Thermal experimental dielectric characterization of cost-fewer low-density polyethylene nanocomposites

Polymer properties can be experimentally tailored by adding small amounts of different fillers, but they are expensive with respect to the classical polymer materials. This paper has been studied the enhancement and controlling of electric and dielectric properties of low-density polyethylene (LDPE) polymer materials by cost-fewer nanoparticles. Certain percentages of clay and fumed silica nanoparticles have been enhanced electric and dielectric properties of low-density polyethylene nanocomposite. Dielectric spectroscopy has been measured the electric and dielectric properties of low-density polyethylene with and without nanofillers at various frequencies (10Hz-100kHz) and temperatures (20°C, 40°C and 60°C). Also, it has been investigated the optimum percentages of nanofillers with respect to nanofillers type, filler concentration and temperature for enhancing electric and dielectric characterization of low-density polyethylene. Experimental measurements have been carried out on dielectric breakdown strength of new polyethylene nanocomposites materials under variant electric fields (uniform, and non-uniform) and variant temperatures. It has been specified the effective nanofillers factors on dielectric breakdown strength of polyethylene nanocomposites materials

Factors Affecting the Sheath Losses in Single-Core Underground Power Cables with Two-Points Bonding Method

Single-core underground power cables with two-points bonding induce currents in their metallic sheaths. The sheath induced currents are undesirable and generate power losses and reduce the cable ampacity. This paper has shown that the values of the sheath losses in some cases could be greater than conductor losses, depending on various factors. Such these factors are type of cable layouts, cable parameters, cable spacing, sheath resistance, phase rotation, conductor current and cable armoring. In this paper the above factors have been investigated. The calculations are carried out depending mainly on IEC 60287 by a proposed computer program using MATLAB.Keywords: Single-core cables, two-point bonding method, sheaths losses, flat, trefoil, armoringDOI:http://dx.doi.org/10.11591/ijece.v2i1.11

Comparasion between Oil Immersed and SF6 Gas Power Transformers Ratings

           Power transformers present the largest portion of the capital investment in addition the power transformer remains oil immersed which presents a fire hazard that is particularly objectionable in urban and metropolitan environment. After careful studies of various alternatives to conventional transformer technology to produce a gas insulated power transformer with increased mega volt-ampere ratings, gas insulated power transformer has been developed with a use with non flammable SF6 gas. For changing the insulating material from oil to SF6 gas a comparative study between these types of transformers should be made. In this paper two mathematical models are suggested and simulated by computer programs to calculate the temperature of the cooling mediums and transformer windings. The obtained results are in agreement wit the measured values in the field

Effect of acidizing rate on enhanced oil recovery for Eocene Thebes limestone, Eastern of the Gulf of Suez, Egypt

38-42Thebes Limestone of Eocene age contributes to oil producing reservoir of Abu Rudeis Field. Acidizing process has been applied successfully for many years to increase the productivity of petroleum wells in carbonate formations, consequently demands of application acidizing techniques are increasing. Carbonate acidizing differs than that occurs in sandstone because the reactive nature of a carbonate rock, as a result of this, carbonate acidizing causes formation of large flow channels in some portions of the rock comparing with the original pore size distrubution, in addition enlarging of some aspects as diameters, areas and volumes of original pores. This study investigated that the presence of oil slows reaction rate of HCL acid with a carbonate reservoir rock, where the treatment of carbonate reservoir rock with high concentrated HCL acid speeds up the acidizing rate, decreases the effect of oil within the rock and creates much new channels that facilitate injectivity and productivity of oil wells. The effects of acidizing on carbonate rocks at various conditions were different and obvious, consequently help us to improve the oil recovery from reservoir rocks

Global economic burden of unmet surgical need for appendicitis

Background There is a substantial gap in provision of adequate surgical care in many low- and middle-income countries. This study aimed to identify the economic burden of unmet surgical need for the common condition of appendicitis. Methods Data on the incidence of appendicitis from 170 countries and two different approaches were used to estimate numbers of patients who do not receive surgery: as a fixed proportion of the total unmet surgical need per country (approach 1); and based on country income status (approach 2). Indirect costs with current levels of access and local quality, and those if quality were at the standards of high-income countries, were estimated. A human capital approach was applied, focusing on the economic burden resulting from premature death and absenteeism. Results Excess mortality was 4185 per 100 000 cases of appendicitis using approach 1 and 3448 per 100 000 using approach 2. The economic burden of continuing current levels of access and local quality was USD 92 492 million using approach 1 and USD 73 141 million using approach 2. The economic burden of not providing surgical care to the standards of high-income countries was USD 95 004 million using approach 1 and USD 75 666 million using approach 2. The largest share of these costs resulted from premature death (97.7 per cent) and lack of access (97.0 per cent) in contrast to lack of quality. Conclusion For a comparatively non-complex emergency condition such as appendicitis, increasing access to care should be prioritized. Although improving quality of care should not be neglected, increasing provision of care at current standards could reduce societal costs substantially.publishedVersio

Mortality of emergency abdominal surgery in high-, middle- and low-income countries

Background: Surgical mortality data are collected routinely in high-income countries, yet virtually no low- or middle-income countries have outcome surveillance in place. The aim was prospectively to collect worldwide mortality data following emergency abdominal surgery, comparing findings across countries with a low, middle or high Human Development Index (HDI). Methods: This was a prospective, multicentre, cohort study. Self-selected hospitals performing emergency surgery submitted prespecified data for consecutive patients from at least one 2-week interval during July to December 2014. Postoperative mortality was analysed by hierarchical multivariable logistic regression. Results: Data were obtained for 10 745 patients from 357 centres in 58 countries; 6538 were from high-, 2889 from middle- and 1318 from low-HDI settings. The overall mortality rate was 1⋅6 per cent at 24 h (high 1⋅1 per cent, middle 1⋅9 per cent, low 3⋅4 per cent; P < 0⋅001), increasing to 5⋅4 per cent by 30 days (high 4⋅5 per cent, middle 6⋅0 per cent, low 8⋅6 per cent; P < 0⋅001). Of the 578 patients who died, 404 (69⋅9 per cent) did so between 24 h and 30 days following surgery (high 74⋅2 per cent, middle 68⋅8 per cent, low 60⋅5 per cent). After adjustment, 30-day mortality remained higher in middle-income (odds ratio (OR) 2⋅78, 95 per cent c.i. 1⋅84 to 4⋅20) and low-income (OR 2⋅97, 1⋅84 to 4⋅81) countries. Surgical safety checklist use was less frequent in low- and middle-income countries, but when used was associated with reduced mortality at 30 days. Conclusion: Mortality is three times higher in low- compared with high-HDI countries even when adjusted for prognostic factors. Patient safety factors may have an important role. Registration number: NCT02179112 (http://www.clinicaltrials.gov)

Power Transformer Incipient Faults Diagnosis Based on Dissolved Gas Analysis

Incipient fault diagnosis of a power transformer is greatly influenced by the condition assessment of its insulation system oil and/or paper insulation. Dissolved gas-in-oil analysis (DGA) is one of the most powerfull techniques for the detection of incipient fault condition within oil-immersed transformers. The transformer data has been analyzed using key gases, Doernenburg, Roger, IEC and Duval triangle techniques. This paper introduce a MATLAB program to help in unification DGA interpretation techniques to investigate the accuracy of these techniques in interpreting the transformer condition and to provide the best suggestion for the type of the fault within the transformer based on fault percentage. It proposes a proper maintenance action based on DGA results which is useful for planning an appropriate maintenance strategy to keep the power transformer in acceptable condition. The evaluation is carried out on DGA data obtained from 352 oil samples has been summarized into 46 samples that have been collected from a 38 different transformers of different rating and different life span

Mitigation of the Electric and Magnetic Fields of 500-kV Overhead Transmission Lines

Publisher Copyright: © 2013 IEEE.The electric and magnetic fields of overhead high voltage transmission lines are still a critical problem for new construction because of their biological effects on the human body. This issue has been a subject of scientific interest and public concern for the risk of the electric and magnetic fields on living organisms. Accordingly, the overhead transmission lines are considered a source of such this risk due to their high electric and magnetic fields in the populated areas. Because of the recent concerns that electric besides magnetic fields, generated by overhead transmission lines, electric power researchers have been trying to find effective methods for the mitigation of the electrical and magnetic fields to be in the range of acceptable limits. Researchers have been trying to find transmission line geometries that will reduce these electric and magnetic fields. Therefore, in this article two novel methods of reducing the electric and magnetic fields are discussed, one is to change the position of the center phase to optimize the delta configuration and the other is to use more than two shielding wires with calculating the currents in these wires. The obtained results of the two proposed methods are compared with the electric as well as magnetic fields, and the right-of-way values of the present conventional configuration. Additionally, this article presents a case study carried out on an Egyptian 500 kV high voltage overhead transmission line for the mitigation of magnetic and electric field intensities.Peer reviewe