Mixing problems are most likely encountered and sometimes can be severe in scaling-up projects. Micro-mixing is an important aspect for fast or quasi-instantaneous reactions. Poor micro-mixing might produce more undes...Mixing problems are most likely encountered and sometimes can be severe in scaling-up projects. Micro-mixing is an important aspect for fast or quasi-instantaneous reactions. Poor micro-mixing might produce more undesired by-products, leading to higher purification costs. This paper gives an extensive review and analysis of micro-mixing studies in single- and multi phase stirred tanks. The relevant experiment techniques, micro-mixing models and nurherical approaches are critically reviewed and analyzed with remarks and perspectives. The reported studies on two-phase micro-mixing experiments and on the impact of the presence of the dispersed phases on turbulence have been limited to a narrow range of conditions. More importantly, disparities widely exist among different reports. Both Lagrangian and Eulerian models are based on oversimplified assumptions, which may lead to uncertainties or even unrealistic results. A heuristic model, which is from the perspective of CFD （computational fluid dynamics） and can cover the whole spectrum of scales and also focus on every subrocess, is desired in the future.展开更多
The efficiency of advanced membranes towards removal of general and specific microbes from wastewater was investigated. The treatment included a subsequent system of activated sludge, ultrafiltration （hollow fibre me...The efficiency of advanced membranes towards removal of general and specific microbes from wastewater was investigated. The treatment included a subsequent system of activated sludge, ultrafiltration （hollow fibre membranes with 100 kDa cut-off, and spiral wound membranes with 20 kDa cut-off）, and RO （reverse osmosis）. The removal evaluation of screened microbes present in treated wastewater showed that hollow fibre membrane rejected only 1 log （90% rejection） of the TPC （total microbial count）, TC （total coliforms）, and FC （faecal coliforms）. A higher effectiveness was observed with spiral wound, removing 2-3 logs （99%-99.9%） of TPC and complete rejection of TC and FC. The RO system was successful in total rejection of all received bacteria. The removal evaluation of inoculated specific types of bacteria showed that the hollow membranes removed 2 logs （99%） of inoculated E. coli （10^7-10^8 cfu/mL inoculum）, 2-3 logs （99%-99.9%） of Enterococus spp. （10^7-10^10 cfu/mL inoculum）, 1-2 logs （90%-99%） of Salmonella （10^8-10^10 cfu/mL inoculum） and 1-2 logs （90%-99%） of Shigella （10^5-10^6 cfu/mL inoculum）. The spiral wound was significantly efficient in rejecting further 3 logs of E. coil, 5 logs of Enterococus spp., 4 logs of Salmonella, and a complete rejection of all received bacteria was accomplished by RO membrane. The results indicate that Gram positive bacteria were removed much more efficiently compared to the Gram negative ones, the rationale behind such behaviour is based on cell walls elasticity.展开更多
This paper presents the investigation of energy and cost saving of microgeneration systems which consist of conventional, load sharing, renewable energy and hybrid-renewable energy systems application featuring single...This paper presents the investigation of energy and cost saving of microgeneration systems which consist of conventional, load sharing, renewable energy and hybrid-renewable energy systems application featuring single detached house and office buildings by implementing spreadsheet modeling. Microsoft excel is employed as the spreadsheet application in this study. The system performance of each case is calculated under typical weather of ottawa, canada. These cases are calculated and analyzed in terms of thermal/cooling load （building demand） and natural gas/electricity consumption （energy supply） as well as the financial part by involving several parameters which are initial cost, annual energy consumption cost, annual operational and maintenance cost, inflation rate, and return on investment. Moreover, a house and an office have the same geometry of 200 mE. Total of seven cases modeling are developed; Case-1- a house with boiler and chiller, Case-2- an office with boiler and chiller, Case-3-a simple sum of Case l and Case 2, Case-4- a load-sharing model, Case-5- a load-sharing with GSHP （ground source heat pump）, Case-6- a load-sharing with ground source heat pump-fuel cell hybrid system （FC-GSHP）and Case-7- a load-sharing with GSHP--photovoltaic hybrid system （PVT-GSHP）. As the results, it will be observed the efficiency of the load-sharing, renewable energy, hybrid-renewable energy implementation comparing to the conventional system.展开更多
The transmission properties of hybrid quasi-periodic photonic systems （HQPS） made by the combination of one-dimensional periodic photonic crystals （PPCs） and quasi-periodic photonic crystals （QPCs） were theoreti...The transmission properties of hybrid quasi-periodic photonic systems （HQPS） made by the combination of one-dimensional periodic photonic crystals （PPCs） and quasi-periodic photonic crystals （QPCs） were theoretically studied. The hybrid quasi-periodic photonic lattice based on the hetero-structures was built from the Fibonacci and Thue-Morse sequences. We addressed the microwave properties of waves through the one-dimensional symmetric Fibonacci, and Thue-Morse system i.e., a quasi-periodic structure was made up of two different dielectric materials （Rogers and air）, in the quarter wavelength condition. It shows that controlling the Fibonacci parameters permits to obtain selective optical filters with the narrow passband and polychromatic stop band filters with varied properties which can be controlled as desired. From the results, we presented the self-similar features of the spectra, and we also presented the fractal process through a return map of the transmission coefficients. We extracted powerfully the band gaps of hybrid quasi-periodic multilayered structures, called ＂pseudo band gaps＂, often containing resonant states, which could be considered as a manifestation of numerous defects distributed along the structure. The results of transmittance spectra showed that the cutoff frequency could be manipulated through the thicknesses of the defects and the type of dielectric layers of the system. Taken together, the above two properties provide favorable conditions for the design of an all-microwave intermediate reflector.展开更多
We investigate the stability of steady states of a size- and stage-structured population model, which is a hybrid system of ordinary and partial differential equations with global integral feedbacks. After the formula...We investigate the stability of steady states of a size- and stage-structured population model, which is a hybrid system of ordinary and partial differential equations with global integral feedbacks. After the formulation of a criterion by spectrum method, we derive conditions for global stability of the trivial state and local stability of the positive equilibrium via the basic reproduction rate. Furthermore, some examples and simulations ure .presented to illustrate the obtained results.展开更多
基金Supported by the State Key Development Program for Basic Research of China (2010CB630904)the National Natural Science Fund for Distinguished Young Scholars (21025627)+2 种基金the National Natural Science Foundation of China (21106154,20990224)the National High Technology Research and Development Program of China (2011AA060704)the Beijing Natural Science Foundation (2112038) and Jiangsu Province Project (BY2009133)
文摘Mixing problems are most likely encountered and sometimes can be severe in scaling-up projects. Micro-mixing is an important aspect for fast or quasi-instantaneous reactions. Poor micro-mixing might produce more undesired by-products, leading to higher purification costs. This paper gives an extensive review and analysis of micro-mixing studies in single- and multi phase stirred tanks. The relevant experiment techniques, micro-mixing models and nurherical approaches are critically reviewed and analyzed with remarks and perspectives. The reported studies on two-phase micro-mixing experiments and on the impact of the presence of the dispersed phases on turbulence have been limited to a narrow range of conditions. More importantly, disparities widely exist among different reports. Both Lagrangian and Eulerian models are based on oversimplified assumptions, which may lead to uncertainties or even unrealistic results. A heuristic model, which is from the perspective of CFD （computational fluid dynamics） and can cover the whole spectrum of scales and also focus on every subrocess, is desired in the future.
文摘The efficiency of advanced membranes towards removal of general and specific microbes from wastewater was investigated. The treatment included a subsequent system of activated sludge, ultrafiltration （hollow fibre membranes with 100 kDa cut-off, and spiral wound membranes with 20 kDa cut-off）, and RO （reverse osmosis）. The removal evaluation of screened microbes present in treated wastewater showed that hollow fibre membrane rejected only 1 log （90% rejection） of the TPC （total microbial count）, TC （total coliforms）, and FC （faecal coliforms）. A higher effectiveness was observed with spiral wound, removing 2-3 logs （99%-99.9%） of TPC and complete rejection of TC and FC. The RO system was successful in total rejection of all received bacteria. The removal evaluation of inoculated specific types of bacteria showed that the hollow membranes removed 2 logs （99%） of inoculated E. coli （10^7-10^8 cfu/mL inoculum）, 2-3 logs （99%-99.9%） of Enterococus spp. （10^7-10^10 cfu/mL inoculum）, 1-2 logs （90%-99%） of Salmonella （10^8-10^10 cfu/mL inoculum） and 1-2 logs （90%-99%） of Shigella （10^5-10^6 cfu/mL inoculum）. The spiral wound was significantly efficient in rejecting further 3 logs of E. coil, 5 logs of Enterococus spp., 4 logs of Salmonella, and a complete rejection of all received bacteria was accomplished by RO membrane. The results indicate that Gram positive bacteria were removed much more efficiently compared to the Gram negative ones, the rationale behind such behaviour is based on cell walls elasticity.
文摘This paper presents the investigation of energy and cost saving of microgeneration systems which consist of conventional, load sharing, renewable energy and hybrid-renewable energy systems application featuring single detached house and office buildings by implementing spreadsheet modeling. Microsoft excel is employed as the spreadsheet application in this study. The system performance of each case is calculated under typical weather of ottawa, canada. These cases are calculated and analyzed in terms of thermal/cooling load （building demand） and natural gas/electricity consumption （energy supply） as well as the financial part by involving several parameters which are initial cost, annual energy consumption cost, annual operational and maintenance cost, inflation rate, and return on investment. Moreover, a house and an office have the same geometry of 200 mE. Total of seven cases modeling are developed; Case-1- a house with boiler and chiller, Case-2- an office with boiler and chiller, Case-3-a simple sum of Case l and Case 2, Case-4- a load-sharing model, Case-5- a load-sharing with GSHP （ground source heat pump）, Case-6- a load-sharing with ground source heat pump-fuel cell hybrid system （FC-GSHP）and Case-7- a load-sharing with GSHP--photovoltaic hybrid system （PVT-GSHP）. As the results, it will be observed the efficiency of the load-sharing, renewable energy, hybrid-renewable energy implementation comparing to the conventional system.
文摘The transmission properties of hybrid quasi-periodic photonic systems （HQPS） made by the combination of one-dimensional periodic photonic crystals （PPCs） and quasi-periodic photonic crystals （QPCs） were theoretically studied. The hybrid quasi-periodic photonic lattice based on the hetero-structures was built from the Fibonacci and Thue-Morse sequences. We addressed the microwave properties of waves through the one-dimensional symmetric Fibonacci, and Thue-Morse system i.e., a quasi-periodic structure was made up of two different dielectric materials （Rogers and air）, in the quarter wavelength condition. It shows that controlling the Fibonacci parameters permits to obtain selective optical filters with the narrow passband and polychromatic stop band filters with varied properties which can be controlled as desired. From the results, we presented the self-similar features of the spectra, and we also presented the fractal process through a return map of the transmission coefficients. We extracted powerfully the band gaps of hybrid quasi-periodic multilayered structures, called ＂pseudo band gaps＂, often containing resonant states, which could be considered as a manifestation of numerous defects distributed along the structure. The results of transmittance spectra showed that the cutoff frequency could be manipulated through the thicknesses of the defects and the type of dielectric layers of the system. Taken together, the above two properties provide favorable conditions for the design of an all-microwave intermediate reflector.
文摘We investigate the stability of steady states of a size- and stage-structured population model, which is a hybrid system of ordinary and partial differential equations with global integral feedbacks. After the formulation of a criterion by spectrum method, we derive conditions for global stability of the trivial state and local stability of the positive equilibrium via the basic reproduction rate. Furthermore, some examples and simulations ure .presented to illustrate the obtained results.
