Continuous fiber ceramic matrix composites for heat engine components

High strength at elevated temperatures, low density, resistance to wear, and abundance of nonstrategic raw materials make structural ceramics attractive for advanced heat engine applications. Unfortunately, ceramics have a low fracture toughness and fail catastrophically because of overload, impact, and contact stresses. Ceramic matrix composites provide the means to achieve improved fracture toughness while retaining desirable characteristics, such as high strength and low density. Materials scientists and engineers are trying to develop the ideal fibers and matrices to achieve the optimum ceramic matrix composite properties. A need exists for the development of failure models for the design of ceramic matrix composite heat engine components. Phenomenological failure models are currently the most frequently used in industry, but they are deterministic and do not adequately describe ceramic matrix composite behavior. Semi-empirical models were proposed, which relate the failure of notched composite laminates to the stress a characteristic distance away from the notch. Shear lag models describe composite failure modes at the micromechanics level. The enhanced matrix cracking stress occurs at the same applied stress level predicted by the two models of steady state cracking. Finally, statistical models take into consideration the distribution in composite failure strength. The intent is to develop these models into computer algorithms for the failure analysis of ceramic matrix composites under monotonically increasing loads. The algorithms will be included in a postprocessor to general purpose finite element programs

An application of multivariable design techniques to the control of the national transonic facility

The digital versions of optimal linear regulator theory and eigenvalue placement theory are applied to the Mach number control loop of the National Transonic Facility cryogenic wind tunnel. The control laws developed are evaluated on a nonlinear simulation of the tunnel process for a typical est condition and are found to significantly reduce the open loop time required to achieve a Mach number set point

Threat expert system technology advisor

A prototype expert system was developed to determine the feasibility of using expert system technology to enhance the performance and survivability of helicopter pilots in a combat threat environment while flying NOE (Nap of the Earth) missions. The basis for the concept is the potential of using an Expert System Advisor to reduce the extreme overloading of the pilot who flies NOE mission below treetop level at approximately 40 knots while performing several other functions. The ultimate goal is to develop a Threat Expert System Advisor which provides threat information and advice that are better than even a highly experienced copilot. The results clearly show that the NOE pilot needs all the help in decision aiding and threat situation awareness that he can get. It clearly shows that heuristics are important and that an expert system for combat NOE helicopter missions can be of great help to the pilot in complex threat situations and in making decisions

The Identification and Characterisation of Novel Suppressors of DNA Replication Stress

Replication stress is present in cancers cells at higher than normal levels due to the increased proliferation caused by oncogene activation. This results in elevated levels of phosphorylated RPA2 (pRPA2) and DNA damage, which can ultimately result in genetic instability. By inhibiting suppressors of replication stress, it may be possible to target this cancer-specific phenotype to selectively kill tumour cells. Attempts were therefore made to develop a high throughput whole genome RNAi screen to detect increased endogenous levels of pRPA2 foci formation following gene knockdown, however, this proved unsuccessful. As a contingency measure a selected panel of kinases, identified as putative replication stress suppressors and potential druggable targets, were assessed for their ability to induce pRPA2 foci following gene knockdown. This approach identified several hits, which were then evaluated for their ability to preferentially kill cells lacking p53 signalling or overexpressing several clinically relevant oncogenes (Cyclin E, H-RAS and MYC-N). They were also assessed for their ability to potentiate the effects of the replication stress inducing drugs Gemcitabine and 5-Flurouracil as well as the PARP inhibitor Olaparib. In addition, the putative DNA damage repair factor CCDC15, which has been hypothesised to act in the resolution of replication impeding lesions, was also investigated as a potential replication stress suppressor. However, it does not appear to modulate DNA replication stress as its loss does not induce pRPA2 and the formation of DNA damage following its knockdown is independent of entry into S phase. Interestingly, depletion of CCDC15 sensitised certain cell lines to the effects of DNA crosslinking agents. Furthermore, knockdown of CCDC15 also slightly increased the formation of endogenous FANCD2 foci, but not in cells treated with DNA crosslinking agents. However, CCDC15-depleted cells exhibited delayed formation and resolution of RAD51 foci following DNA damage, which were not due to perturbations in cell cycle progression. Although CCDC15 appears to have little effect on the cell cycle distribution of cycling cells, its loss potentially delays re-entry into the cycle of cells paused in G1 phase

The Risetime of Nearby Type Ia Supernovae

We present calibrated photometric measurements of the earliest detections of nearby type Ia supernovae (SNe Ia). The set of ~30 new, unfiltered CCD observations delineate the early rise behavior of SNe Ia > 18 to 10 days before maximum. Using simple empirical models, we demonstrate the strong correlation between the risetime (i.e., the time between explosion and maximum), the post-rise light-curve shape, and the peak luminosity. Using a variety of light-curve shape methods, we find the risetime to B maximum for a SN Ia with Delta m15(B)=1.1 mag and peak M_V=-19.45 mag to be 19.5+/-0.2 days. We find that the peak brightness of SNe Ia is correlated with their risetime; SNe Ia which are 0.10 mag brighter at peak in the B-band require 0.80+/-0.05 days longer to reach maximum light. We determine the effects of several possible sources of systematic errors, but none of these significantly impacts the inferred risetime. Constraints on SN Ia progenitor systems and explosion models are derived from a comparison between the observed and theoretical predictions of the risetime.Comment: Submitted to the Astronomical Journal, 24 pages, 7 figure

The effects of multiple aerospace environmental stressors on human performance

An extended Fitt's law paradigm reaction time (RT) task was used to evaluate the effects of acceleration on human performance in the Dynamic Environment Simulator (DES) at Armstrong Laboratory, Wright-Patterson AFB, Ohio. This effort was combined with an evaluation of the standard CSU-13 P anti-gravity suit versus three configurations of a 'retrograde inflation anti-G suit'. Results indicated that RT and error rates increased 17 percent and 14 percent respectively from baseline to the end of the simulated aerial combat maneuver and that the most common error was pressing too few buttons

Professor Justice Ginsburg: Justice Ginsburg\u27s Love of Procedure and Jurisdiction

As two of Justice Ginsburg’s former clerks, we are keenly aware of the popular image of the Justice as the “Notorious RBG”: the champion of women’s rights and the forceful dissenter, strongly disputing the Roberts Court’s conservative turn and articulating the case for the liberal New Deal constitutional vision, with its commitment to protecting individual rights and broad view of national power. This she did, powerfully and eloquently. But to understand Justice Ginsburg – the person, the Justice, and her jurisprudence – it is also critical to account for her role as the Supreme Court’s leading civil procedure and federal jurisdiction maven