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排序方式: 共有163条查询结果,搜索用时 15 毫秒
31.
In this paper, a general approach to address modeling of aeroelastic systems, with the final goal to apply μ analysis, is discussed. The chosen test bed is the typical section with unsteady aerodynamic loads, which enables basic modeling features to be captured and so extend the gained knowledge to practical problems treated with modern techniques. The aerodynamic operator has a nonrational dependence on the Laplace variable s, and hence, 2 formulations for the problem are available: frequency domain or state‐space (adopting rational approximations). The study attempts to draw a parallel between the 2 consequent linear fractional transformation modeling processes, emphasizing critical differences and their effect on the predictions obtained with μ analysis. A peculiarity of this twofold formulation is that aerodynamic uncertainties are inherently treated differently and therefore the families of plants originated by the possible linear fractional transformation definitions are investigated. One of the main results of the paper is to propose a unified framework to address the robust modeling task, which enables the advantages of both the approaches to be retained. On the analysis side, the application of μ analysis to the different models is shown, emphasizing its capability to gain insight into the problem. 相似文献
32.
Petr Kovaricek Peter Nadazdy Eva Pluharova Alica Brunova Riyas Subair Karol Vegso Valentino Libero Pio Guerra Oleksandr Volochanskyi Martin Kalbac Alexander Krasnansky Pallavi Pandit Stephan Volker Roth Alexander Hinderhofer Eva Majkova Matej Jergel Jianjun Tian Frank Schreiber Peter Siffalovic 《Advanced functional materials》2021,31(13):2009007
2D hybrid organic–inorganic perovskites are valued in optoelectronic applications for their tunable bandgap and excellent moisture and irradiation stability. These properties stem from both the chemical composition and crystallinity of the layer formed. Defects in the lattice, impurities, and crystal grain boundaries generally introduce trap states and surface energy pinning, limiting the ultimate performance of the perovskite; hence, an in-depth understanding of the crystallization process is indispensable. Here, a kinetic and thermodynamic study of 2D perovskite layer crystallization on transparent conductive substrates are provided—fluorine-doped tin oxide and graphene. Due to markedly different surface structure and chemistry, the two substrates interact differently with the perovskite layer. A time-resolved grazing-incidence wide-angle X-ray scattering (GIWAXS) is used to monitor the crystallization on the two substrates. Molecular dynamics simulations are employed to explain the experimental data and to rationalize the perovskite layer formation. The findings assist substrate selection based on the required film morphology, revealing the structural dynamics during the crystallization process, thus helping to tackle the technological challenges of structure formation of 2D perovskites for optoelectronic devices. 相似文献
33.
Alessandra Beretta Tiziana Bruno Gianpiero Groppi Ivan Tavazzi Pio Forzatti 《Applied catalysis. B, Environmental》2007,70(1-4):515
Experimental evidence and literature indications suggest that the process of methane partial oxidation over Rh catalysts is structure sensitive. Crystal phases and Rh cluster size are thus expected to affect the final catalytic performance. In this work, it is observed that outstanding performances are obtained when the as-prepared catalysts are conditioned through repeated runs at increasing temperature and O2/CH4 = 0.56. Catalysts slowly activate, that is CH4 conversion and synthesis gas selectivity progressively grow with time on stream. On the basis of TPO and CH4 decomposition measurements, this phenomenon is herein explained as the result of a surface reconstruction driven by the repeated exposition to the reaction at high temperature; it is thought that such reconstruction tends to eliminate defect sites and disfavors C-deposition reactions (extremely fast over steps and kinks). Conditioning with O2-enriched feed streams makes conditioning faster, since the accumulation of surface C-species is suppressed; however, the catalyst is eventually less active than a catalyst conditioned with standard feed mixtures. As an alternative, accumulation of carbon can be suppressed and surface reconstruction proceeds faster if the catalyst is directly exposed to the reaction at high temperature for several hours. 相似文献
34.
Nova Isabella Castoldi Lidia Lietti Luca Tronconi Enrico Forzatti Pio 《Topics in Catalysis》2007,42(1-4):21-25
The reduction process of NOx species stored over Pt-Ba/Al2O3 Lean NOx Trap systems is analysed in this paper when H2 is used as a reductant. The effect of different experimental conditions (temperature, reductant concentration, adsorption
lengths, etc.) is addressed and discussed in relation to the selectivity and the efficiency of the reduction process. 相似文献
35.
The unsteady-state kinetics of the selective catalytic reduction (SCR) of NO with NH3 is studied over V2O5–WO3/TiO2 model catalysts by means of the transient response method. NH3 strongly adsorbs onto the catalyst surface whereas NO does not adsorb appreciably. A dynamic mathematical model based on a Temkin-type desorption process for NH3 and a SCR reaction rate with a complex dependence on the ammonia surface coverage is well suited to represent the data. 相似文献
36.
Marzia Pucci Stefania Raimondo Ornella Urzì Marta Moschetti Maria Antonietta Di Bella Alice Conigliaro Nadia Caccamo Marco Pio La Manna Simona Fontana Riccardo Alessandro 《International journal of molecular sciences》2021,22(22)
Tumor-associated macrophages play a key role in promoting tumor progression by exerting an immunosuppressive phenotype associated with the expression of programmed cell death ligand 1 (PD-L1). It is well known that tumor-derived small extracellular vesicles (SEVs) affect the tumor microenvironment, influencing TAM behavior. The present study aimed to examine the effect of SEVs derived from colon cancer and multiple myeloma cells on macrophage functions. Non-polarized macrophages (M0) differentiated from THP-1 cells were co-cultured with SEVs derived from a colorectal cancer (CRC) cell line, SW480, and a multiple myeloma (MM) cell line, MM1.S. The expression of PD-L1, interleukin-6 (IL-6), and other inflammatory cytokines as well as of the underlying molecular mechanisms were evaluated. Our results indicate that SEVs can significantly upregulate the expressions of PD-L1 and IL-6 at both the mRNA and protein levels and can activate the STAT3 signaling pathway. Furthermore, we identified the TLR4/NF-kB pathway as a convergent mechanism for SEV-mediated PD-L1 expression. Overall, these preliminary data suggest that SEVs contribute to the formation of an immunosuppressive microenvironment. 相似文献
37.
38.
Maria Losurdo Pio Capezzuto Giovanni Bruno Francesco Babudri Antonio Cardone Gianluca M. Farinola Francesco Naso Michael Büchel 《Polymer》2008,49(19):4133-4140
This study is an investigation on the interplay between supramolecular organization and optical properties of thin films of conjugated polymers with fluorinated vinylene units such as poly[2-(2-ethylhexyloxy)-5-methoxy]-1,4-phenylenedifluorovinylene (MEH-PPDFV) and poly(2-methoxy-5-propyloxysulfonatephenylenedifluorovinylene) (MPS-PPDFV), which are both PPV polymers with fluorinated double bonds with alkoxy chains in the 2 and 5 positions. MEH-PPDFV is the fluorinated version of the widely investigated MEH-PPV, and MPS-PPDFV is characterized by the presence of ionic alkoxy side chains. This interplay is elucidated exploiting atomic force microscopy, spectroscopic ellipsometry and photoluminescence to obtain complementary information. It is demonstrated that the presence of F-atoms in the vinylene units of the MEH-PPDFV yields a blue optical band gap with the maximum of the fundamental HOMO-LUMO transition and of the room temperature photoluminescence at 3.74 eV (331 nm) and at 2.71 eV (458 nm), respectively. The blue-absorption and emission in the thin films are ascribed to the fact that fluorine atoms on the vinylene units prevent π-stacking of polymeric chains. Furthermore, the dependence of morphology, anisotropy in optical properties and photoluminescence properties of films on deposition methodology is also discussed. MEH-PPDFV also emits homogeneous blue-greenish electroluminescence at 2.46 eV (504 nm). 相似文献
39.
Ooi JongBoon Wang Xin Tan ChingSeong Ho Jee-Hou Lim Ying Pio 《Journal of Mechanical Science and Technology》2012,26(2):575-589
The portal axle is a gearbox that is specially designed for off-road driving conditions. It is installed between the wheel
and the axle shaft to give higher ground clearance to the vehicle. The modeling and simulation of spur gears in portal axle
is important to predict the actual motion behavior. However, gear train design in portal axle is difficult to study comprehensively
due to their relatively low cost and short product life cycle. In this study, modal analysis of portal axle is simulated using
finite element method (FEM). Modal analysis is simulated on three different combinations of gear train system commonly designed
for portal axle. The three gear trains being analyzed are gear train without idler gear, one idler gear and two idler gears.
FEM static stress analysis is also simulated on three different gear trains to study the gear teeth bending stress and contact
stress behavior of the gear trains in different angular positions from 0° to 18°. The single and double pair gear teeth contact
are also considered. This methodology serves as a novel approach for gear train design evaluation, and the study of gear stress
behavior in gear train which is needed in the small workshop scale industries. 相似文献
40.
Pio John S. Buenconsejo Kanau Ito Hee Young Kim Shuichi Miyazaki 《Acta Materialia》2008,56(9):2063-2072
Ti–Ni microtubes are attractive materials for biomedical devices, such as micro-catheters and micro-stents, but it is difficult to fabricate them with dimensions of less than 100 μm by conventional tube-drawing. In this study, Ti–Ni microtubes with 50 μm inner diameter and a tube wall thickness of 6 μm was successfully fabricated using a novel method in which Ti–Ni was sputter-deposited on a Cu wire with a diameter of 50 μm. All the microtubes exhibited shape memory behavior after crystallization at 873 K for 3.6 ks. Microtubes fabricated without rotating the Cu wire during deposition have low fracture strength due to the columnar grains and non-uniform tube wall thickness. Microtubes fabricated by depositing Ti–Ni on a rotating wire have a uniform wall thickness and the fracture strength increased with increasing rotation speed. Microtubes made by the rotating-wire method exhibited superelasticity of 3% strain at room temperature with high fracture stress of 950 MPa, suggesting that they are suitable for practical applications. 相似文献