The search for clean cash

One hundred and fifty years ago this week, on 10 April 1861, the Massachusetts Institute of Technology (MIT) received its charter. Although hardly the oldest institution of higher learning in the Anglo-American world — Harvard University was already well into its third century by then, and the British universities of Cambridge and Oxford were each on the cusp of their eighth — MIT quickly became a trendsetter. Founder William Barton Rogers built a curriculum around the school's motto Mens et manus: mind and hand. He and his faculty members incorporated laboratory instruction into the most elementary undergraduate courses and fostered close ties between basic science and the practical arts — pedagogical innovations that quickly inspired many imitators

The influence of edge undulation on vortex formation for low-aspect-ratio propulsors

Experiments to study the effect of edge undulation on vortex formation have been conducted on impulsively accelerated plates. Abstractions of propulsors found in nature are produced by imprinting undulatory features with varying wavelengths onto the circumferential vortex-forming edge of circular plates. The effects of the small-scale disturbances introduced by these modifications are accessed by means of force measurements and time-resolved particle image velocimetry. Investigations of four different geometries at two different Reynolds numbers reveal an insensitivity of the flow towards length scales smaller than or similar to the thickness of the feeding shear layer. However, the instabilities in the shear layer and the coherence of the vortex wake are influenced when the wavelength of the undulation exceeds the shear-layer thickness by a significant margin. This results in a force augmentation due to enhanced entrainment into the turbulent vortex core, and thus an associated faster vortex growth rate. Yet, contrary to prior expectations, the time of vortex pinch-off remains constant for all edge modifications. The cause–effect relationship behind the stability of the vortex wake is further investigated. While for small edge undulations a turbulent transition of the vortex core results in vortex pinch-off, for larger edge undulations the turbulent vortex core is found to be fed constantly with additional circulation from the shear layer

DOM-based Content Extraction of HTML Documents

Web pages often contain clutter around the body of the article as well as distracting features that take away from the true information that the user is pursuing. This can range from pop-up ads to flashy banners to unnecessary images and links scattered around the screen. Extraction of 'useful and relevant' content from web pages, has many applications ranging from lightweight environments, like cell phone and PDA browsing, to speech rendering for the visually impaired, to text summarization Most approaches to removing the clutter or making the content more readable involves either changing the size of the font or simply removing certain HTML-denoted components like images, thus taking away from the webpage's inherent look and feel. Unlike Content Reformatting, which aims to reproduce the entire webpage in a more convenient form, our solution directly addresses Content Extraction. We have developed a framework that employs an easily extensible set of techniques that incorporate advantages of previous work on content extraction while limiting the disadvantages. Our key insight is to work with the Document Object Model tree (after parsing and correcting the HTML), rather than with raw HTML markup. We have implemented our approach in a publicly available Web proxy that anyone can use to extract content from HTML web pages for their own purposes

Force estimates in turbulent vortex wakes of accelerating propulsors: The effects of edge undulation on vortex formation

The effects of edge undulation on separated flows and vortex formation are investigated with various geometries of accelerated, low aspect-ratio propulsors. In addition to force measurements, multi-camera planar particle image velocimetry (PIV) is applied for a large field of view of approximately 1.9 m × 0.3 m. Edge undulations with a wavelength λ, that is significantly larger than the thickness δ of the separated shear layer are identified to enhance the propulsion force during the stable vortex growth and before the vortex detaches. Edge undulation leads to a more turbulent vortex core and a faster vortex growth. The application of different approaches to recover the acting forces from PIV data lead to the conclusion, that the three-dimensionality of the turbulent vortex wake leads to both: a loss of out-of-plane vorticity and an underestimation of the kinetic energy in the vortex

Micro Weather Stations for Mars

A global network of weather stations will be needed to characterize the near-surface environment on Mars. Here, we review the scientific and measurement objectives of this network. We also show how these objectives can be met within the cost-constrained Mars Surveyor Program by augmenting the Mars Pathfinder-derived landers with large numbers of very small (less than 5 liter), low-mass (less than 5 kg), low-power, low-cost Mini-meteorological stations. Each station would include instruments for measuring atmospheric. pressures, temperatures, wind velocities, humidity, and airborne dust abundance. They would also include a data handling, telemetry, power, atmospheric entry, and deployment systems in a rugged package capable of direct entry and a high-impact landing. In this paper, we describe these systems and summarize the data-taking strategies and data volumes needed to achieve the surface meteorology objectives for Mars

Hubble flow variance and the cosmic rest frame

We characterize the radial and angular variance of the Hubble flow in the COMPOSITE sample of 4534 galaxies, on scales in which much of the flow is in the nonlinear regime. With no cosmological assumptions other than the existence of a suitably averaged linear Hubble law, we find with decisive Bayesian evidence (ln B >> 5) that the Hubble constant averaged in independent spherical radial shells is closer to its asymptotic value when referred to the rest frame of the Local Group, rather than the standard rest frame of the Cosmic Microwave Background. An exception occurs for radial shells in the range 40/h-60/h Mpc. Angular averages reveal a dipole structure in the Hubble flow, whose amplitude changes markedly over the range 32/h-62/h Mpc. Whereas the LG frame dipole is initially constant and then decreases significantly, the CMB frame dipole initially decreases but then increases. The map of angular Hubble flow variation in the LG rest frame is found to coincide with that of the residual CMB temperature dipole, with correlation coefficient -0.92. These results are difficult to reconcile with the standard kinematic interpretation of the motion of the Local Group in response to the clustering dipole, but are consistent with a foreground non-kinematic anisotropy in the distance-redshift relation of 0.5% on scales up to 65/h Mpc. Effectively, the differential expansion of space produced by nearby nonlinear structures of local voids and denser walls and filaments cannot be reduced to a local boost. This hypothesis suggests a reinterpretation of bulk flows, which may potentially impact on calibration of supernovae distances, anomalies associated with large angles in the CMB anisotropy spectrum, and the dark flow inferred from the kinematic Sunyaev-Zel'dovich effect. It is consistent with recent studies that find evidence for a non-kinematic dipole in the distribution of distant radio sources.Comment: 37 pages, 9 tables, 13 figures; v2 adds extensive new analysis (including additional subsections, tables, figures); v3 adds a Monte Carlo analysis (with additional table, figure) which further tightens the statistical robustness of the dipole results; v4 adds further clarifications, small corrections, references and discussion of Planck satellite results; v5 typos fixed, matches published versio

Effective Hamiltonian study of excitations in a boson- fermion mixture with attraction between components

An effective Hamiltonian for the Bose subsystem in the mixture of ultracold atomic clouds of bosons and fermions with mutual attractive interaction is used for investigating collective excitation spectrum. The ground state and mode frequencies of the $^{87}$Rb and $^{40}$K mixture are analyzed quantitatively at zero temperature. We find analytically solutions of the hydrodynamics equations in the Thomas- Fermi approximation. We discuss the relation between the onset of collapse and collective modes softening and the dependence of collective oscillations on scattering length and number of boson atoms.Comment: 9 pages, 5 figure

Micro-sensors for in-situ meteorological measurements

Improved in-situ meteorological measurements are needed for monitoring the weather and climate of the terrestrial and Martian atmospheres. We have initiated a program to assess the feasibility and utility of micro-sensors for precise in-situ meteorological measurements in these environments. Sensors are being developed for measuring pressure, temperature, wind velocity, humidity, and aerosol amounts. Silicon micro-machining and large scale integration technologies are being used to make sensors that are small, rugged, lightweight, and require very little power. Our long-term goal is to develop very accurate miniaturized sensors that can be incorporated into complete instrument packages or 'micro weather stations,' and deployed on a variety of platforms. If conventional commercially available silicon production techniques can be used to fabricate these sensor packages, it will eventually be possible to mass-produce them at low cost. For studies of the Earth's troposphere and stratosphere, they could be deployed on aircraft, dropsondes, radiosondes, or autonomous surface stations at remote sites. Improved sensor accuracy and reduced sensor cost are the primary challenges for these applications. For studies of the Martian atmosphere, these sensor packages could be incorporated into the small entry probes and surface landers that are being planned for the Mars Environmental SURvey (MESUR) Mission. That decade-long program will deploy a global network of small stations on the Martian surface for monitoring meteorological and geological processes. Low mass, low power, durability, large dynamic range and calibration stability are the principal challenges for this application. Our progress on each of these sensor types is presented