Optimization of composition and microstructure is important to enhance performance of solid oxide fuel cells (SOFC) and lithium-ion batteries (LIB). For this, the porous electrode structures of both SOFC and LIB a...Optimization of composition and microstructure is important to enhance performance of solid oxide fuel cells (SOFC) and lithium-ion batteries (LIB). For this, the porous electrode structures of both SOFC and LIB are modeled as a binary mixture of electronic and ionic conducting particles to estimate effective transport properties. Particle packings of 10000 spherical, binary sized and randomly positioned particles are created numerically and densified considering the different manufacturing processes in SOFC and LIB: the sintering of SOFC electrodes is approximated geometrically, whereas the calendering process and volume change due to intercalation in LIB are modeled physically by a discrete el- ement approach. A combination of a tracking algorithm and a resistor network approach is developed to predict the con- nectivity and effective conductivity for the various densified structures. For SOFC, a systematic study of the influence of morphology on connectivity and conductivity is performed on a large number of assemblies with different compositions and particle size ratios between 1 and 10. In comparison to percolation theory, an enlarged percolation area is found, es- pecially for large size ratios. It is shown that in contrast to former studies the percolation threshold correlates to varying coordination numbers. The effective conductivity shows not only an increase with volume fraction as expected but also with size ratio. For LIB, a general increase of conductivity during the intercalation process was observed in correlation with increasing contact forces. The positive influence of cal- endering on the percolation threshold and the effective conductivity of carbon black is shown. The anisotropy caused by the calendering process does not influence the carbon black phase.展开更多
In granular computing granular structures represent knowledge on universe,in this paper several important granular structures are considered.In a general granular structure the notions of interior point, accumulation ...In granular computing granular structures represent knowledge on universe,in this paper several important granular structures are considered.In a general granular structure the notions of interior point, accumulation point and boundary point etc are proposed,by use of these notions and referring to topological method,the lower and upper approximations of a subset of universe are defined such that they are one kind of generalization of the existing approximations based on some special granular structure.Basic properties of new rough set approximations are investigated.Furthermore,granular structures on universe are characterized by the lower and upper approximation operators.展开更多
Aerobic sludge granulation was rapidly obtained in the erlenmeyer bottle and sequencing batch reactor(SBR) using piggery wastewater.Aerobic granulation occurred on day 3 and granules with mean diameter of 0.2 mm and...Aerobic sludge granulation was rapidly obtained in the erlenmeyer bottle and sequencing batch reactor(SBR) using piggery wastewater.Aerobic granulation occurred on day 3 and granules with mean diameter of 0.2 mm and SVI_(30) of 20.3 mL/g formed in SBR on day 18.High concentrations of Ca and Fe in the raw piggery wastewater and operating mode accelerated aerobic granulation,even though the seed sludge was from a municipal wastewater treatment plant(WWTP).Alpha diversity analysis revealed Operational Taxonomic Units,Shannon,ACE and Chao 1 indexes in aerobic granules were 2013,5.51,4665.5 and 3734.5,which were obviously lower compared to seed sludge.The percentages of major microbial communities,such as Protect)acteria,Bacteroidetes and Firmicutes were obviously higher in aerobic granules than seed sludge.Chlorqflexi,Planctomycetes,Actinobactena,TM7 and Aridobacteria showed much higher abundances in the inoculum.The main reasons might be the characteristics of raw piggery wastewater and granule structure.展开更多
The role of number of grain size fractions on structural and mechanical properties of uniaxially com- pressed granular packings with a uniform particle size distribution in terms of number of particles and with variou...The role of number of grain size fractions on structural and mechanical properties of uniaxially com- pressed granular packings with a uniform particle size distribution in terms of number of particles and with various particle size dispersities was studied using the discrete element method. The study addressed packing density, coordination number, contact forces, global stress, and energy dissipation in assemblies composed of frictional spheres. Packing density was found to change with increasing num- ber of granulometric fractions in mixtures with a small ratio of the diameters of the largest to smallest particles. Results indicated a certain value of particle size ratio below which the number of particle size fractions strongly affected packing density. The average coordination number decreased with increasing number of fractions. Detailed analysis of the effect of particle size dispersity on mechanical coordination number, including particles with no less than four contacts, revealed that, contrary to the average coordi- nation number, the mechanical coordination number increased with increasing ratio of the diameters of the largest to smallest particles in the sample. The composition of polydisperse samples strongly affected stress distribution and energy dissipation in granular packings.展开更多
基金supported by the Helmholtz Portfolio "elektrochemische Speicher",particularly the work related to lithium-ion batteriespartially supported as part of the HeteroFoam Center,an Energy Frontier Research Center funded by the U.S.Department of Energy,Office of Science, Basic Energy Sciences(DE-SC0001061)+1 种基金support from the Center for Scientific Computing at the CNSI and MRL:an NSF MRSEC(DMR-1121053) and NSF (CNS-0960316)Australian Research Council Grant DE130101639
文摘Optimization of composition and microstructure is important to enhance performance of solid oxide fuel cells (SOFC) and lithium-ion batteries (LIB). For this, the porous electrode structures of both SOFC and LIB are modeled as a binary mixture of electronic and ionic conducting particles to estimate effective transport properties. Particle packings of 10000 spherical, binary sized and randomly positioned particles are created numerically and densified considering the different manufacturing processes in SOFC and LIB: the sintering of SOFC electrodes is approximated geometrically, whereas the calendering process and volume change due to intercalation in LIB are modeled physically by a discrete el- ement approach. A combination of a tracking algorithm and a resistor network approach is developed to predict the con- nectivity and effective conductivity for the various densified structures. For SOFC, a systematic study of the influence of morphology on connectivity and conductivity is performed on a large number of assemblies with different compositions and particle size ratios between 1 and 10. In comparison to percolation theory, an enlarged percolation area is found, es- pecially for large size ratios. It is shown that in contrast to former studies the percolation threshold correlates to varying coordination numbers. The effective conductivity shows not only an increase with volume fraction as expected but also with size ratio. For LIB, a general increase of conductivity during the intercalation process was observed in correlation with increasing contact forces. The positive influence of cal- endering on the percolation threshold and the effective conductivity of carbon black is shown. The anisotropy caused by the calendering process does not influence the carbon black phase.
基金supported by grants from the National Natural Science Foundation of China(Nos.11071284 and 61075120)the Natural Science Foundation of Zhejiang Province in China(No.Y107262).
文摘In granular computing granular structures represent knowledge on universe,in this paper several important granular structures are considered.In a general granular structure the notions of interior point, accumulation point and boundary point etc are proposed,by use of these notions and referring to topological method,the lower and upper approximations of a subset of universe are defined such that they are one kind of generalization of the existing approximations based on some special granular structure.Basic properties of new rough set approximations are investigated.Furthermore,granular structures on universe are characterized by the lower and upper approximation operators.
基金supported by the National Nature Science Foundation of China(No.51478433)
文摘Aerobic sludge granulation was rapidly obtained in the erlenmeyer bottle and sequencing batch reactor(SBR) using piggery wastewater.Aerobic granulation occurred on day 3 and granules with mean diameter of 0.2 mm and SVI_(30) of 20.3 mL/g formed in SBR on day 18.High concentrations of Ca and Fe in the raw piggery wastewater and operating mode accelerated aerobic granulation,even though the seed sludge was from a municipal wastewater treatment plant(WWTP).Alpha diversity analysis revealed Operational Taxonomic Units,Shannon,ACE and Chao 1 indexes in aerobic granules were 2013,5.51,4665.5 and 3734.5,which were obviously lower compared to seed sludge.The percentages of major microbial communities,such as Protect)acteria,Bacteroidetes and Firmicutes were obviously higher in aerobic granules than seed sludge.Chlorqflexi,Planctomycetes,Actinobactena,TM7 and Aridobacteria showed much higher abundances in the inoculum.The main reasons might be the characteristics of raw piggery wastewater and granule structure.
文摘The role of number of grain size fractions on structural and mechanical properties of uniaxially com- pressed granular packings with a uniform particle size distribution in terms of number of particles and with various particle size dispersities was studied using the discrete element method. The study addressed packing density, coordination number, contact forces, global stress, and energy dissipation in assemblies composed of frictional spheres. Packing density was found to change with increasing num- ber of granulometric fractions in mixtures with a small ratio of the diameters of the largest to smallest particles. Results indicated a certain value of particle size ratio below which the number of particle size fractions strongly affected packing density. The average coordination number decreased with increasing number of fractions. Detailed analysis of the effect of particle size dispersity on mechanical coordination number, including particles with no less than four contacts, revealed that, contrary to the average coordi- nation number, the mechanical coordination number increased with increasing ratio of the diameters of the largest to smallest particles in the sample. The composition of polydisperse samples strongly affected stress distribution and energy dissipation in granular packings.