979 research outputs found
Flame retardant polyphosphazenes
Six polyphosphazene compositions were prepared by reaction of three bis-tertiary phosphines with two phenyl-s-triazine derived diazides. All six polyphosphazenes produced were completely characterized, four of them were furthermore subjected to isothermal gravimetric analysis, smoke density measurements, flammability and oxidative thermal degradation testing. The results of the characterization studies indicate that only low molecular weight oligomers, possibly of a cyclic structure, were obtained in the polymerization reactions. Despite this, however, two of the materials showed no weight loss after 96 hr at 200 C, one did not autoignite at 500 C in air, and all four self extinguished when exposed to a flame as soon as contact between flame and resin was lost. The only toxic decomposition products to be concerned about were found to be hydrogen cyanide and benzene. Under the conditions employed it was proven, however, that the quantities of toxic products are greatly reduced if no ignition takes place, e.g., if thermal decomposition proceeds at a sufficiently low rate
Flame retardant polyphosphazenes
Three processes for the preparation of polyphosphazenes were investigated: (1) the reaction of bisphosphines with diazides, (2) the condensation of bisdichlorophosphoranes with diamines; and (3) the treatment of bisphosphines with diamines in the presence of carbon tetrachloride followed by base dehydrohalogenation. All products obtained were of low molecular weight; the degree of polymerization did not exceed twelve repeating units. However, several compositions exhibited good thermal stability. No weight loss was observed up to 390 C when heated in air at 5 C/min. Treatment of bisphosphines with either an excess of a diazide or an excess of a diamine in the presence of carbon tetrachloride resulted in the production of difunctional phosphazenes which were respectively, azido and amino terminated. The reaction of these azido terminated extended monomers with bisphosphines did not produce high molecular weight materials. The bis-aminophosphazene prepared for the first time under this contract was successfully incorporated into a polyimide
Flame resistant nontoxic polymer development
A number of homopolymers, copolymers, and terpolymers were synthesized employing styrene and four derivatives of diphenyl-p-styrylphosphine. The various polymeric compositions were prepared by two processes, (1) monomer bulk polymerizations and (2) substitution of preformed polydiphenyl-p-styrylphosphine. Results indicate that the majority of the compositions exhibit superior melting and flame retardant characteristics as compared to polystyrene, but are inferior in molding and film forming capability. Terpolymerization appears to result in the materials with the best overall combination of properties. Toxicological evaluation of three representative basic compositions in the form of molded washers showed that no mortalities occurred among the test animals exposed to the products of the oxidative thermal decomposition of the three materials
APPROPRIATE STATISTICAL METHODS FOR COMPARING SOURCES OF NUTRITIONAL METHIONINE
Kratzer and Ash(1996) presented Experimentation Science as a process to accomplish the Scientific Method with a complete protocol including relevant statistical design and analyses The first principal to sound Experimentation Science is the principle of Relevance. This is a case study primarily of Relevance in Experimentation Science. In our consulting work we found a so called “performance” design as not relevant because of the use of null hypothesis testing to promote a concept of equivalence. The best alternative involves equivalence testing, more replication and representative-ness. Secondly we found a dose response design for two products where non-linear asymptotic regression is misused in applying Bioassay techniques to estimate a single relative biological efficacy (RBV) because the basic assumption of sameness of mathematical form does not hold. We offer a relevant model which involves predicted differences in the relevant zone of commercial use (Vazquez- Añón, M et al, 2006b, Gonzales-Esquerra et al, 2007)
EXPERIMENTATION SCIENCE: A PROCESS APPROACH FOR THE COMPLETE DESIGN OF AN EXPERIMENT
Experimentation Science is introduced as a process through which the necessary steps of experimental design are all sufficiently addressed. Experimentation Science is defined as a nearly linear process of objective formulation, selection of experimentation unit and decision variable(s), deciding treatment, design and error structure, defining the randomization, statistical analyses and decision procedures, outlining quality control procedures for data collection, and finally analysis, presentation and interpretation of results. The protocol description form (PDF) is introduced as an instrument to guide the implementation and documentation of the Experimentation Science process
System Reliability Testing in Space Simulators
All too often the cost in time and money seriously limits the required testing programs. Scientific personnel accept the challenge of space craft design but are rarely stimulated to design and operate the required testing facilities. The space craft test engineer of today must, of necessity, be an experienced expert in all phases of space technology power-plants, solar arrays, hydraulics, pneumatics, structures, dynamics, ultra-high vacuum, solar effects, etc.
Today ! s space environmental testing procedures and techniques have developed a number of varied and specialized test facilities to insure system reliability of space craft. Of these many types, the most important and essential are the Orbital Simulators. The urgency of our current space efforts has been responsible for great strides in high vacuum equipment techniques and systems used for space simulation.
To review briefly the state-of-the-art and to provide general familiarization with the reliability testing theory, methods and application of the Orbital Simulator for space flights will be presented.
To make an over-all system reliability test, just before the launch—i.e., to find out exactly how the system will behave in orbit space simulators are used
Indium-Gallium Segregation in CuInGaSe: An ab initio based Monte Carlo Study
Thin-film solar cells with CuInGaSe (CIGS) absorber are still
far below their efficiency limit, although lab cells reach already 19.9%. One
important aspect is the homogeneity of the alloy. Large-scale simulations
combining Monte Carlo and density functional calculations show that two phases
coexist in thermal equilibrium below room temperature. Only at higher
temperatures, CIGS becomes more and more a homogeneous alloy. A larger degree
of inhomogeneity for Ga-rich CIGS persists over a wide temperature range, which
may contribute to the low observed efficiency of Ga-rich CIGS solar cells
L-band ATS 5/Orion/S. S. Manhattan marine navigation and communication experiment Final report
L-band signals relayed by synchronous satellite for navigation and data communicatio
Thermal oxidative degradation reactions of perfluoroalklethers
The objective of this contract was to investigate the mechanisms operative in thermal and thermal oxidative degradation of Fomblin Z and hexafluoropropene oxide derived fluids and the effect of alloys and additives upon these processes. The nature of arrangements responsible for the inherent thermal oxidative instability of the Fomblin Z fluids has not been established. It was determined that this behavior was not associated with hydrogen end-groups or peroxy linkages. The degradation rate of these fluids at elevated temperatures in oxidizing atmospheres was found to be dependent on the surface/volume ratio. Once a limiting ratio was reached, a steady rate appeared to be attained. Based on elemental analysis and oxygen consumption data, -CF2OCF2CF2O-, not -CF2CF2O-, is one of the major arrangements present. The action of the M-50 and Ti(4 Al, 4 Mn) alloys was found to be much more drastic in the case of Fomblin Z fluids than that observed for the hexalfuoropropane oxide derived materials. The effectiveness of antioxidation/anticorrosion additives, P-3 and phospha-s-triazine, in the presence of metal alloys was very limited at 316 C; at 288 C the additives arrested almost completely the fluid degradation. The phospha-s-triazine appeared to be at least twice as effective as the P-3 compound; it also protected the coupon better. The Ti(4 Al, 4 Mn) alloy degraded the fluid mainly by chain scission processes; this took place to a much lesser degree with M-50
The leading asymptotic terms of the three-body Coulomb scattering wave function
The asymptotic wave function derived by Alt and Mukhamedzhanov [Phys. Rev. A
47, 2004 (1993)] and Mukhamedzhanov and Lieber [Phys. Rev. A 54, 3078 (1996)]
has been refined in the region where the pair remains close
to each other while the third particle is far away from them
, . The improved
wave function satisfies the Schr\"odinger equation up to the terms of order
, provides the leading asymptotic terms of the
three-body scattering wave function with Coulomb interactions and gives further
insight into the continuum behavior of the three-charged-particle wave function
and helps to obtain scattered wave. This opens up further ways of
solving and analysing the three-body Schr\"odinger equation by numerical means
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