51,668 research outputs found

    Proton modified Pt zeolite fuel cell electrocatalysts

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    NaY Zeolite is selected as a suitable material to host 1.5 wt% Platinum (Pt) loading on zeolite using ion exchange method (a) Pt(NH3)4(NO3)2 without excess NH4NO3 nitrate and (b) Pt(NH3)4(NO3)2 with excess NH4NO3 nitrate. The structure/reactivity relationship of Pt nanoparticle has been experimentally studied via Nafion@ bound electrodes to investigate the interaction nature of Pt with zeolite and electron transfer using the extended X-ray adsorption fine structure (EXAFS) and Pt particle was predicted at 0.7 – 1.5 (nm). Pt oxides can be electrochemically reduced via a hydrogen ‘spillover’ phenomenon. A highly dispersed small Pt particle distribution can be achieved with excessive H+ ions on zeolite acidic sites

    Sign Changes of Intrinsic Spin Hall Effect in Semiconductors and Simple Metals: First-Principles Calculations

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    First-principles calculations are applied to study spin Hall effect in semiconductors and simple metals. We found that intrinsic spin Hall conductivity (ISHC) in realistic materials shows rich sign changes, which may be used to distinguish the effect from the extrinsic one. The calculated ISHC in n-doped GaAs can be well compared with experiment, and it differs from the sign obtained from the extrinsic effect. On the other hand, the ISHC in W and Au, which shows opposite sign respectively, is robust and not sensitive to the disorder.Comment: 4 pages, 4 figure

    On the Finite-Time Blowup of a 1D Model for the 3D Axisymmetric Euler Equations

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    In connection with the recent proposal for possible singularity formation at the boundary for solutions of 3d axi-symmetric incompressible Euler's equations (Luo and Hou, 2013), we study models for the dynamics at the boundary and show that they exhibit a finite-time blow-up from smooth data.Comment: A paragraph at the end of Section 2 and an appendix discussing kinetic energy conservation are adde

    Contract Violations in the Construction Projects: How Contractual Obligations are Reached Affects Contractual and Reputational Enforcement

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    Contract violations are frequent in construction projects due to the higher level of uncertainty and complexity in these projects. However, enforcement after a violation, including contractual and reputational enforcement, has received limited attention. This study distinguishes between three types of violations, i.e., violations of documented obligations (letter violations), violations of tacitly agreed obligations (spirit violations #1), and violations of unilaterally assumed obligations (spirit violations #2), based on the documentation and mutuality dimensions. Furthermore, this study compares the impacts of different types of violations on contractual and reputational enforcement and explores the mediating role of relational risk perception in the above impacts. By using the data collected from Chinese general contractors, this study concludes that compared with spirit violations #2, letter violations and spirit violations #1 will lead to more severe contractual enforcement and reputational enforcement while the latter two have no significant differences of their influence on the severity of enforcement. The mediating effects of relational risk perception are empirically supported. By doing this, this study contributes to the literature on contractual governance by exploring the effects of contract structure, especially the undocumented elements of contracts, on enforcement, and responds to the recent calls for the positive role of contract ambiguity. In addition, this study fills the gaps in the scarce literature on reputational enforcement and expands the studies on the antecedents of it. Project managers can benefit from this study by recognizing the employment of reputational enforcement and the making better alignment between different types of violations and enforcement
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