Monitoring Of Electrical Conductivity Research Articles

Characterising the discharge of hillslope karstic aquifers from hydrodynamic and physicochemical data (Sierra Seca, SE Spain)

Groundwater flow has been investigated in the Sierra Seca, Spain. Maximum recharge to the central core of the mountain occurs at high elevations, which provides recharge to two overlapping karst aquifers constituting a groundwater storage zone at a lower elevation break in slope. Both karst aquifers are associated with three springs arising from the upper part of the permeable formations. The climate is characterized by long and intense periods of drought and short periods of rainfall, which trigger discharges from the springs. Spring flow recession curve analysis, cross-correlation and monitoring of groundwater temperature and electrical conductivity have demonstrated contrasts observed in the hydrodynamic and physicochemical response of the three springs during flood events. One spring records floods with narrow and short peaks of high discharge accompanied by sharp drops in temperature and electrical conductivity. Another spring records floods with somewhat wider peaks and sharp increases in temperature and electrical conductivity (piston effect), whereas the third spring shows great consistency in all monitored characteristics. It is concluded that the absence of a piston effect in the spring with the highest flow rates is due to the contribution of rapidly circulating water that is expelled by semi-active karst networks (overflow) before reaching the saturated zone, which does not occur in the other springs due to the absence of overflow hydrological pathways. The most regular spring owes its functioning to the contribution of infiltrated water in the bed of an upstream riverbed, which explains this regularity.

Nano-engineered versatile Janus natural-skin with sandwich structure for wearable all-season personal thermal management

Thermal management wearables hold significant promise for various applications, such as bio-integrated electronics, multifunctional fabrics, thermoelectric devices, etc. Given the complex and volatile external environmental conditions they may encounter, thermal management wearables should possess versatile and comprehensive auxiliary functions to enable cutting-edge advanced applications. Herein, we present a multifunctional nano-engineered Janus-type natural-skin (SHRC-skin) offering dual-modes of solar heating and radiative cooling. Additionally, the SHRC-skin integrated functionalities like flammability resistance, electromagnetic interference (EMI) shielding, and physiological signal monitoring achieved through the integration of traditional spray techniques and a phase-conversion pathway on natural-skin as a substrate, SHRC-skin enabled all-season thermal management. The radiative cooling side of the SHRC-skin incorporates a CA/Mg11(HPO3)8(OH)6 composite coating with an irregular porous structure, while the solar heating side consists of multi-walled carbon nanotubes (MWCNT) with a rough structure. The radiative cooling layer exhibited a solar reflectance of ∼90.13 % and a mid-infrared emittance of ∼87.6 %, whereas the heating layer demonstrated a solar absorptance of ∼89 %. These attributes translated to excellent thermal management performance in outdoor-tests. Furthermore, SHRC-skin offered extensive additional functionalities, including exceptional asymmetric wetting, flame retardancy, electrical conductivity, Joule heating, electromagnetic shielding, and physiological signal monitoring. This versatility significantly enhances SHRC-skin's adaptability to complex and diverse environments. In summary, the multifunctional SHRC-skin seamlessly transitions between cooling and heating modes without additional energy input. This innovation holds great promise for all-season wearable thermal management, environmentally friendly travel, and energy-efficient building furnishings, and opens new possibilities for the development of wearable materials across various scenarios.

Investigating Landsat data for continuous monitoring of ground electrical conductivity: implication for propagation at medium frequency in Ondo West

Ground electrical conductivity (GEC) has many applications, which makes it worthy of continuous research. Apart from the configurations of the radio transmitter and receiver, it is a major determinant of the electric field intensity of radio waves in the Medium Frequency (MF) band. It is usually measured in such a way that both the researcher and the measuring instrument are in direct contact with the ground, and measurements are made at some predetermined constant intervals to ensure good spatial coverage and even spatial distribution. The direct method becomes cumbersome when the field of study is large because the GEC over the licensed coverage area must be known such that electric field intensity can be predicted. At the planning stage, this ensures all parts of the licensed region are reached by useful signals that can suppress interference at all times and seasons. The study is motivated by the possibility of using Landsat to estimate GEC. This study utilizes Landsat images to first estimate the normalized difference salinity index and then, with the aid of map algebra, generate another raster 2 whose pixels' values are the GEC. The study covers a landmass of 967 km in the Ondo West Local Government Area (OWLGA). During analysis, the GEC was divided into five classes. The results reveal that the ranges of very low, low, moderate, high, and very high GEC are 0.124 to 0.437, 0.438 to 0.937, 0.938 to 1.635, 1.636 to 2.524, and 2.525 to 3.600 mS/m, which have mean values of 0.346 ± 0.109, 0.754 ± 0.103, 1.071 ± 0.089, 1.351 ± 2 0.067, and 1.564 ± 0.106 mS/m, and are dispersed over 176.45, 202.24, 214.14, 374.17, and 228.56 km , respectively. The values of GEC, their respective coverage, and spatial distribution recorded in this study are strong enough to sustain the propagation of useful electric field intensity over the entire landmass of Ondo West Local Government if a medium wave is established. The study recommends that the change in GEC with time in this field be studied.

Application of the eddy current method for flaw detection of conductive tracks of printed circuit boards

The article discusses the creation and testing of a hardware-software complex aimed at examining the conductive paths on printed circuit boards. The complex includes a tiny eddy current transducer and a measuring system specifically designed to work with the transducer. The proposed system, which combines software and hardware components, allows for the examination of small sections of metal objects. It enables the monitoring of electrical conductivity and the determination of conductivity distribution across the object’s surface and depth. The article provides detailed explanations of the key features of the measuring system and presents the experimental findings obtained by testing different printed circuit boards. These boards were examined under various conditions, including defect-free ones and those intentionally modified to simulate defects. Dependences between the eddy current transducer signal and the different conductive tracks were established, elucidating the relationship between the transducer’s response and the properties of the tracks.

Application of Benthic Microbial Fuel Cells in Systems of Year-Round Monitoring of Water Environment Parameters

The bioelectrogenic activity of sediments of natural microbial association of the Peter’s Bay of Japanese sea research was performed in a year-round experiment with parallel temperature, illumination and water electrical conductivity monitoring by means of benthic microbial fuel cell (MFC) and automatic online-monitoring. Several variants of underwater devices, including benthic microbial fuel cells, monitoring water environment sensor,information collection and transmission systems, have been developed. This device make electrical voltage up to 216 mV, specific power up to 239 mW/m2. Electrogenic activity of natural microflora depends on water temperature and reach maximum on summer with temperature about 20–25°C. The introduction of toxicants in form as hydrocarbons and cadmium into the sluge led to the suppression of microbial electrogenesis. However the introduction of inductor substances of microbial sulfidogenesis led to the stimulation of microbial electrogenesis. The possibility of functioning of the benthic MFC in the field of the Peter’s Great Bay in various climatic periods is shown. It is shown that such experimental devices serve as a basis for autonomous stations monitoring the state of the aquatic environment for a long time and in a wide range of conditions change. Thus, automatic registration of temperature, illumination and salinity of water with a frequency of 48 times a day was carried out for 13 months (11/28/2019–12/31/2020). The electrogenic activity of this microbiota upon MFC scaling can potentially become a new renewable energy source for low-power marine electronics, including those used in mariculture.

Ultrafast extraction of cold brew coffee in a planetary rotating bed reactor: A kinetic study on the pushback effect

AbstractGiven the rising demand for cold brew coffee, innovative approaches are required to address the present difficulties in its production. This motivates the consideration of the planetary rotating bed reactor (PRBR) as a solid–liquid extraction technology. The PRBR consists of cylindrical mesh chambers that contain the solid phase and move in two superimposed rotations. This motion pattern enhances mass transfer through alternating radial forces: the pushback effect (PBE). To evaluate the utility of the PRBR and the role of PBE, we investigated the kinetics and energy demand of cold brew coffee extraction. For this purpose, we varied rotational speeds and PBE conditions in a 1 L lab‐scale reactor. Kinetics was determined by in‐line monitoring of electrical conductivity correlated with the eluate's weight‐based total dissolved solids and caffeine by high‐performance liquid chromatography. Energy consumption was derived from strain gauge torque measurements. Our findings reveal that saturation of the extraction rate with respect to the rotational speed is evident both with and without PBE. However, PBE significantly reduces extraction time by 75% while requiring 60% less mechanical energy. The fastest conditions probed 95% of the maximum extraction yield within 12 s, effectively being >99% faster than static immersion. We believe these findings, along with further procedural advantages, qualify the PRBR as a viable technology for cold brew coffee production.Practical ApplicationsThe relevance of an economical and sustainable preparation of cold brew coffee extends from the industrial to the gastronomic to the domestic environment. Challenges and limitations relate to process time, particle separation, product and extraction yield, and taste problems due to over‐extraction. The planetary rotating bed reactor (PRBR) promises to address all these issues by combining extraction and separation in a simultaneous and ultrafast process. The present study confirms the superiority of PRBR's action mechanisms in terms of rapidity and energetic efficiency for extraction. Due to the excellent scalability of both the design and the physical effect, the PRBR is intended for large‐scale production of ready‐to‐drink products and local production in coffee shops or private households. By modifying the particle feed, even continuous operation is conceivable. Further applications are, for example, dry‐hopping of beer, fast‐aging of spirits, and preparation of various liquid foods.

Reversible Intercalation of Protons in Tungsten Oxide Films for Multi-Transduction Sensor Applications

Tungsten oxide films under electrochemical bias, can form tungsten oxide bronzes (MxWO3 with M being small cations such as H+ or Li+) featuring high electronic conductivity and change in coloration to deep blue1. This doping process occurs through the reduction of W6+, as described by the following equation:WO3 + x H+ + xe- -> HxWO3The bronze phase can also be formed through exposure of tungsten oxide to H2 at high temperatures (> 200 oC) or in presence of catalysts2, as described by the following equation:WO3 + x/2 H2 -> HxWO3 Because of the significant changes in both optical and electrical proprieties of the films, electrochemical control of proton doping can be used as a strategy for the development of ion-gated transistors3,4, hydrogen sensors and smart windows5.In this work, we report the use of thin films prepared by sol-gel synthesis using polyperoxotungstic acid (PPTA) as a precursor. We used three different types of substrates (conductive transparent fluorine-doped tin oxide (FTO) glass, Si/SiO2 patterned with Au source-drain electrodes and Interdigitated electrodes patterned on transparent glass) to study the changes of color and conductivity following the formation of the bronze in both electrochemical and dry environments. In electrochemical environment, we show that gating by ionic liquid in transistor configuration can be used to propose an iontronic sensor to detect H2 and H2O6. In dry environment, we show that simultaneous monitoring of visible light transmittance and electrical conductivity can be used a double transducer for H2 sensors6.1 M. S. Whittingham, in Solid State Ionics, 2004, vol. 168, pp. 255–263.2 C. C. Chan, W. C. Hsu, C. C. Chang and C. S. Hsu, Sensors and Actuators, B: Chemical, 2011, 157, 504–509.3 M. Barbosa, X. Meng, F. Soavi, C. Santato and M. O. Orlandi, J Mater Chem C Mater, 2018, 6, 1980–1987.4 G. V. de Oliveira Silva, A. Subramanian, X. Meng, S. Zhang, M. S. Barbosa, B. Baloukas, D. Chartrand, J. C. Gonzáles, M. O. Orlandi, F. Soavi, F. Cicoira and C. Santato, J Phys D Appl Phys,5 G. Cai, J. Wang and P. S. Lee, Acc Chem Res, 2016, 49, 1469–1476.6 M. S. Barbosa, R. A. da Silva, C. Santato and M. O. Orlandi, Journal of Vacuum Science & Technology A, 2022, 40, 013202.

Rheology and setting time of saline cemented paste backfill

As many mines around the world are situated in freshwater-scarce regions and corporations are challenged to meet increasing sustainability and environmental responsibility standards, many mining operations are seeking to use locally available saline groundwater or ocean water as mixing water in cemented backfill. However, the implications of this decision on the rheological properties (which control the flow ability or transportability) and setting time of cemented backfill must be better comprehended to allow for a confident selection of this practical solution. Hence, the effects of mixing water salinity and binder type on the rheological properties and setting time of cement paste backfill (CPB) were investigated. Viscosity, yield stress, and setting time testing were conducted on CPB made with Portland cement type I (PC) and varying slag replacement quantities, silica tailings (ST), and mixing water with NaCl concentrations from 0 g/L to 300 g/L. Supplemental testing and analyses included pH determination, TG/DTG and XRD microstructure analyses, zeta potential measurements, and electrical conductivity monitoring. Results indicate that low NaCl concentrations (10 g/L − 35 g/L) in PC-CPB increased the yield stress above the control while higher concentrations (100 g/L − 300 g/L) decreased it. An increase in NaCl concentration led to slower increase in viscosity over the first two hours of curing. Low NaCl concentrations reduced the time to initial and final setting while high concentrations increased it. These behaviors were mainly due to the effects of the Na and Cl ions on the dissolution of the cement components, and on the changes in zeta potential due to chloride adsorption. Increases in slag replacement quantities on saline CPB had minimal effect on the yield stress during the first two hours after mixing but decreased the viscosity. All tested slag contents increased the time to initial setting, though a replacement content of 75% did not increase the initial setting time as much as lower quantities. A slag replacement content of 25% increased the final setting time, though higher contents decreased it. This behavior was due to the slower reaction rate of slag, combined with slag’s consumption of NaCl and CH and greater chloride binding capabilities. The results of this study will aid mines in designing more cost-effective and efficient backfill programs.

Use of a Dielectric Sensor for Salinity Determination on an Extensive Green Roof Substrate.

The irrigation of extensive green roofs with recycled or saline water could contribute to the conservation of valuable drinking water supplies. In such cases, the continuous monitoring of substrate electrical conductivity (ECsw) is of immense importance for the sustainable growth of the plants growing on the green roof. The present study aimed to estimate the ECsw (pore water EC) of an extensive green roof substrate in lysimeters with the use of the WET-2 dielectric sensor. Half of the 48 lysimeters that simulated extensive green roofs had a substrate depth of 7.5 cm, while the other half had a 15 cm substrate depth. The warm season turfgrass Paspalum vaginatum 'Platinum TE' was established at the lysimeters, and during the summer period, it was irrigated every two days at a rate of 14 mm with NaCl solutions of various electrical conductivities (ECi): (a) 3 dS m-1, (b) 6 dS m-1, and (c) 12 dS m-1, while potable water of 0.3 dS m-1 ECi served as the control. The relation between bulk electrical conductivity, σb, and bulk dielectric permittivity, εb, of the substrate was observed to be linear for all ECi levels up to σb values of 2-2.5 dS m-1. The ECsw was predicted by employing the salinity index method which was modified to be applied to the particular case of a green roof substrate. Knowing the salinity index and organic portion (%, v/v) for a given green roof substrate, we could calculate the ECsw. It was found that the use of the salinity index method predicts reliably the ECsw up to 10-11 dS m-1, while the method overestimates ECsw at very low levels of electrical conductivity.

Characterization of the Grigna karst aquifer (Northern Italy) by springs monitoring and tracer tests

Alpine and prealpine karst aquifers represent a considerable water reserve due to the extension of the carbonate massifs. These aquifers are particularly vulnerable and require careful monitoring and protection activities. The Northern Grigna massif (Western Orobic Prealps, Lombardy Region) represents one of the most significant karst areas in Northern Central Alps of Italy, characterised by a deep karst system and a high density of cave entrances. The Fiumelatte Cave and the Fonte Uga spring represent the main identified outflows of the Northern Grigna groundwater karstic system. Past tracer testing established the connection between the upper karst massif and the Fiumelatte Cave and suggested a possible link between the Esino river and the two springs.The characterization of the Grigna karst aquifer by an annual monitoring of the main springs and the interpretation of hydrochemical and hydrological data is the main topic of this paper. The continuous monitoring of water temperature, discharge, electrical conductivity and turbidity at Fiumelatte and Fonte Uga springs allowed to define a conceptual model of these connected discharge points within the karst system.Two multiple tracer tests with fluorescent dyes injected along the Esino river and deep into two caves enabled to better investigate the dynamics of the groundwater flow system and of the springs. The tests revealed the coexistence of different drainage systems within the karst massif and confirmed the relationship between Fiumelatte and Fonte Uga springs. The first one, a temporary spring which activates only after intense rainfall events or during the snowmelt period, represents the overflow system of the second one, which is a perennial spring.An updated model of the Grigna karst system is presented, with a particular focus on the hydrogeochemical characteristics of the main springs and on the flow network developed in the peculiar geological and structural setting of this karstic massif.

The Spatio-Temporal Dynamic Patterns of Shallow Groundwater Level and Salinity: The Yellow River Delta, China

Shallow groundwater in coastal aquifers is a highly dynamic and complex system with a high risk of seawater intrusion. Analyzing the spatio-temporal dynamic patterns of groundwater can help to manage the groundwater resource and prevent it from degradation. Based on the groundwater level (GWL) and electrical conductivity (EC) monitoring data of 18 observation wells in the Yellow River Delta (YRD) from 2004 to 2010, this research analyses the groundwater dynamics using a robust seasonal trend decomposition technique (STL) and spatial interpolation method to detect the groundwater spatio-temporal dynamic patterns of groundwater level and salinity. Combined with hydro-climatic data, the Pearson correlation method and the Mann-Kendall (MK) trend analysis were used to further reveal the impacts that induce their trends and seasonal variations. Our analyses show that the risk of seawater intrusion into local shallow aquifers in this region is high, with the mean groundwater level over 42% of the region lower than the local sea level, and the mean groundwater EC over 96% of the region met the standards for seawater intrusion. In addition, the trends of groundwater level generally declined by 0.01~0.45 m/a and salinity increased by 1.153~25.608 μs/cm.a, which are consistent with the trend of precipitation decline. The seasonal dynamics of groundwater level and salinity are highly correlated with the seasonal components of rainfall and evaporation. It can be concluded that the extent of seawater intrusion will increase in the future with sea level rise. The approaches used in this study proved to be effective and can certainly serve as an example for the analysis of the spatio-temporal dynamics of groundwater in other coastal regions.

In-situ electrical conductivity monitoring of slag solidification during continuous cooling for slag recycling

Large volumes of steel slag are produced annually, leading to significant environmental protection and sustainable development issues. An online technology to monitor the solidification process of steel slag can assist in obtaining the right mineralogy to valorize these slags or render them harmless. For this purpose, we investigated the electrical properties and microstructural relationships of a CaO-Al2O3-SiO2-MgO (CASM) slag during cooling using an innovative setup. The electrical impedance was determined over the frequency range of 20 Hz to 300 kHz at two cooling rates, and the solidification behaviour was observed simultaneously by confocal scanning laser microscopy (CSLM). Four zones can be distinguished in the conductivity-temperature curves for the slag cooled at 10 °C/min, whereas only two distinct zones are visible at 100 °C/min. The liquid fraction of the slag has a significant impact on the slag conductivity during cooling. The electrical conductivity is, therefore, an accurate indicator of the solidification degree. Different theoretical and empirical models were evaluated on their ability to relate the bulk conductivity of the slag to the liquid fraction. The empirical Archie’s model proved to be the most suitable model for relating the bulk conductivity of the slag to the liquid fraction. In-situ electrical conductivity measurements during cooling can provide an online assessment of the slag solidification process, including indicating the appearance of solid precipitates, monitoring the growth of crystals, indicating complete solidification when no liquid phase remains, and indicating the cooling rate.

Salinity Properties Retrieval from Sentinel-2 Satellite Data and Machine Learning Algorithms

The accurate monitoring of soil salinization plays a key role in the ecological security and sustainable agricultural development of semiarid regions. The objective of this study was to achieve the best estimation of electrical conductivity variables from salt-affected soils in a south Mediterranean region using Sentinel-2 multispectral imagery. In order to realize this goal, a test was carried out using electrical conductivity (EC) data collected in central Tunisia. Soil electrical conductivity and leaf electrical conductivity were measured in an olive orchard over two growing seasons and under three irrigation treatments. Firstly, selected spectral salinity, chlorophyll, water, and vegetation indices were tested over the experimental area to estimate both soil and leaf EC using Sentinel-2 imagery on the Google Earth Engine platform. Subsequently, estimation models of soil and leaf EC were calibrated by employing machine learning (ML) techniques using 12 spectral bands of Sentinel-2 images. The prediction accuracy of the EC estimation was assessed by using k-fold cross-validation and computing statistical metrics. The results of the study revealed that machine learning algorithms, together with multispectral data, could advance the mapping and monitoring of soil and leaf electrical conductivity.

Variation of the hydraulic properties in sandy soils induced by the addition of graphene and classical soil improvers

In this study, for the first time, the changes in relevant hydraulic parameters (e.g., hydraulic conductivity, effective porosity, and dispersivity) induced by the introduction of graphene in a calcareous sandy soil and a siliciclastic riverine soil were monitored and modelled via leaching column experiments. Column experiments were also run with traditional soil improvers (compost, biochar, and zeolite) to compare the changes induced by graphene versus well-studied soil improvers. Constant pressure head tests were used to calculate the hydraulic conductivity of each column, while leaching experiments were run to estimate porosity and specific retention, and for each treatment three replicates were done. Columns were then run in saturated conditions via a low flow peristaltic pump and monitored for electrical conductivity, temperature, and chloride. CXTFIT 2.0 was employed to inversely model the column experiments and retrieve parameters like effective porosity, longitudinal dispersivity, bulk thermal diffusivity, and thermal retardation factor. Results highlighted small changes of hydraulic conductivity, porosity, and effective porosity induced by graphene addition (as well as by the other soil improvers) for both soils. A marked increase (nearly 20 %) of specific retention values was instead recorded in the amended columns with respect to control ones. Chloride breakthrough curves modelling showed that graphene doubled dispersivity in the calcareous sandy soil (5.82 ± 1.4 cm) compared to the control (2.6 ± 0.29 cm), while it halved dispersivity in the siliciclastic riverine soil (0.31 ± 0.05 cm) with respect to the control (0.65 ± 0.06 cm). Thermal retardation factors were decreased by graphene by approximately 20 % for both soils. The model fitting via TDS (derived from the electrical conductivity monitoring) produced unreliable dispersivity values in most of the experiments due to the nonconservative nature of this parameter compared to chloride. The results highlight that graphene affected dispersivity but did not significantly alter other physical parameters relevant for solutes transport in sandy soils in comparison to classical improvers, thus future studies should focus on the graphene’s effects on nutrients and agrochemicals leaching in unsaturated flow conditions.

A Wireless Underground Sensor Network Field Pilot for Agriculture and Ecology: Soil Moisture Mapping Using Signal Attenuation.

Wireless Underground Sensor Networks (WUSNs) that collect geospatial in situ sensor data are a backbone of internet-of-things (IoT) applications for agriculture and terrestrial ecology. In this paper, we first show how WUSNs can operate reliably under field conditions year-round and at the same time be used for determining and mapping soil conditions from the buried sensor nodes. We demonstrate the design and deployment of a 23-node WUSN installed at an agricultural field site that covers an area with a 530 m radius. The WUSN has continuously operated since September 2019, enabling real-time monitoring of soil volumetric water content (VWC), soil temperature (ST), and soil electrical conductivity. Secondly, we present data collected over a nine-month period across three seasons. We evaluate the performance of a deep learning algorithm in predicting soil VWC using various combinations of the received signal strength (RSSI) from each buried wireless node, above-ground pathloss, the distance between wireless node and receive antenna (D), ST, air temperature (AT), relative humidity (RH), and precipitation as input parameters to the model. The AT, RH, and precipitation were obtained from a nearby weather station. We find that a model with RSSI, D, AT, ST, and RH as inputs was able to predict soil VWC with an R2 of 0.82 for test datasets, with a Root Mean Square Error of ±0.012 (m3/m3). Hence, a combination of deep learning and other easily available soil and climatic parameters can be a viable candidate for replacing expensive soil VWC sensors in WUSNs.

Real-Time Electrical Conductivity Monitoring and Correlation with Sulfate Release and Acid Mine Drainage Potential from a Gold/Silver Paste Tailing Storage

Safe disposal of tailings as high-density thickened tailings or paste tailings can reduce the environmental risks of conventional tailings deposits, reduce water use, minimize tailings storage facility footprints, reduce the potential for acid mine drainage (AMD), and minimize risks of failure, among other advantages. In the dewatering process, the addition of flocculants is key to improving the sedimentation of the tailings and the formation of a compact paste. Despite the environmental and operational advantages of using paste tailings, it is not clear how the chemical nature of coagulants and flocculants could influence the discharge of toxic elements (salts and metals) from tailings after storage. In this study, we show the results of the real-time evaluation of the release of polluting runoffs from a paste tailings deposit. To do this, we analyzed paste tailing samples for AMD potential through static and kinetic tests and monitored the electrical conductivity and real-time pH, evaluating the correlation with the sulfate in the thickener and downstream from the tailings deposit. Tailing samples have low sulfur content (<2%) and low acid-generating potential. Moreover, there is no evidence of a significant positive correlation (Pearson’s coefficient r < 0.8) between the sulfate concentrations with the pH or EC. Thus, the chemical nature of the paste tailings prior to discharge has no direct impact on the release of sulfate-rich runoffs from the tailings after its storage. This indicates that the tailings paste at the evaluated site is chemically stable in the short term.

Strain Sensing Behavior of 3D Printable and Wearable Conductive Polymer Composites Filled with Silane-Modified MWCNTs.

3D printing of conductive polymers is an attractive technique for achieving high flexibility, wearability, and sensing characteristics without geometrical limitations. However, there is an urgent need to integrate printability, conductivity, and sensing capability. Herein, a conductive polymer ink for 3D printing that combines the desirable features of high electrical conductivity, flexible stretchability, and strain-sensing monitoring is prepared. The ink matrix is polydimethylsiloxane and synergistically enhanced by acetylene carbon black (ACB) and multi-walled carbon nanotubes (MWCNTs) (silane or un-silane-modified). The inks are screened step-by-step to explore their printability, rheology, mechanical properties, and electrical performance upon loading. The formation of an electrically conductive network, electrical properties upon tensile load, and strain sensing stability under cyclic stretching are investigated intensively. It is demonstrated that conductive polymers filled by ACB and silane-modified, MWCNTs (MWCNTs-MTES) possess superior printability, stretchability, conductivity, and strain sensing behaviors. Finally, a flexible wearable strain-sensing skin patch is printed, and it successfully records joint motion signals on human fingers, wrists, and elbows with good stability and repeatability. Those results show the extent of potential applications in healthcare and motion monitoring fields. This work provides an efficient and simple route to achieve comfortably wearable and high-performance strain sensors.

Simulating and monitoring water flow, salinity distribution and yield production under buried diffuser irrigation for date palm tree in Saharan Jemna oasis (North Africa)

Irrigation in traditional oases in the Mena region was possible in the past via traditional techniques (foggaras, tabia) and a relative availability of water resources. To promote the development of sustainable oases, in the context of global changes and water resources scarcity and degradation, an assessment of an innovative subsurface irrigation system (Chahbani) was conducted in Saharan Jemna oasis (South of Tunisia). Irrigation water salinity (ECw) was classified brackish (ECw ranged between 3.2 dSm-1 and 4.5 dSm-1). Field investigations were conducted during two crop years (2018, 2019) for palm trees. Capacitance sensors (Decagon 5TE) were installed at six soil depths (0.15 m, 0.40 m, 0.60 m, 0.80, 1 m and 1.20 m) for real time monitoring of soil water moisture (θ) and pore electrical conductivity (ECp). A numerical model (HYDRUS (2D/3D)) was calibrated then applied to investigate the effect of different filed irrigation amounts ((T1F (73% crop evapotranspiration (ETc); T2F (120% ETc)) and different buried diffuser optimization (opt) positions from the trunk of the palm tree (X) and soil depths (Z): (T1opt (X = 1.5 m and Z = 0.3 m); T2Opt (X = 0.5 m and Z = 0.3 m); T3opt (X = 1.5 m and Z = 0.6 m); T4opt (X = 0.5 m and Z = 0.6 m)) on root water uptake, yield production and soil salinity distribution. Simulation results for both field treatments T1F and T2F showed that the amount of root water uptake was always lower than 100%(ETc) with observed yield equal to 45% and 50% for T1F and T2F, respectively. According to buried diffuser position scenarios, installation of the buried diffuser at the canopy of the date palm T1opt (X = 1.5 m) as used in Jemna oasis, showed the least calculated relative yield (37%). However, for lateral distance, X = 0.5 m, root water uptake was equal to 649 mm for T2Opt (Z = 0.3 m) and 855 mm for T4Opt (Z = 0.6 m) with relative yield equal to 54% and 71%, respectively. According to simulation results, all position scenarios showed salt accumulation on the top soil layers and leaching requirement fraction (LR) application failed to decrease salinity for 0–0.4 m soil depth. Supplemental leaching using surface irrigation is thus recommended. Further studies for irrigation with buried diffuser under arid climate and brackish water need to focus on its impact on oasis sustainability especially when used for traditional oases as irrigation system.

Evaluation of Fertilizer Electrical Conductivity (EC) and Temperature Distribution via Vertical Farming System under Plant Factory

A plant factory has been developed at Horticultural Research Centre, MARDI Serdang. The cultivation approach under the plant factory consists of nine units planting racks with each rack having seven tiers or levels that can cultivate up to 900 crops per rack. Each unit of planting racks has been installed with electrical conductivity (EC) and pH monitoring system. EC is a meaningful indicator of water quality, soil salinity and fertilizer concentration. In this study, the data for EC and temperature were taken for each level different locations (three points along the rack) to evaluate the fertilizer quality distribution. The objective of the study was to evaluate the effectiveness of EC and temperature distribution on the planting rack of vertical farming system under the plant factory. From the study, it was found that EC and temperature parameters were not significantly different at each level and the point location of the vertical farming system. EC and temperature parameters were significantly different with the time (week) and point location from week to week. The effect of the interaction between time (week) and level on EC and temperature parameters were not statistically different. Therefore, it can be concluded that the effect of EC and temperature distribution at different levels of the vertical farming system did not depend on the time.

Variations of springs water conductivity the selected springs at the flank of Mount Rajabasa, Lampung

Continuous Electrical conductivity (EC) monitoring has been carried out on springs in the lower slopes of The Mount Rajabasa. The research is intended to find the variation of EC in volcanic springs as a signal to understand groundwater flow regimes. Data evaluation makes use of frequency distribution from statistical methods. The results give clear information for each character of the spring measured at the research site.