秸秆处理技术的最新进展:挑战与解决方案

秸秆作为一种农业副产品已被认为是一种潜在生物质资源。然而,露天焚烧秸秆仍是世界许多地区的主要手段,这造成资源浪费和空气污染。近年来已经开发了许多用于从秸秆中回收能源和资源的技术,由于其经济可行性和生态友好性质,该生物学方法引起了越来越多的研究兴趣。然而,在生物加工过程之前对秸秆进行预处理是必不可少的,并且在很大程度上决定了过程的可行性、经济可行性和环境可持续性。因此,本综述试图对当前的秸秆预处理技术和管理实践进行重要而全面的分析。主要提出了结合微生物降解和酶促水解的综合生物过程,并阐述了其与未来大规模秸秆处理相关的潜在利益、局限性和挑战,并展望了前景和方向。

Characteristics of sewer biofilms in aerobic rural small diameter gravity sewers

Small diameter gravity sewers(SDGS)are extensively used to collect rural sewage as they are low in cost and quick to construct.However,the characteristics of biofilms in rural SDGS are still not clear.In this study,biofilms characteristics of aerobic rural SDGS were investigated using simulations in a lab under different flow conditions and slopes.Results indic ated that the average thickness of aerobic rural SDGS biofilms was in the range of 350-650μm,decreasing at locations with variable flow and high slopes.Protein was the most abundant substance in extracellular polymeric substance of SDGS biofilms.The most abundant bacteria,Proteobacteria,Actinobacteria,and Bacteroidetes,and functional bacteria showed different distributions when analyzed through Illumina HiSeq sequencing of 16 S rRNA.The relative abundances of denitrifying bacteria,nitrite-oxidizing bacteria,and sulfate-reducing bacteria(SRB)were lower during variable flow than during stable flow.High slopes(15‰)decreased SRB presence,which could be used to mitigate H2 S accumulation in aerobic SDGS.Overall,this study describes the characteristics of aerobic rural SDGS biofilms and provides valuable suggestions for the optimal design of SDGS based on these characteristics.

Intrinsic physical relationships between rotor modal shapes and instantaneous vibrational energy flow transmission characteristics:Theoretical and numerical analysis and application

The modal vibration of the rotor is the main cause of excessive vibration of the aeroengine overall structure.To attenuate the vibration of the rotor under different modal shapes from the perspective of energy control,the intrinsic physical relationships between rotor modal shapes and instantaneous vibrational energy flow transmission characteristics is derived from the general equation of motion base on the structural intensity method.A dual-rotor-support-casing coupling model subjected to the rotor unbalanced forces is established by the finite element method in this paper.The transmission,conversion and balance relationships of the vibrational energy flow for the rotors in the first-order bending modal shape,the conical whirling modal shape and the translational modal shape are analyzed,respectively.The results show that the vibrational energy flow transmitted to the structure can be converted into the strain energy,the kinetic energy and the energy dissipated by the damping of the structure.The vibrational energy flow transmission characteristics of rotors with different modal shapes are quite different.Especially for the first-order bending modal shape,the vibrational energy flow and the strain energy are transmitted and converted to each other in the middle part of the rotor shaft,resulting in large deformation at this part.To attenuate this harmful vibration,the influences of grooving on the shaft on the first-order bending vibration are studied from the perspective of transmission control of vibrational energy flow.This study can provide theoretical references and guidance for the vibration attenuation of the rotors in different modal shapes from a more essential perspective.