailing phenomena. Hydrodynamic shear stress was applied to the bioflocs to peel off the looser outer shell to isolate the cores. Biofloc and core samples were fractionated into narrow size distributions by sieving and their UV disinfection kinetics were determined and compared. The results showed that for bioflocs, the tailing level elevates as the biofloc size increases, showing greater resistance to disinfection. However, for the cores larger than 45 μm, it was found that the UV inactivation curves overlap, and show very close to identical inactivation kinetics. Comparing bioflocs and cores of similar size fraction, it was found that in all cases cores were harder to disinfect with UV light, and showed a higher tailing level. This study suggests that physical structure of bioflocs plays a significant role in the UV inactivation kinetics. 相似文献