Variation Of Electrical Conductivity Research Articles

Electromagnetic Sensing of the Corrosion at Different Microstructural Phases in a Medical Ti-6Al-4V ELI Alloy

Titanium alloys have become increasingly important for biomedical materials due to their high specific strength, good corrosion resistance, and excellent biocompatibility. In this research work, different heat treatments were performed for obtaining equiaxed and Widmanstätten microstructures of Ti-Al-4V extra low interstitials (ELI) alloy. To promote nucleation of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha _{2}$ </tex-math></inline-formula> precipitates (Ti <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Al), an aging process was carried out at 515 °C and 575 °C for 2, 288, and 576 h. The corrosion behavior was analyzed by double-cycle potentiodynamic corrosion tests. Hank’s balanced salt solution (HBSS) was used as the electrolyte, and the tests were maintained at 37 °C. This study uses the eddy current (EC) nondestructive evaluation technique, based on the principle of electromagnetic induction, in an effort to monitor corrosion damage in the medical Ti-6Al-4V alloy. The experimental results show significative electrical conductivity variations in EC data of different Ti-6Al-4V ELI alloy microstructures mainly on equiaxed and Widmanstätten conditions before and after corrosion performance.

EVALUATION OF SOIL SALINITY OF THE FETZARA LAKE REGION (NORTH-EAST ALGERIA)

Fetzara lake, located at 18 km southwest of Annaba city, is one of the largest lakes in the extreme northeastern Algeria. In 2002, the Ramsar convention classified it among the wetlands of international importance. In this study, we aim to evaluate soil properties of Fetzara lake region, which are very sensitive to salinization phenomena, and their evolution according to depth. A sampling companion was carried out on the first two superficial levels 0 to 25 cm and 25 to 50 cm. A total of 24 samples, gathered from 12 sites distributed around the lake perimeter, were analyzed for their physical and physico-chemical properties. Results show that the majority of the soils samples are classified as saline soils (ESP ≤ 15%, EC &gt; 4 mS cm -1 ), with a highly variable electrical conductivity (6.52 to 24.3 mS cm -1 ), reaching its maximum in both northeastern (Wadi Zied town) and southeastern part of the lake (Cheurfa town). Moreover, the soil solutions are characterized by the abundance of ions such as Cl - , SO 4 2- , Na + and Mg 2+ , giving a dominant sodium chloride facies in most of the analyzed samples.

First-principles and machine-learning study of electronic and phonon transport in carbon-based AA-stacked bilayer biphenylene nanosheets

In this study, the structural, electronic and thermal transport properties of AA-stacked bilayer biphenylene sheet (BPN) are systematically investigated in the framework of first-principles calculations in addition to machine-learning interatomic potential approaches. Optimized geometry of AA-stacked bilayer satisfies all the necessary stability criteria which further infers that structure becomes feasible for experimental design. Similar to monolayer BPN, its bilayer variant also exhibits a metallic band structure. Thermal transport characteristics of the AA-stacked bilayer have been analyzed from thermal conductivity, the Seebeck coefficient, and electrical conductivity variations. The electronic part of the thermal conductivity for AA-stacked bilayer Biphenylene exhibits linearly enhancing character with temperature, whereas lattice contributions possess an inverse function of temperature. Moreover, the negative values of the Grüneisen (γ) parameter for AA-stacked bilayer BPN dictate negative thermal expansion which can have potential application to tailor the thermal expansion coefficient in many practical situations.

High electrical properties and good upconversion luminescence in SrBi1.94-xEr0.06YbxNb2O9 lead-free piezoelectric ceramics

SrBi1.94-xEr0.06YbxNb2O9 (x = 0.000, 0.002, 0.004 and 0.006, noted as SBEN-xYb) composites were prepared using traditional solid-phase sintering technology. The influences of (Er, Yb)3+ co-doping on the electrical and luminous properties as well as energy band structure of SrBi2Nb2O9 (SBN) ceramics were systematically investigated. The outstanding comprehensive characteristics with low dielectric loss (tanδ ~ 0.073%), high remnant polarization (2Pr ~ 10.73 μC/cm2), large piezoelectric responses (d33 ~ 15 pC/N) and excellent upconversion photoluminescence (UC-PL) are simultaneously observed by Yb doping with a concentration of x = 0.004. The UC-PL spectrum excited by 980 nm laser shows double bands at 533 nm and 554 nm in the green region, and single band at 672 nm in the red region. A density functional theory (DFT) calculation was performed to reveal the physical origin of electrical conductivity and UC-PL. It is seen that the band gap consistently decreases, while the contribution from f state of (Er, Yb)3+ is intensified with increasing Yb3+, elaborating the variations of electrical conductivity and UC-PL intensity. Related mechanisms for the improvement of UC-PL and electrical properties were discussed.

Machine learning approach towards explaining water quality dynamics in an urbanised river

Human activities alter river water quality and quantity, with consequences for the ecosystems of urbanised rivers. Quantifying the role of human-induced drivers in controlling spatio-temporal patterns in water quality is critical to develop successful strategies for improving the ecological health of urban rivers. Here, we analyse high-frequency electrical conductivity and temperature data collected from the River Chess in South-East England during a Citizen Science project. Utilizing machine learning, we find that boosted trees outperform GAM and accurately describe water quality dynamics with less than 1% error. SHapley Additive exPlanations reveal the importance of and the (inter)dependencies between the individual variables, such as river level and Wastewater Treatment Works (WWTW) outflow. WWTW outflows give rise to diurnal variations in electrical conductivity, which are detectable throughout the year, and to an increase in average water temperature of 1 rm{^o}C in a 2 km reach downstream of the wastewater treatment works during low flows. Overall, we showcase how high-frequency water quality measurements initiated by a Citizen Science project, together with machine learning techniques, can help untangle key drivers of water quality dynamics in an urbanised chalk stream.

Oxygen-Deficient (Ln,Sr)2NiO4- δ Nickelates for Oxygen Electrodes of Solid Oxide Fuel and Electrolysis Cells: Anisotropic Thermochemical Expansion and Thermomechanical Constraints

Perovskite-like and perovskite-related oxides based on variable-valence transition metals may exhibit substantial changes in oxygen content in the course of temperature cycling or under variation of oxygen chemical potential at elevated temperatures. This gives rise to a chemical contribution to the thermal expansion (chemical expansion/contraction or chemical strain) originating mainly from the accompanying changes in the average oxidation state of transition metal cations and, consequently, their ionic radii. Excessive dimensional changes caused by the chemical expansion impose constraints on the applicability of functional oxides at elevated temperatures and under variable redox conditions (due to thermomechanical instability or incompatibility with other materials) and complicate the processing of oxide ceramics at high temperatures. Another unfavorable phenomenon is microcracking caused by a strongly anisotropic expansion of crystal lattice, with effects on the microstructural and mechanical integrity and electrical and electrochemical properties. The present work is a representative study case that focuses on layered Ln2NiO4-based ceramic materials for oxygen electrodes of solid oxide fuel/electrolysis cells (SOFC/SOEC).Ln2NiO4+δ–based oxides (Ln = La, Pr, Nd) with perovskite-related K2NiF4-type structure demonstrate high oxygen diffusivity and surface exchange kinetics in combination with comparatively high electronic conductivity and are considered, therefore, as attractive mixed ionic-electronic conductors for oxygen electrodes of high-temperature SOFC/SOEC [1]. Acceptor-type substitution of Ln3+ by Sr2+ in Ln2NiO4+ δ is compensated by comparatively high oxygen deficiency in Sr-rich Ln2-xSrxNiO4-δ phases at elevated temperatures [2,3]. The transition from oxygen excess to oxygen deficiency is expected to be accompanied by a change in the ionic transport mechanism from prevailing interstitial oxygen diffusion in rock-salt layers to oxygen vacancy diffusion in perovskite-type layers.Ceramic powders of Ln2-xSrxNiO4-δ (Ln = La, Nd, Pr, x = 1.0-1.6) were prepared by the Pechini method with final calcination steps at 1150-1200°C in oxygen. Thermogravimetric studies confirmed that acceptor-type substitution by strontium is compensated by the formation of oxygen vacancies and electron-holes and progressively increases high-temperature oxygen nonstoichiometry (Fig.1A), which reaches as high as δ = 0.36-0.40 for x = 1.6 at 900°C in air. High-temperature XRD studies demonstrated that Ln2-xSrxNiO4-δ nickelates exhibit strongly anisotropic lattice expansion interrelated with oxygen deficiency changes on heating (Fig.1B). Highly anisotropic expansion induces microcracking phenomenon, which, in turn, results in a strong hysteresis in dimensional changes (Fig.1C) and also in variations of electrical conductivity (Fig.1D) on cycling in air for the ceramic samples sintered at 1200-1300°C.An appropriate approach to minimize or neglect the undesirable effects of anisotropic expansion and microcracking is to preserve the grain size in Ln2-xSrxNiO4-δ ceramics or porous electrodes at ~1 micron or submicron level. In particular, spark plasma sintering with subsequent careful oxidation treatment was adopted to avoid grain growth and to produce mechanically stable ceramics with smooth reversible thermochemical expansion and enhanced electrical properties. Acknowledgments: This work was supported by the FCT/MCTES/FEDER (projects CARBOSTEAM (POCI-01-0145-FEDER-032295) and CICECO-Aveiro Institute of Materials (UIDB/50011/2020, UIDP/50011/2020 & LA/P/0006/2020), and PhD grant SFRH/BD/138773/2018).

Template Synthesis and Characterization of Ni Nanostructures

Nanostructures of a typical ferromagnetic material, nickel are fabricated by electro-deposition (in a DC mode) within the pores of polycarbonate track etched membranes. The cylindrical pores with pore diameter 100 nm have been used for present study. Negative template method via two electrode potentiostatic arrangement in electrochemical cell has been used to synthesize the ordered array of one-dimensional Ni nanostructures. Deposition has been carried out at \(41\pm2\) degree, 1.6 V and so formed one dimensional nanostructure has been obtained at a Copper substrate. The elegant approach of template synthesis has advantage that shape and diameter of one-dimensional nanostructure can be varied as per the requirement, by using the templates of different pore shapes and diameters. Crystalline nature of one-dimensional Ni nanostructures is confirmed by X-ray spectroscopy using Rigaku X-ray diffractometer. I-V characteristics have also been drawn using Keithley source meter, in order to check out the variation in electrical conductivity from bulk to nanoscale.

Nutrient dynamics under unmanaged rubber, cocoa, and oil palm plantations in a sandy soil under humid lowland tropical climatic conditions

Changes in land use are an important issue in many farms that affect soil biological, chemical, and physical properties temporarily under cropping cycles or when the land is permanently allocated to perennial tree crops, e.g., in agroforestry. This study investigated the changes in sandy soil chemistry induced by three perennial tree crops (rubber, cocoa, and oil palm) growing in 30-year-old unmanaged and abandoned plantations and the surrounding grasslands dominated by cogon grass. A disruptive approach was used to collect soil samples from the top 60 cm under all the tree crops and in the grassland soils. A 500-gram sample of each soil originating from under each tree crop and the grassland were carefully packed into pre-labeled paper bags in triplicate (n=3) and sent to the laboratory for analysis of a selected number of primary and secondary macronutrients, micronutrients, and other soil parameters. The results showed N, K, Mg, Cu, Zn, and S were generally deficient in the sandy soil. A tree crop-specific soil organic matter, organic carbon, carbon stock contents, and water holding capacity measured were high under rubber and cocoa only. The variation in pH, electrical conductivity, bulk density, total porosity, and particle composition were generally similar except that the sand composition was lower in the soils under rubber and oil palm.

Assessment of the impact of abattoir effluent on the physico-chemical and microbiological characteristics of the Effurun River, Effurun and Eburu Canal, Warri in Delta State, Nigeria

Water is said to be polluted when it is impaired by anthropogenic contaminants and natural phenomena. An assessment of the impact of effluent from the Effurun market abattoir and Eburu abattoir on the physico-chemical parameters of the Effurun River, Effurun and Eburu canal, Warri, Delta State was carried out from July to December 2015 at three designated stations: station 1 (Upstream of effluent discharge point), station 2 (Effluent discharge point) and station 3 (Downstream of effluent discharge point). In the Effurun River, analysis of variance (ANOVA) revealed significant spatial variation (P&lt;0.05) in electrical conductivity, salinity, BOD5 (Biological Oxygen Demand), COD (Chemical Oxygen Demand), TSS (Total Suspended Solids), PO4 (Phosphate), TS (Total Solids), and TDS (Total Dissolved Solids) while in Eburu canal, significant spatial variation (P&lt;0.05) was observed in salinity, BOD5, TS, TDS and TSS. A posteriori test using the Duncan Multiple Range (DMR) test revealed that these indicator parameters were significantly higher in station 2 than in the other stations of the Effurun River and Eburu canal. The values of fecal coliform count and total coliform count increased from station 1 to station 2 and slightly decreased in station 3 in the Effurun River and Eburu canal respectively. Chi-square goodness of fit showed significant difference (P&lt;0.001) in station 2. Both water bodies showed very low recovery capacities (less than 50%). The current water quality status of both water bodies from the discharge of abattoir effluents poses environmental and health problems to the end users. Most of the parameters exceeded the regulatory limits hence the need to treat waste before discharging into the ecosystem.

Exploring the Capabilities of a Piezoresistive Graphene-Loaded Waterborne Paint for Discrete Strain and Spatial Sensing.

The development of a piezoresistive coating produced from dispersing graphene nanoplatelets (GNPs) inside a commercial water-based polyurethane paint is presented. The feasibility of its exploitation for realizing highly sensitive discrete strain sensors and to measure spatial strain distribution using linear and two-dimensional depositions was investigated. Firstly, the production process was optimized to achieve the best electromechanical response. The obtained materials were then subjected to different characterizations for structural and functional investigations. Morphological analyses showed a homogenous dispersion of GNPs within the host matrix and an average thickness of about 75 µm of the obtained nanostructured films. By several adhesion tests, it was demonstrated that the presence of the nanostructures inside the paint film lowered the adhesion strength by only 20% in respect to neat paint. Through electrical tests, the percolation curve of the nanomaterial was acquired, showing an effective electrical conductivity ranging from about 10−4 S/m to 3.5 S/m in relation to the different amounts of filler dispersed in the neat paint: in particular, samples with weight fractions of 2, 2.5, 3, 3.5, 4, 5 and 6 wt% of GNPs were produced and characterized. Next, the sensitivity to flexural strain of small piezoresistive sensors deposited by a spray-coating technique on a fiberglass-reinforced epoxy laminate beam was measured: a high gauge factor of 33 was obtained at a maximum strain of 1%. Thus, the sensitivity curve of the piezoresistive material was successively adopted to predict the strain along a multicontact painted strip on the same beam. Finally, for a painted laminate plate subjected to a mechanical flexural load, we demonstrated, through an electrical resistance tomography technique, the feasibility to map the electrical conductivity variations, which are strictly related to the induced strain/stress field. As a further example, we also showed the possibility of using the coating to detect the presence of conducting objects and damage.

Oxygen nonstoichiometry effects in spin Seebeck insulating Y3−xPrxFe5O12+ δ materials

Yttrium iron garnet (Y3Fe5O12) and its derivatives are ferrimagnetic spin Seebeck insulating materials crucial for the spin transport based phenomena such as the spin Seebeck effect (SSE) and spin Hall magnetoresistance. Structure–property correlation studies of such materials under different conditions are useful for optimizing the relevant constraint in the existed phenomena. The usage of Y3Fe5O12 type materials over the broad range of temperature conditions (27–450 °C) in SSE is under study. We report here the structure–property correlation in spin Seebeck insulating Y3−xPrxFe5O12+δ oxides as a representative material and introduce the additional degrees of freedom in the crystal system relevant to the spin transport based phenomena under high temperature conditions. The natural tendency of having oxygen nonstoichiometry in an iron garnet family of materials strengthens the Fe–O–Fe superexchange interaction, which, in turn, tends to increase the spin voltage correlated magnetic parameters. The analysis of experimental high temperature neutron diffraction data (over 27–450 °C) reveals the oxide ion nonstoichiometry and excess oxide ion transport pathways at moderate temperature 150 °C in the crystal lattices of studied garnet materials. Oxide ion nonstoichiometry, ionic transport, and electron hopping in crystal lattices cause a tremendous variation of electrical conductivity (10−11–10−2 S cm−1) over a moderate change of temperature (27–450 °C). The occurrence of electrical transport in the required thermal gradient over the garnet material in SSE can evoke the additional degrees of freedom in the usage of such materials at high temperatures. The present work provides a new outlook in terms of structure–property correlation for spin transport based materials.

Temporal Evolutions of Self-Organized Patterns Formed on the Water-Anode Surface of an Atmospheric Pressure Glow Discharge

Atmospheric pressure glow discharge above water anode has attracted much attention due to its extensive potential applications, where self-organized patterns can be formed. Usually, they are time-invariant under constant conditions. In this article, some peculiar time-dependent patterns are formed, among which concentric ring patterns like single, triple, quadruple, and quintuple rings are observed in water-anode discharge system for the first time. Accompanying the increasing complexity of patterns, results indicate that water conductivity evolves with time. Optical emission spectroscopy reveals that before reaching constant values, electron density decreases, while electron and gas temperatures increase as time elapses. Interestingly, the temporal variations of electric conductivity and plasma parameters are correlated with the evolution of patterns. Based on the phenomena mentioned above, the pattern evolution is qualitatively explained based on the Turing mechanism at last. We think these results will shed light on formation mechanism of patterns in atmospheric pressure glow discharge with water anode.

Effect of the variable electrical conductivity on the thermal stability of the MHD reactive squeezed fluid flow through a channel by a spectral collocation approach

The present work discusses the impact of the variable electrical conductivity on the thermal stability of the exothermic MHD reactive squeezed fluid flow through parallel plates. The governing nonlinear partial differential equations of the problem are remodel into ordinary differential equations and are solved using spectral collocation method. The obtained results are validated with those obtained using Runge–Kutta fourth–fifth order numerical algorithm (RK45) coupled with a shooting technique, and an excellent agreement is found. The impacts of emerging kinetic parameters, such as the activation energy, the reaction rate, the electrical conductivity exponent and the squeezed number, on the temperature profiles and thermal stability of the system are presented and discussed. It is revealed that positive squeezed number tends to delay the blow-up of the system, while both the negative squeezed number and the electrical conductivity exponent hasten thermal instability of the system.

Design and Simulation of a Compact Metal-Graphene Frequency Reconfigurable Microstrip Patch Antenna with FSS Superstrate for 5G Applications

Microstrip patch antennas are a very popular type of antenna due to their light weight, small size, and low manufacturing cost. However, they suffer from many disadvantages, such as poor gain and tuning difficulties, due to their narrow bandwidth. Graphene is a material that comprises a single layer of carbon atoms arranged in a honeycomb structure. One of the most useful features of graphene is its variable surface electrical conductivity, which can be altered by varying the DC voltage applied to the material. This method can be employed as a substitutional technique to construct tunable antennas. In this work, a compact tunable Rectangular Microstrip Patch Antenna (RMPA) is designed and modeled using Computer Simulation Technology (CST) Microwave Studio (MWS). The RMPA is optimized to work within two operating frequency bands of the fifth-generation communication system. The proposed antenna includes a copper radiating patch with two graphene layers inserted inside it, which are used for tuning. In order to enhance the parameters of the proposed antenna, such as gain and return loss, a frequency selective surface is utilized as a superstrate for 28 GHz band applications.

Rational Design of Space-Confined Mn-Based Heterostructures with Synergistic Interfacial Charge Transport and Structural Integrity for Lithium Storage.

Manganese-based compounds are expected to become promising candidates for lithium-ion battery anodes by virtue of their high theoretical specific capacity and low conversion potential. However, their application is hindered by their inferior electrical conductivity and drastic volume variations. In this work, a unique heterostructure composed of MnO and MnS spatially confined in pyrolytic carbon microspheres (MnO@MnS/C) was synthesized through an integrated solvothermal method, calcination, and low-temperature vulcanization technology. In this architecture, heterostructured MnO@MnS nanoparticles (∼10 nm) are uniformly embedded into the carbonaceous microsphere matrix to maintain the structural stability of the composite. Benefiting from the combination of structural and compositional features, the MnO@MnS/C enables abundance in electrochemically active sites, alleviated volumetric variation, a rich conductive network, and enhanced lithium-ion diffusion kinetics, thus yielding remarkable rate capability (1235 mAh·g-1 at 0.2 A·g-1 and 608 mAh·g-1 at 3.2 A·g-1) and exceptional cycling stability (522 mAh·g-1 after 2000 cycles at 3.0 A·g-1) as a competitive anode material for lithium-ion batteries. Density functional theory calculations unveil that the heterostructure promotes the transfer of electrons with improved conductivity and also accelerates the migration of lithium ions with reduced polarization resistance. This combined with the enhancement brought by spatial confinement endows the MnO@MnS/C with remarkable lithium storage performance.

Geochemical investigation of electrical conductivity and electrical double layer based wettability alteration during engineered water injection in carbonates

The injection of engineered water to increase the oil recovery from carbonates is increasingly becoming popular due to its reduced environmental impact and low cost of operation. However, the related variation in electric properties of rock and fluid with this technique is still ambiguous and needs thorough investigation. This study explores the variation in electrical conductivity, ion mobility, electrical double layer thickness, and the related oil recovery with the change in water composition from a geochemical perspective. In this study, we implemented an improved wettability alteration model based on the variation in electrical conductivity with a Matlab-IPhreeqc coupled simulator, to model the electrical conductivity, ion mobility, and electrical double layer (EDL) thickness. The variation in concentration of the ionic species obtained from the geochemical model is used to determine the electrical conductivity. This electrical conductivity-based wettability modification is dynamically simulated in the transport model. The model is validated with experimental coreflood data conducted on carbonates by simulating the electrical conductivity measurements reported in the literature. From the findings, it is evident that the formation temperature, sulfate concentration, and dilution of injected seawater has a noticeable effect on electrical conductivity during engineered water injection. It is important to mention that the EDL thickness is the main parameter affected by the change in electrical conductivity. In consequence, it is suggested to inject high-temperature water in carbonate reservoirs because it will increase ion mobility. This increase in ion mobility will enhance the EDL thickness and water film will become stabilized. Moreover, seawater dilution decreases electrical conductivity while spiking of sulfate concentration increases the activity of sulfate ions. However, the concentration of sulfate ions must be controlled as a wettability alteration agent, as it can cause the formation and precipitation of calcium sulfate. Furthermore, the variation in electrical conductivity and EDL thickness caused by the injection of seawater and diluted seawater increased the recovery of oil by approximately 16–21% in the selected case study.

Biostimulatory Action of a Plant-Derived Protein Hydrolysate on Morphological Traits, Photosynthetic Parameters, and Mineral Composition of Two Basil Cultivars Grown Hydroponically under Variable Electrical Conductivity

Hydroponics is a viable alternative to open field cultivation for year-round vegetable production in urban areas. However, the total dependence on external chemical inputs (fertilizers) makes these systems often less environmentally sustainable. In this perspective, the use of biostimulants could represent a valuable and eco-friendly tool to limit the excessive use of fertilizers without a negative impact on the yield. To this end, our work aimed to evaluate the productive and physiological response of two cultivars of ‘Genovese’ basil (Eleonora and Italiano Classico) for the industrial production of “pesto” grown for 22 days in two nutrient solutions with different electrical conductivity (1 and 2 dS m−1) and the application of two doses of protein hydrolysates (0.15- and 0.30-mL L−1 of Trainer® in the nutrient solution). The mineral profile was evaluated by ion chromatography coupled with a conductivity detector, while pigments were evaluated by UV-Vis spectrophotometry. Generally, the nutrient solution concentration did not significantly affect the fresh yield of the two cultivars tested. On the contrary, the use of the maximum dose of biostimulant (BT2 = 0.30 mL L−1 of nutrient solution) increased fresh yield, leaf area, and ACO2 by 20.7, 27.5, and 17.6%, respectively, compared with the control. Using the lowest dose of biostimulant (BT1 = 0.15 mL L−1 of the nutrient solution) reduced nitrate by 6.6% compared with the control. The results obtained showed that basil cultivation in a floating raft system combined with biostimulant in the nutrient solution could be an excellent solution to improve productivity, reduce nitrate, and cut fertilizer costs.

Structural, dielectric and gas sensing properties of gadolinium (Gd3+) substituted zinc-manganese nanoferrites

Gadolinium (Gd3+) substituted zinc manganese ferrite nanoparticles with nominal compositions Zn0.7Mn0.3GdxFe2-xO4 (where x = 0.000; 0.025; 0.050; 0.075; 0.100) were successfully synthetized using co-precipitation method. The synthetized powders were calcined at 500 °C and furthermore pressed into pellets and thermally treated at 650 °C for a second time to obtain a more compact material. For the 500 ℃ thermal treated samples, X-ray analysis revealed the formation of pure spinel ferrite phase, meanwhile for the 650 ℃ thermal treated samples secondary phases appear which indicate that some of Gd3+ ions aren’t able to remain in the structure of ferrite. The morphology of samples was investigated using scanning electron microscopy (SEM) and the images show agglomerated spherical nanoparticles within 20–30 nm size range. The magnetization curves recorded in ±10 kOe range indicate a superparamagnetic behavior of the synthetized ferrite samples. At low frequencies, the Gd3+ substituted ferrite samples corresponding to x = 0.050, 0.075 and 0.100 exhibit a resonant behavior of the dielectric losses dependence, while at high frequencies the lowest value was found for the sample with x = 0.025. The introduction of Gd3+ ions in the ferrite structure leads to a non-monotonous variation of AC electrical conductivity, which decrease from 2.55 x10−6 S/m to 3 x10−7 S/m. The ferrite samples have shown a good and reproducible response to the saturated acetone vapors and the highest sensitivity value (53%) was obtained for Zn0.7Mn0.3Gd0.025Fe1.9O4 ferrite sample. The response and recovery time varies between 36 and 56 s, respectively 80–116 s and both of these are independent of Gd3+ content.

Application of MLR-PRN model for estimation of arsenic concentration in drinking water: a case study for İzmir City

ABSTRACT Arsenic in drinking water can have serious adverse health effects depending on consumption. This study includes the comparison of two neural networks, Pattern Recognition Network (PRN) and Cascade Forward Neural Network (CFNN), that uses chloride, pH, and electrical conductivity variables at their inputs for estimation of arsenic in drinking water at the water distribution stations in İzmir. The data set consists of arsenic, electrical conductivity, iron, aluminum, pH, and chloride chemical variables, measured every two weeks (average) and taken from 16 water distribution points. Multiple linear regression (MLR) analysis showed that electrical conductivity is the most significant variable for arsenic estimation. The MAE (Mean Absolute Error), NSE (Nash-Sutcliffe Efficiency), IA (Index of Agreement), and R2 (coefficient of determination) values obtained with the PRN model were 0.653, 0.789, 0.944, and 0.802, respectively. These results showed that arsenic concentration in drinking water could be estimated using chloride, pH, and electrical conductivity.

Effect of Different Fertilizations on the Plant-Available Nitrogen in Soil Profile (0-100 cm): A Study on Chinese Cabbage.

The aim of this study is to analyze the variations in the plant-available nitrogen (PAN) concentrations in the soil profile. Different fertilizers were applied for Chinese cabbage plantation (CCP) in the experimental fields of the Shunyi region. The treatments used for the comparative analysis are (i) no fertilizer and plantation (NVP), (ii) no fertilizer with CCP (CTP), (iii) fertilization as urea (URP), and (iv) potassium nitrate (KNP) and chicken manure (CMP) with CCP. It was concluded that the yield was significantly high in URP, CMP, and KNP as compared to CTP. In URP, maximum PAN in soil layers 0–60 cm was recorded during crop production and in 60–100 cm after harvesting as compared to other treatments. Significant variations in soil pH and electrical conductivity (EC) for the soil profile (0–100 cm) from the initial values with respect to time and treatments were observed. CMP showed maximum ammonium in the upper layers of 0–60 cm throughout the season, whereas minimum PAN was observed in NVP but increased in lower layers of 60–100 cm. In general, all fertilizers raised the PAN below the soil 60–100 cm which indicates their potential for nitrate leaching (NL).