A Transfer Function Analysis of a Geomagnetic Depth Sounding-Profile across Central British Columbia

1973 ◽  
Vol 10 (7) ◽  
pp. 1089-1098 ◽  
Author(s):  
H. Dragert
Keyword(s):  
British Columbia ◽  
Transfer Functions ◽  
Function Analysis ◽  
Three Dimensional ◽  
Vertical Component ◽  
Rocky Mountain ◽  
Three Dimensional Model ◽  
Transfer Function Analysis ◽  
Single Station ◽  
Depth Sounding

Time variations of the geomagnetic field observed across British Columbia at a mean latitude of 54 °N are analyzed using 'single-station' and 'paired-station' optimum transfer functions. The frequency and spatial dependence of both coastal and inland geomagnetic anomalies are estimated with the following results. (1) The normal coast effect is strongly perturbed by lateral conductivity inhomogeneities both north and south of the profile. (2) A simple, single NW–SE striking conductivity contrast between the Cordillera and plains cannot account for the total geomagnetic anomaly in the area of the Rocky Mountain Trench; a three-dimensional model is required, incorporating (i) a lateral inhomogeneity striking east–west and located to the south of the profile, (ii) the effect of induction by the vertical component of source or secondary fields.

Conductive structures in southwestern Canada: a regional magnetometer array study

1982 ◽  
Vol 19 (8) ◽  
pp. 1680-1690 ◽  
Author(s):  
D. I. Gough ◽  
D. K. Bingham ◽  
M. R. Ingham ◽  
A. O. Alabi
Keyword(s):  
British Columbia ◽  
Lower Crust ◽  
Transfer Functions ◽  
Vertical Component ◽  
Rocky Mountain ◽  
Event Analysis ◽  
Response Curves ◽  
Model Studies ◽  
Single Station ◽  
Induced Currents

An array of 33 three-component recording magnetometers was operated in June and July 1980 in Alberta and British Columbia south of the Edmonton – Prince Rupert highway. This very large array, with its stations dispersed through 550 000 km2 and on average 150 km apart, had limited resolution and was designed to confirm known conductive structures, discover new ones, and locate them sufficiently for suitable placement of further arrays with closer spaced stations and, therefore, higher resolution. Magnetograms and three sets of Fourier transform anomaly maps are presented. They show the general attenuation of the vertical component of variation fields west of the Rocky Mountain Belt known from previous work and generally attributed to a conductive layer in the lower crust or upper mantle. Two prominent local anomalies are shown by variation fields of periods 15–30 min. The first indicates induced currents near Tête Jaune Cache, west of Jasper. The highly conductive structure carrying the induced currents may include wet sediments in the Rocky Mountain Trench and possibly partial melt at depth associated with recent volcanics. The second local anomaly appears to be associated with a crustal conductive structure that strikes northeast–southwest across southern Alberta and crosses the southeast corner of British Columbia into eastern Washington State. This may be associated with a Precambrian rift in the lower crust discovered by Kanasewich and his colleagues using deep crustal seismic reflections some 15 years ago. Both of these anomalies are under further investigation by means of arrays operated in 1981 in locations indicated by the results of the array reported here. The regional westward attenuation of the vertical fields has been quantified by means of single-station transfer functions and artificial event analysis, as developed by Bailey and others, to show the Z response to unit southwest–northeast horizontal field at three periods, along a profile from Squamish, near Vancouver, to Edmonton. These response curves will be used in model studies of the regional conductive structure.

Conductive structures under the Canadian Rocky Mountains

1985 ◽  
Vol 22 (3) ◽  
pp. 384-398 ◽  
Author(s):  
D. K. Bingham ◽  
D. I. Gough ◽  
M. R. Ingham
Keyword(s):  
Rocky Mountains ◽  
Transfer Functions ◽  
Three Dimensional ◽  
Vertical Component ◽  
Rocky Mountain ◽  
Auroral Zone ◽  
Event Analysis ◽  
Canadian Rocky Mountains ◽  
Period Range ◽  
Single Station

The paper reports results from an array of 33 three-component magnetometers that recorded time-varying fields in 1981 over an area of some 56 000 km2 in the Canadian Cordillera. The array was centred at Tête Jaune Cache in the Rocky Mountain Trench, where a large magnetovariation anomaly had been located in an earlier array study. It was bisected by the trench and extended to the northeast across the Rocky Mountains to the Alberta Foothills and to the southwest across the Cariboo and Monashee mountains. Magnetograms and Fourier transform maps covering the period range 10–91 min show strong attenuation of the vertical component, Z, southwest of the Rocky Mountain Trench, with very large Z amplitudes in the Main Ranges of the Rockies. The horizontal components show an elongated anomaly along the Rocky Mountains Main Ranges and Trench, with three-dimensional features superimposed. The conductive structures include a highly conductive layer, probably in the lower crust, southwest of the trench and a conductive ridge rising into the upper crust near the edge of that layer. Current models have been fitted to observed vertical -and horizontal-component anomalies and show that both layer and ridge are necessary for a fit and that the ridge is 50–80 km wide. Single-station transfer functions at periods of 10 and 22 min have been calculated from a number of variation events of various polarizations, to reduce any displacement of the anomalies by auroral-zone source currents. Artificial-event analysis, with these transfer functions, shows that the conductive ridge lies under the Main Ranges of the Rockies and not under the trench. Its great width indicates a structure of major tectonic significance, which will be considered in another paper.

A superelastic protective technique for mitigating the effects of vertical and horizontal seismic excitations on highway bridges

2016 ◽  
Vol 28 (12) ◽  
pp. 1533-1552 ◽  
Author(s):  
Hadi Aryan ◽  
Mehdi Ghassemieh
Keyword(s):  
Three Dimensional ◽  
Vertical Component ◽  
Time History ◽  
Highway Bridges ◽  
Three Dimensional Model ◽  
Seismic Excitations ◽  
Innovative System ◽  
Bridge Responses ◽  
Nonlinear Time History ◽  
New System

Vertical component of seismic excitations tremendously affects the performance of bridges during the earthquakes. Several conducted studies identified the lack of engineering attention to the vertical seismic excitation as the main reason of various considerable bridge damages during the past earthquakes. Thus, in this article, an innovative system with superelastic properties is proposed for retrofitting and also new design of the bridges which can simultaneously mitigate the effects of vertical and horizontal seismic excitations. In order to investigate the efficiency of the new system, an evaluation is performed through many nonlinear time history analyses on a three-dimensional model of a detailed multi-span simply supported bridge using a suite of representative ground motions of the bridge region. The analyses are conducted separately on the pertinent issues that affect the performance of the new proposed system. As a part of the study, to identify the sensitivity of the new system and evaluate the overall seismic performance, several assessment parameters are utilized. The results show that the proposed system is efficient for reducing bridge responses as well as improving nonlinear performance of the columns during vertical and horizontal seismic excitations.

A Transfer-Function Formulation For Nonuniformly Distributed Parameter Systems

1994 ◽  
Vol 116 (4) ◽  
pp. 426-432 ◽  
Author(s):  
B. Yang ◽  
H. Fang
Keyword(s):  
Transfer Function ◽  
State Space ◽  
Fundamental Matrix ◽  
Transfer Functions ◽  
Function Analysis ◽  
System Response ◽  
Approximate Methods ◽  
Arbitrary Boundary ◽  
Transfer Function Analysis ◽  
Function Formulation

This paper studies a transfer-function formulation for general one-dimensional, nonuniformly distributed systems, subject to arbitrary boundary conditions and external disturbances. In the development, the governing equations of the nonuniform system are cast into a state-space form in the Laplace transform domain. The system response and distributed transfer functions are derived in term of the fundamental matrix of the state-space equation. Two approximate methods, the step-function approximation and truncated Taylor series, are proposed to evaluate the fundamental matrix. With the transfer-function formulation, various dynamics and control problems for the nonuniformly distributed system can be conveniently addressed. The transfer-function analysis also is applied to constrained/combined nonuniformly distibuted systems. The method developed is illustrated on two nonuniform beams.

The arthropod Sidneyia inexpectans , Middle Cambrian, Burgess Shale, British Columbia

1981 ◽  
Vol 295 (1079) ◽  
pp. 619-653 ◽  
Keyword(s):  
British Columbia ◽  
Posterior Margin ◽  
Three Dimensional ◽  
The Body ◽  
Gut Contents ◽  
Burgess Shale ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Middle Cambrian ◽  
Abdominal Somite

Old and new specimens of Sidneyia inexpectans have been studied and are accompanied by explanatory drawings and photographs. New reconstructions of the animal are given together with a three-dimensional model. The body consisted of a cephalon with a long backwardly directed doublure, a thorax of nine articulating somites, abdomen with cylindrical exoskeleton of two or three somites and a telson. A caudal fan was formed by a pair of uropods articulating at the posterior margin of the last abdominal somite. The cephalon had stalked eyes and preoral antennae but no walking or grasping appendages. The first four somites of the thorax had paired uniramous, prehensile walking legs attached to the body by broad coxae with spiny gnathobases. The coxae were smaller on the five posterior thoracic somites and the paired appendages were biramous, each bearing a gill supported on a flap attached at its proximal end to the first podomere of the leg. The coxa-body attachment resembles that of modern merostomes and is in advance of trilobites. Evidence suggests that Sidneyia was a bottom-living, carnivorous animal eating larger and harder food than trilobites. Gut contents include ostracodes, hyolithids, small trilobites and phosphatic debris. Sidneyia is the earliest known form which could be an ancestor to merostomes, but its body plan and absence of chelicera distinguishes Sidneyia from this group. The holotype of Amiella ornata Walcott, 1911 is reinterpreted and its synonomy with S. inexpectans is confirmed.

Transfer function analysis of autonomic regulation. I. Canine atrial rate response

1989 ◽  
Vol 256 (1) ◽  
pp. H142-H152 ◽  
Author(s):  
R. D. Berger ◽  
J. P. Saul ◽  
R. J. Cohen
Keyword(s):  
Transfer Function ◽  
Transfer Functions ◽  
Function Analysis ◽  
Cardiac Pacemaker ◽  
Corner Frequency ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Atrial Rate ◽  
Transfer Function Analysis ◽  
Functional Components

We present a useful technique for analyzing the various functional components that comprise the cardiovascular control network. Our approach entails the imposition of a signal with broad frequency content as an input excitation and the computation of a system transfer function using spectral estimation techniques. In this paper, we outline the analytical methods involved and demonstrate the utility of our approach in studying the dynamic behavior of the canine cardiac pacemaker. In particular, we applied frequency-modulated pulse trains to either the right vagus or the cardiac sympathetic nerve and computed transfer functions between nerve stimulation rate and the resulting atrial rate. We found that the sinoatrial node (and associated automatic tissue) responds as a low-pass filter to fluctuations in either sympathetic or parasympathetic tone. For sympathetic fluctuations, however, the filter has a much lower corner frequency than for vagal fluctuations and is coupled with a roughly 1.7-s pure delay. We further found that the filter characteristics, including the location of the corner frequency and rate of roll-off, depend significantly on the mean level of sympathetic or vagal tone imposed.

Transfer function analysis of the circulation: unique insights into cardiovascular regulation

1991 ◽  
Vol 261 (4) ◽  
pp. H1231-H1245 ◽  
Author(s):  
J. P. Saul ◽  
R. D. Berger ◽  
P. Albrecht ◽  
S. P. Stein ◽  
M. H. Chen ◽  
...  
Keyword(s):  
Transfer Function ◽  
Arterial Pressure ◽  
Transfer Functions ◽  
Function Analysis ◽  
Pressure Fluctuations ◽  
Rate Of Change ◽  
Phase Delay ◽  
Sinus Arrhythmia ◽  
Mechanical Effects ◽  
Transfer Function Analysis

We have demonstrated previously that transfer function analysis can be used to precisely characterize the respiratory sinus arrhythmia (RSA) in normal humans. To further investigate the role of the autonomic nervous system in RSA and to understand the complex links between respiratory activity and arterial pressure, we determined the transfer functions between respiration, heart rate (HR), and phasic, systolic, diastolic, and pulse arterial pressures in 14 healthy subjects during 6-min periods in which the respiratory rate was controlled in a predetermined but erratic fashion. Pharmacological autonomic blockade with atropine, propranolol, and both, in combination with changes in posture, was used to characterize the sympathetic and vagal contributions to these relationships, as well as to dissect the direct mechanical links between respiration and arterial pressure from the effects of the RSA on arterial pressure. We found that 1) the pure sympathetic (standing + atropine) HR response is characterized by markedly reduced magnitude at frequencies greater than 0.1 Hz and a phase delay, whereas pure vagal (supine + propranolol) modulation of HR is characterized by higher magnitude at all frequencies and no phase delay; 2) both the mechanical links between respiration and arterial pressure and the RSA contribute significantly to the effects of respiration on arterial pressure; 3) the RSA contribution to arterial pressure fluctuations is significant for vagal but not for sympathetic modulation of HR; 4) the mechanical effects of respiration on arterial pressure are related to the negative rate of change of instantaneous lung volume; 5) the mechanical effects have a higher magnitude during systole than during diastole; and 6) the mechanical effects are larger in teh standing than the supine position. Most of these findings can be explained by a simple model of circulatory control based on previously published experimental transfer functions from our laboratory.

Electromechanical Simulation of Helicopter Blade Responses to Random Excitation During Forward Flight

1974 ◽  
Vol 96 (2) ◽  
pp. 405-410
Author(s):  
D. D. Kana ◽  
Wen-Hwa Chu
Keyword(s):  
Transfer Functions ◽  
Function Analysis ◽  
Power Spectra ◽  
Random Excitation ◽  
Analog Computer ◽  
Excitation Power ◽  
Aerodynamic Load ◽  
Forward Flight ◽  
Transfer Function Analysis ◽  
Advance Ratio

The response of a model helicopter rotor blade to random excitation while in simulated forward flight is studied analytically and experimentally by means of an electromechanical apparatus. Generalized transfer functions are defined which relate steady-state responses in bending, flapping, and torsion modes to a sine input. Responses occur at the input and side-band frequencies. These transfer functions are then used along with excitation power spectra to predict the nonstationary time-averaged power spectrum of the response. Validity of the transfer function analysis is investigated by means of the electromechanical model which includes analog computer simulation of the interaction of blade deflections and aerodynamic load. Generalized transfer functions are measured for sinusoidal excitation. They are then used with measured excitation power spectra to predict the response, and the result is compared with measured response power spectra. Agreement is generally good for low advance ratio, but discrepancies diverge with increasing advance ratio.

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