scholarly journals Evaluation of lithostratigraphic units and groundwater potential using the resolution capacities of two different electrical tomographic electrodes at dual-spacing

2021 ◽  
Vol 51 (4) ◽  
pp. 295-320
Author(s):  
Adedibu Sunny AKINGBOYE ◽  
Andy Anderson BERY
Keyword(s):  
Stainless Steel ◽  
Groundwater Potential ◽  
Silty Sand ◽  
Electrode Spacing ◽  
Groundwater Abstraction ◽  
Copper Electrodes ◽  
Lithostratigraphic Units ◽  
Data Points ◽  
The University ◽  
Relative Differences

The selection of a choice electrode is pertinent to attenuating noise and improving geophysical tomographic inversion results. Besides, the detailed understanding of the geodynamic condition of subsurface formation is crucial to sustainable potable groundwater abstraction. Hence, the subsurface lithostratigraphic units and groundwater potential of two sites (i.e., Site 1 and Site 2) within the Universiti Sains Malaysia were evaluated using borehole-constrained electrical resistivity tomography (ERT) and induced polarisation (IP) tomography. Both methods employed the resolution capacities of stainless-steel and copper electrodes at dual-spacing. The ERT and IP field data and inversion results for copper electrodes were generally robust due to the generated higher positive data points and lower RMS errors, percentage relative differences, and mean absolute percentage errors (MAPE) than the stainless-steel electrodes, especially at Site 1 with a profile length of 200 m and an electrode spacing of 5 m. However, both electrodes tend to produce inversion models with almost the same parameters at Site 2, using half the profile length and electrode spacing of Site 1, i.e., 100 m and 2.5 m, respectively. Thus, the sensitivities and resolution capacities of the tomographic electrodes are heavily influenced by electrode spacing, profile length, amount of injected current, and depth of investigation. The borehole lithostratigraphic units, typically sandy silt, sand, and silty sand, have good correlations with the ERT and IP inversion results. The variability in observed resistivity and chargeability values were due to heterogeneous weathered materials and saturating water fills within the fractured and deeply-weathered granitic bedrock, with <200 Ωm and a chargeability of >1.8 msec. The models' median depth of >40 m mapped for the weathered and/or fractured sections was suggestive of high groundwater-yielding capacity in boreholes to sustain a part of the university community. 

scholarly journals Performance Evaluation of Copper and Stainless-steel Electrodes in Electrical Tomographic Imaging

2021 ◽  
Vol 32 (3) ◽  
pp. 13-29
Author(s):  
Adedibu Sunny Akingboye ◽  
◽  
Andy Anderson Bery ◽  
◽  
Keyword(s):  
Stainless Steel ◽  
Performance Evaluation ◽  
Reference Model ◽  
Electrode Spacing ◽  
Percentage Error ◽  
Data Inversion ◽  
Copper Electrodes ◽  
Rms Error ◽  
Conventional Stainless Steel ◽  
Steel Electrodes

Geophysicists use electrical methods to investigate and characterise the earth’s subsurface geology. This study aims to evaluate the performance of copper and conventional stainless-steel electrodes in subsurface tomographic investigations using electrical resistivity tomography (ERT) and induced polarisation (IP) at two sites in Penang, Malaysia. Site 1 and Site 2 employed profile lengths of 200 m and 100 m, with electrodes spacing of 5.0 m and 2.5 m, respectively. In the results of the final data inversion, it was observed that the ERT and IP tomographic models of Site 1 have the best convergence limits with percentage relative differences (copper as reference model) ranging from –70% to 70%, while Site 2 recorded –8% to 8%. The electrodes performance evaluation showed that population root mean square (RMS) error and population mean absolute percentage error (MAPE) of data points between copper and stainless-steel electrodes yielded large values for Site 1 with values above 28% and that of Site 2 was less than 4%. Hence, copper (good electrical conductivity and non-polarisable) electrodes have improved the quality and quantity of infield data which give low values of population RMS error and population MAPE compared to conventional stainless-steel electrodes, especially for large unit electrode spacing surveys. Most notably, this work has contributed to the understanding of the capability of copper electrodes in providing precise and reliable inversion models for subsurface tomographic investigations in pre- and post-land uses (engineering work), hydrogeology/groundwater, environmental studies, etc.

scholarly journals RETRACTED: Polymorphisms in the 5-HTTLPR Gene Mediate Storage Capacity of Visual Working Memory

2012 ◽  
Vol 24 (5) ◽  
pp. 1069-1076 ◽  
Author(s):  
David E. Anderson ◽  
Theodore A. Bell ◽  
Edward Awh
Keyword(s):  
Working Memory ◽  
Visual Working Memory ◽  
Cognitive Neuroscience ◽  
Storage Capacity ◽  
Research Misconduct ◽  
Research Integrity ◽  
Settlement Agreement ◽  
Office Of Research Integrity ◽  
Data Points ◽  
The University

By the request of the authors, the following two research articles will be retracted from the Journal of Cognitive Neuroscience: 1. Anderson, D. E., Ester, E. F., Klee, D., Vogel, E. K., & Awh, E. (2014). Electrophysiological evidence for failures of item individuation in crowded visual displays. Journal of Cognitive Neuroscience, 26(10), 2298– 2309. https://dx.doi.org/10.1162/jocn_a_00649 . 2. Anderson, D. E., Bell, T. A., & Awh, E. (2012). Polymorphisms in the 5-HTTLPR gene mediate storage capacity of visual working memory. Journal of Cognitive Neuroscience, 24(5), 1069–1076. https://dx.doi. org/10.1162/jocn_a_00207 . On August 1, 2015, the Office of Research Integrity (ORI) announced a settlement agreement with David E. Anderson, the Respondent ( http://ori.hhs.gov/content/ case-summary-anderson-david ). On the basis of the Respondent’s admission and an analysis by the University of Oregon, ORI concluded that the Respondent had engaged in research misconduct by falsifying and/or fabricating data in four publications. Those publications were retracted immediately after the release of the ORI findings. Since that time, additional problems have been discovered with Article 1 above. Data points shown in Figure 8 were removed without justification and in contradiction to the analytic approach described in the methods and results. In light of this discovery and of the previous ORI findings, authors Bell and Awh no longer have confidence in the integrity of the data in Article 2. For these reasons, all authors on both articles (including the Respondent) have agreed to the retraction of Articles 1 and 2 above.

scholarly journals Evaluation of groundwater potentials of Orogun, South–South part of Nigeria using electrical resistivity method

2019 ◽  
Vol 9 (8) ◽  
Author(s):  
Sixtus Nwachukwu ◽  
Rasaq Bello ◽  
Ayomide O. Balogun
Keyword(s):  
Electrical Resistivity ◽  
Groundwater Potential ◽  
Electrical Anisotropy ◽  
Electrode Spacing ◽  
Electrical Resistivity Survey ◽  
Resistivity Method ◽  
Transverse Resistance ◽  
Hydrocarbon Sources ◽  
Electrical Resistivity Method ◽  
Dar Zarrouk Parameters

Abstract An investigation has been made of the groundwater potentials of Orogun Town, Ughelli North Local Government Area of Delta State, Nigeria, using electrical resistivity survey. This study motivated to determine electrical resistivity parameters of the area. The aim of this work is to use electrical resistivity method to explore the groundwater potentials of Orogun Town with the determination of its Dar Zarrouk parameters. A total of eight vertical electrical sounding (VES) were conducted with maximum electrode spacing of 150 m. The data were acquired using ABEM SAS 4000 Terrameter and processed using IPI2win and Interpex softwares. The groundwater potentials of the area are evaluated based on the longitudinal conductance (S), transverse resistance (T), coefficient of electrical anisotropy (λ), resistivity for the formation ($$\rho_{\text{m}}$$ρm), reflection coefficient (RC) and resistivity contrast (FC). The results reveal four subsurface geoelectric layers in seven of the eight VES while one VES revealed three subsurface geoelectric layers. Resistivity values for all the layers in the study area are very high, higher than what is expected in a sedimentary basin as we have in the study area. The resistivity values range from 8470 Ωm (layer 1, VES 7) to 118,030,000 Ωm (layer 3, VES 8). Depth to aquifer in the study area ranged from 1.61 m (VES 2) to 12.41 m (VES 1), while resistivity values of the aquifer ranged from 64,182 Ωm (VES 3) to 118,030,000 Ωm (VES 8). The results from the formation parameters evaluated showed that the area has good groundwater potential but might have been highly contaminated, especially from hydrocarbon sources and other man-made pollutants. The suggested contamination of the aquifer is as a result of the high values of resistivity of the aquifer layers.

Book Reviews

2012 ◽  
Vol 50 (3) ◽  
pp. 809-818
Keyword(s):  
Economic Development ◽  
Los Angeles ◽  
The United States ◽  
Factor Endowments ◽  
University Of Wisconsin ◽  
European Colonization ◽  
The University ◽  
Relative Differences

Jeffrey G. Williamson of Harvard University and University of Wisconsin reviews “Economic Development in the Americas since 1500: Endowments and Institutions” by Stanley L. Engerman and Kenneth L. Sokoloff. The EconLit abstract of the reviewed work begins: Eleven papers explore differences in the rates of economic growth in Latin America and mainland North America, specifically the United States and Canada, and consider how relative differences in growth over time are related to differences in the institutions that developed in different economies. Papers discuss paths of development -- an overview; factor endowments and institutions; the role of institutions in shaping factor endowments; the evolution of suffrage institutions; the evolution of schooling – 1800–1925; inequality and the evolution of taxation; land and immigration policies; politics and banking systems; five hundred years of European colonization; institutional and noninstitutional explanations of economic development; and institutions in political and economic development. Engerman is John H. Munro Professor of Economics and Professor of History at the University of Rochester. The late Sokoloff was Professor in the Department of Economics at the University of California, Los Angeles. Bibliography; index.

Experimental Characterization of Microstructure Evolution in Austenitic Stainless Steel With Phase Transformation

2008 ◽  
Author(s):  
Allison Beese ◽  
Dirk Mohr
Keyword(s):  
Stainless Steel ◽  
Phase Transformation ◽  
Magnetic Induction ◽  
Volume Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Martensite Content ◽  
Initial Anisotropy ◽  
Induction Technique ◽  
Relative Differences

The phase transformation in cold-rolled stainless steel 301LN sheets is investigated experimentally. A series of uniaxial experiments is performed to investigate the effect of initial anisotropy on the martensitic transformation kinetics. Three methods are employed to measure the martensite content: (1) X-ray diffraction, (2) micrography and (3) magnetic induction. The first two methods require interrupted tests while the third method allows for the in-situ detection of changes of the martensite volume ratio. All three methods show that the rate of austenite-to-martensite transformation is loading direction dependent. In particular, the magnetic induction technique appears to be sufficiently sensitive to detect these relative differences. However, the results also show that the determination of the absolute martensite volume content can only be quantified with poor accuracy due to the limited accuracy of X-ray diffraction and micrography.

scholarly journals Evaluation of Aquifer Protective Capacity and Groundwater Potential in Part of Iju, Akure-North, Ondo State, Nigeria

2020 ◽  
pp. 197-204
Author(s):  
A. Olajide ◽  
S. Bayode ◽  
T. Fagbemigun ◽  
A. Oyebamiji ◽  
J. Amosun ◽  
...  
Keyword(s):  
Geophysical Methods ◽  
Low Frequency ◽  
Groundwater Potential ◽  
Electrode Spacing ◽  
Protective Capacity ◽  
Value Range ◽  
Weathered Layer ◽  
Ondo State ◽  
Geological Units ◽  
Matching Techniques

Groundwater potential and aquifer protective capacity of the overburden unit was evaluated in part of Iju, Akure North, Ondo State using integrated geophysical methods involving Very Low Frequency Electromagnetic (VLF-EM) profiling and Vertical Electrical Sounding (VES). Four major traverses were established of varying length extents. The VLF-EM measurements were taken along the four major profiles of 10 m station interval.Forty two (42) Vertical Electrical Soundings were also conducted with half electrode spacing varying between 1 and 100 m and interpretation was done using the partial curve matching techniques and computer aided iteration. Five subsurface geological units were identified from geoelectric sections, consisting of the top soil, lateritic, weathered, partly weathered and fresh basement layers consecutively. For the first layer, resistivityranges between 23 and 323 Ωm with values of thickness ranging between 0.5 and 2.2 m. The resistivity and thickness of the second (lateritic) layer range from 132 to 430 Ωm and 1.6 to 4 m respectively. The resistivity of the weathered layer ranges from 4 to 94 Ωm and variable thickness between 10 and 24.4 m. The fourth layer has a resistivity value range of 65 to 120 Ωm and thicknesses between 20 and 30 m. The basement bedrock (fifth layer) has resistivity values between 770 and 820 Ωm. The depth to bedrock ranges from 1.8 to 31 m. The geophysical data and the basement aquifer delineated were then used to evaluate the hydrogeological setting and aquifer protective capacity of the study area. The observation from the results shows that close to 70 % of the study area falls within the zones of low groundwater potential, 25 % falls within medium potential zones while only 5 % make up the high potential zones. 75 % of the study area constituted the weak to poor protective capacity zones.  

scholarly journals Effect of Soil Types on The Development of Matric Suction and Volumetric Water Content for Dike Embankment During Overtopping Tests

2018 ◽  
Vol 4 (3) ◽  
pp. 668 ◽  
Author(s):  
Marwan Adil Hassan ◽  
Mohd Ashraf Mohamad Ismail
Keyword(s):  
Water Content ◽  
Water Flow ◽  
Fine Particles ◽  
Side Wall ◽  
Matric Suction ◽  
Volumetric Water Content ◽  
Silty Sand ◽  
Soil Types ◽  
The Stability ◽  
The University

The resistance of dike materials has a great effect on the development of hydraulic engineering around the world. It helps to understand the mechanism of dike failure occurred due to the influence of hydraulics and Geotechnical parameters. The overtopping moment is one of the main failures that reduces the stability of the dike embankment through initiating the breach channel inside dike crest as a result of water flow above the downstream slope of the dike. Two spatial overtopping tests were conducted at in Hydraulic Geotechnical laboratories at the University Sains of Malaysia to observe the evolution of matric suction and volumetric water content for two soil types of sand and very silty sand soils. A pilot channel was cut in dike crest along the side wall of the small flume channel to represent the transition water flow from upstream into downstream slopes during overtopping test. The results indicated that the matric suction decreases due to the increase of volumetric water content during the saturation of dike body. The proportion increasing and decreasing of volumetric water content and matric suction is lower in very silty sand than those in sand soil due to the presence of fine particles in previous soil.

Use of Cr K-Beta X-Rays and Position Sensitive Detector for Residual Stress Measurement in Stainless Steel Pipe

1978 ◽  
Vol 22 ◽  
pp. 247-249 ◽  
Author(s):  
C. O. Ruud ◽  
C. S. Barrett
Keyword(s):  
Stainless Steel ◽  
Stress Measurement ◽  
Steel Pipe ◽  
X Rays ◽  
University Of Denver ◽  
Stainless Steel Pipe ◽  
Position Sensitive ◽  
The University ◽  
Research Institute

Residual stresses on the inner surface of stainless steel pipe used in nuclear reactors are of exceptional importance. Apparatus for measuring these in situ, in welded lengths of 10-inch diameter austenitic (304) stainless pipe has been developed at the University of Denver Research Institute under the sponsorship of the Electric Power Research Institute.

scholarly journals Geoelectric evaluation of groundwater potential: a case study at Omuma local government area, Rivers State, Nigeria

2020 ◽  
Vol 10 (8) ◽  
pp. 3255-3261
Author(s):  
M. E. Abbey ◽  
D. E. Onyebueke
Keyword(s):  
Local Government ◽  
Water Scarcity ◽  
Groundwater Potential ◽  
Local Government Area ◽  
Subsurface Water ◽  
Electrode Spacing ◽  
Average Depth ◽  
Subsurface Layers ◽  
Rivers State

Abstract Rivers State as the nomenclature depicts is a state richly blessed with both surface and subsurface water. As a result of this, there is less problem of water scarcity, especially in the elite cities of the state, but so many other communities due to one reason or the other still wallow in abject water scarcity. In this survey, a total of seven (7) vertical electric soundings were carried out using Schlumberger configuration at Obibi community in Omuma local government area, Rivers State, to ascertain the location and depths to aquifer. ABEM terrameter SAS 300 was used in the survey with electrode spacing AB/2 of 150 m, thus probing to a depth of about 200 m. Geoelectric software (IPI2WIN) was utilized in the plotting, iteration and interpretation of the resistivity data obtained. From the quantitative interpretation and the lithology of the areas, five different subsurface layers were delineated with their geoelectric curve given as AK, AKQ and AKH. Aquifer in these areas is highly prolific and mostly located at an average depth of 52 m.

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