Rational Panics, Absorbing Regime Switching and Stock Market

A government policy regarding the reduction of state shares in state-owned enterprises (SOE) triggered a crash in the Chinese stock market. The sus- tained depression even after policy adjustments constitutes a puzzle— the so called “state-share paradox.”The empirical evidence shows that the sustained depression is supported by a regime switching model with an absorbing state. The theoretical explanation developed in this paper arises from the concept of rational panics, which generates an inverted-S actual demand curve and gives rise to potential multiple equilibria. Rational panics hypothesis in this paper suggests that the dual pricing system and the quota on the overall stock supply represent major policy failuresChinese Stock Market, Market Crash, and Inverted-S Demand

Elastic wave confinement and absorption in a dissipative metamaterial

In this paper, we report on the theoretical investigation of the elastic wave confinement and absorption in a dissipative metamaterial, which is constituted of two-dimensional phononic crystals with binary composite material defect composed of aluminum discs hemmed around by damped rubber. Based on an efficient finite element method in combination with a super cell technique, the dispersion relations and the power transmission spectra of the proposed dissipative metamaterialshave been calculated. Numerical results show that the proposed dissipative metamaterials can yield complete band gap as well as defect states. Elastic waves of the specific frequency of the defect models in the range of gap frequencies have been confined and dissipated simultaneously in the point defect or along the line defects. In contrast to the traditional damper for vibration energy dissipation, the proposed dissipative metamaterials can be equivalent to elastic wave energy attractor and possess significant higher energy dissipation rate for ambient distributed vibration. These elastic wave confinement and dissipation properties of the proposed dissipative metamaterials can potentially be utilized to generate vibration absorbers as well as optimization design of damped structure

Highly emissive, selective and omnidirectional thermal emitters mediated by machine learning for ultrahigh performance passive radiative cooling

Real-world passive radiative cooling requires highly emissive, selective, and omnidirectional thermal emitters to maintain the radiative cooler at a certain temperature below the ambient temperature while maximizing the net cooling power. Despite various selective thermal emitters have been demonstrated, it is still challenging to achieve these conditions simultaneously because of the extreme complexity of controlling thermal emission of photonic structures in multidimension. Here we demonstrated machine learning mediated hybrid metasurface thermal emitters with a high emissivity of ~0.92 within the atmospheric transparency window 8-13 {\mu}m, a large spectral selectivity of ~1.8 and a wide emission angle up to 80 degrees, simultaneously. This selective and omnidirectional thermal emitter has led to a new record of temperature reduction as large as ~15.4 degree under strong solar irradiation of ~800 W/m2, significantly surpassing the state-of-the-art results. The designed structures also show great potential in tackling the urban heat island effect, with modelling results suggesting a large energy saving and deployment area reduction. This research will make significant impact on passive radiative cooling, thermal energy photonics and tackling global climate change

Coastal upwelling and redox variations in the northwestern Tarim Basin (northwest China) during the Middle-Late Ordovician: implication for paleo-depositional conditions of the organic matter enrichment in the Saergan Formation

The black shales of the Saergan Formation, which represent one of the main hydrocarbon source rocks in the Tarim Basin, witnessed a time span of organic matter enrichment by profound changes in the Earth System. A multi-proxy geochemistry study was carried out on the samples of the Saergan Formation to reconstruct the depositional environment and to explore the mechanism of organic matter enrichment of the unit at the Yingshanbeipo section, Keping area, northwest Tarim. Elemental and TOC data are suggestive of an upwelling setting, with a less pronounced oxygen minimum zone (OMZ) compared to the highly productive Peru and Namibian margins. Ferruginous anoxic bottom water conditions prevailed during most time of the deposition, with suboxic conditions dominating the basal and the top parts of the studied unit. As a whole, primary productivity seems to be the dominating factor that controlled the micronutrients and OM accumulations in the Saergan Formation whereas the role of benthic redox conditions may have been subordinate. The variations in primary productivity and bottom water redox conditions were resulted by the multiple, interacting environmental factors including nutrient supply regulated by oceanic circulation and climate changes, and relative sea-level fluctuations

Laboratory Study on the Use of Urease-Induced Calcium Carbonate Precipitation for Stabilization of Coal Fly Ash

Coal fly ash (FA) dust negatively impacts human health and the environment. This study aimed to prevent wind erosion through the technology of enzyme-induced carbonate precipitation (EICP) to improve the surface stability of FA. In order to investigate the influence of urease activity, salt solution ratio, and polyacrylamide (PAM) concentration on the EICP process, unconfined compressive strength (UCS) test, sieving test, and wind tunnel test was carried out in the laboratory. Scanning electron microscopy (SEM) was also used to analyze the microscopic crystal morphology characteristics of mineralized products. The results showed that the wind erosion rate of the samples treated with EICP reduced significantly (the minimum wind erosion rate is 1.986 mg/(m2·min)) due to the crystal bridge function of CaCO3, while the UCS of these samples increased clearly. Appropriately increasing urease activity in the treatment solution contributed to the increased CaCO3 content and microscopic size. Excess urea concentration had a certain inhibitory effect on urease activity. The addition of PAM provided more nucleation sites for the EICP process and improved the strength of the cementation. These findings suggested that the EICP-PAM was a promising technique for the protection of FA sites from wind erosion

Laboratory Study on the Use of Urease-Induced Calcium Carbonate Precipitation for Stabilization of Coal Fly Ash

Coal fly ash (FA) dust negatively impacts human health and the environment. This study aimed to prevent wind erosion through the technology of enzyme-induced carbonate precipitation (EICP) to improve the surface stability of FA. In order to investigate the influence of urease activity, salt solution ratio, and polyacrylamide (PAM) concentration on the EICP process, unconfined compressive strength (UCS) test, sieving test, and wind tunnel test was carried out in the laboratory. Scanning electron microscopy (SEM) was also used to analyze the microscopic crystal morphology characteristics of mineralized products. The results showed that the wind erosion rate of the samples treated with EICP reduced significantly (the minimum wind erosion rate is 1.986 mg/(m2·min)) due to the crystal bridge function of CaCO3, while the UCS of these samples increased clearly. Appropriately increasing urease activity in the treatment solution contributed to the increased CaCO3 content and microscopic size. Excess urea concentration had a certain inhibitory effect on urease activity. The addition of PAM provided more nucleation sites for the EICP process and improved the strength of the cementation. These findings suggested that the EICP-PAM was a promising technique for the protection of FA sites from wind erosion

Elastic wave confinement and absorption in a dissipative metamaterial

158-163In this paper, we report on the theoretical investigation of the elastic wave confinement and absorption in a dissipative metamaterial, which is constituted of two-dimensional phononic crystals with binary composite material defect composed of aluminum discs hemmed around by damped rubber. Based on an efficient finite element method in combination with a super cell technique, the dispersion relations and the power transmission spectra of the proposed dissipative metamaterialshave been calculated. Numerical results show that the proposed dissipative metamaterials can yield complete band gap as well as defect states. Elastic waves of the specific frequency of the defect models in the range of gap frequencies have been confined and dissipated simultaneously in the point defect or along the line defects. In contrast to the traditional damper for vibration energy dissipation, the proposed dissipative metamaterials can be equivalent to elastic wave energy attractor and possess significant higher energy dissipation rate for ambient distributed vibration. These elastic wave confinement and dissipation properties of the proposed dissipative metamaterials can potentially be utilized to generate vibration absorbers as well as optimization design of damped structure

Large band gaps in two-dimensional phononic crystals with Jerusalem cross slot structures

813-818The band gap properties in a novel two-dimensional phononic crystal with Jerusalem cross slot structures have been investigated theoretically in the present paper. The dispersion relations, the power transmission spectra and the displacement fields of the eigenmodes are calculated by using the finite element method. Numerical results show that the proposed structures with periodic Jerusalem cross slots can yield large band gaps in the low-frequency range as compared to the typical phononic crystals composed of periodic square rods embedded in a homogenous matrix. The formation mechanisms of the large low-frequency band gaps as well as the effects of the geometrical parameters on the band gaps are further explored numerically. Results show that the openings of the low-frequency band gaps are mainly attributed to the interaction between the local resonances of the square scatterers with Jerusalem cross slot structures and the traveling wave modes in the matrix. The band gaps can be significantly modulated by changing the geometrical parameters of Jerusalem cross slot structures.</span