922017 research outputs found
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Counter-Example Guided Neural Network Compression Refinement (CEG4N)
No full textNeural networks are essential components of learning-basedsoftware systems. However, their high compute, memory, and power requirements make using them in low resources domains challenging. For this reason, neural networks are often compressed before deployment. Existing compression techniques tend to degrade the network accuracy.We propose Counter-Example Guided Neural Network Compression Refinement (CEG4N). This technique combines search-based quantization and equivalence verification: the former minimizes the computational requirements, while the latter guarantees that the network’s output does not change after compression. We evaluate CEG4N on a diverse set of benchmarks that include large and small networks. Our technique was successful at compressing the networks in our evaluation while producing models with up to 72% better accuracy than state-of-the-art techniques
The Effect of Compositional Heterogeneity on the Martensite Start Temperature of a High Strength Steel During Rapid Austenitisation and Cooling
No full textMany low alloy steels are compositionally heterogeneous due to the preferential segregation of alloying elements to the dendritic or interdendritic regions when the steel is first solidified (microsegregation). This segregation is often ignored when using CCT diagrams to predict the phase transformation behaviour of steels, but may be of importance in some industrially-relevant cases. This work focuses on the martensite start temperature (Ms) of Super CMV, a high strength aerospace steel, after rapid austenitisation treatment to various peak temperatures from 900 °C to 1300 °C. It was found that the average Ms temperature increased with increasing peak temperature (and prior austenite grain size) at peak temperatures of 1100°C and above, which is to be expected conventionally. However, at peak temperatures of below 1100°C, the Ms temperature increased with decreasing prior-austenite grain size. It is proposed that this was due to the presence of non-dissolved carbides in these conditions, particularly in enriched bands of material, which deplete the matrix and hence raise Ms
Evaluating the Use of Phosphate to Mitigate Caustic-PbSCC of Alloy 690TT
No full textPhosphate additions to Pb-caustic water chemistry were investigated as possible avenue to mitigate against caustic Lead-Assisted Stress Corrosion Cracking (PbSCC) of Alloy 690TT at around 310°C. Dosing with 1,700 ppm of phosphate promoted a small beneficial effect in PbSCC resistance. However, with 3,000 ppm of phosphate, mitigation was only achieved for as received surfaces, whilst polished surfaces displayed localized attack. Advanced materials characterization revealed that a similar crack tip composition was generated in different solutions. It is suggested that phosphate decreased the PbSCC kinetics by partly sequestering Pb from the bulk environment, although not below the threshold value required to prevent cracking
Adrenergic prolongation of action potential duration in rainbow trout myocardium via inhibition of the delayed rectifier potassium current, IKr.
No full textCatecholamines mediate the ‘fight or flight’ response in a wide variety of vertebrates.The endogenous catecholamine adrenaline increases heart rate and contractilestrength to raise cardiac output. The increase in contractile force is driven in large partby an increase in myocyte Ca 2+ influx on the L-type Ca current (I CaL ) during thecardiac action potential (AP). Here, we report a K + - based mechanism that prolongsAP duration (APD) in fish hearts following adrenergic stimulation. We show thatadrenergic stimulation inhibits the delayed rectifier K + current (I Kr ) in rainbow trout( Oncorhynchus mykiss ) cardiomyocytes. This slows repolarization and prolongsAPD which may contribute to positive inotropy following adrenergic stimulation in fishhearts. The endogenous ligand, adrenaline (10 -6 M), which activates both α- and βARs reduced maximal I Kr tail current to 61.4±3.9% of control in atrial and ventricularmyocytes resulting in an APD prolongation of ~ 20% at both 50 and 90%repolarization. This effect was reproduced by the α-specific adrenergic agonist,phenylephrine (10 -6 M), but not the β-specific adrenergic agonist isoproterenol (10 -6 M). Adrenaline (10 -6 M) in the presence of β 1 and β 2 -blockers (10 -6 Matenolol and 10 -6 M ICI-118551, respectively) also inhibited I Kr . Thus, I Krsuppression following adrenergic stimulation leads to APD prolongation in the rainbowtrout heart. This is the first time this mechanism has been identified in fish and may actin unison with the well-known enhancement of I CaL following adrenergic stimulationto prolong APD and increase cardiac inotropy
A Molecular Simulation Study into the Stability of Hydrated Graphene Nanochannels used in Nanofluidics Devices
No full textGraphene-based nanochannels are a popular choice in emerging nanofluidics applications because of their tunable and nanometer-scale channels. In this work, molecular dynamics (MD) simulations were employed both to i) assess the stability of dry and hydrated graphene nanochannels and ii) elucidate the properties of water confined in these channels, using replica-scale models with 0.66 – 2.38 nm channel heights. The use of flexible nanochannel walls allows the nanochannel height to relax in response to the solvation forces arising from the confined fluid and the forces between the confining surfaces, without the need for application of arbitrarily high external pressures. Dry nanochannels were found to completely collapse if the initial nanochannel height was less than 2 nm, due to attractive van der Waals interactions between the confining graphene surfaces. However, the presence of water was found to prevent total nanochannel collapse, due to repulsive hydration forces opposing the attractive van der Waals force. For nanochannel heights less than ~1.7 nm, the confining surfaces must be relaxed to obtain accurate hydration pressures and water diffusion coefficients, by ensuring commensurability between the number of confined water layers and the channel height. For very small (~0.7 nm), hydrated channels a pressure of 231 MPa due to the van der Waals forces was obtained. In the same system, the confined water forms a mobile, liquid monolayer with a diffusion coefficient of 4.0 × 10–5 cm2 s–1, much higher than bulk liquid water. Although this finding conflicts with most classical MD simulations, which predict in-plane order and arrested dynamics, it is supported by experiments and recently published first-principles MD simulations. Classical simulations can therefore be used to predict the properties of water confined in sub-nanometre graphene channels, providing sufficiently realistic molecular models and accurate intermolecular potentials are employed
Denotational and Algebraic Semantics for Cyber-physical Systems
No full textThe cyber-physical system (CPS) is a dynamic system that contains both continuous and discrete behaviors. It has a wide range of applications in fields such as healthcare equipment, intelligent traffic control and environmental monitoring. However, the combination of continuous physical behaviorand discrete control behavior may complicate the design of systems further. It is of great necessity to give an explicit formal language and its semantics for CPS. In this paper, we elaborate the modeling language for CPS based on our previous work.This language supports shared variables to model the interaction between the physical and the cyber. Additionally, we give it denotational semantics and algebraic semantics, especially focus on the continuous behavior and its composition with the discrete behavior. Throughout this paper, we also present some examples to illustrate the feasibility of the language and its semantics intuitively.Index Terms—Cyber-physical system (CPS), Unifying Theories of Programming (UTP), Denotational semantics, Algebraic semantic
New Reaction Pathways by Integrating Chemo- and Biocatalysis
No full textThe combination of chemo- and biocatalysis in one-pot (integrated catalysis) is a powerful approach to develop new routes towards important products under mild and environmentally benign reaction conditions. Integrated catalysis can improve overall synthetic efficiency and, due to the complementary nature of chemo- and biocatalysts, transformations can be performed, which would be otherwise challenging using a single catalyst. In this review, we highlight recent trends for the combination of enzymes with chemocatalysts. Transition-metal catalysis, organocatalysis, and photoredox catalysis have been combined with different biocatalysts and discussed accordingly. We highlight further how integrated catalysis does not only deliver benign substitutes for known transformations but moreover enables transformations which would be otherwise impossible
Initial Conditions for Star Formation: A Physical Description of the Filamentary ISM
No full textThe interstellar medium contains filamentary structure over a wide range of scales. Understanding the role of this structure, both as a conduit of gas across the scales and a diagnostic tool of local physics, is a major focus of star formation studies. We review recent progress in studying filamentary structure in the ISM, interpreting its properties in terms of physical processes, andexploring formation and evolution scenarios. We include structures from galactic-scale filaments to tenth-of-a-parsec scale filaments, comprising both molecular and atomic structures, from both observational and theoretical perspectives. In addition to the literature overview, we assemble a large amount of catalogue data from different surveys and provide the most comprehensive census of filamentary structures to date. Our census consists of 22 803 filamentary structures, facilitating a holistic perspective and new insights. We use our census to conduct a meta-analysis, leading to a description of filament properties over four orders of magnitudes in length and eight in mass. Our analysis emphasises the hierarchical and dynamical nature of filamentary structures. Filaments do not live in isolation, nor they generally resemble static structures close to equilibrium. We propose that accretion during filament formation and evolution sets some of the key scaling properties of filaments. This highlights the role of accretion during filament formation and evolution and also in setting the initial conditions for star formation. Overall, the study of filamentary structures during the past decade has been observationally driven. While great progress has been made on measuring the basic properties of filaments, our understanding of their formation and evolution is clearly lacking. In this context, we identify a number of directions and questions we consider most pressing for the field
Dry heterometallic resist processing based on thermal sublimation deposition and development
No full textA negative tone heterometallic ring resist (HRR) based on a supramolecular assembly [NH2(allyl)2][Cr7NiF8(piv)16] with previously demonstrated resolution down to sub-10nm lines is evaluated in terms of its flexibility to be processed either ‘wet’ (spin-cast, solvent-developed) or ‘dry’ (deposition and development by vacuum sublimation). The implemented sublimation hardware fits easily in the wafer load-lock chamber of EUV and electron beam exposure systems dedicated to R&D activities and allows for HRR films to be uniformly deposited or developed in the same vacuum environment. The HRR shows a sublimation rate dependence on temperature that obeys a Clausius-Clapeyron relation, with thermal stability up to 275°C. Flood exposures of the HRR show identical sensitivity between wet and dry deposited films, while contrast degradation is observed when dry development is initiated by increasing the temperature prior to system pump down. A modified sublimation setup allows for the dry development of exposed HRR samples inside the electron beam tool without breaking vacuum. In this case, nominally patterned 25nm L/S are identically resolved at 30 keV for wet- or dry-developed HRR
Antiplatelet resistance: a review of concepts, mechanisms and implications for management in acute ischaemic stroke and transient ischaemic attack
No full textAcute ischaemic stroke is a leading cause of death and major disability worldwide. Approximately 50% of ischaemic strokes are caused by atherothrombotic occlusion of the cerebral arteries and antiplatelets are the mainstay of secondary stroke preventative treatment. Aspirin is beneficial if given early and short-term treatment using aspirin and clopidogrel is increasingly used for patients with intracranial atherosclerotic disease, minor stroke and/or transient ischemic attack. However, up to 50% of patients continue to have recurrent stroke and major vascular events, which may be partly due to resistance to aspirin and/or clopidogrel. Although the precise mechanisms are unknown, clinical and genetic factors associated with bioavailability and binding to target receptors are implicated. This narrative review begins with the concept of aspirin and clopidogrel resistance in ischaemic stroke and transient ischaemic attack (TIA), potential mechanisms including genetic polymorphisms and an overview of platelet function measures and limitations. We conclude by highlighting practical issues in the management of patients with aspirin and/or clopidogrel resistance including the emerging interest in ticagrelor, prasugrel and cilostazol and directions for future trials in TIA and acute ischaemic stroke