Vaporization and decomposition kinetics of candidate re-entry blackout suppressants in low-pressure flames

Measurement of thermal accommodation coefficients between liquids and high temperature gases in low pressure reentry communications blackout interval

Measured limits to contamination of optical surfaces by elastomers in vacuum

We have monitored the reflectivity of mirrors that were exposed to a fluoroelastomer (3M-Fluorel 2176) and a room-temperature vulcanizing silicone rubber (RTV-615) in vacuum. The 95% confidence limit on the decrease of mirror reflectivities was less than 0.35 ppm/week for Fluorel and <0.29 ppm@week for RTV-615

Polarized-interferometer feasibility study

The feasibility of using a polarized-interferometer system as a rendezvous and docking sensor for two cooperating spacecraft was studied. The polarized interferometer is a radio frequency system for long range, real time determination of relative position and attitude. Range is determined by round trip signal timing. Direction is determined by radio interferometry. Relative roll is determined from signal polarization. Each spacecraft is equipped with a transponder and an antenna array. The antenna arrays consist of four crossed dipoles that can transmit or receive either circularly or linearly polarized signals. The active spacecraft is equipped with a sophisticated transponder and makes all measurements. The transponder on the passive spacecraft is a relatively simple repeater. An initialization algorithm is developed to estimate position and attitude without any a priori information. A tracking algorithm based upon minimum variance linear estimators is also developed. Techniques to simplify the transponder on the passive spacecraft are investigated and a suitable configuration is determined. A multiple carrier CW signal format is selected. The dependence of range accuracy and ambiguity resolution error probability are derived and used to design a candidate system. The validity of the design and the feasibility of the polarized interferometer concept are verified by simulation

The first direct detection of gravitational waves opens a vast new frontier in astronomy

The first direct detection of gravitational waves (GWs), announced on 11 February 2016, has opened a vast new frontier in astronomy. Albert Einstein predicted the existence of these waves about a century ago as a consequence of his general theory of relativity. Radio astronomy observations of the binary pulsar system PSR 1913 + 16 over a 20 year period beginning in 1975 provided strong observational evidence that gravitational waves carried energy away from the orbits of neutron stars at precisely the level predicted by general relativity (GR). This relentless conversion of orbital energy into gravitational wave energy causes binary orbits to decay until the objects eventually collide and merge. The frontier of precision measurement science, using laser interferometers, was pushed for more than four decades to achieve this first direct detection, marking a milestone in experimental physics and engineering. Even more significantly, this milestone also opens a new window onto our universe and a completely new kind of astronomy to explore

Comparison of regional blood flow values measured by radioactive and fluorescent microspheres

Fluorescent microspheres (FM) have become an attractive alternative to radioactive microspheres (RM) for the measurement of regional blood flow (RBF). The aim of the present study was to investigate the comparability of both methods by measuring RBF with FM and RM. Eight anaesthetised pigs received simultaneous, left atrial injections of FM and RM with a diameter of 15 mum at six different time points. Blood reference samples were collected from the descending aorta. RBF was determined in tissue samples of the myocardium, spleen and kidneys of all 8 animals. After radioactivity of the tissue samples was determined, the samples were processed automatically for measuring fluorescence using a recently developed filter device (SPU). RBF was calculated with both the isotope and spectrometric data of both methods for each sample resulting in a total of 10,512 blood flow values. The comparison of the RBF values yielded high linear correlation (mean r(2) = 0.95 +/- 0.03 to 0.97 +/- 0.02) and excellent agreement (bias 5.4-6.7%, precision 9.9-16.5%) of both methods. Our results indicate the validity of MS and of the automated tissue processing technique by means of the SPU. Copyright (C) 2002 S. Karger AG, Basel

The Random Bit Complexity of Mobile Robots Scattering

We consider the problem of scattering $n$ robots in a two dimensional continuous space. As this problem is impossible to solve in a deterministic manner, all solutions must be probabilistic. We investigate the amount of randomness (that is, the number of random bits used by the robots) that is required to achieve scattering. We first prove that $n \log n$ random bits are necessary to scatter $n$ robots in any setting. Also, we give a sufficient condition for a scattering algorithm to be random bit optimal. As it turns out that previous solutions for scattering satisfy our condition, they are hence proved random bit optimal for the scattering problem. Then, we investigate the time complexity of scattering when strong multiplicity detection is not available. We prove that such algorithms cannot converge in constant time in the general case and in $o(\log \log n)$ rounds for random bits optimal scattering algorithms. However, we present a family of scattering algorithms that converge as fast as needed without using multiplicity detection. Also, we put forward a specific protocol of this family that is random bit optimal ($n \log n$ random bits are used) and time optimal ($\log \log n$ rounds are used). This improves the time complexity of previous results in the same setting by a $\log n$ factor. Aside from characterizing the random bit complexity of mobile robot scattering, our study also closes its time complexity gap with and without strong multiplicity detection (that is, $O(1)$ time complexity is only achievable when strong multiplicity detection is available, and it is possible to approach it as needed otherwise)

Tumbleweeds and airborne gravitational noise sources for LIGO

Gravitational-wave detectors are sensitive not only to astrophysical gravitational waves, but also to the fluctuating Newtonian gravitational forces of moving masses in the ground and air around the detector. This paper studies the gravitational effects of density perturbations in the atmosphere, and from massive airborne objects near the detector. These effects were previously considered by Saulson; in this paper I revisit these phenomena, considering transient atmospheric shocks, and the effects of sound waves or objects colliding with the ground or buildings around the test masses. I also consider temperature perturbations advected past the detector as a source of gravitational noise. I find that the gravitational noise background is below the expected noise floor even of advanced interferometric detectors, although only by an order of magnitude for temperature perturbations carried along turbulent streamlines. I also find that transient shockwaves in the atmosphere could potentially produce large spurious signals, with signal-to-noise ratios in the hundreds in an advanced interferometric detector. These signals could be vetoed by means of acoustic sensors outside of the buildings. Massive wind-borne objects such as tumbleweeds could also produce gravitational signals with signal-to-noise ratios in the hundreds if they collide with the interferometer buildings, so it may be necessary to build fences preventing such objects from approaching within about 30m of the test masses.Comment: 15 pages, 10 PostScript figures, uses REVTeX4.cls and epsfig.st

Electromagnetic multipole theory for optical nanomaterials

Optical properties of natural or designed materials are determined by the electromagnetic multipole moments that light can excite in the constituent particles. In this work we present an approach to calculate the multipole excitations in arbitrary arrays of nanoscatterers in a dielectric host medium. We introduce a simple and illustrative multipole decomposition of the electric currents excited in the scatterers and link this decomposition to the classical multipole expansion of the scattered field. In particular, we find that completely different multipoles can produce identical scattered fields. The presented multipole theory can be used as a basis for the design and characterization of optical nanomaterials

Industrija čelika u novim članicama EU u usporedbi s globalnim trendovima

Accession of the metallurgically significant countries of the Central and Eastern Europe to the EU in 2004 was conditioned by fulfilling the Restructuring Programs as the foundation for achievement of competitiveness and guarancy of viability. The Restructuring Programs, which fulfilling and regular monitoring had lasted 5 years, demonstrated the right of the significant position of the steel industry in the new EU members, especially in Poland, Czech Republic, Slovakia, and in Hungary. The objective of the article is to point to the key elements in context of steel industry global trends, regarding either production or especially utility values and total consumption. In this connection, privatization took an important role too.Prinos metalurgije glavnih zemalja Srednje i Istočne Europe u EU u 2004. je bilo ostvarenje restrukturiranja programa kao temelj za postizanje konkurentnosti i jamstvo opstanka. Restrukturiranje programa, provedba i redovito praćenj za 5 godina opravdalo je značajno mjesto u industriji čelika u novim zemljama EU, naročito u Poljskoj, Češkoj, Slovačkoj i Mađarskoj. Ovaj članak ima za cilj istaknuti ključne elemente u razvojnom konextu industrija čelika u svijetu, kako u pogledu proizvodnje, a posebice u odnosu na kvalitete i ukupnu potrošnju. Važan element u tom pogledu, nastavak privatizacije