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排序方式: 共有1513条查询结果,搜索用时 31 毫秒
71.
Mohammed Sid Ahmed Houari Samir Benyoucef Ismail Mechab El Abbas Adda Bedia 《热应力杂志》2013,36(4):315-334
The thermoelastic bending analysis of functionally graded sandwich plates using the two-variable refined plate theory is presented in this paper. Unlike any other theory, the number of unknown functions involved is only four, as against five in case of other shear deformation theories. The theory presented is variationally consistent, has strong similarity with classical plate theory in many aspects, does not require shear correction factor, and gives rise to transverse shear stress variation such that the transverse shear stresses vary parabolically across the thickness satisfying shear stress free surface conditions. The sandwich plate faces are assumed to have isotropic, two-constituent material distribution through the thickness, and the modulus of elasticity, Poisson's ratio of the faces, and thermal expansion coefficients are assumed to vary according to a power law distribution in terms of the volume fractions of the constituents. The core layer is still homogeneous and made of an isotropic ceramic material. Several kinds of sandwich plates are used taking into account the symmetry of the plate and the thickness of each layer. The influences played by the transverse shear deformation, thermal load, plate aspect ratio, and volume fraction distribution are studied. Numerical results for deflections and stresses of functionally graded metal–ceramic plates are investigated. It can be concluded that the proposed theory is accurate and simple in solving the thermoelastic bending behavior of functionally graded plates. 相似文献
72.
Hasanin Mohamed Sharmoukh Walid Hassan Youssef R. El Saied Houssni 《Journal of Inorganic and Organometallic Polymers and Materials》2022,32(2):667-677
Journal of Inorganic and Organometallic Polymers and Materials - Historically, the recording of information over paper has always been regarded as the most important factor for maintaining records... 相似文献
73.
Samir Abu-Rumeileh Peggy Barschke Patrick Oeckl Simone Baiardi Angela Mammana Andrea Mastrangelo Mhd Rami Al Shweiki Petra Steinacker Anna Ladogana Sabina Capellari Markus Otto Piero Parchi 《International journal of molecular sciences》2022,23(4)
Proenkephalin (PENK) and prodynorphin (PDYN) are endogenous opioid peptides mainly produced in the striatum and, to a lesser extent, in the cerebral cortex. Dysregulated metabolism and altered cerebrospinal fluid (CSF) levels of PENK and PDYN have been described in several neurodegenerative diseases. However, no study to date investigated these peptides in the CSF of sporadic Creutzfeldt–Jakob disease (sCJD). Using liquid chromatography-multiple reaction monitoring mass spectrometry, we evaluated the CSF PDYN- and PENK-derived peptide levels in 25 controls and 63 patients with sCJD belonging to the most prevalent molecular subtypes (MM(V)1, VV2 and MV2K). One of the PENK-derived peptides was significantly decreased in each sCJD subtype compared to the controls without a difference among subtypes. Conversely, PDYN-derived peptides were selectively decreased in the CSF of sCJD MV2K, a subtype with a more widespread overall pathology compared to the sCJD MM(V)1 and the VV2 subtypes, which we confirmed by semiquantitative analysis of cortical and striatal neuronal loss and astrocytosis. In sCJD CSF PENK and PDYN were associated with CSF biomarkers of neurodegeneration but not with clinical variables and showed a poor diagnostic performance. CSF PDYN and PENK-derived peptides had no significant diagnostic and prognostic values in sCJD; however, the distinct marker levels between molecular subtypes might help to better understand the basis of phenotypic heterogeneity determined by divergent neuronal targeting. 相似文献
74.
Youssef El Khoury Marie Gebelin Jrme de Sze Christine Patte-Mensah Gilles Marcou Alexandre Varnek Ayiko-Guy Mensah-Nyagan Petra Hellwig Nicolas Collongues 《International journal of molecular sciences》2022,23(5)
Neuromyelitis optica spectrum disorder (NMOSD) and multiple sclerosis (MS) are both autoimmune inflammatory and demyelinating diseases of the central nervous system. NMOSD is a highly disabling disease and rapid introduction of the appropriate treatment at the acute phase is crucial to prevent sequelae. Specific criteria were established in 2015 and provide keys to distinguish NMOSD and MS. One of the most reliable criteria for NMOSD diagnosis is detection in patient’s serum of an antibody that attacks the water channel aquaporin-4 (AQP-4). Another target in NMOSD is myelin oligodendrocyte glycoprotein (MOG), delineating a new spectrum of diseases called MOG-associated diseases. Lastly, patients with NMOSD can be negative for both AQP-4 and MOG antibodies. At disease onset, NMOSD symptoms are very similar to MS symptoms from a clinical and radiological perspective. Thus, at first episode, given the urgency of starting the anti-inflammatory treatment, there is an unmet need to differentiate NMOSD subtypes from MS. Here, we used Fourier transform infrared spectroscopy in combination with a machine learning algorithm with the aim of distinguishing the infrared signatures of sera of a first episode of NMOSD from those of a first episode of relapsing-remitting MS, as well as from those of healthy subjects and patients with chronic inflammatory demyelinating polyneuropathy. Our results showed that NMOSD patients were distinguished from MS patients and healthy subjects with a sensitivity of 100% and a specificity of 100%. We also discuss the distinction between the different NMOSD serostatuses. The coupling of infrared spectroscopy of sera to machine learning is a promising cost-effective, rapid and reliable differential diagnosis tool capable of helping to gain valuable time in patients’ treatment. 相似文献
75.
76.
Astrid Heckl Samir Cenanovic Mathias G?ken Robert F. Singer 《Metallurgical and Materials Transactions A》2012,43(1):10-19
The phase stability of nickel-base superalloys has been investigated using a new in-house-designed alloy series with stepwise
increased additions of Re and Ru at otherwise fixed atomic fractions of alloying elements. Results presented in this study
are focused on the lesser-known topologically closed packed (TCP) formation of columnar colonies or so-called discontinuous
precipitation. A detailed investigation of these colonies allowed for identifying compositional changes during the growth
process and for providing a three-dimensional (3-D) illustration of the TCP phases within these colonies. The results were
used to compare the colony growth process with existing growth models. Furthermore, the influence of Re and Ru on the appearance
of discontinuous precipitation has been investigated by means of colony width and the effect on creep properties. Larson-Miller
plots are given to illustrate the creep strength of directionally solidified samples with and without TCP colonies compared
with single crystalline samples free from TCP colonies. 相似文献
77.
The present brief account relates synthetic endeavours revolving around a novel chemistry of xanthates (dithiocarbonates) being developed in our group. The degenerative reversible transfer of xanthates has a unique ability to store reactive radicals in a dormant form, and thereby to enhance their lifetime in a concentrated medium, while at the same time, regulating their absolute and relative concentrations. It allows intermolecular radical additions even to unactivated alkenes, and can promote otherwise sluggish radical processes, such as 5-endo, 6-exo, 6-endo, 7-endo, and 8-endo cyclisations, as well as ring closures on (hetero)aromatic structures. This chemistry has proved remarkably versatile and powerful, both for solving synthetic problems and for the industrial production of block copolymers through the RAFT/MADIX technology. 相似文献
78.
Abdelkader Nour Samir Lecheb Nouredine Chikh M. Ouali Si-Chaïb 《Journal of Mechanical Science and Technology》2011,25(7):1629-1636
This work concerns the characterization of the thermodynamic behavior of the superalloy Airsist 215 (PN 3601669-7) containing
cobalt. Such superalloys are used in aeronautical construction, in the hot parts of the turbine. They are frequently used
for the production of the paddles. The parts in service are subjected to dynamic solicitations and thermal fluctuations over
the course of time. They are responsible for modification and degradation of material properties. This can lead to the appearance
of cracks and, in the long term, to the rupture of these parts. In this paper, a preliminary physical study is made on the
appearance of the cracks, followed by experiments using shocks at ambient temperature and under a heating situation which
simulates combustion. It is found that these dynamic loads have a significant impact on the development of the cracks that
appear on the segments of the turbine nozzle. The study is devoted to the elastic shock of Hertz-Boussinesq extended to viscoelastic
bodies by direct convolution of Riemann-Stielges. The interest resides in the local convolution and the distribution of stresses
in the contact zone. The shock excitation method includes a deduced force in the load and disload phases. This force is an
impulse which approaches a Dirac function. The sample can be modeled approximately by a system of one degree of freedom for
natural frequency, damping and transfer function. The spectral response of the specified shock allows calculation of the damping.
Every point of this spectrum gives the response for the linear system of the transfer function. Then, viscoelastic shock parameters
are deduced. 相似文献
79.
Emna Hmani Sourour Chaabane Elaoud Youssef Samet Ridha Abdelhdi 《Journal of hazardous materials》2009,170(2-3):928-933
Electrochemical oxidation of O-Toluidine (OT) was studied by galvanostatic electrolysis using lead dioxide (PbO2) and boron-doped diamond (BDD) as anodes. The influence of operating parameters, such as current density, initial concentration of OT and temperature was investigated. Measurements of chemical oxygen demand were used to follow the oxidation. The experimental data indicated that on PbO2 and BDD anodes, OT oxidation takes place by reaction with electrogenerated hydroxyl radicals and is favoured by low current density and high temperature. Furthermore, BDD anodes offer significant advantages over PbO2 in terms of current efficiency and oxidation rate. 相似文献
80.
Youssef Travaly Mikhail Baklanov 《集成电路应用》2009,(1):37-40
随着对新化学品和集成方案了解的加深,我们不但可以减轻介电层孔隙率增加引起的负担还可以降低工艺对超低k薄膜的损伤。 相似文献