Showing papers by "Zhen Gao published in 2014"

Topological Acoustics

Abstract: The manipulation of acoustic wave propagation in fluids has numerous applications, including some in everyday life Acoustic technologies frequently develop in tandem with optics, using shared concepts such as waveguiding and metamedia It is thus noteworthy that an entirely novel class of electromagnetic waves, known as topological edge states, has recently been demonstrated These are inspired by the electronic edge states occurring in topological insulators, and possess a striking and technologically promising property: the ability to travel in a single direction along a surface without backscattering, regardless of the existence of defects or disorder Here, we develop an analogous theory of topological fluid acoustics, and propose a scheme for realizing topological edge states in an acoustic structure containing circulating fluids The phenomenon of disorder-free one-way sound propagation, which does not occur in ordinary acoustic devices, may have novel applications for acoustic isolators, modulators, and transducers

Terahertz transparency of optically opaque metallic films

Abstract: Here we present an alternative approach to design a freestanding transparent conducting device for wide-angle and polarization-insensitive incidence of electromagnetic waves at terahertz frequencies. It is realized by depositing periodic metallic patches on top and bottom of the subwavelength metallic mesh. Based on the numerical computations, the deposited metallic patches can suppress the reflection and enhance the transmission. The high transmission of the designed system is attributed to the impedance matching to the vacuum. This design of a transparent conducting device can be useful in applications, such as optoelectronic electrodes and micro-electronic displays, where both high electrical conductivity and high optical transmittance are desirable.

Terahertz spoof plasmonic coaxial microcavity.

Abstract: We theoretically demonstrate a subwavelength spoof surface-plasmon–polariton (SPP) microcavity on a planar metallic surface working at the terahertz regime with a high-quality factor and ultra-small mode volume. The microcavity is based on plasmonic and metamaterial notions, and it consists of an easy-to-manufacture circular aperture and a bell-shaped metallic core. It is shown that such a structure can sustain SPP eigenmodes whose fields are tightly trapped within the microcavity. Using the proposed structure, a total Q factor of 1000 (including losses from metals at low temperatures) and subwavelength mode volume of 0.00018(λ/2)3 can be achieved in the THz range for the fundamental surface-plasmonic eigenmode at room temperature. Moreover, the key figures of merit such as resonance frequency can be flexibly tuned by modifying the geometry of the microcavity, making it attractive for broad applications in filters, light sources, energy storage, and on-chip optical communications.

Microbial oil preparation method with biodiesel byproducts as carbon sources

Abstract: The invention provides a microbial oil preparation method with biodiesel byproducts as carbon sources and belongs to the technical field of microbial oil preparation. According to the microbial oil preparation method, microbial oil is prepared with the biodiesel byproducts serving as the carbon sources and rhodotorula glutinis 32489 serving as the oil-producing microorganisms. Therefore, the problem of high cost when glucose or pure glycerine (AR) is used as the carbon sources to prepare microbial oil is solved, and crude glycerine is effectively used; the components of the produced microbial oil are almost as same as those of vegetable oil. Compared with vegetable oil, microbial oil has the advantages of being short in the preparation cycle and free of occupying arable land, is a cheap non-crop biomass raw material to prepare biodiesel, can reduce the preparation cost of biodiesel, and has a wide application prospect.

Novel method for preparing biodiesel under catalysis of modified resin

Abstract: The invention provides a novel method for preparing biodiesel under catalysis of modified resin, belonging to the technical field of biodiesel synthesis and environment-friendly recyclable energy resources. According to the method, ferric iron modified 732 Na-type strongly acidic styrene cationic exchange resin is adopted as a catalyst for catalyzing ester exchange reaction of waste cooking oil and methanol to prepare the biodiesel, so that the problem of strict requirement on the acid value of the waste oil due to alkali as the catalyst is avoided, the deacidification pretreatment step required for preventing saponification reaction is omitted, and the shortcomings of long reaction time, high temperature, a large quantity of byproducts, serious equipment corrosion, a large quantity of acidic wastewater, environmental pollution and the like due to sulfuric acid as the catalyst are overcome; the catalyst has the advantages of low price, high catalytic activity and the like and is simple to prepare and recyclable, and the product is easily separated out, the problems of difficult preparation, high expense and instable catalytic activity of a general heterogeneous catalyst are solved, and the method for preparing the biodiesel has good prospects.