排序方式: 共有16条查询结果,搜索用时 15 毫秒
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Prell JS Correra TC Chang TM Biles JA Williams ER 《Journal of the American Chemical Society》2010,132(42):14733-14735
Results from infrared photodissociation (IRPD) spectroscopy and kinetics of singly hydrated, protonated proline indicate that the water molecule hydrogen bonds preferentially to the formally neutral carboxylic acid at low temperatures and at higher temperatures to the protonated N-terminus, which bears the formal charge. Hydration isomer populations obtained from IRPD kinetic data as a function of temperature are used to generate a van't Hoff plot that reveals that C-terminal binding is enthalpically favored by 4.2-6.4 kJ/mol, whereas N-terminal binding is entropically favored by 31-43 J/(mol K), consistent with a higher calculated barrier for water molecule rotation at the C-terminus. 相似文献
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Francisco W. M. Ribeiro Isaac Omari Gilian T. Thomas Mathias Paul Peter J. H. Williams J. Scott McIndoe Thiago C. Correra 《Macromolecular rapid communications》2024,45(2):2300470
Herein, an evaluation of the initial step of benzoxazine polymerization is presented by mass spectrometry, with a focus on differentiating the phenoxy and phenolic products formed by distinct pathways of the cationic ring opening polymerization (ROP) mechanism of polybenzoxazine formation. The use of infrared multiple photon dissociation (IRMPD) and ion mobility spectrometry (IMS) techniques allows for differentiation of the two pathways and provides valuable insights into the ROP mechanism. The results suggest that type I pathway is favored in the initial stages of the reaction yielding the phenoxy product, while type II product should be observed at later stages when the phenoxy product would interconvert to the most stable type II phenolic product. Overall, the findings presented here provide important information on the initial step of the benzoxazine polymerization, allowing the development of optimal polymerization conditions and represents a way to evaluate other multifunctional polymerization processes. 相似文献
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Wax deposition from a waxy crude oil is modelled in turbulent flow in a pipeline. Molecular diffusion in a thin boundary layer
near the pipe wall is taken as the only mechanism responsible for deposition. The model takes into account the ablation, which
is a flow-related phenomenon that limits the growth of the deposit. The effect of desaturation of the oil is analyzed as well.
Two field cases are presented in which the numerical implementation of the model is in agreement with the experimental data.
Work performed in the framework of the cooperation between EniTecnologie (Milan) and I2T3 (Florence). 相似文献
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Summary The energy conservation equations are solved to determine the transient behaviour of a solar power plant, made of linear concentrators.
The equations are solved by the finite-difference method, assuming typical project parameters and the available experimental
data. Different physical and geometrical configurations are considered; the results are shown and discussed in order to supply
useful indications for the design of a solar power plant.
相似文献
Riassunto Si risolvono le equazioni di conservazione dell'energia per determinare il comportamento in regime transitorio di una centrale solare, costituita da concentratori parabolici lineari. Le equazioni sono risolte con il metodo delle differenze finite assumendo tipici parametri di progetto e i dati sperimentali disponibili. Si considerano differenti situazioni fisiche e geometriche; si analizzano e discutono i risultati, al, fine di fornire indicazioni sul progetto di una centrale solare.
Резюме Решаются стационарные уравнения переноса тепла для определения профилей темиературы в диатермическом масле, протекающем через линейный бойлер, расположенный в фокальной линии цилиндрических параболических солнечных концентраторов. Для решения уравнения используется метод конечных разностей, предполагая профили скоростей Никурадзе и используя имеющиеся экспериментальные данные для определения граничных условий и оценки параметров уравнения. Рассматривается система решений для некоторых физических и геометрических ситуаций. Проводится обсуждение пректа солнечной силовой установки.
相似文献
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Mathematical Models for Waxy Crude Oils 总被引:2,自引:1,他引:2
In this paper we review a series of mathematical models formulated for the flow of waxy crude oils, that is, of mineral oils with a high content of paraffinic hydrocarbons (with the generic name of waxes) which may be dissolved or segregated as solid crystals at sufficiently low temperatures. The flow takes place in a laboratory test loop. The crystals have a tendency to form aggregates, producing a gel-like structure. The resulting product can be modeled as a Bingham fluid, but its rheological parameters (yield stress and viscosity) depend on the amount and state of the segregated phase, whose evolution is in turn influenced by the flow. Of course temperature plays a key role. Wax can form a solid deposit at the pipe wall, reducing the pipe radius and this phenomenon is also taken into account. The models presented have a different degree of complexity, depending on which phenomena they include. In presenting each of them we discuss their expected range of validity. 相似文献
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Summary In this paper we report the in-plane fabrication and the characterization of artificially engineered biepitaxial grain boundaries
(GB) obtained by partly interposing a MgO seed layer between a bare or even-buffered substrate and a CeO2 thin layer. The main peculiarity of this technique can be summarized by the capability to locate and engineer a single 45°-tilted
GB at any stage of the device preparation. The junctions, realized by patterning the grain boundary occurring in the overhanging
YBCO film, show Josephson current modulation in a large temperature range with anI
c
R
n value of about 200 μV at 4.2K, theR
n value being constant over the whole superconducting region. Under microwave irradiation, theI–V characteristics display several Shapiro steps while, according to the Resistively Shunted Junction (RSJ) behaviour, the step
heights have the typical current biased junction dependence.
Paper presented at the ?VII Congresso SATT?, Torino, 4–7 October 1994. 相似文献