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1.
Journal of Thermal Analysis and Calorimetry - Nanomaterials and nanocomposites have gained relevance in science and technology due to their excellent properties. Therefore, the characterization of...  相似文献   
2.
Noble metal alloy nanoclusters (NCs) are interesting systems as the properties of two or more elements can be combined in one particle, leading to interesting fluorescence phenomena. However, previous studies have been exclusively performed on ligand-capped NCs from wet chemical synthesis. This makes it difficult to differentiate to which extent the fluorescence is affected by ligand-induced effects or the elemental composition of the metal core. In this work, we used laser fragmentation in liquids (LFL) to fabricate colloidal gold-rich bi-metallic AuPt NCs in the absence of organic ligands and demonstrate the suitability of this technique to produce molar fraction series of 1nm alloy NC. We found that photoluminescence of ligand-free NCs is not a phenomenon limited to Au. However, even minute amounts of Pt atoms in the AuPt NCs lead to quenching and red-shift of the fluorescence, which may be attributed to the altered surface charge density.  相似文献   
3.
The detonation characteristics of methane–oxygen mixtures at pre-detonation pressures of 101–1,013 kPa were investigated in a detonation tube. Both pure methane–oxygen mixtures and mixtures with argon dilution were explored. Measurements made include cell sizes via soot foil, wave speed via high speed ion probes / pressure transducers, and temperature / H2O molar concentration profiles via 100 kHz absorption spectroscopy. Measured cell widths agreed with predicted cell widths based on a ZND length correlation. In addition, the power law fit of cell width with pre-detonation pressure agreed with previous data at less than 101 kPa. Measured detonation wave speeds agreed within 3% of Chapmen-Jouguet for all cases. H2O molar density and temperature were successfully captured up to 507 kPa. However, above 507 kPa pre-detonation pressure, low signal to noise ratio and poor spectral fits at the extreme conditions of the von Neumann spike resulted in unacceptable uncertainty. These results provide a unique dataset to validate kinetics models and high-fidelity computation fluid dynamics codes for methane-oxygen detonations at elevated pre-detonation pressures relevant to rotating detonation rocket engines.  相似文献   
4.
Publications mathématiques de l'IHÉS - We develop a theory of Bridgeland stability conditions and moduli spaces of semistable objects for a family of varieties. Our approach is based...  相似文献   
5.
This study investigates the effects of intermediate temperature heat release (ITHR) on autoignition reactivity of full boiling range gasolines with different octane sensitivity through intake temperature and simulated exhaust gas recirculation (EGR) sweeps in a homogenous charge compression ignition (HCCI) engine. To isolate the ITHR effects, low temperature reactivity was suppressed through the use of high intake temperature and low intake oxygen mole fraction. For quantification of ITHR, a new method was applied to the engine data by examining the maximum value of the second derivative of heat release rate. Combustion phasing comparisons of fuels with octane sensitivity showed that fuel with less octane sensitivity became more reactive as intake temperature and simulated EGR ratio decreased, while fuel with higher octane sensitivity had a reverse trend. For all of the fuels that were tested, the amount of ITHR increased as the intake temperature and oxygen mole fraction increased. These ITHR trends, depending on octane sensitivity, were almost identical with the trends of combustion phasing, showing that ITHR significantly affects fuel autoignition reactivity and determines octane sensitivity.  相似文献   
6.
Journal of Solid State Electrochemistry - Many elements in the periodic table form ionic compounds; the crystal lattices of such compounds contain cations and anions, which are arranged in the way...  相似文献   
7.
A nonlinear damage model based on the combination of deformation and hysteretic energy and its validation with experiments are presented. Also, a combination parameter is defined to consider the mutual effect of deformation and hysteretic energy for different types of components in different loading stages. Four reinforced concrete (RC) columns are simulated and analyzed using the nonlinear damage model. The results indicate that the damage evolution evaluated by the model agrees well with the experimental phenomenon. Furthermore, the seismic damage evolution of a six-story RC frame was analyzed, revealing four typical failure modes according to the interstory drift distribution of the structure; the damage values calculated using the nonlinear damage model agree well with the four typical failure modes.  相似文献   
8.
Measuring angles in the Euclidean plane is a well-known topic, but for general normed planes there exists a variety of different concepts. These can be of a special kind, e.g. also preserving special orthogonality types. But these concepts are no angle measures in the sense of measure theory since they are not additive. This motivates us to define a new angle measure for normed planes that is in fact a measure in the sense of measure theory. Furthermore, we look at related types of rotation and reflection.  相似文献   
9.
We analyze isolated resonance curves (IRCs) in single-degree-of-freedom systems possessing nonlinear damping. Through the combination of singularity theory and the averaging method, the onset and merging of IRCs, which coincide to isola and simple bifurcation singularities, respectively, can be analytically predicted. Numerical simulations confirm the accuracy of the analytical developments. Another important finding of this paper is that we unveil a geometrical connection between the topology of the damping force and IRCs. Specifically, we demonstrate that extremas and zeros of the damping force correspond to the appearance and merging of IRCs. Considering a damping force possessing several minima and maxima confirms the general validity of the analytical result. It also evidences a very complex scenario for which different IRCs are created, co-exist and then merge together to form a super IRC which eventually merges with the main resonance peak.  相似文献   
10.
The effect of surface tension on laminar natural convection in a vertical cylindrical cavity filled with a weak evaporating liquid has been analyzed numerically. The cylindrical enclosure is insulated at the bottom, heated by a constant heat flux from the side, and cooled by a non-uniform evaporative heat flux from the top free surface having temperature-dependent surface tension. Governing equations with corresponding boundary conditions formulated in dimensionless stream function, vorticity, and temperature have been solved by finite difference method of the second-order accuracy. The influence of Rayleigh number, Marangoni number, and aspect ratio on the liquid flow and heat transfer has been studied. Obtained results have revealed that the heat transfer rate at free surface decreases with Marangoni number and increases with Rayleigh number, while the average temperature inside the cavity has an opposite behavior; namely, it growths with Marangoni number and reduces with Rayleigh number.  相似文献   
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