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排序方式: 共有273条查询结果,搜索用时 15 毫秒
1.
Safa Meraghni Labib Sadek Terrissa Meiling Yue Jian Ma Samir Jemei Noureddine Zerhouni 《International Journal of Hydrogen Energy》2021,46(2):2555-2564
Prognostics and health management of proton exchange membrane fuel cell (PEMFC) systems have driven increasing research attention in recent years as the durability of PEMFC stack remains as a technical barrier for its large-scale commercialization. To monitor the health state during PEMFC operation, digital twin (DT), as a smart manufacturing technique, is applied in this paper to establish an ensemble remaining useful life prediction system. A data-driven DT is constructed to integrate the physical knowledge of the system and a deep transfer learning model based on stacked denoising autoencoder is used to update the DT with online measurement. A case study with experimental PEMFC degradation data is presented where the proposed data-driven DT prognostics method has applied and reached a high prediction accuracy. Furthermore, the predicted results are proved to be less affected even with limited measurement data. 相似文献
2.
AbstractGeneralized thermoelastic interactions due to three-phase-lag time-nonlocal heat transfer in a Kelvin-Voigt type infinitely extended visco-thermoelastic continuum with cylindrical cavity has been investigated. The two-temperature generalized thermoelasticity theory has also been taken into account. The problem has been solved in the domain of Laplace on the assumption that the surface of the cavity is free from traction and is subjected to a smooth and time-dependent-heating effect. Laplace inversion of the transformed solutions has been carried out numerically. The obtained numerical data for different considerations are plotted in graphs to study the effects of time-nonlocal parameter, two-temperature parameter and visco-thermoelastic relaxation parameter on different thermoelastic quantities of physical interest. 相似文献
3.
Conductance measurements are reported for s-alkylisothiouronium bromide, iodide and picrate salts in the dipolar aprotic solvent DMSO at 25°C. The data were analysed by Fuoss's equation (1975–1980) for 1:1 electrolytes, from which the values of Λ0, the Gurney's cosphere diameter R and KA are obtained. The results are discussed in the light of the recorded values of the constants KR and KS and the free energy term Gs. 相似文献
4.
5.
Chao AC Ziadeh BI Diau GY Wijendran V Sarkadi-Nagy E Hsieh AT Nathanielsz PW Brenna JT 《Lipids》2003,38(4):425-429
One of the major survival challenges of premature birth is production of lung surfactant. The lipid component of surfactant,
dipalmitoyl PC (DPPC), increases in concentration in the period before normal term birth via a net shift in FA composition away from unsaturates. We investigated the influence of dietary DHA and arachidonic acid (AA)
on lung FA composition and DPPC concentration in term and preterm baboons. Pregnant animals/neonates were randomized to one
of four groups: breast-fed (B), term formula-fed (T−), preterm formulafed (P−), and preterm fed formula supplemented with DHA-AA (P+). Breast milk contained 0.68%wt DHA and the P+ group formula contained 0.61%wt DHA. In the preterm groups (P− and P+), pregnant females received a course of antenatal corticosteroids. At the adjusted age of 4 wk, neonate lung tissue was harvested,
and FA composition and DPPC were analyzed. Palmitate was ∼28%wt of lung total FA and no significant differences were found
among the four treatment groups. In contrast, DPPC in the B group lung tissue was significantly greater than DPPC in the unsupplemented
groups, but not compared with the P+ group. The B and P+ groups were not significantly different in DHA and AA, but were different compared with the unsupplemented (T, P−) groups. These results indicate that LCP supplementation increases lung DHA and AA, without compromising overall lung 16∶0
or DPPC. The shift in FA composition toward greater unsaturation in the groups consuming LCP supported improved surfactant
lipid concentration in preterm neonate lungs. 相似文献
6.
O. Ali Sadek Ibrahim D. Landa-Silva 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2016,20(8):3045-3061
In the context of information retrieval (IR) from text documents, the term weighting scheme (TWS) is a key component of the matching mechanism when using the vector space model. In this paper, we propose a new TWS that is based on computing the average term occurrences of terms in documents and it also uses a discriminative approach based on the document centroid vector to remove less significant weights from the documents. We call our approach Term Frequency With Average Term Occurrence (TF-ATO). An analysis of commonly used document collections shows that test collections are not fully judged as achieving that is expensive and maybe infeasible for large collections. A document collection being fully judged means that every document in the collection acts as a relevant document to a specific query or a group of queries. The discriminative approach used in our proposed approach is a heuristic method for improving the IR effectiveness and performance and it has the advantage of not requiring previous knowledge about relevance judgements. We compare the performance of the proposed TF-ATO to the well-known TF-IDF approach and show that using TF-ATO results in better effectiveness in both static and dynamic document collections. In addition, this paper investigates the impact that stop-words removal and our discriminative approach have on TF-IDF and TF-ATO. The results show that both, stop-words removal and the discriminative approach, have a positive effect on both term-weighting schemes. More importantly, it is shown that using the proposed discriminative approach is beneficial for improving IR effectiveness and performance with no information on the relevance judgement for the collection. 相似文献
7.
In this paper, we present a new sufficient condition for absolute stability of Lure system with two additive time-varying delay components. This criterion is expressed as a set of linear matrix inequalities (LMIs), which can be readily tested by using standard numerical software. We use this new criterion to stabilize a class of nonlinear time-delay systems. Some numerical examples are given to illustrate the applicability of the results using standard numerical software. 相似文献
8.
In this paper, we present a new sufficient condition for absolute stability of Lure system with two additive time-varying
delay components. This criterion is expressed as a set of linear matrix inequalities (LMIs), which can be readily tested by
using standard numerical software. We use this new criterion to stabilize a class of nonlinear time-delay systems. Some numerical
examples are given to illustrate the applicability of the results using standard numerical software. 相似文献
9.
Optimization of composite plates with piezoelectric stiffener-actuators under in-plane compressive loads 总被引:1,自引:0,他引:1
Sarp Adali Ibrahim S. Sadek John C. Bruch Jr. James M. Sloss 《Composite Structures》2005,71(3-4):293-301
Stiffeners which are used to strengthen a plate can be constructed of piezoceramic materials and subsequently used as piezo actuators to improve the load carrying capacity of the plate. In the present study, a fibre composite plate with initial imperfections and under in-plane compressive loads is studied with a view towards minimizing its deflection using the piezo actuators and the fibre orientations. Piezoceramic stiffeners are bonded symmetrically on the top and bottom of the plate and deployed as actuators. Two cases of electric fields, namely, the in-phase and out-of-phase voltages are applied to the actuators. The presence of initial deflections leads to deformation under the in-plane compressive loads which should be less than the critical buckling load. Two cases of initial imperfections are considered, and the first one is the deterministic initial deflections which are known a priori and as such they are given as input parameters for the problem. In the second case the initial deflections are uncertain and they have to be obtained according to a given criterion. In the present study they are determined to produce the least favourable initial deflection (largest deflection) at a given point and the solution is obtained by convex modelling. The effect of the actuators, the ply angles and the voltage are studied and their effects on the transverse deflection are investigated. A performance index involving the L2 norm of the deflections is minimized using the piezo effect and as well as the ply angles the optimal values of which are determined for various problem parameters. 相似文献
10.
Saylor David M. Fridy Joseph El-Dasher Bassem S. Jung Kee-Young Rollett Anthony D. 《Metallurgical and Materials Transactions A》2004,35(7):1969-1979
Techniques are described that have been used to create a statistically representative three-dimensional model microstructure
for input into computer simulations using the geometric and crystallographic observations from two orthogonal sections through
an aluminum polycrystal. Orientation maps collected on the observation planes are used to characterize the sizes, shapes,
and orientations of grains. Using a voxel-based tessellation technique, a microstructure is generated with grains whose size
and shape are constructed to conform to those measured experimentally. Orientations are then overlaid on the grain structure
such that distribution of grain orientations and the nearest-neighbor relationships, specified by the distribution of relative
misorientations across grain boundaries, match the experimentally measured distributions. The techniques are applicable to
polycrystalline materials with sufficiently compact grain shapes and can also be used to controllably generate a wide variety
of hypothetical microstructures for initial states in computer simulations.
This article is based on a presentation made at the symposium “Characterization and Representation of Material Microstructures
in 3-D” held October 8–10, 2002, in Columbus, OH, under the auspices of ASM International’s Phase Transformations committee. 相似文献