Arvin Farid

Am I a STEM professional? Documenting STEM student professional identity development

Post-secondary education is expected to substantially contribute to the cognitive growth and professional achievement of students studying science, technology, engineering, and mathematics (STEM). Yet, there is limited understanding of how students studying STEM develop a professional identity. We used the lens of self-authorship to develop a model for STEM student professional identity development. We applied the model to frame our assessment of the relationship between the level of STEM students’ perceptions of their professional identities and their educational experiences, learning preferences, and comfort with faculty interactions. We found a misalignment between students’ perception of themselves as professionals and the expectations for their actions in professional situations. We also found that students engaged in learning activities similar to the activities of STEM professionals communicated higher levels of professional identity development. We provide implications for our research and directions for ongoing investigations.

Scale Model Experimental Validation and Calibration of the Half-Space Green's Function Born Approximation Model Applied to Cross-Well Radar Sensing

Efficient forward models that describe the physical nature of the geophysical problem are desired for subsurface sensing and reconstruction of a contrasting contaminant pool volume. An analytical model to approximate sensing with radar is developed and implemented in the frequency domain in terms of the half-space lossy dyadic Greens function. The Born approximation is employed as a linear forward model, which will eventually be used for tomographic inversion for object detection. The forward model is compared with measurements generated by a cross-well radar (CWR) experiment in a controlled soil test tank using broadband borehole antennas. Soil parameter (dielectric constant and loss tangent) variance with frequency is represented by a quadratic polynomial. Calibration for soil parameters is performed via CWR data using an iterative nonlinear parameterized inversion technique. With the appropriate calibration, good agreement is obtained with wideband experimental measurements for several different borehole antenna placements, confirming the accuracy of the model.

Electromagnetic Stimulation of Two-Phase Transport in Water for Geoenvironmental Applications

Air sparging is a popular remediation technology for contaminated soils. However, the application is not efficient due to the limitations of airflow that result from the formation of random preferential air channels. Controlling the formation of these air channels and enhancing diffusion surrounding them can considerably improve the effectiveness of air sparging. This work is a study on how electromagnetic (EM) waves—without a measureable increase in temperature—enhance the transport of a nonreactive dye in water as a visible analogy of air sparging (i.e., airflow within groundwater). This paper explains the details of the experimental setup and procedures required to conduct the EM-stimulation experiment as well as electric-field mapping and digital imaging of dye transport for the purpose of digital visual analysis. Several antenna designs and the way they direct the transport mechanism are studied. The results of EM-stimulation tests with no measureable temperature increase show that EM waves enhance and direct the dye transport in accordance with the EM source (transmitting antenna) and its radiation pattern. The rate of transport of the dye is studied and compared for unstimulated and EM-stimulated tests. Because of the small size of the dye molecules and existence of an alternating electric field, dielectrophoresis is the most likely potential transport mechanism. However, the existence of other competing factors dominating dielectrophoresis interferes with this type of study. Future modifications in the experimental design seem to have the potential to improve the investigation of the transport phenomenon.

Study of Mechanisms Governing Electromagnetic Alteration of Hydraulic Conductivity of Soils

Hydraulic conductivity is a measure of the rate at which water flows through porous media. Because of the dipole properties of water molecules, electric field can affect hydraulic conductivity. In this study, the effect of radio-frequency (RF) waves on hydraulic conductivity is investigated. This is important both for the geophysical measurement of hydraulic conductivity as well as remediation using electromagnetic waves. Bentonite clay and sandy samples are tested in rigid-wall, cylindrical permeameters and stimulated using a CPVC-cased monopole antenna vertically centered in the permeameters. The permeameters are encased within RF cavities constructed of aluminum mesh in order to prevent interference from the outside and to confine the RF wave to the medium. Falling-head and constant-head tests are performed to measure the hydraulic conductivity of the clayey and sandy soil samples, respectively. The results show a correlation between the change in the hydraulic conductivity and various characteristics of the RF stimulation. The change is, however, different for sandy and clayey soils.

Experimental Validation of a Numerical Forward Model for Tunnel Detection Using Cross-Borehole Radar

The goal of this research is to develop an experimentally validated two- dimensional (2D) finite difference frequency domain (FDFD) numerical forward model to study the potential of radar-based tunnel detection. Tunnel detection has become a subject of interest to the nation due to the use of tunnels by illegal immigrants, smugglers, prisoners, assailants, and terrorists. These concerns call for research to nondestructively detect, localize, and monitor tunnels. Nondestructive detection requires robust image reconstruction and inverse models, which in turn need robust forward models. Cross-Well Radar (CWR) modality is used for experimentation to avoid soil-air interface roughness. CWR is not a versatile field technology for political boundaries but is still applicable to monitoring the perimeter of buildings or secure sites. Multiple-depth wideband frequency-response measurements are experimentally collected in fully water-saturated sand, across PVC-cased ferrite-bead-jacketed borehole monopole antennae at a pilot scale facility (referred to as SoilBED). The experimental results are then compared with the 2D-FDFD model. The agreement between the results of the numerical and experimental simulations is then evaluated. Results of this work provide key diagnostic tools that can help to

Cross-Well Radar. I: Experimental Simulation of Cross-Well Tomography and Validation

This paper explains and evaluates the potential and limitations of conducting cross-well radar (CWR) in sandy soils. Implementing the experiment and data collection in the absence of any scattering object, and in the presence of an acrylic plate [a representative of dielectric objects, such as dense nonaqueous phase liquid (DNAPL) pools, etc.], as a contrasting object in a water-saturated soil is also studied. To be able to image the signature of any object, more than one pair of receiving and transmitting antennas are required. The paper describes a method to achieve repeatable, reliable, and reproducible laboratory results for different transmitter-receiver combinations. Different practical methods were evaluated for collecting multiple-depth data. Similarity of the corresponding results and problems involved in each method are studied and presented. The data show that the frequency response of a saturated coarse-grained soil is smooth due to the continuous and dominant nature of water in saturated soils. The repeatability and potential symmetry of patterns across some borehole axes provide a valuable tool for validation of experimental results. The potential asymmetry across other borehole axes is used as a tool to evaluate the strength of the perturbation on the electromagnetic field due to hidden objects and to evaluate the feasibility of detecting dielectric objects (such as DNAPL pools, etc.) using CWR. The experimental simulation of this paper models a real-life problem in a smaller scale, in a controlled laboratory environment, and within homogeneous soils that are uniformly dry or fully water saturated, with a uniform dielectric property contrast between the inclusion and background. The soil in the field will not be as homogeneous and uniform. The scaling process takes into consideration that as the size is scaled down; the frequency needs to be scaled up. It is noteworthy that this scaling process needs to be extensively studied and validated for future extension of the models to real-field applications. For example, to extend the outcome of this work to the real field, the geometry (antenna size, their separation and inclusion size) needs to be scaled up back to the field size, while soil grains will not. Therefore, soil, water, and air coupling effects and interactions observed at the laboratory scale do not scale up in the field, and may have different unforeseen effects that require extensive study.

Electromagnetic Enhancement of Microbially Induced Calcite Precipitation

Uniform distribution of soluble and insoluble materials into saturated porous soil is often challenging for geotechnical applications, due to the random formation of fingers, i.e., a form of instability at the interface of materials with contrasting density and viscosity. A mechanism by which, one could control this random fingering tendency would support a broad array of applications where it is desirable to uniformly penetrate soil with a substance. In our previous research, the use of electromagnetic (EM) waves has been demonstrated to be effective to induce multiphase flow of dense (ρ > 1 g/cm3) materials in aqueous media, as well as to control air-channel formation in air sparging. EM waves with carefully predesigned radiation pattern were shown to induce a directed two-phase flow in aqueous and saturated porous media with relatively low energy input and minimal heat generation. A homogeneous medium of saturated Ottawa sand within a dimensionally scaled cavity (a Plexiglas tank with its walls covered with transparent, electrically conductive films), designed with a reservoir at the bottom plumbed to maintain constant head, was used to simulate the soil medium. Then, a nonaqueous liquid was supplied, an even distribution of which (throughout the soil volume) was desired. In current practice, such an application would have limited success, owing to the aforementioned fingering effects, as well as the relatively slow process of natural dispersion. Such a case is used as the control. In the study case, EM waves were then launched into the cavity using a loop antenna sharing the ground as the cavity at the best impedance-matched frequency. The EM filed was also numerically simulated using COMSOL Multiphysics finite-element analysis software. The model was also experimentally validated using experimental measurement. Observations and measurements of the induced flow are then made to assess the effectiveness of the distribution. Infiltrating materials to be studied include ionic, soluble nonionic, and biological samples, selected based on their value for various geotechnical applications. Subsequent pilot- or field-scale testing is necessary to determine ultimate applicability of the system.

Laboratory Study of Electromagnetically Induced Contaminant Removal

Soil contamination with hazardous substances can be in solid or liquid forms such as petrochemicals or chlorinated solvents hydrocarbons. Contaminants in soil can be physically or chemically adsorbed to soil grains or only trapped in pore space. Soil contamination usually occurs through spillage or burial directly at the contaminated area or migration from a spillage or burial source occurred elsewhere. Some of most occurring sources of soil pollution are petrochemical and chemical contamination. This study investigates the use of electromagnetic (EM) waves with various radiation patterns to induce a controlled transportation of a nonhazardous dye (used as contamination simulant). The medium in this study is aqueous (i.e., water), which helps to monitor the contaminant simulant transport under EM stimulated conditions. EM waves can be launched into the medium at proper frequencies to minimize the heat generation and temperature increase, yet induce a transport according to the EM radiation pattern. Then, the contaminant-simulant transport under EM-stimulated and unstimulated conditions were studied, and the results suggest that dielectrophoresis can be the underlying

Electromagnetically Induced Transport in Water for Geoenvironmental Applications

Air sparging is a popular soil remediation technique that enables the removal of contaminants through diffusing air into soil. The removal process is, however, slow. The goal of this work is to study the effect of electromagnetic (EM) waves —with minimal heat generation— on transport mechanisms such as diffusion, in order to improve airflow or contaminant transport in order to expedite the cleanup process using air sparging or similar technologies. This effect is studied through an experimental setup that examines the diffusion of a nonreactive dye in water under EM waves at a range of frequencies (50-200 MHz). The electric field was simulated using COMSOL Multiphysics for better three-dimensional (3D) visualization and analysis and then validated using the experimental measurements. A dielectrophoretic study was then performed using the simulated electric field. Various dye flows under EM stimulation at different frequencies were compared. At 65 MHz and 76 MHz, the dye flow was in the direction of the dielectrophoretic forces, which are believed to be the governing mechanism for the EM-stimulated dye transport.

Laboratory Study of the Effect of Electromagnetic Waves on Airflow during Air Sparging

Air sparging is a popular remediation technology used for treating soil and groundwater contaminated with volatile organic compounds (VOCs). Little is known about the system variables and mass-transfer mechanisms in the air-sparging process. The VOC removal process during air sparging is very slow and time consuming (it might take months or years). The hypothesis of this work is that electromagnetic (EM) waves can be used to enhance air sparging with minimal heat generation. The goal of this research is to study the effect of EM waves on air-channel formation and air diffusion between air channels within soil. This should ultimately help to create a technology to improve airflow and expedite the cleanup process using air sparing. This research presents the theoretical and experimental study to investigate the injected airflow pattern within a glass-bead medium used as an analogous medium to soil. The full three-dimensional (3D) vector electric field was needed for this study. Therefore, experimental measurements of the electric-field component of EM waves were performed, and the results were used to validate a numerical (finite element) simulation using COMSOL Multiphysics software. Air-sparging experiments were also performed at different injected air pressures, and digital images of the airflow patterns were collected. The size and shape of the zone of influence (ZOI) of airflow were measured. Airflow patterns were monitored for the unstimulated case as well as cases stimulated at various EM power levels and frequencies. The airflow was also modeled using a finite-difference method. A coupled analysis of airflow and EM-wave propagation was used to evaluate the correlation between EM-wave characteristics and air sparging.