Hot Isostatic Pressing Technology for Defence and Space Applications

Hot isostatic pressing (HIP) technology has been established for the development of AISI-304 stainless steel and nickel base superalloy Inconel 718 integral turbine rotors, for liquid propulsion engine of Prithvi missile, and cryoengine of geostationary satellite launch vehicle (GSLV), respectively. Before making the full size rotors, the structure – property relationships in hot isostatic pressed (HIPed) 304 stainless steel and superalloy 718 were established. The HIPed steel and superalloy have shown near 100 per cent theoretical density, homogeneous, and fine grained microstructure. Their mechanical properties were found to be in agreement with those specified for the integral turbine rotors and hence, development of full size near net shaped integral turbine rotors was undertaken. The HIPed steel rotors subjected to the static engine tests have shown a satisfactory performance, and therefore a large number of rotors could be produced to fulfill the requirement of target labs. The HIP technology for the integral turbine rotors was found to be cost effective (about 50 per cent) over the conventional fabrication method which involves forging, machining, and welding of blades to the disk. The processing, structure, and properties of the HIPed 304 stainless steel and superalloy 718 in relation to the performance of integral turbine rotors for missile and space vehicle applications are discussed in this paper.Defence Science Journal, 2012, 62(1), pp.73-80, DOI:http://dx.doi.org/10.14429/dsj.62.37

Observer’s Galvanic Skin Response for Discriminating Real from Fake Smiles

This paper demonstrates a system to discriminate real from fake smiles with high accuracy by sensing observers’ galvanic skin response (GSR). GSR signals are recorded from 10 observers, while they are watching 5 real and 5 posed or acted smile video stimuli. We investigate the effect of various feature selection methods on processed GSR signals (recorded features) and computed features (extracted features) from the processed GSR signals, by measuring classification performance using three different classifiers. A leave-one-observer-out process is implemented to reliably measure classification accuracy. It is found that simple neural network (NN) using random subset feature selection (RSFS) based on extracted features outperforms all other cases, with 96.5% classification accuracy on our two classes of smiles (real vs. fake). The high accuracy highlights the potential of this system for use in the future for discriminating observers’ reactions to authentic emotional stimuli in settings such as advertising and tutoring systems

Measurement of Turbulent Flame Speeds of Hydrogen and Natural Gas Blends (C1-C5 Alkanes) using a Newly Developed Fan-Stirred Vessel

A fan-stirred flame speed vessel was developed at Texas A&M University to conduct turbulent combustion studies. Four high-speed impellers were installed in a central-symmetric pattern at the central circumference of an existing cylindrical laminar flame bomb. The fans generated homogeneous and isotropic turbulence with negligible mean flow (< 10% u′) at the vessel center, and flames up to 12.7 cm in diameter can be measured. The fan designs were optimized using particle image velocimetry inside a Plexiglas model of the vessel. The uniformity of the flow fields was verified using spatial uniformity maps, two-point correlations, and the energy spectra. Additionally, the capability to independently vary the intensity level and the integral length scale was developed. Where the former changed with fan speeds, increasing the blade pitch angle of the impeller decreased the integral length scale. Turbulent flame speeds of fuels that are of topical interest to gas turbines were measured in the fan-stirred bomb. Schlieren photography was used to visualize the flame growth under constant-pressure conditions, and the captured images were processed using an edge-detection code developed in-house. The equivalent-circle-area method was used to determine the flame radii. The shot-to-shot variability was minimal, which resulted in a low experimental scatter close to 10 cm/s. The flame speeds increased with radius due to flame acceleration. Effective turbulent intensity levels were estimated which increased progressively with flame radius. A systematic approach was followed to determine the effects of hydrogen addition on the turbulent displacement speeds of alkanes (C1-C3). Particularly, a natural gas surrogate (NG2) containing large amounts of C2+ hydrocarbons (>20%) was studied. Turbulent displacements were higher for alkane mixtures with Lewis number below unity than those with Le>1. NG2 and methane gave near-identical turbulent displacement speeds consistent with the laminar flame speed trends. Similar trends in displacement speeds were observed for blends of NG2/H_(2) and CH_(4)/H_(2), thus validating the newly established experimental technique. Additionally, turbulent flame speeds of hydrogen and a generic, high-hydrogen-content syngas blend (50:50 H_(2):CO) were studied. The wide range of laminar flame speeds explored herein revealed significantly different flame surface features between the various regimes of turbulent combustion

Performance Evaluation of Reverberant Chamber Background Noise Levels

An improved test system for acoustical rating of air-movement devices was installed and evaluated at the Riverside Energy Efficiency Laboratory at Texas A&M University where measurements of sound pressure levels were carried out using an array of six microphones instead of the existing rotating boom- microphone setup. The new array setup did not generate any inherent transient noise peaks, which provided adequate signal-to-noise ratios suitable for low sone fan testing. The reverberation chamber was qualified for broad-band testing in the frequency range 50 Hz to 10 kHz. Important acoustical parameters, namely, reverberation time and natural modes of the chamber, were determined. The purpose of this study was to identify potential background noise sources by computing the coherence functions between microphones placed outside the chamber and a microphone placed within the chamber. No strong coherence was observed, thus indicating adequate sound attenuation characteristics of the chamber walls. The effect of background noise levels on the loudness rating of fans was evaluated. A low sone fan and a louder fan (loudness greater than one sone) were tested during night time when the background noise is the least and during daytime and with the air conditioners running (high background noise level). While both fan types showed no significant change in loudness when tested during daytime and during the night, accurate ratings were not obtained with the air-conditioners running due to inconsistent spectrum. Finally, it was observed that with the six decibels separation requirement between the fan and background noise spectra for a low sone fan, at very low frequencies (below 63 Hz), despite inadequate fan- background separation, the loudness rating of the fan does not change as the minimum perceived loudness at these frequencies is very high. At very high frequencies (greater than 5 kHz), the fan does not generate any noise and hence the fan and the background noise sound pressure levels are very close to each other

On the (parameterized) complexity of recognizing well-covered (r,l)-graphs.

An (r,ℓ)(r,ℓ)-partition of a graph G is a partition of its vertex set into r independent sets and ℓℓ cliques. A graph is (r,ℓ)(r,ℓ) if it admits an (r,ℓ)(r,ℓ)-partition. A graph is well-covered if every maximal independent set is also maximum. A graph is (r,ℓ)(r,ℓ)-well-covered if it is both (r,ℓ)(r,ℓ) and well-covered. In this paper we consider two different decision problems. In the (r,ℓ)(r,ℓ)-Well-Covered Graph problem ((r,ℓ)(r,ℓ) wcg for short), we are given a graph G, and the question is whether G is an (r,ℓ)(r,ℓ)-well-covered graph. In the Well-Covered (r,ℓ)(r,ℓ)-Graph problem (wc (r,ℓ)(r,ℓ) g for short), we are given an (r,ℓ)(r,ℓ)-graph G together with an (r,ℓ)(r,ℓ)-partition of V(G) into r independent sets and ℓℓ cliques, and the question is whether G is well-covered. We classify most of these problems into P, coNP-complete, NP-complete, NP-hard, or coNP-hard. Only the cases wc(r, 0)g for r≥3r≥3 remain open. In addition, we consider the parameterized complexity of these problems for several choices of parameters, such as the size αα of a maximum independent set of the input graph, its neighborhood diversity, or the number ℓℓ of cliques in an (r,ℓ)(r,ℓ)-partition. In particular, we show that the parameterized problem of deciding whether a general graph is well-covered parameterized by αα can be reduced to the wc (0,ℓ)(0,ℓ) g problem parameterized by ℓℓ, and we prove that this latter problem is in XP but does not admit polynomial kernels unless coNP⊆NP/polycoNP⊆NP/poly

β−Diketiminate Ligands as Supports for Alkaline Earth and Aluminum Complexes: Synthesis, Characterization, and Reactivity Studies

Meine Doktorarbeit handelt von der Synthese, Charakterisierung und Reaktivitätsuntersuchungen von Komplexen der nicht toxischen Metalle der 2. Hauptgruppe (Magnesium, Calcium und Strontium) sowie Aluminium bei der Benutzung des β-Diketiminaten Ligandens L (L = CH{(CMe)(2,6-iPr2C6H3N)}2). Die Highlights stellen die Synthese von in Kohlenwasserstoffen löslichen Amide, Hydroxide, Oxide, Chloride und Fluoride von Strontium da. Außerdem wurden Heterobimetallische Komplexe des Strontiums durch Umpolung zu einer Säure hergestellt. Des Weiteren wurden Acetylide und Jodide von Calcium und Strontium dargestellt, speziell eine [I-Ca-I-Ca-I-Ca-I]2+ Kette stabilisiert durch zwei chelatisierende β-Diketiminat-Liganden. Außerdem die Synthese von heterobimetallischen Hydrid-Komplexen von Magnesium und Aluminium; Synthese von Heterobimetallischen Komplexen die einen Zr-O-Sr Strukturtyp tragen durch die Nutzung von Zirconiumhydroxiden und Strontiumamiden; Die Synthese von N-Hetrocyclischen Aluminiumkomplexen; N-H Bindungsspaltung von Ammoniak an einem Aluminium(III)-Zentrum; Synthese von Heteroleptischen Aluminiumkomplexen; Cycloadditionsreaktion eines Ketons mit einem N-Heterocyclischen Aluminiumkomplexen und Konstruktion von heterobimetallischen Komplexen die Aluminium ohne eine Sauerstoffbrücke enthielten

Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial

Background Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy

Ultrasound-enhanced ocular delivery of dexamethasone sodium phosphate: An in vivo study

Background The eye\u27s unique anatomy and its physiological and anatomical barriers can limit effective drug delivery into the eye. Methods An in vivo study was designed to determine the effectiveness and safety of ultrasound application in enhancing drug delivery in a rabbit model. Permeability of a steroid ophthalmic drug, dexamethasone sodium phosphate, was investigated in ultrasound- and sham-treated cases. For this study, an eye cup filled with dexamethasone sodium phosphate was placed on the cornea. Ultrasound was applied at intensity of 0.8 W/cm2 and frequency of 400 or 600 kHz for 5 min. The drug concentration in aqueous humor samples, collected 90 min after the treatment, was determined using chromatography methods. Light microscopy observations were done to determine the structural changes in the cornea as a result of ultrasound application. Results An increase in drug concentration in aqueous humor samples of 2.8 times (p \u3c 0.05) with ultrasound application at 400 kHz and 2.4 times (p \u3c 0.01) with ultrasound application at 600 kHz was observed as compared to sham-treated samples. Histological analysis showed that the structural changes in the corneas exposed to ultrasound predominantly consisted of minor epithelial disorganization. Conclusions Ultrasound application enhanced the delivery of an anti-inflammatory ocular drug, dexamethasone sodium phosphate, through the cornea in vivo. Ultrasound-enhanced ocular drug delivery appears to be a promising area of research with a potential future application in a clinical setting

PaLM: Scaling Language Modeling with Pathways

Large language models have been shown to achieve remarkable performance across a variety of natural language tasks using few-shot learning, which drastically reduces the number of task-specific training examples needed to adapt the model to a particular application. To further our understanding of the impact of scale on few-shot learning, we trained a 540-billion parameter, densely activated, Transformer language model, which we call Pathways Language Model PaLM. We trained PaLM on 6144 TPU v4 chips using Pathways, a new ML system which enables highly efficient training across multiple TPU Pods. We demonstrate continued benefits of scaling by achieving state-of-the-art few-shot learning results on hundreds of language understanding and generation benchmarks. On a number of these tasks, PaLM 540B achieves breakthrough performance, outperforming the finetuned state-of-the-art on a suite of multi-step reasoning tasks, and outperforming average human performance on the recently released BIG-bench benchmark. A significant number of BIG-bench tasks showed discontinuous improvements from model scale, meaning that performance steeply increased as we scaled to our largest model. PaLM also has strong capabilities in multilingual tasks and source code generation, which we demonstrate on a wide array of benchmarks. We additionally provide a comprehensive analysis on bias and toxicity, and study the extent of training data memorization with respect to model scale. Finally, we discuss the ethical considerations related to large language models and discuss potential mitigation strategies