Effect of side chains on the dielectric properties of alkyl esters derived from palm kernel oil

Alkyl ester derivatives were synthesized from laboratory purified palm kernel oil. The steps in the synthesis involved transesterification of palm kernel oil to produce a methyl ester, followed by epoxidation and then the grafting of side chains by esterification with propionic and butyric anhydride. The dielectric and thermal properties of the ester derivatives were analyzed and compared with the methyl ester. The melting point of the ester derivatives were found to reduce with side chain attachment and antioxidant improved its thermal stability. The dielectric loss was dominated by mobile charged particles and the chemical modification appeared to increase the rate at which electric double layer was formed at the electrode-liquid interface. The esters possessed excellent breakdown strengths suggesting that the processing to optimize their physical properties did not have a negative influence on their electrical breakdown strength. This product may prove useful as an insulation fluid in Electrical Power Transformers

Electrical breakdown strength characteristics of palm kernel oil ester-based dielectric fluids

Natural ester fluids have been synthesized from crude palm kernel oil for consideration as an alternative to mineral oil based insulating fluid. Chemical modification of the oil enhanced the physico-chemical properties of the fluid. This paper presents the statistical analysis of the AC electrical breakdown strength of the synthesized esters in comparison with the crude palm kernel oil sample. The breakdown test was carried out in accordance with ASTM 1816 test method using a bespoke test cell designed for small sample volume. The estimated characteristic breakdown strength of the esters, defined as the 63.2% cumulative failure probability, is significantly higher than the BS148 mineral oil. The slopes, indicating the shape parameters, are similar. The results suggest that, at least in this regard, the synthesized esters may serve as an alternative to mineral oil as a transformer fluid

Aging of Kraft paper insulation in natural ester dielectric fluid

The aging behavior of transformer insulation Kraft paper aged in a natural ester oil, recently developed from palm kernel oil, is compared to the behavior of paper samples aged in mineral insulating oil. This study aimed to investigate the effect of the natural ester oil on the aging of cellulose insulation paper if used as an alternative insulating fluid in transformers. Thermally upgraded insulation paper was aged in both insulating fluids together with strips of galvanized steel, copper and aluminium to represent the transformer, under nitrogen pressure in a sealed mild steel pressure vessel for 150 degC for 28, 56, and 84 days. The degradation after aging was assessed using tensile strength and breakdown strength measurements of the paper. The paper samples impregnated with natural ester fluid exhibited similar behavior before and after aging, with an approximately 5% reduction in tensile strength after 28 days of ageing. Two sets of response were obtained for paper samples aged in mineral insulating oil under the same ageing conditions; the paper closer to the copper strips had a faster degradation rate (~35% reduction). The natural ester fluid retarded the aging of the Kraft paper. The characteristic breakdown strength of natural ester impregnated paper was found to be, on the average, 42% better than that of mineral oil impregnated paper

Electrical Conduction and Dielectric Breakdown Characteristics of Alkyl Ester Dielectric Fluids obtained from Palm Kernel Oil

Naturally occurring palm kernel oil (PKO) and its ester derivatives are being considered as sustainable alternatives to synthetic oils for use as dielectric fluids. This paper reports on their dielectric properties, which have been studied and compared to BS148 mineral oil. The low frequency complex dielectric response of the PKO and its derivatives are related to ionic conduction and electrode polarization phenomena. The purified PKO has an electrical conductivity of 3.04 ?? 10-12 Sm-1 at 30°C; this is 10 times lower than crude PKO but about 10 times greater than the BS148 oil. The bulk conductivity is thermally activated, activation energy = 0.47 eV, and influenced by viscosity. The ester derivatives have a higher conductivity than the PKO, which is related to ionic impurities introduced during processing. The breakdown field was measured in a bespoke cell enabling smaller volumes of oil (15 ml) than that used in ASTM D1816. The characteristic ac breakdown strength of purified PKO and is alkyl esters were found to be in the range, 41 to 43 kV/mm, which is significantly higher than the mineral oil (27 kV/mm). The results support the proposition that a dielectric fluid derived from palm kernel oil, once re-purified, may be a suitable replacement for mineral oil based fluids in HV electrical equipment

Electrical properties of ester dielectric fluids from palm kernel oil

This paper presents characteristics of dielectric fluids prepared from chemical modification of palm kernel oil ester as an alternative to mineral oil for use in HV electric equipment such as transformers. The palm kernel oil-based alkyl ester dielectric fluids were synthesized from palm kernel oil through epoxidation and esterification reactions. The functional groups in the alkyl esters were identified using FTIR spectroscopy. The rationale for this processing and its effect on the physical properties, such as melting, are presented. The AC breakdown voltage, volume resistivity, relative complex permittivity, and tan of the esters were measured. The dielectric response results indicate that the relaxation processes correspond to ionic conduction and electrode polarization phenomena. The breakdown strength of the alkyl esters were found to have a significant improvement compared with the crude oil sample

Musings on privacy issues in health research involving disaggregate geographic data about individuals

This paper offers a state-of-the-art overview of the intertwined privacy, confidentiality, and security issues that are commonly encountered in health research involving disaggregate geographic data about individuals. Key definitions are provided, along with some examples of actual and potential security and confidentiality breaches and related incidents that captured mainstream media and public interest in recent months and years. The paper then goes on to present a brief survey of the research literature on location privacy/confidentiality concerns and on privacy-preserving solutions in conventional health research and beyond, touching on the emerging privacy issues associated with online consumer geoinformatics and location-based services. The 'missing ring' (in many treatments of the topic) of data security is also discussed. Personal information and privacy legislations in two countries, Canada and the UK, are covered, as well as some examples of recent research projects and events about the subject. Select highlights from a June 2009 URISA (Urban and Regional Information Systems Association) workshop entitled 'Protecting Privacy and Confidentiality of Geographic Data in Health Research' are then presented. The paper concludes by briefly charting the complexity of the domain and the many challenges associated with it, and proposing a novel, 'one stop shop' case-based reasoning framework to streamline the provision of clear and individualised guidance for the design and approval of new research projects (involving geographical identifiers about individuals), including crisp recommendations on which specific privacy-preserving solutions and approaches would be suitable in each case

Variationally Mimetic Operator Networks

In recent years operator networks have emerged as promising deep learning tools for approximating the solution to partial differential equations (PDEs). These networks map input functions that describe material properties, forcing functions and boundary data to the solution of a PDE. This work describes a new architecture for operator networks that mimics the form of the numerical solution obtained from an approximate variational or weak formulation of the problem. The application of these ideas to a generic elliptic PDE leads to a variationally mimetic operator network (VarMiON). Like the conventional Deep Operator Network (DeepONet) the VarMiON is also composed of a sub-network that constructs the basis functions for the output and another that constructs the coefficients for these basis functions. However, in contrast to the DeepONet, the architecture of these sub-networks in the VarMiON is precisely determined. An analysis of the error in the VarMiON solution reveals that it contains contributions from the error in the training data, the training error, the quadrature error in sampling input and output functions, and a "covering error" that measures the distance between the test input functions and the nearest functions in the training dataset. It also depends on the stability constants for the exact solution operator and its VarMiON approximation. The application of the VarMiON to a canonical elliptic PDE and a nonlinear PDE reveals that for approximately the same number of network parameters, on average the VarMiON incurs smaller errors than a standard DeepONet and a recently proposed multiple-input operator network (MIONet). Further, its performance is more robust to variations in input functions, the techniques used to sample the input and output functions, the techniques used to construct the basis functions, and the number of input functions.Comment: 49 pages, 18 figures, 1 Appendi

Energy efficiency of information transmission by electrically coupled neurons

The generation of spikes by neurons is energetically a costly process. This paper studies the consumption of energy and the information entropy in the signalling activity of a model neuron both when it is supposed isolated and when it is coupled to another neuron by an electrical synapse. The neuron has been modelled by a four dimensional Hindmarsh-Rose type kinetic model for which an energy function has been deduced. For the isolated neuron values of energy consumption and information entropy at different signalling regimes have been computed. For two neurons coupled by a gap junction we have analyzed the roles of the membrane and synapse in the contribution of the energy that is required for their organized signalling. Computational results are provided for cases of identical and nonidentical neurons coupled by unidirectional and bidirectional gap junctions. One relevant result is that there are values of the coupling strength at which the organized signalling of two neurons induced by the gap junction takes place at relatively low values of energy consumption and the ratio of mutual information to energy consumption is relatively high. Therefore, communicating at these coupling values could be energetically the most efficient option

Imaging of hydrothermal altered zones in Wadi Al-Bana, in southern Yemen, using remote sensing techniques and very low frequency–electromagnetic data

© 2019, Saudi Society for Geosciences. Economic mineralization and hydrothermally altered zones are areas of great economic interests. This study focusses on hydrothermal altered zones of high mineralization potentials in Wadi Al-Bana, in southern Yemen. An azimuthal very low frequency–electromagnetic (AVLF-EM) data acquisition was conducted in search for mineralization in the study area. The study integrated observations from geophysical field data with others extracted from object-oriented principal component analysis (PCA) to better map and understand mineralization in the investigated area. This technique was applied to two data sets, ASTER and Landsat 8 Operational Land Imager (OLI) imagery. The results of PCA revealed high accuracy in detecting alteration minerals and for mapping zones of high concentration of these minerals. The PCA-based distribution of selected alteration zones correlated spatially with high conductivity anomalies in the subsurface that were detected by VLF measurements. Finally, a GIS model was built and successfully utilized to categorize the resulted altered zones, into three levels. [Figure not available: see fulltext.]