A critical review on soil ionisation modelling for grounding electrodes

Grounding electrode resistance non-linearly changes under impulse conditions due to soil ionisation phenomenon. Several models have been proposed to model soil ionisation for grounding electrodes applications. However, to date, there is yet an attempt made to compile all these works into a comprehensive review article. Therefore, this paper is written with the objective of summarizing all related works in this field as a one- stop reference. With reference to the literature, this paper is written to summarize the working principles of the soil ionisation models as well as the accuracy and performance analysis of the models. This paper, particularly highlights the deficiencies of the available models in terms of accuracy and performance. This knowledge will contribute to the development of a new accurate and efficient soil ionisation model

Isolation of keratinophilic fungi and aerobic actinomycetes from park soils in Gorgan, North of Iran

Background: Keratinophilic fungi are a group of fungi that colonize in various keratinous substrates and degrade them to the components with low molecular weight. This study was conducted to determine the prevalence of keratinophilic fungi and aerobic Actinomycetes in soil of city parks in Gorgan. Objectives: In this study, we surveyed the city park soils of Gorgan (a northern province of Iran) to determine the identities and diversity of soil aerobic Actinomycetes, keratinophilic and non-keratinophilic fungi. Materials and Methods: A total of 244 soil samples were collected from 22 diferent parks of Gorgan, North of Iran. The samples were collected from the superfcial layer with depth not exceeding than 0-10 cm in sterile polyethylene bags. We used hair bait technique for isolation keratinophilic fungi. The colonies identifed by macroscopic and microscopic characterization after slide culturing. Actinomycetes were isolated by antibiotic dilution methods and detected by using physiological tests such as Lysozyme, Casein, Xanthine, Hypoxanthine, Gelatin, Urea Broth, and modifed acid-fast stain. Results: Totally, 75 isolates of aerobic Actinomycetes were detected that Actinomadura madurae and Nocardia asteroides were the most prevalent strains, with 14.66 and 28% prevalence respectively. Microsporum gypseum was more frequent than other keratinophilic fungi (22.96%) and Aspergillus spp. was the most species of saprophyte fungi (15.92%). Conclusions: This study showed that the collected soil from studied areas was rich of keratinophilic fungi and Actinomycetes, therefore hygiene protocol should be taken to prevent the spread of pathogenic and saprophytes fungi in the environment of susceptible person. © 2013, Ahvaz Jundishapur University of Medical Sciences

Aging detection of glass disc insulator by using infrared camera

Suitable diagnostic techniques for outdoor glass insulators are important for ensuring the reliablilty and stability of power system. The possibility of insulator flash-over increases, especially when the insulator is covered by pollution layers or has an internal defect. In this paper, a new technique to detect the pollution level and invisible damage by measuring the surface temperature of glass disc insulators is proposed. A high definition camera had been used to determine the surface temperatures of four glass insulators. The effects ofapplied voltage on the surface temperature and its distribution were studied. The results show the possibility of using the infrarad camera to detect the aging level and invisible damages of the glass insulators

Leakage current based thermal modeling of glass disc insulator surface

The stability of transmission lines relies on the health of the insulators, such as glass string insulators, which may occasionally flashover during an overvoltage. The likelihood of flashover increases notably when the glass insulator is wrapped by a wet contaminant layer. In this paper a study of the surface thermal profile of glass disc insulators insulation had been carried out for both clean and polluted surfaces. A finite-element simulation with time dependent model was carried out using COMSOL Multiphysics software. The variation of the insulator surface temperature with applied voltage as well as with pollution layer thickness is explained. The results illustrate the significant effect of pollution conductivity on heat propagate along the surface of the glass insulators with the increase higher voltages’ magnitudes. Study of the aging level impact on a steady state thermal for glass insulation surface is also carried out

Physiology of seed yield in soybean: Growth and dry matter production

A field study was conducted to assess the growth parameters controlling the dry matter and seed yield of soybean. The result shows that growth rate was slow during vegetative phase in all genotypes. A relatively smaller portion of total dry mass (TDM) was produced before flower initiation and the bulk of it after anthesis. Maximum absolute growth rate (AGR) was observed during pod filling stage in all genotypes due to maximum leaf area (LA) development and leaf area index (LAI) at this stage. Plant characters like LAI and AGR contributed to higher TDM production. Results indicate that a high yielding soybean genotype should possess larger LAI, higher TDM production ability and higher AGR at all growth stages.Keywords: Soybean seed yield, total dry mass (TDM), leaf area index (LAI), absolute growth rate (AGR), relative growth rate (RGR

Participatory scenario development to address potential impacts of land use change: an example from the Italian Alps

Changes to land use such as the removal of natural vegetation and expansion of urban areas can result in degradation of the landscape and an increase in hydro-meteorological risk. This has led to higher interest by decision-makers and scientsts in the future consequences of these drivers. Scenario development can be a useful tool for addressing the high uncertainty regarding modeing future land use changes. Scenarios are not exact forecasts, but images of plausible futures. When studying future land dynamics, emphasis should be given to areas experiencing high rates of socioeconomic change. We have focused on the eastern Italian Alps, which face increasing pressure from tourism development. Identified drivers of local land use change are mostly external and difficult to quantify. This area characterized by a traditional Alpine landscape, is subject to high levels of hydro-meteorological risk, another reason to study potential future land use changes. We tested a scenario generation method based on existing decisions and assumptions about future tourism developmnt. We aimed to develop a framework leading to plausible scenarios that can overcome data inaccessibility and address external drivers. We combined qualitative methods, such as stakeholder interviews and cognitive mapping, with geospatial methods, such as geographic infrmation systems, geostatistics, and environmental modeling. We involved stakeholders from the beginning to support the steps of generating data, understanding the system of land use change, and developing a land use change model for scenario development. In this way, we generate spatio-temporal scenarios that can assist future spatial planning and improve preparedness for possible undesirable development

Knudsen gas in a finite random tube: transport diffusion and first passage properties

We consider transport diffusion in a stochastic billiard in a random tube which is elongated in the direction of the first coordinate (the tube axis). Inside the random tube, which is stationary and ergodic, non-interacting particles move straight with constant speed. Upon hitting the tube walls, they are reflected randomly, according to the cosine law: the density of the outgoing direction is proportional to the cosine of the angle between this direction and the normal vector. Steady state transport is studied by introducing an open tube segment as follows: We cut out a large finite segment of the tube with segment boundaries perpendicular to the tube axis. Particles which leave this piece through the segment boundaries disappear from the system. Through stationary injection of particles at one boundary of the segment a steady state with non-vanishing stationary particle current is maintained. We prove (i) that in the thermodynamic limit of an infinite open piece the coarse-grained density profile inside the segment is linear, and (ii) that the transport diffusion coefficient obtained from the ratio of stationary current and effective boundary density gradient equals the diffusion coefficient of a tagged particle in an infinite tube. Thus we prove Fick's law and equality of transport diffusion and self-diffusion coefficients for quite generic rough (random) tubes. We also study some properties of the crossing time and compute the Milne extrapolation length in dependence on the shape of the random tube.Comment: 51 pages, 3 figure

An improved circuit-based grounding electrode considering frequency dependence of soil parameters

This paper presents the simulation of circuit-based vertically oriented grounding electrodes with the consideration of frequency dependence of soil resistivity and permittivity. The resistivity and permittivity were determined using equations proposed by Sundae and Dwight and the frequency dependence properties were modelled according to Scott's model. It was found that the voltage response was highly affected by the frequency, especially at high soil resistivity of 1000 ω and above (up to 4% decrease in voltage response). As for the low soil resistivity cases, the voltage response was less affected by the frequency, which is 1.4% and 1% lower for soil resistivity of 100 ω and 10 ω respectively. Obviously, the current circuit-based model (frequency independent model) tends to provide overestimated results. Therefore, the effect of frequency on the soil resistivity and relative permittivity should not be neglected when determining the transient performance of grounding electrode in order to obtain accurate results

Modelling of electroluminescence in polymeric material using dimensional analysis method: effect of applied voltage and frequency.

Electroluminescence (EL) method has been used by several researchers to observe the behaviour of an aged polymeric material. EL is a phenomenon that occurs when the atoms of a material are being excited due to the application of and external high electrical stresses. The changes in the energy level of these excitation states can be used as an indicator for the initiation of electrical ageing. There are several factors that affect the behaviour of EL emission such as, among others, applied voltage, applied frequency, ageing of material and types of materials and gases used are discussed in this paper. A mathematical approach relating these factors and the intensity of EL is proposed through the aid of Dimensional Analysis method. A close relationship is obtained between experimental and simulation that suggests this mathematical approach can be utilized as a tool to predict electrical ageing of insulation material

The level of creativity in English writing among Jordanian secondary school students

The aim of this study is to explore the level of creativity in English writing among Jordanian secondary school students.The researchers have used a random sample of 100 students of secondary school students in Irbid and Amman cities in Jordan.Adapetd Torrance Test of Creative Thinking (TTCT) was used to measure their creativity in English writing.TTCT test is thought to be the best test to evaluate the creativity dimensions of students in writing.TTCT assesses fluency or the number of ideas; flexibility, the variety of categories in the answers; and originality, which consists in considering innovative answers, neither familiar nor inappropriate.The results of the study showed that the respondents fall in the moderate level of creativity