Influence of pore-scale disorder on viscous fingering during drainage

We study viscous fingering during drainage experiments in linear Hele-Shaw cells filled with a random porous medium. The central zone of the cell is found to be statistically more occupied than the average, and to have a lateral width of 40% of the system width, irrespectively of the capillary number $Ca$. A crossover length $w_f \propto Ca^{-1}$ separates lower scales where the invader's fractal dimension $D\simeq1.83$ is identical to capillary fingering, and larger scales where the dimension is found to be $D\simeq1.53$. The lateral width and the large scale dimension are lower than the results for Diffusion Limited Aggregation, but can be explained in terms of Dielectric Breakdown Model. Indeed, we show that when averaging over the quenched disorder in capillary thresholds, an effective law $v\propto (\nabla P)^2$ relates the average interface growth rate and the local pressure gradient.Comment: 4 pages, 4 figures, submitted to Phys Rev Letter

Fracture Mechanics Testing of Titanium 6AL-4V in AF-M315E

The Green Propellant Infusion Mission (GPIM) will demonstrate the performance of AF-M315E monopropellant on orbit. Flight certification requires a safe-life analysis of the titanium alloy fuel tank to ensure inherent processing flaws will not cause failure during the design life of the tank. Material property inputs for this analysis require testing to determine the stress intensity factor for environment-assisted cracking (KEAC) of Ti 6Al-4V in combination with the AF-M315E monopropellant. Testing of single-edge notched, or SE(B), specimens representing the bulk tank membrane and weld material were performed in accordance with ASTM E1681. Specimens with fatigue pre-cracks were loaded into test fixtures so that the crack tips were exposed to AF-M315E at 50 C for a duration of 1,000 hours. Specimens that did not fail during exposure were opened to inspect the crack surfaces for evidence of crack growth. The threshold stress intensity value, KEAC, is the highest applied stress intensity that produced neither a failure of the specimen during the exposure nor showed evidence of crack growth. The threshold stress intensity factor for environment-assisted cracking of the Ti 6Al-4V forged tank material was found to be at least 22 ksiin and at least 31 ksiin for the weld material when exposed to AF-M315E monopropellant

Analysis of direct segregated boundary-domain integral equations for variable-coefficient mixed bvps in exterior domains

This is the post-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2013 World Scientific Publishing.Direct segregated systems of boundary-domain integral equations are formulated for the mixed (Dirichlet–Neumann) boundary value problems for a scalar second-order divergent elliptic partial differential equation with a variable coefficient in an exterior three-dimensional domain. The boundary-domain integral equation system equivalence to the original boundary value problems and the Fredholm properties and invertibility of the corresponding boundary-domain integral operators are analyzed in weighted Sobolev spaces suitable for infinite domains. This analysis is based on the corresponding properties of the BVPs in weighted Sobolev spaces that are proved as well.The work was supported by the grant EP/H020497/1 \Mathematical analysis of localised boundary-domain integral equations for BVPs with variable coefficients" of the EPSRC, UK

Trends in the Composition of Consumer Expenditure: Australia 1854-1913

This paper fust surveys available evidence on consumption patterns in the period between the gold rushes and the fust world war (Section 1), then attempts to integrate this evidence to achieve a reasonably consistent set of estimates across the period (Section 2). The changes in the composition of consumption activity are then compared with those occurring since 1914 in Australia, and also with evidence for the United States and several European countries between 1875 and 1914 (Section 3). The share of food items in total consumption has declined while the shares of clothing, housing and "other" items increased between the 1850s and 1914, though this did not occur steadily across the period. Australian and U.S. consumption patterns seem broadly comparable at the end of the nineteenth century.historical analysis; income; growth rate; household

Soil Phase Photodegradation of Toxic Organics at Contaminated Disposal Sites for Soil Renovation and Groundwater Quality Protection

Accurate assessment of the potential for contaminated soil remediation requires detailed knowledge of the fate of waste constituents within the soil environment. For many non-biodegradable organics compounds, photochemical degradation may provide a potential pathway for the removal of such compounds from soil surfaces. A study was conducted to evaluate the rate of photodegradation of ten hazardous organic compounds from three soils, silica gel, and four soil minerals (kaolinite, montmorillonite, illite, and calcite) under conditions of controlled irradiation. In addition, the effect of siz amendment treatments (methylene blue, riboflavin, hydrogen peroxide, diethylamine, peat moss, and silica gel) on the rates of compound loss was also investigated. Soil and mineral samples were spiked with various combinations of m-cresol, quinoline, biphenyl, dibenzo[a]furan, fluorene, pentachlorophenol, phenanthrene, anthracene, 9H-carbazole and pyrene at either 500 or 1000 mg/kg initial soil concentration of each chemical. Amendments were applied to the soils and minerals and duplicate samples were irradiated in petri dishes under ultraviolet or visible light while spike controls were inclubated in the dark. Linear regression of soil/mineral contaminant concentration data showed that first order kinetic modeling best described the degradation process. Significant loss of anthracene occurred on all surfaces tested althrough the rate of loss varied with surface type and, for some surfaces, with the spiking solution concentration and chemical mixtures. Anthracene loss from silica gel was the msot rapid of all reactions observed. Skumpah soil, a light colored alkaline soil, yielded the greatest reduction in contaminant concentrations found in the soil studies. Calcium kaolinite displaed the most rapid kinetics of the mineral surfaces tested. Loss of the other test compounds was observed from only some of the surfaces investigated. Anthraquinone and fluorenone were identified as the major degradation products of the photoreaction of anthracene and fluorene. Under the conditions of this study, soild and mineral type, as well as surface renewal via mixing, were found to have more effect on degradation rates than any of the amendments that were tested

The Resonance in the B-P-a Reaction

The yield of alpha particles of range greater than 2 cms. from boron bombarded by protons has been studied as a function of bombarding energy in the range from 100 to 200 ekv, using a thin target, either methyl borate or boron trifluoride at pressures of 1 mm. of Hg. The yield vs. energy curve shows an approximately exponential rise on which is superposed a sharp (half breadth ~ 6 ekv) intense line at 150 ± ekv. There is some indication of a weaker and much broader line at 190 ekv. Number range curves are not yet available, but the appearance of pulses on the oscillograph screen leads us to suppose that the high yield (line) at 150 ekv is due to emission of a homogeneous long-range group

Using AI/expert system technology to automate planning and replanning for the HST servicing missions

This paper describes a knowledge-based system that has been developed to automate planning and scheduling for the Hubble Space Telescope (HST) Servicing Missions. This new system is the Servicing Mission Planning and Replanning Tool (SM/PART). SM/PART has been delivered to the HST Flight Operations Team (FOT) at Goddard Space Flight Center (GSFC) where it is being used to build integrated time lines and command plans to control the activities of the HST, Shuttle, Crew and ground systems for the next HST Servicing Mission. SM/PART reuses and extends AI/expert system technology from Interactive Experimenter Planning System (IEPS) systems to build or rebuild time lines and command plans more rapidly than was possible for previous missions where they were built manually. This capability provides an important safety factor for the HST, Shuttle and Crew in case unexpected events occur during the mission

Spectropolarimetric observations of Herbig Ae/Be Stars I: HiVIS spectropolarimetric calibration and reduction techniques

Using the HiVIS spectropolarimeter built for the Haleakala 3.7m AEOS telescope in Hawaii, we are collecting a large number of high precision spectropolarimetrc observations of stars. In order to precisely measure very small polarization changes, we have performed a number of polarization calibration techniques on the AEOS telescope and HiVIS spectrograph. We have extended our dedicated IDL reduction package and have performed some hardware upgrades to the instrument. We have also used the ESPaDOnS spectropolarimeter on CFHT to verify the HiVIS results with back-to-back observations of MWC 361 and HD163296. Comparision of this and other HiVIS data with stellar observations from the ISIS and WW spectropolarimeters in the literature further shows the usefulness of this instrument.Comment: 35 pages, 44 figures, Accepted by PAS