4,984 research outputs found
Bistability and hysteresis of dipolar dynamos generated by turbulent convection in rotating spherical shells
Bistability and hysteresis of magnetohydrodynamic dipolar dynamos generated by turbulent convection in rotating spherical fluid shells is demonstrated. Hysteresis appears as a transition between two distinct regimes of dipolar dynamos with rather different properties including a pronounced difference in the amplitude of the axisymmetric poloidal field component and in the form of the differential rotation. The bistability occurs from the onset of dynamo action up to about 9 times the critical value of the Rayleigh number for onset of convection and over a wide range of values of the ordinary and the magnetic Prandtl numbers including the value unity
A local defect resonance for linear and nonlinear ultrasonic thermography
An efficient wave-defect interaction is the key to a high thermal response of flaws in ultrasonic thermography. To selectively enhance defect vibrations a concept of local defect resonance is developed and applied to ultrasonic activation of defects. The frequency match between the defect resonance frequency and the probing ultrasonic wave results in a substantial rise of a local defect temperature. The defect resonance is accompanied by depletion of the excitation frequency vibration due to nonlinear frequency conversion to higher harmonics. The local generation of higher frequency components provides a high thermal defect response in such an acoustically nonlinear thermography mode
Financing health care in high-income countries
The main lesson from the experience of high-income countries with health care financing is a simple one: financing reforms should support the ultimate goal of universal coverage. Most high-income countries started with voluntary health insurance systems, which were then gradually extended to compulsory social insurance for certain groups and finally reached universal coverage, either as nationwide social health insurance schemes or as tax-financed national health services. The risk pooling and prepayment functions are essential. Moreover, the revenue collection mechanisms, whether as general tax revenues or payroll taxes, are secondary to the basic object of providing financial protection through effective risk pooling mechanisms. The experience of high-income countries indicates that private health insurance, medical savings accounts, and other forms of private resource collection are supplementary methods for increasing universal coverage.
Aerobee 150 structural and aerodynamic pitch coupling
Aerobee 150 structural and aerodynamic pitch coupling failure analysis based on flight performance data reductio
Dynamo Effects Near The Transition from Solar to Anti-Solar Differential Rotation
Numerical MHD simulations play increasingly important role for understanding
mechanisms of stellar magnetism. We present simulations of convection and
dynamos in density-stratified rotating spherical fluid shells. We employ a new
3D simulation code for the solution of a physically consistent anelastic model
of the process with a minimum number of parameters. The reported dynamo
simulations extend into a "buoyancy-dominated" regime where the buoyancy
forcing is dominant while the Coriolis force is no longer balanced by pressure
gradients and strong anti-solar differential rotation develops as a result. We
find that the self-generated magnetic fields, despite being relatively weak,
are able to reverse the direction of differential rotation from anti-solar to
solar-like. We also find that convection flows in this regime are significantly
stronger in the polar regions than in the equatorial region, leading to
non-oscillatory dipole-dominated dynamo solutions, and to concentration of
magnetic field in the polar regions. We observe that convection has different
morphology in the inner and at the outer part of the convection zone
simultaneously such that organized geostrophic convection columns are hidden
below a near-surface layer of well-mixed highly-chaotic convection. While we
focus the attention on the buoyancy-dominated regime, we also demonstrate that
conical differential rotation profiles and persistent regular dynamo
oscillations can be obtained in the parameter space of the rotation-dominated
regime even within this minimal model.Comment: Published in the Astrophysical Journa
A compendium of NASA Aerobee sounding rocket launchings for 1966
Compendium of Aerobee sounding rocket launchings for 196
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