The quantum search on the graph is a very important topic.In this work,we develop a theoretic method on searching of single vertex on the graph[Phys.Rev.Lett.114110503(2015)],and systematically study the search of man...The quantum search on the graph is a very important topic.In this work,we develop a theoretic method on searching of single vertex on the graph[Phys.Rev.Lett.114110503(2015)],and systematically study the search of many vertices on one low-connectivity graph,the joined complete graph.Our results reveal that,with the optimal jumping rate obtained from the theoretical method,we can find such target vertices at the time O(√N),where N is the number of total vertices.Therefore,the search of many vertices on the joined complete graph possessing quantum advantage has been achieved.展开更多
The concept of joined-wing aircraft with nonplanar wings as conceived and patented by Wolkovitch is attractive due to various advantages such as light weight, high stiffness, low induced drag, high trimmed CLmax, redu...The concept of joined-wing aircraft with nonplanar wings as conceived and patented by Wolkovitch is attractive due to various advantages such as light weight, high stiffness, low induced drag, high trimmed CLmax, reduced wetted area and parasite drag and good stability and control, which have been supported by independent analyses, design studies and wind tunnel tests. With such foreseen advantages, the present work is carried out to design joined-wing business-jet aircraft and study and investigate its advantages and benefits as compared to the current available conventional business jet of similar size, passenger and payload capacity. In particular, the work searches for a conceptual design of joined-wing configured business-jet aircraft that possesses more superior characteristics and better aerodynamic performance in terms of increased lift and reduced drag, and lighter than the conventional business jet of similar size. Another significant objective of this work is to prove that the added rigidity possessed by the joined wing configuration can contribute to weight reduction.展开更多
On Aug. 25, China National Offshore Oil Corporation （CNOOC） and WorleyParsons, a world famous project construction company, signed an agreement for jointly setting up Huizhou Refinery Project Construction Team in Be...On Aug. 25, China National Offshore Oil Corporation （CNOOC） and WorleyParsons, a world famous project construction company, signed an agreement for jointly setting up Huizhou Refinery Project Construction Team in Beijing KEMPINSKI Hotel. Zheng Changbo, assistant president of CNOOC, Dong Xiaoli, general manager of Huizhou Refinery Project Team, and Lynn C. Fister, deputy general manager of WorleyParsons attended the signing ceremony.展开更多
Layered double hydroxide(LDH)conversion coatings loaded with corrosion inhibitors were suggested for the surface treatment of the aluminum alloy 2024-T3,prior to friction spot joining with carbon-fiber reinforced poly...Layered double hydroxide(LDH)conversion coatings loaded with corrosion inhibitors were suggested for the surface treatment of the aluminum alloy 2024-T3,prior to friction spot joining with carbon-fiber reinforced polyphenylene sulfide(AA2024-T3/CF-PPS).Vanadate was used as a model corrosion inhibitor.Lap shear testing method revealed an increase of approx.20%of the joint’s adhesion performance when treated with LDH and before exposure to salt spray.The evaluation of the joints after exposure to salt spray demonstrated a significant difference in the corrosion behavior of the joints when the AA2024-T3 is treated with LDH loaded with nitrate and vanadate species.The LDH intercalated with nitrate revealed a clear improvement in the mechanical and corrosion resistance performance of the joints,even after 6 weeks of salt spray.However,the LDH intercalated with vanadate failed in providing protection against corrosion as well as preserving the mechanical properties of the joints.The effect of the galvanic corrosion was further investigated by zero resistance ammeter(ZRA)measurements as well as localized scanning vibrating electrode technique(SVET).展开更多
A new testing methodology was developed to quantitively study galvanic corrosion of AZ31B and thermoset carbon-fiber–reinforced polymer spot-joined by a friction self-piercing riveting process.Pre-defined areas of AZ...A new testing methodology was developed to quantitively study galvanic corrosion of AZ31B and thermoset carbon-fiber–reinforced polymer spot-joined by a friction self-piercing riveting process.Pre-defined areas of AZ31B in the joint were exposed in 0.1 M NaCl solution over time.Massive galvanic corrosion of AZ31B was observed as exposure time increased.The measured volume loss was converted into corrosion current that was at least 48 times greater than the corrosion current of AZ31B without galvanic coupling.Ninety percent of the mechanical joint integrity was retained for corroded F-SPR joints to 200 h and then decreased because of the massive volume loss of AZ31B。展开更多
Joints between sintered silicon carbide （SSiC） were produced using a polysiloxane silicon resin YR3370 （GE Toshiba Silicones） as joining material. Samples were heat treated in a 99.99% nitrogen flux at temperature...Joints between sintered silicon carbide （SSiC） were produced using a polysiloxane silicon resin YR3370 （GE Toshiba Silicones） as joining material. Samples were heat treated in a 99.99% nitrogen flux at temperatures ranging from 1 100 ℃ to 1 300 ℃. Three point bending strength of the joint reached the maximum of 179 MPa as joined at 1 200℃. The joining layer is continuous, homogeneous and densified and has a thickness of 2 μm -5μm. The joining mechanism is that the amorphous silicon oxycarbide （SixOyCz） ceramic pyrolyzed from silicon resin YR3370 acts as an inorganic adhesive to SSiC substrate, which means the formation of the continuous Si-C bond structure between SixOyCz structure and SSiC substrate. Life prediction of the ceramic joint can be realized through the measurement of the critical time of the joint after the cyclic loading test.展开更多
Silicon nitride composite is joined to itself by heating interlayer of Y2 O3 -AL2O3 -SiO2 mixtures above their liquidus temperatures in flowing nitrogen. The joined specimens are tested in four point flexure from room...Silicon nitride composite is joined to itself by heating interlayer of Y2 O3 -AL2O3 -SiO2 mixtures above their liquidus temperatures in flowing nitrogen. The joined specimens are tested in four point flexure from room temperature to 1373 K. The interface microstruclure and fractured surfaces after testing are observed and analyzed by SEM, EPMA and XRD respectively. The results show that F2 O3 -A12 O3 -SiO2 glass reacts with Si3 N4 at interface, forming the Si3 N4/Si2 N2 O( Y-AlrSi-O-N glass/ Y-Al- Si-O glass gradient interface. With the increase of bonding temperature and holding time, the joint strength first increases, reaching a peak, and then decreases . According to interfacial analyses , the bonding strength depends on joint thickness .展开更多
In the context of electromobility,ensuring the leak tightness of assemblies is of paramount importance,particularly in bat-tery housings.Current battery housings,often featuring base assemblies crafted from extruded a...In the context of electromobility,ensuring the leak tightness of assemblies is of paramount importance,particularly in bat-tery housings.Current battery housings,often featuring base assemblies crafted from extruded aluminum profiles,address the challenge of leak tightness at joints through methods like friction stir welding,a process known for its time and cost intensiveness.The aim of this study is to develop and implement a new type of extruded profile concept to produce tight base assemblies for battery housings by a longitudinal mechanical single stroke joining process.The geometry,the process and the properties of the aluminum profiles are investigated to get a joint that meets the tightness requirements and achieve high load-bearing capacities in agreement with the high homologation requirements set to vehicles with high-voltage systems.The joint is formed by means of a single stage press stroke,which eliminates the need for complex tool designs that are neces-sary for continuous joining(roll joining).Flat steel contact surfaces are used as joining tools.To evaluate the joint quality,force curves from the joining process are analyzed and the resulting joint geometries are assessed using micrographs.The resulting leak tightness of the linear joints is measured by a helium sniffer leak detector and the load-bearing capacities are investigated by shear lap and bending tests and fatigue strength test.The study also explores whether a difference in strength between the two joining partners has a positive effect on the joint properties.展开更多
Determining the crossing number of a given graph is NP-complete. The cycle of length m is denoted by Cm = v1v2…vmv1. G^((1))_(m) (m ≥ 5) is the graph obtained from Cm by adding two edges v1v3 and vlvl+2 (3 ≤ l ≤ m...Determining the crossing number of a given graph is NP-complete. The cycle of length m is denoted by Cm = v1v2…vmv1. G^((1))_(m) (m ≥ 5) is the graph obtained from Cm by adding two edges v1v3 and vlvl+2 (3 ≤ l ≤ m−2), G^((2))m (m ≥ 4) is the graph obtained from Cm by adding two edges v1v3 and v2v4. The famous Zarankiewicz’s conjecture on the crossing number of the complete bipartite graph Km,n states that cr(Km,n)=Z(m,n)=[m/2][m-1/2][n/2[n-1/2].Based on Zarankiewicz’s conjecture, a natural problem is to study the change in the crossingnumber of the graphs obtained from the complete bipartite graph by adding certain edge sets.If Zarankiewicz’s conjecture is true, this paper proves that cr(G^((1))_(m)+Kn)=Z(m,n)+2[n/2] and cr(G^((2))_(m)+Kn)=Z(m,n)+n.展开更多
Not many 17‑year‑old girls know how to join two pipes together or light the pilot light.These are skills I have learned over the past five years as an assistant to my plumber dad.This summer job demands an attitude of...Not many 17‑year‑old girls know how to join two pipes together or light the pilot light.These are skills I have learned over the past five years as an assistant to my plumber dad.This summer job demands an attitude of perseverance and grace that I frequently struggle to adopt.Each humid morning,my dad and I drag awkward and heavy toolboxes into people's dark and damp basements where I usually get lost in mazes of storage boxes.Nevertheless,I stick to it.I am the plumber's daughter and helper.展开更多
Chromosomal DNA double-strand breaks(DSBs)are often generated in the genome of all living organisms.To combat DNA damage,organisms have evolved several DSB repair mechanisms,with nonhomologous end-joining(NHEJ)and hom...Chromosomal DNA double-strand breaks(DSBs)are often generated in the genome of all living organisms.To combat DNA damage,organisms have evolved several DSB repair mechanisms,with nonhomologous end-joining(NHEJ)and homologous recombination(HR)being the two most prominent.Although two major pathways have been extensively studied in Arabidopsis,rice and other mammals,the exact functions and differences between the two DSB repair pathways in maize still remain less well understood.Here,we characterized mre11a and rad50,mutants of HR pathway patterns,which showed drastic degradation of the typically persistent embryo and endosperm during kernel development.Loss of MRE11 or RAD50 function led to chromosomal fragments and chromosomal bridges in anaphase.While we also reported that the NHEJ pathway patterns,KU70 and KU80 are associated with developmental growth and genome stability.ku70 and ku80 both displayed an obvious dwarf phenotype.Cytological analysis of the mutants revealed extensive chromosome fragmentation in metaphase and subsequent stages.Loss of KU70/80 function upregulated the expression of genes involved in cell cycle progression and nuclear division.These results provide insights into how NHEJ and HR are mechanistically executed during different plant developmental periods and highlight a competitive and complementary relationship between the NHEJ and HR pathways for DNA double-strand break repair in maize.展开更多
The development and application of large Die⁃Casting Al Alloy(DCAA)parts and Thermo⁃Formed Steel Sheets(TFSS)in Body⁃in⁃White(BIW)have created higher demands for the joining technology of high⁃strength steel/Al dissim...The development and application of large Die⁃Casting Al Alloy(DCAA)parts and Thermo⁃Formed Steel Sheets(TFSS)in Body⁃in⁃White(BIW)have created higher demands for the joining technology of high⁃strength steel/Al dissimilar materials.As an emerging technology,Flush Self⁃Piercing Riveting(FSPR)is still in the experimental phase and undergoing small batch equipment verification.This paper focuses on the joining methods for DCAA and TFSS in BIW,investigating the joining mechanisms,technical features,and forming principles of FSPR for steel/Al dissimilar materials with two⁃layer or three⁃layer plate combinations.Considering the TL4225/C611/CR5 sheet combination as a subject,the forming mechanism of high⁃quality joints was studied,and a physical and mathematical model was established to depict the relationship between the filling amount of the arc⁃gap and die dimensions,as well as the extrusion amount.This model effectively illustrates the relationship between the filling amount of the flowing metal in the arc⁃gap and critical parameters,such as die dimensions and feeding amounts.By simplifying the process of selecting joining parameters,it significantly reduces both the time and experimental workload associated with parameter selection.This provides a technical foundation for the application of DAAA and TFSS parts in BIW,enabling the rapid choice of appropriate joining parameters to meet the requirements for obtaining high⁃quality joints.The model can be effectively utilized to investigate the relationships between key parameters,including arc⁃gap radius,plate thickness,rivet arc radius,nail head radius,groove width,and feeding amount,while keeping other parameters constant.This approach provides a theoretical foundation for the design of Friction Stir Processing(FSP)joints and aids in the selection of optimal parameters.展开更多
Editor’s notes: Now, the E.B of CHINA AUTO has been moved to Beijing Operations of CATARC (also named Beijing CATARC Automotive Technology Development Co., Ltd.). With the purpose of giving you further information on...Editor’s notes: Now, the E.B of CHINA AUTO has been moved to Beijing Operations of CATARC (also named Beijing CATARC Automotive Technology Development Co., Ltd.). With the purpose of giving you further information on CATARC and its Beijing branch, and for more convenience on concerned business now and then, we show you their brief introduction. Hope CATARC could act as a bridge of automotive industry both inside and outside.展开更多
BORN to a poor farmer’s family at Yangxi Village, Yeping Town, Ruijin County (today’s Ruijin City) of Jiangxi Province in 1914, I was sent to the Lius to be a child daughter-in-law. The Lius were too poor to support...BORN to a poor farmer’s family at Yangxi Village, Yeping Town, Ruijin County (today’s Ruijin City) of Jiangxi Province in 1914, I was sent to the Lius to be a child daughter-in-law. The Lius were too poor to support themselves. They had nothing but two sons. Worried about not having enough money to purchase a daughter-in-law in the future, the family accepted me as a child daughter-in-law-to-be. I was told by my elders that when I was three years old, I went with my father-in-law to beg. On the way, I was bitten by a rich family’s dog, causing my mother-in-law to burst into tears. My father-in-law died before long, leaving his wife, two sons and I with nothing to live on. With an uncle-in-law展开更多
Joining is a crucial process for the production of complex-shaped advanced engineering materials.Deep understanding of ceramic–metal interfaces during joining or following heat-treatment steps is therefore of importa...Joining is a crucial process for the production of complex-shaped advanced engineering materials.Deep understanding of ceramic–metal interfaces during joining or following heat-treatment steps is therefore of important concern in designing the new systems.Capacitor discharge joining(CDJ)method was firstly carried out to compose the ceramic–metal joint material by silicon nitride(Si3N4)–titanium(Ti)constituents.Afterwards,heat treatment was performed on the Si3N4-Ti joints in air atmosphere at 1000℃temperature to reveal the interface reactions and phases.Reaction layer that occurred between the Si3N4 and Ti interfaces and new phase formations were examined by transmission electron microscopy(TEM)-based various imaging and chemical analysis techniques.Electron transparent samples for TEM characterization were prepared by focused ion beam(FIB)milling and lifting method.Based on the detailed TEM results,Si and N diffusion arising from the Si3N4 ceramic was observed towards Ti metal foil side and further interacted with Ti atoms.The upshot of current diffusion was that Ti3N2 reaction layer with 50 nm thickness was formed at the interface while titanium silicon nitride(Ti6Si3N)matrix phase including dendritic-shaped Ti2 N grains occurred in the Ti interlayer.It is believed that our TEM-based microscopy results not only provide the knowledge on ceramic–metal joint materials by CDJ method,but also contribute new insights on the development of various new joint systems.展开更多
Refill friction stir spot welding(RFSSW)provides a novel method to join similar and/or dissimilar metallic materials without a key-hole in the center of the joint.Having the key-hole free characterization,the similar/...Refill friction stir spot welding(RFSSW)provides a novel method to join similar and/or dissimilar metallic materials without a key-hole in the center of the joint.Having the key-hole free characterization,the similar/dissimilar RFSSW joint exhibits remarkable and endurable characteristics,including high shear strength,long fatigue life,and strong corrosion resistance.In the meanwhile,as the key-hole free joint has different microstructures compared with conventional friction stir spot welding,thus the RFSSW joint shall possess different shear and fatigue fracture mechanisms,which needs further investigation.To explore the underlying failure mechanism,the similar/dissimilar metallic material joining parameters and pre-treatment,mechanical properties,as well as fracture mechanisms under this novel technology will be discussed.In details,the welding tool design,welding parameters setting,and the influence of processing on the lap shear and fatigue properties,as well as the corrosion resistance will be mainly discussed.Moreover,the roadmap of RFFSW is also discussed.展开更多
Dr.Xuanhe Zhao is a professor of mechanical engineering and civil and environmental engineering at Massachusetts Institute of Technology(MIT).Before joining MIT,he was an assistant professor in the Department of Mecha...Dr.Xuanhe Zhao is a professor of mechanical engineering and civil and environmental engineering at Massachusetts Institute of Technology(MIT).Before joining MIT,he was an assistant professor in the Department of Mechanical Engineering and Materials Science at Duke University.He earned his PhD at Harvard University in 2009.展开更多
基金the National Key R&D Program of China(Grant No.2017YFA0303800)the National Natural Science Foundation of China(Grant Nos.91850205 and 11974046)。
文摘The quantum search on the graph is a very important topic.In this work,we develop a theoretic method on searching of single vertex on the graph[Phys.Rev.Lett.114110503(2015)],and systematically study the search of many vertices on one low-connectivity graph,the joined complete graph.Our results reveal that,with the optimal jumping rate obtained from the theoretical method,we can find such target vertices at the time O(√N),where N is the number of total vertices.Therefore,the search of many vertices on the joined complete graph possessing quantum advantage has been achieved.
文摘The concept of joined-wing aircraft with nonplanar wings as conceived and patented by Wolkovitch is attractive due to various advantages such as light weight, high stiffness, low induced drag, high trimmed CLmax, reduced wetted area and parasite drag and good stability and control, which have been supported by independent analyses, design studies and wind tunnel tests. With such foreseen advantages, the present work is carried out to design joined-wing business-jet aircraft and study and investigate its advantages and benefits as compared to the current available conventional business jet of similar size, passenger and payload capacity. In particular, the work searches for a conceptual design of joined-wing configured business-jet aircraft that possesses more superior characteristics and better aerodynamic performance in terms of increased lift and reduced drag, and lighter than the conventional business jet of similar size. Another significant objective of this work is to prove that the added rigidity possessed by the joined wing configuration can contribute to weight reduction.
文摘On Aug. 25, China National Offshore Oil Corporation （CNOOC） and WorleyParsons, a world famous project construction company, signed an agreement for jointly setting up Huizhou Refinery Project Construction Team in Beijing KEMPINSKI Hotel. Zheng Changbo, assistant president of CNOOC, Dong Xiaoli, general manager of Huizhou Refinery Project Team, and Lynn C. Fister, deputy general manager of WorleyParsons attended the signing ceremony.
基金supported by the European FP7 project“PROAIR”(No.PIAPP-GA-2013-612415)the Horizon 2020 project“MULTISURF”(Marie Sklodowska-Curie grant agreement No 645676)+3 种基金the DAAD financial support in the form of an International Travel Grant,which enabled her to attend the International Conference on Surface Modification Technologies 33(SMT-33)the support of the National Council for Scientific and Technological Development(CNPq Brazil,Process 200694/2015-4)the financial support from the Austrian aviation program“TAKE-OFF”from the Austrian Ministry for Climate Action,Environment,Energy,Mobility,Innovation and Technology,BMK。
文摘Layered double hydroxide(LDH)conversion coatings loaded with corrosion inhibitors were suggested for the surface treatment of the aluminum alloy 2024-T3,prior to friction spot joining with carbon-fiber reinforced polyphenylene sulfide(AA2024-T3/CF-PPS).Vanadate was used as a model corrosion inhibitor.Lap shear testing method revealed an increase of approx.20%of the joint’s adhesion performance when treated with LDH and before exposure to salt spray.The evaluation of the joints after exposure to salt spray demonstrated a significant difference in the corrosion behavior of the joints when the AA2024-T3 is treated with LDH loaded with nitrate and vanadate species.The LDH intercalated with nitrate revealed a clear improvement in the mechanical and corrosion resistance performance of the joints,even after 6 weeks of salt spray.However,the LDH intercalated with vanadate failed in providing protection against corrosion as well as preserving the mechanical properties of the joints.The effect of the galvanic corrosion was further investigated by zero resistance ammeter(ZRA)measurements as well as localized scanning vibrating electrode technique(SVET).
基金financially sponsored by the US Department Energy Vehicle Technologies Office, as part of the Joining Core Programmanaged by UT-Battelle LLC for the US Department of Energy under Contract DE-AC05-00OR22725。
文摘A new testing methodology was developed to quantitively study galvanic corrosion of AZ31B and thermoset carbon-fiber–reinforced polymer spot-joined by a friction self-piercing riveting process.Pre-defined areas of AZ31B in the joint were exposed in 0.1 M NaCl solution over time.Massive galvanic corrosion of AZ31B was observed as exposure time increased.The measured volume loss was converted into corrosion current that was at least 48 times greater than the corrosion current of AZ31B without galvanic coupling.Ninety percent of the mechanical joint integrity was retained for corroded F-SPR joints to 200 h and then decreased because of the massive volume loss of AZ31B。
基金National Key Fundamental R&D Plan (2004CB217808)National Natural Science Foundation of China (20271037)
文摘Joints between sintered silicon carbide （SSiC） were produced using a polysiloxane silicon resin YR3370 （GE Toshiba Silicones） as joining material. Samples were heat treated in a 99.99% nitrogen flux at temperatures ranging from 1 100 ℃ to 1 300 ℃. Three point bending strength of the joint reached the maximum of 179 MPa as joined at 1 200℃. The joining layer is continuous, homogeneous and densified and has a thickness of 2 μm -5μm. The joining mechanism is that the amorphous silicon oxycarbide （SixOyCz） ceramic pyrolyzed from silicon resin YR3370 acts as an inorganic adhesive to SSiC substrate, which means the formation of the continuous Si-C bond structure between SixOyCz structure and SSiC substrate. Life prediction of the ceramic joint can be realized through the measurement of the critical time of the joint after the cyclic loading test.
文摘Silicon nitride composite is joined to itself by heating interlayer of Y2 O3 -AL2O3 -SiO2 mixtures above their liquidus temperatures in flowing nitrogen. The joined specimens are tested in four point flexure from room temperature to 1373 K. The interface microstruclure and fractured surfaces after testing are observed and analyzed by SEM, EPMA and XRD respectively. The results show that F2 O3 -A12 O3 -SiO2 glass reacts with Si3 N4 at interface, forming the Si3 N4/Si2 N2 O( Y-AlrSi-O-N glass/ Y-Al- Si-O glass gradient interface. With the increase of bonding temperature and holding time, the joint strength first increases, reaching a peak, and then decreases . According to interfacial analyses , the bonding strength depends on joint thickness .
文摘In the context of electromobility,ensuring the leak tightness of assemblies is of paramount importance,particularly in bat-tery housings.Current battery housings,often featuring base assemblies crafted from extruded aluminum profiles,address the challenge of leak tightness at joints through methods like friction stir welding,a process known for its time and cost intensiveness.The aim of this study is to develop and implement a new type of extruded profile concept to produce tight base assemblies for battery housings by a longitudinal mechanical single stroke joining process.The geometry,the process and the properties of the aluminum profiles are investigated to get a joint that meets the tightness requirements and achieve high load-bearing capacities in agreement with the high homologation requirements set to vehicles with high-voltage systems.The joint is formed by means of a single stage press stroke,which eliminates the need for complex tool designs that are neces-sary for continuous joining(roll joining).Flat steel contact surfaces are used as joining tools.To evaluate the joint quality,force curves from the joining process are analyzed and the resulting joint geometries are assessed using micrographs.The resulting leak tightness of the linear joints is measured by a helium sniffer leak detector and the load-bearing capacities are investigated by shear lap and bending tests and fatigue strength test.The study also explores whether a difference in strength between the two joining partners has a positive effect on the joint properties.
基金Supported by Changsha Natural Science Foundation(No.kq2208001)the Key Project Funded by Hunan Provincial Department of Education(No.21A0590)。
文摘Determining the crossing number of a given graph is NP-complete. The cycle of length m is denoted by Cm = v1v2…vmv1. G^((1))_(m) (m ≥ 5) is the graph obtained from Cm by adding two edges v1v3 and vlvl+2 (3 ≤ l ≤ m−2), G^((2))m (m ≥ 4) is the graph obtained from Cm by adding two edges v1v3 and v2v4. The famous Zarankiewicz’s conjecture on the crossing number of the complete bipartite graph Km,n states that cr(Km,n)=Z(m,n)=[m/2][m-1/2][n/2[n-1/2].Based on Zarankiewicz’s conjecture, a natural problem is to study the change in the crossingnumber of the graphs obtained from the complete bipartite graph by adding certain edge sets.If Zarankiewicz’s conjecture is true, this paper proves that cr(G^((1))_(m)+Kn)=Z(m,n)+2[n/2] and cr(G^((2))_(m)+Kn)=Z(m,n)+n.
文摘Not many 17‑year‑old girls know how to join two pipes together or light the pilot light.These are skills I have learned over the past five years as an assistant to my plumber dad.This summer job demands an attitude of perseverance and grace that I frequently struggle to adopt.Each humid morning,my dad and I drag awkward and heavy toolboxes into people's dark and damp basements where I usually get lost in mazes of storage boxes.Nevertheless,I stick to it.I am the plumber's daughter and helper.
基金supported by the National Natural Science Foundation of China(32372116)to Yan He.
文摘Chromosomal DNA double-strand breaks(DSBs)are often generated in the genome of all living organisms.To combat DNA damage,organisms have evolved several DSB repair mechanisms,with nonhomologous end-joining(NHEJ)and homologous recombination(HR)being the two most prominent.Although two major pathways have been extensively studied in Arabidopsis,rice and other mammals,the exact functions and differences between the two DSB repair pathways in maize still remain less well understood.Here,we characterized mre11a and rad50,mutants of HR pathway patterns,which showed drastic degradation of the typically persistent embryo and endosperm during kernel development.Loss of MRE11 or RAD50 function led to chromosomal fragments and chromosomal bridges in anaphase.While we also reported that the NHEJ pathway patterns,KU70 and KU80 are associated with developmental growth and genome stability.ku70 and ku80 both displayed an obvious dwarf phenotype.Cytological analysis of the mutants revealed extensive chromosome fragmentation in metaphase and subsequent stages.Loss of KU70/80 function upregulated the expression of genes involved in cell cycle progression and nuclear division.These results provide insights into how NHEJ and HR are mechanistically executed during different plant developmental periods and highlight a competitive and complementary relationship between the NHEJ and HR pathways for DNA double-strand break repair in maize.
文摘The development and application of large Die⁃Casting Al Alloy(DCAA)parts and Thermo⁃Formed Steel Sheets(TFSS)in Body⁃in⁃White(BIW)have created higher demands for the joining technology of high⁃strength steel/Al dissimilar materials.As an emerging technology,Flush Self⁃Piercing Riveting(FSPR)is still in the experimental phase and undergoing small batch equipment verification.This paper focuses on the joining methods for DCAA and TFSS in BIW,investigating the joining mechanisms,technical features,and forming principles of FSPR for steel/Al dissimilar materials with two⁃layer or three⁃layer plate combinations.Considering the TL4225/C611/CR5 sheet combination as a subject,the forming mechanism of high⁃quality joints was studied,and a physical and mathematical model was established to depict the relationship between the filling amount of the arc⁃gap and die dimensions,as well as the extrusion amount.This model effectively illustrates the relationship between the filling amount of the flowing metal in the arc⁃gap and critical parameters,such as die dimensions and feeding amounts.By simplifying the process of selecting joining parameters,it significantly reduces both the time and experimental workload associated with parameter selection.This provides a technical foundation for the application of DAAA and TFSS parts in BIW,enabling the rapid choice of appropriate joining parameters to meet the requirements for obtaining high⁃quality joints.The model can be effectively utilized to investigate the relationships between key parameters,including arc⁃gap radius,plate thickness,rivet arc radius,nail head radius,groove width,and feeding amount,while keeping other parameters constant.This approach provides a theoretical foundation for the design of Friction Stir Processing(FSP)joints and aids in the selection of optimal parameters.
文摘Editor’s notes: Now, the E.B of CHINA AUTO has been moved to Beijing Operations of CATARC (also named Beijing CATARC Automotive Technology Development Co., Ltd.). With the purpose of giving you further information on CATARC and its Beijing branch, and for more convenience on concerned business now and then, we show you their brief introduction. Hope CATARC could act as a bridge of automotive industry both inside and outside.
文摘BORN to a poor farmer’s family at Yangxi Village, Yeping Town, Ruijin County (today’s Ruijin City) of Jiangxi Province in 1914, I was sent to the Lius to be a child daughter-in-law. The Lius were too poor to support themselves. They had nothing but two sons. Worried about not having enough money to purchase a daughter-in-law in the future, the family accepted me as a child daughter-in-law-to-be. I was told by my elders that when I was three years old, I went with my father-in-law to beg. On the way, I was bitten by a rich family’s dog, causing my mother-in-law to burst into tears. My father-in-law died before long, leaving his wife, two sons and I with nothing to live on. With an uncle-in-law
基金Anadolu University(Eskisehir,Turkey)for financial support by BAP-030217 project.
文摘Joining is a crucial process for the production of complex-shaped advanced engineering materials.Deep understanding of ceramic–metal interfaces during joining or following heat-treatment steps is therefore of important concern in designing the new systems.Capacitor discharge joining(CDJ)method was firstly carried out to compose the ceramic–metal joint material by silicon nitride(Si3N4)–titanium(Ti)constituents.Afterwards,heat treatment was performed on the Si3N4-Ti joints in air atmosphere at 1000℃temperature to reveal the interface reactions and phases.Reaction layer that occurred between the Si3N4 and Ti interfaces and new phase formations were examined by transmission electron microscopy(TEM)-based various imaging and chemical analysis techniques.Electron transparent samples for TEM characterization were prepared by focused ion beam(FIB)milling and lifting method.Based on the detailed TEM results,Si and N diffusion arising from the Si3N4 ceramic was observed towards Ti metal foil side and further interacted with Ti atoms.The upshot of current diffusion was that Ti3N2 reaction layer with 50 nm thickness was formed at the interface while titanium silicon nitride(Ti6Si3N)matrix phase including dendritic-shaped Ti2 N grains occurred in the Ti interlayer.It is believed that our TEM-based microscopy results not only provide the knowledge on ceramic–metal joint materials by CDJ method,but also contribute new insights on the development of various new joint systems.
基金This work was supported by International Science and Technology Cooperation Project of Guangdong Province(Grant No.2022A0505050054)Innovation and Technology Fund(ITF)(Grant No.ITP/021/19AP)National Natural Science Foundation of China(Grant No.51905112).
文摘Refill friction stir spot welding(RFSSW)provides a novel method to join similar and/or dissimilar metallic materials without a key-hole in the center of the joint.Having the key-hole free characterization,the similar/dissimilar RFSSW joint exhibits remarkable and endurable characteristics,including high shear strength,long fatigue life,and strong corrosion resistance.In the meanwhile,as the key-hole free joint has different microstructures compared with conventional friction stir spot welding,thus the RFSSW joint shall possess different shear and fatigue fracture mechanisms,which needs further investigation.To explore the underlying failure mechanism,the similar/dissimilar metallic material joining parameters and pre-treatment,mechanical properties,as well as fracture mechanisms under this novel technology will be discussed.In details,the welding tool design,welding parameters setting,and the influence of processing on the lap shear and fatigue properties,as well as the corrosion resistance will be mainly discussed.Moreover,the roadmap of RFFSW is also discussed.
文摘Dr.Xuanhe Zhao is a professor of mechanical engineering and civil and environmental engineering at Massachusetts Institute of Technology(MIT).Before joining MIT,he was an assistant professor in the Department of Mechanical Engineering and Materials Science at Duke University.He earned his PhD at Harvard University in 2009.
