Small-scale Objects Research Articles

A RING MEDIAN FILTER FOR DIGITAL IMAGES

ABSTRACT The ring filter is defined as a median filter which assigns weight only to select pixels in an annulus. Its advantage is that it has a sharply-defined scale length; that is, all objects with a scale-size less than the radius of the ring are filtered and replaced by the local background level. It provides a fast, simple and intuitive method to remove the small-scale objects (independent of morphology) from a digital image, leaving behind the large-scale objects and overall light gradients. The ring filter is much faster than the more commonly used filled-box median filter, and completes in one or two passes what previously required a long iterative procedure. Several examples of its use are presented.

Laser speckle photography in heat transfer studies

Laser speckle photography, as a technique making use of the displacement of optical speckle by refraction as an information carrier, has recently been used to measure fluid density, temperature, and heat transfer. The concept of laser speckle photography and the principles of measuring the temperature gradient field are briefly described, including the formation of laser speckle and its displacement, six kinds of recording systems, and two methods for reconstructing a specklegram. The major advantages of the laser speckle photography method for heat transfer study in comparison with interferometric methods are listed and discussed. Finally, many applications of laser speckle photography in the study of heat transfer are given, including cases of natural convection along a vertical plate, measurements of the axisymmetric temperature field of a flame, heat tranfser in channel natural convection and verification of thermal drag phenomena, and heat transfer of small-scale objects.

Laser speckle photography for heat transfer

ABSTRACT Laser speckle photography, as a technique making use of the displacement of optical speckle by refraction as information carrier, is recently used to measure fluid density, temperature and heat transfer. The concept of laser speckle photography and the measuring principle of temperature gradient field are briefly described. They cover the formation of laser speckle and its displacement, six kinds of record system and two reconstruction methods of specklegram. Major advantages of the laser speckle photography method for heat transfer study over interferometric methods are listed and discussed. Finally, many applications of laser speckle photography in heat transfer study are given, including natural convection along a vertical plate; measurements of axisymmetric temperature field of a flame; heat transfer in channel natural convection and verification of thermal drag phenomena; and heat transfer of small-scale objects etc.

The Brummer Collection of Medieval Art

The Brummer Collection of Medieval Art in the Duke University Museum of Art is one of the finest to be found in any American university museum. It is remarkable for its breadth and the variety of objects represented, with works varying in scale from monumental stone pieces to small-scale objects in wood, ivory, or metal, and ranging from the seventh to eighth centuries through the sixteenth century. This fine catalog makes available for the first time this rich but little-known collection. Five studies by leading art scholars focus on key works in the collection and contribute to a new understanding of the origins of many of the pieces. Two introductory essays comment on the character of the collection as a whole, its acquisition by Duke University, and its conservation. Finally, the catalog section discusses the more important pieces in the collection and is followed by a checklist of entries and smaller photographs of all other objects. Contributors. Ilene H. Forsyth, Jean M. French, Dorothy F. Glass, Dieter Kimpel, Jill Meredith, Linda S. Roundhill

Using the reversability of the peltier effect to reduce the heat-scattering surfaces of thermal cooling batteries

We propose and analyze a method for significant reduction in the area of heat scattering surfaces in thermal cooling batteries, where the latter are used to cool small-scale objects.

Spatial Distribution of Quasars

The distribution of quasars has become one of the most interesting problems in observational cosmology. This is due mainly to the development of theory of the formation of large scale structure in the universe. In recent years, several scenarios of clustering have been proposed. In the adiabatic case, the clustering process is from larger scales to smaller ones, i.e., the first systems to form out would be on the scale of superclusters, then these systems fragment to form smaller scale systems such as galaxies. In the isothermal case, the clustering is from smaller scales to larger ones, namely, galaxies condense out at first and larger scale systems, such as clusters and superclusters, then form later via hierachical build-up processes. In the universe contain two components, the scenario of clustering might be different from both standard adiabatic and isothermal cases(1). According to this new scenario, there should be two kinds of small scale objects, one is formed due to fragment of larger scale systems, another is formed before large scale systems form.

SS 433 as a prototype of astrophysical jets

SS 433, a small-scale object within our Galaxy having cool gas within its jets, offers unprecedented clues to the nature of astrophysical jets in general. The jets are probably accelerated by radiation pressure and partially collimated by nozzles, formed where a dense accretion disk encounters heating and high pressures close to the central source. Interaction with an ambient medium, perhaps a stellar wind, is responsible for the line emission. Constraints on the line emissivity of the gas indicate that the jets are composed of many dense (n/sub e/approx. =10/sup 13/ cm/sup -3/), relatively cool Tapprox. =10/sup 4/ K condensations, with a filling factor of epsilonapprox. =10/sup -4/; these values are probably caused by thermal instability near the nozzle and contained by thermal pressure of hot (Tapprox. =10/sup 8/ K) gas in the jet. Evaporation of the condensations by thermal conduction may determine the length of the line-emitting portion of each jet.