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101.
Slow flow of an incompressible Newtonian fluid across a fibrous porous medium bounded by a free-flow region of variable width was studied experimentally by magnetic resonance imaging velocimetry. The fibrous porous medium (fibre lattice) comprised of aligned rows of cylindrical rods, which were macroscopically arranged in a semi-circular fashion in a Hele-Shaw cell. The local aspects of the flow in the interior of and exterior to the fibre lattices were studied for (i) three individual semi-circular fibre lattices of different porosity and/or cylinder size, with each lattice bounded by an open channel and (ii) an assembly of five fibre lattices with the interstitial space between them forming a free-flow region. The symmetry (in a practical sense) of slow flow over symmetrical lattice-channel arrangements is demonstrated. The subtle characteristics of the flow within the lattices are seen as considerable local velocity enhancements (LVE) transverse to and in the direction of superficial flow. These LVE within the lattices strongly depend on the interface configuration of the lattice-channel arrangement, the gap size between the cylinders and the lattice porosity. The penetration depth of the LVE may even extend to the lattice centre. When a fibre lattice is a part of an assembly, the surface irregularities of neighbouring lattices create more complex tortuous flow pathways in the free-flow region. These pathways produce recurrent LVE within the fibre lattice. The implications that the above findings have for the flow, heat transfer and mass transfer in conceptually similar heterogeneous porous media used in, for example, liquid composite moulding processes and filtration processes are discussed. 相似文献
102.
Branko Brkljač Marko Janev Radovan Obradović Danilo Rapaić Nebojša Ralević Vladimir Crnojević 《Applied Intelligence》2014,41(3):956-973
The paper presents a novel precision matrix modeling technique for Gaussian Mixture Models (GMMs), which is based on the concept of sparse representation. Representation coefficients of each precision matrix (inverse covariance), as well as an accompanying overcomplete matrix dictionary, are learned by minimizing an appropriate functional, the first component of which corresponds to the sum of Kullback-Leibler (KL) divergences between the initial and the target GMM, and the second represents the sparse regularizer of the coefficients. Compared to the existing, alternative approaches for approximate GMM modeling, like popular subspace-based representation methods, the proposed model results in notably better trade-off between the representation error and the computational (memory) complexity. This is achieved under assumption that the training data in the recognition system utilizing GMM have an inherent sparseness property, which enables application of the proposed model and approximate representation using only one dictionary and a significantly smaller number of coefficients. Proposed model is experimentally compared with the Subspace Precision and Mean (SPAM) model, a state of the art instance of subspace-based representation models, using both the data from a real Automatic Speech Recognition (ASR) system, and specially designed sets of artificially created/synthetic data. 相似文献
103.
Rajeswari?Chandrasekaran Godfrey?Sikha Branko?N.?PopovEmail author 《Journal of Applied Electrochemistry》2005,35(10):1005-1013
A detailed analysis of the capacity fade of a battery/supercapacitor hybrid and a battery alone has been carried out at 55 °C by discharging them at three different pulse rates. The applied peak current amplitudes were 5C (7 A), 3C (4.2 A), and 1C (1.4 A), respectively. The results indicated that for hybrids the pulse discharge run time was extended for all pulse discharge rates. The ohmic resistances estimated as a function of the pulse discharge rates were smaller for hybrids when compared with those for batteries. The variation of the ohmic resistance under pulse discharge with cycling, irrespective of the pulse discharge rate was smaller for hybrids than that for the batteries. The batteries and hybrids cycled at the lowest pulse discharge rate (high pulse discharge time) have larger capacity fade when compared with the capacity fade of the batteries and the hybrids discharged using higher discharge rates (low pulse discharge time). Impedance, cyclic voltammogram, and the rate capability studies were carried out on batteries cycled alone and on batteries cycled as part of the hybrid. The battery showed larger increase in the interfacial impedance with cycling when compared with the hybrid system. 相似文献
104.
Miloš D. Tomić Branko Dunjić Jelena B. Bajat Violeta Likić Jelena Rogan Jasna Djonlagić 《Journal of Coatings Technology and Research》2016,13(3):439-456
The preparation of epoxy/clay nanocomposites (NCs) and their insertion into coatings are of great importance since the NCs could enhance the protective performances. In this study, epoxy NCs with 1–10 wt% of nanoclay Cloisite 30B (C30B) were prepared by the sonication-assisted solution method. The rheological measurements of epoxy/C30B suspensions revealed non-Newtonian, shear-thinning behavior of the uncured NCs, with an increase in the viscosity, yield stress, and shear modules with increasing organoclay content, while the dispersion effectiveness of C30B decreased. A significant enhancement of the rheological parameters was observed at the second percolation threshold (4.1 vol%) due to the formation of a continuous network of 45-layer-thick tactoids. Although NCs with 1–3 wt% C30B exhibited slightly reduced mechanical and adhesion properties compared with the cured reference epoxy resin, the epoxy primer and topcoat based on NC with 1 wt% C30B generally displayed improved impact resistance and maintained flexibility, pendulum hardness, and good adhesion properties. Two-layer coating systems, i.e., NC-based primers and topcoats, had higher corrosion stability in a salt spray chamber compared to the unmodified system. 相似文献
105.
Novel frameworks for the design of fault‐tolerant control using optimal sliding‐mode control 下载免费PDF全文
This paper describes 2 schemes for a fault‐tolerant control using a novel optimal sliding‐mode control, which can also be employed as actuator redundancy management for overactuated uncertain linear systems. By using the effectiveness level of the actuators in the performance indexes, 2 schemes for redistributing the control effort among the remaining (redundant or nonfaulty) set of actuators are constructed based on an ‐based optimal sliding‐mode control. In contrast to the current sliding‐mode fault‐tolerant control design methods, in these new schemes, the level of control effort required to maintain sliding is penalised. The proposed optimal sliding‐mode fault‐tolerant control design schemes are implemented in 2 stages. In the first stage, a state feedback gain is derived using an LMI‐based scheme that can assign a number of the closed‐loop eigenvalues to a known value whilst satisfying performance specifications. The sliding function matrix related to the particular state feedback derived in the first stage is obtained in the second stage. The difference between the 2 schemes proposed for the sliding‐mode fault‐tolerant control is that the second one includes a separate control allocation module, which makes it easier to apply actuator constraints to the problem. Moreover, it will be shown that, with the second scheme, we can deal with actuator faults or even failures without controller reconfiguration. We further discuss the advantages and disadvantages of the 2 schemes in more details. The effectiveness of the proposed schemes are illustrated with numerical examples. 相似文献
106.
This work demonstrates the possibility to use artificial neural networks (ANN) for the classification of white varietal wines. A multilayer perceptron technique using quick propagation and quasi-Newton propagation algorithms was the most successful. The developed methodology was applied to classify Slovak white wines of different variety, year of production and from different producers. The wine samples were analysed by the GC–MS technique taking into consideration mainly volatile species, which highly influence the wine aroma (terpenes, esters, alcohols). The analytical data were evaluated by means of the ANN and the classification results were compared with the analysis of variance (ANOVA). A good agreement amongst the applied computational methods has been observed and, in addition, further special information on the importance of the volatile compounds for the wine classification has been provided. 相似文献
107.
Jasmina Stojkovska Branko Bugarski Bojana Obradovic 《Journal of materials science. Materials in medicine》2010,21(10):2869-2879
Alginate hydrogels in forms of discs and packed beds of microbeads (~800 μm) were tested in a novel bioreactor at 10% strain
using two regimes: at a loading rate of 337.5 μm/s and at sequential increments of 50 μm displacement every 30 min. Compressive
strength increased with the increase in alginate concentration (1.5 vs. 2% w/w) and the content of guluronic residues (38.5
vs. 67%). Packed beds of microbeads exhibited significantly higher (~1.5–3.4 fold) compression moduli than the respective
discs indicating the effects of gel form and entrapped water. Short-term cultivation of microbeads with immobilized bovine
calf chondrocytes (1.5% w/w, 33 × 106 cells/ml) under biomimetic conditions (dynamic compression: 1 h on/1 h off, 0.42 Hz, 10% strain) resulted in cell proliferation
and bed compaction, so that the compression modulus slightly increased. Thus, the novel bioreactor demonstrated advantages
in evaluation of biomaterial properties and cell-biomaterial interactions under in vivo–like settings. 相似文献
108.
Zoran M. Miodragovi Goran A. Bogdanovi Bojana B. Kraj
inovi Branko J. Drakuli Vladan B. Kusigerski Djenana U. Miodragovi Vojislav V. Spasojevi Ismet M. Hodi Ivan O. Jurani 《Inorganic chemistry communications》2006,9(12):1173-1177
A new binuclear Cu(II) complex with an (E)-4-(2,4-diisopropylphenyl)-4-oxo-2-butenoato ligand (L) was successfully synthesized and characterized by elemental analysis and IR-spectroscopy. The structures of (E)-4-(2,4-diisopropylphenyl)-4-oxo-2-butenoic acid (HL), and the corresponding (tetrakis)-μ-[(E)-4-(2,4-diisopropylphenyl)-4-oxo-2-butenoato]-bis(ethanol)-copper(II) complex, [Cu2L4(C2H5OH)2], were determined by single crystal X-ray analyses and are preliminarily discussed. This is the first complex of a transition metal with ligand L, as well as the first determined crystal structure of a metal complex with this type of ligand. Analysis of the magnetic susceptibility measurements of the isolated [Cu2L4(C2H5OH)2] · H2O complex shows the existence of a strong anti-ferromagnetic intradimer coupling, with an exchange integral value 2J of −260 cm−1. 相似文献
109.
Stojanka Petrusic Maryline Lewandowski Stéphane Giraud Petar Jovancic Branko Bugarski Sanja Ostojic Vladan Koncar 《应用聚合物科学杂志》2012,124(2):890-903
This work refers to the synthesis and characterization of thermosensitive hydrogels based on interpenetrating polymer networks (IPNs) of poly(N‐isopropylacrylamide) (PNIPAAm) and calcium alginate in the form of films. The influence of the crosslinking degree of PNIPAAm and alginate content on thermal, swelling, mechanical, and morphological properties of hydrogels is investigated in detail. Characterization of pure PNIPAAm hydrogels and IPN hydrogels was performed by FTIR, DSC, DMA, and SEM. In addition, the studies of equilibrium swelling behavior as well as swelling, deswelling, and reswelling kinetics are performed. The results obtained imply the benefits of synthesizing IPNs based on PNIPAAm and calcium alginate over pure PNIPAAm hydrogels. The presence of calcium alginate contributes to the improvement of mechanical properties, the deswelling rate of hydrogels, and the network porosity, without altering the thermosensitivity of PNIPAAm significantly. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
110.