Titanium alloys are excellent structural materials in engineering fields,but their poor tribological properties limit their further applications.Electroless plating is an effective method to enhance the tribological p...Titanium alloys are excellent structural materials in engineering fields,but their poor tribological properties limit their further applications.Electroless plating is an effective method to enhance the tribological performance of alloys,but it is difficult to efficiently apply to titanium alloys,due to titanium alloy’s strong chemical activity.In this work,the electroless Nickel-Boron(Ni-B)coating was successfully deposited on the surface of titanium alloy(Ti-6AL-4V)via a new pre-treatment process.Then,linearly reciprocating sliding wear tests were performed to evaluate the tribological behaviors of titanium alloy and its electroless Ni-B coatings.It was found that the Ni-B coatings can decrease the wear rate of the titanium alloy from 19.89×10^(−3)mm^(3)to 0.41×10^(−3)mm^(3),which attributes to the much higher hardness of Ni-B coatings.After heat treatment,the hardness of Ni-B coating further increases corresponding to coating crystallization and hard phase formation.However,heat treatment does not improve the tribological performance of Ni-B coating,due to the fact that higher brittleness and more severe oxidative wear exacerbate the damage of heat-treated coatings.Furthermore,the Ni-B coatings heat-treated both in air and nitrogen almost present the same tribological performance.The finding of this work on electroless coating would further extend the practical applications of titanium alloys in the engineering fields.展开更多
It is a challenge to polish the interior surface of an additively manufactured component with complex structures and groove sizes less than 1 mm.Traditional polishing methods are disabled to polish the component,meanw...It is a challenge to polish the interior surface of an additively manufactured component with complex structures and groove sizes less than 1 mm.Traditional polishing methods are disabled to polish the component,meanwhile keeping the structure intact.To overcome this challenge,small-grooved components made of aluminum alloy with sizes less than 1 mm were fabricated by a custom-made printer.A novel approach to multi-phase jet(MPJ)polishing is proposed,utilizing a self-developed polisher that incorporates solid,liquid,and gas phases.In contrast,abrasive air jet(AAJ)polishing is recommended,employing a customized polisher that combines solid and gas phases.After jet polishing,surface roughness(Sa)on the interior surface of grooves decreases from pristine 8.596μm to 0.701μm and 0.336μm via AAJ polishing and MPJ polishing,respectively,and Sa reduces 92%and 96%,correspondingly.Furthermore,a formula defining the relationship between linear energy density and unit defect volume has been developed.The optimized parameters in additive manufacturing are that linear energy density varies from 0.135 J mm^(-1)to 0.22 J mm^(-1).The unit area defect volume achieved via the optimized parameters decreases to 1/12 of that achieved via non-optimized ones.Computational fluid dynamics simulation results reveal that material is removed by shear stress,and the alumina abrasives experience multiple collisions with the defects on the heat pipe groove,resulting in uniform material removal.This is in good agreement with the experimental results.The novel proposed setups,approach,and findings provide new insights into manufacturing complex-structured components,polishing the small-grooved structure,and keeping it unbroken.展开更多
Tea plants(Camellia sinensis)are commercially cultivated in>60 countries,and their fresh leaves are processed into tea,which is the most widely consumed beverage in the world.Although several chromosome-level tea p...Tea plants(Camellia sinensis)are commercially cultivated in>60 countries,and their fresh leaves are processed into tea,which is the most widely consumed beverage in the world.Although several chromosome-level tea plant genomes have been published,they collapsed the two haplotypes and ignored a large number of allelic variations that may underlie important biological functions in this species.Here,we present a phased chromosome-scale assembly for an elite oolong tea cultivar,"Huangdan",that is well known for its high levels of aroma.Based on the two sets of haplotype genome data,we identi fi ed numerous genetic variations and a substantial proportion of allelic imbalance related to important traits,including aroma-and stress-related alleles.Comparative genomics revealed extensive structural variations as well as expansion of some gene families,such as terpene synthases(TPSs),that likely contribute to the high-aroma characteristics of the backbone parent,underlying the molecular basis for the biosynthesis of aroma-related chemicals in oolong tea.Our results uncovered the genetic basis of special features of this oolong tea cultivar,providing fundamental genomic resources to study evolution and domestication for the economically important tea crop.展开更多
To objectively reflect the relevant situation of researches on think tank service of Chinese university libraries, this paper uses CNKI Database as the retrieval source, the bibliometric analysis method, and CiteSpace...To objectively reflect the relevant situation of researches on think tank service of Chinese university libraries, this paper uses CNKI Database as the retrieval source, the bibliometric analysis method, and CiteSpace, a citation network analysis tool, to make quantitative analysis on the literature data of researches on the think tank service of university libraries;draw the knowledge map of literature authors, organization distribution, keyword co-occurrence, research hotspot distribution, etc.;objectively and comprehensively analyzes the hot topics and cutting-edge trends of researches on the think tank service of libraries, the research includes the following aspects: First, the status quo and orientation of the existing university library think tanks in China;second, it is recommended to carry out research on policy support and system guarantee for university library think tank services;third, integrate big data technology is merged into the construction of university libraries think tanks;fourth, the transformation of library and information institutions to new types of think tanks, including the transformation of knowledge services, disciplinary services, and characteristic think tanks, in order to provide reference for researches and practical work of think tank service of libraries in China.展开更多
Dear Editor,Tea plant(Camellia sinensis(L.)O.Kuntze)is one of the world’s most important non-alcoholic beverages,with great economic,health,and cultural value.Recently,several genomes of C.sinensis var.assamica(CSA)(...Dear Editor,Tea plant(Camellia sinensis(L.)O.Kuntze)is one of the world’s most important non-alcoholic beverages,with great economic,health,and cultural value.Recently,several genomes of C.sinensis var.assamica(CSA)(Yunkang 10),C.sinensis var.sinensis(CSS)(Shuchazao,Biyun,Longjing 43,Tieguanyin,Huangdan),and ancient tea plant(DASZ)have been deciphered[1-3].展开更多
High-performance devices usually have curved surfaces, requiring high accuracy of shape and low surface roughness. It is a challenge to achieve high accuracies for form and position on a device with low surface roughn...High-performance devices usually have curved surfaces, requiring high accuracy of shape and low surface roughness. It is a challenge to achieve high accuracies for form and position on a device with low surface roughness. However, due to the unique nonlinear rheology, magnetorheological fluids with hard abrasives are widely applied in ultra-precision surface finishing. Compared with conventional mechanical finishing, magnetorheological finishing displays obviously advantages, such as high precision shape of machined surface, low surface roughness and subsurface damage, and easy control for finishing processes. However, finishing performance depends on various factors, e.g. volume fraction and distribution of magnetic particles, types of hard abrasives and additives, strength of magnetic field, finishing forms. Therefore, a comprehensive review on related works is essential to understand the state-of-the-art of magnetorheological finishing and beneficial to inspire researchers to develop lower cost, higher machining accuracy and efficient approaches and setups, which demonstrates a significant guidance for development of high-performance parts in fields of aerospace, navigation and clinical medicine etc. This review starts from the rheological property of magnetorheological fluids, summarizing dynamically nonlinear rheological properties and stable finishing approaches. Then, the effect of components in magnetorheological fluids is discussed on finishing performance, consisting of magnetic particles, carrier fluid, additives and abrasives. Reasonable configuration of magnetorheological fluids, and different magnetorheological finishing methods are presented for variously curved surfaces. In addition, the current finishing forms and future directions are also addressed in this review.展开更多
Processing(grinding,polishing)of phosphate laser(PL)glass involves material removal at two vastly different(spatial)scales.In this study,the nano‐and macro‐tribological properties of PL glass are investigated by rub...Processing(grinding,polishing)of phosphate laser(PL)glass involves material removal at two vastly different(spatial)scales.In this study,the nano‐and macro‐tribological properties of PL glass are investigated by rubbing the glass against a SiO_(2) counter‐surface in both dry and humid conditions.The results indicate that the friction of the PL glass/SiO_(2) pair has opposing trends at the nano‐and macroscales.At the nanoscale,the friction coefficient(COF)in humid air is much higher than in dry air,which is attributed to the capillary effect of the absorbed water‐film at the interface.At the macroscale,on the other hand,the COF in humid air is lower than in dry air,because the water‐related mechanochemical wear makes the worn surface less susceptible to cracking.Material removal for PL glass is better facilitated by humid air than by dry air at both scales,because the stress‐enhanced hydrolysis accelerates the material‐removal process in glass.Moreover,the material‐removal is more sensitive to contact pressure at the macroscale,because stronger mechanical‐interaction occurs during material removal at the macroscale with the multi asperity contact mode.At the macroscale,the material removal is more sensitive to contact pressure in humid air compared to dry air.Because almost all mechanical energy is used to remove material in humid air,and most of the mechanical energy is used to produce cracks in PL glass in dry air.The results of this study can help optimize the multi‐scale surface processing of optical glasses.展开更多
Tribology behaviors of energetic crystals play critical roles in the friction-induced hotspot in highenergy explosive,however,the binder and energetic crystals are not distinguished properly in previous investigations...Tribology behaviors of energetic crystals play critical roles in the friction-induced hotspot in highenergy explosive,however,the binder and energetic crystals are not distinguished properly in previous investigations.In this study,for the first time,the nanoscale friction ofβ-octahydro-1,3,5,7-tetranitro1,3,5,7-tetrazocine(β-HMX)crystal is studied with nanoscratch tests under the ramping load mode.The results show that the nanoscale friction and wear ofβ-HMX crystal,as a typical energetic material,is highly depended on the applied load.The friction coefficient ofβ-HMX crystal is initially high when no discernible wear is observed,and then it decreases to a stable value which varies from~0.2 to~0.7,depending on the applied load,scratch direction,and crystal planes.Theβ-HMX(011)surfaces show weakly friction and wear anisotropy behavior;in contrast,theβ-HMX(110)surfaces show strongly friction and wear anisotropy behavior where the friction coefficient,critical load for the elastic–plastic deformation transition and plastic–cracking deformation transition,and deformation index at higher normal load are highly depended on the scratch directions.Further analyses indicate the slip system and direction ofβ-HMX surfaces play key roles in determining the nanoscale friction and wear ofβ-HMX surfaces.The obtained results can provide deeper insight into the friction and wear of energetic crystal materials.展开更多
Over the past 20 years,tremendous advances in sequencing technologies and computational algorithms have spurred plant genomic research into a thriving era with hundreds of genomes decoded already,ranging from those of...Over the past 20 years,tremendous advances in sequencing technologies and computational algorithms have spurred plant genomic research into a thriving era with hundreds of genomes decoded already,ranging from those of nonvascular plants to those of flowering plants.However,complex plant genome assembly is still challenging and remains difficult to fully resolve with conventional sequencing and assembly methods due to high heterozygosity,highly repetitive sequences,or high ploidy characteristics of complex genomes.Herein,we summarize the challenges of and advances in complex plant genome assembly,including feasible experimental strategies,upgrades to sequencing technology,existing assembly methods,and different phasing algorithms.Moreover,we list actual cases of complex genome projects for readers to refer to and draw upon to solve future problems related to complex genomes.Finally,we expect that the accurate,gapless,telomere-totelomere,and fully phased assembly of complex plant genomes could soon become routine.展开更多
Reinforcing fillers are of great importance in tribological performance and tribofilm formation of polymeric composites.In this study,the tribological properties of aramid particle(AP)and short carbon fiber(SCF)reinfo...Reinforcing fillers are of great importance in tribological performance and tribofilm formation of polymeric composites.In this study,the tribological properties of aramid particle(AP)and short carbon fiber(SCF)reinforced polyimide(PI)composites were added to hexagonal boron nitride(h-BN),and silica(SiO_(2))nanoparticles sliding against alumina were comprehensively investigated.When sliding occurred with AP-reinforced PI composites,the tribological properties were not closely depended on the pressure×velocity(p×v)factors and the nanoparticles.The interactions between AP and its counterpart could not induce tribo-sintering of the transferred wear debris.As such,the tribofilm seemed to be in a viscous state,leading to higher friction and wear.However,the inclusion of hard SCF into the PI matrix changed the interfacial interactions with alumina.A robust tribofilm consisting of a high fraction of silica was generated when the SCF-reinforced PI was added to the SiO_(2) nanoparticles.It exhibited a high load-carrying capability and was easily sheared.This caused a significant decrease in the friction and wear of the PI composite at 8 MPa·1m/s.Moreover,due to their high melting point,few h-BN nanoparticles were observed in the tribofilm of the SCF-reinforced PI when hexagonal boron nitride was added.展开更多
A high-throughput approach based on magnetron co-sputtering of alloy libraries is employed to investigate mechanical properties of crystalline and amorphous alloys in a ternary palladium(Pd)-tungsten(W)-silicon(Si)sys...A high-throughput approach based on magnetron co-sputtering of alloy libraries is employed to investigate mechanical properties of crystalline and amorphous alloys in a ternary palladium(Pd)-tungsten(W)-silicon(Si)system with the aim to reveal the difference in plastic deformation response and extract the relevant structure-property relationships of the alloys in the system.It was found that in contrast to crystalline alloys,the amorphous ones,i.e.,metallic glasses,exhibited a much smaller fluctuation range in the plasticity parameters(Er2/H and Wp/Wt),indicating a significant difference in the plastic deformation mechanism controlling the mechanical properties for the respective alloys.We propose that the inhomogeneous deformation of amorphous alloys localized in thin shear bands is responsible for the weaker compositional dependence of both plasticity parameters,while dislocation gliding in crystalline materials is significantly more dependent on the exact structure,thus resulting in a larger scattering range.Based on the representative efficient cluster packing model,a set of composition-dependent atomic structural models is proposed to figure out the structure-property relationships of amorphous alloys in Pd-W-Si alloy system.展开更多
We demonstrate an effective approach of mode suppression by simply using a tungsten probe to destroy the external neck surface of polymer microbottle resonators.The higher-order bottle modes with large axial orders,sp...We demonstrate an effective approach of mode suppression by simply using a tungsten probe to destroy the external neck surface of polymer microbottle resonators.The higher-order bottle modes with large axial orders,spatially located around the neck surface of the microresonator,will suffer large optical losses.Thus,excitation just with an ordinary free-space light beam will ensure direct generation of single fundamental bottle mode lasers.This method is with very low cost and convenient and can obtain high side-mode suppression factors.Our work demonstrated here may have promising applications such as in lasing and sensing devices.展开更多
Background: Evidence on the relations of the American Heart Association’s ideal cardiovascular health (ICH) with mortality in Asians is sparse, and the interaction between behavioral and medical metrics remained uncl...Background: Evidence on the relations of the American Heart Association’s ideal cardiovascular health (ICH) with mortality in Asians is sparse, and the interaction between behavioral and medical metrics remained unclear. We aimed to fill the gaps. Methods: A total of 198,164 participants without cancer and cardiovascular disease (CVD) were included from the China Kadoorie Biobank study (2004-2018), Dongfeng-Tongji cohort (2008-2018), and Kailuan study (2006-2019). Four behaviors (i.e., smoking, physical activity, diet, body mass index) and three medical factors (i.e., blood pressure, blood glucose, and blood lipid) were classified into poor, intermediate, and ideal levels (0, 1, and 2 points), which constituted 8-point behavioral, 6-point medical, and 14-point ICH scores. Results of Cox regression from three cohorts were pooled using random-effects models of meta-analysis. Results: During about 2 million person-years, 20,176 deaths were recorded. After controlling for demographic characteristics and alcohol drinking, hazard ratios (95% confidence intervals) comparing ICH scores of 10-14 vs. 0-6 were 0.52 (0.41-0.67), 0.44 (0.37-0.53), 0.54 (0.45-0.66), and 0.86 (0.64-1.14) for all-cause, CVD, respiratory, and cancer mortality. A higher behavioral or medical score was independently associated with lower all-cause and CVD mortality among the total population and populations with different levels of behavioral or medical health equally, and no interaction was observed. Conclusions: ICH was associated with lower all-cause, CVD, and respiratory mortality among Chinese adults. Both behavioral and medical health should be improved to prevent premature deaths.展开更多
We developed for the first time an unprecedented domino reaction of sulfonyl oximonitriles with secondary amines to streamline the synthesis of N-sulfonylformamidines in decent to high yields under mild reaction condi...We developed for the first time an unprecedented domino reaction of sulfonyl oximonitriles with secondary amines to streamline the synthesis of N-sulfonylformamidines in decent to high yields under mild reaction conditions.In addition,scale-up experiments and late-stage functionalization of drugs were also performed.Preliminary studies indicate that the loss of a cyano-/benzyloxy-group and a sulfonyl migration process are involved in this reaction.展开更多
基金Supported by Sichuan Provincial Science and Technology Program of China(Grant No.2018JY0245)National Natural Science Foundation of China(Grant No.51975492)Natural Science Foundation of Southwest University of Science and Technology of China(Grant No.19xz7163).
文摘Titanium alloys are excellent structural materials in engineering fields,but their poor tribological properties limit their further applications.Electroless plating is an effective method to enhance the tribological performance of alloys,but it is difficult to efficiently apply to titanium alloys,due to titanium alloy’s strong chemical activity.In this work,the electroless Nickel-Boron(Ni-B)coating was successfully deposited on the surface of titanium alloy(Ti-6AL-4V)via a new pre-treatment process.Then,linearly reciprocating sliding wear tests were performed to evaluate the tribological behaviors of titanium alloy and its electroless Ni-B coatings.It was found that the Ni-B coatings can decrease the wear rate of the titanium alloy from 19.89×10^(−3)mm^(3)to 0.41×10^(−3)mm^(3),which attributes to the much higher hardness of Ni-B coatings.After heat treatment,the hardness of Ni-B coating further increases corresponding to coating crystallization and hard phase formation.However,heat treatment does not improve the tribological performance of Ni-B coating,due to the fact that higher brittleness and more severe oxidative wear exacerbate the damage of heat-treated coatings.Furthermore,the Ni-B coatings heat-treated both in air and nitrogen almost present the same tribological performance.The finding of this work on electroless coating would further extend the practical applications of titanium alloys in the engineering fields.
基金the National Key Research and Development Program of China(2018YFA0703400)the Young Scientists Fund of the National Natural Science Foundation of China(52205447)Changjiang Scholars Program of the Chinese Ministry of Education。
文摘It is a challenge to polish the interior surface of an additively manufactured component with complex structures and groove sizes less than 1 mm.Traditional polishing methods are disabled to polish the component,meanwhile keeping the structure intact.To overcome this challenge,small-grooved components made of aluminum alloy with sizes less than 1 mm were fabricated by a custom-made printer.A novel approach to multi-phase jet(MPJ)polishing is proposed,utilizing a self-developed polisher that incorporates solid,liquid,and gas phases.In contrast,abrasive air jet(AAJ)polishing is recommended,employing a customized polisher that combines solid and gas phases.After jet polishing,surface roughness(Sa)on the interior surface of grooves decreases from pristine 8.596μm to 0.701μm and 0.336μm via AAJ polishing and MPJ polishing,respectively,and Sa reduces 92%and 96%,correspondingly.Furthermore,a formula defining the relationship between linear energy density and unit defect volume has been developed.The optimized parameters in additive manufacturing are that linear energy density varies from 0.135 J mm^(-1)to 0.22 J mm^(-1).The unit area defect volume achieved via the optimized parameters decreases to 1/12 of that achieved via non-optimized ones.Computational fluid dynamics simulation results reveal that material is removed by shear stress,and the alumina abrasives experience multiple collisions with the defects on the heat pipe groove,resulting in uniform material removal.This is in good agreement with the experimental results.The novel proposed setups,approach,and findings provide new insights into manufacturing complex-structured components,polishing the small-grooved structure,and keeping it unbroken.
基金This research was funded by the Fujian Province"2011 Collaborative Innovation Center",the Chinese Oolong Tea Industry Innovation Center special project(J 2015-75)the National Natural Science Foundation of China(31701874)+3 种基金the Major Special Project of Scientific and Technological Innovation on Anxi Tea(AX2021001)the Earmarked Fund for the China Agriculture Research System(CARS-19)the Scientific Research Foundation of the Graduate School of Fujian Agriculture and Forestry University(324-1122yb060)the Scientific Research Foundation of Horticulture College of Fujian Agriculture and Forestry University(2018B02).
文摘Tea plants(Camellia sinensis)are commercially cultivated in>60 countries,and their fresh leaves are processed into tea,which is the most widely consumed beverage in the world.Although several chromosome-level tea plant genomes have been published,they collapsed the two haplotypes and ignored a large number of allelic variations that may underlie important biological functions in this species.Here,we present a phased chromosome-scale assembly for an elite oolong tea cultivar,"Huangdan",that is well known for its high levels of aroma.Based on the two sets of haplotype genome data,we identi fi ed numerous genetic variations and a substantial proportion of allelic imbalance related to important traits,including aroma-and stress-related alleles.Comparative genomics revealed extensive structural variations as well as expansion of some gene families,such as terpene synthases(TPSs),that likely contribute to the high-aroma characteristics of the backbone parent,underlying the molecular basis for the biosynthesis of aroma-related chemicals in oolong tea.Our results uncovered the genetic basis of special features of this oolong tea cultivar,providing fundamental genomic resources to study evolution and domestication for the economically important tea crop.
文摘To objectively reflect the relevant situation of researches on think tank service of Chinese university libraries, this paper uses CNKI Database as the retrieval source, the bibliometric analysis method, and CiteSpace, a citation network analysis tool, to make quantitative analysis on the literature data of researches on the think tank service of university libraries;draw the knowledge map of literature authors, organization distribution, keyword co-occurrence, research hotspot distribution, etc.;objectively and comprehensively analyzes the hot topics and cutting-edge trends of researches on the think tank service of libraries, the research includes the following aspects: First, the status quo and orientation of the existing university library think tanks in China;second, it is recommended to carry out research on policy support and system guarantee for university library think tank services;third, integrate big data technology is merged into the construction of university libraries think tanks;fourth, the transformation of library and information institutions to new types of think tanks, including the transformation of knowledge services, disciplinary services, and characteristic think tanks, in order to provide reference for researches and practical work of think tank service of libraries in China.
基金This study was funded by Shenzhen Science and Technology Program(Grant No.RCYX20210706092103024)Key-Area Research and Development Program of Guangdong Province(2020B020220004).
文摘Dear Editor,Tea plant(Camellia sinensis(L.)O.Kuntze)is one of the world’s most important non-alcoholic beverages,with great economic,health,and cultural value.Recently,several genomes of C.sinensis var.assamica(CSA)(Yunkang 10),C.sinensis var.sinensis(CSS)(Shuchazao,Biyun,Longjing 43,Tieguanyin,Huangdan),and ancient tea plant(DASZ)have been deciphered[1-3].
基金funded by the National Key Research and Development Program of China (2018YFA0703400)the Young Scientists Fund of the National Natural Science Foundation of China (52205447)+2 种基金Changjiang Scholars Program of Chinese Ministry of Educationthe Xinghai Science Funds for Distinguished Young Scholars at Dalian University of Technologythe Collaborative Innovation Center of Major Machine Manufacturing in Liaoning。
文摘High-performance devices usually have curved surfaces, requiring high accuracy of shape and low surface roughness. It is a challenge to achieve high accuracies for form and position on a device with low surface roughness. However, due to the unique nonlinear rheology, magnetorheological fluids with hard abrasives are widely applied in ultra-precision surface finishing. Compared with conventional mechanical finishing, magnetorheological finishing displays obviously advantages, such as high precision shape of machined surface, low surface roughness and subsurface damage, and easy control for finishing processes. However, finishing performance depends on various factors, e.g. volume fraction and distribution of magnetic particles, types of hard abrasives and additives, strength of magnetic field, finishing forms. Therefore, a comprehensive review on related works is essential to understand the state-of-the-art of magnetorheological finishing and beneficial to inspire researchers to develop lower cost, higher machining accuracy and efficient approaches and setups, which demonstrates a significant guidance for development of high-performance parts in fields of aerospace, navigation and clinical medicine etc. This review starts from the rheological property of magnetorheological fluids, summarizing dynamically nonlinear rheological properties and stable finishing approaches. Then, the effect of components in magnetorheological fluids is discussed on finishing performance, consisting of magnetic particles, carrier fluid, additives and abrasives. Reasonable configuration of magnetorheological fluids, and different magnetorheological finishing methods are presented for variously curved surfaces. In addition, the current finishing forms and future directions are also addressed in this review.
基金The authors are grateful for financial support from the National Natural Science Foundation of China(Nos.51975492 and 51575462)the Scientific Research Fund of Sichuan Provincial Education Department,China(18ZA0504)+3 种基金the Research Fund Supported by Sichuan Science and Technology Program(2018JY0245)the Research Foundation of Southwest University of Science and Technology(18zx7162)the Tribology Science Fund of State Key Laboratory of Tribology(SKLTKF19B15)the Project National United Engineering Laboratory for Advanced Bearing Tribology,Henan University of Science and Technology(201910).
文摘Processing(grinding,polishing)of phosphate laser(PL)glass involves material removal at two vastly different(spatial)scales.In this study,the nano‐and macro‐tribological properties of PL glass are investigated by rubbing the glass against a SiO_(2) counter‐surface in both dry and humid conditions.The results indicate that the friction of the PL glass/SiO_(2) pair has opposing trends at the nano‐and macroscales.At the nanoscale,the friction coefficient(COF)in humid air is much higher than in dry air,which is attributed to the capillary effect of the absorbed water‐film at the interface.At the macroscale,on the other hand,the COF in humid air is lower than in dry air,because the water‐related mechanochemical wear makes the worn surface less susceptible to cracking.Material removal for PL glass is better facilitated by humid air than by dry air at both scales,because the stress‐enhanced hydrolysis accelerates the material‐removal process in glass.Moreover,the material‐removal is more sensitive to contact pressure at the macroscale,because stronger mechanical‐interaction occurs during material removal at the macroscale with the multi asperity contact mode.At the macroscale,the material removal is more sensitive to contact pressure in humid air compared to dry air.Because almost all mechanical energy is used to remove material in humid air,and most of the mechanical energy is used to produce cracks in PL glass in dry air.The results of this study can help optimize the multi‐scale surface processing of optical glasses.
基金The authors gratefully acknowledge the financial support of this work by President Foundation of China Academy of Engineering Physics(YZJJLX2020005)National Natural Science Foundation of China(Grant No.51975492)。
文摘Tribology behaviors of energetic crystals play critical roles in the friction-induced hotspot in highenergy explosive,however,the binder and energetic crystals are not distinguished properly in previous investigations.In this study,for the first time,the nanoscale friction ofβ-octahydro-1,3,5,7-tetranitro1,3,5,7-tetrazocine(β-HMX)crystal is studied with nanoscratch tests under the ramping load mode.The results show that the nanoscale friction and wear ofβ-HMX crystal,as a typical energetic material,is highly depended on the applied load.The friction coefficient ofβ-HMX crystal is initially high when no discernible wear is observed,and then it decreases to a stable value which varies from~0.2 to~0.7,depending on the applied load,scratch direction,and crystal planes.Theβ-HMX(011)surfaces show weakly friction and wear anisotropy behavior;in contrast,theβ-HMX(110)surfaces show strongly friction and wear anisotropy behavior where the friction coefficient,critical load for the elastic–plastic deformation transition and plastic–cracking deformation transition,and deformation index at higher normal load are highly depended on the scratch directions.Further analyses indicate the slip system and direction ofβ-HMX surfaces play key roles in determining the nanoscale friction and wear ofβ-HMX surfaces.The obtained results can provide deeper insight into the friction and wear of energetic crystal materials.
基金supported by the National Natural Science Foundation of China(Grant No.32222019)the National Key R&D Program of China(Grant No.2021YFF1000900).
文摘Over the past 20 years,tremendous advances in sequencing technologies and computational algorithms have spurred plant genomic research into a thriving era with hundreds of genomes decoded already,ranging from those of nonvascular plants to those of flowering plants.However,complex plant genome assembly is still challenging and remains difficult to fully resolve with conventional sequencing and assembly methods due to high heterozygosity,highly repetitive sequences,or high ploidy characteristics of complex genomes.Herein,we summarize the challenges of and advances in complex plant genome assembly,including feasible experimental strategies,upgrades to sequencing technology,existing assembly methods,and different phasing algorithms.Moreover,we list actual cases of complex genome projects for readers to refer to and draw upon to solve future problems related to complex genomes.Finally,we expect that the accurate,gapless,telomere-totelomere,and fully phased assembly of complex plant genomes could soon become routine.
基金The authors are grateful for the financial support received from National Natural Science Foundation of China(Grant Nos.51475446 and 51975492)the Research Foundation of Southwest University of Science and Technology(Grant Nos.18zx7162 and 18zx7125)Sichuan Science and Technology Program(Grant No.18YYJC0905).
文摘Reinforcing fillers are of great importance in tribological performance and tribofilm formation of polymeric composites.In this study,the tribological properties of aramid particle(AP)and short carbon fiber(SCF)reinforced polyimide(PI)composites were added to hexagonal boron nitride(h-BN),and silica(SiO_(2))nanoparticles sliding against alumina were comprehensively investigated.When sliding occurred with AP-reinforced PI composites,the tribological properties were not closely depended on the pressure×velocity(p×v)factors and the nanoparticles.The interactions between AP and its counterpart could not induce tribo-sintering of the transferred wear debris.As such,the tribofilm seemed to be in a viscous state,leading to higher friction and wear.However,the inclusion of hard SCF into the PI matrix changed the interfacial interactions with alumina.A robust tribofilm consisting of a high fraction of silica was generated when the SCF-reinforced PI was added to the SiO_(2) nanoparticles.It exhibited a high load-carrying capability and was easily sheared.This caused a significant decrease in the friction and wear of the PI composite at 8 MPa·1m/s.Moreover,due to their high melting point,few h-BN nanoparticles were observed in the tribofilm of the SCF-reinforced PI when hexagonal boron nitride was added.
基金financially supported by the National Natural Science Foundation of China(No.51975492)the Research Fund Supported by Sichuan Science and Technology Program(No.2018JY0245)+1 种基金the Natural Science Foundation of Southwest University of Science and Technology(No.19xz7163)supported by the National Science Foundation of the United States(No.NSF CMMI-1901959)。
文摘A high-throughput approach based on magnetron co-sputtering of alloy libraries is employed to investigate mechanical properties of crystalline and amorphous alloys in a ternary palladium(Pd)-tungsten(W)-silicon(Si)system with the aim to reveal the difference in plastic deformation response and extract the relevant structure-property relationships of the alloys in the system.It was found that in contrast to crystalline alloys,the amorphous ones,i.e.,metallic glasses,exhibited a much smaller fluctuation range in the plasticity parameters(Er2/H and Wp/Wt),indicating a significant difference in the plastic deformation mechanism controlling the mechanical properties for the respective alloys.We propose that the inhomogeneous deformation of amorphous alloys localized in thin shear bands is responsible for the weaker compositional dependence of both plasticity parameters,while dislocation gliding in crystalline materials is significantly more dependent on the exact structure,thus resulting in a larger scattering range.Based on the representative efficient cluster packing model,a set of composition-dependent atomic structural models is proposed to figure out the structure-property relationships of amorphous alloys in Pd-W-Si alloy system.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.11604210and 11674230)the Shanghai Rising-Star Program(No.18QA1403200)
文摘We demonstrate an effective approach of mode suppression by simply using a tungsten probe to destroy the external neck surface of polymer microbottle resonators.The higher-order bottle modes with large axial orders,spatially located around the neck surface of the microresonator,will suffer large optical losses.Thus,excitation just with an ordinary free-space light beam will ensure direct generation of single fundamental bottle mode lasers.This method is with very low cost and convenient and can obtain high side-mode suppression factors.Our work demonstrated here may have promising applications such as in lasing and sensing devices.
基金supported by grants from the National Nature Science Foundation of China(Nos.81930124 and 82021005)The Dongfeng-Tongji cohort was supported by the National Key Research and Development Program of China(Nos.2016YFC0900801 and 2017YFC0907504)+2 种基金The China Kadoorie Biobank study was funded by the National Natural Science Foundation of China(Nos.82192901,82192900,and 81390540)the National Key Research and Development Program of China(No.2016YFC0900500)and the Chinese Ministry of Science and Technology(No.2011BAI09B01).
文摘Background: Evidence on the relations of the American Heart Association’s ideal cardiovascular health (ICH) with mortality in Asians is sparse, and the interaction between behavioral and medical metrics remained unclear. We aimed to fill the gaps. Methods: A total of 198,164 participants without cancer and cardiovascular disease (CVD) were included from the China Kadoorie Biobank study (2004-2018), Dongfeng-Tongji cohort (2008-2018), and Kailuan study (2006-2019). Four behaviors (i.e., smoking, physical activity, diet, body mass index) and three medical factors (i.e., blood pressure, blood glucose, and blood lipid) were classified into poor, intermediate, and ideal levels (0, 1, and 2 points), which constituted 8-point behavioral, 6-point medical, and 14-point ICH scores. Results of Cox regression from three cohorts were pooled using random-effects models of meta-analysis. Results: During about 2 million person-years, 20,176 deaths were recorded. After controlling for demographic characteristics and alcohol drinking, hazard ratios (95% confidence intervals) comparing ICH scores of 10-14 vs. 0-6 were 0.52 (0.41-0.67), 0.44 (0.37-0.53), 0.54 (0.45-0.66), and 0.86 (0.64-1.14) for all-cause, CVD, respiratory, and cancer mortality. A higher behavioral or medical score was independently associated with lower all-cause and CVD mortality among the total population and populations with different levels of behavioral or medical health equally, and no interaction was observed. Conclusions: ICH was associated with lower all-cause, CVD, and respiratory mortality among Chinese adults. Both behavioral and medical health should be improved to prevent premature deaths.
基金This research was financially supported by the National Natural Science Foundation of China(No.21402116,21502111,21572126,22001161)the Key Science Research of Education Committee in Henan Province(no.21A150044,22A150051)Shangqiu Normal University(Program of Ecological Conservation and High-quality Development of the Old Course of Yellow River,no.2021KYFZ06).
文摘We developed for the first time an unprecedented domino reaction of sulfonyl oximonitriles with secondary amines to streamline the synthesis of N-sulfonylformamidines in decent to high yields under mild reaction conditions.In addition,scale-up experiments and late-stage functionalization of drugs were also performed.Preliminary studies indicate that the loss of a cyano-/benzyloxy-group and a sulfonyl migration process are involved in this reaction.
