| 1. |
- Liang, Xifeng, et al.
(författare)
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On the aerodynamic loads when a high speed train passes under an overhead bridge
- 2020
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Ingår i: Journal of Wind Engineering and Industrial Aerodynamics. - : Elsevier BV. - 0167-6105. ; 202
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Tidskriftsartikel (refereegranskat)abstract
- The aerodynamic loads on the overhead bridge bottom surface induced by train passage are reported in this paper. Both moving model test and numerical simulation approaches at the 1:20 scale are used. The numerical work is validated through both mesh independence tests and comparison with experimental data. Typical pressure variation curves are plotted and compared with previous studies. The peak pressure values’ dependence on the Reynolds number is considered through four sets of experiments with different train running speeds. The peak pressure coefficient distribution law for the bridge bottom surface is presented. Differences in the pressure distribution in different bridge bottom areas are explained based on more detailed flow field information. The influence of the bridge height on the aerodynamic load magnitude and time interval is presented. Moreover, the application of the CEN Standard to practical engineering issues is discussed.
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| 2. |
- Liu, X., et al.
(författare)
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Surface roughness prediction method of titanium alloy milling based on CDH platform
- 2022
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Ingår i: The International Journal of Advanced Manufacturing Technology. - : Springer Nature. - 0268-3768 .- 1433-3015. ; 119:11-12, s. 7145-7157
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Tidskriftsartikel (refereegranskat)abstract
- Generally, off-line methods are used for surface roughness prediction of titanium alloy milling. However, studies show that these methods have poor prediction accuracy. In order to resolve this shortcoming, a prediction method based on Cloudera’s Distribution including Apache Hadoop (CDH) platform is proposed in the present study. In this regard, data analysis and process platform are designed based on the CDH, which can upload, calculate, and store data in real time. Then this platform is combined with the Harris hawk optimization (HHO) algorithm and pattern search strategy, and an improved Harris hawk optimization optimization (IHHO) method is proposed accordingly. Then this method is applied to optimize the support vector machine (SVM) algorithm and predict the surface roughness in the CDH platform. The obtained results show that the prediction accuracy of IHHO method reaches 95%, which is higher than the conventional methods of SVM, BAT-SVM, gray wolf optimizer (GWO-SVM), and whale optimization algorithm (WOA-SVM).
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| 3. |
- Wei, Xiao-Ping, et al.
(författare)
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Investigations on electronic, Fermi surface, Curie temperature and optical properties of Zr2CoAl
- 2017
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Ingår i: Journal of Solid State Chemistry. - : ACADEMIC PRESS INC ELSEVIER SCIENCE. - 0022-4596 .- 1095-726X. ; 247, s. 97-104
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Tidskriftsartikel (refereegranskat)abstract
- Using full-potential local-orbital minimum-basis along with spin-polarized relativistic Korringa-Kohn-Rostoker methods, we study the electronic, Fermi surface, Curie temperature and optical properties of Zr2CoAl alloy. The alloy with Li2AgSb and Cu2MnAl structures are compared in terms of magnetic properties, and the electronic structures in two structures are also discussed. According to the calculated electronic states, it finds that the Zr2CoAl with Li2AgSb structure is half-metallic ferromagnet with an integral magnetic moment of 2.00 mu(beta), meanwhile we also notice the d-d and p-d hybridizations are responsible for the formation of minority-spin gap, furthermore, the fat-bands are applied to discuss the mixture between d and p electrons in the vicinity of the Fermi level. The Fermi surfaces related to the valence bands are constructed, and it is found that the spin-up valence bands 26, 27 and 28 across the Fermi energy dominate the nature of electrons. By mapping the system onto a Heisenberg Hamiltonian, we obtain the exchange coupling parameters, and observe that the Zr(A)-Co(C) and Zr(A)-Zr(B) interactions provide a major contribution for exchange interactions. Based on the calculated exchange coupling parameters, the Curie temperature is estimated to be 287.86 K at equilibrium, and also the dependence of Curie temperature on lattice constant related to the tunable Curie temperature in Zr2CoAl alloy is studied. Finally, we report the optical properties of Zr2CoAl alloy, and present the photon energy dependence of the absorption, the optical conductivity and the loss function.
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| 4. |
- Zhang, P., et al.
(författare)
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A Cu-Based Nanoparticulate Film as Super-Active and Robust Catalyst Surpasses Pt for Electrochemical H2 Production from Neutral and Weak Acidic Aqueous Solutions
- 2016
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Ingår i: Advanced Energy Materials. - : Wiley-VCH Verlagsgesellschaft. - 1614-6832 .- 1614-6840. ; 6:8
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Tidskriftsartikel (refereegranskat)abstract
- Electrocatalysts that are stable and highly active at low overpotential (η) under mild conditions as well as cost-effective and scalable are eagerly desired for potential use in photo- and electro-driven hydrogen evolution devices. Here the fabrication and characterization of a super-active and robust Cu-CuxO-Pt nanoparticulate electrocatalyst is reported, which displays a small Tafel slope (44 mV dec-1) and a large exchange current density (1.601 mA cm-2) in neutral buffer solution. The catalytic current density of this catalyst film reaches 500 mA cm-2 at η = -390 ± 12 mV and 20 mA cm-2 at η = -45 ± 3 mV, which are significantly higher than the values displayed by Pt foil and Pt/C electrodes in neutral buffer solution and even comparable with the activity of Pt electrode in 0.5 m H2SO4 solution.
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| 5. |
- Hu, Ji-Chong, et al.
(författare)
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Oxidation behavior of Ni-based superalloy GH4738 under tensile stress
- 2024
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Ingår i: Rare Metals. - : NONFERROUS METALS SOC CHINA. - 1001-0521 .- 1867-7185.
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Tidskriftsartikel (refereegranskat)abstract
- Revealing the oxidation behavior of superalloys is crucial for optimizing material properties and extending service life. This study investigated the oxidation behavior of superalloy GH4738 under stress states at 850 degrees C. High-throughput specimens were fabricated to withstand different stresses at the same time. Isothermal oxidation samples were analyzed using the mass gain method to obtain oxidation kinetic curves. The results show that the external stress below 200 MPa could improve the oxidation resistance of the GH4738. With tensile stress increasing, the oxide layer becomes thinner, denser and more complete, while internal oxidation decreases. The tensile stress alters the structure of the external oxide layer from a two-layer to a three-layer configuration. The Cr2O3 oxide layer inhibits the outward diffusion of Ti, leading to Ti enrichment at the oxide-matrix interface and altering the oxidation mechanism of GH4738.
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| 6. |
- Sun, Liang Liang, et al.
(författare)
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Bounding the Amount of Entanglement from Witness Operators
- 2024
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Ingår i: Physical Review Letters. - 0031-9007. ; 132:11
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Tidskriftsartikel (refereegranskat)abstract
- We present an approach to estimate the operational distinguishability between an entangled state and any separable state directly from measuring an entanglement witness. We show that this estimation also implies bounds on a variety of other well-known entanglement quantifiers. This approach for entanglement estimation is then extended to both the measurement-device-independent scenario and the fully device-independent scenario, where we obtain nontrivial but suboptimal bounds. The procedure requires no numerical optimization and is easy to compute. It offers ways for experimenters to not only detect, but also quantify, entanglement from the standard entanglement witness procedure.
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| 7. |
- Sun, Yifan, et al.
(författare)
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Sensitive parameters affecting dark current characteristics of SCD
- 2021
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 12061
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Konferensbidrag (refereegranskat)abstract
- The sensitive parameters affecting the dark current characteristics are further studied by using InAs/GaSb type II superlattice (T2SL) pBpp structure long wavelength Infrared photodetectors. Generation of recombination (G-R), surface leakage current and tunneling current are the main components of dark current. Using pBpp structure can suppress them effectively, thereby decreasing dark current. Based on the k · p method, the band structure of InAs/GaSb T2SL and InAs/AlSb T2SL can be obtained by solving the 8-band k · p model. We have calculated different doping levels of pBpp detector and different layer thicknesses of pBpp detector. For pBpp device, we consider the dark current for different contact layer doping and different absorber layer doping. We also study the influence of different contact layer thicknesses and different absorber layer thicknesses on dark current. The dark current of pBpp detector is dominant by tunneling current at low temperature, and diffusion is the main limiting mechanism in dark current at high temperature, for barrier layer inhibits generation-recombination contribution. Eventually, the dark current of a pBpp structure has been calculated for versus voltage at 77 K.
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| 8. |
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| 9. |
- Chen, Yanping, et al.
(författare)
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PKU-20 : A new silicogermanate constructed from sti and asv layers
- 2016
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Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 224, s. 384-391
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Tidskriftsartikel (refereegranskat)abstract
- A new silicogermanate (PKU-20) was hydrothermally synthesized using triethylisopropylammonium cation as the structure directing agent in the presence of fluoride. Its structure was determined from a combination of synchrotron single crystal X-ray diffraction and powder X-ray diffraction data. PKU-20 crystallizes in the monoclinic space group C2/m, with the lattice parameters of a = 18.5901(6) angstrom, b = 13.9118 (4) angstrom, c = 22.2614(7) angstrom and beta = 100.1514 (12)degrees. The framework of PKU-20 is constructed from an alternate stacking of sti and asv layers. The sti layer is exactly the same as that in the STI framework, while the asv layer is a new layer sliced off from the ASV framework parallel to the (112) plane. The takeout scheme of the layer is discussed on the basis of a composite building unit D4R-/au-D4R. PKU-20 possesses a two-dimensional channel system, where the 10-ring channels parallel to the [010] direction are intercrossed by 12-ring pockets along the [101] direction.
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| 10. |
- Sun, Xiaoyu, et al.
(författare)
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Revealing microstructural degradation mechanism induced by interdiffusion between Amdry365 coating and IN792 superalloy
- 2024
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Ingår i: Materials and Design. - : ELSEVIER SCI LTD. - 1873-4197 .- 0264-1275. ; 241
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Tidskriftsartikel (refereegranskat)abstract
- Metallic coatings are widely employed to improve the oxidation resistance of superalloys. However, the interdiffusion between the metallic coatings and the superalloys leads to microstructural degradation in both. Some of the underlying degradation mechanisms are still elusive, e.g., the γ′ (Ni3Al) phase depletion in superalloys, where a large amount of γ′ precipitates are dissolved in the γ matrix even though the incoming Al from coatings indeed increases the Al content. Here, we investigated the interdiffusion behavior between the Amdry365 coating and the IN792 superalloy at 1100 °C, using multiple microscopic techniques and thermodynamics calculations. Our results showed an excellent agreement between experiments and thermodynamics simulations, indicating the dominant role of Al on the initial diffusion-induced phase transitions. We proposed the Al-Cr interference effect to account for the pile-up behavior of Cr and the reduced Al content near the coating/superalloy interface. The local phase equilibrium calculations revealed that the γ′ depletion in the superalloy is primarily attributed to the loss of γ′-forming elements, such as Ta and Ti. Our findings opened up an avenue for studies on the superalloy/coating interdiffusion, contributing to reducing this damaging impact.
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