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51.
两级载荷下复合材料层板疲劳与寿命预测 总被引:4,自引:0,他引:4
研究了复合材料层板疲劳过程中的累积应变演化规律,建立了以累积应变为基础的非线性积累损伤法则,实验结果表明:文中提出的累积应变方法能够较好地反映加载次序效应,准确地预测了复合材料层板在两级载荷下的疲劳寿命。 相似文献
52.
The paper addresses the stability of the sliding mode in nonstationary automatic-control systems of variable structure. The parameters of dynamic states are assumed to vary arbitrarily and continuously within a given bounded domain. The existence and stability conditions for the sliding mode on the switching hyperplane are established. They define nonstationary sets that contain phase velocity vectors directed away from the sliding hyperplane. The sets do not have common points with the switching hyperplane, except for the origin, for the known extreme values of the discontinuous coefficients of logical controls. This is the essence of the necessary and sufficient conditions for the stable sliding mode of the automatic-control system. The general results are used to analyze the stability conditions for the sliding mode in a nonstationary automatic-control system with a variable structure of the third order 相似文献
53.
铁电材料在力、电载荷作用尤其是循环载荷作用下有明显的热效应.热效应会在铁电材料中引起应力场和电场.另外,在外载作用下铁电材料发生约束畴变时也会产生附加的应力场,这些附加的应力场和电场都会对铁电材料的畴变产生影响.而且在循环载荷作用的情况下,这种影响会逐渐累积.但在以往的研究中,很少涉及这种影响.该文就循环电载下热效应引起的力、电场和约束畴变时产生的附加应力场对铁电材料畴变的影响进行了初步研究. 相似文献
54.
A new technique is described, which allows the assessment of elastic and inelastic regions around a macroscopic defect in
ferroelectric-ferroelastic ceramics. The accuracy and robustness of the method are demonstrated on a PZT plate with a centered
hole subjected to uni-axial compressive stresses. From the electrical potential distribution on the sample surface, the mechanical
response of the material is obtained at different load levels. 相似文献
55.
Wei Sun Yuanyuan Zhang Anhui Hu Yongxi Lu Fan Shi Bingxin Lei Zhenfan Sun 《Electroanalysis》2013,25(6):1417-1424
In this work a partially reduced graphene oxide (p‐RGO) modified carbon ionic liquid electrode (CILE) was prepared as the platform to fabricate an electrochemical DNA sensor, which was used for the sensitive detection of target ssDNA sequence related to transgenic soybean A2704‐12 sequence. The CILE was fabricated by using 1‐butylpyridinium hexafluorophosphate as the binder and then p‐RGO was deposited on the surface of CILE by controlling the electroreduction conditions. NH2 modified ssDNA probe sequences were immobilized on the electrode surface via covalent bonds between the unreduced oxygen groups on the p‐RGO surface and the amine group at the 5′‐end of ssDNA, which was denoted as ssDNA/p‐RGO/CILE and further used to hybridize with the target ssDNA sequence. Methylene blue (MB) was used as electrochemical indicator to monitor the DNA hybridization. The reduction peak current of MB after hybridization was proportional to the concentration of target A2704‐12 ssDNA sequences in the range from 1.0×10?12 to 1.0×10?6 mol/L with a detection limit of 2.9×10?13 mol/L (3σ). The electrochemical DNA biosensor was further used for the detection of PCR products of transgenic soybean with satisfactory results. 相似文献
56.
In order to compensate for light leakage in the oblique viewing directions of the dark state of the horizontal-switching mode such as the in-plane switching and fringe field switching modes. The viewing angle performance of the horizontal-switching mode with an compensation film has been evaluated on a case by case basis according to the retardation values of the films. Consequently, we found that a much better dark state can be achieved by using an optimised compensation film. 相似文献
57.
The flexible Ag/TiO2/ITO/PET resistive switching memory is prepared by low-temperature sol-gel method with UV irradiation, and the simple method that combined the advantages of sol-gel method and low temperature can be applied to fabricate high-quality film. The flexible Ag/TiO2/ITO/PET memory device displays good resistive behavior, for instance, the narrow distributions of switching voltages, good cycle endurance, and long retention time. Meanwhile, the multilevel resistance states of the device can be realized by controlling the compliance current or reset voltages, showing the potential of applications in neural networks and high-density storge. In addition, flexibility of the Ag/TiO2/ITO/PET is studied, which exhibit good endurance and retention properties under bending condition. The I–V curves are replotted and fitted for analyzing the conductive mechanism of the device. The fitting results show that SCLC and Ohmic mechanism are main mechanisms of high resistance state and low resistance state respectively. The electrochemical and thermochemical modes are adopted to explain resistive switching behavior. Our results indicate the Ag/TiO2/ITO/PET memory has potential application in wearable and foldable electronics. 相似文献
58.
Yan Zhang 《Numerical Functional Analysis & Optimization》2019,40(11):1268-1290
G-frames generalize frames in Hilbert spaces. The literatures show that g-frames and frames share many similar properties, while they behave differently in redundancy and perturbation properties. Interestingly, g-frames have been extensively studied, but g-frame sequences have not. This problem is nontrivial since a g-frame and a frame both involve all vectors in the same Hilbert space, while a g-frame sequence and a frame sequence do not. They involve different linear spans. Using the synthesis and Gram matrix methods, we in this paper characterize g-frame sequences and g-Riesz sequences; obtain the Pythagorean theorem for g-orthonormal systems. These results recover several known results and lead to some new results on g-frames. 相似文献
59.
60.
ABSTRACTQM(UB3LYP)/MM(AMBER) calculations were performed for the locations of the transition structure (TS) of the oxygen–oxygen (O–O) bond formation in the S4 state of the oxygen-evolving complex (OEC) of photosystem II (PSII). The natural orbital (NO) analysis of the broken-symmetry (BS) solutions was also performed to elucidate the nature of the chemical bonds at TS on the basis of several chemical indices defined by the occupation numbers of NO. The computational results revealed a concerted bond switching (CBS) mechanism for the oxygen–oxygen bond formation coupled with the one-electron transfer (OET) for water oxidation in OEC of PSII. The orbital interaction between the σ-HOMO of the Mn(IV)4–O(5) bond and the π*-LUMO of the Mn(V)1=O(6) bond plays an important role for the concerted O–O bond formation for water oxidation in the CaMn4O6 cluster of OEC of PSII. One electron transfer (OET) from the π-HOMO of the Mn(V)1=O(6) bond to the σ*-LUMO of the Mn(IV)4–O(5) bond occurs for the formation of electron transfer diradical, where the generated anion radical [Mn(IV)4–O(5)]-? part is relaxed to the ?Mn(III)4?…?O(5)- structure and the cation radical [O(6)=Mn(V)1]+ ? part is relaxed to the +O(6)–Mn(IV)1? structure because of the charge-spin separation for the electron-and hole-doped Mn–oxo bonds. Therefore, the local spins are responsible for the one-electron reductions of Mn(IV)4->Mn(III)4 and Mn(V)1->Mn(IV)1. On the other hand, the O(5)- and O(6)+ sites generated undergo the O–O bond formation in the CaMn4O6 cluster. The Ca(II) ion in the cubane- skeleton of the CaMn4O6 cluster assists the above orbital interactions by the lowering of the orbital energy levels of π*-LUMO of Mn(V)1=O(6) and σ*-LUMO of Mn(IV)4–O(5), indicating an important role of its Lewis acidity. Present CBS mechanism for the O–O bond formation coupled with one electron reductions of the high-valent Mn ions is different from the conventional radical coupling (RC) and acid-base (AB) mechanisms for water oxidation in artificial and native photosynthesis systems. The proton-coupled electron transfer (PC-OET) mechanism for the O–O bond formation is also touched in relation to the CBS-OET mechanism. 相似文献