Areas Of High Resistance Research Articles

Resistance Reduction Scheme for Tower Grounding with Conductive Cement

The construction conditions of transmission lines are becoming more and more difficult. It is necessary to find new ways to reduce the grounding resistance of poles and towers at high soil resistivity and small construction area. Conductive cement samples with graphite, stainless steel fibers, and their mixtures as conductive phases materials were prepared, the resistivity, flexural strength and compressive strength were tested, compared and analyzed. The graphite and stainless steel fiber conductive cement with better comprehensive performance was selected out for tower grounding. The application schemes of conductive cement for tower grounding were designed and compared, the partial wrapping scheme was selected and its application methods under different soil resistivity was analyzed. The analysis results can provide theoretical basis and guidance for the application of conductive cement in transmission tower grounding, the feasibility of scheme is proved by the field application.

Electric Arc Recoil–A Novel Method for Reducing Lightning Strike Potential Difference for Transmission Line

Increasing arc pressure by tens of times with fine pouring tube, a positive shock wave by the pouring arc entering the closed space of the thin tube (electric arc recoil wave). The pressure of electric arc recoil wave is 8 to 23 times than that of the arc tube pouring wave. Since the recoil wave has more pressure than the arc tube pouring wave, and their directions are opposite, the tube poring arc is driven away from the tube channel by the recoil wave. The arc completely emptying and a large scale truncation to the electric arc are formed. Therefore, the truncation arc interrupts the lightning current, and recombusts to form a new tube pouring wave and backwash wave. The arc truncation and recombustion are caused by arc tube pouring and electric arc recoil alternately, and forming the intermittent lightning discharge, a large decrease in the amplitude of lightning current, steepness and discharge time. The results show that the amplitude of lightning current can reduce from 67.14 kA to 35.1 kA, and the lightning current steepness can decrease 77.3%. This attenuation method of lightning current amplitude could significantly reduce the lightning current flowing into the ground, the induced overvoltage and the ohm potential difference. Additionally, the problem of lightning strike step voltage in high soil specific resistivity areas and electromagnetic induced overvoltage can be solved by the method in this paper. The probability of original fault is reduced, and the operation reliability is enhanced. The method can lower the cost of ground network and improve the lightning protection performance.

Van der Waals Multiferroic Tunnel Junctions.

Multiferroic tunnel junctions (MFTJs) have aroused significant interest due to their functional properties useful for nonvolatile memory devices. So far, however, all of the existing MFTJs have been based on perovskite-oxide heterostructures limited by a relatively high resistance-area (RA) product unfavorable for practical applications. Here, using first-principles calculations, we explore spin-dependent transport properties of van der Waals (vdW) MFTJs which consist of two-dimensional (2D) ferromagnetic FenGeTe2 (n = 3, 4, 5) electrodes and 2D ferroelectric In2Se3 barrier layers. We demonstrate that such FemGeTe2/In2Se3/FenGeTe2 (m, n = 3, 4, 5; m ≠ n) MFTJs exhibit multiple nonvolatile resistance states associated with different polarization orientation of the ferroelectric In2Se3 layer and magnetization alignment of the two ferromagnetic FenGeTe2 layers. We find a remarkably low RA product (less than 1 Ω·μm2) which makes the proposed vdW MFTJs superior to the conventional MFTJs in terms of their promise for nonvolatile memory applications.

THE EFFECTS OF P-ALAXIN ON FERTILITY AND HEMATOLOGICAL PARAMETERS IN MALE ADULT WISTAR RATS

P-Alaxin, is an anti-malarial drug that is highly effective in treating malaria all forms of malarial infection including multi drug resistance malaria in areas of high resistance especially in Africa. It is composed of dihydroartemisinin and piperaquine phosphate. This study investigates the effects of therapeutic dose of P-alaxin on fertility and hematological indices in rats. Fifteen male adult Wistar rats weighing between 150 and 220g were divided into three consisting of 5 rats per group. Normal saline was administered to the control group while the test and recovery groups were given 15.4mg/kg body weight of P-Alaxin orally for three days. The recovery group was allowed to recover for three days from the drug's effect. The animals were anaesthetized using diethyl ether. Blood samples were collected through cardiac puncture. Oral administration of P-alaxin (15.4mg/kg body weight) for three days reduced (p<0.05) significantly the sperm motility, sperm count, viability and testosterone as well as the PCV, Hb, WBC and RBC when compared to the control and there was no significant change in values of pH of the tests rats' semen. Allowing the rats to recover from the effects of the drug resulted in gradual restoration of sperm parameters and hematological indices under investigation. From the study it can be safely concluded that oral administration of P-Alaxin caused reduction in the hematological and sperm parameters and serum testosterone and could reduce male Wistar rats' fertility and also lead to anemia in rats

Threadbare BUT Bonded—Weaving Stories and Experiences Into a Collective Quilt of Black Women’s Leadership

As black women leaders within the 21st century sharing our stories, reflections and contributions remain an area of high anxiety, reluctance and resistance. The fear of these contentions can elicit feelings of invisibility, voicelessness, rejection and reprisal. Black women’s experiences of leadership are, at times, visualised metaphorically as a single bare thread. A thread that manoeuvres and meanders aimlessly, not through choice, but by navigating their way through institutional systems. Their journeys are fuelled with micro aggressions, convoluted racial barriers and systemic obstacles placed within their paths while attempting to reach and sustain their leadership positions. In this research (Curtis, 2014; 2017), has sought to connect these threadbare yet bonded experiences by weaving their counter-narratives into a collective quilt. A quilt designed and developed to show their stories of leadership. This methodology displays their strengths and commands visibility while displaying vibrant, passionate social justice leadership within these symbolic colourful, tired and tangled yarns. Black women’s survival in leadership positions is often not one of centrality within the mainstream literature. These experiences are not commonly championed or celebrated by those who hold dominance within society. However, within this research, black women’s survival is one in which their resilience hangs solitary at times by a threadbare yarn. Using these threads to authenticate connectedness and weaving their journeys of leadership has utilised a bond and created an opportunity to share with other black women leaders their often isolated experiences. The research expands their expressive, creative liberation using the lens of Critical Race Theory to explore the women’s cultural identities as educational leaders. KEYWORDS: Social Justice Leadership, Critical Race Theory, Black feminism, Collective identity

Subsurface Resistivity Imaging of Nasudake (Chausudake) Volcano Determined from Time Domain Electromagnetic Survey (TDEM)

A time domain electromagnetic survey (TDEM method) was conducted to investigate the resistivity structure of the crater, fumarole, and hot spring area of the Nasudake (Chausudake) volcano. The findings of this survey are as follows: (1) Under the crater area, a thin low-resistivity layer (approximately 50 m) was found on the surface, and lens-shaped high-resistivity areas continued to a depth of 800 m below it. The lens-shaped high-resistivity areas are believed to correspond to a thermal volcanic gas region. (2) From the east-west direction survey line crossing the foot of the Nasudake, two or three horizontal resistivity layer structures, which are considered to be caused by the geological structure and surface water, were observed.

Risk factors for malaria infection prevalence and household vector density between mass distribution campaigns of long-lasting insecticidal nets in North-western Tanzania

BackgroundLong-lasting insecticidal nets (LLINs) are the most widely deployed vector control intervention in sub-Saharan Africa to prevent malaria. Recent reports indicate selection of pyrethroid insecticide resistance is widespread in mosquito vectors. This paper explores risk factors associated with malaria infection prevalence and vector density between mass distribution campaigns, changes in net coverage, and loss of protection in an area of high pyrethroid resistance in Northwest Tanzania.MethodsA cross sectional malaria survey of 3456 children was undertaken in 2014 in Muleba district, Kagera region west of Lake Victoria. Vector density was assessed using indoor light traps and outdoor tent traps. Anophelines were identified to species using PCR and tested for Plasmodium falciparum circumsporozoite protein. Logistic regression was used to identify household and environmental factors associated with malaria infection and regression binomial negative for vector density.ResultsLLIN use was 27.7%. Only 16.9% of households had sufficient nets to cover all sleeping places. Malaria infection was independently associated with access to LLINs (OR: 0.57; 95% CI 0.34–0.98). LLINs less than 2 years old were slightly more protective than older LLINs (53 vs 65% prevalence of infection); however, there was no evidence that LLINs in good condition (hole index < 65) were more protective than LLINs, which were more holed. Other risk factors for malaria infection were age, group, altitude and house construction quality. Independent risk factors for vector density were consistent with malaria outcomes and included altitude, wind, livestock, house quality, open eaves and LLIN usage. Indoor collections comprised 4.6% Anopheles funestus and 95.4% Anopheles gambiae of which 4.5% were Anopheles arabiensis and 93.5% were Anopheles gambiae sensu stricto.ConclusionThree years after the mass distribution campaign and despite top-ups, LLIN usage had declined considerably. While children living in households with access to LLINs were at lower risk of malaria, infection prevalence remained high even among users of LLINs in good condition. While effort should be made to maintain high coverage between campaigns, distribution of standard pyrethroid-only LLINs appears insufficient to prevent malaria transmission in this area of intense pyrethroid resistance.

Conductive 3D printing: resistivity dependence upon infill pattern and application to EMI shielding

Polymers filled with conductive carbon black allow for the 3D printing of electrically conductive samples. The resistivity of these 3D printed samples depends on both the microscopic parameters of the carbon black filler and also on the macroscopic arrangement of the extrudites that build up the 3D printed sample. To investigate this dependence, we characterize the resistivity of five different printing infill patterns and find that a cross-ply pattern, which has extrudites oriented both in the direction of current flow and perpendicular to the direction of current flow has a lower resistivity of $$0.229\,\Omega {\text{m}}$$ than the resistivity of $$0.458\,\Omega {\text{m}}$$ found for a uni-ply pattern with all extrudites oriented in the direction of current flow. A Monte Carlo simulation of a large network of variable resistors illustrates the feasibility that the lower resistivity of the cross-ply pattern is caused by cross-flow which diverts current around areas of high local resistance. The same type of 3D printed conductive samples are tested as electromagnetic shields at frequencies up to 3.0 GHz using a custom-designed flanged coaxial sample holder. The shielding effectiveness of three sample infill patterns and four sample infill densities is compared. Cross-ply and angle-ply samples show the most efficient shielding effectiveness (normalized to sample density) of $$17.5\,{\text{dB}}/{\text{g}}\,{\text{cm}}^{3}$$ at an infill density of 50% and would be the infill pattern of choice in an application constrained by weight or material.

Electrical Resistivity Tomography as a Support Tool for Physicochemical Properties Assessment of Near-Surface Waste Materials in a Mining Tailing Pond (El Gorguel, SE Spain)

The legacy of the mining industry has left a large number of tailing ponds in the Cartagena–La Unión mining district exposed to water and wind erosion, which causes serious environmental and health problems and requires remediation. Before applying any remediation technique, an intensive sampling of the materials infilling the pond is required to determine the geochemistry of the pond, which will condition the remediation process. However, sampling the large number of tailing ponds that compose the district could be expensive. Thus, the main objective of this study is to evaluate the usefulness of electrical resistivity tomography (ERT) as a non-invasive tool to provide an image of spatial subsurface resistivity distribution and its relation to the physicochemical composition of near-surface mine wastes. To achieve this objective, three short ERT profiles were conducted, and 12 samples in each profile were collected at different depths for its geochemical characterization. Several non-linear regression models were fitted to predict physicochemical properties and metal concentrations from electrical resistivity measures. As a result, a high resistivity area was depicted in the ERT profiles G2 and G3, while the low resistivity ERT profile G1 was also obtained in accordance with the site’s surficial characteristics. Relationships among low resistivity values and high salinity, clay content, high metal concentrations, and mobility were established. Specifically, calibrated models were obtained for electrical conductivity, particle sizes of 0.02–50 µm and 50–2000 µm, total Zn and Cd concentration, and bioavailable Ni, Cd, and Fe. The ERT technique was shown to be a useful tool for the approximation of the location and distribution of the highest ranges of fine particle sizes, moisture, and, to a lesser extent, metal accumulation in the near-surface waste materials.

Navigating paved paradise: Evaluating landscape permeability to movement for large mammals in two conservation priority landscapes in India

Human land use and activity results in the loss of habitat and biodiversity, and alters how animals move through landscapes. Spatially explicit information on where animal movement is affected at large spatial scales is crucial for prioritizing conservation efforts. We evaluated landscape permeability to movement in two conservation priority landscapes in India, the Western Ghats (WG) and Central India (CI). Using an agent-based model we simulated movement and dispersal of five wide-ranging species in WG (elephant, gaur, leopard, sambar and sloth bear) and four in CI (gaur, leopard, sambar and sloth bear). For each species we compared movement in the presence and absence of land-use land-cover, infrastructure and human population to identify areas where movement is impeded and reduced due to high-resistance features; unrestricted due to relatively low-resistance features; and increased and channelled due to surrounding high-resistance areas. In both landscapes, median movement was reduced. Human land-use, human population and high linear infrastructure density contribute the highest to impeded movement for all species. Natural areas constitute only 20–55% and 50–70% of unrestricted, increased and channelled movement areas in WG and CI respectively. This suggests that a large percentage of the landscape crucial for maintaining movement is not completely permeable. Such areas are often neglected in conservation planning. Our spatially explicit results help identify and prioritize areas where restoration or mitigation should be planned to improve permeability to movement for large mammals. Our approach can be used for other landscapes where data on large mammal movement is lacking.

Sustaining electrification service from photovoltaic power plants during backflow lightning overvoltages

Photovoltaic (PV) systems are subjected to lightning strikes that contribute to losing their sustainable electrification service. Furthermore, they are subjected to backflow lightning overvoltages due to the installation in high soil resistivity areas, however, such the study is not aforementioned well in the literature. Therefore, the analyses and reductions of backflow lightning overvoltages are investigated in this paper, considering a PV power plant as an example installed in Taif city, KSA. All PV plant components are modeled using high-frequency models, in which they are such as air-termination, grounding system, surge protective devices, PV string, inverters, underground cables, and power transformers. To decrease the lightning overvoltages in the PV power plant, a modified PV grounding system design is introduced and evaluated. The evaluation is performed considering step voltage profiles using COMSOL Multiphysics and backflow lightning overvoltage magnitudes at different points in PV plant using ATP/EMTP. The results provide the motivation of studying backflow lightning overvoltages in PV plants and evidence of the efficacy of the proposed grounding system design in reducing the overvoltage magnitudes.

Mineral Prospect Identification Using Inducedpolarization And Very Low Frequency-EM Methods At Sangon, Kalirejo Village, Kokap Sub-District, Kulonprogo Regency, Special Region Of Yogyakarta, Indonesia

A research of induced polarization and very low frequency method was carried out at Sangon Village, Kulonprogo to identify mineralization zone. The result of these methods were able to be used to support each other. Mineralization zone is shown by high resistivity and high hargeability area of induced polarization method, and is also shown by high electric current density area of very low frequency method. Interpretation of resistivity and chargeability model shows that mineralization zone is mostly located at the depth below 10 m from surface. On the other hand, interpretation of electric current density models at depth 10 m and 20 m show that mineralization zone is not well distributed respect to alteration zone, which is the character of low sulfidation epithermal type, mostly at north-south direction.

3D Numerical Modeling of Induced-Polarization Grounded Electrical-Source Airborne Transient Electromagnetic Response Based on the Fictitious Wave Field Methods

The grounded electrical-source airborne transient electromagnetic (GREATEM) system is widely used in mineral exploration. Meanwhile, the induced polarization (IP) effect, which indicates the polarizability of the earth, is often found. In this paper, the Maxwell equations in the frequency domain are transformed into fictitious wave domain, where Maxwell equations are solved by the time domain finite difference method. Then, an integral transformation method is used to convert the calculation results back to the time domain. A three-dimensional (3D) numerical simulation in a polarizable medium is presented. The accuracy of this method is proven by comparing it with the analytical solution and the existing method, and the calculation efficiency is increased five-fold. The simulation results show that the GREATEM system has a higher response amplitude in the conductive region, while IP effects cannot be identified in the conductive area. The GREATEM system has a higher response amplitude in the low-resistance region, but IP effects cannot be identified in the low-resistance area, and the detection of IP effects is more suitable for the high-resistance area. Therefore, it is necessary to improve the detection ability of the GREATEM system in the low-resistance area.

Is tailored therapy based on antibiotic susceptibility effective ? a multicenter, open-label, randomized trial.

An effective eradication therapy of Helicobacter pylori (H. pylori) should be used for the first time. In this study, we assessed whether tailored therapy based on antibiotic susceptibility testing is more effective than traditional therapy. We also evaluated the factors that cause treatment failure in high-resistance areas. For this multicenter trial, we recruited 467 H. pylori-positive patients. The patients were randomly assigned to receive tailored triple therapy (TATT), tailored bismuth-containing quadruple therapy (TABQT), or traditional bismuth-containing quadruple therapy (TRBQT). For the TATT and TABQT groups, antibiotic selection proceeded via susceptibility testing using an agar-dilution test. The patients in the TRBQT group were given amoxicillin, clarithromycin, esomeprazole, and bismuth. Successful eradication was defined as a negative 13C-urea breath test at least eight weeks after the treatment ended. Susceptibility testing was conducted using an agar-dilution test. The eradication rate was examined via intention-to-treat (ITT) and per-protocol (PP) analyses. The clarithromycin, levofloxacin, and metronidazole resistance rates were 26.12%, 28.69%, and 96.79%, respectively. Resistance against amoxicillin and furazolidone was rare. The eradication rates for TATT, TRBQT, and TABQT were 67.32%, 63.69%, and 85.99% in the ITT analysis (P 0.001) and 74.64%, 68.49%, and 91.22% in the PP analysis (P 0.001), respectively. The efficacy of TABQT was affected by clarithromycin resistance, and bismuth exerted a direct influence on TATT failure. TABQT was the most efficacious regimen for use in high-resistance regions, especially among clarithromycin-susceptible patients.

Outdoor photoluminescence imaging of solar panels by contactless switching: Technical considerations and applications

AbstractMonitoring the performance of solar modules in a photovoltaic system is critical in order to understand the health of the system. Existing methods for field inspection have limited capability of detecting various electronic defects that can, however, be identified with luminescence‐based methods. A contactless outdoor photoluminescence‐imaging based measurement method that uses the sun as the excitation source was presented in our earlier work. This paper extends our previous work and presents two unique applications to (a) identify and quantify local areas of high series resistance within the cells and (b) identify bypass diodes that have failed in open‐circuit. The paper also discusses specific technical considerations of this method. The main merit of this method is that it can be used when the module is under normal operation in the field, without requiring changing of the electrical wiring of the photovoltaic array.

Shortened treatment regimens versus the standard regimen for drug-sensitive pulmonary tuberculosis.

Shortened treatment regimens versus the standard regimen for drug-sensitive pulmonary tuberculosis.

Helicobacter pylori eradication regimens in an antibiotic high-resistance European area: A cost-effectiveness analysis.

Helicobacter pylori infection (Hpylori-I) affects more than half of the global population and consists an important burden to public health and healthcare expenditures, by contributing to many diseases' pathogenesis. This study aimed to evaluate the current nonbismuth quadruple eradication regimens in a high antibiotic resistance area, such as Greece, concerning their cost-effectiveness, especially during financial crisis period. Eight hundred and nine patients who received eradication treatment against Hpylori-I were included to evaluate five different regimens, using amoxicillin, clarithromycin, and metronidazole as antibiotics and one proton-pump inhibitor, based on their current eradication rates. Regimes compared 10-day concomitant use of (a) pantoprazole or (b) esomeprazole; 10-day sequential use of (c) pantoprazole or (d) esomeprazole; and 14-day hybrid using esomeprazole. Cost-effectiveness analysis ratio (CEAR) and incremental cost-effectiveness ratios were calculated taking into account all direct costs and cases who needed second-line treatment. Additionally, sensitivity analysis was performed to predict all potential combinations. Ten-day concomitant regimen with esomeprazole was characterized by the lowest CEAR (179.17€) followed by the same regimen using pantoprazole (183.27€). Hybrid regimen, although equivalent in eradication rates, was found to have higher CEAR (187.42€), whereas sequential regimens were not cost-effective (CEAR: 204.12€ and 216.02€ respectively). This is the first study evaluating the cost-effectiveness of Hpylori-I treatment regimens in a high clarithromycin-resistance (≈26.5%) European area, suggesting the 10-day concomitant regimen with generics using esomeprazole 40mg as the most appropriate one. National and regional guidelines should include cost-effectiveness in their statements, and further studies are required to clarify the necessity of a wide "test and treat" policy for Hpylori-I.

Porous geopolymers: processing routes and properties

Cellular ceramics constitute a specific class of materials containing a high level of porosity, greater than 60 vol%, which are characterized by the presence of three-dimensionally arranged open and/or closed cells. Because of their structure, cellular ceramics exhibit a unique combination of properties such as low density, low thermal conductivity, low thermal mass, high permeability, high thermal shock resistance and high specific surface area, making them essential for various engineering application. Nowadays, porous geopolymers have been the focus of promising research in the field of porous inorganic materials because of their unique combination of good thermal stability and excellent mechanical properties. An interesting technological feature is that their solidification kinetics is easily adjustable and thanks to ceramic-like structure they have significant structural stability at elevated temperatures. The processing methods used for the fabrication of porous geopolymers can be divided into various approaches. Many methods have been explored to synthesize reproducible porous sponges or foams from geopolymer systems, such as gaseous method, rapid solidification, foaming, freeze-casting and/or combination of them. Concerning the macro/micro-structure of cells, the processing can be strongly influenced by various characteristics as a chemical composition, rheological behaviour of the slurries, kinetics of pore formation and hardening behaviour. This study presents methods of processing and manufacturing approaches with respect to types of porous materials and experimental results in this field.

Dislocation reduction in AlInSb mid-infrared photodiodes grown on GaAs substrates

We investigated the electrical and optical properties of a highly mismatched AlInSb/GaAs photodiode sensor working in the mid-infrared range at room temperature. A substantial increase in the device performance was achieved by controlling the strain energy density in the dislocation filter layers and barrier layers to reduce the density of threading and interfacial dislocations, respectively. The resulting photodiode showed a high resistance-area product of 0.24 Ω cm2 and a peak detectivity of 2.2 × 109 cm Hz1/2 W–1 at 3.3 μm.

Enhanced performance of vertical-structured InGaN micro-pixelated light-emitting-diode array fabricated using an ion implantation process.

In this Letter, a new approach to fabricating a high-efficiency vertical-structured InGaN micro-pixelated light-emitting diode (μVLED) is presented. The high-resistivity selective areas are intentionally created in the n-GaN layer through a fluorine (F) ion-implantation process and then used as the electrical isolation regions for realizing a μVLED array consisting of 25×25 pixels with a diameter of 10μm. The results prove that the dual-energy F- ion implantations not only can improve the uniformity of carrier distribution but also can effectively prevent current from leaking along the etched sidewalls, which in turn realize a more efficient carrier injection into the mesa area. More notably, the current-handling capability and corresponding optical output power density of the μVLED array are substantially higher than those of conventional vertical-structured broad-area LEDs. A measured output light power density of the F- ion-implanted μVLED array reaches a maximum value of 43 W cm-2 at 3.06 kA cm-2, before power saturation. The improved luminescence performances of the μVLED array can be attributed to an effective ion-induced heat relaxation and associated lower junction temperature.