The microstructure, microhardness and quasi-static failure behavior of resistance spot welds of AA6111-T4 aluminum alloy were experimentally investigated. Optical metallography and high-resolution hardness traverses w...The microstructure, microhardness and quasi-static failure behavior of resistance spot welds of AA6111-T4 aluminum alloy were experimentally investigated. Optical metallography and high-resolution hardness traverses were utilized to characterize the weld nugget, heat affected zone and base metal. The AA6111 spot welds displayed a softer nugget and hardened heat affected zone, compared with the base metal. The through-thickness hardness of the base metal sheet was not constant and had to be carefully considered to determine the effect of welding on material properties. Quasi-static lap-shear tensile tests were used to determine the failure load and failure mode. All tensile specimens failed through the interfacial fracture. This failure mode is consistent with the observed reduced hardness in the weld nugget.展开更多
As the polyurethane foam(PUF)market,especially in the automotive sector,continues to grow,the environmental impacts of its petrochemical demands and end-of-life waste have motivated the industry to look for more susta...As the polyurethane foam(PUF)market,especially in the automotive sector,continues to grow,the environmental impacts of its petrochemical demands and end-of-life waste have motivated the industry to look for more sustainable solutions.This study explores the preparation of recyclable PUFs using commercially available soy polyols(Cargill's BiOH),aiming to enable improved thermal reprocessability of flexible PUFs via vitrimer chemistry.A series of“soy-PUFs”was produced by partially substituting petrochemical polyether polyols with 25%or 50%soy polyols in a standard reference formulation.Incorporation of soy polyols resulted in an increase in the stiffness of the resulting foams.Employing a modest amount(∼0.5 wt%)of dibutyltin dilaurate(DBTDL)in the formulations facilitated dynamic covalent bond exchanges in the cross-linked network during a mild“foam-to-sheet”reprocessing process(160°C),converting malleable PUFs into densified sheet materials(PUS)with proper compactness and mechanical performance(e.g.,tensile modulus=∼50 MPa).Soy-PUFs demonstrated a modestly enhanced stress relaxation behavior,suggesting adequate reprocessing ability.DMA results demonstrated the phenomenon of forming an“intermediate”region between the hard and soft domains of PUSs after reprocessing.展开更多
With the development of artificial intelligence and breakthroughs in deep learning,large-scale foundation models(FMs),such as generative pre-trained transformer(GPT),Sora,etc.,have achieved remarkable results in many ...With the development of artificial intelligence and breakthroughs in deep learning,large-scale foundation models(FMs),such as generative pre-trained transformer(GPT),Sora,etc.,have achieved remarkable results in many fields including natural language processing and computer vision.The application of FMs in autonomous driving holds considerable promise.For example,they can contribute to enhancing scene understanding and reasoning.By pre-training on rich linguistic and visual data,FMs can understand and interpret various elements in a driving scene,and provide cognitive reasoning to give linguistic and action instructions for driving decisions and planning.Furthermore,FMs can augment data based on the understanding of driving scenarios to provide feasible scenes of those rare occurrences in the long tail distribution that are unlikely to be encountered during routine driving and data collection.The enhancement can subsequently lead to improvement in the accuracy and reliability of autonomous driving systems.Another testament to the potential of FMs'applications lies in world models,exemplified by the DREAMER series,which showcases the ability to comprehend physical laws and dynamics.Learning from massive data under the paradigm of self-supervised learning,world models can generate unseen yet plausible driving environments,facilitating the enhancement in the prediction of road users'behaviors and the off-line training of driving strategies.In this paper,we synthesize the applications and future trends of FMs in autonomous driving.By utilizing the powerful capabilities of FMs,we strive to tackle the potential issues stemming from the long-tail distribution in autonomous driving,consequently advancing overall safety in this domain.展开更多
In this study, a boron-doped microporous carbon （BMC）/sulfur nanocomposite is synthesized and applied as a novel cathode material for advanced Li-S batteries. The cell with this cathode exhibits an ultrahigh cycling...In this study, a boron-doped microporous carbon （BMC）/sulfur nanocomposite is synthesized and applied as a novel cathode material for advanced Li-S batteries. The cell with this cathode exhibits an ultrahigh cycling stability and rate capability. After activation, a capacity of 749.5 mAh/g was obtained on the 54t＂ cycle at a discharge current of 3.2 A/g. After 500 cycles, capacity of 561.8 mAh/g remained （74.96% retention）, with only a very small average capacity decay of 0.056%. The excellent reversibility and stability of the novel sulfur cathode can be attributed to the ability of the boron-doped microporous carbon host to both physically confine polysulfides and chemically bind these species on the host surface. Theoretical calculations confirm that boron-doped carbon is capable of significantly stronger interactions with the polysulfide species than undoped carbon, most likely as a result of the lower electronegativity of boron. We believe that this doping strategy can be extended to other metal-air batteries and fuel cells, and that it has promising potential for many different applications.展开更多
The Beijing-Tianjin-Hebei （BTH） region is one of the most heavily polluted regions in China, with both high PM2.5 concentrations and a high population density. A quantitative source-receptor relationship can provide...The Beijing-Tianjin-Hebei （BTH） region is one of the most heavily polluted regions in China, with both high PM2.5 concentrations and a high population density. A quantitative source-receptor relationship can provide valuable insights that can inform effective emission control strategies. Both source appor- tionment （SA） and source sensitivity （SS） can provide such information from different perspectives. In this study, both methods are applied in northern China to identify the most significant emission cate- gories and source regions for PMz5 exposure in BTH in 2013. Despite their differences, both models show similar distribution patterns for population and simulated PM2.5 concentrations, resulting in overall high PM2.5 exposure values （approximately 110 Ixg/m3） and particularly high exposure values during the win- ter （approximately 200 ktg/m3）. Both methods show that local emissions play a dominant role （70%）, with some contribution from surrounding provinces （e.g., Shandong） via regional transport. The two methods also agree on the priority of local emission controls： both identify industrial, residential, and agricultural emissions as the top three categories that should be controlled locally. In addition, the effect of control- ling agricultural ammonia emissions is approximately doubled when the co-benefits of reducing nitrate are considered. The synthesis of SA and SS for addressing specific categories of emissions provides a quantitative basis for the development of emission control strategies and policies for controlling PM2.5 in China.展开更多
基金Project(0211005303101)supported by the Fundamental Research Funds for the Central Universities,ChinaInternational Cooperation Project(2014DFA51270)supported by Ministry of Science and Technology of ChinaProject(2009-5043R)supported by the Ford Motor Company University Research Program,USA
文摘The microstructure, microhardness and quasi-static failure behavior of resistance spot welds of AA6111-T4 aluminum alloy were experimentally investigated. Optical metallography and high-resolution hardness traverses were utilized to characterize the weld nugget, heat affected zone and base metal. The AA6111 spot welds displayed a softer nugget and hardened heat affected zone, compared with the base metal. The through-thickness hardness of the base metal sheet was not constant and had to be carefully considered to determine the effect of welding on material properties. Quasi-static lap-shear tensile tests were used to determine the failure load and failure mode. All tensile specimens failed through the interfacial fracture. This failure mode is consistent with the observed reduced hardness in the weld nugget.
基金the financial support from the United Soybean Board,Project No.2333-102-0201 and 2422-106-010.
文摘As the polyurethane foam(PUF)market,especially in the automotive sector,continues to grow,the environmental impacts of its petrochemical demands and end-of-life waste have motivated the industry to look for more sustainable solutions.This study explores the preparation of recyclable PUFs using commercially available soy polyols(Cargill's BiOH),aiming to enable improved thermal reprocessability of flexible PUFs via vitrimer chemistry.A series of“soy-PUFs”was produced by partially substituting petrochemical polyether polyols with 25%or 50%soy polyols in a standard reference formulation.Incorporation of soy polyols resulted in an increase in the stiffness of the resulting foams.Employing a modest amount(∼0.5 wt%)of dibutyltin dilaurate(DBTDL)in the formulations facilitated dynamic covalent bond exchanges in the cross-linked network during a mild“foam-to-sheet”reprocessing process(160°C),converting malleable PUFs into densified sheet materials(PUS)with proper compactness and mechanical performance(e.g.,tensile modulus=∼50 MPa).Soy-PUFs demonstrated a modestly enhanced stress relaxation behavior,suggesting adequate reprocessing ability.DMA results demonstrated the phenomenon of forming an“intermediate”region between the hard and soft domains of PUSs after reprocessing.
基金supported in part by the National Nature Science Foundation of China(nos.62373289,62273256,and 62088101)the Fundamental Research Funds for the Central Universities.
文摘With the development of artificial intelligence and breakthroughs in deep learning,large-scale foundation models(FMs),such as generative pre-trained transformer(GPT),Sora,etc.,have achieved remarkable results in many fields including natural language processing and computer vision.The application of FMs in autonomous driving holds considerable promise.For example,they can contribute to enhancing scene understanding and reasoning.By pre-training on rich linguistic and visual data,FMs can understand and interpret various elements in a driving scene,and provide cognitive reasoning to give linguistic and action instructions for driving decisions and planning.Furthermore,FMs can augment data based on the understanding of driving scenarios to provide feasible scenes of those rare occurrences in the long tail distribution that are unlikely to be encountered during routine driving and data collection.The enhancement can subsequently lead to improvement in the accuracy and reliability of autonomous driving systems.Another testament to the potential of FMs'applications lies in world models,exemplified by the DREAMER series,which showcases the ability to comprehend physical laws and dynamics.Learning from massive data under the paradigm of self-supervised learning,world models can generate unseen yet plausible driving environments,facilitating the enhancement in the prediction of road users'behaviors and the off-line training of driving strategies.In this paper,we synthesize the applications and future trends of FMs in autonomous driving.By utilizing the powerful capabilities of FMs,we strive to tackle the potential issues stemming from the long-tail distribution in autonomous driving,consequently advancing overall safety in this domain.
文摘In this study, a boron-doped microporous carbon （BMC）/sulfur nanocomposite is synthesized and applied as a novel cathode material for advanced Li-S batteries. The cell with this cathode exhibits an ultrahigh cycling stability and rate capability. After activation, a capacity of 749.5 mAh/g was obtained on the 54t＂ cycle at a discharge current of 3.2 A/g. After 500 cycles, capacity of 561.8 mAh/g remained （74.96% retention）, with only a very small average capacity decay of 0.056%. The excellent reversibility and stability of the novel sulfur cathode can be attributed to the ability of the boron-doped microporous carbon host to both physically confine polysulfides and chemically bind these species on the host surface. Theoretical calculations confirm that boron-doped carbon is capable of significantly stronger interactions with the polysulfide species than undoped carbon, most likely as a result of the lower electronegativity of boron. We believe that this doping strategy can be extended to other metal-air batteries and fuel cells, and that it has promising potential for many different applications.
基金supported by the National Natural Science Foundation of China(41625020 and 41571130035)the Ford Company, U.S.DOE grant #DE-SC0006695 at NCSU+1 种基金China's Special Scientific Research Funds for Environment Protection Commonweal Section(201409027)a DOE Office of Science User Facility supported by the Office of Science of the U.S.Department of Energy (DE-AC02-05CH11231)
文摘The Beijing-Tianjin-Hebei （BTH） region is one of the most heavily polluted regions in China, with both high PM2.5 concentrations and a high population density. A quantitative source-receptor relationship can provide valuable insights that can inform effective emission control strategies. Both source appor- tionment （SA） and source sensitivity （SS） can provide such information from different perspectives. In this study, both methods are applied in northern China to identify the most significant emission cate- gories and source regions for PMz5 exposure in BTH in 2013. Despite their differences, both models show similar distribution patterns for population and simulated PM2.5 concentrations, resulting in overall high PM2.5 exposure values （approximately 110 Ixg/m3） and particularly high exposure values during the win- ter （approximately 200 ktg/m3）. Both methods show that local emissions play a dominant role （70%）, with some contribution from surrounding provinces （e.g., Shandong） via regional transport. The two methods also agree on the priority of local emission controls： both identify industrial, residential, and agricultural emissions as the top three categories that should be controlled locally. In addition, the effect of control- ling agricultural ammonia emissions is approximately doubled when the co-benefits of reducing nitrate are considered. The synthesis of SA and SS for addressing specific categories of emissions provides a quantitative basis for the development of emission control strategies and policies for controlling PM2.5 in China.
