Thermal coatings for titanium-aluminum alloys

Titanium aluminides and titanium alloys are candidate materials for use in hot structure and heat-shield components of hypersonic vehicles because of their good strength-to-weight characteristics at elevated temperature. However, in order to utilize their maximum temperature capability, they must be coated to resist oxidation and to have a high total remittance. Also, surface catalysis for recombination of dissociated species in the aerodynamic boundary layer must be minimized. Very thin chemical vapor deposition (CVD) coatings are attractive candidates for this application because of durability and very light weight. To demonstrate this concept, coatings of boron-silicon and aluminum-boron-silicon compositions were applied to the titanium-aluminides alpha2 (Ti-14Al-21Nb), super-alpha2 (Ti-14Al-23-Nb-2V), and gamma (Ti-33Al-6Nb-1Ta) and to the titanium alloy beta-21S (Ti-15Mo-3Al-3Nb-0.2Si). Coated specimens of each alloy were subjected to a set of simulated hypersonic vehicle environmental tests to determine their properties of oxidation resistance, surface catalysis, radiative emittance, and thermal shock resistance. Surface catalysis results should be viewed as relative performance only of the several coating-alloy combinations tested under the specific environmental conditions of the LaRC Hypersonic Materials Environmental Test System (HYMETS) arc-plasma-heated hypersonic wind tunnel. Tests were also conducted to evaluate the hydrogen transport properties of the coatings and any effects of the coating processing itself on fatigue life of the base alloys. Results are presented for three types of coatings, which are as follows: (1) a single layer boron silicon coating, (2) a single layer aluminum-boron-silicon coating, and (3) a multilayer coating consisting of an aluminum-boron-silicon sublayer with a boron-silicon outer layer

Paper Session III-C - Innovative Financing of a Large Space Project

This paper addresses the changes to the Space Frontier Operations, Inc. (SFO) Space Exploration Plan, (SEP) that was initially presented at the 37th. Space Congress in 1999. Progress since last year will be presented briefly and the progress made in finding the correct financing vehicles will be presented in detail. The SFO Space Exploration Project starts off as an international project that will present unique and difficult challenges to both the space and financial communities. The effects of these challenges will be discussed along with their impact to the process of raising capital for a project of this nature. The rationale behind establishing a separate but complimentary corporation will be discussed. The relationship between the commercial corporation and SFO will be delineated. It will be shown that complimentary roles are not only possible but also highly desirable. The way in which the SEP fits into the standard protocols used by the finance industry will be discussed. As the project proceeds to completion the issue of traditional financing with an Initial Public Offering will be addressed along with the possibility of bringing in one or more partners – either commercial or governmental. Finally, the work of the supporting commercial corporation will be presented and the current status of the two corporations will be discussed

Seasonal and geographic variation in the shell microstructure of a salt-marsh bivalve (Geukensia demissa (Dillwyn))

The microstructure of the inner shell layer of Geukensia demissa (Dillwyn) varies with both the season of calcium carbonate deposition (or dissolution) and the latitude of sampled populations. Living specimens (n = 510) were sampled at monthly and, occasionally, biweekly intervals over a 3-year period from a natural intertidal population in Gulf of Maine estuarine waters. Scanning electron microscopic examination of the inner shell layer growth surface and fractured shell sections of the sampled specimens suggests that the observed structural changes reflect seasonal cycles of aragonite deposition and dissolution. Discrete nacreous tablets generally are deposited during the warmer months of the year from May through September. During the remaining months of the year, varying degrees of shell dissolution are apparent from ultrastructural examination of the inner shell layer growth surface and fractured shell sections. Additional specimens (n = 285) were sampled during various seasons from six geographically separated populations from Prince Edward Island, Canada to Cape Kennedy, Florida, USA. Examination of acetate peel replicas and polished thin sections of shells from northern populations has revealed the presence of three distinct types of aragonitic microstructure (granular, simple prismatic, and nacre), with an increased percentage of granular structure relative to that present in shells from more southern populations. Granular microstructure is absent in shells from North Carolina and Florida populations; in the inner shell layer of specimens from these southern localities, extensive regions of nacre alternate with horizons of simple prismatic aragonite. It is suggested that area percentages of the various microstructures (particularly granular), when viewed in consistently-oriented antero-posterior shell sections, may be highly correlated with mean annual seawater temperatures. Ecological and paleoecological applications of the observed microstructural changes in the inner shell layer of this species include temporal and spatial temperature gradient reconstructions, as well as analytical studies of demographic (and individual organism) growth rates and age structure

An X-Ray Spectroscopic Study of the SMC X-1/Sk 160 System

We have investigated the composition and distribution of the wind of Sk 160, the supergiant companion of the X-ray star SMC X-1, by comparing an X-ray spectrum of the source, obtained with the ASCA observatory, during an eclipse with the computed spectra of reprocessed radiation from circumstellar matter with various density distributions. We show that the metal abundance in the wind of Sk 160 is no greater than a few tenths of solar, as has been determined for other objects in the Magellanic Clouds. We also show that the observed X-ray spectrum is not consistent with the density distributions of circumstellar matter of the spherically symmetric form derived for line-driven winds, nor with the density distribution derived from a hydrodynamic simulation of the X-ray perturbed and line-driven wind by Blondin & Woo (1995).Comment: 35 pages including 16 figures, uses AASTeX v5.0.2, accepted to Ap

Penetration In Granite By Jets From Shaped-charge Liners Of Six Materials

A new application of theory for three-dimensional collapse of conical liners shows why the two-dimensional analysis may offer a good approximation. Shaped-charge design parameters and rock target properties were investigated to determine their effects on penetration and breakage. Several metals, liner thicknesses, cone angles and standoff ranges for each were investigated. Effective standoff is greater for aluminum than more dense metals. Jets from the 60° monel, brass and steel liners gave the deepest penetration in granite. Jets from copper and brass liners gave equal penetration for 42° apex angles. Liners containing zinc produced small slugs or none at all. The holes in the granite were uniform and approximated right circular cones. Jet penetration velocities into granite varied from a maximum of 10,000 m/sec to a minimum of 2000 m/sec for the most effective metal jet. © 1973

Dimethyl 7a-carbonyl-2-meth­oxy-7a,7a-bis­(triphenyl­phosphino)-7a-ruthena-1-benzofuran-4,7-dicarboxyl­ate

The crystal structure of the title compound, [Ru(C12H12O6)(C18H15P)2(CO)], confirms its formulation as a ruthenabenzofuran, with a slightly distorted octa­hedral coordination environment at the RuII ion, and mutually trans triphenyl­phosphine ligands. The metallabicyclic ring system is essentially planar (maximum deviation 0.059 Å)

Marketing New England poultry, Station Bulletin, no.475

The Bulletin is a publication of the New Hampshire Agricultural Experiment Station, College of Life Sciences and Agriculture, University of New Hampshire, Durham, New Hampshire

Inexpensive and Portable System for Dexterous High-Density Myoelectric Control of Multiarticulate Prostheses

Multiarticulate bionic arms are now capable of mimicking the endogenous movements of the human hand. 3D-printing has reduced the cost of prosthetic hands themselves, but there is currently no low-cost alternative to dexterous electromyographic (EMG) control systems. To address this need, we developed an inexpensive (~$675) and portable EMG control system by integrating low-cost microcontrollers with an EMG acquisition device. We validated signal acquisition by comparing the signal-to-noise ratio (SNR) of our system with that of a high-end research-grade system. We also demonstrate the ability to use the low-cost control system for proportional and independent control of various prosthetic hands in real-time. We found that the SNR of the low-cost control system was statistically no worse than 44% of the SNR of a research-grade control system. The RMSEs of predicted hand movements (from a modified Kalman filter) were typically a few percent better than, and not more than 6% worse than, RMSEs of a research-grade system for up to six degrees of freedom when only relatively few (six) EMG electrodes were used. However, RMSEs were generally higher than RMSEs of research-grade systems that utilize considerably more (32) EMG electrodes, guiding future work towards increasing electrode count. Successful instantiation of this low-cost control system constitutes an important step towards the commercialization and wide-spread availability of dexterous bionic hands.Comment: IEEE EMBC 202