4,074 research outputs found

    Contagion: China Evergrande Group’s Collapse and its impact on Belt and Road Stock Indices

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    The Evergrande Group is a giant: a company that has liabilities proportional to 2% of China’s overall GDP. While there is evidence that Evergrande’s collapse harmed China and its surrounding economies, this thesis analyzes Evergrande’s default within the context of China’s central foreign policy: the Belt and Road Initiative. Through four selected event dates, a difference in means and medians test and standard panel regression is conducted to analyze differences in impacts for Belt and Road and non-Belt and Road participating countries’ stock indices. This paper’s hypothesis implies that Belt and Road countries would see comparatively more negative impacts on their stock indices. Empirical analysis reveals that events before and after Evergrande’s September 2021 warning were statistically different for both Belt and Road and non-Belt and Road groups, with Fitch Ratings’ declaration of Evergrande’s default being the most detrimental. On the other hand, warnings the year prior to Evergrande’s widespread media coverage in September 2020 opposed the hypothesis, seeing non-Belt and Road countries being more negatively affected. Further findings suggest, however, that Belt and Road countries relative to non-Belt and Road countries showcase comparatively worse stock return performance across the majority of the events, fortifying the hypothesis that Belt and Road countries were more negatively impacted by Evergrande’s default relative to non-Belt and Road countries

    Numerical Modeling of Dust Dynamics around Small Asteroids

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    Dynamics of dust transport around an airless body has been a focused area of research in recent years, however, various challenging aspects still remain to be addressed. This paper presents an investigation of charged dust transport and distribution around small asteroids utilizing a full particle Particle-in-Cell (PIC) model to simulate plasma flow around an asteroid and calculate surface charging self-consistently from charge deposition on asteroid. Material properties of asteroid are also explicitly included in the simulation. PIC simulation results are fed into a 3D dust dynamics model to simulate charged dust levitation, transport and distribution. In addition to electrostatic and gravitational forces, the dynamics of dust surface impacts and asteroid body rotation are also included in the model. We discuss the effects on dust levitation and transport by comparing dust grain charge-mass ratio, local electrostatic field and dust grain size. We present simulation results of dust distribution around small spherical asteroids. The study highlights the sensitivity to electrostatic field and grain characteristics while following the general trend that gravity dominates in the far field, where as local electric field prevails at low altitude

    Scattering of swell by currents

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    The refraction of surface gravity waves by currents leads to spatial modulations in the wave field and, in particular, in the significant wave height. We examine this phenomenon in the case of waves scattered by a localised current feature, assuming (i) the smallness of the ratio between current velocity and wave group speed, and (ii) a swell-like, highly directional wave spectrum. We apply matched asymptotics to the equation governing the conservation of wave action in the four-dimensional position--wavenumber space. The resulting explicit formulas show that the modulations in wave action and significant wave height past the localised current are controlled by the vorticity of the current integrated along the primary direction of the swell. We assess the asymptotic predictions against numerical simulations using WAVEWATCH III for a Gaussian vortex. We also consider vortex dipoles to demonstrate the possibility of `vortex cloaking' whereby certain currents have (asymptotically) no impact on the significant wave height. We discuss the role of the ratio of the two small parameters characterising assumptions (i) and (ii) above and show that caustics are only significant for unrealistically large values of this ratio, corresponding to unrealistically narrow directional spectra

    Broad-Wavevector Spin Pumping of Flat-Band Magnons

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    We report the experimental observation of large spin pumping signals in YIG/Pt system driven by broad-wavevector spin-wave spin current. 280 nm-wide microwave inductive antennas offer broad-wavevector excitation which, in combination with quasi-flatband of YIG, allows a large number of magnons to participate in spin pumping at a given frequency. Through comparison with ferromagnetic resonance spin pumping, we attribute the enhancement of the spin current to the multichromatic magnons. The high efficiency of spin current generation enables us to uncover nontrivial propagating properties in ultra-low power regions. Additionally, our study achieves the spatially separated detection of magnons, allowing the direct extraction of the decay length. The synergistic combination of the capability of broad-wavevector excitation, enhanced voltage signals, and nonlocal detection provides a new avenue for the electrical exploration of spin waves dynamics

    Realization of the welding of individual TiO2 semiconductor nano-objects using a novel 1D Au80Sn20 nanosolder

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    Individual semiconductor nanowires (NWs) TiO2 were successfully welded together using novel one-dimensional (1D) Au80Sn20 (mass ratio) nanosolders at the nano-scale for the first time. The nanosolders were electrodeposited into nanoporous templates to form a 1D structure, and their morphology, crystal structure, chemistry and elemental electronic states were systematically characterized. Individual Au80Sn20 nanowires were proved to consist of mixed crystal phases, including a Au5Sn phase with a trigonal structure, a AuSn phase with a hexagonal structure and a small SnO2 phase produced the by oxidation of the surface portion. Chemical analysis indicated that the composition was Au80Sn20. The testing of the welding capability by either in situ TEM or in situ SEM by nanomanipulators and infiltration experiment revealed a good wet ability and diffusion ability between the Au80Sn20 nanosolder and the TiO2 nanowire. It is believed that our study contributes to the field a special nanosolder for future nano-scale welding techniques, which also make the bonding of titanium-based semiconductor oxide nanomaterials at the nano-scale a reality
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