The dependence of the helicity bound of force-free magnetic fields on boundary conditions

This paper follows up on a previous study showing that in an open atmosphere such as the solar corona the total magnetic helicity of a force-free field must be bounded and the accumulation of magnetic helicity in excess of its upper bound would initiate a non-equilibrium situation resulting in an expulsion such as a coronal mass ejection (CME). In the current paper, we investigate the dependence of the helicity bound on the boundary condition for several families of nonlinear force-free fields. Our calculation shows that the magnitude of the helicity upper bound of force-free fields is non-trivially dependent on the boundary condition. Fields with a multipolar boundary condition can have a helicity upper bound ten times smaller than those with a dipolar boundary condition when helicity values are normalized by the square of their respective surface poloidal fluxes. This suggests that a coronal magnetic field may erupt into a CME when the applicable helicity bound falls below the already accumulated helicity as the result of a slowly changing boundary condition. Our calculation also shows that a monotonic accumulation of magnetic helicity can lead to the formation of a magnetic flux rope applicable to kink instability. This suggests that CME initiations by exceeding helicity bound and by kink instability can both be the consequences of helicity accumulation in the corona. Our study gives insights into the observed associations of CMEs with the magnetic features at their solar surface origins.Comment: accepted by Ap

Apparatus and method for explosive bonding to edge of flyer plate

The invention is an apparatus and a process for the explosive joining of a flyer plate and a base plate. The apparatus consists of a flyer plate positioned over a base plate. The flyer plate has a notch containing a filler material in intimate contact with the flyer plate. An adhesive means holds a ribbon explosive partially overlapping the notch in the flyer plate. A detonating means initiates the ribbon explosive that drives the flyer plate to accomplish a high velocity, angular collision between the mating surfaces. This collision creates surface melts and effacing bonding, resulting in electron sharing linkups between the plates. An unbonded tab fractures at a base of the notch leaving a bond to an edge of the attached flyer plate

The New Economics of Teachers and Education

Rapidly growing costs of elementary and secondary education are studied in the context of the rising value of women's time. The three-fold increase in direct costs of education per student in the past three decades was caused by increasing demand and utilization of teacher and staff inputs, attributable to growing market opportunities of women and changes in the structure of families. Substitution of purchased teacher and staff inputs for own household time in the total production of children's education and maturation is a predictable economic response to these forces. On the supply side, the 'flexibility option,' that female teachers who take temporary leaves to raise children do not suffer subsequent wage loss upon reentry, is shown to be an important attraction of the teaching profession to women. Other college educated women suffer reentry wage losses of 10 percent per year of leave. The estimated value of flexibility in teaching is 5 percent of life-cycle earnings and will fall as labor force interruptions of women for child-rearing become less frequent. Both supply and demand considerations suggest that the direct costs of education per student will continue to increase in the future, independent of political and other organization reforms of schools.

Flyer

A flyer advertising the Workers with Disabilities: The Role of Workplace Flexibility event on November 13, 2006 hosted by Cornell University on behalf of Workplace Flexibility 2010

A Hybrid Radial Basis Function - Pseudospectral Method for Thermal Convection in a 3-D Spherical Shell

A novel hybrid spectral method that combines radial basis function (RBF) and Chebyshev pseudospectral (PS) methods in a “2+1” approach is presented for numerically simulating thermal convection in a 3-D spherical shell. This is the first study to apply RBFs to a full 3D physical model in spherical geometry. In addition to being spectrally accurate, RBFs are not defined in terms of any surface based coordinate system such as spherical coordinates. As a result, when used in the lateral directions, as in this study, they completely circumvent the pole issue with the further advantage that nodes can be “scattered” over the surface of a sphere. In the radial direction, Chebyshev polynomials are used, which are also spectrally accurate and provide the necessary clustering near the boundaries to resolve boundary layers. Applications of this new hybrid methodology are given to the problem of convection in the Earth’s mantle,which is modeled by a Boussinesq fluid at infinite Prandtl number. To see whether this numerical technique warrants further investigation, the study limits itself to an isoviscous mantle.Benchmark comparisons are presented with other currently used mantle convection codes for Rayleigh number 7 · 103 and 105. The algorithmic simplicity of the code (mostly due to RBFs)allows it to be written in less than 400 lines of Matlab and run on a single workstation. We find that our method is very competitive with those currently used in the literature

Flyer

The flyer of the Meeting the Needs of Today’s Families: The Role of Workplace Flexibility event held May 1, 2006

Briefing Flyer

The briefing flyer from the Flexible Work Arrangements: Working for Americas Employers and Employees event held December 14, 2009

eSciDoc.PubMan - flyer

Information flyer about the eSciDoc solution PubMan