Effect of Prestirring Time on Carbon Removal from Coal Fly Ash in the Flotation Technology.

Coal fly ash (CFA) is one of the industrial byproducts of burning coal for energy production and has unburned carbon, which negatively affects its full potential use. The flotation technology can be effective in separating unburned carbon from CFA, and the prestirring time is crucial for the ideal initial conditions during the flotation process. To find the suitable prestirring time, eight prestirring times, including 0, 1, 2, 3, 4, 5, 6, and 7 min, were selected in this paper, followed by flotation of CFA after prestirring.

Low-temperature synthesis of colloidal few-layer WTe nanostructures for electrochemical hydrogen evolution.

High-quality transition metal tellurides, especially for WTe, have been demonstrated to be necessarily synthesized under close environments and high temperatures, which are restricted by the low formation Gibbs free energy, thus limiting the electrochemical reaction mechanism and application studies. Here, we report a low-temperature colloidal synthesis of few-layer WTe nanostructures with lateral sizes around hundreds of nanometers, which could be tuned the aggregation state to obtain the nanoflowers or nanosheets by using different surfactant agents. The crystal phase and chemical composition of WTe nanostructures were analyzed by combining the characterization of X-ray diffraction and high-resolution transmission electron microscopy imaging and elements mapping.

Polarization-multiplexed full-space metasurface simultaneously merging with an ultrawide-angle antireflection and a large-angle retroreflection.

Multifunctional electromagnetic (EM) metasurfaces are capable of manipulating electromagnetic waves with kaleidoscopic functions flexibly, which will significantly enhance integration and applications of electronic systems. However, most known design schemes only realize the reflection or transmission functions under a specific angle range, which wastes the other half EM space and restricts wider applications of multifunctional metadevices. Herein, an encouraging strategy of broadband and wide-angle EM wavefronts generator is proposed to produce two independent functions, i.

Tailoring permittivity using metasurface: a facile way of enhancing extreme-angle transmissions for both TE- and TM-polarizations.

The transmission of electromagnetic (EM) waves through a dielectric plate will be decreased significantly when the incident angle becomes extremely large, regardless of transverse electric (TE)- or transverse magnetic (TM)- polarization. In this regard, we propose a facile way of tailoring the permittivity of the dielectric material using metasurface to enhance the transmissions of both TE- and TM-polarized waves under extremely large incidence angles. Due to parallel or antiparallel electric fields induced by the metasurface, the net electric susceptibility is altered, and hence the effective permittivity can be tailored to improve the impedance matching on the two air-dielectric interfaces, which enhances the wave transmissions significantly under extreme incident angles.

Extremely angle-stable transparent window for TE-polarized waves empowered by anisotropic metasurfaces.

Impedance mismatch generally exists upon interfaces between different media. This is especially true for TE-polarized waves with large incident angles since there is no Brewster effect. As a result, high-efficiency transmission can only be guaranteed within limited incident angle range.

Transmission enhancement of a half-wave wall under extreme angles by synergy of double lorentz resonances.

The a half-wave wall is usually adopted as the transparent window for electromagnetic (EM) waves ranging from microwave to optical regimes. Due to the interference nature, the bandwidth of the half-wave wall is usually quite narrow, especially under extreme angles for TE-polarized waves. It is usually contradictory to expand the bandwidth and to keep high transmission.

Quasi-omnidirectional retroreflective metagrating for TE-polarized waves based on wave-vector reversions.

Structuring elements of gratings brings more freedom in manipulating diffraction waves, e.g., retroreflection using diffraction orders other than the 0 order.

Multifunctional full-space metasurface controlled by frequency, polarization and incidence angle.

Multifunctional metasurfaces have exhibited considerable abilities of manipulating electromagnetic (EM) waves, especially in full-space manipulation. However, most works are implemented with functions controlled by polarization or frequency and seldom involve the incidence angle. Herein, we propose a multifunctional full-space metasurface controlled by frequency, polarization and incidence angle.

The Impact of COVID-19 on Tourist Satisfaction with B&B in Zhejiang, China: An Importance-Performance Analysis.

After the outbreak of COVID-19 (especially in the stage of tourism recovery), the bed and breakfast (B&B) tourism industry faced big challenges in improving its health strategies. B&Bs are very important for the tourism industry in China and many other countries. However, few studies have studied the impact of B&Bs, under COVID-19, on tourism in China.

Comparison of sludge treatment by O3 and O3/H2O2.

This work focuses on the comparison of sludge decomposition caused by ozone (O3) alone and by ozone/hydrogen peroxide (O3/H2O2). The content of carbonaceous organic materials, nitrogenous compounds and phosphoric substances in sludge supernatant were measured. The release of soluble chemical oxygen demand, total nitrogen (TN) and total phosphorus (TP) caused by O3/H2O2 treatment were more than by O3 alone.