Reagent injections designed to provide in stiu mass destruction of soil and groundwater contaminants are commonly prone to failure due to inadequate distribution of the injected reagent. Reagent injections, in particular in situ chemical oxidation (ISCO) injections, require contact between the treatment reagent and targeted contaminant to allow for mass destruction in source zones and plumes. Subsurface heterogeneities that exist at all spatial scales prevent remediation specialists from accurate prediction of reagent distribution in the subsurface, even when significant site characterization and hydraulic testing has previously taken place. A prototype probe system was developed to provide real-time monitoring of the distribution of injected reagents. This thesis focused on laboratory testing of the system to verify that the design was capable of indicating the presence of an injected reagent in the field. Temperature and two-wire dipole resistance sensors were developed with low-cost materials to provide feedback on the electrical conductivity (EC) signatures produced by typical reagents mixed as salt solutions. Sensors were attached to sections of PVC conduit and wired to a data acquisition system to control measurements and store data. The temperature sensor was found to accurately respond to temperature changes in comparison to a commercial datalogger. Measured temperature differences between the constructed sensor and commercial datalogger were relatively constant, indicating that the constructed sensor could be calibrated to measurements from a commercial logger. Static cell experiments were conducted in beakers with varying concentration sodium chloride (NaCl), potassium permanganate (KMnO4) and sodium persulfate (Na2S2O8) solutions to determine dipole resistance sensor response to variations in EC. Different fixed resistors were wired with the dipole sensor circuit to determine the impact on sensor readings. Results indicated a nonlinear correlation between two-wire dipole resistance sensor response and increasing EC. Each constructed dipole sensor behaved uniquely. Raw sensor response was calibrated to EC by accounting for the influence of the fixed resistor. Data was fit to a second-order polynomial with form y = aEC2 + bEC + c, with r2 ranging from 0.92-1.00 for experiments with 4-6 measurement points. Calibrations were accurate within the range of EC for each static cell experiment; trends extrapolated beyond the measurement range were subject to significant error. The choice of fixed resistor did not appear to alter the accuracy of probe calibrations. Flow cell experiments were designed to analyze dipole resistance sensor response to continuous changes in EC. EC breakthrough curves (BTCs) were produced by injecting NaCl tracer solutions into the flow cell. Initial flow cell experiments conducted in an open water system showed agreement between dipole sensor measurement and handheld EC measurements on the rising limb of BTCs and divergence between the two datasets on the falling limb of BTCs. To resolve these issues, a more sophisticated tank with a porous medium was built and tested to compare sensor response from s prototype probe and a commercial EC datalogger. EC BTCs were measured under two scenarios: (1) conditions with deionized water (DI) circulating through the tank as the background solution, and (2) conditions with a simulated groundwater solution with elevated EC circulating through the tank as the background solution. BTCs produced agreement between EC recorded by the commercial logger and dipole resistance measurements for both the rising and falling limbs of BTCs. Results indicated the dipole resistance sensor was not capable of resolving fine changes in EC that occurred during breakthrough. A calibration of all in situ measurements from the experiments with porous medium confirmed the simulated groundwater experiments were subject to significantly less variability than the deionized water experiments. The calibration applied to the simulated groundwater measurements produced BTCs that matched very closely with those recorded by the commercial logger. Two field trials were also conducted during ISCO injections at contaminated sites where probes were installed in existing monitoring wells. The field trials did not successfully correlate dipole resistance sensor measurements with oxidant concentration. Observations from the second trial indicated the dipole sensor measurements correlated with EC of water samples. This work has provided a theoretical representation of two-wire dipole resistance sensor response to EC and has verified expected results through laboratory experiments. It has analyzed the influence of temperature and choice of fixed resistors on two-wire dipole resistance sensor readings, has extensively tested sensor response to EC during static cell and BTC experiments, and has displayed the prototype probe is capable of indicating the presence of injected reagents that have an EC signature. Further research avenues include pilot-scale testing in the field and developing a design for use with a direct-push rig.

Reagent injections designed to provide in stiu mass destruction of soil and groundwater contaminants are commonly prone to failure due to inadequate distribution of the injected reagent. Reagent injections, in particular in situ chemical oxidation (ISCO) injections, require contact between the treatment reagent and targeted contaminant to allow for mass destruction in source zones and plumes. Subsurface heterogeneities that exist at all spatial scales prevent remediation specialists from accurate prediction of reagent distribution in the subsurface, even when significant site characterization and hydraulic testing has previously taken place. A prototype probe system was developed to provide real-time monitoring of the distribution of injected reagents. This thesis focused on laboratory testing of the system to verify that the design was capable of indicating the presence of an injected reagent in the field. Temperature and two-wire dipole resistance sensors were developed with low-cost materials to provide feedback on the electrical conductivity (EC) signatures produced by typical reagents mixed as salt solutions. Sensors were attached to sections of PVC conduit and wired to a data acquisition system to control measurements and store data. The temperature sensor was found to accurately respond to temperature changes in comparison to a commercial datalogger. Measured temperature differences between the constructed sensor and commercial datalogger were relatively constant, indicating that the constructed sensor could be calibrated to measurements from a commercial logger. Static cell experiments were conducted in beakers with varying concentration sodium chloride (NaCl), potassium permanganate (KMnO4) and sodium persulfate (Na2S2O8) solutions to determine dipole resistance sensor response to variations in EC. Different fixed resistors were wired with the dipole sensor circuit to determine the impact on sensor readings. Results indicated a nonlinear correlation between two-wire dipole resistance sensor response and increasing EC. Each constructed dipole sensor behaved uniquely. Raw sensor response was calibrated to EC by accounting for the influence of the fixed resistor. Data was fit to a second-order polynomial with form y = aEC2 + bEC + c, with r2 ranging from 0.92-1.00 for experiments with 4-6 measurement points. Calibrations were accurate within the range of EC for each static cell experiment; trends extrapolated beyond the measurement range were subject to significant error. The choice of fixed resistor did not appear to alter the accuracy of probe calibrations. Flow cell experiments were designed to analyze dipole resistance sensor response to continuous changes in EC. EC breakthrough curves (BTCs) were produced by injecting NaCl tracer solutions into the flow cell. Initial flow cell experiments conducted in an open water system showed agreement between dipole sensor measurement and handheld EC measurements on the rising limb of BTCs and divergence between the two datasets on the falling limb of BTCs. To resolve these issues, a more sophisticated tank with a porous medium was built and tested to compare sensor response from s prototype probe and a commercial EC datalogger. EC BTCs were measured under two scenarios: (1) conditions with deionized water (DI) circulating through the tank as the background solution, and (2) conditions with a simulated groundwater solution with elevated EC circulating through the tank as the background solution. BTCs produced agreement between EC recorded by the commercial logger and dipole resistance measurements for both the rising and falling limbs of BTCs. Results indicated the dipole resistance sensor was not capable of resolving fine changes in EC that occurred during breakthrough. A calibration of all in situ measurements from the experiments with porous medium confirmed the simulated groundwater experiments were subject to significantly less variability than the deionized water experiments. The calibration applied to the simulated groundwater measurements produced BTCs that matched very closely with those recorded by the commercial logger. Two field trials were also conducted during ISCO injections at contaminated sites where probes were installed in existing monitoring wells. The field trials did not successfully correlate dipole resistance sensor measurements with oxidant concentration. Observations from the second trial indicated the dipole sensor measurements correlated with EC of water samples. This work has provided a theoretical representation of two-wire dipole resistance sensor response to EC and has verified expected results through laboratory experiments. It has analyzed the influence of temperature and choice of fixed resistors on two-wire dipole resistance sensor readings, has extensively tested sensor response to EC during static cell and BTC experiments, and has displayed the prototype probe is capable of indicating the presence of injected reagents that have an EC signature. Further research avenues include pilot-scale testing in the field and developing a design for use with a direct-push rig.

Este trabalho tem como objetivo estudar filmes finos de polímeros semicondutores preparados a partir de dispersões coloidais de poli(3,4 etilenodioxitiofeno)/poli(estirenosulfonato de sódio) (PEDOT:PSS), submetidos a tratamentos físico-químicos para alterar as suas características morfológicas e estruturais, melhorando a condutividade elétrica e mantendo um bom nível de transmitância óptica na faixa de comprimento de onda da luz visível. Foram utilizadas no estudo duas dispersões coloidais comerciais de PEDOT:PSS, identificadas como P1 e P2. O P1 descrito pelo fornecedor como de grau condutivo (1 S.cm-1) e P2 de grau altamente condutivo (<100 ?/?). Foram produzidos filmes finos em três procedimentos diferentes e realizadas medidas de resistência elétrica e transmitância óptica. Na primeira série, os filmes foram preparados por spin-coating da dispersão coloidal original de PEDOT:PSS e seguidos pelo recozimento na estufa. Na segunda série, foi adicionado à dispersão coloidal original de PEDOT:PSS um solvente orgânico polar, o dimetilsulfóxido (DMSO), após a centrifugação, a dispersão sobrenadante foi depositada para a preparação de filmes finos como descrito na etapa anterior. Na terceira série, à parte sobrenadante da dispersão coloidal de PEDOT:PSS preparada na segunda série, foi adicionada uma solução precursora de nanopartículas de prata (Tinta Reativa de Prata) (TRP2) e a dispersão coloidal foi depositada para formar filmes finos como descrito anteriormente. As resistividades elétricas com os valores mais significativos foram de filmes de P1 e de P2 depositados a 2000 rpm. Para P1 foram observadas resistividades de 1,37 ?.cm, 0,34 ?.cm e 0,18 ?.cm, para as dispersões coloidais P1 original, P1 tratado com DMSO e P1 tratado com DMSO/TRP2, respectivamente, correspondendo a uma redução de 87% do valor da resistência elétrica da primeira para a terceira série. A transmitância óptica dos filmes a 550 nm se manteve entre 80~90% para todas as séries, nas análises por espectroscopia no UV-Vis. Para os filmes de P2, depositadas a 2000 rpm, as resistividades elétricas nos filmes foram de 0,76 ?.cm, 0,015 ?.cm e 0,0012 ?.cm, para P2 original, P2 tratado com DMSO e P2 tratado com DMSO/TRP2, respectivamente, correspondendo a uma redução de 99,8% do valor da resistência elétrica da primeira para a terceira série. O valor da transmitância óptica dos filmes a 550 nm manteve-se entre 85~90% na primeira e segunda série, entretanto para os filmes da terceira série, devido à presença da fase prata grosseira, reduziu-se para o intervalo entre 40~60%. / This work aims to study thin films of semiconducting polymers prepared from colloidal dispersions of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT: PSS), submitted to physicochemical treatments in order to change their microstructural features and improve their electrical conductivity, while maintaining a good level of optical transmittance in the visible wavelength range. Two types of commercial colloidal dispersions of PEDOT:PSS were used in the study, named as P1 and P2. The P1 is described as a conductive grade (250 ?/?) and P2, highly conductive grade (<100 ?/?). Thin films were produced from colloidal dispersions through three different procedures and their electrical resistance and optical transmittance were measured. In the first series, films were prepared by spin-coating of the PEDOT: PSS pristine colloidal dispersion, followed by annealing in the oven. In the second series, to the pristine colloidal dispersion of PEDOT:PSS a polar organic solvent dimethylsulfoxide (DMSO) was added, then after centrifugation, the supernatant colloidal dispersion was deposited to form thin films as described previously. In the third series, to the supernatant colloidal dispersion of PEDOT:PSS prepared in the second series, a silver nanoparticle precursor solution (Reactive Silver Ink) (TRP2) was added and the colloidal dispersion was deposited to form thin films as described previously. Electrical resistivity with the most significant values from P1 and P2 films deposited at 2000 rpm. For the films from P1, 1.37 ?.cm, 0.34 ?.cm and 0.18 ?.cm were observed, for pristine colloidal dispersion, with DMSO and with DMSO and TRP2, respectively; corresponding to a reduction of 87% of the electrical resistance from the first to the third series. The optical transmittance of films at 550 nm, as measured by UV-Vis spectroscopy, was maintained in the range 80~90% for all series. For the films from P2, the electrical resistances were observed to vary from 0.76 ?.cm to 0.015 ?.cm and 0.0012 ?.cm, for pristine P2 colloidal dispersion, after DMSO addition and with DMSO and TRP2, respectively, corresponding to a reduction of 99.8% in the electrical resistance from the first series to the third one. The optical transmittance of films at 550 nm was observed to remain in the range 85~90% for the first and second series, while the third series, due to the massive presence of a coarse silver phase, dropped to the range 40~60%.

Variations in drainage density have been observed in a range of environments as the perennial stream network expands into headwater reaches. This network expansion and contraction results in large changes in drainage density and as such, has implications for the connectivity of the catchment and the associated flux of water, sediments and solutes. One environment where these changes have been observed is peatlands. The accurate characterisation of catchment connectivity in peatlands is desirable for a number of reasons, not least to understand the controls on carbon flux. In addition, the accurate characterisation of these systems will help us to predict the impacts of a changing climate. It is hitherto been difficult to quantify changes in connectivity due to the logistical difficulties of monitoring this phenomenon. The use of Electrical Resistance (ER) technology has shown potential to detect the presence and absence of water. This method is built on here and a range of sensors are developed to monitor connectivity at high temporal and spatial resolutions, specifically flow in ephemeral portions of the channel network, pipeflow and overland flow. The study takes places in the Upper North Grain research catchment, a small peatland headwater catchment in the south Pennines, UK. The data collected on ephemeral streamflows highlight the importance of water table as a control on changes in network extent in the study catchment, as the presence or absence of flow at each site is strongly controlled by local water table. This allows the minimum and maximum drainage density within the catchment to be determined, as well how frequently these states occur. Pipe stormflow generation appears to be strongly linked to the production of saturation excess overland flow. The pipe network is very sensitive to small inputs of rainfall. In contrast, pipe baseflows seem to be controlled by water table level as pipes are fed by seepage from the peat mass. Pipe behaviour could not be related to any of the morphological characteristics presented here and is though to be dependent on the subsurface morphology of the pipe network. Overland flow production was monitored at a gully head and gully side location. At the gully head the incidence of overland flow increased with distance from the gully edge due to higher local water tables encouraging the production of saturation excess overland flow. At the gully side, extreme water table drawdown has caused the peat to become hydrophobic and the incidence of overland flow is high here, due to infiltration excess. This signifies a major advancement in our knowledge of runoff pathways in peatlands as the importance of infiltration excess overland flow has not been acknowledged until now. In general, ephemeral streamflows occur before the production of either overland flow or pipeflow as incident rainfall causes saturation of the gully floors. The temporal pattern of overland flow and pipeflow is similar, although pipeflow continues after overland flow ceases and is thought to be fed by shallow subsurface flow on the recession limb. Both overland flow and pipeflow precede discharge at the catchment outlet by several minutes. The interaction of these processes is examined under both ‘wet’ and ‘dry’ antecedent conditions. The data collected here provide an accurate characterisation of the dynamics of, and controls on, peatland connectivity under current climatic conditions, providing a reference point to which future observations can be compared.

The aim of this research is to explore the integration of ad hoc and mobile sensors into a conventional Electrical Resistance Tomography (ERT) system. This is motivated by the desire to improve the spatial resolution of 3D reconstructed images that are produced using ERT. The feasibility of two approaches, referred to as the Extended Electrical Tomography (EET) and Augmented Electrical Tomography (AET) are considered. The approaches are characterized according to the functionality of the sensors on the ad hoc 'pills'. This thesis utilizes spectral and numerical analysis techniques, with the goal of providing a better understanding of reconstruction limitations, including quality of measurements, sensitivity levels and spatial resolution. These techniques are applied such that an objective evaluation can be made, without having to depend heavily on visual inspection of a selection of reconstructed images when evaluating the performance of different set-ups. In EET, the sensors on the pills are used as part of the ERT electrode system. Localized voltage differences are measured on a pair of electrodes that are located on an ad hoc pill. This extends the number of measurements per data set and provides information that was previously unobtainable using conventional electrode arrangements. A standalone voltage measurement system is used to acquire measurements that are taken using the internal electrodes. The system mimics the situation that is envisaged for a wireless pill, specifically that it has a floating ground and is battery-powered. For the present exploratory purposes, the electronic hardware is located remotely and the measured signal is transmitted to the PC through a cable. The instrumentation and data acquisition circuits are separated through opto-isolators which essentially isolates both systems. Using a single pill located in the centre of a vessel furnished with 16 electrodes arranged in a single plane, spectral analysis indicates that 15 of the 16 extended measurements acquired using the adjacent current injection strategy are unique. Improvement is observed for both the sensitivity and spatial resolution for the voxels in the vicinity of the ad hoc pill when comparing the EET approach with the conventional ERT approach. This shows the benefit of the EET approach. However, visual inspection of reconstructed images reveals no apparent difference between images produced using a regular and extended dataset. Similar studies are conducted for cases considering the opposite strategy, different position and orientation of the pill, and the effect of using multiple pills. In AET, the sensors on the ad hoc pills are used as conductivity probes. Localized conductivity measurements provide conductivity values of the voxels in a discretized mesh of the vessel, which reduces the number of unknowns to be solved during reconstruction. The measurements are incorporated into the inverse solver as prior information. The Gauss-Newton algorithm is chosen for implementation of this approach because of its non-linear nature. Little improvement is seen with the inclusion of one localized conductivity measurement. The effect on the neighbouring voxels is insignificant and there is a lack of control over how the augmented measurement influences the solution of its neighbouring voxels. This is the first time that measurements using ad hoc and 'wireless' sensors within the region of interest have been incorporated into an electrical tomography system.

Photovoltaic(PV) technology is promising due to its natural availability among energy harvesting technologies. There is a growing need for sustainable power sources that can function without being connected to a power source or needing regular battery replacements. Wearable PV cells are gaining popularity in different applications. However, most companies produce wearable PVs for terrestrial applications. Research on wearable PV applications for the marine environment remains limited because these cells suffer from several issues. This research compares commercially sourced wearable PV cells' maximum current consistency and electrical resistance for two testing conditions. The researcher followed standardized methods for these two laundering and corrosion testing conditions. The results revealed that current consistency values decreased over both types' laundering and corrosion testing conditions. However, electrical resistance values showed opposite trends. The findings of this study suggest that wearable PV cells may serve as a reliable source for powering electronic devices in marine environments.

No description available.

No description available.

Mobile platforms for archaeological purposes have increased in use over the last 20 years with many of the developments coming from Continental Europe. Mobile platform developments have mainly focused on one type of instrumentation, offering multiple sensors, depths of detection or frequencies. This development of mobile platforms has focused on data acquisition rates but has not considered the physical impact on the soil. The Geoscan Research Mobile Sensor Platform (MSP40) was intended to improve survey efficiency and remain a lightweight system. The platform can collect two earth resistance configurations that show directional variation of the current flow through soil. Additional sensors were integrated on to the square frame of the hand-pulled cart to record simultaneous fluxgate gradiometer data and a microtopographic surveys. Ground based geophysical investigation will always have a physical impact on a site. The MSP40 is no exception but careful selection of wheel types and the lightweight frame limit the damage compared to many mobile arrays. The MSP40 has been tested on a number of different soils at various times of the year with encouraging results; however issues with overcoming the contact resistance of electrodes remain. The continuous collection rate and combination of techniques means a slight drop in data quality is inevitable. However the increased data density, multiple-sensors and improved rate of collection offset reductions in data quality. The research has shown that the MSP40 can perform low impact rapid site assessments on ¿vulnerable¿ sites, whilst maximising the information gained from a single traverse. / AHRC, Geoscan Research

During the incorporation of ceramic particles into metallic alloy melts for the production of metal matrix composites, the particles tend to float or sink, depending on their density. In order to study the sedimentation patterns, a novel electrical resistance technique has been developed. A current is passed between two electrodes, and the potential over a fixed distance is measured with two other electrodes. Experiments were carried out in an aluminum foundry alloy(A356) containing up to 30 volume percent 88 μm silicon carbide particles. The particles’ behaviour was compared with sedimentation patterns in aqueous systems. The implications for fabrication and remelting of metal matrix composite material are discussed. / Thesis / Master of Engineering (ME)