Resistance Values Research Articles

Associations of serum D-dimer and glycosylated hemoglobin levels with third-trimester fetal growth restriction in gestational diabetes mellitus

BACKGROUND Gestational diabetes mellitus (GDM) is a special type of diabetes that commonly occurs in women during pregnancy and involves impaired glucose tolerance and abnormal glucose metabolism; GDM is diagnosed for the first time during pregnancy and can affect fetal growth and development. AIM To investigate the associations of serum D-dimer (D-D) and glycosylated hemoglobin (HbA1c) levels with third-trimester fetal growth restriction (FGR) in GDM patients. METHODS The clinical data of 164 pregnant women who were diagnosed with GDM and delivered at the Obstetrics and Gynecology Hospital of Fudan University from January 2021 to January 2023 were analyzed retrospectively. Among these women, 63 whose fetuses had FGR were included in the FGR group, and 101 women whose fetuses had normal body weights were included in the normal body weight group (normal group). Fasting venous blood samples were collected from the elbow at 28-30 wk gestation and 1-3 d before delivery to measure serum D-D and HbA1c levels for comparative analysis. The diagnostic value of serum D-D and HbA1c levels for FGR was evaluated by receiver operating characteristic analysis, and the influencing factors of third-trimester FGR in GDM patients were analyzed by logistic regression. RESULTS Serum fasting blood glucose, fasting insulin, D-D and HbA1c levels were significantly greater in the FGR group than in the normal group, while the homeostasis model assessment of insulin resistance values were lower (P < 0.05). Regarding the diagnosis of FGR based on serum D-D and HbA1c levels, the areas under the curves (AUCs) were 0.826 and 0.848, the cutoff values were 3.04 mg/L and 5.80%, the sensitivities were 81.0% and 79.4%, and the specificities were 88.1% and 87.1%, respectively. The AUC of serum D-D plus HbA1c levels for diagnosing FGR was 0.928, and the sensitivity and specificity were 84.1% and 91.1%, respectively. High D-D and HbA1c levels were risk factors for third-trimester FGR in GDM patients (P < 0.05). CONCLUSION D-D and HbA1c levels can indicate the occurrence of FGR in GDM patients in the third trimester of pregnancy to some extent, and their combination can be used as an important index for the early prediction of FGR.

Fracture resistance of endodontically treated maxillary premolars using indirect and direct composite onlays: A comparative study

ABSTRACT Aim: To evaluate and compare the fracture resistance of endodontically treated maxillary teeth using the same material as indirect and direct composite onlays and their modes of fracture. Materials and Methods: Ninety maxillary premolars were divided into six groups (n = 15) out of which 15 teeth were kept intact (negative control, Group 1). In the remaining 75 teeth, endodontic treatment was done and standardized mesio-occlusal-distal cavities were prepared. Fifteen teeth were kept unrestored (positive control, Group 2). The rest of the teeth were divided according to the type of restorations and the restorative material; Group 3: Ceram X sphereTEC™ one direct composite onlay, Group 4: Ceram X sphereTEC™ one indirect composite onlay, Group 5: Filtek Z 350 XT direct composite onlay, and Group 6: Filtek Z 350 XT indirect composite onlay. All the specimens were subjected to thermocycling and cyclic loading. The fracture resistance test was performed with the help of a universal testing machine and their modes of fracture were evaluated. Results: Mean fracture resistance values in the decreasing order are as: 1487.33N for Group 6, 1104.57N for Group 4, 933.87N for Group 1, 799.13N for Group 5, and 688.73N for Group 3, 265.23N for Group 2. Mean fracture resistance of Groups 6 and 4 was found to be significantly higher than Groups 1, 2, 3, and 5. Furthermore, there was a significant difference between Groups 1 and 3. Groups 1, 3, 4, 5, and 6 showed more number of favorable/restorable fractures, whereas Group 2 showed more unfavorable/unrestorable fracture. Conclusion: The indirect technique of fabrication of onlays improved the fracture resistance of endodontically treated maxillary premolars.

Investigation of magnetic exchange interactions in Cr-doped Ca0.5Sr0.5RuO3

The value of Curie temperature (T C) and resistivity for Ca0.5Sr0.5Ru1−xCrxO3 are found to increase with increase in x from 0 to 0.1. The T C increases from 38 K to 107 K. In this work, we investigate the increment using spin polarised density functional theory. The compounds exhibit Griffiths phase. Our results show that to understand the behaviour of the increase in T C , it is important to consider not only the competing super exchange and super–super exchange interactions between Ru/Cr–Ru/Cr ion pairs but also the increment in the value of the magnetic moment due to the localized character of the dopant (Cr) ion. Our results suggest that the increased resistivity with Cr doping could be due to increased scattering rate and strong on-site coulomb repulsion due to Cr doping. It is also important to note that the behaviour of T C with the Ru–O–Ru bond angle is not in line with the functional form reported for ferrites, chromites and some ferromagnetic oxides. We believe that our results will be helpful in further exploring the origin of magnetism and transport on Cr doping in perovskite ruthenates.

Effect of Sm dopant on electrocatalytic activity of AgNbO3 perovskite fabricated by sonication method for Oxygen Evaluation Reaction (OER)

Excessive reliance on fossil fuels causes a variety of difficulties and the use of efficient electrocatalysts material has exhibited significant attention for high electrocatalytic activity. Most transition metal oxide materials performance can be enhanced by the incorporation of metals for OER activity. This work presents the synthesis of samarium (Sm) doped silver niobium oxide (AgNbO3) was achieved using sonication techniques. An electrocatalyst, Sm-doped AgNbO3, has shown promising results for oxygen evolution reaction (OER) in alkaline medium with a significant increase in active sites, enhanced electrical conductivity and improved stability. The Sm-doped AgNbO3 electrocatalyst exhibits overpotential of 203 mV and Tafel slope of 35.22 mV dec−1 for OER activity at current densities of 10 mA cm−2. By utilizing, electrochemical surface area (ECSA), the Sm-doped AgNbO3 electrocatalyst exhibited higher ECSA values of 1009 cm−2 with a higher roughness factor of 2008.60. Further, observations of low charge transfer resistance value (Rct = 0.17 Ω) along with a durability of 50 h, indicate that this material is highly efficient and long-lasting as an electrocatalyst for energy conversion systems.

Achieving optimal balance: tuning electrical and optical characteristics of carbon electrodes for emerging photovoltaics.

Transparent and conductive electrodes (TCEs) are essential for various optoelectronic and photovoltaic applications, but they often require expensive and complex fabrication methods. In this paper, a unique low-cost, eco-friendly, and scalable method of fabricating TCEs using spray-coated carbon ink is investigated. Firstly the carbon particles used for this process underwent a size reduction from 20 microns to 0.96 microns via ball milling. Then ink was prepared by mixing graphite powder (for conductivity), ethyl cellulose (for viscosity), and toluene (for solubility) with different weight-per-volume ratios (w/v) of 5%, 10%, and 15%. The TCEs were fabricated by spray coating the ink onto glass substrates using an airbrush. The sheet resistance (Ω sq-1) and transparency (%) of the TCEs were measured by a digital multimeter (DMM) probe method and a UV-vis spectrophotometer, respectively. The sheet resistance of the TCEs decreased linearly from 60 to 20 Ω sq-1, while the transparency decreased exponentially from 37.18% to 18.88% as the ink concentration increased from 5% to 15% w/v. This paper also reports the reflectance and absorbance values for each ink concentration. The results demonstrate that spray-coated carbon ink TCEs achieve sheet resistance and transparency values of 20 Ω sq-1 and 18.88%, respectively, with low-cost and eco-friendly materials and methods, which are desirable for optoelectronic and photovoltaic applications. These TCEs can play an important role as electrodes in semi-transparent perovskite cells enhancing their stability and overall efficiency.

An analysis of the impact of nanofluids on the cooling effectiveness of pin and perforated heat sinks

In the presented numerical study, the effect of the use of mono and hybrid (CuO/Water at 2% volume concentration and CuO + Fe/Water (1% CuO + 1% Fe)) type nanofluid in heat sinks designed in new geometric structures used to increase the processor cooling performance was investigated. The geometries used are circular, triangular, square, hexagonal, square, and hexagonal, and their perforated structures and their effects on a total of eight geometries were analyzed. In addition to these, the rate of improving the temperature distribution and heat transfer in the heat sink, i.e., the Performance Evaluation Criterion (PEC), was also examined. According to the results obtained, the lowest thermal resistance value is seen in the circular cross-section with Rth = 0.289 K/W, while the highest thermal, i.e., cooling performance is seen in the triangular perforated structure with Rth = 0.63 K/W and at the lowest pressure inlet condition. In terms of temperature distribution, the most uniform distribution was obtained between 311.82 and 308.98 K in the circular section. The most interesting result in terms of the results was the PEC = 1.4 for the triangular hole structure in the heat transfer improvement performance. The main reason for this is that the range of the temperature distribution shown is very high (319–311.5K).

Reliable Lift‐Off Patterning of Graphene Dispersions for Humidity Sensors

AbstractDispersion‐based graphene materials are promising candidates for various sensing applications. They offer the advantage of relatively simple and fast deposition via spin‐coating, Langmuir–Blodgett deposition, or inkjet printing. Film uniformity and reproducibility remain challenging in all of these deposition methods. Here, a scalable structuring method is demonstrated, characterized, and successfully applied for graphene dispersions. The method is based on a standard lift‐off process, is simple to implement, and increases the film uniformity of graphene devices. It is also compatible with standard semiconductor manufacturing methods. Two different graphene dispersions are investigated via Raman spectroscopy and Atomic Force Microscopy and observe no degradation of the material properties by the structuring process. Furthermore, high uniformity of the structured patterns and homogeneous graphene flake distribution is achieved. Electrical characterizations show reproducible sheet resistance values correlating with material quantity and uniformity. Finally, repeatable humidity sensing is demonstrated with van der Pauw devices, with sensing limits of less than 1% relative humidity.

Photosensitive properties of Schottky type photodiodes prepared by spin coating of isoniazid Schiff base thin film on p-Si

In this study, a layer of isonicotinohydrazide and pyrene-based Schiff base (PyMIs) was formed on the front side of a p-Si semiconductor using the spin coating method, and an Al/PyMIs/p-Si/Al diode was fabricated. The I-V characteristics of the fabricated diode were measured under dark and from 20 to 100 mW/cm2 illumination intensities for both forward and reverse bias. Diode parameters, including saturation current (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${I}_{0}$$\\end{document}), ideality factor (n), and barrier height (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\varphi }_{b}$$\\end{document}) were investigated for all measurements based on thermionic emission theory. The values n changed from 2.51 to 2.05, and the \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\varphi }_{b}$$\\end{document} changed from 0.77 eV to 0.86 eV as light intensity increased from dark to 100 mW/cm2. The series resistance (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${R}_{s}$$\\end{document}) values of the diode were investigated using the modified Norde’s function and Cheung’s functions. An analysis of the forward \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$log\\left( I \\right) - log\\left( V \\right)$$\\end{document} plot of Al/PyMIs/p-Si (MOmS)-type diode specified the carrier transport domination by ohmic conduction in the lower bias regions, by the space-charge-limited current (SCLC) at medium bias regions and the trap-charge limit current (TCLC) transport mechanism at higher bias regions. The fabricated diode exhibited typical photodiode behavior with reverse current values increasing from 9.13 × 10− 6 A to 1.05 × 10− 4 A, respectively. Furthermore, \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$I-V$$\\end{document} characteristics illuminated from 20 to 100 mW/cm2 were also studied, and they indicated that the Al/PyMIs/p-Si diode could operate in a photovoltaic regime.

Electrical conductivity enhancement of rGO-MoS2 composite electrode for inverted PSC by parameter optimization

Carbon-based electrodes are widely used in photovoltaic, metal-ion batteries, supercapacitors, and sensors due to their low ohmic resistance and ability to integrate modifiers. Reduced graphene oxide (rGO) represents a promising alternative to graphite in carbon-based electrodes because of its high electrical conductivity, large surface area, and robust mechanical properties. This study aimed to optimize the fabrication parameters of rGO-MoS2 composite electrodes prepared via a one-pot hydrothermal method, focusing on maximizing their electrical conductivity for potential electronic applications. Taguchi analysis was employed to evaluate the impact of three key factors: rGO-MoS2 mixing ratio, annealing temperature, and annealing time. The novelty of this work lies in the systematic optimization approach using the Taguchi method, which allowed for the identification of the most significant factors and their optimal levels. The optimal combination was found to be a 1:1 ratio, 75 °C annealing temperature, and 15-min annealing time, resulting in an impressive electrical conductivity of 11 800 S m⁻1. This optimized rGO-MoS2 composite electrode exhibited an approximate 11 % reduction in sheet resistance compared to the unoptimized composite. Furthermore, all samples show an improvement in sheet resistance values compared to pure rGO and MoS2, which were 82.5 Ω/sq and 48.9 Ω/sq. Numerical simulations further revealed a 13.23 % improvement in device performance when the optimized rGO-MoS2 composite was implemented as the top electrode in an inverted perovskite solar cell, demonstrating the significant potential of this material for various electronic applications.

Geophysical and physicochemical assessment of groundwater and the implication on the public health in rural and semi-urban areas of Northern Nigeria

Groundwater resource plays a central role in every sector of life globally. Unfortunately, the roles of groundwater are often unappreciated in many parts of the world, especially in developing nations. The paper applied a combined geo-electrical method and hydrochemical analysis alongside physical surveys to investigate aquifer promising zones, the quality and the source of water supply in the selected regions. The geo-electric resistivity data were used to select the most aquifer-promising zone for groundwater development with a key interest in groundwater potential and aquifer overburden protective capacity overlying the water-bearing unit. Seventeen (17) vertical electrical sounding (VES) acquired in four regions reveals that the regional weathered/fractured unit which constitutes the aquifer unity extends from 13.4 m to 41.3 m in depth with the subsurface resistivity value varying between 53 Ωm–1013 Ωm in terms of resistivity values. The overburdened thickness (protective soil layers) stretches from 2.5 m to 13 m with a resistive layer of resistivity values ranging from 111 Ωm to 2877 Ωm, which could provide high aquifer protective cover for the regional groundwater systems. The computed aquifer transmissivity and hydraulic conductivity range from 0.54 m2/h\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${m}^{2}/h$$\\end{document}–15.85 m2/h\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${m}^{2}/h$$\\end{document}, and 0.95 m/day–9.19 m/day, respectively. The estimated average longitudinal conductance (0.2 moh) reveals that the regional groundwater systems are moderately protective against surface contaminants. In addition, the physicochemical water analysis was examined, which exposes the level of heavy metals (HMs) compositions in the regional groundwater systems and the possible public health risks compared to WHO permissible drinking water limits. The sample water from the Rivers had the highest concentration of HMs (0.089 mg/I–2.012 mg/l), followed by the hand-dug wells (HWDs) (0.033 mg/l–1.555 mg/l) and the lowest in the borehole (0.011 mg/l–0.511 mg/l). In contrast, the borehole water sample shows a moderation where the HMs presence falls within the WHO standard for drinking water. The outcomes of the study show that 63% of the investigated region consumed water with a high concentration of HMs above the WHO permissible standard allowance for drinking water, while only 37% took water that falls within the WHO permissible standard. In conclusion, the study showed significant impacts of anthropogenic activities on the regional water quality, which provides vital information about the regional groundwater systems and the quality of water supply for adequate groundwater development and sustainability.

Exploring Olive Pit Powder as a Filler for Enhanced Thermal Insulation in Epoxy Mortars to Increase Sustainability in Building Construction

This article explores the use of olive pit powder (OPP) as a promising resource for enhancing the thermal insulation properties of epoxy mortars. A comprehensive analysis of the chemical and physical characteristics of OPP was conducted, employing analytical techniques including scanning electron microscopy (SEM), thermogravimetric analysis and emitted gas analysis (TG-MS-EGA), and proximal analysis. Experimental samples of epoxy grout were prepared by using different proportions of a conventional inorganic filler, quartz powder, and OPP within an epoxy mortar matrix. As the percentage of OPP in the formulation increased, the microstructure of the samples gradually became more porous and less compact. Consequently, there was a decrease in density with the increase in OPP content. The 28-day compressive strength decreased from 46 MPa to 12.8 MPa, respectively, in the samples containing only quartz (Sample E) and only OPP (Sample A) as a filler. Similarly, flexural strength decreased from 35.2 to 5.3 MPa. The thermal conductivity decreased from 0.3 W/mK in Sample E to 0.11 in Sample A. Therefore, increasing the %wt of OPP improved insulating properties while reducing the mechanical resistance values. This study highlights the potential of OPP as an environmentally friendly and thermally efficient filler for epoxy mortars, thereby promoting sustainable construction practices.

Rust Prevention Property of a New Organic Inhibitor under Different Conditions.

The corrosion resistance properties of a new type of environmentally-friendly organic inhibitor containing amino ketone molecules are presented in this paper. To evaluate the prevention effect of the inhibitor on corrosion of reinforcement, the electrochemical characteristics of steels in the simulated concrete pore solution (SPS) were investigated under varied conditions of the relevant parameters, including concentrations of the inhibitor and NaCl, pH value, and temperature. The inhibition efficiency of the material was characterized through electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, and the weight loss of steels. The results reveal a significant improvement in the corrosion resistance of steels with the inhibitor. A maximum resistance value of 89.07% was achieved at an inhibitor concentration of 4%. Moreover, the new organic inhibitor exhibited good corrosion protection capability for steels under different NaCl concentrations. Its inhibition efficiency was determined to be 65.62, 80.06, and 66.30% at NaCl concentrations of 2, 3.5 and 5%, respectively. On the other hand, it was found that an alkaline environment was favorable for an enhanced corrosion prevention effect, and an optimal pH value of 11.3 was observed in this work. Besides, the inhibition efficiencies at different temperatures showed a trend of 25 > 35 > 40 > 20 > 30 °C, with a maximum value of 81.32% at 25 °C. The above results suggest that the new organic material has high potential to be used as an eco-friendly and long-term durable inhibitor for steel corrosion prevention under complex conditions.

Lithospheric electrical structure of the Alxa Block, NW China, southern central Asian Orogenic Belt, revealed by 2D inversion of magnetotelluric data

The Alxa Block, situated between the Tarim and North China cratons, is essential to understand the tectonics of northwest China. It has undergone several tectonic cycles, including rifting from northern Gondwana in Neoproterozoic, subduction-accretion of the Paleo-Asian Ocean during Paleozoic, and intracontinental deformation in Mesozoic. Broadband magnetotelluric data covering a frequency range of 320 Hz to ∼ 10000 s was collected along two NW-SE trending lines across major tectonic units of the Alxa region to investigate the deep structures of the Alxa Block. By applying the nonlinear conjugate gradient (NLCG) inversion approach, two-dimensional (2D) electrical resistivity models were obtained at a 100 km depth. These findings indicate that the Zhusileng-Hangwula and Zongnaishan-Shalazhashan tectonic zones have high resistivity in their lower crust and upper mantle, with an overall layered high-low–high resistivity pattern. The upper crust of the Nuru-Langshan tectonic zone is primarily characterized by high resistivity values, whereas the lower crust and upper mantle contain a large-scale low-resistivity (or conductive) zone that is likely the result of partial melting. The large-scale Early–Middle Jurassic nappe structures may be connected to sub-horizontal low-resistivity anomalies in the shallow strata, which are located up to 20 km below the Yagan and Zhusileng–Hangwula tectonic zones. Below the Engger Us fault, two low-resistivity bands are interpreted as the product of bidirectional subduction and final closure of the Paleo-Asian Ocean. The Alxa Block may have subducted southwards beneath the Ordos Block, as suggested by a clear low-resistivity anomaly between the two blocks. Furthermore, partial melting may have happened for high-conductivity bodies in the upper mantle based on the modified Archie formula’s evaluation of their melting degree.

98 Adding parasite resistance to the breeding objective in hair sheep

Abstract Economic selection indexes provide the best method to achieve genetic gain for multiple traits simultaneously. Hair sheep enterprises, particularly in environments with substantial gastrointestinal nematode challenge, may benefit from incorporating parasite resistance in a selection index. However, obtaining the relative economic value (REV) for parasite resistance is challenging; information on its impact on productivity is incomplete, as are the costs of treatment given anthelmintic resistance. The National Sheep Improvement Program (NSIP) currently provides producers with an index designed to increase total weight of lamb weaned per ewe lambing (TW). Our objective was to assess the effects of including fecal egg count, an indicator of parasite resistance, as an additional goal trait. Including the benchmark scenario with TW as its sole objective, 10 indexes were constructed using standard index theory. Post-weaning fecal egg count (PFEC) was added to this breeding objective with a REV of -1 and the REV for TW was varied from +1 to +5 at +0.5 increments. Weaning weight, number of lambs born and weaned, and PFEC were the selection criteria, modelled as either phenotypes or estimated breeding values (EBV). Phenotypes and EBV were simulated for 1,000 lambs by Cholesky decomposition and used to generate index scores. Ten replicates were run and the top 3% of males and 26% of females were retained on index scores. Annual responses in the goal traits were estimated. Responses in PFEC were expressed as a percentage, assuming a mean PFEC of 2,089 eggs/g as in NSIP. Concordances with those selected in the benchmark scenario were determined. Using EBV as selection criteria, TW increased by 1.7 kg/yr in the benchmark scenario (Table 1). However, unfavorably, PFEC increased by 2.3%/yr. When phenotypic criteria were used, TW increased by 0.5 kg/yr, and PFEC by 0.3%/yr. Once added to the breeding objective, PFEC decreased regardless of the REV of TW. However, response in TW also reduced, although less so as its REV increased. With EBV as the criteria, the REV of +3 for TW appeared preferable: PFEC reduced by 7.1%/yr with 98% of the response in TW retained. With phenotypic selection criteria, PFEC reduced by 5.2%/yr with 94% of the response in TW retained. With +3 REV for TW and EBV as the selection criteria, on average 65% and 82% of males and females, respectively, were chosen in common with the benchmark. When phenotypic criteria were used, those percentages were 60% and 80%, respectively. Implementing a more holistic index with REV of +3 for TW and -1 for PFEC would result in reasonable responses in both traits. However, producers will need to decide if reduced gains in TW is acceptable to improve parasite resistance in a hair sheep breeding program.

Determination of Clay and Sand Volume Using Vertical Electrical Sounding

This study presents the results of an electrical resistivity survey conducted in Agudama Epie, Yenagoa local government area, Bayelsa State, Nigeria. The primary objective of the survey was to estimate the volume of clay and sand within a rectangular land parcel measuring 100 m by 200m in the study area. The survey employed the Schlumberger electrode configuration and utilized nine vertical electrode sounding (VES) points.Data was collected using a Terrameter SAS 1000 and was processed using IPI2win software. The geophysical analysis revealed the presence of four distinct geoelectric layers across the study area, identified as layers 1 to 4 in the VES profiles. Layer 2, characterized by clay, exhibited an average thickness of 21.2 meters, while layer 3, consisting of sand, had an average thickness of 8.15 meters. The apparent resistivity values ranged from 8.45 to 79.43 ohm-meter to a depth of 10.14 meters for the clay layer and 8499.86 to 15013.11 ohm-meter to a depth of 33.5 meters for the sand layer. The study estimated a substantial presence of approximately 746,240 tonnes of clay and approximately 261,126 tonnes of sand in Agudama Epie. This discovery offers significant economic potential, including job creation, the establishment of small and medium-sized enterprises, and opportunities within the construction industry. The local extraction and processing of clay can drive economic growth and facilitate the production of concrete and building materials. Additionally, the availability of sand in the region can reduce transportation costs and stimulate local construction projects, thereby fostering economic activity and infrastructure development.

Enhanced Thermoelectric Performance of Na0.55CoO2 Ceramics Doped by Transition and Heavy Metal Oxides

Using the solid-state reactions method Na0.55(Co,M)O2 (M = Cr, Ni, Zn, W, and Bi) ceramics were prepared and their crystal structure, microstructure, electrophysical, thermophysical, and thermoelectric properties were studied. Doping of Na0.55CoO2 by transition or heavy metal oxides led to the increase in the grain size of ceramics, a decrease in electrical resistivity and thermal diffusivity values, and a sharp increase in the Seebeck coefficient, which resulted in essential enhancement of their thermoelectric properties. The largest power factor (1.04 mW/(m·K2) at 1073 K) and figure of merit (0.702 at 1073 K) among the studied samples possessed the Na0.55Co0.9Bi0.1O2 compound, which also demonstrated the highest values of the Seebeck coefficient (666 μV/K at 1073 K). The obtained results show that the doping of layered sodium cobaltite by different metal oxides allows for improving its stability, microstructure, and functional properties, which proves the effectiveness of the doping strategy for developing new thermoelectric oxides with enhanced thermoelectric performance.

Interpretasi Material Pada Rancang Bak Ukur Skala Laboratorium Dengan Pendekatan Konfigurasi Wenner, Wenner – Schlumberger dan Dipole-dipole

Geoelectric measurements have been carried out using multichannel ResistivityMeter (Geores) tools with Wenner, Wenner-Schlumberger, and Dipole-dipole Configuration approaches on the influence of materials arranged in a laboratory-scale measuring tub design with dimensions of 194x184x80 cm. The measured method is the variation in resistivity value against each trajectory of the material. The method used is the variation of resistivity values for each path of the material that has been arranged in a laboratory scale measuring design. Geoelectric measurements were carried out on 7 lines (5 line in the West-East direction and 2 line in the North-South direction). The spacing between the electrodes of each line is 10 cm with 16 electrodes in one line so that each line has a length of 160 cm or 1.6 m which corresponds to the length and width dimensions of a laboratory scale measuring design. The electrode arrangement parameters are constant with respect to changes in the configuration selected from the geores parameters during geoelectric measurements. The measurement results showed that the identified depth reached 31.2 cm. The low resistivity value category has an interval of 374-4,397 ohm.meters at a depth of 0-12.5 cm, which is the influence of building sand material containing water and soil, while the depth interval is 12.5 - 31.2 cm ohm.meters (material category that is influenced by 2 iron rods, tin tailings sand, granite, gravel) with resistivity values ranging from 12,378–67,498 ohm.meters. From experiments on the influence of the resistivity values of the three Wenner, Wenner-Schlumberger, and Dipole-dipole configurations, it was obtained that the smallest absolute error resistivity value in the Wenner configuration was 5.01% against the overall average absolute error resistivity value of 10.16%.

The Effects of Cl− and selected deoxidizers on the high temperature corrosion electrochemistry of alloy 690 in nuclear steam generator water

ABSTRACT The heat transfer tube in a steam generator serves as a critical heat exchange component in the primary and secondary loops of pressurized water reactor (PWR) nuclear power plants. The corrosion resistance of the heat transfer tube material directly influences the longevity of PWR nuclear power plants. This study investigated the electrochemical corrosion properties of 690 alloy (UNS N06690) in a simulated secondary water environment of PWR, focusing on different chloride ion concentrations and combinations of deoxidizers. The findings reveal a gradual decrease in the corrosion potential of 690 alloy, accompanied by an increase in self-corrosion current and a progressive reduction in the passivation range, ultimately leading to its disappearance as chloride ion concentration rises from 0 μg·L−1 to 500 μg·L−1. Moreover, the impedance value of the inner film exhibits a declining trend with increase of chloride ion concentration. Conversely, the resistance value of the outer film remains relatively stable while the size and spacing of oxide particles on the surface of the 690 alloy continuously increase. This observation suggests that chloride ions primarily influence the formation of the inner passivation film, which in turn determines the corrosion resistance of the 690 alloy. Notably, the performance of the 690 alloy is similar when the deoxidizer combination is ammonia(NH3)+erythorbic acid(ERA) or NH3+hydrazine(N2H4), demonstrating the ability to form a relatively complete passivation film and exhibit improved corrosion resistance compared to NH3+N-isopropyl hydroxylamine, additionally, when the deoxidizer combination is NH3+N2H4, the 690 alloy exhibits lower self-corrosion current density across different chloride ion concentrations, indicating enhanced corrosion resistance.

A Virtual Resistance Optimization Method Based on Hybrid Index in Low-voltage Microgrid

Introduction: The introduction of virtual resistance can effectively suppress the circulating current between micro-sources and improve power allocation in low-voltage microgrid, but it also causes the voltage deviation of micro-sources’ inverters. An optimization method of virtual resistance based on hybrid index is proposed in order to suppress circulating current and improve voltage deviation at the same time in this paper. The gradient descent method is used to design the virtual resistance optimization process, aiming at the optimization of hybrid index composed of circulating current and voltage deviation. The constraints are deduced with power quality requirements, capacity limitation and static stability, and then virtual resistance values are optimized. The effects of switching load and micro-source on the optimization results are analyzed through the simulation of low-voltage microgrid, and the simulation results show that the virtual resistance optimization method can significantly suppress circulating current while improving power quality. When distributed generators are connected to utility grid through inverters and feeders, differences in feeder parameters and inverter control strategies easily cause circulating current and uneven power distribution among micro-sources. The introduction of virtual resistance can effectively suppress the circulating current between micro-sources and improve power allocation in low-voltage microgrids, but it also causes the voltage deviation of micro-sources’ inverters. An optimization method of virtual resistance based on hybrid index is proposed in order to suppress circulating current and improve voltage deviation. Methods: The gradient descent method is used to design the virtual resistance optimization process, aiming at the optimization of hybrid index composed of circulating current and voltage deviation. The constraints are deduced with power quality requirements, capacity limitation and static stability, and then virtual resistance values are optimized. Results: In the simulation scenario of two micro-sources and three micro-sources, the virtual resistance obtained by the method proposed in this paper has more obvious improvement on the system operation index, and is not affected by the load type. Conclusion: The method of optimizing virtual resistance based on the hybrid index can achieve the effect of restraining circulating current and improving power sharing degree on the premise of guaranteeing power quality and satisfying system stability. The optimization of virtual resistance is affected by the number of feeders. It is necessary to re-optimize the virtual resistance after changing the number of feeders, but the process of switching micro-source and adjusting load does not affect the optimized resistance value.

VLF-EM data conversion into apparent resistivity using the Hilbert transform and its application for shallow fault investigation at Pinggirsari, Bandung Regency, Indonesia

This research presented the ability of the Hilbert transformation of The Very Low Frequency-Electromagnetic (VLF-EM) data to investigate the presence of faults. VLF-EM data was collected in the Pinggirsari village area, Arjasari District, Bandung Regency, West Java, Indonesia. Through the Hilbert transformation, the VLF-EM data was converted into apparent resistivity data and then inverted into a resistivity cross-section. For comparison, qualitative interpretation was also conducted using both the Fraser and the Karous-Hjelt filters. Interpretation results using both the Fraser and Karous-Hjelt filters indicate the presence of faults through tilt-angle curve peaks and apparent current density anomalies. The resistivity cross-section resulting from the Occam inversion of the apparent resistivity data, derived from the Hilbert transformation, accurately delineated fault positions. Resistivity changes around 700–800 m indicated fault proximity to a depth of approximately 150 m, with a good match to the geological map. Within a distance of 0–700 m, low resistivity values were associated with the Malabar tuff, while >700 m, higher resistivity values were associated with the Waringin-Bedil andesite. The Hilbert transform helps in clarifying VLF data interpretation for precise fault detection through resistivity parameters.