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排序方式: 共有487条查询结果,搜索用时 31 毫秒
31.
The effect of mean stress, or the stress ratio (R), on the fatigue-crack growth (FCG) behavior of α-aged and ω-aged microstructures of the beta titanium alloy Ti-10V-2Fe-3Al was investigated. While the mean stress had a negligible effect
on the FCG behavior of the α-aged microstructure, a strong effect was observed in the ω-aged microstructure. In particular, the values of the threshold stress-intensity range (ΔK
th
) exhibited a strong dependence on R in the ω-aged microstructure, while this dependence was weak in the α-aged microstructure. These effects seem to arise primarily from fracture-surface roughness-induced crack closure. The crack
closure levels for the α-aged microstructure were found to be very low compared to those for the ω-aged microstructure. Transmission electron microscopy and scanning electron microscopy studies of microstructures and fracture
surfaces were performed to gain insight into the deformation characteristics and crack propagation mechanisms, respectively,
in these microstructures. The microstructure-induced differences in FCG behavior are rationalized in terms of the effect of
aging on slip and crack closure. 相似文献
32.
Jit Biswas Andrei Tolstikov Maniyeri Jayachandran Victor Foo Aung Aung Phyo Wai Clifton Phua Weimin Huang Louis Shue Kavitha Gopalakrishnan Jer-En Lee Philip Yap 《电信纪事》2010,65(9-10):505-521
Monitoring and timely intervention are extremely important in the continuous management of health and wellness among all segments of the population, but particularly among those with mild dementia. In relation to this, we prescribe three design principles for the construction of services and applications. These are ambient intelligence, service continuity, and micro-context. In this paper, we provide three exemplars from our research and development activities that illustrate the use of these design principles in the construction of services and applications. All the applications are drawn from the field of care for mild dementia patients in their living quarters. 相似文献
33.
HBPE of different generations were synthesized using 4-hydroxybenzoic acid and 2,2′,2″-nitrilotriethanol via the A2 + B3 method. The reaction was carried out in a dry nitrogen atmosphere using p-toluene sulfonic acid (p-TSA) as an acid catalyst. The chosen molar ratios of 2,2′,2″-nitrilotriethanol to 4-hydroxybenzoic acid were 1:3, 1:6, and 1:21 for the G1, G2, and G5 generations, respectively. The G5 stage of HBPE was further coupled with acrylic acid to modify the terminal hydroxyl groups. The resulting products were analyzed using 1H NMR, 13C NMR, FTIR spectroscopy, and GPC. Silver nanoparticles were prepared by a reductive technique using HBPEs of the G5 generation as the matrix. XRD and TEM analysis indicated the formation of highly spherical and stable nanosilver in the HBPE. The antibacterial activity of the nanosilver/HBPE was evaluated against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) bacteria. 相似文献
34.
Arpita Basu Marci Wilkinson Kavitha Penugonda Brandi Simmons Nancy M Betts Timothy J Lyons 《Nutrition journal》2009,8(1):43
Background
Strawberry flavonoids are potent antioxidants and anti-inflammatory agents that have been shown to reduce cardiovascular disease risk factors in prospective cohort studies. Effects of strawberry supplementation on metabolic risk factors have not been studied in obese populations. We tested the hypothesis that freeze-dried strawberry powder (FSP) will lower fasting lipids and biomarkers of oxidative stress and inflammation at four weeks compared to baseline. We also tested the tolerability and safety of FSP in subjects with metabolic syndrome. FSP is a concentrated source of polyphenolic flavonoids, fiber and phytosterols. 相似文献35.
M. J. N. Chandrasekar M. Ravichandran M. J. Nanjan B. Suresh 《Drug development and industrial pharmacy》2001,27(9):959-964
A new polymerizable drug derivative of diclofenac sodium was synthesized and characterized in terms of melting point, elemental analysis, and infrared spectroscopy. It was then polymerized to obtain a new polymeric prodrug. The prodrug was evaluated for its viscosity, drug content, and in vitro drug release behavior at pH 1.2 and 7.2. The in vitro studies showed that the drug release takes place predominantly at the higher pH and in a sustained manner, as hypothesized. Stability at room temperature, bioavailability, and ulcer-inducing effect of the polymeric prodrug were also studied. The investigations showed complete drug absorption from the polymeric prodrug with a statistically significant decrease in ulcer scoring effect, thus showing its potential for site-specific and sustained drug delivery. 相似文献
36.
An experimental technique based on the Kolsky pressure bar has been developed to investigate the behavior of ceramics under
dynamic multiaxial compression. Experimental results for aluminum nitride (AlN), together with data available in the literature,
indicate that a Mohr-Coulomb criterion and the Johnson–Holmquist model fit the experimental data for failure in a brittle
manner, whereas the ceramic material exhibited pressure insensitive plastic flow at high pressures. A failure surface is constructed
which represents the material failure behavior, including brittle failure, brittle/ductile transition and plastic flow, under
various pressures. The effect of various material properties on the failure behavior was investigated. The Poisson's ratio
is found to be a measure of brittleness for ceramic materials with low spall strength under shock wave loading conditions.
Lower value of Poisson's ratio indicates that the material will fail in a brittle manner through axial splitting even under
uniaxial strain loading; whereas materials with higher Poisson's ratio may be expected to deform plastically beyond the Hugoniot
Elastic Limit (HEL). The applicability of the proposed failure surface to a range of ceramics is explored and the limitations
of the model are outlined.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
37.
This study mainly deals with cenosphere‐filled phenolic resin‐based composite that is prepared using ceramic‐ceramic fiber as reinforcement by traditional hand layup technique. The effect of cenosphere at various percentage is investigated on the mechanical, ablative, and thermal properties of the filled composites. Mechanical investigation revealed that the addition of microsized cenosphere up to 10% concentration increased the tensile strength of the composite. It is also observed that the addition of cenosphere increased the compressive strength and impact resistance of the composites. Thermogravimetric analysis (TGA) and ablative test revealed that the addition of cenosphere not only decreased both linear and mass ablative rates but also increased the upper working temperature of the filled ceramic/phenolic composites. POLYM. COMPOS., 37:1906–1913, 2016. © 2015 Society of Plastics Engineers 相似文献
38.
Ranganathan Kavitha Vikram Jayaram 《International Journal of Applied Ceramic Technology》2010,7(4):482-492
The structural features, including preferred orientation and surface morphology of zinc oxide (ZnO) films deposited by combustion flame pyrolysis were investigated as a function of process parameters, which include precursor solution concentration, substrate–nozzle (S–N) distance, gas flow rate, and duration of deposition. In this technique, the precursor droplets react within the flame and form a coating on an amorphous silica substrate held in or near the flame. Depending on the process parameters, the state of decomposition at which the precursor arrives on the substrate varies substantially and this in turn dictates the orientation and microstructure of the films. 相似文献
39.
Arun Muthukkumaran Shrayas Raghunathan Arjun Ravichandran Raghunathan Rengaswamy 《American Institute of Chemical Engineers》2023,69(7):e18068
With the ever-increasing volume of scientific literature, there is a strong need to develop methods that allow rigorous information identification. In this contribution, a state-of-the-art natural language processing (NLP) model was used to select perovskite materials for electrocatalytic applications from literature. This was accomplished by obtaining word embeddings for perovskite materials from the NLP model and subsequently designing downstream tasks to discover perovskite-based electrocatalyst materials. However, embeddings could be obtained only for materials available in the literature. Consequently, a novel methodology was devised to generate embeddings for newly designed materials. Results from the analysis showed that the computed embeddings could be used to rank materials for their suitability for electrocatalytic applications. Further, the word embeddings were also employed as features in predicting the electrocatalytic activity of perovskite-based electrocatalysts. The analysis demonstrated that the fidelity of regression models increased when the embeddings were used as features. 相似文献
40.