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991.
Angelo Alessandri Simona Sacone Silvia Siri 《Journal of Mathematical Modelling and Algorithms》2007,6(1):109-133
The main objective of this paper consists in modelling, optimizing, and controlling container transfer operations inside intermodal
terminals. More specifically, maritime container terminals are here considered, involving three kinds of transportation modes,
i.e., maritime, rail, and road transport. Generally speaking, an intermodal port terminal can be seen as a system of container
flows with two interfaces, towards the hinterland and towards the sea, respectively. Moreover, inside a terminal, unloading
operations of inbound containers, container storage, and loading operations of outbound containers are carried out. A simple
model for maritime container terminals is proposed in this paper. In the model, a system of queues represents the standing
of containers and their movements inside the terminal. The dynamic evolutions of these queues are described by discrete-time
equations, where the state variables represent the queue lengths and the control variables take into account the utilization
of terminal resources such as load/unload handling rates. On the basis of the proposed model, an optimization problem is defined
that consists in minimizing the transfer delays of containers in the terminal. The problem is stated as an optimal control
problem whose solution is sought by adopting a receding-horizon strategy.
相似文献
992.
Gozzi A Ceolin L Schwarz A Reese T Bertani S Crestan V Bifone A 《Magnetic resonance imaging》2007,25(6):826-833
Pharmacological MRI (phMRI) methods have been widely applied to assess the central hemodynamic response to pharmacological intervention as a surrogate for changes in the underlying neuronal activity. However, many psychoactive drugs can also affect cardiovascular parameters, including arterial blood pressure (BP). Abrupt changes in BP or the anesthetic agents used in preclinical phMRI may impair cerebral blood flow (CBF) autoregulation mechanisms, potentially introducing confounds in the phMRI response. Moreover, relative cerebral blood volume (rCBV), often measured in small-animal phMRI studies, may be sensitive to BP changes even in the presence of intact autoregulation. We applied laser Doppler flowmetry and MRI to measure changes in CBF and microvascular CBV induced by increasing doses of intravenous norepinephrine (NE) challenge in the halothane-anesthetized rat. NE is a potent vasopressor that does not cross the blood-brain barrier and mimics the rapid BP changes typically observed with acute drug challenges. We found that CBF autoregulation was maintained over a BP range of 60-120 mmHg. Under these conditions, no significant central rCBV responses were observed, suggesting that microvascular rCBV changes in response to abrupt changes in perfusion pressure are negligible within the autoregulatory range. Larger BP responses were accompanied by significant changes in both CBV and CBF that might confound the interpretation of phMRI results. 相似文献
993.
Using an approach to analyze the theta dependence of systems with a theta term we recently proposed, the critical behavior of CP(10 at theta=pi is studied. We find a region outside the strong coupling regime where Haldane's conjecture is verified. The critical line, however, does not belong to the universality class of the Wess-Zumino-Novikov-Witten model at topological coupling k=1 since it shows continuously varying critical exponents. 相似文献
994.
995.
Moletti A Coluccini C Pasini D Taglietti A 《Dalton transactions (Cambridge, England : 2003)》2007,(16):1588-1592
The synthesis and characterization of the new chiral ligand 2, based on a BINOL-tren (tren = tris(2-aminoethyl)amine) conjugate, in enantiomerically pure form, are reported. UV-Vis spectrophotometric and spectrofluorimetric studies at variable pH show that the incorporation of a phenolic functionality in close proximity to the polyamino fragment of the molecule causes a dramatic variation of the acid-base and coordination properties of the molecule; the major role of this functionality in determining the selectivity observed in the complexation of Cu(2+), when compared with Zn(2+) and Ni(2+), at pH = 5 in aqueous MeOH, has been clarified, also by comparison with the spectroscopic and coordination properties of model compound 3, bearing protected OMe functionalities. The peculiar absorbance, emission and chiroptical properties of the binaphthyl fragment incorporated in compound 2 can be used for the selective detection of Cu(2+) using three different and potentially orthogonal techniques, namely UV, CD and fluorescence spectroscopies. 相似文献
996.
Amoroso AJ Coogan MP Dunne JE Fernández-Moreira V Hess JB Hayes AJ Lloyd D Millet C Pope SJ Williams C 《Chemical communications (Cambridge, England)》2007,(29):3066-3068
A series of lipophilic and hydrophilic fac tricarbonyl rhenium bisimine complexes have been prepared, their membrane-permeabilities explored in liposomes and their potential for application in fluorescence microscopy cell imaging demonstrated in the first application of MLCT-fluorescent rhenium complexes in cell imaging. 相似文献
997.
998.
Palocci C Barbetta A La Grotta A Dentini M 《Langmuir : the ACS journal of surfaces and colloids》2007,23(15):8243-8251
Highly porous, hydrophilic porous matrices were fabricated by using a high internal phase supercritical-CO2 (scCO2) emulsion templating technique. The novel aspect of the work resides in the combination of a natural biopolymer (dextran) as the building component of the matrices and of an environmentally benign solvent (supercritical-CO2) as the pore-generating phase. The synthetic route to the porous biomaterials involved the preliminary functionalization of the dextran chains with methacrylic moieties, formation of a scCO2-in-water concentrated emulsion, and curing of the external phase of the emulsion by radical polymerization. As the emulsion stabilizer a perfluoropolyether surfactant was chosen. The matrices obtained exhibit highly interconnected, trabecular morphologies. The porous biomaterial morphologies were qualitatively characterized by scanning electron microscopy (SEM) and the evaluation of void and interconnect sizes was carried out on the micrographs taken with the light microscope. To tailor the morphologies of the porous structures, the influence of the volume fraction of the internal phase and of the surfactant/internal phase ratio was investigated. It was established that the variation of the volume fraction of the internal phase exerted only a limited influence on void and interconnect sizes. On the contrary the increase of surfactant concentration alters dramatically the distribution of void size, a large proportion of the void space enclosed within the matrix being attributable to voids with a diameter exceeding 100 microm. The free toxic solvent process of fabrication of the porous structures, the high water content, the expected biocompatibility, and the mechanical properties that resemble natural tissues make these porous hydrogels potentially useful for tissue engineering applications. 相似文献
999.
Bonalumi N Vargas A Ferri D Baiker A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(33):9236-9244
The adsorption behavior of O-methyl and O-trimethylsilyl derivatives of cinchonidine (CD), employed as chiral modifiers for heterogeneous enantioselective hydrogenations on supported Pt catalysts, has been investigated by using attenuated total reflection infrared spectroscopy (ATR-IR) and density functional theory (DFT) electronic structure calculations. The ATR-IR spectroscopic investigation provided detailed insight of the adsorbed modifiers under conditions close to those employed during catalytic processes, and electronic structure calculations were used as a complement to the experiments to uncover the implications of conformational changes in generating the topology of the surface chiral site. The structural investigation of the adsorbed modifiers revealed a relationship between the spatial positions of the ether substituents and the enantiodifferentiation induced by the modified catalyst observed in the hydrogenation of alpha-activated ketones. Experiments and calculations corroborate a model, according to which the addition of a bulky ether group to CD reshapes the chiral sites, thus generating catalytic chiral surfaces with different and, in some cases (e.g. hydrogenation of ketopantolactone), even opposite enantioselective properties to those obtained with CD without altering the absolute configuration of the modifier. The study also confirms that active surface conformations of cinchona modifiers are markedly different from those existing in vacuum and in solution, thus underlying the necessity of investigating the surface-modifier interaction in order to understand enantioselectivity. 相似文献
1000.
Andrea Nobili Angelo Marcello Tarantino 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2007,58(1):137-160
In this paper, the deformation of a composite hard ferromagnetic-elastic beam-plate structure is investigated. A sandwich
structure, composed of two thin hard ferromagnetic layers, with a linear elastic layer in between, is considered. The deformation
is due to the self generated magnetic field (magnetostriction). The aim is to assess the interaction forces among the perfectly
bonded layers, through a consistent application of the classical nonlinear magneto-elastic theory. Once the general mechanical
model is stated, the analysis is specialized to study longitudinal elongation, given its great relevance in technical applications.
Owing to the non-local character of the magnetic action, a nonlinear integro-differential equation is derived. Some qualitative
properties of the solution are pointed out and the asymptotic behavior near the end sections is examined in detail. A finite
differences approach allows writing an approximating nonlinear system of equations in the non asymptotic part of the solution,
which is solved through a Newton’s iterative scheme. The numerical results are discussed and it is shown how the asymptotic
part of the solution well approximates the full behavior of the structure. Furthermore, the longitudinal interaction force
density is found to be singular at the end cross-sections, regardless of the assumed bonding type. 相似文献