3,787 research outputs found
Strain-induced kinetics of intergrain defects as the mechanism of slow dynamics in the nonlinear resonant response of humid sandstone bars
A closed-form description is proposed to explain nonlinear and slow dynamics
effects exhibited by sandstone bars in longitudinal resonance experiments.
Along with the fast subsystem of longitudinal nonlinear displacements we
examine the strain-dependent slow subsystem of broken intergrain and
interlamina cohesive bonds. We show that even the simplest but
phenomenologically correct modelling of their mutual feedback elucidates the
main experimental findings typical for forced longitudinal oscillations of
sandstone bars, namely, (i) hysteretic behavior of a resonance curve on both
its up- and down-slopes, (ii) linear softening of resonant frequency with
increase of driving level, and (iii) gradual recovery (increase) of resonant
frequency at low dynamical strains after the sample was conditioned by high
strains. In order to reproduce the highly nonlinear elastic features of
sandstone grained structure a realistic non-perturbative form of strain
potential energy was adopted. In our theory slow dynamics associated with the
experimentally observed memory of peak strain history is attributed to
strain-induced kinetic changes in concentration of ruptured inter-grain and
inter-lamina cohesive bonds causing a net hysteretic effect on the elastic
Young's modulus. Finally, we explain how enhancement of hysteretic phenomena
originates from an increase in equilibrium concentration of ruptured cohesive
bonds that are due to water saturation.Comment: 5 pages, 3 figure
Quantitative estimation of plant characteristics using spectral measurement: A survey of the literature
There are no author-identified significant results in this report
Two RNA-binding motifs in eIF3 direct HCV IRES-dependent translation.
The initiation of protein synthesis plays an essential regulatory role in human biology. At the center of the initiation pathway, the 13-subunit eukaryotic translation initiation factor 3 (eIF3) controls access of other initiation factors and mRNA to the ribosome by unknown mechanisms. Using electron microscopy (EM), bioinformatics and biochemical experiments, we identify two highly conserved RNA-binding motifs in eIF3 that direct translation initiation from the hepatitis C virus internal ribosome entry site (HCV IRES) RNA. Mutations in the RNA-binding motif of subunit eIF3a weaken eIF3 binding to the HCV IRES and the 40S ribosomal subunit, thereby suppressing eIF2-dependent recognition of the start codon. Mutations in the eIF3c RNA-binding motif also reduce 40S ribosomal subunit binding to eIF3, and inhibit eIF5B-dependent steps downstream of start codon recognition. These results provide the first connection between the structure of the central translation initiation factor eIF3 and recognition of the HCV genomic RNA start codon, molecular interactions that likely extend to the human transcriptome
Modeling and simulation of phase-transitions in multicomponent aluminum alloy casting
The casting process of aluminum products involves the spatial distribution of alloying elements. It is essential that these elements are uniformly distributed in order to guarantee reliable and consistent products. This requires a good understanding of the main physical mechanisms that affect the solidification, in particular the thermodynamic description and its coupling to the transport processes of heat and mass that take place. The continuum modeling is reviewed and methods for handling the thermodynamics component of multi-element alloys are proposed. Savings in data-storage and computing costs on the order of 100 or more appear possible, when a combination of data-reduction and data-representation methods is used. To test the new approach a simplified model was proposed and shown to qualitatively capture the evolving solidification front
Patient Choice for Older People in English NHS Primary Care: Theory and Practice
In the English National Health Service (NHS), patients are now expected to choose the time and place of treatment and even choose the actual treatment. However, the theory on which patient choice is based and the implementation of patient choice are controversial. There is evidence to indicate that attitudes and abilities to make choices are relatively sophisticated and not as straightforward as policy developments suggest. In addition, and surprisingly, there is little research on whethermaking individual choices about care is regarded as a priority by the largest NHS patient group and the single largest group for most GPsâolder people.This conceptual paper examines the theory of patient choice concerning accessing and engaging with healthcare provision and reviews existing evidence on older people and patient choice in primary care
Preliminary evaluation of spectral, normal and meteorological crop stage estimation approaches
Several of the projects in the AgRISTARS program require crop phenology information, including classification, acreage and yield estimation, and detection of episodal events. This study evaluates several crop calendar estimation techniques for their potential use in the program. The techniques, although generic in approach, were developed and tested on spring wheat data collected in 1978. There are three basic approaches to crop stage estimation: historical averages for an area (normal crop calendars), agrometeorological modeling of known crop-weather relationships agrometeorological (agromet) crop calendars, and interpretation of spectral signatures (spectral crop calendars). In all, 10 combinations of planting and biostage estimation models were evaluated. Dates of stage occurrence are estimated with biases between -4 and +4 days while root mean square errors range from 10 to 15 days. Results are inconclusive as to the superiority of any of the models and further evaluation of the models with the 1979 data set is recommended
Definition and Demonstration of a Methodology for Validating Aircraft Trajectory Predictors
This paper presents a new methodology for validating an aircraft trajectory predictor, inspired by the lessons learned from a number of field trials, flight tests and simulation experiments for the development of trajectory-predictor-based automation. The methodology introduces new techniques and a new multi-staged approach to reduce the effort in identifying and resolving validation failures, avoiding the potentially large costs associated with failures during a single-stage, pass/fail approach. As a case study, the validation effort performed by the Federal Aviation Administration for its En Route Automation Modernization (ERAM) system is analyzed to illustrate the real-world applicability of this methodology. During this validation effort, ERAM initially failed to achieve six of its eight requirements associated with trajectory prediction and conflict probe. The ERAM validation issues have since been addressed, but to illustrate how the methodology could have benefited the FAA effort, additional techniques are presented that could have been used to resolve some of these issues. Using data from the ERAM validation effort, it is demonstrated that these new techniques could have identified trajectory prediction error sources that contributed to several of the unmet ERAM requirements
Proving Craig and Lyndon Interpolation Using Labelled Sequent Calculi
We have recently presented a general method of proving the fundamental
logical properties of Craig and Lyndon Interpolation (IPs) by induction on
derivations in a wide class of internal sequent calculi, including sequents,
hypersequents, and nested sequents. Here we adapt the method to a more general
external formalism of labelled sequents and provide sufficient criteria on the
Kripke-frame characterization of a logic that guarantee the IPs. In particular,
we show that classes of frames definable by quantifier-free Horn formulas
correspond to logics with the IPs. These criteria capture the modal cube and
the infinite family of transitive Geach logics
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