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991.
Petr Svoboda Dagmar Svobodova Dagmar Merinska Toshiaki Ougizawa 《European Polymer Journal》2009,45(8):2434-2442
A blend of poly(ε-caprolactone) (PCL) and poly(styrene-co-acrylonitrile) (SAN) containing 27.5 wt% of acrylonitrile having the critical composition (80/20 PCL/SAN) was studied. This PCL/SAN blend having a lower critical solution temperature (LCST) phase boundary at 122 °C offered an excellent opportunity to investigate, firstly the kinetics of phase separation above LCST (125-180 °C), and secondly the kinetics of phase dissolution below LCST (50-115 °C). The blend underwent a temperature-jump above LCST where spinodal decomposition (SD) proceeded, yielding a regularly phase-separated structure (SD structure). Then, it was quenched to the temperatures below LCST when the phase dissolution proceeded. Optical microscopy was used to observe the spinodal decomposition qualitatively while light scattering was used to characterize the phase separation and phase dissolution quantitatively. It was found that during phase dissolution the peak maximum moved towards a smaller angle (wavelength of concentration fluctuations increased) while the peak intensity decreased. This behavior was explained by a model. Also it was found that the fastest phase dissolution kinetics at 80 °C, which was characterized by an apparent diffusion coefficient, was about 10 times slower than the kinetics of phase separation at 180 °C. 相似文献
992.
Petr Kučera 《Annali dell'Universita di Ferrara》2009,55(2):289-308
In this paper we deal with the system of the non-steady Navier–Stokes equations with mixed boundary conditions. We study the
existence and uniqueness of a solution of this system. Suppose that the system is solvable with some given data (the initial
velocity and the right hand side). We prove that there exists a unique solution of this system for data which are small perturbations
of the previous ones. 相似文献
993.
Maria Rosende Elena Yu. Savonina Petr S. Fedotov Manuel Miró Víctor Cerdà 《Talanta》2009,79(4):1081-1088
Dynamic fractionation has been recognized as an appealing alternative to conventional equilibrium-based sequential extraction procedures (SEPs) for partitioning of trace elements (TE) in environmental solid samples. This paper reports the first attempt for harmonization of flow-through dynamic fractionation using two novel methods, the so-called sequential injection microcolumn (SIMC) extraction and rotating coiled column (RCC) extraction. In SIMC extraction, a column packed with the solid sample is clustered in a sequential injection system, while in RCC, the particulate matter is retained under the action of centrifugal forces. In both methods, the leachants are continuously pumped through the solid substrates by the use of either peristaltic or syringe pumps.A five-step SEP was selected for partitioning of Cu, Pb and Zn in water soluble/exchangeable, acid-soluble, easily reducible, easily oxidizable and moderately reducible fractions from 0.2 to 0.5 g samples at an extractant flow rate of 1.0 mL min−1 prior to leachate analysis by inductively coupled plasma-atomic emission spectrometry.Similarities and discrepancies between both dynamic approaches were ascertained by fractionation of TE in certified reference materials, namely, SRM 2711 Montana Soil and GBW 07311 sediment, and two real soil samples as well. Notwithstanding the different extraction conditions set by both methods, similar trends of metal distribution were in generally found. The most critical parameters for reliable assessment of mobilisable pools of TE in worse-case scenarios are the size-distribution of sample particles, the density of particles, the content of organic matter and the concentration of major elements. For reference materials and a soil rich in organic matter, the extraction in RCC results in slightly higher recoveries of environmentally relevant fractions of TE, whereas SIMC leaching is more effective for calcareous soils. 相似文献
994.
An almost orthogonal comprehensive two-dimensional liquid chromatography was developed for the separation of phenolic and flavone natural antioxidants by using combinations of a polyethylene glycol silica micro-column in the first dimension and a porous-shell fused-core C18 column in the second dimension, both in the reversed-phase mode. System orthogonality was improved using parallel gradients of acetonitrile in buffered mobile phase. A new approach was proposed to optimize matching segmented gradient profiles in the two dimensions. An algorithm was developed for automatic corrections of the shifts in retention in the second dimension induced by the parallel two-dimensional gradient operation technique. Using the porous-shell C18 column in the second dimension at elevated temperature (60 degrees C) and high pressure (480 bar) with optimized segmented profiles of the parallel gradients in the two dimensions, the overall separation time for comprehensive LC x LC was reduced to 30 min. 相似文献
995.
996.
Robust static output feedback control was applied to a continuous stirred tank reactor with parametric uncertainty and multiple
steady states in which exothermic reaction takes place. The problem of robust controller design was converted to a solution
of linear matrix inequalities and a computationally simple non-iterative algorithm is presented. The possibility of using
robust static output feedback for stabilization of reactors with uncertainty and comparison of robust P and PI controllers
with an optimal controller is demonstrated by simulation results. 相似文献
997.
998.
The influence of different memory systems and associated attentional processes on the acuity of auditory images, formed for the purpose of making intonation judgments, was examined across three experiments using three different task types (cued-attention, imagery, and two-tone discrimination). In experiment 1 the influence of implicit long-term memory for musical scale structure was manipulated by varying the scale degree (leading tone versus tonic) of the probe note about which a judgment had to be made. In experiments 2 and 3 the ability of short-term absolute pitch knowledge to develop was manipulated by presenting blocks of trials in the same key or in seven different keys. The acuity of auditory images depended on all of these manipulations. Within individual listeners, thresholds in the two-tone discrimination and cued-attention conditions were closely related. In many listeners, cued-attention thresholds were similar to thresholds in the imagery condition, and depended on the amount of training individual listeners had in playing a musical instrument. The results indicate that mental images formed at a sensory/cognitive interface for the purpose of making perceptual decisions are highly malleable. 相似文献
999.
Marek M Schejbal M Kocí P Nevoral V Kubícek M Hadac O Schreiber I 《Chaos (Woodbury, N.Y.)》2006,16(3):037107
Early experimental observations of chaotic behavior arising via the period-doubling route for the CO catalytic oxidation both on Pt(110) and Ptgamma-Al(2)O(3) porous catalyst were reported more than 15 years ago. Recently, a detailed kinetic reaction scheme including over 20 reaction steps was proposed for the catalytic CO oxidation, NO(x) reduction, and hydrocarbon oxidation taking place in a three-way catalyst (TWC) converter, the most common reactor for detoxification of automobile exhaust gases. This reactor is typically operated with periodic variation of inlet oxygen concentration. For an unforced lumped model, we report results of the stoichiometric network analysis of a CO reaction subnetwork determining feedback loops, which cause the oscillations within certain regions of parameters in bifurcation diagrams constructed by numerical continuation techniques. For a forced system, numerical simulations of the CO oxidation reveal the existence of a period-doubling route to chaos. The dependence of the rotation number on the amplitude and period of forcing shows a typical bifurcation structure of Arnold tongues ordered according to Farey sequences, and positive Lyapunov exponents for sufficiently large forcing amplitudes indicate the presence of chaotic dynamics. Multiple periodic and aperiodic time courses of outlet concentrations were also found in simulations using the lumped model with the full TWC kinetics. Numerical solutions of the distributed model in two geometric coordinates with the CO oxidation subnetwork consisting of several tens of nonlinear partial differential equations show oscillations of the outlet reactor concentrations and, in the presence of forcing, multiple periodic and aperiodic oscillations. Spatiotemporal concentration patterns illustrate the complexity of processes within the reactor. 相似文献
1000.
Jiri A. Mares Petr Prusa Martin Nikl Karel Nitsch Alena Beitlerova Miroslav Kucera Martin Hanus Yurij Zorenko 《Radiation measurements》2010,45(3-6):369-371
Scintillating properties of Ce3+-doped (Lu,Y) aluminum garnet single crystalline films (SCF) were investigated. Thin SCF films of thickness between 1 and 30 μm were grown by a liquid phase epitaxy (LPE) method in various fluxes. The α-particle excitation (mainly 5.4857 MeV line of 241Am) of pulse height spectra is used to measure scintillation response of SCF, especially peak of those α-rays which are totally absorbed in the films. Detailed studies and evaluation of scintillation measurements of large sets of Ce3+-doped SCF (Lu,Y) aluminum garnets showed that at present time (i) YAG:Ce SCF have comparable scintillation properties as YAG:Ce single crystals, especially their Nphels photoelectron yields are the same while (ii) scintillation properties of LuAG:Ce SCF do not reach those of LuAG:Ce single crystal. 相似文献