A 4 kW fiber laser was chosen to weld the new hot-rolled nano-scale precipitation-strengthened steel with a thickness of 4.5 mm. The effect of laser power, defocusing distance, and welding speed on the welded joint ap...A 4 kW fiber laser was chosen to weld the new hot-rolled nano-scale precipitation-strengthened steel with a thickness of 4.5 mm. The effect of laser power, defocusing distance, and welding speed on the welded joint appearance was examined, and the microstructure and mechanical properties on the typical butt joints were investigated. Results showed that increasing laser welding power may cause faster downward flow of molten metal to produce greater root humping. With the welding speed increasing, the average welding seam （WS） width decreased, and the average WS and heat-affected zone （HAZ） hardness increased. The microstructures of WS, fusion line, and coarse grain heat-affected zone were lath martensite, but the growth direction of the original austenite grain boundaries was significantly different. The microstructures of fine grain heat-affected zone were ferrite and martensite, and the microstructure of mixed grain heat- affected zone contained ferrite, massive M/A island, and a small amount of martensite. The micro-hardness values of WS, HAZ, and base metal （BM） were 358, 302, and 265 HV, respectively. The butt joint fracture at the BM far from the WS and the welded joint tensile strength are observed to follow proportional relationship with hardness.展开更多
The laser scanning system based on Simultaneous Localization and Mapping(SLAM)technology has the advantages of low cost,high precision and high efficiency.It has drawn wide attention in the field of surveying and mapp...The laser scanning system based on Simultaneous Localization and Mapping(SLAM)technology has the advantages of low cost,high precision and high efficiency.It has drawn wide attention in the field of surveying and mapping in recent years.Although real-time data acquisition can be achieved using SLAM technology,the precision of the data can’t be ensured,and inconsistency exists in the acquired point cloud.In order to improve the precision of the point cloud obtained by this kind of system,this paper presents a hierarchical point cloud global optimization algorithm.Firstly,the“point-to-plane”iterative closest point(ICP)algorithm is used to match the overlapping point clouds to form constraints between the trajectories of the scanning system.Then a pose graph is constructed to optimize the trajectory.Finally,the optimized trajectory is used to refine the point cloud.The computational efficiency is improved by decomposing the optimization process into two levels,i.e.local level and global level.The experimental results show that the RMSE of the distance between the corresponding points in overlapping areas is reduced by about 50%after optimization,and the internal inconsistency is effectively eliminated.展开更多
Alternaria alternata,a causal agent of leaf blights and spots on a wide range of hosts,has a high risk of developing resistance to fungicides.Procymidone,a dicarboximide fungicide(DCF),has been widely used in controll...Alternaria alternata,a causal agent of leaf blights and spots on a wide range of hosts,has a high risk of developing resistance to fungicides.Procymidone,a dicarboximide fungicide(DCF),has been widely used in controlling Alternaria leaf blights in China for decades.However,the resistance of A.alternata against DCFs has rarely been reported from crucifer plants.A total of 198 A.alternata isolates were collected from commercial fields of broccoli and cabbage during 2018-2019,and their sensitivities to procymidone were determined.Biochemical and molecular characteristics were subsequently compared between the high-level procymidone-resistant(Pro^(HR))and procymidone-sensitive(Pro^(S))isolates,and also between Pro^(HR)isolates from broccoli and cabbage.Compared with ProS isolates,the mycelial growth rate,sporulation capacity and virulence of most Pro^(HR)isolates were reduced;Pro^(HR)isolates displayed an increased sensitivity to osmotic stresses and a reduced sensitivity to sodium dodecyl sulfate(SDS);all Pro^(HR)isolates showed a reduced sensitivity to hydrogen peroxide(H_(2)O_(2))except for the isolate B102.Correlation analysis revealed a positive cross-resistance between procymidone and iprodione,or fludioxonil.When treated with 10μg/mL of procymidone,both mycelial intracellular glycerol accumulations(MIGAs)and relative expression of AaHK1 in Pro^(S) isolates were higher than those in Pro^(HR)isolates.Sequence alignment of AaHK1 from ten Pro^(HR)isolates demonstrated that five of them possessed a single-point mutation(P94A,V612L,E708K or Q924STOP),and four isolates had an insertion or a deletion in their coding regions.No significant difference in biochemical characteristics was observed among Pro^(HR)isolates from two different hosts,though mutations in AaHK1 of the cabbage-originated Pro^(HR)isolates were distinct from those of the broccoli-originated Pro^(HR)isolates.展开更多
Acute noncompressive nucleus pulposus(NP)extrusion has been widely described in veterinary medicine,especially in dogs and cats;however,caseshave rarely been reported in humans.We report a rare case of acute pain caus...Acute noncompressive nucleus pulposus(NP)extrusion has been widely described in veterinary medicine,especially in dogs and cats;however,caseshave rarely been reported in humans.We report a rare case of acute pain caused by a hydrated NP.Magnetic resonance imaging revealed an obvious hyperintense signal on T2-weighted images at the L5/S1 segments,while computed tomography imaging and radiography revealed amildly herniated discat the L4/5 level and slightlumbar spondylo listhesis at the L5/S1 segments.The operation was performed to confirm the presence of ared and swollen nerve root on the right side of the hydrated L5/S1 segment.The patient’s severe pain disappeared,and full recovery was achieved months after surgery.Thus,our case demonstrated a probable lumbar acute noncompressive NP extrusion in humans and reported associated symptoms and imaging characteristics.In such circumstances,surgical management is indicated and may be associated with a good outcome.展开更多
基金supported by the National Natural Science Foundation of China (Nos.51305285 and 51104110)the Basic Research Program of Jiangsu Province (Nos. BK20130315 and BK20130304)
文摘A 4 kW fiber laser was chosen to weld the new hot-rolled nano-scale precipitation-strengthened steel with a thickness of 4.5 mm. The effect of laser power, defocusing distance, and welding speed on the welded joint appearance was examined, and the microstructure and mechanical properties on the typical butt joints were investigated. Results showed that increasing laser welding power may cause faster downward flow of molten metal to produce greater root humping. With the welding speed increasing, the average welding seam （WS） width decreased, and the average WS and heat-affected zone （HAZ） hardness increased. The microstructures of WS, fusion line, and coarse grain heat-affected zone were lath martensite, but the growth direction of the original austenite grain boundaries was significantly different. The microstructures of fine grain heat-affected zone were ferrite and martensite, and the microstructure of mixed grain heat- affected zone contained ferrite, massive M/A island, and a small amount of martensite. The micro-hardness values of WS, HAZ, and base metal （BM） were 358, 302, and 265 HV, respectively. The butt joint fracture at the BM far from the WS and the welded joint tensile strength are observed to follow proportional relationship with hardness.
基金National Key Research Program of China(No.2017YFC0803801)。
文摘The laser scanning system based on Simultaneous Localization and Mapping(SLAM)technology has the advantages of low cost,high precision and high efficiency.It has drawn wide attention in the field of surveying and mapping in recent years.Although real-time data acquisition can be achieved using SLAM technology,the precision of the data can’t be ensured,and inconsistency exists in the acquired point cloud.In order to improve the precision of the point cloud obtained by this kind of system,this paper presents a hierarchical point cloud global optimization algorithm.Firstly,the“point-to-plane”iterative closest point(ICP)algorithm is used to match the overlapping point clouds to form constraints between the trajectories of the scanning system.Then a pose graph is constructed to optimize the trajectory.Finally,the optimized trajectory is used to refine the point cloud.The computational efficiency is improved by decomposing the optimization process into two levels,i.e.local level and global level.The experimental results show that the RMSE of the distance between the corresponding points in overlapping areas is reduced by about 50%after optimization,and the internal inconsistency is effectively eliminated.
基金supported by National Science Foundation of China(No.31801778&No.31672065)Chinese Key R&D Plan(2018YFD0201201,2016YED0201007&2018YFD0201000)Agricultural Science and Technology Projects of Jiangsu Province,China{PZCZ201715,CX[19]3003,BE2018378,BA2018039,&CX(18)2005}.
文摘Alternaria alternata,a causal agent of leaf blights and spots on a wide range of hosts,has a high risk of developing resistance to fungicides.Procymidone,a dicarboximide fungicide(DCF),has been widely used in controlling Alternaria leaf blights in China for decades.However,the resistance of A.alternata against DCFs has rarely been reported from crucifer plants.A total of 198 A.alternata isolates were collected from commercial fields of broccoli and cabbage during 2018-2019,and their sensitivities to procymidone were determined.Biochemical and molecular characteristics were subsequently compared between the high-level procymidone-resistant(Pro^(HR))and procymidone-sensitive(Pro^(S))isolates,and also between Pro^(HR)isolates from broccoli and cabbage.Compared with ProS isolates,the mycelial growth rate,sporulation capacity and virulence of most Pro^(HR)isolates were reduced;Pro^(HR)isolates displayed an increased sensitivity to osmotic stresses and a reduced sensitivity to sodium dodecyl sulfate(SDS);all Pro^(HR)isolates showed a reduced sensitivity to hydrogen peroxide(H_(2)O_(2))except for the isolate B102.Correlation analysis revealed a positive cross-resistance between procymidone and iprodione,or fludioxonil.When treated with 10μg/mL of procymidone,both mycelial intracellular glycerol accumulations(MIGAs)and relative expression of AaHK1 in Pro^(S) isolates were higher than those in Pro^(HR)isolates.Sequence alignment of AaHK1 from ten Pro^(HR)isolates demonstrated that five of them possessed a single-point mutation(P94A,V612L,E708K or Q924STOP),and four isolates had an insertion or a deletion in their coding regions.No significant difference in biochemical characteristics was observed among Pro^(HR)isolates from two different hosts,though mutations in AaHK1 of the cabbage-originated Pro^(HR)isolates were distinct from those of the broccoli-originated Pro^(HR)isolates.
文摘Acute noncompressive nucleus pulposus(NP)extrusion has been widely described in veterinary medicine,especially in dogs and cats;however,caseshave rarely been reported in humans.We report a rare case of acute pain caused by a hydrated NP.Magnetic resonance imaging revealed an obvious hyperintense signal on T2-weighted images at the L5/S1 segments,while computed tomography imaging and radiography revealed amildly herniated discat the L4/5 level and slightlumbar spondylo listhesis at the L5/S1 segments.The operation was performed to confirm the presence of ared and swollen nerve root on the right side of the hydrated L5/S1 segment.The patient’s severe pain disappeared,and full recovery was achieved months after surgery.Thus,our case demonstrated a probable lumbar acute noncompressive NP extrusion in humans and reported associated symptoms and imaging characteristics.In such circumstances,surgical management is indicated and may be associated with a good outcome.
