Depth of investigation studies for gradient arrays over homogeneous isotropic half‐space

Geophysics ◽  
1982 ◽  
Vol 47 (8) ◽  
pp. 1198-1203 ◽  
Author(s):  
B. B. Bhattacharya ◽  
Indrajit Dutta
Keyword(s):  
Point Source ◽  
Unit Length ◽  
Radial Distance ◽  
Current Electrode ◽  
Point Electrode ◽  
Maximum Value ◽  
Finite Line ◽  
Infinite Line ◽  
Electrode Systems ◽  
Depth Of Investigation

The depth of investigation of gradient arrays using point, finite, and infinite line sources over homogeneous isotropic ground has been studied. The depth of investigation depends for all cases on the radial distance of the plotting point (i.e., the midpoint of the line joining the potential probes) and separation between the current electrodes. For point electrode systems, it also depends upon azimuth of the plotting point, whereas for finite line electrode systems, it depends upon the azimuth and the length of the line electrode. The depth of investigation at the center of the array is maximum (0.145 L) for infinite line electrodes, decreases to 0.135 L for finite line electrodes of length L, and becomes least (0.125 L) for the point source, where L is the separation between the current electrodes. The depth of investigation for finite line electrodes of unit length L is practically independent of the y‐coordinate which is mathematically the case for infinite line electrode systems. The depth of investigation is least toward the current electrode and increases as one moves away from the current electrode; it ultimately reaches the maximum value of 0.135 L at the center of the system. The depth of investigation for point electrode systems is also minimum near the current electrode and increases with the increase of azimuth for any radial distance.

Distortion in resistivity logging at shallow depth

Geophysics ◽  
1995 ◽  
Vol 60 (4) ◽  
pp. 1058-1069 ◽  
Author(s):  
Tien‐Chang Lee ◽  
Brian N. Damiata
Keyword(s):  
Point Source ◽  
Line Source ◽  
Apparent Resistivity ◽  
Homogeneous Medium ◽  
Radial Distance ◽  
Ground Surface ◽  
Current Electrode ◽  
Potential Electrode ◽  
Resistivity Logging ◽  
Source Array

Owing to the proximity of an insulating ground surface, normal resistivity logging at shallow depths (less than 30 m) can yield an apparent resistivity that exceeds 200% of the formation resistivity for a homogeneous medium. The distortion is more acute for long‐normal than for short‐normal logging. Three examples from a landfill site in southern California are presented to show such distortion. The patterns of distortion are similar for logging devices consisting of either two point‐source electrodes or one point‐source and one finite length, line‐source electrode. The former electrode array is a generally accepted approximation of the latter. However, the simulated apparent resistivity for the line‐source array is greater than that for the point‐source array at any given depth. A resistivity contrast between the formation and the borehole fluid can shift the magnitude of the background apparent resistivity but does not significantly alter the pattern of distortion. The magnitude of the distortion can be reduced by placing the reference‐ground potential electrode at a radial distance that is about equal to the spacing between the downhole upper potential electrode and the upper current electrode. It can also be removed by including the radial distance in an array‐dependent geometric factor that accounts for the resistivity of the borehole fluid and the proximity of the logging device to the ground surface.

Elastohydrodynamic Lubrication of Finite Line Contacts

1983 ◽  
Vol 105 (4) ◽  
pp. 598-604 ◽  
Author(s):  
A. Mostofi ◽  
R. Gohar
Keyword(s):  
Elastohydrodynamic Lubrication ◽  
Mineral Oil ◽  
Pressure Variation ◽  
Material Parameters ◽  
Line Contacts ◽  
Finite Line ◽  
Moderate Load ◽  
Infinite Line ◽  
Cylindrical Roller ◽  
Theoretical Results

In this paper, a numerical solution to the elastohydrodynamic lubrication (EHL) problem is presented for a cylindrical roller with axially profiled ends, rolling over a flat plane. Convergence was obtained for moderate load and material parameters (glass, steel, and a mineral oil). Isobars, contours, and section graphs, show pressure variation and film shape. Predictions of film thickness compare favorably with experiments which use the optical interference method, as well as with other theoretical results for an infinite line contact, or an ellipse having a long slender aspect ratio. The maximum EHL pressure occurs near the start of the profiling and can exceed pressure concentrations there predicted by elastostatic theory.

Numerical Modeling of Mud Invasion Profile Based on the Well Logging with the Shallow Depth of Investigation

2012 ◽  
Vol 524-527 ◽  
pp. 148-151
Author(s):  
Yuan Zhong Zhang ◽  
Xiu Ying Miao
Keyword(s):  
Numerical Modeling ◽  
Dynamic Process ◽  
Water Saturation ◽  
Radial Distance ◽  
Well Logging ◽  
Shallow Depth ◽  
Borehole Wall ◽  
Drilling Mud ◽  
Invasion Depth ◽  
Depth Of Investigation

The drilling mud invasion is a dynamic process varying with time and reveal the permeability or the relatively permeability of the formation saturated with fluid. The mud invasion profile denotes the water saturation change with the radial distance from the borehole wall. The logging with the shallow depth of investigation (DOI), such as density logging, neutron logging and shallow electrical logging, often detects the information of the flushed zone. We chose DOI logging to model the slope invasion profile with the hyperbolic secant function, and the calculated logging reading comparing from the real logging reading to optimize the invasion profile. The results show that the mud invasion profile and the invasion depth are strongly affected by porosity, where the invasion depth reduces with porosity adding.

scholarly journals Modelling the thermal radiation from kitchen hob fires

2020 ◽  
Vol 38 (4) ◽  
pp. 377-394
Author(s):  
Michael Spearpoint ◽  
Charlie Hopkin ◽  
Danny Hopkin
Keyword(s):  
Heat Flux ◽  
Point Source ◽  
Radial Distance ◽  
Source Model ◽  
View Factor ◽  
Calculation Methods ◽  
Fire Dynamics ◽  
Potential Threat ◽  
Computational Tools

Kitchen hob fires present a potential threat to occupants escaping from dwellings and calculations may be needed to assess the hazard. Determination of the thermal heat flux from flames to a target can be achieved through the use of hand calculation methods or computational tools. This article compares point source, parallel plane and cylindrical view factor hand calculations and computational simulations using B-RISK and Fire Dynamics Simulator of thermal heat flux with kitchen hob fire experiments presented in the literature. Knowing the level of accuracy of each method provides useful information to designers. Although the point source model is influenced by whether the radial distance is measured perpendicular to the heat flux target or is offset relative to the centre of the flame, the article concludes that it provides an adequate approach for the calculation of thermal heat flux in the case of kitchen hob fires.

scholarly journals Analisa Gaya Penekanan pada Proses ECAP Batang Kuningan CuZn 70/30

2019 ◽  
Vol 8 (1) ◽  
pp. 39-46
Author(s):  
Suryadi ◽  
Amin Suhadi ◽  
Dedi Priadi ◽  
E. S. Siradj
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Unit Length ◽  
Area Under The Curve ◽  
Pressing Force ◽  
The Third ◽  
Angular Pressing ◽  
Maximum Value ◽  
First Pass ◽  
Fourth Pass

Telah dilakukan percobaan severe plastic deformation (SPD) dengan metodeequal channel angular pressing (ECAP) pada batang kuningan CuZn 70/30 diameter 10 mm sampai 5 pas. Gaya penekanan meningkat secara signifikan pada awal langkah penekanan dan mencapai nilai maksimum lalu melandai. Pada pas pertama gaya penekanan mencapai 115 kN, pas kedua 130 kN, pas ketiga mecapai 150 kN dan pada pas keempat 165 kN. Dari pengukuran luas area di bawah kurva gaya penekanan diperoleh energi total pembentukan pada proses ECAP batang kuningan persatuan panjang adalah 95 Joule/mm pada pas pertama, sampai 130 Joule/mm pada pas ketiga, dan turun 125 Juole/mm pada pas keempat. Secara kumulatif total energi persatuan panjang meningkat secara linier sesuai dengan peningkatan jumpah pas, dimana pada pas keempat mencapai 597 MPa. Peningkatan gaya penekanan dan energi penekanan sebanding dengan terjadinya peningkatan kekerasan pada batang kuningan dan terjadinya penghalusan butir.Kata kunci: ECAP, gaya penekanan, energi pembentukan, kekerasan, penghalusan butir, kuningan.AbstractExperiments of severe plastic deformation (SPD) have been carried out by the method of equal channel angular pressing (ECAP) on brass rods CuZn 70/30 diameter 10 mm to 5 pas. Pressing force significantly is increased emphasis on early steps and reaches a maximum value and then ramp. At the first pas the pressing force reached 115 kN, the second pass 130 kN, the third pass 150 kN and fouth pass is 165. From measurements of the area under the curve of pressing force, the total forming energy per unit length generated to form the brass rod in ECAP is 95 Joule / mm at the first pass, 130 Joules / mm at third pass and down to 125 Joule/mm at fouth pass. Cumulatively, the total forming energy per unit length increases linearly according to the increase in number of ECAP pass, where the fourth pass reach 597 Joule/mm. Increased emphasis pressing load and forming energy is proportional to the increase in hardness of the brass rod and the grain refinement.Keywords: ECAP, pressing load, forming energy, hardness, grain refinement, Brass

THE COSMIC STRINGS GENERATED FROM THE TORSION

1993 ◽  
Vol 08 (06) ◽  
pp. 491-501 ◽  
Author(s):  
TAKEHIKO T. FUJISHIRO ◽  
MITSUO J. HAYASHI ◽  
SHOJI TAKESHITA
Keyword(s):  
Cosmic Strings ◽  
Unit Length ◽  
Three Dimensional ◽  
Fine Tuning ◽  
Crystalline Solid ◽  
Dimensional Model ◽  
Einstein Theory ◽  
Maximum Value ◽  
Deficit Angle ◽  
Space Time Structure

The cosmic strings can be described naturally by torsion formalism which has a direct analogy with dislocations in three-dimensional crystalline solid. We have obtained an exact solution in a four-dimensional model on M2×T2 and may be expected to describe a space-time structure of our universe. The relation between the mass per unit length and the deficit angle are different from that of the Einstein theory, but can be made consistent since our model could reproduce its prediction. We could also obtain the maximum value of the mass per unit length µ~10−6(~1022 g/cm ) by fine tuning of a parameter, which is consistent with the recent observations.

Axial Distribution Profile of Magnetic Field and Plasma Sheath Velocity in Argon Plasma Focus Device

2015 ◽  
Vol 11 (2) ◽  
pp. 2990-3000 ◽  
Author(s):  
Hanaa Elshamy
Keyword(s):  
Magnetic Field ◽  
Plasma Focus ◽  
Radial Distance ◽  
Plasma Sheath ◽  
Azimuthal Magnetic Field ◽  
Plasma Current Sheath ◽  
Argon Gas ◽  
Maximum Value ◽  
Axial Acceleration ◽  
Gas Pressures

The main aim of this work is to study dynamics of plasma current sheath, PCS during the axial acceleration phase in term of its axial velocity, Vz and the induced azimuthal magnetic field induction, Bθ in 2.2 KJ plasma focus, PF device of Mather type. It powered by a capacitor bank of 30 µf capacity with charging voltage of 12 KV. In the present paper all the experimental work are performed for Argon gas pressure in the range of 0.2 – 1.8 Torr. The length of the inner electrode, IE has been changed to 9.5, 10.5 and 11.5 cm respectively. To detect, Bθ and Vz three identical magnetic probes are located at radial distance r1 = 2.75 cm, r2 = 3.5 cm and r3 = 4.25 cm from the IE axis and at axial distance z = 8.15 cm from coaxial electrodes breech.The dependence of Vz and Bθ on gas pressures are measured and the results of them clear that, Vz is decayed with increasing of gas pressures and it has a maximum value for IE length of 10.5 cm, P = 0.2 Torr and at r1, while Bθ has a maximum value for IE length = 11.5 cm, 1.2 Torr at r1 . Also distribution of Vz with p in linear fitting shows that efficient a snow-plough action is obtained approximately for IE length = 10.5 cm. Results of Vz versus radial distance demonstrated that the PCS has a parabolic shape especially at lower Argon gas pressures. Results of modification factor, F as a function of gas pressures show that at IE = 10.5 cm, r1 and for most Argon gas pressures F has a higher values than any others IE lengths and radial distances. Also the decay of dF/dp along radial distances has a smaller values at IE length = 11.5 cm than any other lengths (9.5 and 10.5 cm).

APPARENT RESISTIVITY CURVES FOR AN INFINITE LINE SOURCE PARALLEL TO AN INCLINED CONTACT

Geophysics ◽  
1975 ◽  
Vol 40 (4) ◽  
pp. 689-693 ◽  
Author(s):  
Sri Niwas ◽  
S. K. Upadhyay
Keyword(s):  
Point Source ◽  
Line Source ◽  
Apparent Resistivity ◽  
Master Curves ◽  
Harmonic Method ◽  
Resistivity Data ◽  
Infinite Line

Investigations of apparent resistivity due to a point source over an inclined contact have been reported by Aldredge (1937), Unz (1953), Maeda (1955), and Chastenet de Gery and Kunetz (1956). In these investigations either the image or the harmonic method has been utilized. In this note, we propose to solve the same problem as follows: (1) Transform point‐source potential data into line‐source apparent resistivity data. (2) Interpret transformed apparent resistivities by the master curves provided.

Seismic waves from finite faults in layered media

1979 ◽  
Vol 69 (6) ◽  
pp. 1693-1714
Author(s):  
F. Abramovici ◽  
J. Gal-Ezer
Keyword(s):  
Point Source ◽  
Half Space ◽  
Seismic Waves ◽  
Time Dependent ◽  
Homogeneous Layer ◽  
Two Dimensional ◽  
Homogeneous Half Space ◽  
Finite Line ◽  
Finite Line Source ◽  
Time Dependent Solution

abstract The time-dependent solution for a multipolar source in a structure consisting of a homogeneous layer over a homogeneous half-space is obtained as a sum of generalized rays. Numerical seismograms are calculated for a horizontal strikeslip and a horizontal dip-slip for a point-source, a finite line-source, and a finite two-dimensional source in the form of a rectangle. For comparison, the displacements in a homogeneous space and half-space are also calculated. The seismograms for finite sources are similar to those for a point-source but show less conspicuous phases, the arriving pulses being wider and less sharp.

Physical Interpretations of the Instabilities Encountered in the Deflection Equations of the Unconstrained Pipeline

1976 ◽  
Vol 98 (3) ◽  
pp. 1099-1102
Author(s):  
G. C. Daley
Keyword(s):  
Differential Equations ◽  
Parametric Study ◽  
Flexural Rigidity ◽  
Unit Length ◽  
Vertical Force ◽  
Continuous Beam ◽  
Pipeline Construction ◽  
Sea Floor ◽  
Maximum Value

For a pipeline modeled as having constant rigidity, horizontal tension, and submerged weight per unit length, there is a maximum value that the maximum sag-bend moment attains as the distance from the pin-supported end of the pipe to the sea floor increases. This paper presents the results of a parametric study analyzing a pipeline displaced from the sea floor to some pipeline construction configuration. The pipeline is modeled as a continuous beam having constant submerged weight per unit length and a constant horizontal tension or force with one end supported vertically by the sea floor. The governing differential equations are solved in terms of dimensionless combinations of the three characteristic variables—the submerged weight per unit length, the flexural rigidity, and the constant horizontal tension. This allows any possible pipeline configuration meeting stated constraints to be analyzed. The analysis performed specifies the maximum sag-bend moment. This maximum sag-bend moment is changed by varying the sea floor vertical force until a further change in sea floor reaction does not give a pipeline configuration. This maximum attainable maximum sag-bend moment is then computed and graphed as a function of the three characteristic pipeline values, the horizontal tension, the flexural rigidity, and the submerged weight per unit length.

Sign in / Sign up

Export Citation Format

Share Document