17,395 research outputs found
Diesel engine fuel injection monitoring using acoustic measurements and independent component analysis
Air-borne acoustic based condition monitoring is a promising technique because of its intrusive nature and the rich information contained within the acoustic signals including all sources. However, the back ground noise contamination, interferences and the number of Internal Combustion Engine ICE vibro-acoustic sources preclude the extraction of condition information using this technique. Therefore, lower energy events; such as fuel injection, are buried within higher energy events and/or corrupted by background noise.
This work firstly investigates diesel engine air-borne acoustic signals characteristics and the benefits of joint time-frequency domain analysis. Secondly, the air-borne acoustic signals in the vicinity of injector head were recorded using three microphones around the fuel injector (120° apart from each other) and an Independent Component Analysis (ICA) based scheme was developed to decompose these acoustic signals. The fuel injection process characteristics were thus revealed in the time-frequency domain using Wigner-Ville distribution (WVD) technique. Consequently the energy levels around the injection process period between 11 and 5 degrees before the top dead center and of frequency band 9 to 15 kHz are calculated. The developed technique was validated by simulated signals and empirical measurements at different injection pressure levels from 250 to 210 bars in steps of 10 bars. The recovered energy levels in the tested conditions were found to be affected by the injector pressure settings
Frustration in Biomolecules
Biomolecules are the prime information processing elements of living matter.
Most of these inanimate systems are polymers that compute their structures and
dynamics using as input seemingly random character strings of their sequence,
following which they coalesce and perform integrated cellular functions. In
large computational systems with a finite interaction-codes, the appearance of
conflicting goals is inevitable. Simple conflicting forces can lead to quite
complex structures and behaviors, leading to the concept of "frustration" in
condensed matter. We present here some basic ideas about frustration in
biomolecules and how the frustration concept leads to a better appreciation of
many aspects of the architecture of biomolecules, and how structure connects to
function. These ideas are simultaneously both seductively simple and perilously
subtle to grasp completely. The energy landscape theory of protein folding
provides a framework for quantifying frustration in large systems and has been
implemented at many levels of description. We first review the notion of
frustration from the areas of abstract logic and its uses in simple condensed
matter systems. We discuss then how the frustration concept applies
specifically to heteropolymers, testing folding landscape theory in computer
simulations of protein models and in experimentally accessible systems.
Studying the aspects of frustration averaged over many proteins provides ways
to infer energy functions useful for reliable structure prediction. We discuss
how frustration affects folding, how a large part of the biological functions
of proteins are related to subtle local frustration effects and how frustration
influences the appearance of metastable states, the nature of binding
processes, catalysis and allosteric transitions. We hope to illustrate how
Frustration is a fundamental concept in relating function to structural
biology.Comment: 97 pages, 30 figure
Dynamics of Viscoplastic Deformation in Amorphous Solids
We propose a dynamical theory of low-temperature shear deformation in
amorphous solids. Our analysis is based on molecular-dynamics simulations of a
two-dimensional, two-component noncrystalline system. These numerical
simulations reveal behavior typical of metallic glasses and other viscoplastic
materials, specifically, reversible elastic deformation at small applied
stresses, irreversible plastic deformation at larger stresses, a stress
threshold above which unbounded plastic flow occurs, and a strong dependence of
the state of the system on the history of past deformations. Microscopic
observations suggest that a dynamically complete description of the macroscopic
state of this deforming body requires specifying, in addition to stress and
strain, certain average features of a population of two-state shear
transformation zones. Our introduction of these new state variables into the
constitutive equations for this system is an extension of earlier models of
creep in metallic glasses. In the treatment presented here, we specialize to
temperatures far below the glass transition, and postulate that irreversible
motions are governed by local entropic fluctuations in the volumes of the
transformation zones. In most respects, our theory is in good quantitative
agreement with the rich variety of phenomena seen in the simulations.Comment: 16 pages, 9 figure
Improving reliability and reducing risk by using inequalities
The paper introduces a powerful domain-independent method for improving reliability and reducing risk based on algebraic inequalities, which transcends mechanical engineering and can be applied in many unrelated domains. The paper demonstrates the application of inequalities to reduce the risk of failure by producing tight uncertainty bounds for properties and risk-critical parameters. Numerous applications of the upper-bound-variance inequality have been demonstrated in bounding uncertainty from multiple sources, among which is the estimation of uncertainty in setting positioning distance and increasing the robustness of electronic devices. The rearrangement inequality has been used to maximise the reliability of components purchased from suppliers. With the help of the rearrangement inequality, a highly counter-intuitive result has been obtained. If no information about the component reliability characterising the individual suppliers is available, purchasing components from a single supplier or from the smallest possible number of suppliers maximises the probability of a high-reliability assembly. The Cauchy-Schwartz inequality has been applied for determining sharp bounds of mechanical properties and the Chebyshev's inequality for determining a lower bound for the reliability of an assembly. The inequality of the inversely correlated random events has been introduced and applied for ranking risky prospects involving units with unknown probabilities of survival
Measuring inequality of well-being with a correlation-sensitive multidimensional Gini index
We propose to measure inequality of well-being with a multidimensional generalization of the Gini coefficient. We derive two inequality indices from their underlying social evaluation functions. These functions are conceived as a double aggregation functions: one across the dimensions of well-being, and another across the individuals. They differ only with respect to the sequencing of aggregations. We argue that the sequencing that does not exclude the Gini index to be sensitive to the correlation between the dimensions is more attractive. We illustrate both Gini indices using Russian household data on three dimensions of well-being: expenditure, health and education.multidimensional inequality, single parameter Gini index, correlation increasing majorization, Russia.
Dynamic covalent chemistry in polymer networks : a mechanistic perspective
The incorporation of dynamic covalent linkages within and between polymer chains brings new properties to classical thermosetting polymer formulations, in particular in terms of thermal responses, processing options and intrinsic recycling abilities. Thus, in recent years, there has been a rapidly growing interest in the design and synthesis of monomers and cross-linkers that can be used as robust but at the same time reactive organic building blocks for dynamic polymer networks. In this perspective, a selection of such chemistries is highlighted, with a particular focus on the reaction mechanisms of molecular network rearrangements, and on how various mechanistic profiles can be related to the mechanical and physicochemical properties of polymer materials, in particular in relation with vitrimers, the recently defined third category of polymer materials. The recent advances in this area are not only expected to help direct promising emerging polymer applications, but also point towards the need for a better fundamental understanding of chemical reactivity within a macromolecular context
Data analysis challenges in transient gravitational-wave astronomy
Gravitational waves are radiative solutions of space-time dynamics predicted
by Einstein's theory of General Relativity. A world-wide array of large-scale
and highly sensitive interferometric detectors constantly scrutinizes the
geometry of the local space-time with the hope to detect deviations that would
signal an impinging gravitational wave from a remote astrophysical source.
Finding the rare and weak signature of gravitational waves buried in
non-stationary and non-Gaussian instrument noise is a particularly challenging
problem. We will give an overview of the data-analysis techniques and
associated observational results obtained so far by Virgo (in Europe) and LIGO
(in the US), along with the prospects offered by the up-coming advanced
versions of those detectors.Comment: 7 pages, 5 figures, Proceedings of the ARENA'12 Conference, few minor
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