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21.
Emmanuel Saridis Serafeim‐Dionysios Maroulas Marinos Pitsikalis 《Journal of polymer science. Part A, Polymer chemistry》2013,51(5):1162-1174
Various half‐titanocene complexes of the ATiCl2Nu type, where A is the pentamethylcyclopentadienyl (Cp*) or indenyl (Ind) group and Nu a nucleophile (ethoxy group or chloride), were used for the polymerization of L ‐lactide, LLA. In the cases where Nu is an ethoxy group, a 5% excess of ATiCl3 was used to accelerate the polymerization reaction. These systems were proven to be very efficient initiators for the ring‐opening polymerization (ROP) of LLA in toluene at 130 °C. Kinetic studies revealed that in most cases the polymerization yield was quantitative and the molecular weight increased linearly with time, leading to well‐defined PLLA with narrow molecular weight distributions (Mw/Mn ≤ 1.1). LLA was also polymerized by the in situ formation of the initiating system after mixing IndTiCl3, benzyl alcohol, BzOH, and NEt3. The thermal properties of the produced polymers were examined by differential scanning calorimetry and thermogravimetric analysis. The activation energy of the thermal decomposition was calculated by the Ozawa–Flynn–Wall and Kissinger methods. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
22.
Johannes Vassiliou Soulis 《国际流体数值方法杂志》1991,13(4):437-464
A marching finite volume method is presented for the calculation of two-dimensional, subcritical and supercritical, steady open channel flow including the usually neglected terms of slope and bottom friction. The channel flow will be assumed to be homogeneous, incompressible, two-dimensional and viscous with wind and Coriolis forces neglected. A hydrostatic pressure distribution is assumed throughout the flow field. The numerical technique used is a combination of the finite element and finite difference methods. A transformation is introduced through which quadrilaterals in the physical domain are mapped into squares in the computational domain. The governing system of PDEs is thus transformed into an equivalent system applied over a square grid network. Comparisons with other numerical solutions as well as with measurements for various open channel configurations show that the proposed approach is a comparatively accurate, reliable and fast technique. 相似文献
23.
Johannes Vassiliou Soulis 《国际流体数值方法杂志》1995,20(1):1-30
A time-marching finite volume numerical procedure is presented for three-dimensional Euler analysis of turbomachinery flows. The proposed scheme is applied to the conservative form of the Euler equations written in general curvilinear co-ordinates. A simple but computationally efficient grid is constructed. Numerical solution results for three 3D turbine cascade flows have been presented and compared with available measurements as well as with another state-of-the-art 3D Euler analysis numerical solution in order to demonstrate the accuracy and computational efficiency of the analysis method. Also, the predicted results are compared with a 3D potential flow solver and comparison is made with the analytical solution. The proposed method is an accurate and reliable technique for solving the compressible flow equations in turbomachinery geometries. 相似文献
24.
Evagelia D. Farsirotou Johannes V. Soulis Vassilios D. Dermissis 《International Journal of Computational Fluid Dynamics》2013,27(3):187-200
A fully coupled two-dimensional sub-critical and/or supercritical, free-surface flow numerical model is developed to calculate bed variations in alluvial channels. Vertically averaged free-surface flow equations in conjunction with sediment transport equation are numerically solved using an explicit finite-volume scheme in integral form. The capabilities of the proposed method are first demonstrated by analyzing supercritical flow in an expansion channel. Thereafter, one and two-dimensional applications referring to aggradation and scouring are reported. For each of these test cases, computed results compare satisfactorily with measurements as well as with other numerical solutions. The method is stable, reliable and accurate, although time consuming, handling a variety of sediment transport equations with rapid changes of sediment transport at the boundaries. 相似文献
25.
Dimitris Raptis John K. Kouinis Dionysios Kaminaris Andreas G. Galinos 《Monatshefte für Chemie / Chemical Monthly》1981,112(6-7):713-719
The preparationof etherates and pyridinium compounds of mixed complex iodoacids of Ga(III) is reported together with some physical and chemical properties, as well as conductometric measurements and the ultraviolet and infrared spectra of the new compounds. From the analytical, conductometric, stability and spectral data, some information is gained about the probable structure of the complexes.
Etherate und Pyridin-Verbindungen von gemischtkomplexen Jodosäuren von Gallium(III)
Zusammenfassung Es wird über die Darstellung von Ether- und Pyridiniumverbindungen gemischter komplexer Jodosäuren von Ga(III), sowie über einige physikalische und chemische Eigenschaften, konduktometrische Daten und die UV- und IR-Spektren dieser neuen Verbindungen berichtet. Auf Grund von analytischen, konduktometrischen, spektroskopischen und Stabilitätsbefunden wurden Informationen über die wahrscheinliche Struktur dieser Komplexe gewonnen.相似文献
26.
Foteini A. Kappi George Z. Tsogas Dimosthenis L. Giokas Dionysios C. Christodouleas Athanasios G. Vlessidis 《Mikrochimica acta》2014,181(5-6):623-629
We present two colorimetric procedures for the determination of cyanuric acid, using silver nanoparticle-based (AgNPs) probes. The first is making use of melamine-modified AgNPs which bind to cyanuric acid through hydrogen bonding to form a large conjugate network that enhances the aggregation of AgNPs to produce an absorbance peak at 640 nm and a green coloration. In the second assay, melamine is directly added to the sample in order to form a stable complex with cyanuric acid. AgNPs are then added, resulting in the formation of an absorbance peaking at 525 nm and a color change from green (blank sample) to purple or orange-red as a function of cyanuric acid concentration. Matrix effects, that originate from the interaction of alkaline earth metals with the charged surface of the AgNPs, are mitigated through a matrix-matched calibration. In this manner, spectral transitions can be selectively attributed to the concentration of cyanuric acid, which can be even visually quantified at low mg L?1 levels with minimum sample pre-treatment and without sophisticated instrumentation. Figure
Two colorimetric procedures for the determination of cyanuric acid, using silver nanoparticle-based (AgNPs) probes are presented. Matrix effects, which originate from the interaction of alkaline earth metals with the charged surface of the AgNPs, are mitigated through a matrix-matched calibration. In this manner, spectral transitions can be selectively attributed to the concentration of cyanuric acid, which can be visually quantified at low mg L?1 levels with minimum sample pre-treatment and no sophisticated instrumentation. 相似文献
27.
M. Soulis A.P. Mirgorodsky T. Merle-Méjean O. Masson P. Thomas M. Udovic 《Journal of Non》2008,354(2-9):143-149
The compositional invariance of the Raman spectra of (1 ? x)TeO2–xMnOm glasses (M = Ti, Nb) is analyzed and interpreted as evidence for the conservatism of a framework-type constitution inherent to such glasses. This is assigned to the chemical similarity of cations in the X–O–Y bridges (X, Y = Te4+, Ti4+, Nb5+) considered as the framework building blocks. It is concluded that the atoms of metals having valence IV and V can be placed into the category of such cations, to which certain of the atoms with valence III can be added. 相似文献
28.
Anatase-containing nanostructured TiO(2) particles with high surface area have been synthesized using a water immiscible room temperature ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate) as an effective additional solvent by the sol-gel method at low temperature. 相似文献
29.
To describe the two-dimensional flow of water in unsaturated soil, the governing equation is solved on a mesh constructed from small area elements. A transformation is introduced with which these possibly distorted rectangular elements of the physical plane are mapped into computational squares. Thus, irregularly shaped regions, which present difficulties when attempting to describe their geometry on an orthogonal computational mesh, can be more easily modelled. Using this methodology, here called the finite volume method, numerical results are obtained showing the ability of the method to describe transient unsaturated flow. 相似文献
30.
Maria Alexopoulou Emmanouela Mystiridou Dionysios Mouzakis Stefanos Zaoutsos Dimitrios G. Fatouros Nikolaos Bouropoulos 《Crystal Research and Technology》2016,51(1):41-48
In the present study, pure and mixed calcium phosphate/gypsum cements were prepared and characterized. Chara‐cterizations were performed using X‐ray diffraction FTIR spectroscopy, thermogravimetric analysis, and Scanning Electron Microscopy. Furthermore, the mechanical proper‐ties of the materials were studied and it was found that they depend with the gypsum content. Bioactivity tests after incubation in 2xSBF solution revealed dense apatite structure on the samples containing α‐tricalcium phosphate while the pure gypsum specimens showed sparse distributed tiny apatite crystals. Finally, 1% and 2% wt of the anti‐inflammatory drug ibuprofen incorporated into the cement paste and the release behaviour of the drug was stu‐died for 18 days in PBS solution. The results showed marked differences in the release profiles of ibuprofen for the different formulations. Complete release of the drug was noticed in the case of pure calcium phosphate cements within 18 days whereas ca. 35–40% of the drug was released from its congeners containing gypsum at the same timescale. 相似文献