Metasurfaces with spin‐selective reflection or transmission functions for circularly‐polarized (CP) incident waves have aroused researchers' great attention. However, current spin‐selective metasurface designs have yet to mature into a practical method due to the limitations of single operating band or inefficient phase modulation. Herein, a novel chiral meta‐atom is proposed, exhibiting spin‐selective absorption/reflection functions for dual‐orthogonal CP incident waves at three different operating bands. More significantly, the Pancharatnam–Berry phase theory is introduced at all working frequencies to generate a full 2π reflection phase modulation by rotating the chiral resonator, and the three distinct absorption bands remain almost constant with the rotation. Theoretical results indicate that high absorption can separately act on left‐handed or right‐handed CP incident waves at triple bands, and meanwhile, the other incident wave with different handedness is efficiently reflected without changing the handedness. As a proof of concept, two tri‐band meta‐devices with spin‐selective anomalous reflection and spin‐selective orbital angular momentum generating functions are designed and experimentally characterized, both of which exhibit excellent spin‐dependent bi‐functional performances at three different operating bands. The research results provide a promising route to realize spin‐selective meta‐devices with multi‐band operating modes in wireless communication systems and multispectral imaging and information encryption fields.
Isolation and culture of hydrogen-producing and fermentative bacteria is an important foundation on biohydrogen production process. There are complicated operation and composition in present anaerobic techniques and culture media. Hungate technique was improved and plate of culture bottle was established by comparing anaerobic methods and bacterium growth. Isolation and enrichment culture media were confirmed by the test of different composition and the species and amount of hydrogen-producing and fermentative bacterium. 550 bacterium strains were isolated by the anaerobic operation.
Substrate concentration effects on H2 production performance in a continuous stirred-tank reactor (CSTR) were investigated. Using molasses as the feeding, the CSTR system was operated at chemical oxygen demand (COD) of 2000-8000 mg/L to identify the optimal working substrate concentration. Increasing substrate concentration (2000~6000 mg/L) gave better biomass content and hydrogen production, signifying that the average cellular activity for H2 production may be enhanced as the substrate concentration increased. The overall maximal biogas and hydrogen production yield were 18.69 L and 6.01 L, respectively, both of them occurred at 6000 mg/L. The gas phase H2 content did not vary considerably regardless of changes in substrate concentration. This reflects that the CSTR was a relatively stable H2-producing system. The major soluble products from hydrogen fermentation were ethanol and acetic acid, accounting for 59% and 23% of total liquid fermentation products, respectively. Thus, the dominant H2 producers in the mixed culture belonged to acidogenic bacteria that underwent ethanol-type fermentation. However, the biomass content and hydrogen production yield tended to decrease as the substrate concentration increased to 8000 mg/L, suggesting that granular sludge formation and cellular activity for H2 production may be inhibited at high substrate concentration. Ethanol, acetic, butyric and propionic were the main liquid fermentation products with the percentages of 31%, 24%, 20% and 18%, which formed the mixed-type fermentation.
The important premise for hydrogen production technology of fermentation generator was to separate and identify the efficient hydrogen producing bacteria. By use of Hungater technology and flat-panel technology with wide-body narrow-neck flask, LM-1 and HPB-LR medium to separate and identify the anaerobic fermentation hydrogen production bacteria, and five hydrogen-producing bacteria were obtained, whose hydrogen metabolism was ethanol fermentation. The product analysis on the hydrogen production bacteria fermentation liquid showed that ethanol and acetic acid accounted for 95%-99% of the total metabolites. These strains can be fermented to produce hydrogen, and can be used for industrial applications.
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