9,760 research outputs found
Isinglass River Conservation Corridor Project
The New Hampshire Estuaries Project (NHEP) provided a 2.9 million project was a collaboration of Bear-Paw, the Trust for Public Land (TPL), and the Town of Strafford that protected five properties and 868 acres of forest, over one mile of road frontage, more than three miles of frontage on streams and rivers (including more than 1½ miles on the Isinglass River), several ponds, and two historic mill sites. All of these properties are in areas that have been identified as important to protect in the Land Conservation Plan for New Hampshire’s Coastal Watersheds, a Conservation Plan produced by Bear-Paw Regional Greenways, the New Hampshire Wildlife Action Plan
AN EXTENSION OF THE CHAPMAN-FERRARO THEORY OF GEOMAGNETIC STORMS
Extension of chapman-ferraro theory of geomagnetic storm
Bread board float zone experiment system for high purity silicon
A breadboard float zone experimental system has been established at Westech Systems for use by NASA in the float zone experimental area. A used zoner of suitable size and flexibility was acquired and installed with the necessary utilities. Repairs, alignments and modifications were made to provide for dislocation free zoning of silicon. The zoner is capable of studying process parameters used in growing silicon in gravity and is flexible to allow trying of new features that will test concepts of zoning in microgravity. Characterizing the state of the art molten zones of a growing silicon crystal will establish the data base against which improvements of zoning in gravity or growing in microgravity can be compared. 25 mm diameter was chosen as the reference size, since growth in microgravity will be at that diameter or smaller for about the next 6 years. Dislocation free crystals were growtn in the 100 and 111 orientations, using a wide set of growth conditions. The zone shape at one set of conditions was measured, by simultaneously aluminum doping and freezing the zone, lengthwise slabbing and delineating by etching. The whole set of crystals, grown under various conditions, were slabbed, polished and striation etched, revealing the growth interface shape and the periodic and aperiodic natures of the striations
Aging Dynamics of a Fractal Model Gel
Using molecular dynamics computer simulations we investigate the aging
dynamics of a gel. We start from a fractal structure generated by the DLCA-DEF
algorithm, onto which we then impose an interaction potential consisting of a
short-range attraction as well as a long-range repulsion. After relaxing the
system at T=0, we let it evolve at a fixed finite temperature. Depending on the
temperature T we find different scenarios for the aging behavior. For T>0.2 the
fractal structure is unstable and breaks up into small clusters which relax to
equilibrium. For T<0.2 the structure is stable and the dynamics slows down with
increasing waiting time. At intermediate and low T the mean squared
displacement scales as t^{2/3} and we discuss several mechanisms for this
anomalous time dependence. For intermediate T, the self-intermediate scattering
function is given by a compressed exponential at small wave-vectors and by a
stretched exponential at large wave-vectors. In contrast, for low T it is a
stretched exponential for all wave-vectors. This behavior can be traced back to
a subtle interplay between elastic rearrangements, fluctuations of chain-like
filaments, and heterogeneity.Comment: 30 pages, 25 figure
Astrophotonic micro-spectrographs in the era of ELTs
The next generation of Extremely Large Telescopes (ELT), with diameters up to
39 meters, will start opera- tion in the next decade and promises new
challenges in the development of instruments. The growing field of
astrophotonics (the use of photonic technologies in astronomy) can partly solve
this problem by allowing mass production of fully integrated and robust
instruments combining various optical functions, with the potential to reduce
the size, complexity and cost of instruments. In this paper, we focus on
developments in integrated micro-spectrographs and their potential for ELTs. We
take an inventory of the identified technologies currently in development, and
compare the performance of the different concepts. We show that in the current
context of single-mode instruments, integrated spectrographs making use of,
e.g., a photonic lantern can be a solution to reach the desired performance.
However, in the longer term, there is a clear need to develop multimode devices
to improve overall the throughput and sensitivity, while decreasing the
instrument complexity.Comment: 9 pages. 2 figures. Proceeding of SPIE 9147 "Ground-based and
Airborne Instrumentation for Astronomy V
Space-time domain decomposition for advection-diffusion problems in mixed formulations
This paper is concerned with the numerical solution of porous-media flow and
transport problems , i. e. heterogeneous, advection-diffusion problems. Its aim
is to investigate numerical schemes for these problems in which different time
steps can be used in different parts of the domain. Global-in-time,
non-overlapping domain-decomposition methods are coupled with operator
splitting making possible the different treatment of the advection and
diffusion terms. Two domain-decomposition methods are considered: one uses the
time-dependent Steklov--Poincar{\'e} operator and the other uses optimized
Schwarz waveform relaxation (OSWR) based on Robin transmission conditions. For
each method, a mixed formulation of an interface problem on the space-time
interface is derived, and different time grids are employed to adapt to
different time scales in the subdomains. A generalized Neumann-Neumann
preconditioner is proposed for the first method. To illustrate the two methods
numerical results for two-dimensional problems with strong heterogeneities are
presented. These include both academic problems and more realistic prototypes
for simulations for the underground storage of nuclear waste
A quantitative image evaluation study of a concurrent photon amplification treated emulsion
A study was performed to evaluate the effect of concurrent photon amplification (CPA) on Kodak Tri-X Pan emulsion in regard to image quality. The study evaluated detective quantum efficiency (DQE), modulation transfer function (MTF), and information content (IC) as a function of exposure in a comparison between normal exposure and CPA. The results showed CPA to enhance image quality relative to normal exposure at very low exposure levels. As the exposure was increased, normally exposed images became comparable and then exceeded CPA exposures in image quality. The exposure level at which normal exposure became preferential was distinct with each image quality measure
Wave-particle velocities
Shonting (1966, 1967, 1968) has measured a number of ocean-wave particle velocities at Buzzards Bay Entrance Light Station (BBELS) with a ducted current meter…
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