Local Earth Research Articles

MORTARS AND PLASTERS PRODUCED WITH EARTH-BASED SUSTAINABLE MIXES: A METHODOLOGY PROPOSAL FOR RECOVERY OF VERNACULAR ARCHITECTURE IN ROERO, PIEDMONT (ITALY)

Abstract. The work presented is the achievement of a master degree project, developed at Politecnico di Torino. The paper aims to provide standards for the formulation and mixing of earth-based mortars, for the rehabilitation of historic buildings of the Roero area, in Piemonte region. Roero presents a large architectural heritage, consisting mainly of fired or earth bricks rural and residential buildings, which was anciently protected using lime or earth-based plasters perfectly integrated with local landscape and environment colours appearance. In recent decades (and still to present days), vernacular plasters are frequently replaced by cement-based products, resulting hardly compatible with local bearing walls materials and landscape aesthetic features. While Roero traditional buildings plasters were produced using local earth and sands coming from streams, today, aggregates extraction in watercourses proximity is not allowed, or strictly regulated by rules and regional regulations. The paper presents a classification of the characteristics of different soils from Roero area, through different types of particle distribution size analysis and diffractometric tests, and propose a method for the production of local earth-based plasters stabilized with lime, making use of earth and rocks from local excavation sites, considered in Italy as secondary raw materials or special waste. Produced plasters compressive and bending strength have been tested, while their suitability for building maintenance and restoration, as their compatibility with Roero architecture and landscape, have been verified through spectrophotometric measures.

Derivation of Earth Geoid Model for Mosul City in Iraq

The quality and efficiency of geoid models have been developed rapidly to provide elevations instead of traditional surveying. The high cost and the long measurement time of surveying instrumentation cause an urgent need for deriving local Earth Geoid Model (EGM). Hundred control points are selected on the study area topographic map. The study area is located in Mosul city in Iraq. Multiple earth geoid models have been derived using different interpolation methods available in ArcGIS environment. The results of statistical analysis determine the best interpolation method. The percentage root mean square errors (RMSEs) for the adapted interpolation methods are 26.54 %, 28.43 %, 30.13 %, 34.79 %, 36.75 %, and 37.28 % in kriging, Inverse Distance Weighted (IDW), Trend, Natural Neighbor, Spline, and Topo To Raster, respectively. Kriging interpolation gives minimum standard deviation (2.226 m) and RMSE (2.654 m) so it is the preferable method. The results indicate that the geoid is departed from GPS Visualizer data by the mean value of minus (1.405 m) in the study area.

A Multiple 1D Earth Approach (M1DEA) to account for lateral viscosity variations in solutions of the sea level equation: An application for glacial isostatic adjustment by Antarctic deglaciation

The pseudo-spectral form of the sea level equation (SLE) requires the approximation of a radially-symmetric visco-elastic Earth. Thus, the resulting predictions of sea level change (SLC) and glacial isostatic adjustment (GIA) often ignore lateral variations in the Earth structure. Here, we assess the capabilities of a Multiple 1D Earth Approach (M1DEA) applied to large-scale ice load components with different Earth structures to account for these variations. In this approach the total SLC and GIA responses result from the superposition of individual responses from each load component, each computed globally assuming locally-appropriate 1D Earth structures. We apply the M1DEA to three separate regions (East Antarctica, West Antarctica, and outside Antarctica) to analyze uplift rates for a range of Earth structures and different ice loads at various distances. We find that the uplift response is mostly sensitive to the local Earth structure, which supports the usefulness of the M1DEA. However, stresses transmitted across rheological boundaries (e.g., producing peripheral bulges) present challenges for the M1DEA, but can be minimized under two conditions: (1) If the considered time period of ice loading for each component is consistent with the relaxation time of the local Earth structure. (2) If the load components can be subdivided according to the scale of the lateral variations in Earth structure. Overall, our results indicate that M1DEA could be a computationally much cheaper alternative to 3D finite element models, but further work is needed to quantify the relative accuracy of both methods for different resolutions, loads, and Earth structure variations.

Effect of temperature on insecticidal efficiency of local diatomaceous earth against stored-grain insects

Bu calisma, 2017 yilinda Kahramanmaras Sutcu Imam Universitesi’nin Entomoloji Laboratuvari’nda Turkiye’nin farkli bolgelerinden elde edilen yerel diatom topraginin depolanmis tahil zararlisi, Pirinc biti, Sitophilus oryzae (L, 1763) (Coleoptera: Curculionidae) , Kirma un biti, Tribolium confusum Du Val., 1863 (Coleoptera: Tenebrionidae) ve Ekin kambur biti Rhyzopertha dominica (F., 1792 ) (Coleoptera: Bostrichidae) ’ne karsi insektisidal etkinligi uzerine sicakligin etkisini belirlemek icin yurutulmustur. Bu amacla bugday uzerinde uc farkli sicakliklarda (20, 25 ve 30±1oC) ve %55 nispi nem ortaminda bugday uzerinde yerel diatom topraginin 0, 100, 300, 500, 900 ile 1500 ppm (mg/kg) konsantrasyonlarinda biyolojik testler yurutulmustur. Mevcut calisma sicakligin test edilen yerel diatom topragin depolanmis tahil zararlilarinin karsi etkinligi uzerine onemli etkiye sahip oldugunu gostermistir. Calismada sicakligin yerel diatom topraginin etkinligine etkisi test edilen bocek turune ve diatom konsantrasyonuna gore degisiklik gosterdigi gorulmustur. Yerel diatom topragi uygulamalarinda sicaklik artisiyla S. oryzae ve T. confusum erginlerinin olum oranlarinda artis saptanirken 30oC’deki olum oranlarinin 20oC ve 25oC’deki olum oranlarindan onemli derecede daha yuksek oldugu gorulmustur. Ancak, yerel diatom topragi uygulanan R. dominica erginlerinde ise 20oC sicaklikta elde edilen R. dominica erginlerinin olum oranlarinin 25oC ve 30oC sicakliktan elde edilen olum oranlarindan daha yuksek oldugu bulunmustur. Bu calismanin sonuclari, 500 ppm ila 900 ppm arasinda degisen dusuk konsantrasyonlarda T. confusum ve S. oryzae erginlerinde %100 olum oraninin elde edildigini gostermistir. Sonuc olarak, bu calismada yurutulen biyolojik test sonuclarina gore, yerel diatom toprak formulasyonun (ACN-1), bugday uzerinde depolanmis tahil boceklerinin kontrolunde kullanilma potansiyeline sahip olabilecegi sonucuna varilmistir.

Preliminary study of great earthquakes relocation in the last decade (2008-2018) in north and central region of Sulawesi Island

Research has been conducted to determine the position of earthquakes that occurred in Sulawesi Island in the last decade (2008-2018). The study area included 2.64 N; 126 E; 118.57 W; and -7.36 S with a maximum depth of 1000 km. A total of 13 data of seismicity were recorded on 26 BMKG stations with a magnitude more than equal to 6 Richter scale. Relocation was done based on the travel time data of P wave and S wave obtained from the Seismic Analysis Code. The data were processed using Geiger method to determine earthquake position. The earth model used in this study was diverse. The relocation result depends on the model of the earth used. Local earth models were required to perform routine data analysis of activities in the region of Sulawesi earthquake.

An experimental approach to the preservation potential of magnetic signatures in anthropogenic fires.

Archaeomagnetic and rock-magnetic methods are of great value in the identification of archaeological fire, especially in Palaeolithic sites where evidence is usually scarce, ambiguous or poorly preserved. Although taphonomic processes can significantly modify Palaeolithic combustion structures, the extent to which such processes affect the magnetic record remains unknown. Here we report the results of an archaeomagnetic study involving five, two-to-five-year-old experimental combustion structures in open-air and cave settings. Some of these combustion structures involved post-combustion human actions such as trampling and relighting. Our results show pseudo-single domain (PSD) magnetite as the main magnetic carrier. Wood ash layers of combustion structures are the most magnetic facies followed by thermally altered sediments constituting the combustion substrates. A decreasing magnetic concentration pattern in depth was observed as a function of temperature. Positive correlation was found between good-quality directional data and macroscopically well-preserved combustion structures. Partial thermoremanent magnetization (pTRM) was the main magnetization mechanism identified in the combustion substrate facies. These data coupled with partial thermomagnetic curve experiments show the potential of these methods to estimate maximum temperatures of the last combustion event. Relightings show very good directional results, but they cannot be identified because the time between them is not enough to statistically distinguish directional variations of the local Earth´s magnetic field. The substrate sediment of an intensively trampled combustion structure yielded reliable archaeomagnetic directions. The results are discussed in terms of magnetization preservation potential and the effects of taphonomic processes on the archaeomagnetic record.

Elemental compositions of particulate matter retained on air condition unit\u2019s filters at Greater Doha, Qatar

Elemental composition of airborne dust samples retained by internal filters of air condition units (ACUs) was determined at 12 locations of Doha city, state of Qatar. Twenty-four elements: Al, Ca, Mg, Fe, Na, K, Ti, Zn, P, Sr, Mn, Ba, Cu, Cr, Ni, Pb, V, Mo, Li, Co, Sb, As, Cd, Be, were analysed by ICP-OES technique after acid digestion of the samples. The analysed components reflect 20.6% of the total sample mass. Similar or lower concentration values have been found for As, Cd, Cr, Cu, Mn, Ni, Pb, V, Zn, Al, and Fe compared to the international context of upper crust concentrations, NIST SRM (urban dust), published local dust information of outdoor, and surface terrestrial deposit (STD) counted for 7.2, 0.7, 91.8, 192.8, 369.7, 68.6, 65.3, 52.1, 824.3, 19,791, 20,508 mg/kg, respectively. The coefficient of correlation (p ≤ 0.05) showed significant association of ACUs dust elemental compositions with the main components of the local earth crust and surface deposits, ranging from the lowest 0.77 (Mg–Fe) to the highest 0.98 (Al–Fe), while Ni and V, typical anthropogenic pollutants, are also strongly correlated (0.86). These strong correlation relationships can be interpreted as the contribution of outdoor particulate to the indoor dust. Dendrogram of metal/Al ratios, based on Euclidean distance calculation and average linkage clustering method, distinguished three typical groups. Studying the enrichment factors of the three groups indicated elevated levels of Zn (131), Pb (49), Cu (32), Cd (8) and Ni (5) found indoors compared to the background composition of STD especially at locations in the industrial zone. The major elemental composition of the samples reflects the typical mineral composition of the local dust, while the trace composition demonstrates the influence of indoor sources. The collected ACU filter dust samples show significant contribution of outdoor mineral particles, non-exhaust traffic emission, industrial sources, as well as the influence of indoor activity such as smoking.

Experimental Strength of Earth-Based Construction Materials in Different Regions of China

According to the latest UN statistics, more than 2 billion people in the world still live in various forms of earthen buildings, including some in China. The variety of earth-based constructional materials is significant among different regions, with each region influencing the selection of local earth construction materials. In this study, earth materials from four regions of China were collected and sorted, with 10 samples from each source, and cube compressive strength tests were performed to analyze the composition and mechanical properties of the four materials, including northeast black earth, southeast red earth, northwest loess, and Xinjiang yellow sand earth. The results showed that significant differences existed in the composition of earth-based constructional materials from different regions, which have influence on the materials’ compressive strength. The order from large to small of compressive strengths was loess, black earth, yellow sandy earth, and red earth. Material load-displacement curves were influenced significantly by the plasticity index, but the overall failure processes of the various samples were basically the same.

Correlations between acute atrial fibrillation and local earth magnetic field strength

Objectives: Atrial fibrillation is the most frequent cardiac arrhythmia affecting over 3 percent and appears to be increasing in general population. In addition to widely discussed such risk factor as obesity, arterial hypertension, electrolytes disbalances and dysfunction of thyroid, there is more and more evidence of human heath interactions with environment parameters such as humidity, temperature, the lunar and the solar activity. Atrial fibrillation, a disorder of heart conductive system, in several studies have been indicated as affected by local Earth magnetic field changes. The study was aimed to analyse possible correlations between the power in the local Earth time-varying magnetic field and admission due to atrial fibrillation. Methods: Two-hundred-fifty-one patients diagnosed with acute atrial fibrillation and treated in Department of Cardiology of Hospital of Lithuanian University of Health Sciences Kaunas Clinics during year of 2016 were retrospectively included into the study. Weekly prevalence of acute atrial fibrillation was compared with weekly summarised changes in the local Earth magnetic field strength. One-year was divided into two time periods according to week number: the first period included weeks from 1 to 26 and the second period included weeks from 27 to 52. Results: Analyses have shown from weak to moderate significant correlations. Tendencies towards higher power magnetic field in low frequently ranges to be associated with higher admission rates were noticeable throughout all analysed periods. Atrial fibrillation concomitant with arterial hypertension was indicated as combination increasing severity of correlation coefficient. Conclusion: Significant correlations between acute atrial fibrillation and the local Earth time varying magnetic field changes were found. Increased magnetic field in low frequency ranges are associated with episodes of acute atrial fibrillation. Arterial hypertension is significantly associated with higher admission due to atrial fibrillation rate under low frequency local Earth magnetic field range.

Valence band of ZnO:Yb probed by resonant photoemission spectroscopy

Resonant photoemission spectroscopy (RPES), which is a useful tool for extracting photoemission response of the localized Rare Earth (RE) impurity levels from the host electronic band structure, was used to study ZnO:Yb films. The resonant enhancement of the photoemission signal at binding energy around 7.5 and 11.7 eV was observed when photon energy was tuned to the Yb 4d-4f absorption threshold (182 eV). It was found that the 4f and the valence band (VB) maximum binding energies do not depend on the Yb dose, suggesting that the measurement of only one concentration is sufficient to determine the binding energies of the Yb 4f in the examined system. Subsequent annealing did not change the arrangements of implanted ytterbium atoms in host matrix: the majority of them remain in 3 + state having pseudo-octahedral local arrangement similar to Yb2O3.

Regional Climate Model Evaluation System powered by Apache Open Climate Workbench v1.3.0: an enabling tool for facilitating regional climate studies

Abstract. The Regional Climate Model Evaluation System (RCMES) is an enabling tool of the National Aeronautics and Space Administration to support the United States National Climate Assessment. As a comprehensive system for evaluating climate models on regional and continental scales using observational datasets from a variety of sources, RCMES is designed to yield information on the performance of climate models and guide their improvement. Here, we present a user-oriented document describing the latest version of RCMES, its development process, and future plans for improvements. The main objective of RCMES is to facilitate the climate model evaluation process at regional scales. RCMES provides a framework for performing systematic evaluations of climate simulations, such as those from the Coordinated Regional Climate Downscaling Experiment (CORDEX), using in situ observations, as well as satellite and reanalysis data products. The main components of RCMES are (1) a database of observations widely used for climate model evaluation, (2) various data loaders to import climate models and observations on local file systems and Earth System Grid Federation (ESGF) nodes, (3) a versatile processor to subset and regrid the loaded datasets, (4) performance metrics designed to assess and quantify model skill, (5) plotting routines to visualize the performance metrics, (6) a toolkit for statistically downscaling climate model simulations, and (7) two installation packages to maximize convenience of users without Python skills. RCMES website is maintained up to date with a brief explanation of these components. Although there are other open-source software (OSS) toolkits that facilitate analysis and evaluation of climate models, there is a need for climate scientists to participate in the development and customization of OSS to study regional climate change. To establish infrastructure and to ensure software sustainability, development of RCMES is an open, publicly accessible process enabled by leveraging the Apache Software Foundation's OSS library, Apache Open Climate Workbench (OCW). The OCW software that powers RCMES includes a Python OSS library for common climate model evaluation tasks as well as a set of user-friendly interfaces for quickly configuring a model evaluation task. OCW also allows users to build their own climate data analysis tools, such as the statistical downscaling toolkit provided as a part of RCMES.

Insecticidal effect of Central Anatolian Region diatomaceous earths against confused flour beetle ( Tribolium confusum Du Val.) on stored paddy

In this study, insecticidal efficacy of different local diatomaceous earth (DE) deposits obtained Central Anatolian Region in Turkey and commercial DE deposit (German origin), Silicosec® were evaluated against substantial pest on stored grain as Tribolium confusum du Val (Coleoptera: Tenebrionidae) at five different concentrations of 100, 300, 500, 900 and 1500 ppm on stored paddy. Mortality of the exposed adults was assessed after 7, 14 and 21 days of exposure. Also progeny productions were assessed after 65 days The tests were carried out at 25±1 oC temperature, 55±5% R.H. under dark conditions. The most effective DE in a short time were assessed AG2N-1 which caused 97% mortality of T. confusum adults at 1500 ppm concentration after 7 days of exposure in paddy. Complete mortality of T. confusum adults was recorded on AG2N-1 at 900 ppm for 14 days and treatments of AG2N-1, BGN-1, CBN-1 for 21 days at 500, 900 and 1500 ppm respectively whereas 87% mortality rate was determined for 21 days exposure of Silicosec® at the highest concentrations on paddy. In conclusion, this study indicated that Turkish DE deposits, AG2N-1, BGN-1 and CBN-1 had high insecticidal efficacy in comparison with the commercial Silicosec® and would have potential to be used against insects in the pest management of stored paddy.

Performance Evaluation of Magnetic Wireless Sensor Networks Algorithm for Traffic Flow Monitoring in Chaotic Cities

Traffic flow monitoring involves the capturing and dissemination of real-time traffic flow information for a road network. When a vehicle, a ferromagnetic object, travels along a road, it disturbs the ambient Earth’s magnetic field, causing its distortion. The resulting distortion carries vehicle signature containing traffic flow related information such as speed, count, direction, and classification. To extract such information in chaotic cities, a novel algorithm based on the resulting magnetic field distortion was developed using nonintrusive sensor localization. The algorithm extracts traffic flow information from resulting magnetic field distortions sensed by magnetic wireless sensor nodes located on the sides of the road. The model magnetic wireless sensor networks algorithm for local Earth’s magnetic field performance was evaluated through simulation using Dar es Salaam City traffic flow conditions. Simulation results for vehicular detection and count showed 93% and 87% success rates during normal and congested traffic states, respectively. Travel Time Index (TTI) was used as a congestion indicator, where different levels of congestion were evaluated depending on the traffic state with a performance of 87% and 88% success rates during normal and congested traffic flow, respectively.

Telluric Field Variations as Drivers of Variations in Cathodic Protection Potential on a Natural Gas Pipeline in New Zealand

AbstractA study of variations in cathodic protection potential on a natural gas pipeline in the North Island of New Zealand is reported. Both the measured pipe‐to‐soil potential (PSP) and the current measured through an installed defect in the pipeline coating show strong correlations with variations in measured magnetic and telluric fields. Contrary to predictions from distributed‐source transmission line theory, analysis shows that the closest correlations of PSP and current are with the component of telluric field perpendicular to the pipeline. This orientation is close to perpendicular to major electrical conductivity contrasts associated with both the local coastline and with on‐shore Earth conductivity structure. It is therefore inferred the variations in PSP which drive the variations in defect current are the result of changes in the local Earth potential. While reporting on specific observations from New Zealand, these results should be applicable across a wide range of middle and high‐latitude global locations. Estimates of possible corrosion rates for the pipeline in question suggest that such enhancement of telluric field variations by conductivity structure may pose significant risk to pipelines in the event of defects in the pipeline coating.

The local earth magnetic field changes impact on weekly hospitalization due to unstable angina pectoris

Objectives: Acute coronary syndrome as an acute oxygenated blood deprivation to the heart muscle due to atherosclerotic plaque rupture in the coronary artery followed by thrombosis is possibly associated with changes in the Earth’s local time varying magnetic field as they strongly influence hormonal and other regulatory systems’ activity. This study analyses the correlation between prevalence of the acute coronary syndrome and the changes in the local time varying aspects of the magnetic field. Methods: Seven-hundred patients admitted to Cardiology Department of Hospital of Lithuanian University of Health Sciences Kaunas Clinics within 2016 due to acute coronary syndrome were retrospectively included into the study. The number of cases per week was compared with the weekly changes of the local Earth magnetic field. The one-year period was divided into two periods: the first-half of the year (weeks 1 to 26) and the second-half of the year (weeks 27 to 52) and more detailed analyses were performed accordingly to the significance of the left main artery lesion. Mean power of local magnetic field fluctuations in Lithuania, measured in pT2 in five different frequency ranges where overlaps between the Schumann resonance and EEG frequency ranges (named as SDelta (0-3.5 Hz), STheta (3.5-7 Hz), SAlpha (7-15 Hz), SBeta (15-32 Hz) and SGamma (32-66 Hz) to distinguish them from the EEG bands). Results: Statistically significant weak and moderate correlations between weekly prevalence of acute coronary syndrome admissions and the magnetic field intensities changes were found. Higher intensities in the SBeta and SGamma ranges were associated with a higher number of admissions throughout the year in females and the SGamma range was associated with higher number of admission only during the second-half of the year in males. A higher intensity magnetic field in SDelta, STheta, SAlpha and SBeta ranges was associated with a higher admissions number due to left main artery lesions in males, while a higher intensity in the SGamma range was associated with higher number of admissions due to left main artery lesions in females through the year. Conclusion: Significant correlation between acute coronary syndrome and changes in the local Earth time varying magnetic field intensities was found. Some frequency ranges are associated with an episode of an acute coronary syndrome. Left main artery lesions significantly correlated with magnetic field changes in most of the frequency ranges in males while only one of the frequency ranges in females.

DISEÑO DE UN CENTRO DE MANDO Y CONTROL TERRESTRE PARA UAVS UTILIZANDO TÉCNICAS AMFE

Summary: We present the design proposal for a center of remote control for UAVs, based on the improvement of different types of ground stations by analysis of mode effect and mode of failure, FMEA and Ishikawa diagrams. So, that has been a center of command and control robust and reliable analysis FMEA analysis of the basic functions of control center. This Control Center, allows to remotely control UAVs in NLOS (Non Line Of Sight) mode as well as the transmission and the reception of data and video from a local earth station that controls the UAV in the LOS (Line Of Sight) mode. Key words: FMEA, diagrams of Ishikawa, ground stations, command and control center, UAV, UAS

Judd–Ofelt analysis and experimental spectroscopic study of erbium doped phosphate glasses

A series of phosphate glasses including two compositions that are similar to commercial laser glasses and 3 new compositions doped with 2 × 1020 Er3+/cm3 were prepared by using the classical melt quenching technique. The new glass compositions show much better glass forming properties than the commercially available glasses, lower molecular weights and lower optical basicities which are expected to be advantageous for their luminescence and laser properties. From the UV–vis–NIR absorption spectra, detailed Judd–Ofelt analyses were conducted and the radiative properties of the luminescent levels of Er3+ in these host materials were calculated. In fact all three compositions show longer calculated luminescence lifetimes than the compositions that are based on commercially available laser glasses. The absorption and the emission cross sections, the luminescence lifetimes and the quantum efficiency at 1530 nm were investigated. LiZnLaAPF glass can be suggested as a good host to generate efficient lasing action at 1530 nm. The variation of the Judd–Ofelt intensity parameters Ω2, Ω4 and Ω6 is discussed with respect to the glass compositions and their properties. For this, the calculated Ω2, Ω4 and Ω6 values are compared to the results of numerous publications on Er3+ doped phosphate glasses. From this data a correlation with the symmetry at the local rare earth site (Ω2) and with the theoretical optical basicity (Ω6) of the glass composition can be assumed.

Correlation between Changes in Local Earth's Magnetic Field and Cases of Acute Myocardial Infarction.

The impact of changes in the geomagnetic field on the human body remains the subject of studies across the world, yet there is no consensus. Current studies are observing effects that require further work by researchers in order to find out the mechanisms that would allow a proper assessment of the correlations between the Earth‘s magnetic field variations and changes in human organisms. The main purpose of this study was to investigate possible correlations between the strength of time-varying aspects of the local Earth’s magnetic field and incidence of myocardial infarctions. Study participants included 435 males and 268 females who had diagnosis of myocardial infarction during the period of 1 January 2016 to 31 December 2016 and attended the Department of Cardiology at the Hospital of Lithuanian University of Health Sciences (LUHS), Kauno klinikos. Time varying magnetic field data was collected at the magnetometer site located in Lithuania. After mathematical analysis, the results support the hypothesis that the Earth’s magnetic field has a relationship between the number of acute myocardial infarction with ST segment elevation (STEMI) cases per week and the average weekly geomagnetic field strength in different frequency ranges. Correlations varied in different age groups as well as in males and females, which may indicate diverse organism sensitivity to the Earth’s magnetic field.

Using semi-finished Ce-La extracts as the sole RE source to synthesize high-performance ZnVMnNbO varistor ceramics

Semi-finished Ce-La extracts of a local Rare Earth (RE) ore refining factory were heat-decomposed to oxides and used as the sole RE source to fabricate high-performance ZnO-V2O5-MnCO3-Nb2O5 (ZnVMnNbO) varistor ceramics. The effect of varying the concentration of this RE dopant within the range of 0–0.25mol% on the microstructure and nonlinearity of the ceramic sintered at 850–950°C was studied by XRD, SEM, EDS, EBSD and I-V test. Besides of ZnO main phase, Ce(La)VO4 solid solution and ZnMn2O4 were identified as the minor secondary phases along with ZnV2O4, Zn3(VO4)2. The average ZnO grain size decreased from 6.35 to 3.37µm in the ceramic samples sintered at 900°C with the increase of Ce-La dopant from 0 to 0.25mol%. The breakdown field was thereby elevated from 3320 to 5590V/cm and the homogeneity of the obtained microstructure was enhanced as well. Only 0.1mol% of such Ce-La dopant was sufficient to improve the nonlinear coefficient of the ZnVMnNbO based varistor ceramics sintered at 875°C to 48.4. The further addition of the RE dopant or the increase of sintering temperature from 875°C to 950°C all decreased the nonlinearity. In general, our result indicated the semi-finished Ce-La extracts can be a feasible and effective candidate to replace pure RE oxides for fabricating high-performance ZnO based varistor ceramics at a lower cost.

Local earth magnetic field and ischemic heart disease: peculiarities of interconnection

Local earth magnetic field and ischemic heart disease: peculiarities of interconnection