The magnetically constricted arc technique was implemented to mitigate the heat input related metallurgical problems in Gas Tungsten Arc Welding(GTAW)of Inconel 718 alloy particularly Nb segregation and subsequent lav...The magnetically constricted arc technique was implemented to mitigate the heat input related metallurgical problems in Gas Tungsten Arc Welding(GTAW)of Inconel 718 alloy particularly Nb segregation and subsequent laves phase evolution in fusion zone.This paper reports the direct effect of magnetically constricted arc traverse speed(MCATS)on bead profile,tensile properties and microstructural evolution of Inconel 718 alloy sheets joined by Gas Tungsten Constricted Arc Welding(GTCAW)process.The mechanism amenable for the microstructural modification and corresponding influence on the tensile properties of joints is investigated both in qualitative and quantitative manner related to the mechanics of arc constriction and pulsing.It is correlated to the solidification conditions during welding.The relationship between MCATS and Arc Constriction Current(ACC)was derived.Its interaction effect on the magnetic arc constriction and joint performance was analysed.Results showed that the joints fabricated using CATS of 70 mm/min exhibited superior tensile properties(98.39% of base metal strength with 31.50% elongation).It is attributed to the grain refinement in fusion zone microstructure leading to the evolution of finer,discrete laves phase in interdendritic areas.展开更多
This paper investigates the effect of porosity on active damping of geometrically nonlinear vibrations(GNLV)of the magneto-electro-elastic(MEE)functionally graded(FG)plates incorporated with active treatment constrict...This paper investigates the effect of porosity on active damping of geometrically nonlinear vibrations(GNLV)of the magneto-electro-elastic(MEE)functionally graded(FG)plates incorporated with active treatment constricted layer damping(ATCLD)patches.The perpendicularly/slanted reinforced 1-3 piezoelectric composite(1-3 PZC)constricting layer.The constricted viscoelastic layer of the ATCLD is modeled in the time-domain using Golla-Hughes-Mc Tavish(GHM)technique.Different types of porosity distribution in the porous magneto-electro-elastic functionally graded PMEE-FG plate graded in the thickness direction.Considering the coupling effects among elasticity,electrical,and magnetic fields,a three-dimensional finite element(FE)model for the smart PMEE-FG plate is obtained by incorporating the theory of layer-wise shear deformation.The geometric nonlinearity adopts the von K arm an principle.The study presents the effects of a variant of a power-law index,porosity index,the material gradation,three types of porosity distribution,boundary conditions,and the piezoelectric fiber’s orientation angle on the control of GNLV of the PMEE-FG plates.The results reveal that the FG substrate layers’porosity significantly impacts the nonlinear behavior and damping performance of the PMEE-FG plates.展开更多
OBJECTIVE The objective of this study was to characterize the neurotransmitter systems that cause constriction of murine airways.METHODS Murine precision cut lung slices(PCLS)and trachea were prepared,placed into perf...OBJECTIVE The objective of this study was to characterize the neurotransmitter systems that cause constriction of murine airways.METHODS Murine precision cut lung slices(PCLS)and trachea were prepared,placed into perfusion chambers equipped with platinum electrodes and stimulated transmurally(1.0 ms,50 V,0.1-30 Hz).To measure PCLS constriction,changes in airway luminal area in response to electric field stimulation(EFS)were captured as video images quantified using Image J software.For trachea,changes in isometric tension were recorded using Grass force transducers.Frequency response curves were generated in the absence and the presence of the inhibitors magnesium,atropine and capsaicin and responses analyzed and compared using a student's t-test(P<0.05).RESULTS EFS caused airway constriction in a frequency-dependent manner that was best fit by a biphasic curve.Neuron-specific stimulation was verified by Mg^(2+) blockade.Maximum airway constriction to 30 Hz EFS in PCLS was(51.8±3.0)%while tracheal constriction averaged(551±80)mg.Interestingly,in PCLS the muscarinic receptor antagonist atropine(10μmol·L^(-1))blocked(99.5±7.2)%of EFS induced constriction at 1 Hz,but only blocked(23.3±3.8)%of EFS induced constriction at 30 Hz and eliminated the first phase but not the second phase of the biphasic EFS response.Treatment with capsaicin to deplete sensory neurotransmitters significantly increased EFS constriction supporting the presence of sensory neurotransmitter systems in airways.CONCLUSION These data are consistent with parasympathetic constriction of airways by acetylcholine at lower EFS frequencies while higher frequencies release sensory dilator neurotransmitters.These data provide evidence for multiple nerve types innervating airways which may provide novel targets for treatment of lung disease.展开更多
基金funded by Indian Space Research Organization (ISRO) India. Project No. ISRO/RES/3/728/16e17
文摘The magnetically constricted arc technique was implemented to mitigate the heat input related metallurgical problems in Gas Tungsten Arc Welding(GTAW)of Inconel 718 alloy particularly Nb segregation and subsequent laves phase evolution in fusion zone.This paper reports the direct effect of magnetically constricted arc traverse speed(MCATS)on bead profile,tensile properties and microstructural evolution of Inconel 718 alloy sheets joined by Gas Tungsten Constricted Arc Welding(GTCAW)process.The mechanism amenable for the microstructural modification and corresponding influence on the tensile properties of joints is investigated both in qualitative and quantitative manner related to the mechanics of arc constriction and pulsing.It is correlated to the solidification conditions during welding.The relationship between MCATS and Arc Constriction Current(ACC)was derived.Its interaction effect on the magnetic arc constriction and joint performance was analysed.Results showed that the joints fabricated using CATS of 70 mm/min exhibited superior tensile properties(98.39% of base metal strength with 31.50% elongation).It is attributed to the grain refinement in fusion zone microstructure leading to the evolution of finer,discrete laves phase in interdendritic areas.
文摘This paper investigates the effect of porosity on active damping of geometrically nonlinear vibrations(GNLV)of the magneto-electro-elastic(MEE)functionally graded(FG)plates incorporated with active treatment constricted layer damping(ATCLD)patches.The perpendicularly/slanted reinforced 1-3 piezoelectric composite(1-3 PZC)constricting layer.The constricted viscoelastic layer of the ATCLD is modeled in the time-domain using Golla-Hughes-Mc Tavish(GHM)technique.Different types of porosity distribution in the porous magneto-electro-elastic functionally graded PMEE-FG plate graded in the thickness direction.Considering the coupling effects among elasticity,electrical,and magnetic fields,a three-dimensional finite element(FE)model for the smart PMEE-FG plate is obtained by incorporating the theory of layer-wise shear deformation.The geometric nonlinearity adopts the von K arm an principle.The study presents the effects of a variant of a power-law index,porosity index,the material gradation,three types of porosity distribution,boundary conditions,and the piezoelectric fiber’s orientation angle on the control of GNLV of the PMEE-FG plates.The results reveal that the FG substrate layers’porosity significantly impacts the nonlinear behavior and damping performance of the PMEE-FG plates.
文摘OBJECTIVE The objective of this study was to characterize the neurotransmitter systems that cause constriction of murine airways.METHODS Murine precision cut lung slices(PCLS)and trachea were prepared,placed into perfusion chambers equipped with platinum electrodes and stimulated transmurally(1.0 ms,50 V,0.1-30 Hz).To measure PCLS constriction,changes in airway luminal area in response to electric field stimulation(EFS)were captured as video images quantified using Image J software.For trachea,changes in isometric tension were recorded using Grass force transducers.Frequency response curves were generated in the absence and the presence of the inhibitors magnesium,atropine and capsaicin and responses analyzed and compared using a student's t-test(P<0.05).RESULTS EFS caused airway constriction in a frequency-dependent manner that was best fit by a biphasic curve.Neuron-specific stimulation was verified by Mg^(2+) blockade.Maximum airway constriction to 30 Hz EFS in PCLS was(51.8±3.0)%while tracheal constriction averaged(551±80)mg.Interestingly,in PCLS the muscarinic receptor antagonist atropine(10μmol·L^(-1))blocked(99.5±7.2)%of EFS induced constriction at 1 Hz,but only blocked(23.3±3.8)%of EFS induced constriction at 30 Hz and eliminated the first phase but not the second phase of the biphasic EFS response.Treatment with capsaicin to deplete sensory neurotransmitters significantly increased EFS constriction supporting the presence of sensory neurotransmitter systems in airways.CONCLUSION These data are consistent with parasympathetic constriction of airways by acetylcholine at lower EFS frequencies while higher frequencies release sensory dilator neurotransmitters.These data provide evidence for multiple nerve types innervating airways which may provide novel targets for treatment of lung disease.
