Change In Electrical Resistance Research Articles

Detecting soil water redistribution in subsurface drip irrigated processing tomatoes using electrical resistivity tomography, proximal sensing and hydrological modelling

In this study, multiple soil-plant-atmosphere continuum (SPAC) monitoring methodologies, including electrical resistivity tomography (ERT), proximal thermal sensing techniques, and micrometeorological data, were combined with two-dimensional (2-D) soil hydrological modelling using HYDRUS 2-D to explore the soil water redistribution, and infer the relative crop water status in a subsurface drip irrigated (SDI) processing tomato field located in California (Yolo County, USA). Specifically, time-lapse ERT surveys were performed at two transects distributed parallel and perpendicular, respectively, to the SDI line, during an irrigation event. The ERT results were compared to HYDRUS 2-D outputs and the relative differences were explained in the form of local heterogeneities in electrical resistivity (ER) changes, as a proxy for soil water content (SWC) variations. Concurrent simultaneous soil wetting and root water uptake during the last irrigation event of the season caused negligible changes in ER in the active root zone. Slight differences in ER were observed in the top 20 cm along the dripline, confirming that the emitter spacing is small enough to create a wetted strip along the processing tomato bed. These changes were also compared to SWC values measured with time domain reflectometry soil moisture sensors. A comparison between HYDRUS 2-D and ERT confirmed negligible changes in ER during irrigation due to simultaneous wetting and root water uptake processes. In addition, a good correlation was observed between the proximal sensed and the ERT results. Finally, the findings of this study underscore the necessity of using multiple methods for improving our knowledge of the SPAC system under real field conditions.

An advanced cement-based geocomposite with autonomous sensing and heating capabilities for enhanced intelligent transportation infrastructure

This study introduces an innovative multifunctional cementitious-based geocomposite with self-sensing and self-heating capability, generated for transportation infrastructural health monitoring and traffic recognition. In this route, hybrid graphene nanoplatelets (GNP) and carbon nanotubes (CNT) were uniformly dispersed within a matrix of stabilized sand containing 10% cement. The mechanical and microstructural performances of the composite were examined using various tests. The self-sensing capabilities of the composite were also investigated. In addition, the effects of temperature, moisture content, and loading shape, speed and magnitudes on the strain and stress sensing capability of the specimens were also investigated. The self-sensing performance of this cementitious geocomposite for the asphalt layer strain detection was assessed in a hybrid section including the asphalt mixture layer and smart geocomposite. Moreover, the research also examined the composite's capacity for self-heating, a highly relevant application within the transportation sector. The 0.98 ˚C/s heating rate, 526 mW/˚C heating power, and 251 ˚C maximum temperature proved the high heating potential of this geocomposite for deicing, self-healing, and temperature sensing applications. The specimens showed a supreme correlation between strain changes and fractional changes in electrical resistance (FCR) values in different loading patterns. Although increasing temperature amplified the piezoresistivity response of the composite, the introduction of humidity had adverse impacts. An appropriate correlation was observed between gauge factor, modulus, and digital image correlation analysis. The piezoresistive response of this geocomposite in the hybrid section including smart geocomposite and asphalt layer, representative of the common structural layers of urban pavements, showed the ability of this geocomposite in terms of strain and stress detection of itself and even in the asphalt layer. This study provides a bright horizon for smart materials development in civil infrastructures, particularly transportation and railways.

A broad-spectrum gas sensor based on correlated two-dimensional electron gas

Designing a broad-spectrum gas sensor capable of identifying gas components in complex environments, such as mixed atmospheres or extreme temperatures, is a significant concern for various technologies, including energy, geological science, and planetary exploration. The main challenge lies in finding materials that exhibit high chemical stability and wide working temperature range. Materials that amplify signals through non-chemical methods could open up new sensing avenues. Here, we present the discovery of a broad-spectrum gas sensor utilizing correlated two-dimensional electron gas at a delta-doped LaAlO3/SrTiO3 interface with LaFeO3. Our study reveals that a back-gating on this two-dimensional electron gas can induce a non-volatile metal to insulator transition, which consequently can activate the two-dimensional electron gas to sensitively and quantitatively probe very broad gas species, no matter whether they are polar, non-polar, or inert gases. Different gas species cause resistance change at their sublimation or boiling temperature and a well-defined phase transition angle can quantitatively determine their partial pressures. Such unique correlated two-dimensional electron gas sensor is not affected by gas mixtures and maintains a wide operating temperature range. Furthermore, its readout is a simple measurement of electric resistance change, thus providing a very low-cost and high-efficient broad-spectrum sensing technique.

The effects of different nano materials on the strain and crack length sensing performance of smart concrete: Phenomenological models

Nineteen concrete mixtures with multi wall carbon nano tube (MWCNT), graphene, nano scale (waste of steel industry, iron oxide) and suspensions of nano sized iron, zinc, and a composite suspension of nano sized iron, silver, copper, zinc were designed with different volume percent. The electrical resistivity decreased 229%, 176%, 113%, 251% with additions of graphene, MWCNT, nano scale, composite suspension of nano-sized iron, silver, copper, zinc, respectively. The compressive strain sensitivity of the mixtures increased 244%, 211%, 311% with addition of graphene, MWCNT, nano zinc suspension, respectively. Tensile strain and crack length sensitivities of reference and graphene added mixtures which had the highest compressive strain sensitivity were determined. Strong linear relationships between compressive strain, tensile strain and crack length versus electrical resistance change were observed. Detailed phenomenological models were presented for relationship between the graphene amount, tensile strain and crack sensitivities.

Anisotropic magneto-resistivity and magnetocaloric effect in DyAl2

In this study, we experimentally and theoretically investigate the correlation between the anisotropic magnetic resistivity and magnetocaloric effect in DyAl2 single crystals. DyAl2 crystallizes in the C15 Laves phase structure with cubic symmetry. While some earlier studies revealed that the isothermal entropy change in dialuminides follows a similar trend as the electrical resistivity change as a function of temperature and magnetic field, the correlation between anisotropic behavior of these two physical parameters is yet to be explored to the best of our knowledge. To address this gap, we measured electrical resistivity of DyAl2 single crystals along two different directions in zero and applied magnetic fields and compared the experimental results with our theoretical model. For the theoretical analysis, we employed a model Hamiltonian in the mean-field approximation, considering the exchange interaction, Zeeman effect, and crystalline electric field associated with the cubic symmetry. Our findings reveal a significant dependence of DyAl2 resistivity on the direction of the applied magnetic field, in agreement with our theoretical results. These outcomes emphasize the interplay between magnetocaloric effect and magneto-resistivity, underscoring the potential of the magnetocaloric effect as a valuable tool for gaining deeper insights into basic physical properties including electron transport behavior.

Nature of anomalous electrical resistance in Co73-xFe4CrxSi12B11 amorphous microwires

Influence of structural relaxation and composition of microwires of metallic amorphous alloys Co73-xFe4CrxSi12B11 (x = 0, 2, 4, 6, 8) on the character and mechanisms of temperature dependence of electrical resistance r(T) has been studied in a wide temperature range (from 4.2 K to crystallization temperature). It is shown that alloys with more than 2 at.% Cr have a number of specific properties, which are significantly differentiate them from Fe- and Ni-rich alloys, as well as many Co-rich amorphous alloys. The features of Cr-doped Co-rich alloys are explained by two reasons: firstly, very strong quantum interference effects of the electron-electron interaction and weak localization of electrons caused by scattering of electrons by the potential created by randomly distributed chromium atoms, and secondly, partially reversible compositional structural relaxation leading to clustering of the amorphous phase at T > 300 °C. It is assumed that the resulting Cr-rich clusters, in which chromium atoms are bonded to metalloid atoms, can enhance these interference effects. The contributions from various mechanisms of interaction and scattering of electrons to the change in electrical resistance with temperature and composition of the alloy are analyzed. The fitting parameters for them are determined and compared with the known data.

Manipulation of fractionalized charge in the metastable topologically entangled state of a doped Wigner crystal

Metastability of many-body quantum states is rare and still poorly understood. An exceptional example is the low-temperature metallic state of the layered dichalcogenide 1T-TaS2 in which electronic order is frozen after external excitation. Here we visualize the microscopic dynamics of injected charges in the metastable state using a multiple-tip scanning tunnelling microscope. We observe non-thermal formation of a metastable network of dislocations interconnected by domain walls, that leads to macroscopic robustness of the state to external thermal perturbations, such as small applied currents. With higher currents, we observe annihilation of dislocations following topological rules, accompanied with a change of macroscopic electrical resistance. Modelling carrier injection into a Wigner crystal reveals the origin of formation of fractionalized, topologically entangled networks, which defines the spatial fabric through which single particle excitations propagate. The possibility of manipulating topological entanglement of such networks suggests the way forward in the search for elusive metastable states in quantum many body systems.

Double percolation phenomenon of carbon nanotube/cement composites as piezoresistivity sensing elements with exposure to salt environment

It has been known that the carbon nanotube (CNT)/cement composites can be used to reflect the external loading information and detect premature damage; however, the agreement on whether the piezoresistivity as a function of external loading is positive or negative has yet to be achieved, and the innate electrically conductive mechanism remains unclear. In this study, to minimize the application cost, small-size CNT/cement composites were embedded into the surface of the concrete as sensing elements, and the piezoresistivity of the CNT/cement composites under external loading along with/without salt attacks was tested. The results indicate that the piezoresistivity significantly depends on the percolation backbone density and the critical exponent of the CNT networks near the percolation threshold. Without salt environments, an “M” shape was observed in the curve of the fractional electrical resistivity (FCR) as a function of cyclic loading applied on the concrete samples. However, when the concrete samples were exposed to a salt environment, the “M” shape in the FCR curve disappeared. In addition, based on the percolation theory, the electrical resistivity changes as a function of strain fits well with an exponential function. The microstructure analysis demonstrates that the pore structure of the CNT/cement composites can be divided into spherical pores and cracks with layered structures. This study not only provides a new insight into the electrical conduction mechanism in CNT/cement composites systems but also sheds light on how to accurately monitor and analyze concrete structures with external loads, especially along with salt environment.

Контроль прочности серого чугуна электрографическим способом

The experimental procedure carried out on a test installation to determine the electrical resistance value in the process of crystallization of cast iron is presented. A scheme of a test installation using a measuring circuit based on the Wheatstone bridge circuit to determine the electrical resistance value of crystallized cast iron is given. Recording measured data over time allowed constructing a graphical dependence of the change in the values of specific electrical resistance during the crystallization of gray cast iron. Experimental data on changes in the values of the specific electrical conductivity of a sample of gray cast iron during crystallization and their relationship to the amount of supercooling of the melt of this alloy are presented. The obtained dependence made it possible to identify on the curve of specific electrical resistivity change under supercooling of cast-iron test sample those areas, which were exposed to the cast-iron melt supercooling. The ratio of the initial and final values of the electrical resistivity under supercooling of cast iron allowed calculating the values of the relative electrical resistivity. Measurements of cast iron strength have shown that they are functionally related to the value of the relative electrical resistivity of gray cast iron, determined by the degree of supercooling of the cast iron melt. The use of this method will make it possible to predict gray cast iron strength and will allow reducing the amount of castings defective in terms of mechanical properties and at the same time increasing foundry production profitability.

Monitoring temperature and hydration by mortar sensors made of nanomodified Portland cement

Mortar beams incorporating carbon nanofibers (CNFs), which were synthesized in situ on Portland cement particles, were used to produce nanomodified Portland cement sensors (SmartCem sensors). SmartCem sensors exhibited an electrical response comparable to a thermistor with a temperature coefficient of resistivity of − 0.0152/ °C. The highest temperature sensing was obtained for the SmartCem sensor, which contained ~ 0.271 wt.% of CNFs. The calculated temperature sensitivity was approximately 11.76% higher in comparison with the mortar beam containing only unmodified Portland cement. SmartCem sensors were used to monitor the cement hydration in large-scale self-compacting concrete beams. The measurements were conducted after casting for 7 days. Additionally, commercially available thermocouple and humidity sensors were used as references. The results showed that changes in electrical resistivity measured by the SmartCem sensor were well aligned with the ongoing hydration processes.

Material-Enabled Impact Detection and Damage Localisation System Using Shape Memory Alloy Tufted Composites

Shape memory alloy (SMA) tufted composites have shown a significant improvement of the mechanical strength, fracture toughness, and delamination resistance of structural joints. This paper investigated the self-sensing functionality of SMA tufted carbon/epoxy composite T-joints to enable in situ strain monitoring for the detection of low-velocity impacts. Indeed, large deformations in the tufted composite due to impacts caused abrupt changes in electrical resistance of SMA filaments, which were used to trigger the detection system. An Arduino Mega controller was programmed to simultaneously extract and process real-time electrical resistance recordings from SMA tufts during impact tests conducted at 5 J and 10 J. Experimental results showed that the proposed SMA-enabled detection system can capture accurately the time of the impact and localise the delamination onset, thus demonstrating the truly multifunctional capabilities of proposed SMA tufted composites.

Imaging of the electrical activity in the root zone under limited-water-availability stress: a laboratory study for Vitis vinifera

Abstract. Understanding root signals and their consequences for the whole plant physiology is one of the keys to tackling the water-saving challenge in agriculture. The implementation of water-saving irrigation strategies, such as the partial root zone drying (PRD) method, is part of a comprehensive approach to enhance water use efficiency. To reach this goal tools are needed for the evaluation of the root's and soil water dynamics in time and space. In controlled laboratory conditions, using a rhizotron built for geoelectrical tomography imaging, we monitored the spatio-temporal changes in soil electrical resistivity (ER) for more than a month corresponding to eight alternating water inputs cycles. Electrical resistivity tomography (ERT) was complemented with electrical current imaging (ECI) using plant-stem-induced electrical stimulation. To estimate soil water content in the rhizotron during the experiment, we incorporated Archie's law as a constitutive model. We demonstrated that under mild water stress conditions, it is practically impossible to spatially distinguish the limited-water-availability effects using ECI. We evidenced that the current source density spatial distribution varied during the course of the experiment with the transpiration demand but without any significant relationship to the soil water content changes. On the other hand, ERT showed spatial patterns associated with irrigation and, to a lesser degree, to RWU (root water uptake) and hydraulic redistribution. The interpretation of the geoelectrical imaging with respect to root activity was strengthened and correlated with indirect observations of the plant transpiration using a weight monitoring lysimeter and direct observation of the plant leaf gas exchanges.

Integrated Bolometric Photodetectors Based on Transparent Conductive Oxides from Near‐ to Mid‐Infrared Wavelengths

On‐chip photodetectors are essential components in optical communications as they convert light into an electrical signal. Photobolometers are a type of photodetector that functions through a resistance change caused by electronic temperature fluctuations upon light absorption. They are widely used in the broad wavelength range from ultraviolet to mid‐infrared (MIR). In this work, a novel waveguide‐integrated bolometer that operates in a wide wavelength range from near‐infrared to MIR is introduced on the standard material platform with the transparent conductive oxides (TCOs) as the active material. This material platform enables the construction of both modulators and photodetectors using the same material, which is fully complementary metal–oxide–semiconductor compatible and easily integrated with passive on‐chip components. The photobolometers proposed here consist of a thin TCO layer placed inside the rib photonic waveguide to enhance light absorption and then heat the electrons in the TCO. This rise in electron temperature leads to decreasing electron mobility and consequential electrical resistance change. In consequence, a responsivity exceeding 10 A W−1 can be attained with a mere few microwatts of optical input power. Calculations suggest that further improvements can be expected with lower doping of the TCO, thus opening new doors in on‐chip photodetectors.

CNTs monitoring sensors for resin infusion optimization

The quality of composites manufactured by means of resin infusion depends to a significant extent on the expertise of operators. In order to improve both the reliability and performance of infusion, careful monitoring of the process is required. To this end, macroscopic filaments made of multi-walled carbon nanotubes (MWCNTs) were integrated into the fabrics of different materials and used to monitor the fluid front advance during vacuum-assisted resin infusion (VARI) experiments. In particular, the electrical resistance change of MWCNT fiber was continuously recorded while the resin was impregnating the fabrics. Although the method does not require complex equipment, its practical implementation is far from trivial, since several external variables can significantly affect the electrical measurements. In this work, fluid pressure in the laminate, temperature, fabric compaction, and electrical contacts between the carbon nanotube (CNT) yarns and the acquisition system were analyzed. It is concluded that temperature and the quality of contacts (CNT filament-electrode soldering) can have a striking effect on the electrical output and must be carefully controlled. The study used the hysteresis curve in the electrical resistance change appearing in different vacuum pressure cycles and fabrics to determine the position of the resin front.

Analytical Modeling of a Hydrogen Sensor Based on Exfoliated and Reduced Graphene Oxide

Hydrogen can be considered a clean energy carrier with zero carbon emissions, produced from renewable energy sources. However, hydrogen is a highly flammable gas and can form explosive mixtures with oxygen; hence, sensing techniques are essential for timely leak detection. This paper presents the experimental characterization of a hydrogen sensor based on sensing material consisting of thermally exfoliated/reduced graphene oxide (rGO) films deposited on a sensor device by the drop-coating technique. The measurement of changes in electrical resistance due to hydrogen gas exposure operating at different temperatures (27°C, 90°C, and 150°C) is carried out in a gas chamber with a known concentration of hydrogen in constant air flow. In addition, a generalized mathematical formulation is provided for the dependence of hydrogen gas concentration, temperature, and sensor resistance for the hydrogen gas sensor based on exfoliated/reduced graphene oxide.

A novel real time sensing framework for assessment of thrust force in drilling of composites using Taguchi and NSGA-II

Monitoring thrust during drilling operations is critical to optimizing drilling parameters and ensuring safe and efficient drilling. In this study, we will monitor variations in thrust force during the drilling process using a sensor coated with carbon black. These sensors measure changes in electrical resistance when the sensor is subjected to a mechanical load, such as drilling force. Carbon black at 5 wt% was used, which was embedded in a fiberglass composite. For this study, an orthogonal arrangement of Taguchi’s L27 sequence was used, with drill diameter D, feed rate F, and spindle speed S as machining parameters. The thrust force was measured with a force dynamometer and the resistance change was measured simultaneously with the developed new system. Analysis of variance was used to find the optimal parameters, and in this study, a mathematical model was proposed to measure the thrust force directly using the electrical resistance detected. NSGA-II algorithm was used to predict solutions for the given parameters for comparison. A comprehensive way of drilling process and data-driven decisions to improve drilling performance and safety was studied, and a correlation between actual thrust and calculated thrust of 0.91 was found. The proposed system was able to monitor and continuously record thrust force in real time during drilling, with electrical resistance as the most important factor with an error percentage of less than 8% compared to the NSGA-II predictions of less than 5%.

Influence of the Amount of Conductive Component on the Electrical Resistivity of Fine-Grained Electrically Conductive Concrete

Approaches to the production of electrically conductive concrete and the possibility of its application through the use of electrical properties in various industries are considered. The results of testing the compositions of fine-grained self-compacting concrete based on Portland cement CEM I 52.5 N, sand with a size modulus Mk=2.43 and polycarboxylate plasticizer for changes in electrical resistivity during hardening are presented. The increase in specific electrical conductivity was provided by the introduction of conductive components in various quantities, such as construction soot, carbon black K-354, graphite EUT-2. The positive effect of increasing the amount of the conductive component on the electrical resistivity for 28 days of normal hardening of the samples and on the ability to resistive heating by changing the surface temperature of the samples when passing a direct current with a voltage of 30 V. is shown.

Mega‐Tidal and Surface Flooding Controls on Coastal Groundwater and Saltwater Intrusion Within Agricultural Dikelands

AbstractClimate change will increase sea levels, driving saltwater into coastal aquifers and impacting coastal communities and land use viability. Coastal aquifers are also impacted by tides that control groundwater‐ocean interactions and maintain an “upper saline plume” (USP) of brackish groundwater. Coastal dikes are designed to limit the surface impacts of high‐amplitude tides, but, due to ongoing sea‐level rise (SLR), low‐lying dikelands and underlying aquifers are becoming increasingly vulnerable to flooding from high tides and storm surges. This study combines field observations with numerical modeling to investigate ocean‐aquifer mixing and future saltwater intrusion dynamics in a mega‐tidal (tidal range >8 m) dikeland along the Bay of Fundy in Atlantic Canada. Field data revealed strong connectivity between the ocean and coastal aquifer, as evidenced by pronounced tidal oscillations in deeper groundwater heads and an order of magnitude intra‐tidal change in subsurface electrical resistivity. Numerical model results indicate that SLR and surges will force the migration of the USP landward, amplifying salinization of freshwater resources. Simulated storm surges can overtop the dike, contaminating agricultural soils. The presence of dikes decreased salinization under low surge scenarios, but increased salinization under larger overtopping scenarios due to landward ponding of seawater behind the dike. Mega‐tidal conditions maintain a large USP and impact aquifer freshening rates. Results highlight the vulnerability of terrestrial soil landscapes and freshwater resources to climate change and suggest that the subsurface impacts of dike management decisions should be considered in addition to protection measures associated with surface saltwater intrusion processes.

Effect of CNT on the Physical and Electrical Properties of CNT/UHMWPE Nanocomposite Sensor

Nano Composites Polymer represents a class of multifunctional sensors that can effectively respond to changes in electrical properties when subjected to external forces acting on their physical characteristics. The research aims to develop nanocomposite polymer sensors that can respond well and be easily molded. The experimental process involved mixing Ultra-high-molecular-weight polyethylene (UHMWPE) with 1%, 4%, and 7wt% of carbon nanotubes (CNT) using the hot pressing method, leading to remarkable improvements in the electrical and mechanical properties of the composite polymers. The distribution patterns of CNT at different weight ratios showed that 4 wt% exhibited a more desirable and uniform distribution. However, at 1 wt%, the amount of CNT was insufficient, resulting in scattering and disconnection. On the other hand, at 7 wt%, the CNT distribution appeared to be densely bundled in some areas, leading to detrimental effects on the mechanical and electrical properties, as well as the electrical percolation threshold of the composites. Regarding the mechanical properties test, significant improvements were found at 4 wt% for the tensile strength, but when the filler content exceeded 4 wt%, there was a reduction in the tensile strength of the CNT/UHMWPE composites. Additionally, the change in electrical resistance based on the physical characteristics was examined by varying the percentage of CNT added to UHMWPE through compression and bending tests. The compression tests were conducted using weights ranging from 0 to 10 kg, and the bending tests were performed with angles from 0° to 40° degrees. In terms of the test results, however, with 4% and 7% wt% CNT filler, the electrical resistance values could be successfully measured by a multimeter. The electrical percolation threshold was found to be very good at 4 wt%. For the compression testing results, the resistance values ranged from approximately 27.329 to 32.389 KΩ for the 4 wt% filler and from 0.504 to 0.552 KΩ for the 7 wt% filler. As for the bending testing, the resistance values ranged from approximately 4.019 to 4.044 KΩ for the 4 wt% filler and from 0.427 to 0.432 KΩ for the 7 wt% filler.

Feasibility of room temperature detection of low energy single ions using nanometer-thick graphite

In this work, we demonstrate the feasibility of detecting low energy single ions using nanometer-thick and few-micrometer-wide graphite flakes at room temperature. We used electrically contacted samples of highly oriented pyrolytic graphite and measured in situ the change in electrical resistance upon ion irradiation using a self-made nanovoltmeter. Eight samples of different dimensions were prepared and subjected to ion irradiation from various species. A fluence as low as 5×108cm−2 corresponding to a few hundreds of ions irradiated was sufficient to produce a signal significantly above the noise level. Furthermore, we used a model to describe the dependence of the change in electrical resistance on the defect concentration induced by ion irradiation. By extrapolating this model to the level of single ions, our findings support the feasibility of detecting single ions at room temperature using thin graphite as a detector material.