Browsing by Author "Wang, H."
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Item New Intrinsic Mechanism on Gum-Like Superelasticity of Multifunctional AlloysLiu, J. -P; Wang, Y. -D; Hao, Y. -L; Wang, Y.; Nie, Z. -H; Wang, D.; Ren, Y.; Lu, Z. -P; Wang, Jinguo; Wang, H.; Hui, X.; Lu, Ning; Kim, Moon J.; Yang, R.Ti-Nb-based Gum Metals exhibit extraordinary superelasticity with ultralow elastic modulus, superior strength and ductility, and a peculiar dislocation-free deformation behavior, most of which challenge existing theories of crystal strength. Additionally, this kind of alloys actually displays even more anomalous mechanical properties, such as the non-linear superelastic behavior, accompanied by a pronounced tension-to-compression asymmetry, and large ductility with a low Poisson's ratio. Two main contradictory arguments exist concerning the deformation mechanisms of those alloys, i.e., formation of reversible nanodisturbance and reversible martensitic transformation. Herein we used the in-situ synchrotron high-energy X-ray scattering technique to reveal the novel intrinsic physical origin of all anomalous mechanical properties of the Ti-24Nb-4Zr-8Sn-0.10O alloy, a typical gum-like metal. Our experiments provide direct evidence on two different kinds of interesting, stress-induced, reversible nanoscale martensitic transitions, i.e., the austenitic regions with B2 structure transform to α" martensite and those with BCC structure transform to ō martensite.Item Reactivity of Atomic Layer Deposition Precursors with OH/H₂O-Containing Metal Organic Framework Materials(American Chemical Society) Tan, Kui; Jensen, S.; Feng, L.; Wang, H.; Yuan, S.; Ferreri, M.; Klesko, Joseph P.; Rahman, Rezwanur; Cure, Jeremy; Li, J.; Zhou, H. -C; Thonhauser, T.; Chabal, Yves J.; 0000-0002-5167-7295 Tan, K); 0000-0003-3989-8009 (Klesko, JP); 0000-0002-8109-4787 (Rahman, R); 0000-0002-6080-6909 (Cure, J); 0000-0002-6435-0347 (Chabal, YJ); Tan, Kui; Klesko, Joseph P.; Rahman, Rezwanur; Cure, Jeremy; Chabal, Yves J.Metal organic frameworks (MOFs) are a class of three-dimensional porous architectures that can be chemically functionalized. The ability of atomic layer deposition (ALD) to incorporate metal atoms or functional groups into MOFs offers an interesting alternative to chemically modify MOFs for applications such as catalysis and gas separation, for which transport, adsorption, and the reaction of gases are critical. Optimization of these deposition processes requires an understanding of the underlying reaction mechanisms that is best derived from in situ characterization. We have therefore combined in situ infrared spectroscopy, X-ray photoelectron spectroscopy with in situ sputtering, and ab initio calculations to elucidate the reaction mechanisms of the common ALD precursors trimethylaluminium (TMA), diethylzinc (DEZ), and TiCl 4 with several Zr-MOFs containing hydroxyl (OH) and water (H₂O) groups. Focusing on the OH and H₂O groups is particularly revealing because it makes it possible to explore the reactivity dependence on the chemical and structural (i.e., sterics) environments. We find that the reactivity of the OH groups in the Zr₆(μ₃ -OH)₄ (μ₃ -O)₄ (OH)ₓ (OH₂) y cluster node is highly dependent on their location, accessibility, and chemical environment. For instance, the activation temperature for the reaction of the OH groups of Zr₆ clusters with TMA decreases with the node connectivity: 200, 150, and 24 °C for UiO-66-NH₂ , Zr-abtc, and MOF-808, respectively. Interestingly, the hydroxyl groups in unfunctionalized UiO-66 do not react with TMA molecules. Ab initio calculations reveal that the NH₂ group is directly responsible for catalyzing this reaction by anchoring the TMA molecule in close proximity to the target OH group. Finally, we show that TMA easily reacts with water adsorbed on the external surfaces of wet MOF crystals at room temperature, forming a thick Al₂O₃ blocking layer on the periphery of the MOF crystals. These findings provide a basis for the design and modification of MOFs by ALD processes. © 2019 American Chemical Society.Item Upper Critical Field and Kondo Effects in Fe(Te{0.9} Se{0.1}) Thin Films by Pulsed Field Measurements(Nature Publishing Group, 2016-02-10) Salamon, Myron B.; Cornell, N.; Jaime, M.; Balakirev, F. F.; Zakhidov, Anvar A.; Huang, J.; Wang, H.; 0000 0001 0965 7058 (Salamon, MB); 0000-0003-3983-2229 (Zakhidov, AA); Salamon, Myron B.; Zakhidov, Anvar A.The transition temperatures of epitaxial films of Fe(Te{0.9} Se {0.1}) are remarkably insensitive to applied magnetic field, leading to predictions of upper critical fields B{c2}(T = 0) in excess of 100 T. Using pulsed magnetic fields, we find B{c2}(0) to be on the order of 45 T, similar to values in bulk material and still in excess of the paramagnetic limit. The same films show strong magnetoresistance in fields above B{c2}(T), consistent with the observed Kondo minimum seen above T{c}. Fits to the temperature dependence in the context of the WHH model, using the experimental value of the Maki parameter, require an effective spin-orbit relaxation parameter of order unity. We suggest that Kondo localization plays a similar role to spin-orbit pair breaking in making WHH fits to the data.Item Viral Marketing of Online Game by DS Decomposition In Social Networks(Elsevier B.V.) Gao, C.; Du, H.; Wu, Weili; Wang, H.; 56851698 (Wu, W); Wu, WeiliIn social networks, the spread of influence has been studied extensively, but most efforts in existing literature are made on the product used by a single person. This paper attempts to address the product which is used by many persons such as the online game. When multiple people participate in one game, interaction between users is accompanied by browsing and clicking on advertisements, and operators can also earn certain advertising revenues. All these revenues are related to information interaction between people involved in one game. We use game profit to represent all of the revenues gained from players involved in one game and model the game profit maximization problem in social networks, which finds a seed set to maximize the game profit between players who are influenced to buy the game. We prove that the problem is NP-hard and the objective function is neither submodular nor supermodular. To solve it, we decompose it into the Difference between two Submodular functions (DS decomposition) and propose four heuristic algorithms. To address the complexity of computing objective function, we design a new sampling method based on reverse reachable set technology. Experiment results on real datasets show that our approaches perform well. ©2019 Elsevier B.V.