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CEO succession planning and market reactions to CEO turnover announcements
No full textThis study investigates how capital market investors assess CEO succession planning in the context of CEO turnover events. Conducting empirical tests using a manually collected sample of 676 CEO turnover cases, we find that CEO succession planning mitigates the negative association between CEO performance and market reactions to CEO turnover announcements. Further analyses reveal that our results are driven by firms with strong corporate governance. Overall, our findings suggest that CEO succession planning disclosure reduces investors??? concerns about firm performance in the event of CEO turnover
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Flow control over a circular cylinder using a slot and axially arranged holes
No full textCircular cylinder flow is controlled using a slot and axially arranged holes (AAH) at a Reynolds number of 32000. When the slot and AAH are placed at small incidence angles from the free-stream direction, the passive jet generated on the leeward cylinder side pushes the wake vortex downstream, reducing the drag compared to the baseline cylinder. If the incidence angle is larger than the critical angle, the alternate blowing and suction induced by the slot and AAH promote a boundary-layer transition on one side and a shear-layer transition on the other. The earlier transition to turbulent flow substantially shortens the separated shear layers on both sides, shifting the wake formation region toward the base and leading to an increase in drag. The AAH has a higher critical incidence angle than the same-size slot, as the passive jet developed from the AAH undergoes a transition to alternate blowing and suction at a higher incidence angle than the slot. Just before the incidence angle of the AAH reaches the critical angle, the weak jet flow induced on the windward cylinder side delays the boundarylayer separation through early separation and laminar reattachment without shortening the separated shear layer, thereby allowing additional drag reduction
Efficient Second-Harmonic Generation from Dielectric Inter-subband Polaritonic Metasurfaces Coupled to Lattice Resonance
No full textNonlinear optical metasurfaces offer a possibility to perform frequency mixing without the phase-matching constraints of bulk nonlinear crystals and with control of the local nonlinear response at a sub-wavelength scale. Nonlinear inter-subband polaritonic metasurfaces created by combining the semiconductor heterostructures with quantum-engineered inter-subband nonlinear response and electromagnetically engineered metal-clad nanoresonators offer by far the largest second-order nonlinear response of all condensed matter systems reported to date. However, the nonlinear optical response of these metasurfaces is limited by optical intensity saturation in the nanoresonator hot spots that prevented the achievement of power conversion efficiencies over 0.2% in three-wave mixing experiments. In this study, we propose and experimentally demonstrate dielectric inter-subband polaritonic metasurfaces for second-harmonic generation that achieve 0.37% power conversion efficiency. Our structure is created by a new design approach that combines dielectric resonators inducing Mie resonant modes with a lattice resonance to achieve a uniform and high field enhancement throughout the meta-atom volume
Advances in Intrinsically Stretchable Light-Emitting Diodes
No full textIntrinsically stretchable light-emitting diodes, composed of stretchable electrodes, charge transport layers, and luminescent materials, have garnered significant interest for enhancing human well-being and advancing the field of deformable electronics. Various luminescent materials, such as perovskites and organics, have been integrated with stretchable elastomers to function as the stretchable emissive layers in these intrinsically stretchable LEDs. Stretchable conductors including Ag nanowire based percolating structures and conducting polymers have been utilized as stretchable transparent electrode. Despite this progress, their performances in terms of efficiency and stability remain challenging compared to their structurally stretchable and rigid LED counterparts. This review offers a comprehensive overview of recent advancements in intrinsically stretchable LEDs, focusing on material innovations
Reversible Pd Catalysts Supported on Hierarchical Titanate Nanosheets for an <i>N</i>-Methylindole-Based Liquid Organic Hydrogen Carrier
No full textReversible hydrogenation and dehydrogenation processes were investigated in a liquid organic hydrogen carrier (LOHC) system by employing a single-catalyst approach. Key hydrogen-involved catalytic behaviors, including adsorption and migration, play crucial roles in reactivity. To facilitate these behaviors at the active sites on the catalyst surface during the LOHC process, a defective metal oxide support was utilized. Herein, a Pd catalyst was prepared by using hierarchical titanate nanosheets (HTN) synthesized via solvothermal synthesis. Compared to commercial TiO2 and hierarchical TiO2 (HT), which was synthesized by the calcination of HTN, HTN exhibited a higher density of acidic sites and oxygen vacancies. Density functional theory calculations confirmed that hydrogen spillover occurred more readily on the defective HTN surface than on the TiO2 (101) surface. The Pd/HTN catalyst demonstrated superior catalytic activity for both the hydrogenation and dehydrogenation reactions in the N-methylindole-based LOHC system. The hydrogen uptake of Pd/HTN catalyst (4.73 wt %) was 3 times higher than that of other Pd catalysts (similar to 1.57 wt %). The single Pd/HTN catalyst successfully accomplished reversible hydrogen storage and release within the LOHC system in one reactor