989 research outputs found
Electrophoretic deposition of gradated oxidation resistant coatings on tantalum-10 tungsten alloy
Material selection and electrophoretic deposition studies of high temperature oxidation resistant coatings on tantalum-10 tungsten allo
Development of oxidation resistant coatings for use above 3500 deg F
Physical property evaluation of oxidation resistant coating materials for high temperature protection of tantalum-base alloy
Student Counseling Program in Twenty Iowa Colleges
A survey was made of certain student personnel practices in twenty Iowa colleges by submitting a questionnaire and obtaining follow-up data one year later. While most colleges provide student counseling service, specific measures and procedures vary widely. There is no uniformity in regard to the testing program or the means for assisting students with How to Study problems. Generally speaking, any professional counseling effort is supplemented by adviser service rendered by regular faculty members
Do correlations create an energy gap in electronic bilayers? Critical analysis of different approaches
This paper investigates the effect of correlations in electronic bilayers on
the longitudinal collective mode structure. We employ the dielectric
permeability constructed by means of the classical theory of moments. It is
shown that the neglection of damping processes overestimates the role of
correlations. We conclude that the correct account of damping processes leads
to an absence of an energy gap.Comment: 4 page
The Nonlinear Debye-Onsager Relaxation Effect in Weakly Ionized Plasmas
A weakly ionized plasma under the influence of a strong electric field is
considered. Supposing a local Maxwellian distribution for the electron momenta
the plasma is described by hydrodynamic equations for the pair distribution
functions. These equations are solved and the relaxation field is calculated
for an arbitrary field strength. It is found that the relaxation effect becomes
lower with increasing strength of the electrical field.Comment: 4 pages, 1 figur
Aeorodynamic characteristics of an air-exchanger system for the 40- by 80-foot wind tunnel at Ames Research Center
A 1/50-scale model of the 40- by 80-Foot Wind Tunnel at Ames Research Center was used to study various air-exchange configurations. System components were tested throughout a range of parameters, and approximate analytical relationships were derived to explain the observed characteristics. It is found that the efficiency of the air exchanger could be increased (1) by adding a shaped wall to smoothly turn the incoming air downstream, (2) by changing to a contoured door at the inlet to control the flow rate, and (3) by increasing the size of the exhaust opening. The static pressures inside the circuit then remain within the design limits at the higher tunnel speeds if the air-exchange rate is about 5% or more. Since the model is much smaller than the full-scale facility, it is not possible to completely duplicate the tunnel, and it will be necessary to measure such characteristics as flow rate and tunnel pressures during implementation of the remodeled facility. The aerodynamic loads estimated for the inlet door and for nearby walls are also presented
An Analysis of Surface Relaxation in the Surface Cauchy--Born Model
The Surface Cauchy-Born (SCB) method is a computational multi-scale method
for the simulation of surface-dominated crystalline materials. We present an
error analysis of the SCB method, focused on the role of surface relaxation. In
a linearized 1D model we show that the error committed by the SCB method is
O(1) in the mesh size; however, we are able to identify an alternative
"approximation parameter" - the stiffness of the interaction potential - with
respect to which the error in the mean strain is exponentially small. Our
analysis naturally suggests an improvement of the SCB model by enforcing
atomistic mesh spacing in the normal direction at the free boundary
A Disciplined Approach to Accident Analysis Development and Control Selection
Abstract The development and use of a Safety Input Review Committee (SIRC) process promotes consistent and disciplined Accident Analysis (AA) development to ensure that it accurately reflects facility design and operation; and that the credited controls are effective and implementable. Lessons learned from past efforts were reviewed and factored into the development of this new process. The implementation of the SIRC process has eliminated many of the problems previously encountered during Safety Basis (SB) document development. This process has been subsequently adopted for use by several Savannah River Site (SRS) facilities with similar results and expanded to support other analysis activities
Nonlinear relaxation field in charged systems under high electric fields
The influence of an external electric field on the current in charged systems
is investigated. The results from the classical hierarchy of density matrices
are compared with the results from the quantum kinetic theory. The kinetic
theory yields a systematic treatment of the nonlinear current beyond linear
response. To this end the dynamically screened and field-dependent
Lenard-Balescu equation is integrated analytically and the nonlinear relaxation
field is calculated. The classical linear response result known as Debye -
Onsager relaxation effect is only obtained if asymmetric screening is assumed.
Considering the kinetic equation of one specie the other species have to be
screened dynamically while the screening with the same specie itself has to be
performed statically. Different other approximations are discussed and
compared.Comment: language correction
Equation of state of a strongly magnetized hydrogen plasma
The influence of a constant uniform magnetic field on the thermodynamic
properties of a partially ionized hydrogen plasma is studied. Using the method
of Green' s function various interaction contributions to the thermodynamic
functions are calculated. The equation of state of a quantum magnetized plasma
is presented within the framework of a low density expansion up to the order
e^4 n^2 and, additionally, including ladder type contributions via the bound
states in the case of strong magnetic fields (2.35*10^{5} T << B << 2.35*10^{9}
T). We show that for high densities (n=10^{27-30} m^{-3}) and temperatures
T=10^5 - 10^6 K typical for the surface of neutron stars nonideality effects
as, e.g., Debye screening must be taken into account.Comment: 12 pages, 2 Postscript figures. uses revtex, to appear in Phys. Rev.
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