scholarly journals The wave form of atmospherics at night

1940 ◽  
Vol 176 (965) ◽  
pp. 180-202 ◽  
Keyword(s):  
Wave Form ◽  
Time Interval ◽  
Time Separation ◽  
The Earth ◽  
Lightning Channel ◽  
Reflexion Coefficient ◽  
Primary Pulse

The wave form of all atmospherics received at night from sources within 2000 km. can be accurately described as a ground pulse followed by a series of sky pulses produced by successive reflexions between the ionosphere and the earth, thirty such reflexions being frequently recorded. The time separation between the peaks of these pulses is determined by the distance travelled and the height of the layer. The primary pulse emitted by the source is usually a single complete oscillation of period ranging from 50 to 400//sec. A t distances greater than 500 km. the ground pulse and the first sky pulse merge owing to the shortness of the time interval between them . Differences of amplitude, form and phase between pulses can arise from differences in angle of emission from the parent lightning channel. The height of the reflecting layer can be determined within ± 1 km. It ranged from 85-5 to 90-5 km. during two winter months, with a mean of 88-0 km. The distances of the sources as found by analysis of the pulse series were corroborated by independent location with cathode-ray direction-finders. The reflexion coefficient of the layer for the pulses of longer period exceeded 0-80. The velocity of the ground pulse where it can be tested is within 0.7 % of that of light.

The Earth Sciences and Creative Practice

2015 ◽  
pp. 110-140
Author(s):  
Suzette Worden
Keyword(s):  
Earth Sciences ◽  
Digital Media ◽  
Time Interval ◽  
Audience Participation ◽  
Transdisciplinary Approach ◽  
Deep Time ◽  
Environmental Care ◽  
The Earth ◽  
Geological Age ◽  
Curatorial Practice

The Anthropocene is being suggested as a new geological age replacing the Holocene and is a description of a time interval where significant conditions and processes are profoundly altered by human activity. Artists interested in the earth sciences are using digital media to provide audiences with ways of understanding the issues highlighted in discussions about the Anthropocene. These artists are harnessing data through visualisation and sonification, facilitating audience participation, and are often working in art-science collaborations. These activities demonstrate a transdisciplinary approach that is necessary for confronting the world's most pressing problems, such as climate change. After a discussion of the opportunities provided by visualisation technologies and an overview of the Anthropocene, this chapter explores the following interrelated themes through examples of creative works: (1) nanoscale, (2) geology and deep time, (3) climate, weather, and the atmosphere, (4) extreme places – beyond wilderness, and (5) curatorial practice as environmental care.

scholarly journals Nonlinear gas oscillations in pipes. Part 1. Theory

1973 ◽  
Vol 59 (1) ◽  
pp. 23-46 ◽  
Author(s):  
J. Jimenez
Keyword(s):  
Boundary Conditions ◽  
Equations Of Motion ◽  
Nonlinear Effects ◽  
Wave Form ◽  
Cube Root ◽  
Acoustic Oscillations ◽  
Open Mouth ◽  
Near Resonance ◽  
Reflexion Coefficient ◽  
Two Parameters

The problem of forced acoustic oscillations in a pipe is studied theoretically. The oscillations are produced by a moving piston in one end of the pipe, while a variety of boundary conditions ranging from a completely closed to a completely open mouth at the other end are considered. All these boundary conditions are modelled by two parameters: a length correction and a reflexion coefficient equivalent to the acoustic impedance.The linear theory predicts large amplitudes near resonance and nonlinear effects become crucially important. By expanding the equations of motion in a series in the Mach number, both the amplitude and wave form of the oscillation are predicted there.In both the open- and closed-end cases the need for shock waves in some range of parameters is found. The amplitude of the oscillation is different for the two cases, however, being proportional to the square root of the piston amplitude in the closed-end case and to the cube root for the open end.

Initiation of each avian inspiration by a CO2 threshold mechanism

1979 ◽  
Vol 47 (1) ◽  
pp. 233-239 ◽  
Author(s):  
D. A. Miller ◽  
A. L. Kunz
Keyword(s):  
Threshold Model ◽  
Co2 Concentration ◽  
Threshold Level ◽  
Mean Value ◽  
Wave Form ◽  
Time Interval ◽  
Threshold Mechanism ◽  
The Mean ◽  
The Relationship ◽  
Respiratory Movements

The avian respiratory oscillator has been investigated in a unidirectionally ventilated chicken by changing the dynamic pattern of inflow CO2 concentration (FCO2). Stimulation with periodic FCO2 results in a one-to-one synchronization of the respiratory movements that we have called pacing (Respir. Physiol. 22: 167--177, 1974). A two-parameter CO2 threshold model is proposed to explain this behavior. The model states that when FCO2 reaches a threshold level (L), it initiates the beginning of inspiration a constant time interval (LB) later. According to this model, when a triangular FCO2 concentration is used to synchronize the breathing pattern, the time from the minimum of the wave form to the beginning of inspiration (C-B interval) is dependent on the mean value and the rate of rise of FCO2 as determined by period and amplitude of the triangle. Particularly interesting is the prediction that the direction of the relationship (increasing or decreasing) between FCO2 amplitude and the C-B interval is dependent on whether the mean value of FCO2 is above or below the threshold level. Experimental data obtained during amplitude changes support the above prediction.

On the near-equilibrium and near-frozen regions in an expansion wave in a relaxing gas

1964 ◽  
Vol 19 (1) ◽  
pp. 81-102 ◽  
Author(s):  
J. G. Jones
Keyword(s):  
Asymptotic Solution ◽  
Simple Wave ◽  
Expansion Wave ◽  
Wave Form ◽  
Time Interval ◽  
Finite Time Interval ◽  
Acoustic Equation ◽  
Equilibrium Region ◽  
Relaxing Gas ◽  
Asymptotic Equilibrium

A weak expansion wave propagating in a relaxing gas is discussed with particular reference to the ‘near-equilibrium’ and ‘near-frozen’ regions. The concept of bulk viscosity is used in conjunction with Burger's equation in the near-equilibrium region. The asymptotic equilibrium simple wave is modified by diffusive regions in the neighbourhood of the first and last rays. It is shown that in the case of a weak expansion wave, Chu's asymptotic solution of the acoustic equation describes the wave-form for a finite time interval before convection effects become noticeable. In the near-frozen region a characteristic perturbation method is used to describe the flow near the wave-front.

Time Determination and Time Keeping

1948 ◽  
Vol 1 (2) ◽  
pp. 109-117
Author(s):  
Harold Spencer Jones
Keyword(s):  
Frequency Control ◽  
Rate Of Change ◽  
Time Interval ◽  
The Earth ◽  
Convenient Means ◽  
Time Signals ◽  
Time Determination ◽  
The Mean ◽  
Rotation Of The Earth ◽  
Definite Manner

The rotation of the Earth provides the ultimate standard of time. As the fundamental unit of time we can use either the mean solar day or the sidereal day; these two units are related in a definite manner, so that when one is determined, the other can be inferred. The purpose of any timepiece is to subdivide the day into shorter intervals, and so give the time at any instant. No timepiece will give exact time; the error of the timepiece at some definite instant and the rate of change of that error, or, briefly, the rate, must be determined in order to extrapolate for the correct time at some subsequent instant. The accuracy of the extrapolation will depend upon the uniformity of the rate of the timepiece. Radio time signals sent out from an observatory, which is responsible for the determination and distribution of time, provide the most convenient means for deriving the error and rate of a timepiece. For normal navigational purposes an accuracy of about 0·05 seconds is adequate. But for the purpose of frequency control a very much higher precision is needed—but a precision in time interval rather than in absolute time. Some of the radio-aids to navigation depend upon the accuracy in standardization of frequency, so that high accuracy in time interval has become, indirectly, a navigational requirement.

The ionosphere as a whispering gallery

1962 ◽  
Vol 265 (1323) ◽  
pp. 554-569 ◽  
Keyword(s):  
Electron Density ◽  
Spherical Surface ◽  
Low Frequency ◽  
Electron Density Profile ◽  
Whispering Gallery Modes ◽  
Radio Waves ◽  
Sound Waves ◽  
Whispering Gallery ◽  
The Earth ◽  
Reflexion Coefficient

The propagation of radio waves of very low frequency to great distances is conveniently treated by regarding the space between the earth and the ionosphere as a wave-guide. Several authors have found that the least attenuated modes are profoundly affected by the earth’s curvature. This effect is investigated for several models of the ionosphere. It is found, in particular, that for frequencies greater than about 30 kc/s some modes are possible for which the energy is concentrated in a region near the base of the ionosphere, and the field strength near the ground is small. It is useful to think of such modes as being composed of waves repeatedly reflected at the inside spherical surface of the ionosphere, the rays being chords of this sphere. By analogy with sound waves these modes are called ‘whispering gallery modes’. The theory uses wave admittance and reflexion coefficient variables because these satisfy differential equations which are convenient for integration using a digital computer. The curvature of the earth is allowed for by using the method of the modified refractive index, but the earth’s magnetic field is neglected. Formulae for the m ode condition and the excitation of the various modes by a transmitter are given and discussed. A new way of dealing with an ionosphere having a continuous electron density profile is presented. The results of some numerical calculations are given both for a sharply bounded homogeneous ionosphere and for an exponential profile of electron density.

scholarly journals 40. Investigation of minor meteor streams

1968 ◽  
Vol 33 ◽  
pp. 408-427 ◽  
Author(s):  
A. K. Terenteva
Keyword(s):  
Numerical Integration ◽  
Electronic Computer ◽  
Equations Of Motion ◽  
Time Interval ◽  
List Type ◽  
Type Number ◽  
Meteor Streams ◽  
Long Period ◽  
The Earth ◽  
Meteor Body

The paper consists of three sections: (1)In continuation of a previous paper by the author, on 154 minor meteor streams, elements of orbits and other data are presented for an additional 95 minor streams (most of them less active). These streams have been found both by the studies of the photographic orbits of meteor bodies known before, and from the visual radiants of faint showers.(2)The problems of a possible family of six minor meteor streams associated with the Lexell comet 1770-I, and the connection between nine other minor streams and long-period comets, are examined. The assumption is made that nearly-parabolic comets may be accompanied by meteor streams of considerable width.(3)Radiants and elements of the orbits for 30 meteor bodies of the Cyclids are described, as were established by photographic data. Perturbed motion of one such meteor body is investigated by numerical integration of differential equations of motion on the electronic computer BESM-2, using Cowell's method of quadratures and taking account of perturbations from six planets (Venus–Uranus) and of high-order terms through to the 4th order. Over the time interval studied of 45 years the orbit of the Cyclids has been stable. Perturbing action of the Earth does not lead to any substantial changes in the elements of the orbits. Even at close approaches of the order of 0–003 AU the changes in the angular elements are not greater than about 1°.

On time of the triassic rifts system origin in West Siberia

2019 ◽  
Vol 486 (1) ◽  
pp. 88-92
Author(s):  
K. S. Ivanov ◽  
Yu. V. Erokhin
Keyword(s):  
Climate Change ◽  
West Siberia ◽  
Time Interval ◽  
Short Time Interval ◽  
Earth History ◽  
The Earth ◽  
Rift Zones ◽  
Short Time ◽  
Basalt Magmatism

It is commonly supposed that a very substantial volume of early basalt magmatism effused synchronously on Siberia platform and West Siberia in a very short time interval at 249.4 ± 0.5 Ma (Reichow et al., 2002, etc.). This magmatism and induced climate change are considered as a main reason of the most catastrophic in the Earth history extinction at the border of Permian and Triassic time. But these conclusions were based on incomplete and unrepresentative data on West Siberia. We have obtained by analysis of pyroxenes monofraction from kainotype basalts of Guslinskaya P-430 well Ar-Ar age 268.4 ± 7.5 Ma. In Taurovskaya 503 well this age is 268.1 ± 7.5 Ma. Hence, volcanism in axial rift zones of the basement of West Siberia plate began earlier than that considered before and significantly earlier than on Siberia platform.

Questions on measurements of the Earth’s crustal strain on the basis of GPS data on geodynamic moves of plates after earthquakes

2017 ◽  
Vol 919 (1) ◽  
pp. 40-44
Author(s):  
S.A. Ganiyeva ◽  
J.T. Mehdiyev
Keyword(s):  
Atmospheric Pressure ◽  
Main Shock ◽  
Complete Removal ◽  
Time Interval ◽  
Strong Earthquakes ◽  
The Earth ◽  
Shallow Earthquakes ◽  
Triangular Network ◽  
Gps System

It is well-known that strong shallow earthquakes are usually accompanied with series of aftershocks which can be explained by non-complete removal of strains, collected in the center during the main shock. But in some cases after some time interval the repeated strong earthquake happens in the same place. There are different versions for such repeated earthquakes. It is obvious, that all existing versions require presence or accumulation of strain in the active zone after the main shock which stress out the actuality of development of theoretical and methodological basics for assessment of strains on the basis of experimental data on plates motion. The importance of geodynamic research of remained strain at the Earth crust after strong earthquakes by way of calculation of remained strain on the basis of data plates is noted. It is shown, that utilization of GPS system for determination of shifts of plates could lead to error caused by shifts of GPS stations due to various causes.The consideration of the case where the non-stability of atmospheric pressure is a prevailing factor is reasoned. The related formulas for calculation of strain of the Earth crust on the basis of GPS measurements in the triangular network are given.

scholarly journals Introduction

1992 ◽  
Vol 13 (1) ◽  
pp. xi-xii
Keyword(s):  
Plate Tectonics ◽  
Time Interval ◽  
British Isles ◽  
Late Precambrian ◽  
The Earth ◽  
Iapetus Ocean ◽  
Lower Palaeozoic ◽  
The Subject ◽  
Early Palaeozoic ◽  
Early Maps

AbstractAlmost forty years have elapsed since Leonard Wills published his 'Palaeogeographical Atlas of the British Isles'; those forty years have seen a revolution in the earth sciences which has overturned many earlier ideas in geology. Palaeogeography has been affected just as much as other parts of the subject by this change.The advent of the plate tectonic theory has transformed our ideas of the Lower Palaeozoic palaeogeographical evolution of the British area and has rendered totally obsolete many aspects of Wills' maps. The application of plate tectonics has caused us to produce totally new palaeogeographical models for the late Precambrian and early Palaeozoic, and has emphasised that definitive palaeogeographies for this time interval cannot yet be compiled. Wills was at pains to point out that his Atlas was an 'Aunt Sally' at which to 'hurl one's own and other field observations'-our atlas too must be viewed in that light.The Precambrian and Lower Palaeozoic maps are separated for the northern and southern British Isles areas, because for much of that time the two areas were separated by the Iapetus Ocean. The recognition of important terrane boundaries in Scotland and Ireland has led to our attempt to reconstruct a map from the collage of terranes now in juxtaposition. These early maps owe much to Keith Ingham's experience of the Lower Palaeozoic-Keith would insist here that the maps are very much in the 'Aunt Sally' mould, and that his interpretations may not be able to stand the test of time-but they represent

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