Beihang University

About: Beihang University is a education organization based out in Beijing, China. It is known for research contribution in the topics: Computer science & Control theory. The organization has 67002 authors who have published 73507 publications receiving 975691 citations. The organization is also known as: Beijing University of Aeronautics and Astronautics.

Power generation and thermoelectric cooling enabled by momentum and energy multiband alignments.

Abstract: Thermoelectric materials transfer heat and electrical energy, being useful for power generation or cooling applications. Many of these materials have narrow bandgaps, especially for cooling applications where this property has been seen as particularly important for enhancing the thermoelectric properties. We developed SnSe crystals with a wide bandgap Eg ~ 33 kBT with attractive thermoelectric properties through Pb alloying. The momentum and energy multiband alignment promoted by Pb alloying resulted in an ultra-high power factor ~75 μWcm–1K–2 at 300 K, and a ZTave ~ 1.90. We show that a 31-pair thermoelectric device can produce a power generation efficiency ~4.4% and a cooling ΔTmax ~ 45.7 K. These results demonstrate that wide bandgap compounds can be used for thermoelectric cooling applications.

Scheduling in cloud manufacturing: state-of-the-art and research challenges

Abstract: For the past eight years, cloud manufacturing as a new manufacturing paradigm has attracted a large amount of research interest worldwide. The aim of cloud manufacturing is to deliver on-demand man ...

Underwater superoleophobic porous membrane based on hierarchical TiO2 nanotubes: multifunctional integration of oil–water separation, flow-through photocatalysis and self-cleaning

Abstract: Functional porous membranes with special surface wettability have been applied widely for the treatment of water contamination. Herein, we demonstrated a novel underwater superoleophobic porous membrane with multifunctions such as oil–water separation, flow-through photocatalysis and self-cleaning. The porous membrane was fabricated by electrochemical formation of hierarchical TiO2 nanotubes on the surface of porous titanium, followed by calcination in air. Due to its superhydrophilicity and underwater superoleophobicity, the porous membrane achieved the separation of oily substances from water by allowing water to permeate through the membrane. The photocatalysis of hierarchical TiO2 nanotubes in the porous membrane was used to decompose toxic organic molecules during the permeation of polluted water through the membrane. In some cases, when the porous membrane was contaminated by organic molecules in the environment and lost their unique surface wettability, the UV-induced self-cleaning function of hierarchical TiO2 nanotubes recovered its original wettability. This multifunctional porous membrane demonstrated potential application against water contamination.

Lift and power requirements of hovering flight in Drosophila virilis.

Abstract: SUMMARY The lift and power requirements for hovering flight in Drosophila virilis were studied using the method of computational fluid dynamics. The Navier-Stokes equations were solved numerically. The solution provided the flow velocity and pressure fields, from which the unsteady aerodynamic forces and moments were obtained. The inertial torques due to the acceleration of the wing mass were computed analytically. On the basis of the aerodynamic forces and moments and the inertial torques, the lift and power requirements for hovering flight were obtained. For the fruit fly Drosophila virilis in hovering flight (with symmetrical rotation), a midstroke angle of attack of approximately 37° was needed for the mean lift to balance the insect weight, which agreed with observations. The mean drag on the wings over an up- or downstroke was approximately 1.27 times the mean lift or insect weight (i.e. the wings of this tiny insect must overcome a drag that is approximately 27 % larger than its weight to produce a lift equal to its weight). The body-mass-specific power was 28.7 W kg-1, the muscle-mass-specific power was 95.7 W kg-1 and the muscle efficiency was 17 %. With advanced rotation, larger lift was produced than with symmetrical rotation, but it was more energy-demanding, i.e. the power required per unit lift was much larger. With delayed rotation, much less lift was produced than with symmetrical rotation at almost the same power expenditure; again, the power required per unit lift was much larger. On the basis of the calculated results for power expenditure, symmetrical rotation should be used for balanced, long-duration flight and advanced rotation and delayed rotation should be used for flight control and manoeuvring. This agrees with observations.