Global Distribution of Water Vapor and Cloud Cover--Sites for High Performance THz Applications

Absorption of terahertz radiation by atmospheric water vapor is a serious impediment for radio astronomy and for long-distance communications. Transmission in the THz regime is dependent almost exclusively on atmospheric precipitable water vapor (PWV). Though much of the Earth has PWV that is too high for good transmission above 200 GHz, there are a number of dry sites with very low attenuation. We performed a global analysis of PWV with high-resolution measurements from the Moderate Resolution Imaging Spectrometer (MODIS) on two NASA Earth Observing System (EOS) satellites over the year of 2011. We determined PWV and cloud cover distributions and then developed a model to find transmission and atmospheric radiance as well as necessary integration times in the various windows. We produced global maps over the common THz windows for astronomical and satellite communications scenarios. Notably, we show that up through 1 THz, systems could be built in excellent sites of Chile, Greenland and the Tibetan Plateau, while Antarctic performance is good to 1.6 THz. For a ground-to-space communication link up through 847 GHz, we found several sites in the Continental United States where mean atmospheric attenuation is less than 40 dB; not an insurmountable challenge for a link.Comment: 15 pages, 23 figure

Anisotropic Optic Conductivities due to Spin and Orbital Orderings in LaVO3 and YVO3: First-Principles Studies

The anisotropy of low energy (0$\sim$5eV) optical excitations in strongly correlated transition-metal oxides is closely related to the spin and orbital orderings. The recent successes of LDA+$U$ method in describing the magnetic and electronic structures enable us to calculate the optical conductivity from first-principles. The LaVO$_3$ and YVO$_3$, both of which have $3d^2$ configuration and have various spin and orbital ordered phases at low temperature, show distinct anisotropy in the optical spectra. The effects of spin and orbital ordering on the anisotropy are studied in detail based on our first-principles calculations. The experimental spectra of both compounds at low temperature phases can be qualitatively explained with our calculations, while the studies for the intermediate temperature phase of YVO$_3$ suggest the substantial persistence of the low temperature phase at elevated temperature.Comment: 6 pages, 3 figures, accepted by PR

Recent studies on thermophilic anaerobic bioconversion of lignocellulosic biomass

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Health Building Information Modeling (HBIM)-based Facility Management: A Conceptual Framework

The outbreak of the COVID-19 epidemic has brought significant challenges to building operation and occupant health. In practice, building operators have begun to use various Internet of Things (IoT) technologies, intelligent sensing devices, and manual registration methods to update occupant information and behaviour in different building areas. Building spaces are classified according to their health, such as the distinction between safe areas and infected areas. Using the health data of occupants and spaces to help buildings operate efficiently and safely is a problem that needs to be solved urgently. This research proposed a conceptual framework for facility management driven by a Health Building Information Model (HBIM). The framework aims to incorporate the emerging data types to enrich the health information of the BIM model and provide decision support for facility operation and maintenance

Effects of season and waterbody on transparency tube estimates of suspended sediment in large rivers

This paper reports the measurement (N>132) of the effect of river and season on transparency in cm and Total Suspended Solids in mg/L in a navigational pool of the Ohio River and one of its tributaries, the Muskingum River. Both river of origin and season affected water transparency. The transparency-TSS relationship was stronger in spring (R2 = 0.894) than autumn (R2 =0.710), with an overall correlation of R2=0.86 for N=93 observations in both water bodies and seasons. Regression equations for the transparency-TSS relationships for the two rivers under low (autumn) and high (spring) flow conditions were developed. Our study demonstrates that properly trained volunteers can assist with rapid assessment of water turbidity from suspended solids in large rivers, reservoirs and lakes, but seasonal calibration of these measures will improve accuracy of sediment monitoring and management.Keywords: Transparency tube, turbidity, monitoring, sediment transport, citizen science, water qualit

Impact of turbulence and secondary flow on the water surface in partially filled pipes

Large eddy simulations (LESs) of turbulent flow in partially filled pipes at various filling degrees are conducted to investigate the response of the water surface to the turbulence and the secondary flow below it. LESs are validated first using experimental and direct numerical simulation data. At increasing water depth, the magnitude of water surface fluctuations increases with increasing strength of the main secondary flow. Visualizations of the instantaneous water surface and the turbulent flow underneath reveal that thin surface waves are generated by flow meandering in the shallower case, whereas surface waves in the deeper cases are influenced by the vertical velocity fluctuation. Pre-multiplied spectra of the water surface fluctuation, h′, provide further evidence of the origin of the surface waves. In the shallow flow, the peak frequency of the h′ spectra is consistent with the peak frequency of the u′ and v′ spectra, while for deeper flows, it agrees more with the w′ spectra. Furthermore, the transport patterns of the surface waves are investigated by the wavenumber-frequency spectra. Three types of surface waves are observed in the wavenumber-frequency spectra, i.e., (1) convective waves with phase velocity equaling the surface velocity, (2) irrotational dispersive gravity-capillary waves, and (3) stationary waves caused by secondary currents