To reduce greenhouse gases emission and increase the renewable energy uti</span><span style="font-family:Verdana;">lization portion in the world, the biomass gasification coupled with a coal-fire...To reduce greenhouse gases emission and increase the renewable energy uti</span><span style="font-family:Verdana;">lization portion in the world, the biomass gasification coupled with a coal-fired </span><span style="font-family:Verdana;">boiler power generation system is studied. It is a challenge to achieve optimum performance for the coupled system. The models of biomass gasification coupled with co-firing of coal in a boiler have been established. A comparative study of three kinds of biomass (Food Rubbish, Straw and Wood Pellets) has </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">been </span></span></span><span><span><span><span style="font-family:Verdana;">done. The syngas produced in a 10 t/h gasifier is fed to a 330 MWe coal-fired boiler for co-combustion, and the co-firing performances have been compared with pure coal combustion case under the conditions of constant boiler load. Results show that co-firing decreases the furnace combustion temperature and raises the flue gas temperature for Food Rubbish and Straw, while, flue gases temperature decrease in case of Wood Pellets. At the same time NO<sub>x</sub> and SO<sub>x</sub> emissions have reduced. The system efficiencies at constant load for Food Rubbish, Straw and Wood Pellets are 83.25%, </span><span style="font-family:Verdana;">83.88% and 82.56% when the optimum conditions of gasification and co-firing </span><span style="font-family:Verdana;">process are guaranteed.展开更多
2,5-Furandicarboxylic acid (FDCA) is a potential biorenewable chemical for applications including plastics, polyamides, drugs, etc. The selective biosynthesis of FDCA from 5-hydroxymethylfurfural (HMF) by a speci c en...2,5-Furandicarboxylic acid (FDCA) is a potential biorenewable chemical for applications including plastics, polyamides, drugs, etc. The selective biosynthesis of FDCA from 5-hydroxymethylfurfural (HMF) by a speci c enzyme poses a great challenge. In this study, we reported an e cient strategy to produce FDCA from HMF by the tandem biocatalysis of laccase (CotA-TJ102@UIO-66-NH 2 ) and Novozym 435. For the rst step, a nanoparticle metal organic framework was synthesized as a carrier to immobilize CotA-TJ102@UIO-66-NH 2 , which was assigned for the production of 5-formyl-2-furancarboxylic acid (FFCA) and featured an enzyme loading of 255.54 mg/g, speci c activity of 135.90 U/mg, and solid loading ratio of 99.65%. Under optimal conditions, an ideal FFCA yield of 98.5% was achieved, and the CotA-TJ102@UIO-66-NH2 pre- sented a high recycling capacity after 10 cycles. For the second step, Novozym 435 was applied for the further conversion of FFCA into FDCA, presenting a high FDCA yield of 95.5% under the optimized conditions. Novozym 435 also exhibited a high recyclability after eight cycles. As a result, the tandem biocatalysis strategy provided a 94.2% FDCA yield from HMF, indicating its excellence as a method for FDCA production.展开更多
The adoption of applicable artificial intelligence technologies to library real-time virtual reference services is an innovative experimentation in one of the key areas of library services. Based on the open source so...The adoption of applicable artificial intelligence technologies to library real-time virtual reference services is an innovative experimentation in one of the key areas of library services. Based on the open source software Artificial Linguistic Internet Computer Entity(A.L.I.C.E.) and a combined application of several other relevant supporting technologies for facilitating the use of the current existing library resources, Tsinghua University Library has recently developed a real-time smart talking robot, named Xiaotu,for the enhancement of its various service functions, such as reference services, book searching, Baidu Baike searching, self-directed learning, etc. The operation of Xiaotu is programmed into Renren website(a social networking website), which adds significantly an innovative feature to the modus operandi of the real-time virtual reference service at Tsinghua University Library.展开更多
The fuel staging combustion technology is a promising low NOx combustion technology for coal-fired boiler. In order to reduce NOx emissions, the burners of a 600?MWe coal-fired boiler are retrofitted in which methane ...The fuel staging combustion technology is a promising low NOx combustion technology for coal-fired boiler. In order to reduce NOx emissions, the burners of a 600?MWe coal-fired boiler are retrofitted in which methane gas is selected as a secondary fuel for re-combustion. The CFD models of combustion process are built to investigate?effects of the methane gasratio on combustion process and NOx emissions. A total of 4 cases are numerically studied, including the pure coal combustion case, the coal combustion with 7.5%, 10%, 12.5% of methane gas re-combustion cases respectively. The results show that the re-combustion of methane can reduce the temperature at primary combustion zone, but increase the temperatures at the re-combustion area and the furnace outlet. The NOx concentration at the furnace outlet reduces with the increasing methane gas ratio.?Methane re-combustion can greatly benefit to the NOx emissions reduction.展开更多
In recent years, along with the development of education reform, the educational concepts have been updated continuously and the new educational theory is perfecting step by step. The students that the teachers contac...In recent years, along with the development of education reform, the educational concepts have been updated continuously and the new educational theory is perfecting step by step. The students that the teachers contact now are new-style students of great personalities and thoughts. The old nanny-style head teacher isn't suitable in modern time anymore. Only constant learning, constant innovation and constant surpassing yourself can make the successors adapt to the modern society. As an organizer and director of the class, how does the head teacher implement the enterprise management mode in the class management as the quality educational theory updating continuously? This subject is based on the widely proposed "class management under enterprise mode" to rethink the new class management methods under the new situation through the research and practice in one's own class and provide a new effective and feasible mode for the class management in the future.展开更多
Tsinghua University Library recently launched Tsinghua Wireless and Mobile Digital Library System(TWIMS) to meet users’ need for wireless access to library services.A survey of user experience about TWIMS was carried...Tsinghua University Library recently launched Tsinghua Wireless and Mobile Digital Library System(TWIMS) to meet users’ need for wireless access to library services.A survey of user experience about TWIMS was carried out for the purpose of studying its users’ behavior and their level of satisfaction about the system design and its various performance indicators. Based on our research findings, we concluded our research paper with a set of evaluative comments and suggestions. Those remarks are aimed at furthering the TWIMS’ functionality and reconstructing a more sensible questionnaire survey appertaining to the system users’ experience as well in the next phase of our extended research.展开更多
The ablation behaviour of(Hf-Ta-Zr-Nb)C high entropy carbide(HEC4)was studied at temperatures above 2100℃using a plasma flame gun in air.The microstructures,phase and chemical compositions of the HEC4 samples were in...The ablation behaviour of(Hf-Ta-Zr-Nb)C high entropy carbide(HEC4)was studied at temperatures above 2100℃using a plasma flame gun in air.The microstructures,phase and chemical compositions of the HEC4 samples were investigated after ablation.The mass ablation rate of the HEC4 samples increased with increasing ablation time from 0.21 mg cm^(−2)s^(−1)for 60 s to 0.45 mg cm^(−2)s^(−1)for 120 s.Com-pared to the mono-and binary carbides with commonly decreased mass and thickness after ablation,the HEC4 samples with the increased mass and thickness after ablation showed good resistance to mechan-ical scouring at such high temperatures and an oxidation controlled ablation mechanism.The ablation processes mainly include the oxidation of the carbide,the phase separation of the oxides,the melting of oxides,and the diffusion of oxygen.A composition gradient in the oxide layer was detected due to the different melting temperatures of the different oxides;Nb-Ta rich oxides formed at the front surface melted and became enriched at the edge of the samples,and the Zr-Hf rich oxides were enriched in the centre of the samples.The oxide layer with complex compositions and phase distributions acted as an effective ablation barrier.展开更多
Plasmonic nanostructures have been widely used for photochemical conversions due to their unique and easy-tuning optical properties in visible and near-infrared range.Compared with the plasmon-generated hot electrons,...Plasmonic nanostructures have been widely used for photochemical conversions due to their unique and easy-tuning optical properties in visible and near-infrared range.Compared with the plasmon-generated hot electrons,the hot holes usually have a shorter lifetime,which makes them more difficult to drive redox reactions.This review focuses on the photochemistry driven by the plasmon-generated hot holes.First,we discuss the generation and energy distribution of the plasmon-generated hot carriers,especially hot holes.Then,the dynamics of the hot holes are discussed at the interface between plasmonic metal and semiconductor or adsorbed molecules.Afterwards,the utilization of these hot holes in redox reactions is reviewed on the plasmon-semiconductor heterostructures as well as on the surface of the molecule-adsorbed plasmonic metals.Finally,the remaining challenges and future perspectives in this field are presented.This review will be helpful for further improving the efficiency of the photochemical reactions involving the plasmon-generated hot holes and expanding the applications of these hot holes in varieties of chemical reactions,especially the ones with high conversion rate and selectivity.展开更多
In this study,unsupervised and supervised pattern recognition were implemented in combination to achieve real-time health monitoring.Unsupervised recognition(k-means++)was used to label the spectral characteristics of...In this study,unsupervised and supervised pattern recognition were implemented in combination to achieve real-time health monitoring.Unsupervised recognition(k-means++)was used to label the spectral characteristics of acoustic emission(AE)signals after completing the tensile tests at ambient temperature.Using in-plane tensile at 800 and 1000°C as implementing examples,supervised recognition(K-nearest neighbor(KNN))was used to identify damage mode in real time.According to the damage identification results,four main tensile damage modes of 2D C/SiC composites were identified:matrix cracking(122.6–201 kHz),interfacial debonding(201–294.4 kHz),interfacial sliding(20.6–122.6 kHz)and fiber breaking(294.4–1000 kHz).Additionally,the damage evolution mechanisms for the 2D C/SiC composites were analyzed based on the characteristics of AE energy accumulation curve during the in-plane tensile loading at ambient and elevated temperature with oxidation.Meanwhile,the energy of various damage modes was accurately calculated by harmonic wavelet packet and the damage degree of modes could be analyzed.The identification results show that compared with previous studies,using the AE analysis method,the method has higher sensitivity and accuracy.展开更多
As synthetic biology enters the era of quantitative biology,mathematical information such as kinetic parameters of enzymes can offer us an accurate knowledge of metabolism and growth of cells,and further guidance on p...As synthetic biology enters the era of quantitative biology,mathematical information such as kinetic parameters of enzymes can offer us an accurate knowledge of metabolism and growth of cells,and further guidance on precision metabolic engineering.k_(cat),termed the turnover number,is a basic parameter of enzymes that describes the maximum number of substrates converted to products each active site per unit time.It reflects enzyme activity and is essential for quantitative understanding of biosystems.Usually,the k_(cat) values are measured in vitro,thus may not be able to reflect the enzyme activity in vivo.In this case,Davidi et al.defined a surrogate K^(vivo)_(max)(k_(app))for kcat and developed a high throughput method to acquire K^(vivo)_(max)from omics data.Heckmann et al.and Chen et al.proved that the surrogate parameter can be a good embodiment of the physiological state of enzymes and exhibit superior performance for enzyme-constrained metabolic model to the default one.These breakthroughs will fuel the development of system and synthetic biology.展开更多
文摘To reduce greenhouse gases emission and increase the renewable energy uti</span><span style="font-family:Verdana;">lization portion in the world, the biomass gasification coupled with a coal-fired </span><span style="font-family:Verdana;">boiler power generation system is studied. It is a challenge to achieve optimum performance for the coupled system. The models of biomass gasification coupled with co-firing of coal in a boiler have been established. A comparative study of three kinds of biomass (Food Rubbish, Straw and Wood Pellets) has </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">been </span></span></span><span><span><span><span style="font-family:Verdana;">done. The syngas produced in a 10 t/h gasifier is fed to a 330 MWe coal-fired boiler for co-combustion, and the co-firing performances have been compared with pure coal combustion case under the conditions of constant boiler load. Results show that co-firing decreases the furnace combustion temperature and raises the flue gas temperature for Food Rubbish and Straw, while, flue gases temperature decrease in case of Wood Pellets. At the same time NO<sub>x</sub> and SO<sub>x</sub> emissions have reduced. The system efficiencies at constant load for Food Rubbish, Straw and Wood Pellets are 83.25%, </span><span style="font-family:Verdana;">83.88% and 82.56% when the optimum conditions of gasification and co-firing </span><span style="font-family:Verdana;">process are guaranteed.
基金supported by the National Key R&D Program of China (No. 2017YFB0306502)the Science Fund for Creative Research Groups (No. 21621004)+2 种基金the Project funded by China Postdoctoral Science Foundation (2019)the Key Project of Tianjin Science and Technology Committee (No. 17YFZCSY01080)the Program of Beiyang Young Scholar of Tianjin University (2012)
文摘2,5-Furandicarboxylic acid (FDCA) is a potential biorenewable chemical for applications including plastics, polyamides, drugs, etc. The selective biosynthesis of FDCA from 5-hydroxymethylfurfural (HMF) by a speci c enzyme poses a great challenge. In this study, we reported an e cient strategy to produce FDCA from HMF by the tandem biocatalysis of laccase (CotA-TJ102@UIO-66-NH 2 ) and Novozym 435. For the rst step, a nanoparticle metal organic framework was synthesized as a carrier to immobilize CotA-TJ102@UIO-66-NH 2 , which was assigned for the production of 5-formyl-2-furancarboxylic acid (FFCA) and featured an enzyme loading of 255.54 mg/g, speci c activity of 135.90 U/mg, and solid loading ratio of 99.65%. Under optimal conditions, an ideal FFCA yield of 98.5% was achieved, and the CotA-TJ102@UIO-66-NH2 pre- sented a high recycling capacity after 10 cycles. For the second step, Novozym 435 was applied for the further conversion of FFCA into FDCA, presenting a high FDCA yield of 95.5% under the optimized conditions. Novozym 435 also exhibited a high recyclability after eight cycles. As a result, the tandem biocatalysis strategy provided a 94.2% FDCA yield from HMF, indicating its excellence as a method for FDCA production.
基金supported by the Foundation for Humanities and Social Sciences of the Chinese Ministry of Education(Grant No.:11BTQ011)
文摘The adoption of applicable artificial intelligence technologies to library real-time virtual reference services is an innovative experimentation in one of the key areas of library services. Based on the open source software Artificial Linguistic Internet Computer Entity(A.L.I.C.E.) and a combined application of several other relevant supporting technologies for facilitating the use of the current existing library resources, Tsinghua University Library has recently developed a real-time smart talking robot, named Xiaotu,for the enhancement of its various service functions, such as reference services, book searching, Baidu Baike searching, self-directed learning, etc. The operation of Xiaotu is programmed into Renren website(a social networking website), which adds significantly an innovative feature to the modus operandi of the real-time virtual reference service at Tsinghua University Library.
文摘The fuel staging combustion technology is a promising low NOx combustion technology for coal-fired boiler. In order to reduce NOx emissions, the burners of a 600?MWe coal-fired boiler are retrofitted in which methane gas is selected as a secondary fuel for re-combustion. The CFD models of combustion process are built to investigate?effects of the methane gasratio on combustion process and NOx emissions. A total of 4 cases are numerically studied, including the pure coal combustion case, the coal combustion with 7.5%, 10%, 12.5% of methane gas re-combustion cases respectively. The results show that the re-combustion of methane can reduce the temperature at primary combustion zone, but increase the temperatures at the re-combustion area and the furnace outlet. The NOx concentration at the furnace outlet reduces with the increasing methane gas ratio.?Methane re-combustion can greatly benefit to the NOx emissions reduction.
文摘In recent years, along with the development of education reform, the educational concepts have been updated continuously and the new educational theory is perfecting step by step. The students that the teachers contact now are new-style students of great personalities and thoughts. The old nanny-style head teacher isn't suitable in modern time anymore. Only constant learning, constant innovation and constant surpassing yourself can make the successors adapt to the modern society. As an organizer and director of the class, how does the head teacher implement the enterprise management mode in the class management as the quality educational theory updating continuously? This subject is based on the widely proposed "class management under enterprise mode" to rethink the new class management methods under the new situation through the research and practice in one's own class and provide a new effective and feasible mode for the class management in the future.
基金supported by the Foundation for Humanities and Social Sciences of the Chinese Ministry of Education(Grant Nos.:08JA870010 and 11BTQ011)
文摘Tsinghua University Library recently launched Tsinghua Wireless and Mobile Digital Library System(TWIMS) to meet users’ need for wireless access to library services.A survey of user experience about TWIMS was carried out for the purpose of studying its users’ behavior and their level of satisfaction about the system design and its various performance indicators. Based on our research findings, we concluded our research paper with a set of evaluative comments and suggestions. Those remarks are aimed at furthering the TWIMS’ functionality and reconstructing a more sensible questionnaire survey appertaining to the system users’ experience as well in the next phase of our extended research.
基金financially supported by the National Natural Science Foundation of China (Nos. 51602325, 91960102, and 51572224)the Natural Science Foundation of Shanghai (No.20ZR1465400)+1 种基金111 Project (No. BP0820014)financial support from China Scholarship Council
文摘The ablation behaviour of(Hf-Ta-Zr-Nb)C high entropy carbide(HEC4)was studied at temperatures above 2100℃using a plasma flame gun in air.The microstructures,phase and chemical compositions of the HEC4 samples were investigated after ablation.The mass ablation rate of the HEC4 samples increased with increasing ablation time from 0.21 mg cm^(−2)s^(−1)for 60 s to 0.45 mg cm^(−2)s^(−1)for 120 s.Com-pared to the mono-and binary carbides with commonly decreased mass and thickness after ablation,the HEC4 samples with the increased mass and thickness after ablation showed good resistance to mechan-ical scouring at such high temperatures and an oxidation controlled ablation mechanism.The ablation processes mainly include the oxidation of the carbide,the phase separation of the oxides,the melting of oxides,and the diffusion of oxygen.A composition gradient in the oxide layer was detected due to the different melting temperatures of the different oxides;Nb-Ta rich oxides formed at the front surface melted and became enriched at the edge of the samples,and the Zr-Hf rich oxides were enriched in the centre of the samples.The oxide layer with complex compositions and phase distributions acted as an effective ablation barrier.
基金This work was supported by National Natural Science Foundation of China(No.11974180)Key University Science Research Project of Jiangsu Province(No.17KJA150005)+1 种基金Six Talent Peaks Project in Jiangsu Province(No.XCL-038)Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX20_1060).
文摘Plasmonic nanostructures have been widely used for photochemical conversions due to their unique and easy-tuning optical properties in visible and near-infrared range.Compared with the plasmon-generated hot electrons,the hot holes usually have a shorter lifetime,which makes them more difficult to drive redox reactions.This review focuses on the photochemistry driven by the plasmon-generated hot holes.First,we discuss the generation and energy distribution of the plasmon-generated hot carriers,especially hot holes.Then,the dynamics of the hot holes are discussed at the interface between plasmonic metal and semiconductor or adsorbed molecules.Afterwards,the utilization of these hot holes in redox reactions is reviewed on the plasmon-semiconductor heterostructures as well as on the surface of the molecule-adsorbed plasmonic metals.Finally,the remaining challenges and future perspectives in this field are presented.This review will be helpful for further improving the efficiency of the photochemical reactions involving the plasmon-generated hot holes and expanding the applications of these hot holes in varieties of chemical reactions,especially the ones with high conversion rate and selectivity.
基金the National Natural Science Foundation of China(Grant No.12172304)the 111 Project(Grant No.BP0719007).
文摘In this study,unsupervised and supervised pattern recognition were implemented in combination to achieve real-time health monitoring.Unsupervised recognition(k-means++)was used to label the spectral characteristics of acoustic emission(AE)signals after completing the tensile tests at ambient temperature.Using in-plane tensile at 800 and 1000°C as implementing examples,supervised recognition(K-nearest neighbor(KNN))was used to identify damage mode in real time.According to the damage identification results,four main tensile damage modes of 2D C/SiC composites were identified:matrix cracking(122.6–201 kHz),interfacial debonding(201–294.4 kHz),interfacial sliding(20.6–122.6 kHz)and fiber breaking(294.4–1000 kHz).Additionally,the damage evolution mechanisms for the 2D C/SiC composites were analyzed based on the characteristics of AE energy accumulation curve during the in-plane tensile loading at ambient and elevated temperature with oxidation.Meanwhile,the energy of various damage modes was accurately calculated by harmonic wavelet packet and the damage degree of modes could be analyzed.The identification results show that compared with previous studies,using the AE analysis method,the method has higher sensitivity and accuracy.
基金the National Natural Science Foundation of China(31922002,32101174)W.W and Z.L,the National Key R&D program of China(2020YFA0907800)+1 种基金the 111 Project(B18022),the Youth Innovation Promotion Association CAS(Y202027)W.W and the China Postdoctoral Science Foundation(2021M703379)to Z.L.
文摘As synthetic biology enters the era of quantitative biology,mathematical information such as kinetic parameters of enzymes can offer us an accurate knowledge of metabolism and growth of cells,and further guidance on precision metabolic engineering.k_(cat),termed the turnover number,is a basic parameter of enzymes that describes the maximum number of substrates converted to products each active site per unit time.It reflects enzyme activity and is essential for quantitative understanding of biosystems.Usually,the k_(cat) values are measured in vitro,thus may not be able to reflect the enzyme activity in vivo.In this case,Davidi et al.defined a surrogate K^(vivo)_(max)(k_(app))for kcat and developed a high throughput method to acquire K^(vivo)_(max)from omics data.Heckmann et al.and Chen et al.proved that the surrogate parameter can be a good embodiment of the physiological state of enzymes and exhibit superior performance for enzyme-constrained metabolic model to the default one.These breakthroughs will fuel the development of system and synthetic biology.
