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361.
Graça Marques Gonçalves Luís Gouveia Margarida Vaz Pato 《Annals of Operations Research》2014,219(1):141-167
In this paper the authors address a pressurized water distribution network design problem for irrigation purposes. Two mixed binary nonlinear programming models are proposed for this NP-hard problem. Furthermore, a heuristic algorithm is presented for the problem, which considers a decomposition sequential scheme, based on linearization of the second model, coupled with constructive and local search procedures designed to achieve improved feasible solutions. To evaluate the robustness of the method we tested it on several instances generated from a real application. The best solutions obtained are finally compared with solutions provided by standard software. These computational experiments enable the authors to conclude that the decomposition sequential heuristic is a good approach to this difficult real problem. 相似文献
362.
Henriques VB Germano R Lamy MT Tamashiro MN 《Langmuir : the ACS journal of surfaces and colloids》2011,27(21):13130-13143
Aqueous dispersions of phosphatidylglycerol (PG) lipids may present an anomalous chain-melting transition at low ionic strengths, as seen by different experimental techniques such as calorimetry or light scattering. The anomaly disappears at high ionic strengths or for longer acyl-chain lengths. In this article, we use a statistical model for the bilayer that distinguishes both lipid chain and headgroup states in order to compare model and experimental thermotropic and electrical properties. The effective van der Waals interactions among hydrophobic chains compete with the electrostatic repulsions between polar headgroups, which may be ionized (counterion dissociated) or electrically neutral (associated with counterions). Electric degrees of freedom introduce new thermotropic charge-ordered phases in which headgroup charges may be spatially ordered, depending on the electrolyte ionic strength, introducing a new rationale for experimental data on PGs. The thermal phases presented by the model for different chain lengths, at fixed ionic strength, compare well with an experimental phase diagram constructed on the basis of differential scanning calorimetry profiles. In the case of dispersions of DMPG (dimyristoyl phosphatidylglycerol) with added monovalent salt, the model properties reproduce the main features displayed by data from differential scanning calorimetry as well as the characteristic profile for the degree of ionization of the bilayer surface across the anomalous transition region, obtained from the theoretical interpretation of electrokinetic (conductivity and electrophoretic mobility) measurements. 相似文献
363.
N. Drichko S. Kaiser R. Shewmon J. Eckstein M. Dressel M. Matos R. T. Henriques M. Almeida 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,78(3):283-289
The optical properties of the one-dimensional organic conductor (perylene)2Pt(mnt)2 and its Au analogue have been investigated at ambient and low temperatures. The spectra along the stacks of the molecules
show a simple Drude behavior with no detectable influence of electron-electron interactions. Basing on the spectra for different
polarizations an assignment of the vibrational modes is made.
Perpendicular to the stacks, a wide band observed in the mid-infrared range evidences a charge transfer between perylene and
anion stacks. The electronic properties are discussed in comparison with other quasi-one-dimensional synthetic metals. 相似文献
364.
Studies of a classical III–V semiconductor (InSb) doped with 3d magnetic ions (Mn2+, having a localized spin S=55/2) reveal some unexpected transport properties. It is found that the transition from the metallic to the low-temperature
insulator phase occurs at an impurity concentration N
Mn∼N
cr=2× 1017 cm−3 and a temperature T<T
cr∼1 K. Under these conditions a giant negative magnetoresistance arises. The experimental results can be explained in terms
of the onset of a hard Mott-Hubbard gap Δ in the impurity band formed by the shallow manganese acceptor in InSb at N
Mn∼N
cr. A model describing the gap formation is proposed.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 5, 358–362 (10 March 1999)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
365.
Fatima M. Barreiros Paulo J. Ferreira M. Margarida Figueiredo 《Particle & Particle Systems Characterization》1996,13(6):368-373
It is well established that particle size and shape substantially influence the bulk properties of powdered materials. Although these characteristics are closely interrelated, the tendency has been to analyse the particle size independently from particle shape. The aim of this work was the assessment of particle shape through particle sizing data. For this purpose, three different particle shape materials – glass beads (spherical), crushed glass (moderately irregular) and mica (lamellar) – were tested, employing four particle sizers. The shape factor selected was the Wadell's sphericity, which was evaluated utilizing distinct equations. The comparison of the results reveals problems arising from the use of approximations rather than more fundamental equations. 相似文献
366.
Paulo J. Ferreira Sandra Matos Margarida M. Figueiredo 《Particle & Particle Systems Characterization》1999,16(1):20-24
The aim of this work was the characterisation of the primary components of papermaking pulp, i.e. fibres and fines. Although it included the measurement of fibre dimensions, this work was mainly devoted to sizing fines, applying methods other than those frequently used for pulp quality control. Therefore, in addition to the Kajaani method, image analysis, laser diffraction and the electrical sensing zone method were also utilised. A chemical pulp was tested before and after laboratory refining. Finally, an evaluation was made of the handsheet strength and optical properties prepared with these pulps, with and without fines, in order to study the effect of the beating process and of the fines. 相似文献
367.
Vieira Manuel V. C. Carvalho Margarida 《4OR: A Quarterly Journal of Operations Research》2023,21(3):491-512
4OR - Motivated by a real-world application, we present a multi-container loading problem with 3-open dimensions. We formulate it as a biobjective mixed-integer nonlinear program with lexicographic... 相似文献