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991.
Haotian Wang Jian Sun Hong Ding Ganlin Shan Zhuang Chang 《Journal of Failure Analysis and Prevention》2017,17(6):1182-1190
Performance degradation modeling plays an important role in prognostics and health management of mechanical system. Influenced by the complex structure of the hydraulic pump and the limited experiment standards, it is hard to establish an appropriate performance degradation model. To fulfill current requirements, a method for establishing the performance degradation model based on accelerated experiment is proposed. In order to describe the general trend of the degradation, the double-stress exponential model is firstly established as the theoretical degradation model. On this basement, combined with the characteristics of the experiment, the accelerating coefficient is settled; meanwhile, the procedures for assuring the model parameters are presented. Furthermore, based on the accelerated experiment of the hydraulic pump under various stresses, the performance degradation model is finally established. Result of the experimental analysis indicates that the proposed method is applicable and the presented model is effective to measure the performance degradation of pump. 相似文献
992.
Shuntao Xu Jinkun Liu Yuan Xue Tianya Wu 《Fullerenes, Nanotubes and Carbon Nanostructures》2017,25(1):40-46
Oxidation time and exfoliated conditions of graphite oxides (GOs) were investigated to prepare few–layer graphene oxide and reduced graphene oxide via a modified Hummers approach. Different oxidative degree of GOs was prepared by changing oxidation time, and the effects of oxidative degree of GOs in different oxidation time were studied by XRD, FT-IR. Afterwards, highly oxidized GOs were used as precursor to prepare graphene oxide and reduced graphene oxide by ultrasonic dispersion method and thermal expansion method. The exfoliated conditions (ultrasonic power and ultrasonic time, thermal exfoliated temperature) were investigated to prepare few-layered graphene oxide and reduced graphene oxide. 相似文献
993.
Changjiang Zhou Futian Huang Xu Han Yuantong Gu 《International Journal of Mechanics and Materials in Design》2017,13(3):335-345
This paper presents a continuous elastic–plastic asperity contact model with or without the consideration of friction to investigate the micro-contact properties of gear tooth profiles. The model for normal or side contact analysis is established according to Hertz contact theory and the asperity morphology feature, which yields to similar results as obtained from the model proposed by Chang W.R., Etsion I., and Bogy D.B. (CEB model) and the model proposed by Kogut L. and Etsion I. (KE model). More importantly, this model avoids the constant average contact stress as predicted by the CEB model, and the noncontinuous contact stress and deformation within the ultimate strength as given by the KE model. As a application of the present theoretical model in micro-contact analysis of rough tooth profiles, a finite element model (FE model) for elastic–plastic asperity in normal or side contact is established according to the measured surface parameters of a spur gear pair. It is shown that the extreme point of Von Mise stress of the asperities along the normal vector is ascertained by FE model, and that the extreme point is relative to the initial occurrence of the asperities plastic deformation. Compared with the present theoretical model, the similar normal contact stress along the contact radius is attained by FE model. Though the contact stress isogram in the specific plane in normal or side contact of the asperities is a circle or ellipse respectively when the plastic deformation is expanded from the inside of the asperities to their surfaces, it is in line with the distribution of elastic and plastic region of the theoretical model. Compared with CEB model, KE model, and FE model, the consistent results are attained by the present theoretical model in elastic–plastic asperity contact analysis. The results indicate that the theoretical model is applicable to the elastic–plastic asperity contact analysis on the rough surface of a spur gear drive. 相似文献
994.
Ren Zhang Yunhua Zhou Yiyi Zhu Yangyang Li Liang Chu Yonggang Min Jian Zhang Jianping Yang Xing’ao Li 《Journal of Superconductivity and Novel Magnetism》2017,30(9):2471-2479
Tetragonal BiFeO3 (BFO), which has a giant spontaneous polarization, has attracted a great deal of attention recently. In this paper, we systematically study the structural, magnetic, electronic and optic properties of BFO, BiFe0.75Mn0.25 O 3 (BFMM), and BiFe0.75Ti0.125Mn0.125 O 3 (BFMT). Results show that doping Ti and Mn into the Fe sites increases the c/a ratio and enhances the magnetization of BiFeO3 from 0 to 5 μB. The crystal symmetry changes from orthogonality to tetragonality with half of the Mn atoms being replaced by Ti in BiFe0.75Mn0.25 O 3, which suppresses the energy splitting of the Mn 3d orbitals and thus enlarge the band gap to 1.21 eV for BiFe0.75Ti0.125Mn0.125 O 3. Our calculated Bader charge and charge density difference show that the smallest volume of BiFe0.75Mn0.25 O 3 arises from the strong Mn–O bonds in BiFe0.75Mn0.25 O 3. Further investigations indicate similar optical behaviors for BiFeO3 and BiFe0.75Ti0.125Mn0.125 O 3. However, BiFe0.75Mn0.25 O 3 exhibits strong absorption in the infrared region for the transition from O 2p to Mn \({e_{g}^{2}}\) and \(t_{2g}^{3}\). 相似文献
995.
Chao‐Yu Li Zhen‐Wei Yang Jin‐Chao Dong Tapan Ganguly Jian‐Feng Li 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(8)
Shell‐isolated nanoparticle‐enhanced Raman spectroscopy (SHINERS), due to its versatility, has been able to break the long‐term limitations of the material‐ and substrate‐specific generalities in the traditional field of surface‐enhanced Raman spectroscopy. With a shell‐isolated work principle, this method provides an opportunity to investigate successfully in surface, biological systems, energetic materials, and environmental sciences. Both the shell material and core morphology are being improved continuously to meet the requirements in diverse systems, such as the electrochemical studies at single crystal electrode surfaces, in situ monitoring of photoinduced reaction processes, practical applications in energy conversion and storage, inspections in food safety, and the surface‐enhanced fluorescence. Predictably, the concept of shell‐isolated nanoparticle‐enhancement could be expanded to the wider range for the performance of plasmon‐enhanced spectral modifications. 相似文献
996.
Phase Separation Derived Core/Shell Structured Cu11V6O26/V2O5 Microspheres: First Synthesis and Excellent Lithium‐Ion Anode Performance with Outstanding Capacity Self‐Restoration 下载免费PDF全文
Jian Pei Gang Chen Qiang Zhang Changfeng Bie Jingxue Sun 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(17)
Novel amorphous vanadium oxide coated copper vanadium oxide (Cu11V6O26/V2O5) microspheres with 3D hierarchical architecture have been successfully prepared via a microwave‐assisted solution method and subsequent annealing induced phase separation process. Pure Cu11V6O26 microspheres without V2O5 coating are also obtained by an H2O2 solution dissolving treatment. When evaluated as an anode material for lithium‐ion batteries (LIBs), the as‐synthesized hybrid exhibits large reversible capacity, excellent rate capability, and outstanding capacity self‐recovery. Under the condition of high current density of 1 A g?1, the 3D hierarchical Cu11V6O26/V2O5 hybrid maintains a reversible capacity of ≈1110 mA h g?1. Combined electrochemical analysis and high‐resolution transmission electron microscopy observation during cycling reveals that the amorphous V2O5 coating plays an important role on enhancing the electrochemical performances and capacity self‐recovery, which provides an active amorphous protective layer and abundant grain interfaces for efficient inserting and extracting of Li‐ion. As a result, this new copper vanadium oxide hybrid is proposed as a promising anode material for LIBs. 相似文献
997.
Zhongxue Chen Fei Xu Shunan Cao Zhengfeng Li Hanxi Yang Xinping Ai Yuliang Cao 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(18)
LiV3O8 nanorods with controlled size are successfully synthesized using a nonionic triblock surfactant Pluronic‐F127 as the structure directing agent. X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy techniques are used to characterize the samples. It is observed that the nanorods with a length of 4–8 µm and diameter of 0.5–1.0 µm distribute uniformly. The resultant LiV3O8 nanorods show much better performance as cathode materials in lithium‐ion batteries than normal LiV3O8 nanoparticles, which is associated with the their unique micro–nano‐like structure that can not only facilitate fast lithium ion transport, but also withstand erosion from electrolytes. The high discharge capacity (292.0 mAh g?1 at 100 mA g?1), high rate capability (138.4 mAh g?1 at 6.4 A g?1), and long lifespan (capacity retention of 80.5% after 500 cycles) suggest the potential use of LiV3O8 nanorods as alternative cathode materials for high‐power and long‐life lithium ion batteries. In particular, the synthetic strategy may open new routes toward the facile fabrication of nanostructured vanadium‐based compounds for energy storage applications. 相似文献
998.
Sensitive Detection of Carcinoembryonic Antigen Using Stability‐Limited Few‐Layer Black Phosphorus as an Electron Donor and a Reservoir 下载免费PDF全文
Jian Peng Youqun Lai Yuanyuan Chen Jun Xu Liping Sun Jian Weng 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(15)
The instability of few‐layer black phosphorus (FL‐BP) hampers its further applications. Here, it can be demonstrated that the instability of FL‐BP can also be the advantage for application in biosensor. First, gold nanoparticle/FL‐BP (BP‐Au) hybrid is facilely synthesized by mixing Au precursor with FL‐BP. BP‐Au shows outstanding catalytic activity (K = 1120 s?1 g?1) and low activation energy (17.53 kJ mol?1) for reducing 4‐nitrophenol, which is attributed to the electron‐reservoir and electron‐donor properties of FL‐BP, and synergistic interaction of Au nanoparticles and FL‐BP. Oxidation of FL‐BP after catalytic reaction is further confirmed by transmission electron microscope, X‐ray photoelectron spectroscopy, and zeta potentials. Second, the catalytic activity of BP‐Au can be reversibly switched from “inactive” to “active” upon treatment with antibody and antigen in solution, thus providing a versatile platform for label‐free colorimetric detection of biomarkers. The sensor shows a wide detection range (1 pg mL?1 to –10 µg mL?1), high sensitivity (0.20 pg mL?1), and selectivity for detecting carcinoembryonic antigen (CEA). Finally, the biosensor has been used to detect CEA in colon and breast cancer clinical samples with satisfactory results. Therefore, the instability of BP can also be the advantage for application in detecting cancer biomarker in clinic. 相似文献
999.
Near‐Infrared Photodetectors Based on MoTe2/Graphene Heterostructure with High Responsivity and Flexibility 下载免费PDF全文
Wenzhi Yu Shaojuan Li Yupeng Zhang Weiliang Ma Tian Sun Jian Yuan Kai Fu Qiaoliang Bao 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(24)
2D transition metal dichalcogenides (TMDCs) have attracted considerable attention due to their impressively high performance in optoelectronic devices. However, efficient infrared (IR) photodetection has been significantly hampered because the absorption wavelength range of most TMDCs lies in the visible spectrum. In this regard, semiconducting 2D MoTe2 can be an alternative choice owing to its smaller band gap ≈1 eV from bulk to monolayer and high carrier mobility. Here, a MoTe2/graphene heterostructure photodetector is demonstrated for efficient near‐infrared (NIR) light detection. The devices achieve a high responsivity of ≈970.82 A W?1 (at 1064 nm) and broadband photodetection (visible‐1064 nm). Because of the effective photogating effect induced by electrons trapped in the localized states of MoTe2, the devices demonstrate an extremely high photoconductive gain of 4.69 × 108 and detectivity of 1.55 × 1011 cm Hz1/2 W?1. Moreover, flexible devices based on the MoTe2/graphene heterostructure on flexible substrate also retains a good photodetection ability after thousands of times bending test (1.2% tensile strain), with a high responsivity of ≈60 A W?1 at 1064 nm at V DS = 1 V, which provides a promising platform for highly efficient, flexible, and low cost broadband NIR photodetectors. 相似文献
1000.
Surface Energy and Surface Stability of Ag Nanocrystals at Elevated Temperatures and Their Dominance in Sublimation‐Induced Shape Evolution 下载免费PDF全文
Long‐Bing He Lei Zhang Xiao‐Dong Tan Lu‐Ping Tang Tao Xu Yi‐Long Zhou Zhan‐Yong Ren Yun Wang Chun‐Yu Teng Li‐Tao Sun Jian‐Feng Nie 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(27)
The surface energy and surface stability of Ag nanocrystals (NCs) are under debate because the measurable values of the surface energy are very inconsistent, and the indices of the observed thermally stable surfaces are apparently in conflict. To clarify this issue, a transmission electron microscope is used to investigate these problems in situ with elaborately designed carbon‐shell‐capsulated Ag NCs. It is demonstrated that the {111} surfaces are still thermally stable at elevated temperatures, and the victory of the formation of {110} surfaces over {111} surfaces on the Ag NCs during sublimation is due to the special crystal geometry. It is found that the Ag NCs behave as quasiliquids during sublimation, and the cubic NCs represent a featured shape evolution, which is codetermined by both the wetting equilibrium at the Ag–C interface and the relaxation of the system surface energy. Small Ag NCs (≈10 nm) no longer maintain the wetting equilibrium observed in larger Ag NCs, and the crystal orientations of ultrafine Ag NCs (≈6 nm) can rotate to achieve further shape relaxation. Using sublimation kinetics, the mean surface energy of Ag NCs at 1073 K is calculated to be 1.1–1.3 J m?2. 相似文献