Effect of thruster pulse length on thruster-exhaust damage of S13G white thermal control coatings

Rocket exhaust products which strike thermal control surfaces cause changes in solar absorptance (Alpha Sub s) and thermal emittance (Epsilon) of these surfaces. A study was made of the effect of rocket pulse duration on exhaust damage to S13G white coatings. Two pulse lengths were used - 14 msec and 50 msec. An MMH/N204 bipropellant 5-lb thrust rocket was fired into a simulated space environment with a vacuum of 0.00001 torr, a liquid helium temperature enclosure, and solar radiation. The changes in solar absorptance and thermal emittance of S13G white coatings due to rocket exhaust were made in-situ for total firing times of 58 seconds with 14 msec pulses and 223.7 sec with 50 msec pulses. The solar absorptance of S13G increased 25 percent due to 223.7 sec of exposure to 50 msec pulses and the thermal emittance was unaffected. The ratio of Alpha Sub s/Epsilon therefore increased by 25 percent. The short 14 msec pulse exhaust exposure caused between 40 and 70 percent increase in solar absorptance and a decrease of between 13 and 18 percent in thermal emittance. The corresponding increase in Alpha Sub s/Epsilon ratio was between 80 and 100 percent. Ultraviolet radiation was present in the short pulse test and may have contributed to the large damage of that test

Statistics of conductance and shot-noise power for chaotic cavities

We report on an analytical study of the statistics of conductance, $g$, and shot-noise power, $p$, for a chaotic cavity with arbitrary numbers $N_{1,2}$ of channels in two leads and symmetry parameter $\beta = 1,2,4$. With the theory of Selberg's integral the first four cumulants of $g$ and first two cumulants of $p$ are calculated explicitly. We give analytical expressions for the conductance and shot-noise distributions and determine their exact asymptotics near the edges up to linear order in distances from the edges. For $0<g<1$ a power law for the conductance distribution is exact. All results are also consistent with numerical simulations.Comment: 7 pages, 3 figures. Proc. of the 3rd Workshop on Quantum Chaos and Localisation Phenomena, Warsaw, Poland, May 25-27, 200

Correlation functions of impedance and scattering matrix elements in chaotic absorbing cavities

Wave scattering in chaotic systems with a uniform energy loss (absorption) is considered. Within the random matrix approach we calculate exactly the energy correlation functions of different matrix elements of impedance or scattering matrices for systems with preserved or broken time-reversal symmetry. The obtained results are valid at any number of arbitrary open scattering channels and arbitrary absorption. Elastic enhancement factors (defined through the ratio of the corresponding variance in reflection to that in transmission) are also discussed.Comment: 10 pages, 2 figures (misprints corrected and references updated in ver.2); to appear in Acta Phys. Pol. A (Proceedings of the 2nd Workshop on Quantum Chaos and Localization Phenomena, May 19-22, 2005, Warsaw

Medicaid Expansion in Texas: What's at Stake?

Texas is one of nearly 20 states yet to expand its Medicaid program under the Affordable Care Act (ACA), and is home to the largest number of uninsured Americans of any state in the country. For many of the state's 5 million uninsured, this decision has left them without an option for affordable health insurance. A comparison with other Southern states that have expanded Medicaid shows how this decision has left many low-income Texans less able to afford their medical bills, to pay for needed prescription drugs, and to obtain regular care for chronic conditions. These problems have been compounded by the state's opposition to outreach and enrollment assistance for many Texans who are eligible for coverage under the ACA. Ongoing efforts from stakeholders and consumer groups to persuade state leaders to expand coverage have significant implications for the well-being of millions of low-income adults in Texas

Assessing Defrosting Performance on Hydrophilic, Hydrophobic, and Micro-Patterned Heat Transfer Surfaces

In this work, differences in drainage rates and defrosting effectiveness were explored for surfaces of differing wettability. Both patterned and non-patterned surfaces were explored. To date, six surfaces have been examined— an uncoated, untreated aluminum plate (Sample 1), an identical plate treated with a hydrophilic coating (Sample 2), a plate containing evenly-spaced micro-channels with no surface coating (Sample 3), a plate containing evenly-spaced micro-channels with a hydrophobic coating (Sample 4), and a surface containing a microstructural roughness gradient both with and without a hydrophobic surface coating (Samples 5 and 6). Cyclical tests containing frosting periods and defrosting periods were conducted on each sample. Each cycle consisted of one hour of frost growth, followed by ten minutes of defrost and drainage. For these experiments, the frost layer was grown inside a Plexiglas environmental test chamber where the relative humidity was held constant (i.e. 60%, 80%) for the duration of the experiment using an ultrasonic humidifier. The temperature of the ambient air inside the enclosure was recorded to ensure that it remained constant throughout the experiment, and the surface temperature of the plate was fixed using a thermoelectric cooler (TEC). The TEC unit was placed on an electronic balance within the test chamber which permitted the frost mass to be recorded continuously during testing. Overall, the surface defrosting effectiveness varied from 52-77% across all surfaces depending on the test conditions, with one test showing slightly lower percentages. Our data show that only small differences were observed in the defrosting effectiveness between the samples. The gradient surfaces however did remove slightly more water from the surface during defrosting (as compared to the baseline) when the frost was grown at colder surface temperatures. The average increase in defrosting effectiveness at Tw = -12°C was 2-4% for Surface 6 versus Surface 1. Interestingly, when the frost was grown at warmer surface temperatures, the gradient surfaces did not perform as well. In almost all cases, however, the defrosting effectiveness increased as the surface temperature was decreased during the frost growth period. This finding suggests that defrosting effectiveness is intrinsically linked to the thermophysical properties of the grown frost layer. Additional research is needed to investigate this phenomenon more fully. The overall aim of this work is to study the effects of surface wettability and micro-structural roughness on the defrosting performance of functionalized heat transfer surfaces

Issues in health reform: How changes in eligibility may move millions back and forth between Medicaid and insurance exchanges

The Affordable Care Act will extend health insurance coverage by both expanding Medicaid eligibility and offering premium subsidies for the purchase of private health insurance through state health insurance exchanges. But by definition, eligibility for these programs is sensitive to income and can change over time with fluctuating income and changes in family composition. The law specifies no minimum enrollment period, and subsidy levels will also change as income rises and falls. Using national survey data, we estimate that within six months, more than 35 percent of all adults with family incomes below 200 percent of the federal poverty level will experience a shift in eligibility from Medicaid to an insurance exchange, or the reverse; within a year, 50 percent, or 28 million, will. To minimize the effect on continuity and quality of care, states and the federal government should adopt strategies to reduce the frequency of coverage transitions and to mitigate the disruptions caused by those transitions. Options include establishing a minimum guaranteed eligibility period and “dually certifying” some plans to serve both Medicaid and exchange enrollees

Role of electron-electron and electron-phonon interaction effect in the optical conductivity of VO2

We have investigated the charge dynamics of VO2 by optical reflectivity measurements. Optical conductivity clearly shows a metal-insulator transition. In the metallic phase, a broad Drude-like structure is observed. On the other hand, in the insulating phase, a broad peak structure around 1.3 eV is observed. It is found that this broad structure observed in the insulating phase shows a temperature dependence. We attribute this to the electron-phonon interaction as in the photoemission spectra.Comment: 6 pages, 8 figures, accepted for publication in Phys. Rev.