Open Access. Powered by Scholars. Published by Universities.®

Geological Engineering Commons

Open Access. Powered by Scholars. Published by Universities.®

1,014 Full-Text Articles 2,472 Authors 562,848 Downloads 71 Institutions

All Articles in Geological Engineering

Faceted Search

1,014 full-text articles. Page 14 of 45.

Seismic Azimuthal Anisotropy Beneath A Fast Moving Ancient Continent: Constraints From Shear Wave Splitting Analysis In Australia, Kailun Ba, Stephen S. Gao, Jianguo Song, Kelly H. Liu 2023 Missouri University of Science and Technology

Seismic Azimuthal Anisotropy Beneath A Fast Moving Ancient Continent: Constraints From Shear Wave Splitting Analysis In Australia, Kailun Ba, Stephen S. Gao, Jianguo Song, Kelly H. Liu

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Seismic Azimuthal Anisotropy Beneath Australia is Investigated using Splitting of the Teleseismic PKS, SKKS, and SKS Phases to Delineate Asthenospheric Flow and Lithospheric Deformation Beneath One of the Oldest and Fast-Moving Continents on Earth. in Total 511 Pairs of High-Quality Splitting Parameters Were Observed at 116 Seismic Stations. Unlike Other Stable Continental Areas in Africa, East Asia, and North America, Where Spatially Consistent Splitting Parameters Dominate, the Fast Orientations and Splitting Times Observed in Australia Show a Complex Pattern, with a Slightly Smaller Than Normal Average Splitting Time of 0.85 ± 0.33 S. on the North Australian Craton, the Fast …


Coreflooding Evaluation Of Fiber-Assisted Recrosslinkable Preformed Particle Gel Using An Open Fracture Model, Shuda Zhao, Ali Al Brahim, Junchen Liu, Baojun Bai, Thomas P. Schuman 2023 Missouri University of Science and Technology

Coreflooding Evaluation Of Fiber-Assisted Recrosslinkable Preformed Particle Gel Using An Open Fracture Model, Shuda Zhao, Ali Al Brahim, Junchen Liu, Baojun Bai, Thomas P. Schuman

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Recrosslinkable Preformed Particle Gels (RPPGs) Have Been Used to Treat the Problem of Void Space Conduits (VSC) and repair the "Short-Circuited" Waterflood in Alaska's West Sak Field. Field Results Showed a 23% Increase in Success Rates over Typical Preformed Particle Gel (PPG) Treatments. in This Paper, We Evaluated Whether Adding Fiber into RPPGs Can Increase the RPPG Plugging Efficiency and Thus Further Improve the Success Rate. We Designed Open Fracture Models to Represent vs.C and Investigated the Effect of Swelling Ratio (SR), Fracture Size, and Fiber Concentration on Gel Injection Pressure, Water Breakthrough Pressure, and Permeability Reduction. Results Show that …


A Systematic Design Approach For Bulk Gel Treatments Based On Gel Volume-Concentration Ratio In Field Projects, Munqith Aldhaheri, Mingzhen Wei, Baojun Bai 2023 Missouri University of Science and Technology

A Systematic Design Approach For Bulk Gel Treatments Based On Gel Volume-Concentration Ratio In Field Projects, Munqith Aldhaheri, Mingzhen Wei, Baojun Bai

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Controlling excessive water production in mature oil fields has always been a desired objective of the oil and gas industry. This objective calls for planning of more effective water-control gel treatments with optimized designs to obtain more attractive outcomes. Unfortunately, planning such effective treatments remains a dilemma for reservoir engineers due to the lack of methodical design tools in the industry. This paper presents a novel systematic design approach for polyacrylamide-based bulk gel treatments by classifying their field projects according to the gel volume-concentration ratio (VCR) into three design types. In terms of one another, the approach estimates either the …


Wildfire Risk Zone Mapping In Contrasting Climatic Conditions: An Approach Employing Ahp And F-Ahp Models, Aishwarya Sinha, Suresh Nikhil, Rajendran Shobha Ajin, Jean Homian Danumah, Sunil Saha, Romulus Costache, Ambujendran Rajaneesh, Kochappi Sathyan Sajinkumar, Kolangad Amrutha, Alfred Johny, Fahad Marzook, Pratheesh Chacko Mammen, Kamal Abdelrahman, Mohammed S. Fnais, Mohamed Abioui 2023 Symbiosis Institute of Geoinformatics

Wildfire Risk Zone Mapping In Contrasting Climatic Conditions: An Approach Employing Ahp And F-Ahp Models, Aishwarya Sinha, Suresh Nikhil, Rajendran Shobha Ajin, Jean Homian Danumah, Sunil Saha, Romulus Costache, Ambujendran Rajaneesh, Kochappi Sathyan Sajinkumar, Kolangad Amrutha, Alfred Johny, Fahad Marzook, Pratheesh Chacko Mammen, Kamal Abdelrahman, Mohammed S. Fnais, Mohamed Abioui

Michigan Tech Publications, Part 1

Wildfires are one of the gravest and most momentous hazards affecting rich forest biomes worldwide; India is one of the hotspots due to its diverse forest types and human-induced reasons. This research aims to identify wildfire risk zones in two contrasting climate zones, the Wayanad Wildlife Sanctuary in the Western Ghats and the Kedarnath Wildlife Sanctuary in the Himalayas, using geospatial tools, analytical hierarchy process (AHP), and fuzzy-AHP models to assess the impacts of various conditioning factors and compare the efficacy of the two models. Both of the wildlife sanctuaries were severely battered by fires in the past, with more …


Lysine Crosslinked Polyacrylamide─A Novel Green Polymer Gel For Preferential Flow Control, Tao Song, Baojun Bai, Yugandhara Eriyagama, Thomas P. Schuman 2023 Missouri University of Science and Technology

Lysine Crosslinked Polyacrylamide─A Novel Green Polymer Gel For Preferential Flow Control, Tao Song, Baojun Bai, Yugandhara Eriyagama, Thomas P. Schuman

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Acrylamide-based polymer gels have been applied to control the preferential flow in the subsurface for decades. However, some commonly used crosslinkers, such as Cr (III) and phenol-formaldehyde, are highly toxic and are being phased out because of stringent environmental regulations. This work uses l-lysine as the green crosslinker to produce acrylamide-based polymer gels. This article systematically studied the effect of lysine and polymer concentration, salinity, pH, and temperature on gelation behavior and thermal stability. Besides, the gelation mechanism and crosslinking density were elucidated in this work. A high-permeability sandstone core was used to test the plugging efficiency of this novel …


Version 2 Of The Global Catalogue Of Large Anthropogenic And Volcanic So2 Sources And Emissions Derived From Satellite Measurements, Vitali E. Fioletov, Chris A. McLinden, Debora Griffin, Ihab Abboud, Nickolay Krotkov, Peter J.T. Leonard, Can Li, Joanna Joiner, Nicolas Theys, Simon Carn 2023 Environment and Climate Change Canada

Version 2 Of The Global Catalogue Of Large Anthropogenic And Volcanic So2 Sources And Emissions Derived From Satellite Measurements, Vitali E. Fioletov, Chris A. Mclinden, Debora Griffin, Ihab Abboud, Nickolay Krotkov, Peter J.T. Leonard, Can Li, Joanna Joiner, Nicolas Theys, Simon Carn

Michigan Tech Publications, Part 1

Sulfur dioxide (SO2) measurements from the Ozone Monitoring Instrument (OMI), Ozone Mapping and Profiler Suite (OMPS), and TROPOspheric Monitoring Instrument (TROPOMI) satellite spectrometers were used to update and extend the previously developed global catalogue of large SO2 emission sources. This version 2 of the global catalogue covers the period of 2005-2021 and includes a total of 759 continuously emitting point sources releasing from about 10 ktyr-1 to more than 4000 ktyr-1 of SO2, that have been identified and grouped by country and primary source origin: volcanoes (106 sources); power plants (477); smelters (74); and sources related to the oil and …


Underestimated Passive Volcanic Sulfur Degassing Implies Overestimated Anthropogenic Aerosol Forcing, U. A. Jongebloed, A. J. Schauer, J. Cole-Dai, C. G. Larrick, R. Wood, T. P. Fischer, S. A. Carn, S. Salimi, S. R. Edouard, S. Zhai, L. Geng, B. Alexander 2023 University of Washington

Underestimated Passive Volcanic Sulfur Degassing Implies Overestimated Anthropogenic Aerosol Forcing, U. A. Jongebloed, A. J. Schauer, J. Cole-Dai, C. G. Larrick, R. Wood, T. P. Fischer, S. A. Carn, S. Salimi, S. R. Edouard, S. Zhai, L. Geng, B. Alexander

Michigan Tech Publications, Part 1

The Arctic is warming at almost four times the global rate. An estimated sixty percent of greenhouse-gas-induced Arctic warming has been offset by anthropogenic aerosols, but the contribution of aerosols to radiative forcing (RF) represents the largest uncertainty in estimating total RF, largely due to unknown preindustrial aerosol abundance. Here, sulfur isotope measurements in a Greenland ice core show that passive volcanic degassing contributes up to 66 ± 10% of preindustrial ice core sulfate in years without major eruptions. A state-of-the-art model indicates passive volcanic sulfur emissions influencing the Arctic are underestimated by up to a factor of three, possibly …


Measurement Of Volumetric Deformation, Strain Localization, And Shear Band Characterization During Triaxial Testing Using A Photogrammetry-Based Method, Sara Fayek, Xiong Zhang, Xiaolong Xia, Qingqing Fu, Jeffrey D. Cawlfield 2023 Missouri University of Science and Technology

Measurement Of Volumetric Deformation, Strain Localization, And Shear Band Characterization During Triaxial Testing Using A Photogrammetry-Based Method, Sara Fayek, Xiong Zhang, Xiaolong Xia, Qingqing Fu, Jeffrey D. Cawlfield

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

Triaxial Testing Has Been Routinely Used as a Standard Laboratory Test that Allows Correct Determination of Soil Characteristics. Previously the Volumetric Strain of the Triaxial Specimen Was Considered to Be Uniformly Distributed Along with the Specimen during the Isotropic and Deviatoric Loading. Although This Assumption Might Hold True under Isotropic Loading, the Effects of Restrained Ends and Disturbance during the Procedures of Specimen Installation and Testing Can Cause Nonuniform Strains throughout the Whole Specimen. This Paper Investigates the Effects of Specimen Preparation and Misalignment on the Strain Uniformity Along with the Soil Specimen during Triaxial Testing. a Series of Consolidated …


Point Density For Soil Specimen Volume Measurements In Image-Based Methods During Triaxial Testing, Sara Fayek, Xiong Zhang, Javad Galinmoghadam, Jeffrey D. Cawlfield 2023 Missouri University of Science and Technology

Point Density For Soil Specimen Volume Measurements In Image-Based Methods During Triaxial Testing, Sara Fayek, Xiong Zhang, Javad Galinmoghadam, Jeffrey D. Cawlfield

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

Discrete Measurement Targets Were Frequently Utilized in Image-Based Methods on the Specimen's Surface to Monitor the Soil Specimen during Triaxial Testing. However, the Required Density of Measurement Targets that Should Be Used in Triaxial Testing to Achieve Highly Accurate Volume Measurement Has Not Been Investigated. to overcome This Limitation, This Paper Presents a Parametric Study to Determine the Optimum Target/point Densities to Be Utilized on the Triaxial Soil Specimen Surface to Achieve the Desired Level of Volume Measurement Accuracy in Image-Based Methods. LiDAR Scanning Was Applied to Establish the "Ground Truth" Volume of the Specimen. the Effects of Deformation and …


Evaluating Geomechanical Uncertainty In Open Pit Mine Planning, Evan Ricchio-Hitchcock 2023 Michigan Technological University

Evaluating Geomechanical Uncertainty In Open Pit Mine Planning, Evan Ricchio-Hitchcock

Dissertations, Master's Theses and Master's Reports

Open pit mine planning encompasses a variety of uncertainties. Uncertainty due to geomechanics is most critical for a safe operation in an open pit mine. Without sufficient knowledge of the geomechanical properties of the subsurface, a reliability analysis of the slope stability could be challenging. Slope stability is a crucial step in pit optimization since the cash flow analysis of a mine is constrained by a stable slope angle. However, obtaining a stable slope angle with certainty is difficult to achieve as geomechanical parameters are modeled using a very limited number of samples. This thesis proposes a method to integrate …


Experimental Study: Investigating The Anions And Cations' Effects On The Elasticity Of The Anionic And Cationic High Viscosity Friction Reducers, Xiaojing Ge, Ghith Biheri, Abdulmohsin Imqam, Baojun Bai, Yuwei Zhang 2023 Missouri University of Science and Technology

Experimental Study: Investigating The Anions And Cations' Effects On The Elasticity Of The Anionic And Cationic High Viscosity Friction Reducers, Xiaojing Ge, Ghith Biheri, Abdulmohsin Imqam, Baojun Bai, Yuwei Zhang

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

High viscosity friction reducers (HVFRs) are widely used as friction-reducing agents and proppant carriers during hydraulic fracturing. The reuse of produced water has gained popularity due to environmental and economic benefits. Currently, the field's most commonly used friction reducers are anionic and cationic HVFRs. Anionic HVFRs are typically pumped with freshwater, while cationic HVFRs are used with high Total Dissolved Solids (TDS) produced water. Cationic friction reducers are believed to have better TDS tolerance, friction reduction performance, and proppant transport capabilities compared to anionic friction reducers under high TDS conditions due to their superior viscoelastic properties. In addition, the impact …


Finite Line Relief Well System Design For Dams And Levees, Andrew M. Keffer, Erich D. Guy, Katherine R. Grote 2023 Missouri University of Science and Technology

Finite Line Relief Well System Design For Dams And Levees, Andrew M. Keffer, Erich D. Guy, Katherine R. Grote

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

An Analytical Method is Commonly Used to Design Relief Well Systems by Assuming the Well Line Extends an Infinite Distance Parallel to the Dam or Levee. This Assumption May Be Met in Some Cases, But When a Well Line is of Finite Length, This Can Severely Underestimate Excess Heads. Although These Consequences Have Been Historically Recognized, a Practical Graph-Based Analytical Approach for Finite Well Line Design Has Not Been Developed. Finite Well Lines Exist and Continue to Be Installed at Many Locations, So This Study Developed a Practical Design Method for Such Systems. Analytical Solutions and Numerical Models Were Used …


The Taphonomic Character, Occurrence, And Persistence Of Upper Permian–Lower Triassic Plant Assemblages In The Mid-Paleolatitudes, Bogda Mountains, Western China, Robert A. Gastaldo, Mingli Wan, Wan Yang 2023 Missouri University of Science and Technology

The Taphonomic Character, Occurrence, And Persistence Of Upper Permian–Lower Triassic Plant Assemblages In The Mid-Paleolatitudes, Bogda Mountains, Western China, Robert A. Gastaldo, Mingli Wan, Wan Yang

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

The Bogda Mountains, Xianjiang Uygur Autonomous Region, Western China, Expose an Uppermost Permian–Lower Triassic Succession of Fully Continental Strata Deposited Across Three Graben (Half Graben) Structures in the Mid-Paleolatitudes of Pangea. a Cyclostratigraphy Scheme Developed for the Succession is Subdivided into Three Low-Order Cycles (Wutonggou, Jiucaiyuan, Shaofanggou). Low-Order Cycles Are Partitioned into 1838 High-Order Cycles based on Repetitive Environmental Changes, and their Plant Taphonomic Character is Assessed in . 4700 M of High-Resolution, Measured Sections Distributed Across ~ 100 Km. Four Taphonomic Assemblages Are Represented By: Permineralized Wood (Both Autochthonous and Allochthonous), Megafloral Adpressions (?parautochthonous and Allochthonous) Identifiable to Systematic …


Magnetic Inversion Approach For Modeling Data Acquired Across Faults: Various Environmental Cases Studies, Khalid S. Essa, Eid R. Abo-Ezz, Neil Lennart Anderson, Omar A. Gomaa, Mahmoud Elhussein 2023 Missouri University of Science and Technology

Magnetic Inversion Approach For Modeling Data Acquired Across Faults: Various Environmental Cases Studies, Khalid S. Essa, Eid R. Abo-Ezz, Neil Lennart Anderson, Omar A. Gomaa, Mahmoud Elhussein

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

An effective extension to the particle swarm optimizer scheme has been developed to visualize and modelize robustly magnetic data acquired across vertical or dipping faults. This method can be applied to magnetic data sets that support various investigations, including mining, fault hazards assessment, and hydrocarbon exploration. The inversion algorithm is established depending on the second horizontal derivative technique and the particle swarm optimizer algorithm and was utilized for multi-source models. Herein, the inversion method is applied to three synthetic models (a dipping fault model contaminated without and with different Gaussian noises levels, a dipping fault model affected by regional anomaly, …


The Influence Of Tropical Atlantic Sea-Surface Temperatures And The North Atlantic Subtropical High During The Maya Droughts, Derek K. Gibson, Jonathan Obrist-Farner, Brooke A. Birkett, Jason H. Curtis, Melissa A. Berke, Peter M.J. Douglas, Prudence M. Rice, Jeremy Maurer 2023 Missouri University of Science and Technology

The Influence Of Tropical Atlantic Sea-Surface Temperatures And The North Atlantic Subtropical High During The Maya Droughts, Derek K. Gibson, Jonathan Obrist-Farner, Brooke A. Birkett, Jason H. Curtis, Melissa A. Berke, Peter M.J. Douglas, Prudence M. Rice, Jeremy Maurer

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

The frequency and duration of Late-Holocene hydrologic extremes in northern Guatemala were investigated using multiple sedimentological and geochemical proxies preserved in a sediment core collected from Lake Petén Itzá. A general trend of increasing aridity in the Maya Lowlands during the past 2000 years was punctuated by several multidecadal- to centennial-scale drought events recorded in the Petén Itzá sediments. In particular, the period spanning the Maya Terminal Classic Period and the Medieval Climate Anomaly (MCA), between 800 and 1300 CE, was marked by several extreme droughts and included the driest conditions of the past 2000 years between 950 and 1100 …


Tropospheric Correction For Insar Using Machine Learning, Ngo Hi Kenny Yue 2023 Missouri University of Science and Technology

Tropospheric Correction For Insar Using Machine Learning, Ngo Hi Kenny Yue

Masters Theses

"Interferometric Synthetic Aperture Radar (InSAR) is a popular technique for studying Earth's surface deformation caused by phenomena like earthquakes and subsidence. However, its accuracy is limited by tropospheric delays caused by water vapor in the atmosphere. This limitation can be overcome by using methods that correct for tropospheric noise, such as statistical, empirical, and predictive approaches. This study explores the potential of using machine learning algorithms to predict the zenith total delay caused by tropospheric effects in InSAR measurements. The study employs two different machine learning algorithms, random forest and neural networks, to learn the relationship between numerical weather prediction …


Drainage And Sedimentary Response Of The Northern Andes And The Pebas System To Miocene Strike-Slip Tectonics: A Source To Sink Study Of The Magdalena Basin, S. Zapata, L. Calderon-Diaz, C. Jaramillo, Francisca Oboh-Ikuenobe, J. C. Piedrahita, M. Rodríguez-Cuevas, A. Cardona, E. R. Sobel, M. Parra, V. Valencia, A. Patiño, J. S. Jaramillo-Rios, M. Flores, J. Glodny 2023 Missouri University of Science and Technology

Drainage And Sedimentary Response Of The Northern Andes And The Pebas System To Miocene Strike-Slip Tectonics: A Source To Sink Study Of The Magdalena Basin, S. Zapata, L. Calderon-Diaz, C. Jaramillo, Francisca Oboh-Ikuenobe, J. C. Piedrahita, M. Rodríguez-Cuevas, A. Cardona, E. R. Sobel, M. Parra, V. Valencia, A. Patiño, J. S. Jaramillo-Rios, M. Flores, J. Glodny

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Miocene strike-slip tectonics was responsible for creating and closing short-lived (ca. 6 Ma) passages and the emergence of isolated topography in the Northern Andes. These geological events likely influenced the migration and/or isolation of biological populations. To better understand the paleogeography of the Miocene hinterland and foreland regions in the Northern Andes, we conducted a source-to-sink approach in the Magdalena Basin. This basin is located between the Central and Eastern Cordilleras of Colombia and contains an ample Miocene record, which includes Lower Miocene fine-grained strata and Middle Miocene to Pliocene coarsening-up strata. Our study presents a new data set that …


Descriptive Systematics Of Upper Palaeocene–Lower Eocene Pollen And Spores From The Northern Niger Delta, South-Eastern Nigeria, Luke Mander, Carlos Jaramillo, Francisca Oboh-Ikuenobe 2023 Missouri University of Science and Technology

Descriptive Systematics Of Upper Palaeocene–Lower Eocene Pollen And Spores From The Northern Niger Delta, South-Eastern Nigeria, Luke Mander, Carlos Jaramillo, Francisca Oboh-Ikuenobe

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Fossil pollen and spores are a vital source of information on the geological history of tropical vegetation including reconstructions of vegetation diversity and composition. However, such work relies on a sound taxonomic framework, and this is challenging to achieve because of the large number of pollen and spore morphotypes that are encountered in palynological preparations from tropical sediments. In tropical West Africa, for example, extensive taxonomic work on Cretaceous–Paleogene pollen and spores was undertaken in the later part of the twentieth century, but more recent palynological work has focused on stratigraphy and basin evolution, and there is a need for …


Sedimentological And Geochemical Characterization Of A Varved Sediment Record From The Northern Neotropics, Edward Duarte, Jonathan Obrist-Farner, Susan R.H. Zimmerman, Erik T. Brown, Robert Brown 2023 Missouri University of Science and Technology

Sedimentological And Geochemical Characterization Of A Varved Sediment Record From The Northern Neotropics, Edward Duarte, Jonathan Obrist-Farner, Susan R.H. Zimmerman, Erik T. Brown, Robert Brown

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Annually resolved sedimentological records (including annual varves) can be used to develop precise chronologies for key climatic and tectonic events. Varved records, however, are most common in high latitude lakes, resulting in a spatial bias with respect to annually resolved records in tropical regions. Here we report on the sedimentology of two sediment cores from Lake Izabal, eastern Guatemala, that contain a well-preserved thinly laminated section spanning ca. 2200 years of the mid-Holocene. We integrate radiocarbon age-depth modeling, sedimentological observations, laminae counting, µX-ray fluorescence scanning, and multivariate statistical analyses to constrain the nature and chronology of the laminations. Our sedimentological …


Microcrystalline Dolomite In A Middle Permian Volcanic Lake: Insights On Primary Dolomite Formation In A Non-Evaporitic Environment, Xin Jiao, Yi Qun Liu, Wan Yang, Hong Li, Zi Yuan Meng, Min Ru Zhao, Zhe Xuan Li 2023 Missouri University of Science and Technology

Microcrystalline Dolomite In A Middle Permian Volcanic Lake: Insights On Primary Dolomite Formation In A Non-Evaporitic Environment, Xin Jiao, Yi Qun Liu, Wan Yang, Hong Li, Zi Yuan Meng, Min Ru Zhao, Zhe Xuan Li

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Lacustrine dolomite nucleation commonly occurs in modern and Neogene evaporitic alkaline lakes. As a result, ancient lacustrine microcrystalline dolomite has been conventionally interpreted to be formed in evaporitic environments. This study, however, suggests a non-evaporitic origin of dolomite precipitated in a volcanic–hydrothermal lake, where hydrothermal and volcanic processes interacted. The dolomite occurs in lacustrine fine-grained sedimentary rocks in the middle Permian Lucaogou Formation in the Santanghu intracontinental rift basin, north-west China. Dolostones are composed mainly of nano-sized to micron-sized dolomite with a euhedral to subhedral shape and a low degree of cation ordering, and are interlaminated and intercalated with tuffaceous …


Digital Commons powered by bepress