Effect of Stirrups on Behavior of Normal and High Strength Concrete Columns

This paper deals with an experimental investigation and numerical simulation of reinforced concrete columns. The behavior of normal and high strength columns is studied, with special attention paid to the confinement effects of transversal reinforcement in columns with a square cross section. The character of a failure, and the strengths, ductility and post-peak behavior of columns are observed in experiments and also in numerical solution. A three-dimensional computational model based on the microplane model for concrete was constructed and compared with experimental data. The results of the numerical model showed good agreement in many aspects, and proved the capabilities of the used material model.

Materials Properties of Modifeied Ni-Based Alloy

The thermomechanical processing of NiMoCr solid solution nickel base superalloy is the way to considerably influence the grain size. As uniform coarse grain size increases the creep strength and crack growth resistance. In the work, the processing to achieve uniform recrystallized grain structure with variation of thermomechanical parameters is investigated. The creep behavior of the alloy after various hot working conditions is determined. The results of creep tests showed that creep characteristics such as strain rate and lifetime were greatly dependent on the initial hot working conditions and annealing parameters

Materials Properties of Modifeied Ni-Based Alloy

The thermomechanical processing of NiMoCr solid solution nickel base superalloy is the way to considerably influence the grain size. As uniform coarse grain size increases the creep strength and crack growth resistance. In the work, the processing to achieve uniform recrystallized grain structure with variation of thermomechanical parameters is investigated. The creep behavior of the alloy after various hot working conditions is determined. The results of creep tests showed that creep characteristics such as strain rate and lifetime were greatly dependent on the initial hot working conditions and annealing parameters

CORRELATIONS OF PLASMA DENSITY AND MAGNETIC FIELD STRENGTH IN THE HELIOSHEATH

The crossing of the termination shock (TS) by Voyager 2 in 2007 at 84 AU allows a comparison of fluctuations in different heliosheath regions. The Letter concentrates on MHD waves that exhibit a significant correlation between the magnetic field strength and plasma density. The correlations between both quantities were computed on 2?hr time intervals in the frequency range of 1 × 10[superscript -4] to 4 × 10[superscript -3] Hz. We separate the data into two regions with different magnetic field behavior; the post-TS region with many crossings of the current sheet and the unipolar region where the magnetic field direction remains nearly constant. We find that typical correlation coefficients in these regions are about 0.55-0.65, larger than in Earth's magnetosheath. The largest correlations occur when the spectrum of magnetic field fluctuations is dominated by low frequencies.Grant Agency of the Czech Republic (Contract 205/09/0170)Grant Agency of the Czech Republic (Contract 205/07/0694)Grant Agency of the Czech Republic (Contract 202/08/H057)Czech Republic. Ministry of Education (Research Plan 0021620860)United States. National Aeronautics and Space Administration (Voyager Project)United States. National Aeronautics and Space Administration (Grant NNX08AC04G

PRESSURE PULSES AT

Voyager 1 (V1) crossed the heliopause into the local interstellar medium (LISM) in 2012. The LISM is a dynamic region periodically disturbed by solar transients with outward-propagating shocks, cosmic-ray intensity changes and anisotropies, and plasma wave oscillations. Voyager 2 (V2) trails V1 and thus may observe the solar transients that are later observed at V1. V2 crossed the termination shock in 2007 and is now in the heliosheath. Starting in 2012, when solar maximum conditions reached V2, five possible merged interaction regions (MIRs) have been observed by V2 in the heliosheath. The timing is consistent with these MIRs driving the transients observed by V1 in the LISM. The largest heliosheath MIR was observed by V2 in late 2015 and should reach V1 in 2018.Jet Propulsion Laboratory (U.S.) (contract 959203

Pressure balance at the magnetopause: Experimental studies

The pressure balance at the magnetopause is formed by magnetic field and plasma in the magnetosheath, on one side, and inside the magnetosphere, on the other side. In the approach of dipole earth's magnetic field configuration and gas-dynamics solar wind flowing around the magnetosphere, the pressure balance predicts that the magnetopause distance R depends on solar wind dynamic pressure Pd as a power low R ~ Pd^alpha, where the exponent alpha=-1/6. In the real magnetosphere the magnetic filed is contributed by additional sources: Chapman-Ferraro current system, field-aligned currents, tail current, and storm-time ring current. Net contribution of those sources depends on particular magnetospheric region and varies with solar wind conditions and geomagnetic activity. As a result, the parameters of pressure balance, including power index alpha, depend on both the local position at the magnetopause and geomagnetic activity. In addition, the pressure balance can be affected by a non-linear transfer of the solar wind energy to the magnetosheath, especially for quasi-radial regime of the subsolar bow shock formation proper for the interplanetary magnetic field vector aligned with the solar wind plasma flow.Comment: 8 pages, 2 figure

Anisotropy of Magnetic Field and Velocity Fluctuations in the Solar Wind

We present a large statistical study of the fluctuation anisotropy in minimum variance (MV) frames of the magnetic field and solar wind velocity. We use 2, 10, 20, and 40 minute intervals of simultaneous magnetic field (the Wind spacecraft) and velocity (the Spektr-R spacecraft) observations. Our study confirms that magnetic turbulence is a composite of fluctuations varying along the mean magnetic field and those changing in the direction perpendicular to the mean field. Regardless of the length scale within the studied range of spacecraft-frame frequencies, ≈90% of the observed magnetic field fluctuations exhibit an MV direction aligned with the mean magnetic field, ≈10% of events have the MV direction perpendicular to the background field, and a negligible portion of fluctuations has no preferential direction. On the other hand, the MV direction of velocity fluctuations tends to be distributed more uniformly. An analysis of magnetic compressibility and density fluctuations suggests that the fluctuations resemble properties of Alfvénic fluctuations if the MV direction is aligned with background magnetic field whereas slow-mode-like fluctuations have the MV direction perpendicular to the background field. The proportion between Alfvénic and slow-mode-like fluctuations depends on plasma β and length scale: the dependence on the solar wind speed is weak. We present 3D numerical MHD simulations and show that the numerical results are compatible with our experimental results

Do we know the actual magnetopause position for typical solar wind conditions?

We compare predicted magnetopause positions at the subsolar point and four reference points in the terminator plane obtained from several empirical and numerical MHD models. Empirical models using various sets of magnetopause crossings and making different assumptions about the magnetopause shape predict significantly different magnetopause positions (with a scatter >1 RE) even at the subsolar point. Axisymmetric magnetopause models cannot reproduce the cusp indentations or the changes related to the dipole tilt effect, and most of them predict the magnetopause closer to the Earth than nonaxisymmetric models for typical solar wind conditions and zero tilt angle. Predictions of two global nonaxisymmetric models do not match each other, and the models need additional verification. MHD models often predict the magnetopause closer to the Earth than the nonaxisymmetric empirical models, but the predictions of MHD simulations may need corrections for the ring current effect and decreases of the solar wind pressure that occur in the foreshock. Comparing MHD models in which the ring current magnetic field is taken into account with the empirical Lin et al. model, we find that the differences in the reference point positions predicted by these models are relatively small for Bz=0. Therefore, we assume that these predictions indicate the actual magnetopause position, but future investigations are still needed.Key PointsEmpirical models predict significantly different magnetopause positions even at the subsolar pointAxisymmetric empirical models predict the magnetopause closer to the Earth than nonaxisymmetric empirical models for zero tilt angleResults of MHD models with the ring current magnetic field lie close to results of the nonaxisymmetric Lin et al. modelPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134087/1/jgra52758_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134087/2/jgra52758.pd