Ice formation on a smooth or rough cold surface due to the impact of a supercooled water droplet

Ice accretion is considered in the impact of a supercooled water droplet on a smooth or rough solid surface, the roughness accounting for earlier icing. In this theoretical investigation the emphasis and novelty lie in the full nonlinear interplay of the droplet motion and the growth of the ice surface being addressed for relatively small times, over a realistic range of Reynolds numbers, Froude numbers, Weber numbers, Stefan numbers and capillary underheating parameters. The Prandtl number and the kinetic under-heating parameter are taken to be order unity. The ice accretion brings inner layers into play forcibly, affecting the outer flow. (The work includes viscous effects in an isothermal impact without phase change, as a special case, and the differences between impact with and without freezing.) There are four main findings. First, the icing dynamically can accelerate or decelerate the spreading of the droplet whereas roughness on its own tends to decelerate spreading. The interaction between the two and the implications for successive freezings are found to be subtle. Second, a focus on the dominant physical effects reveals a multi-structure within which restricted regions of turbulence are implied. The third main finding is an essentially parabolic shape for a single droplet freezing under certain conditions. Fourth is a connection with a body of experimental and engineering work and with practical findings to the extent that the explicit predictions here for ice-accretion rates are found to agree with the experimental range.

Can Effects of Dark Matter be Explained by the Turbulent Flow of Spacetime?

For the past forty years the search for dark matter has been one of the primary foci of astrophysics, although there has yet to be any direct evidence for its existence (Porter et al. 2011). Indirect evidence for the existence of dark matter is largely rooted in the rotational speeds of stars within their host galaxies, where, instead of having a ~ r^1/2 radial dependence, stars appear to have orbital speeds independent of their distance from the galactic center, which led to proposed existence of dark matter (Porter et al. 2011; Peebles 1993). We propose an alternate explanation for the observed stellar motions within galaxies, combining the standard treatment of a fluid-like spacetime with the possibility of a "bulk flow" of mass through the Universe. The differential "flow" of spacetime could generate vorticies capable of providing the "perceived" rotational speeds in excess of those predicted by Newtonian mechanics. Although a more detailed analysis of our theory is forthcoming, we find a crude "order of magnitude" calculation can explain this phenomena. We also find that this can be used to explain the graviational lensing observed around globular clusters like "Bullet Cluster".Comment: 5 pages, Accepted for publication in Journal of Modern Physics: Gravitation and Cosmology (Sept. 2012

Asian finance and the role of bankruptcy

The degree to which bankruptcy is permitted to play a role in the allocation of capital is a key distinction between the Asian state-directed financial regime and the Western market-directed version. The paper discusses the two approaches to finance and argues that a major problem with the bank finance model used in many Asian countries is its minimization of bankruptcy risks. A three-sector development model (agriculture, manufacturing, and financial sector) is developed and simulated to compare the outcomes of the two approaches separately and then to evaluate the transition costs of switching from a state- to a market-directed financial regime. The simulation results suggest that the market approach results in a higher long-run growth path because it eliminates inefficient firms through bankruptcy. The results also suggest that switching from a state- to a market-directed model can be very costly to the economy, though the transition costs can be lowered somewhat by a delayed and phased-in liberalization. At the same time, a delayed and phased-in approach may induce other difficulties not considered in the model. Several policy implications are drawn from the model and simulation results; for example, development of an infrastructure to provide for orderly bankruptcy and the development of money and capital markets should be given high priority in the liberalization process.Banks and banking - Asia ; Bankruptcy

Capturing Trojans and Irregular Satellites - the key required to unlock planetary migration

It is now accepted that the Solar system's youth was a dynamic and chaotic time. The giant planets migrated significant distances to reach their current locations, and evidence of that migration's influence on the Solar system abounds. That migration's pace, and the distance over which it occurred, is still heavily debated. Some models feature systems in which the giant planets were initially in an extremely compact configuration, in which Uranus and Neptune are chaotically scattered into the outer Solar system. Others feature architectures that were initially more relaxed, and smoother, more sedate migration. To determine which of these scenarios best represents the formation of our Solar system, we must turn to the structure of the system's small body populations, in which the scars of that migration are still clearly visible. We present the first results of a program investigating the effect of giant planet migration on the reservoirs of small bodies that existed at that time. As the planets migrate, they stir these reservoirs, scattering vast numbers of small bodies onto dynamically unstable orbits in the outer Solar system. The great majority of those bodies are rapidly removed from the system, through collisions and ejections, but a small number become captured as planetary Trojans or irregular satellites. Others are driven by the migration, leading to a significant sculpting of the asteroid belt and trans-Neptunian region. The capture and retention efficiencies to these stable reservoirs depend on the particular migration scenario used. Advocates of chaotic migration from an initially compact scenario argue that smoother, more sedate migration cannot explain the observed populations of Trojans and irregular satellites. Our results draw a strikingly different picture, revealing that such smooth migration is perfectly capable of reproducing the observed populations.Comment: 13 pages, accepted for publication in the peer-reviewed proceedings of the 12th annual Australian Space Science Conferenc

Development and Validation of NDE Standards for NASAs Advanced Composites Project

The adoption of composite materials in aircraft manufacturing for use in structural applications continues to increase but is still relatively new to the industry. Composite components have large development and certification costs in comparison to metallic structures. Traditional methods of nondestructive evaluation (NDE) used for isotropic materials such as metals may not be adequate for composite applications and therefore is a contributing factor to the cost and complexity of developing new structural composites. Additionally, the defects of interest in composite materials are significantly different from metals. Thus, good quality composite reference standards are essential to obtaining reliable and quantifiable NDE results. Ideally, reference standards contain flaws or damage whose NDE indications most closely represent those created by actual flaws/damage. They should also be easy to duplicate and inexpensive to manufacture. NASAs Advanced Composites Project, working with industry partners, developed a set of composite standards that contain a range of validated defects representing those typically found in aerospace composite materials. This paper will provide an overview of the standards fabricated, the manufacturing plans used to fabricate them, the types of defects included, and validation testing that has performed. Also discussed is an inter-laboratory round-robin test that is being performed on these standards. The paper will describe a guidance document being compiled to outline relevant inspection procedures for challenging and critical defects unique to composites where conventional techniques may not be appropriate

Aspect-based video browsing - a user study

In this paper, we present a user study on a novel video search interface based on the concept of aspect browsing. We aim to confirm whether automatically suggesting new aspects can increase the performance of an aspect-based browser. The proposed strategy is to assist the user in exploratory video search by actively suggesting new query terms and video shots. We use a clustering technique to identify potential aspects and use the results to propose suggestions to the user to help them in their search task. We evaluate this approach by analysing the users' perception and by exploiting the log files

An architecture for life-long user modelling

In this paper, we propose a united architecture for the creation of life-long user profiles. Our architecture combines different steps required for a user prole, including feature extraction and representation, reasoning, recommendation and presentation. We discuss various issues that arise in the context of life-long profiling

Supporting aspect-based video browsing - analysis of a user study

In this paper, we present a novel video search interface based on the concept of aspect browsing. The proposed strategy is to assist the user in exploratory video search by actively suggesting new query terms and video shots. Our approach has the potential to narrow the "Semantic Gap" issue by allowing users to explore the data collection. First, we describe a clustering technique to identify potential aspects of a search. Then, we use the results to propose suggestions to the user to help them in their search task. Finally, we analyse this approach by exploiting the log files and the feedbacks of a user study

Phillips CO-oxidation catalyts for long-lived CO2 lasers: Activity and initial characterization studies

Four different catalysts have been developed specifically for use in sealed carbon dioxide lasers. The catalysts have been designed to be low dusting, stable to shock and vibration, have high activity at low temperatures and have long active lifetimes. Measured global CO oxidation rates range from 1.4 to 2.2 cc CO converted per minute per gram of catalyst at ambient temperature. The catalysts also retain substantial activity at temperatures as low as -35 C. The Phillips laser catalysts are prepared in a variety of different shapes to meet the different pressure drop and gas flow profiles present in the many different styles of lasers. Each catalyst has been tested in sealed TEA lasers and has been shown to substantially increase the sealed life of the laser. Activity measurements made on the precious metal catalysts which were prepared with and without activity promoters showed that the promoter materials increase catalyst CO oxidation activity at least an order of magnitude at ambient temperature. Initial studies using H2 and CO chemisorption, X ray diffraction (XRD) and X ray photoelectron spectroscopy (XPS) have shown that the activity promoters do not significantly affect the precious metal crystallite size or the electronic structure around the precious metal. In addition, the formation or lack of formation of solid solutions between the precious metal and promoters has also been shown not to affect the activity of the promoted catalyst