Modelling Earthquake Ground Motions by Stochastic Method

The prediction of earthquake ground motions in accordance with recorded observations from past events is the core business of engineering seismology. An attenuation model presents values of parameters characterising the intensities and properties of ground motions estimated of projected earthquake scenarios (which are expressed in terms of magnitude and distance). Empirical attenuation models are developed from regression analysis of recorded strong motion accelerograms. In situations where strong motion data are scarce the database of records has to cover a very large area which may be an entire continent (eg. Ambrasey model for Europe) or a large part of a continent (eg. Toro model for Central & Eastern North America) in order that the size of the database has statistical significance (Toro et al., 1997; Ambrasey, 1995). Thus, attenuation modelling based on regression analysis of instrumental data is problematic when applied to regions of low and moderate seismicity. This is because of insufficient representative data that has been collected and made available for model development purposes. An alternative approach to attenuation modelling is use of theoretical models. Unlike an empirical model, a theoretical model only makes use of recorded data to help ascertain values of parameters in the model rather than to determine trends from scratch by regression of data. Thus, much less ground motion data is required for the modelling. Data that is available could be used to verify the accuracies of estimates made by the theoretical model. Ground motion simulations by classical wave theory provides comprehensive description of the earthquake ground motions but information that is available would typically not be sufficient as input to the simulations. The heuristic source model of Brune (1970) which defines the frequency content of seismic waves radiated from a point source is much simpler. The model has only three parameters : seismic moment, distance and the stress parameter. Combining this point source model with a number of filter functions which represent modification effects of the wave travel path and the site provides estimates for the Fourier amplitude spectrum of the motion generated by the earthquake on the ground surface. The source model (of Brune) in combination with the various filter functions are collectively known as the seismological model (Boore, 1983). Subsequent research by Atkinson and others provides support for the proposition that simulations from a well calibrated point source model are reasonably consistent with those from the more realistic finite fault models

Gauge Invariance, the Quantum Action Principle, and the Renormalization Group

If the Wilsonian renormalization group (RG) is formulated with a cutoff that breaks gauge invariance, then gauge invariance may be recovered only once the cutoff is removed and only once a set of effective Ward identities is imposed. We show that an effective Quantum Action Principle can be formulated in perturbation theory which enables the effective Ward identities to be solved order by order, even if the theory requires non-vanishing subtraction points. The difficulties encountered with non-perturbative approximations are briefly discussed.Comment: 11 pages, latex, no figures, one reference added, version to be published on Phys. Lett.

Review of modern concepts in the engineering interpretation of earthquake response spectra

The design response spectrum is typically the starting point of most codified seismic design and assessment procedures and is used predominantly to prescribe the applied inertia forces induced by earthquake ground motions. This paper introduces and reviews modern concepts related to the effective development and application of earthquake design response spectra, including the conventional acceleration response spectrum, the velocity spectrum, and the displacement spectrum. It further briefly reviews the concepts of the inelastic response spectrum and the capacity spectrum. A number of the ideas presented are targeted particularly at assisting practising engineers working in low- and moderate-seismicity environments. The principal purpose is to enlighten engineers to modern concepts in response spectra development, in order to subsequently facilitate the effective use of the information contained in an earthquake response spectrum for both analysis and design applications.published_or_final_versio

Studies of proton irradiated 0.9PMN-0.1PT/P(VDF-TrFE) 0-3 composites

2001-2002 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

The metaphysics of Machian frame-dragging

The paper investigates the kind of dependence relation that best portrays Machian frame-dragging in general relativity. The question is tricky because frame-dragging relates local inertial frames to distant distributions of matter in a time-independent way, thus establishing some sort of non-local link between the two. For this reason, a plain causal interpretation of frame-dragging faces huge challenges. The paper will shed light on the issue by using a generalized structural equation model analysis in terms of manipulationist counterfactuals recently applied in the context of metaphysical enquiry by Schaffer (2016) and Wilson (2017). The verdict of the analysis will be that frame-dragging is best understood in terms of a novel type of dependence relation that is half-way between causation and grounding

Impairment in movement skills of children with autism spectrum disorders

We undertook this study to explore the degree of impairment in movement skills in children with autistic spectrum disorders (ASD) and a wide IQ range. Movement skills were measured using the Movement Assessment Battery for Children (M-ABC) in a large, well defined, population-derived group of children (n=101: 89 males,12 females; mean age 11y 4mo, SD 10mo; range 10y-14y 3mo) with childhood autism and broader ASD and a wide range of IQ scores. Additionally, we tested whether a parent-completed questionnaire, the Developmental Coordination Disorder Questionnaire (DCDQ), was useful in identifying children who met criteria for movement impairments after assessment (n=97 with complete M-ABCs and DCDQs). Of the children with ASD, 79% had definite movement impairments on the M-ABC; a further 10% had borderline problems. Children with childhood autism were more impaired than children with broader ASD, and children with an IQ less than 70 were more impaired than those with IQ more than 70. This is consistent with the view that movement impairments may arise from a more severe neurological impairment that also contributes to intellectual disability and more severe autism. Movement impairment was not associated with everyday adaptive behaviour once the effect of IQ was controlled for. The DCDQ performed moderately well as a screen for possible motor difficulties. Movement impairments are common in children with ASD. Systematic assessment of movement abilities should be considered a routine investigation

In-Plane Behavior of Cold-Formed Steel-Framed Shear Wall Panels Sheathed with Fibre Cement Board

Shear wall panels are commonly used as lateral load resisting elements to provide stability of the cold-formed steel-framed houses in Australia against wind and earthquake actions. The effectiveness of their lateral resistance behavior is obtained usually by experimental testing although it can also be done by analytical modeling. This paper presents racking test results of steelframed wall panels with different aspect ratios sheathed with fibre cement board subjected to monotonic and cyclic loading protocol. Performance parameters of the wall panels are obtained from the experimentally observed load-deflection curves using various existing methods and evaluation method is proposed. The evaluation method considers various performance characteristics including ductility modification factor, residual displacement recovery and load levels satisfying ultimate and serviceability limit state conditions

Biomechanical Characteristics of Lumbar Manipulation Performed by Expert, Resident, and Student Physical Therapists

Background Lumbar manipulation is a commonly used treatment for low back pain, but little research evidence exists regarding practitioner biomechanics during manipulation. Most existing evidence describes rate of force production through the hands into instrumented manikins and it is unclear how the practitioner moves their body and legs to generate this force. Objectives To identify and characterize important kinetic and kinematic factors in practitioners of varying experience performing lumbar manipulation in order to identify which factors distinguish experts from less experienced practitioners. Study design This was a cohort observational laboratory study. Methods 43 male physical therapists (PT) and PT students (4 experts, 11 residents, 13 third year, and 15 first year students) performed 4 manipulations each on asymptomatic patient models. Angular and linear kinematics of the pelvis were measured using motion capture, and ground reaction forces were measured with force plates under the practitioner\u27s feet. Results Peak pelvic angular velocity was greater and in the opposite direction in experts compared to other groups in the frontal plane (p = 0.020) and transverse plane (p = 0.000). Experts had greater downward pelvic linear velocity than third year students and first year students (p = 0.000). Experts also demonstrated faster rate of vertical ground reaction force unloading during the manipulation (p = 0.002). Conclusions Expert performance of manipulation was characterized by increased speed of linear and angular pelvic motion, and increased modulation of vertical ground reaction force. These results help to inform educators and practitioners that teach and use this complex manual skill

Human hypocretin and melanin-concentrating hormone levels are linked to emotion and social interaction.

The neurochemical changes underlying human emotions and social behaviour are largely unknown. Here we report on the changes in the levels of two hypothalamic neuropeptides, hypocretin-1 and melanin-concentrating hormone, measured in the human amygdala. We show that hypocretin-1 levels are maximal during positive emotion, social interaction and anger, behaviours that induce cataplexy in human narcoleptics. In contrast, melanin-concentrating hormone levels are minimal during social interaction, but are increased after eating. Both peptides are at minimal levels during periods of postoperative pain despite high levels of arousal. Melanin-concentrating hormone levels increase at sleep onset, consistent with a role in sleep induction, whereas hypocretin-1 levels increase at wake onset, consistent with a role in wake induction. Levels of these two peptides in humans are not simply linked to arousal, but rather to specific emotions and state transitions. Other arousal systems may be similarly emotionally specialized