2,283 research outputs found
Analytic Criteria for Power Exhaust in Divertors due to Impurity Radiation
Present divertor concepts for next step experiments such ITER and TPX rely
upon impurity and hydrogen radiation to transfer the energy from the edge
plasma to the main chamber and divertor chamber walls. The efficiency of these
processes depends strongly on the heat flux, the impurity species, and the
connection length. Using a database for impurity radiation rates constructed
from the ADPAK code package, we have developed criteria for the required
impurity fraction, impurity species, connection length and electron temperature
and density at the mid-plane. Consistent with previous work, we find that the
impurity radiation from coronal equilibrium rates is, in general, not adequate
to exhaust the highest expected heating powers in present and future
experiments. As suggested by others, we examine the effects of enhancing the
radiation rates with charge exchange recombination and impurity recycling, and
develop criteria for the minimum neutral fraction and impurity recycling rate
that is required to exhaust a specified power. We also use this criteria to
find the optimum impurity for divertor power exhaust.Comment: Preprint for the 11th PSI meeting, Adobe pdf with 14 figures, 15
page
Gravitomagnetic Resonance Shift due to a Slowly Rotating Compact Star
The effect of a slowly rotating mass on a forced harmonic oscillator with two
degrees of freedom is studied in the weak field approximation. It is found that
according to the general theory of relativity there is a shift in the resonat
frequency of the oscillator which depends on the density and rotational
frequency of the gravitational source. The proposed shift is quite small under
normal physical situations however it is estimated that for compact x-ray
sources such as white dwarfs, pulsars, and neutron stars the shift is quite
appreciable.Comment: 8 pages, 2 figures, Accepted for Publication in Inter. Journal of
Modern Physics
Exposure damage mechanisms for KCl windows in high power laser systems
An experimental study of the 10.6 micrometer and 0.6328 micrometer optical properties of single crystal and europium doped polycrystal is described. Significant variations in the optical properties are observed over periods of exposure up to 100 hours. Models are proposed to predict the 10.6 micrometer absorptivity for long exposure periods. Mechanical creep has been detected in both materials at high temperature
Advanced high temperature static strain sensor development
An examination was made into various techniques to be used to measure static strain in gas turbine liners at temperatures up to 1150 K (1600 F). The methods evaluated included thin film and wire resistive devices, optical fibers, surface acoustic waves, the laser speckle technique with a heterodyne readout, optical surface image and reflective approaches and capacitive devices. A preliminary experimental program to develop a thin film capacitive device was dropped because calculations showed that it would be too sensitive to thermal gradients. In a final evaluation program, the laser speckle technique appeared to work well up to 1150 K when it was used through a relatively stagnant air path. The surface guided acoustic wave approach appeared to be interesting but to require too much development effort for the funds available. Efforts to develop a FeCrAl resistive strain gage system were only partially successful and this part of the effort was finally reduced to a characterization study of the properties of the 25 micron diameter FeCrAl (Kanthal A-1) wire. It was concluded that this particular alloy was not suitable for use as the resistive element in a strain gage above about 1000 K
Dough development by sheeting and its application to bread production from composite flours
This article describes a simple, low power sheeting development baking process and demonstrates its application to the production of bread from a variety of composite flours
Model-based Robotic Dynamic Motion Control for the Robonaut 2 Humanoid Robot
Robonaut 2 (R2), an upper-body dexterous humanoid robot, has been undergoing experimental trials on board the International Space Station (ISS) for more than a year. R2 will soon be upgraded with two climbing appendages, or legs, as well as a new integrated model-based control system. This control system satisfies two important requirements; first, that the robot can allow humans to enter its workspace during operation and second, that the robot can move its large inertia with enough precision to attach to handrails and seat track while climbing around the ISS. This is achieved by a novel control architecture that features an embedded impedance control law on the motor drivers called Multi-Loop control which is tightly interfaced with a kinematic and dynamic coordinated control system nicknamed RoboDyn that resides on centralized processors. This paper presents the integrated control algorithm as well as several test results that illustrate R2's safety features and performance
An Australian rental housing conditions research infrastructure
Each year the proportion of Australians who rent their home increases and, for the first time in generations, there are now as many renters as outright homeowners. Researchers and policy makers, however, know very little about housing conditions within Australia's rental housing sector due to a lack of systematic, reliable data. In 2020, a collaboration of Australian universities commissioned a survey of tenant households to build a data infrastructure on the household and demographic characteristics, housing quality and conditions in the Australian rental sector. This data infrastructure was designed to be national (representative across all Australian States and Territories), and balanced across key population characteristics. The resultant Australian Rental Housing Conditions Dataset (ARHCD) is a publicly available data infrastructure for researchers and policy makers, providing a basis for national and international research
Detectability of gravitational wave events by spherical resonant-mass antennas
We have calculated signal-to-noise ratios for eight spherical resonant-mass
antennas interacting with gravitational radiation from inspiralling and
coalescing binary neutron stars and from the dynamical and secular bar-mode
instability of a rapidly rotating star. We find that by using technology that
could be available in the next several years, spherical antennas can detect
neutron star inspiral and coalescence at a distance of 15 Mpc and the dynamical
bar-mode instability at a distance of 2 Mpc.Comment: 39 pages, 4 EPS Figures, some additional SNRs for secular
instabilities, some changes to LIGO SNRs, Appendix added on the asymptotic
expansion of energy sensitivity, corrected supernova rates. Results available
at http://www.physics.umd.edu/rgroups/gen_rel_exp/snr.html Submitted to Phys.
Rev.
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