74 research outputs found
Apparent negative motion of vortex matter due to inhomogeneous pinning
We investigate the transport of vortices in superconductors with inhomgeneous pinning under a driving force. The inhomogeneity of pinning is simplified as strong-weak pinning regions. It is demonstrated that the interactions between the vortices captured by strong pinning potentials and the vortices in the weak pinning region cause absolute negative motion (ANM) of vortices: The vortices which are climbing toward the high barriers induced by the strong pinning with the help of driving force move toward the opposite direction of the force and back to their equilibrium positions in the weak pinning region as the force decreases or is withdrawn. Our simulations reveal that the hysteresis of ANM is determined by the competition between the speed of the negative motion which depends on the piining inhomogeneity in superconductors and the speed of the driving force. Under the conditions of either larger force scanning rate or higher pinning inhomogeneity, a marked ANM and a larger hysteretic speed-force loop could be observed. This indicates that the time window to observe the ANM should be chosen properly. Moreover, the V-1 characteristics of Ag-sheathed Bi=2223 tapes are measured, and experimental observations are qualitatively in agreement with the simulation
Isothermal Fatigue and Creep-Fatigue Interaction Behavior of Nickel-Base Directionally Solidified Superalloy
The creep-fatigue interaction in directionally solidified nickel-base superalloy was analyzed with the modified Chaboche-based unified viscoplasticity constitutive model. The model features the anisotropic material behavior, hardening/ softening, and stress relaxation. Simple low-cyclic fatigue and specified hold time experiments were conducted on a directionally solidified superalloy (DZ125) at temperatures over 760Β°C. The material parameters were optimized considering its tensile, cyclic and creep behavior with the LevenbergβMarquardt optimization procedure. The model was constructed in FORTRAN and integrated in FEA software UMAT/ABAQUS. The results show that experimental and simulated hysteresis loop size/shape, peak stresses, stress relaxation, and related areas are closely matched. The modified constitutive model was found to be instrumental for revealing the fatigue and creep-fatigue interaction behavior of such materials and can be used for practical applications.ΠΠ·Π°ΠΈΠΌΠΎΠ΄Π΅ΠΉΡΡΠ²ΠΈΠ΅ ΠΏΠΎΠ»Π·ΡΡΠ΅ΡΡΠΈ ΠΈ ΡΡΡΠ°Π»ΠΎΡΡΠΈ Π² ΡΡΠΏΠ΅ΡΡΠΏΠ»Π°Π²Π΅ Π½Π° ΠΎΡΠ½ΠΎΠ²Π΅ Π½ΠΈΠΊΠ΅Π»Ρ, ΠΏΠΎΠ»ΡΡΠ΅Π½Π½ΠΎΠ³ΠΎ Π½Π°ΠΏΡΠ°Π²Π»Π΅Π½Π½ΠΎΠΉ ΠΊΡΠΈΡΡΠ°Π»Π»ΠΈΠ·Π°ΡΠΈΠ΅ΠΉ, ΠΏΡΠΎΠ°Π½Π°Π»ΠΈΠ·ΠΈΡΠΎΠ²Π°Π½ΠΎ Ρ ΠΏΠΎΠΌΠΎΡΡΡ ΠΌΠΎΠ΄ΠΈΡΠΈΡΠΈΡΠΎΠ²Π°Π½Π½ΠΎΠΉ ΡΠ½ΠΈΡΠΈΡΠΈΡΠΎΠ²Π°Π½Π½ΠΎΠΉ ΠΎΠΏΡΠ΅Π΄Π΅Π»ΡΡΡΠ΅ΠΉ ΠΌΠΎΠ΄Π΅Π»ΠΈ Π²ΡΠ·ΠΊΠΎΠΏΠ»Π°ΡΡΠΈΡΠ½ΠΎΡΡΠΈ Π¨Π°Π±ΠΎΡΠ°. ΠΠΎΠ΄Π΅Π»Ρ Ρ
Π°ΡΠ°ΠΊΡΠ΅ΡΠΈΠ·ΡΠ΅Ρ Π°Π½ΠΈΠ·ΠΎΡΡΠΎΠΏΠ½ΠΎΠ΅ ΠΏΠΎΠ²Π΅Π΄Π΅Π½ΠΈΠ΅ ΠΌΠ°ΡΠ΅ΡΠΈΠ°Π»Π°, ΡΠΏΡΠΎΡΠ½Π΅Π½ΠΈΠ΅/ΡΠ°Π·ΡΠΏΡΠΎΡΠ½Π΅Π½ΠΈΠ΅ ΠΈ ΡΠ΅Π»Π°ΠΊΡΠ°ΡΠΈΡ Π½Π°ΠΏΡΡΠΆΠ΅Π½ΠΈΠΉ. ΠΠΊΡΠΏΠ΅ΡΠΈΠΌΠ΅Π½ΡΡ ΠΏΠΎ ΠΎΠΏΡΠ΅Π΄Π΅Π»Π΅Π½ΠΈΡ ΠΌΠ°Π»ΠΎΡΠΈΠΊΠ»ΠΎΠ²ΠΎΠΉ ΡΡΡΠ°Π»ΠΎΡΡΠΈ ΠΈ Π²ΡΠ΅ΠΌΠ΅Π½ΠΈ ΠΏΡΠ΅Π±ΡΠ²Π°Π½ΠΈΡ Π²ΡΠΏΠΎΠ»Π½Π΅Π½Ρ Π½Π° ΡΡΠΏΠ΅ΡΡΠΏΠ»Π°Π²Π΅ (DZ125) ΠΏΡΠΈ ΡΠ΅ΠΌΠΏΠ΅ΡΠ°ΡΡΡΠ°Ρ
Π²ΡΡΠ΅ 760Β°Π‘. ΠΠ°ΡΠ°ΠΌΠ΅ΡΡΡ ΠΌΠ°ΡΠ΅ΡΠΈΠ°Π»Π° ΠΎΠΏΡΠΈΠΌΠΈΠ·ΠΈΡΠΎΠ²Π°Π½Ρ Ρ ΡΡΠ΅ΡΠΎΠΌ Π΅Π³ΠΎ ΠΏΠΎΠ²Π΅Π΄Π΅Π½ΠΈΡ ΠΏΡΠΈ ΡΠ°ΡΡΡΠΆΠ΅Π½ΠΈΠΈ, ΡΠΈΠΊΠ»ΠΈΡΠ΅ΡΠΊΠΎΠΉ Π½Π°Π³ΡΡΠ·ΠΊΠ΅ ΠΈ ΠΏΠΎΠ»Π·ΡΡΠ΅ΡΡΠΈ ΠΏΡΠΈ ΠΏΠΎΠΌΠΎΡΠΈ ΠΌΠ΅ΡΠΎΠ΄Π° ΠΎΠΏΡΠΈΠΌΠΈΠ·Π°ΡΠΈΠΈ ΠΠ΅Π²Π΅Π½Π±Π΅ΡΠ³Π°βΠΠ°ΡΠΊΠ²Π°ΡΠ΄ΡΠ°. ΠΠΎΠ΄Π΅Π»Ρ ΠΏΠΎΡΡΡΠΎΠ΅Π½Π° Π½Π° ΡΠ·ΡΠΊΠ΅ Π€ΠΠ Π’Π ΠΠ ΠΈ ΠΈΠ½ΡΠ΅Π³ΡΠΈΡΠΎΠ²Π°Π½Π° Π² ΠΏΡΠΎΠ³ΡΠ°ΠΌΠΌΡ FEΠ UMAT/ABAQUS. ΠΠΎΠΊΠ°Π·Π°Π½ΠΎ, ΡΡΠΎ ΡΠΊΡΠΏΠ΅ΡΠΈΠΌΠ΅Π½ΡΠ°Π»ΡΠ½ΡΠ΅ ΠΈ ΠΌΠΎΠ΄Π΅Π»ΡΠ½ΡΠ΅ ΡΠ°Π·ΠΌΠ΅ΡΡ/ ΡΠΎΡΠΌΠ° ΠΏΠ΅ΡΠ»ΠΈ Π³ΠΈΡΡΠ΅ΡΠ΅Π·ΠΈΡΠ°, ΠΏΠΈΠΊΠΎΠ²ΡΠ΅ Π½Π°ΠΏΡΡΠΆΠ΅Π½ΠΈΡ, ΡΠ΅Π»Π°ΠΊΡΠ°ΡΠΈΡ Π½Π°ΠΏΡΡΠΆΠ΅Π½ΠΈΠΉ ΠΈ ΠΈΡ
ΠΎΠ±Π»Π°ΡΡΡ Π½Π°Ρ
ΠΎΠ΄ΡΡΡΡ Π² ΡΠΎΠΎΡΠ²Π΅ΡΡΡΠ²ΠΈΠΈ. Π£ΡΡΠ°Π½ΠΎΠ²Π»Π΅Π½ΠΎ, ΡΡΠΎ ΠΌΠΎΠ΄ΠΈΡΠΈΡΠΈΡΠΎΠ²Π°Π½Π½ΡΡ ΠΎΠΏΡΠ΅Π΄Π΅Π»ΡΡΡΡΡ ΠΌΠΎΠ΄Π΅Π»Ρ ΡΠ΅Π»Π΅ΡΠΎΠΎΠ±ΡΠ°Π·Π½ΠΎ ΠΏΡΠΈΠΌΠ΅Π½ΡΡΡ ΠΏΡΠΈ Π°Π½Π°Π»ΠΈΠ·Π΅ ΡΡΡΠ°Π»ΠΎΡΡΠΈ ΠΈ Π²Π·Π°ΠΈΠΌΠΎΠ΄Π΅ΠΉΡΡΠ²ΠΈΡ ΠΏΠΎΠ»Π·ΡΡΠ΅ΡΡΠΈ ΠΈ ΡΡΡΠ°Π»ΠΎΡΡΠΈ ΠΏΠΎΠ΄ΠΎΠ±Π½ΡΡ
ΠΌΠ°ΡΠ΅ΡΠΈΠ°Π»ΠΎΠ², ΠΎΠ½Π° ΠΌΠΎΠΆΠ΅Ρ ΡΠ°ΠΊΠΆΠ΅ Π½Π°ΠΉΡΠΈ ΠΏΡΠ°ΠΊΡΠΈΡΠ΅ΡΠΊΠΎΠ΅ ΠΏΡΠΈΠΌΠ΅Π½Π΅Π½ΠΈΠ΅
Nonequilibrium dynamics in type-II superconductors with inhomogeneous vortex pinning
We study numerically the dynamics relating to negative vortex motion in inhomogeneous pinning systems. We show that this dynamical phenomenon results from the internal field effect produced by the growing local barriers with decreasing temperature. We find that the negative motion is characterized
by a peak of negative voltage or resistance in resistanceβtemperature transport measurements. We also demonstrate that the time window to observe the negative motion is determined by the magnitude of driving force in addition to the temperature scanning rat
Nucleon-nucleon momentum correlation function for light nuclei
Nucleon-nucleon momentum correlation function have been presented for nuclear
reactions with neutron-rich or proton-rich projectiles using a nuclear
transport theory, namely Isospin-Dependent Quantum Molecular Dynamics model.
The relationship between the binding energy of projectiles and the strength of
proton-neutron correlation function at small relative momentum has been
explored, while proton-proton correlation function shows its sensitivity to the
proton density distribution. Those results show that nucleon-nucleon
correlation function is useful to reflect some features of the neutron- or
proton-halo nuclei and therefore provide a potential tool for the studies of
radioactive beam physics.Comment: Talk given at the 18th International IUPAP Conference on Few-Body
Problems in Physics (FB18), Santos, Brasil, August 21-26, 2006. To appear in
Nucl. Phys.
Scaling of anisotropy flows in intermediate energy heavy ion collisions
Anisotropic flows (, and ) of light nuclear clusters are
studied by a nucleonic transport model in intermediate energy heavy ion
collisions. The number-of-nucleon scalings of the directed flow () and
elliptic flow () are demonstrated for light nuclear clusters. Moreover,
the ratios of of nuclear clusters show a constant value of 1/2
regardless of the transverse momentum. The above phenomena can be understood by
the coalescence mechanism in nucleonic level and are worthy to be explored in
experiments.Comment: Invited talk at "IX International Conference on Nucleus-Nucleus
Collisions", Rio de Janeiro, Aug 28- Sept 1, 2006; to appear on the
proceeding issue in Nuclear Physics
Recommended from our members
Cyclodextrin-based surface acoustic wave chemical microsensors
Cyclodextrin thin films were fabricated using either self-assembled monolayer (SAM) or solgel techniques. The resulting host receptor thin films on the substrates of surface acoustic wave (SAW) resonators were studied as method of tracking organic toxins in vapor phase. The mass loading of surface-attached host monolayers on SAW resonators gave frequency shifts corresponding to typical monolayer surface coverages for SAM methods and ``multilayer`` coverages for sol-gel techniques. Subsequent exposure of the coated SAW resonators to organic vapors at various concentrations, typically 5,000 parts per millions (ppm) down to 100 parts per billions (ppb) by mole, gave responses indicating middle-ppb-sensitivity ({approximately}50 ppb) for those sensor-host-receptors and organic-toxin pairs with optimum mutual matching of polarity, size, and structural properties
Basic Magnetic Nanoparticles as Efficient Catalysts for the Preparation of Naphthopyrane Derivatives
Stress State Analysis of Iosipescu Shear Specimens for Aerogel Composite with Different Properties in Tension and Compression
AbstractThe objective of present research is to establish guidelines for preparing shear tests of ceramic-fiber-reinforced aerogel. The aerogel composite prepared by Sol-gel methods exhibits bi-modulus properties under tension and compression loadings. Bi- modulus constitutive model of the aerogel composite was built, and then verified by analysis of bending test. Finite element analysis (FEA) was presented on Iosipescu specimens with different V-notch and Round-notch configurations. Several trends have become evident: stress state of bi-modulus aerogel is different from that of isotropic material; stress concentration is a strong function of V-notch tip radius, and increasing V-notch tip radius can effectively reduce normal stress concentration at notch tips; shear stress distribution in the test region can be modified by varying notch angle when V-notch tip radiusβ€1.3mm; increasing the Round-notch radius can also effectively reduce the normal stress concentration at notch tips. Based on these observations, Round-notch specimen seems to be a favorable choice for reducing the normal stress concentration at notch tips, especially the longitudinal tensile stress concentration. Round-notch specimen with r=4mm is favorable for the uniformly distributed shear stress in the test region. Digital image correlation (DIC) was suggested for shear strain measuring
- β¦