The AF structure of non commutative toroidal Z/4Z orbifolds

For any irrational theta and rational number p/q such that q|qtheta-p|<1, a projection e of trace q|qtheta-p| is constructed in the the irrational rotation algebra A_theta that is invariant under the Fourier transform. (The latter is the order four automorphism U mapped to V, V mapped to U^{-1}, where U, V are the canonical unitaries generating A_theta.) Further, the projection e is approximately central, the cut down algebra eA_theta e contains a Fourier invariant q x q matrix algebra whose unit is e, and the cut downs eUe, eVe are approximately inside the matrix algebra. (In particular, there are Fourier invariant projections of trace k|qtheta-p| for k=1,...,q.) It is also shown that for all theta the crossed product A_theta rtimes Z_4 satisfies the Universal Coefficient Theorem. (Z_4 := Z/4Z.) As a consequence, using the Classification Theorem of G. Elliott and G. Gong for AH-algebras, a theorem of M. Rieffel, and by recent results of H. Lin, we show that A_theta rtimes Z_4 is an AF-algebra for all irrational theta in a dense G_delta.Comment: 35 page

Configuration development study of the X-24C hypersonic research airplane

Bottom line results were made of a three-phase study to determine the feasibility of designing, building, and operating, and maintaining an air-launched high performance aircraft capable of cruising at speeds up to Mach 8 for short durations. The results show that Lockalloy heat-sink structure affords the capability for a 'work-horse' vehicle which can serve as an excellent platform for this research. It was further concluded that the performance of a blended wing body configuration surpassed that of a lifting body design for typical X-24C missions. The cost of a two vehicle program, less engines, B-52 modification and contractor support after delivery, can be kept within $70M (in Jan. 1976 dollars)

Electron-irradiated two-terminal, monolithic InP/Ga0.47In0.53As tandem solar cells and annealing of radiation damage

Radiation damage results from two-terminal monolithic InP/Ga(0.47)In(0.53)As tandem solar cells subject to 1 MeV electron irradiation are presented. Efficiencies greater than 22 percent have been measured by the National Renewable Energy Laboratory from 2x2 sq cm cells at 1 sun, AMO (25 C). The short circuit current density, open circuit voltage and fill factor are found to tolerate the same amount of radiation at low fluences. At high fluence levels, slight differences are observed. Decreasing the base amount of radiation at the Ga(0.47)In(0.53)As bottomcell improved the radiation resistance of J(sub sc) dramatically. This is turn, extended the series current flow through the subcell substantially up to a fluence of 3x10(exp 15) cm(exp -2) compared to 3x10(exp 14) cm(exp -2), as observed previously. The degradation of the maximum power output form tandem device is comparable to that from shallow homojunction (SHJ) InP solar cells, and the mechanism responsible for such degradation is explained in terms of the radiation response of the component cells. Annealing studies revealed that the recovery of the tandem cell response is dictated by the annealing characteristics exhibited by SHJ InP solar cells

The effect of hydrogen dilution on the structure of a-C : H

Two a-C:H samples were prepared using a fast-atom deposition system from acetylene and an acetylene/hydrogen gas mixture. Their structure was investigated using neutron and x-ny diffraction and infrared spectroscopy measurements. Compositional analysis shows that a 1:1 C2H2:H-2 mixture results in a change from a-C-77:H-23 to a-C-79:H-21, i.e. has a very small effect on the composition. The diffraction data also show that the addition of hydrogen to the precursor gas has no significant effect on the average bond distances and angles but shows a small change in the H-C-H and C-C-H correlations between the two samples. However, the infrared data show that there are significant changes in the bonding of hydrogen within the sample-changes which do not affect the average network structure. We observe a decrease in the amount of sp(3) CH2 and CH3 groups, and an increase in the fraction of sp(2) and sp(3) CH groups, with the formation of a second sp(2) CH bonding environment in the hydrogen-diluted sample. Therefore, in addition to providing useful structural information on these a-C:H samples, this set of experiments illustrates very well the complementary nature of the data from diffraction and spectroscopic techniques

A spectroscopic study of the structure of amorphous hydrogenated carbon

A range of amorphous hydrogenated carbon (a-C:H) samples have been studied using inelastic neutron spectroscopy (INS) and Fourier transform infrared (FTIR) spectroscopy. Using these complementary techniques, the bonding environments of both carbon and hydrogen can be probed in some detail, with the INS data providing not only qualitative but also quantitative information. By comparing the data from each of the samples we have been able to examine the effects of different deposition conditions, i.e. precursor gas, deposition energy and deposition method, on the atomic-scale structure of a-C:H

Equilibrium states of the pressure function for products of matrices

Let $\{M_i\}_{i=1}^\ell$ be a non-trivial family of $d\times d$ complex matrices, in the sense that for any $n\in \N$, there exists $i_1... i_n\in \{1,..., \ell\}^n$ such that $M_{i_1}... M_{i_n}\neq {\bf 0}$. Let $P \colon (0,\infty)\to \R$ be the pressure function of $\{M_i\}_{i=1}^\ell$. We show that for each $q>0$, there are at most $d$ ergodic $q$-equilibrium states of $P$, and each of them satisfies certain Gibbs property.Comment: 12 pages. To appear in DCD