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Frequency domain spectroscopy is a non-invasive, offline test performed to estimate moisture content, conductivity and aging status of the composite oil-paper insulation of a transformer. In conventional frequency domain spectroscopy test, sinusoidal excitation voltage is applied on the insulation under test for two cycles starting from 0.1 mHz to 1 kHz. One important aspect of conventional dielectric response measurement is the choice of excitation voltage. The insulation in real life operation is often stressed by voltage waveforms, which are non-stationary in nature. Therefore, modification of excitation voltage waveform is required for reliable assessment of insulation condition. Another important factor is the measurement time. Conventional frequency sweep from 0.1 mHz to 1 kHz, makes frequency domain spectroscopy measurement inadvertently lengthy, hence development of new measuring technique is necessary to reduce measurement duration for diagnosis of insulation condition. Considering these two facts, this contribution reports the feasibility of conducting dielectric response measurement in frequency domain using chirp excitation voltage waveforms. Instead of applying sinusoidal excitation at discrete measurement frequencies, chirp signals (band limited from 0.1 mHz to 1 Hz) were used to conduct frequency domain spectroscopy measurement on three laboratory prepared test samples and on two transformers. The dielectric dissipation factors evaluated using chirp waveforms showed a very good agreement when compared to that obtained by using sinusoidal excitation. Besides, investigations also revealed that the proposed method offered least amount of measurement time in comparison with conventional measurement as well as with some existing state of the art methods. [ABSTRACT FROM AUTHOR]

The behavior of polar polymeric dielectrics at high electric fields is controlled by several factors. Among them, dipolar polarization and trapping and de-trapping of space charge are very important, as they are related to the microstructural properties of the material. From the point of insulation diagnostics, it will be highly beneficial if these two are properly identified from material characteristics, as they can reveal a lot about the aging condition of the material. This study aims to characterize the behavior of dipoles and space charge in a polar dielectric from discharge current measurements. Epoxy resin, a widely used dielectric in high voltage system is chosen as the material of interest. Thin epoxy resin samples are stressed at different electric fields for a fixed time period. Then they are discharged to ground and the discharging current is recorded upto a time period of 10000s. The applied electric field was varied from 2kV/mm to 20 kV/mm during electrical stressing of the samples. The discharging current measurements were performed at two temperatures, 25°C and 50°C on same set of specimens. In this paper an attempt has been made to separate the space charge by correlating frequency domain to time domain measurements using Hamon approximation. It was observed that the charge de-trapping phenomena considerably affects the discharging currents when the samples were previously stressed at high fields (10 kV/mm and 20 kV/mm). The distribution of trapped charge along trap depth was also investigated. It was found, that at high electric stress (20 kV/mm), the trapped charge distribution is exponential in nature at the investigated trap depth range. [ABSTRACT FROM AUTHOR]

Formation of space charge in polymeric insulation is a critical issue in the design of high voltage electric systems. Accumulation of space charge accelerates the material aging and may lead to premature breakdown of the insulation. Therefore, it becomes increasingly important to understand the charge injection, trapping and de-trapping processes in dielectric under application of high voltage. However analysis of charge trapping and de-trapping is very difficult due to material properties and also the fact that the measurement of space charge itself is a very complicated issue. Most of the trapping and de-trapping investigation in literature has been performed through indirect means, by measuring the space charge distribution in a dielectric specimen under charging and discharging conditions. The effect of temperature on the trapping and de-trapping properties of polymeric insulating materials has also received limited attention. In this paper, the charge trapping and de-trapping behavior of low density polyethylene (LDPE), a widely used polymeric material for electrical insulation purpose, have been investigated using a direct method based on the depolarization characteristics of a stressed sample. A model has been developed to obtain the trapped charge distribution according to their energy level in the sample directly from the depolarization current. The measurements were performed at different temperature to study the effect of temperature. It was observed that temperature plays a critical role in charge injection, trap formation, trapping and de-trapping. [ABSTRACT FROM PUBLISHER]

It is generally accepted that formation and accumulation of space charge in polymeric insulation is a critical issue in the design of high voltage electric systems, as it leads to insulation degradation and premature failure under high voltage surges and polarity reversals. Even at service stress level, accumulation of space charge may cause electrothermal aging. The insulation degradation and aging is reflected in the trapping and detrapping characteristics of the insulation, making it a useful aging marker. Space charge measurement methods are frequently used for trapping and de-trapping analysis. However, estimation of charge trapping and de-trapping behavior is very difficult due to the involvement of material properties and also partly due to the fact that proper measurement of space charge is itself a very complicated issue, requiring very sophisticated experimental arrangement and signal processing techniques. Moreover, application of these methods is limited to polymeric insulations of certain geometries (planar or radial). In this paper, the charge trapping and de-trapping behavior of low density polyethylene (LDPE), a widely used polymeric material for electrical insulation purpose, have been investigated employing a direct method based on the discharge characteristics obtained after the sample was stressed for short durations. A relationship is established between the de-trapped charge and the extracted charge measured from the discharge current. From this relationship a relative distribution of trapped charges across different trap depths was obtained. It was noticed that the trapped charge distribution is of exponential nature in the trap depth range of 0.93?1.11 eV. The presented method facilitates direct estimation of trap distribution independent of the insulation geometry. It was also observed that the trapped charge is highly dependent on the applied field. [ABSTRACT FROM AUTHOR]

This paper presents a Rough Set Theory (RST) based approach for predicting the surface contamination level of porcelain type insulators at different environmental condition. The sample insulators have been contaminated by Solid layer Method (SLM) according to IEC60507. Leakage current of the insulators are recorded at different contamination level and at different humidity conditions. In the proposed method, autocorrelation technique is used for feature selection from leakage current because it is well suited for non-stationary leakage current signals and cancels out the effect of noise present in the signal. Rough Set Theory is used for classification of extracted features as it suits well with the correlation technique. Result shows that the proposed method is able to detect the contamination level with acceptable range of accuracy. [ABSTRACT FROM PUBLISHER]

Development of sensitive as well as low-cost immunodiagnostics for detection of infected individuals would be an important step towards reaching the goal of lymphatic filariasis elimination by 2020. In an earlier study, using soluble antigens of adult Setaria digitata, we have shown that an antigen fraction in the molecular weight range 14 to 20 kDa can induce differential Th1/ Th2 immune response in the PBMC of the endemic normal (EN) and asymptomatic microfilaraemic (ASM) individuals residing in bancroftian filariasis endemic areas. In the present study, using 2D immunoblot we are able to show that two antigens of 17 and 18 kDa molecular weight and pI of 5-5.5 are recognized by the IgG4 isotype antibodies, a marker for active parasite infection, present in the sera of ASM but not in that of EN individuals. Elevated antigen-specific IgG4 antibodies in the blood are the indicators of circulating parasite in infected individuals who do not have apparent clinical symptoms of filariasis. Thus, we suggest that these two antigens can be explored for the immunodiagnosis of lymphatic filariasis. [ABSTRACT FROM AUTHOR]

2,4-Disubstituted quinoline derivatives were designed based on a 3D-QSAR study, synthesized and evaluated for antimalarial activity. A large dataset of 178 quinoline derivatives was used to perform a 3D-QSAR study using CoMFA and CoMSIA models. PLS analysis provided statistically validated results for CoMFA (r2ncv = 0.969, q2 = 0.677, r2cv = 0.682) and CoMSIA (r2ncv = 0.962, q2 = 0.741, r2cv = 0.683) models. Two series of a total of 40 2,4-disubstituted quinoline derivatives were designed with amide (quinoline-4-carboxamide) and secondary amine (4-aminoquinoline) linkers at the -C4 position of the quinoline ring. For the purpose of selecting better compounds for synthesis with good pEC50 values, activity prediction was carried out using CoMFA and CoMSIA models. Finally, a total of 10 2,4-disubstituted quinoline derivatives were synthesized, and screened for their antimalarial activity based on the reduction of parasitaemia. Compound #5 with amide linker and compound #19 with secondary amine linkers at the -C4 position of the quinoline ring showed maximum reductions of 64% and 57%, respectively, in the level of parasitaemia. In vivo screening assay confirmed and validated the findings of the 3D-QSAR study for the design of quinoline derivatives. [ABSTRACT FROM AUTHOR]

The paper presents a method using deep learning framework based on convolution neural network (CNN), for identification and localization of faults of transformer winding under impulse test. The results show that the proposed method outperforms the existing methods significantly. The present scheme eliminates the requirement of separate feature extraction and classification algorithms for the analysis of fault current patterns. A part of the proposed network performs feature learning and the other part classifies the features in a supervised manner. The method is computation intensive but capable of achieving very high degree of accuracy; on an average a margin of more than 7% compared to other published literature till date. [ABSTRACT FROM AUTHOR]

Partial discharge (PD) localization employing acoustic emission technique is commonly done by estimating the time difference of arrival (TDOA) between signals captured at multiple acoustic sensors placed on the walls of the transformer tank. The localization accuracy of PD sources depends on the accuracy with which the TDOA is estimated. Hence it is important to accurately estimate the TDOA as far as possible. This paper presents a novel approach for the estimation of TDOA which is based on the source-filter model of acoustic theory. The TDOA is estimated by extraction of the excitation source signal from the acoustic signals in the form of an estimation of the PD pulse. The PD pulse serves as the excitation source signal for the acoustic detection system, whereas the acoustic path through the transformer tank and oil constitutes the physical system, which when excited by the PD pulse, gives rise to the acoustic pressure waves. The source-filter model extracts an estimation of the excitation source (PD pulse) by isolating it from the acoustic response of the tank-oil system. The extracted PD pulse information gives a sharp estimate of the instant of appearance of the PD pulse at each sensor. Hence, the TDOA between any two sensors determined from the cross-correlation function between the PD pulse estimates at the respective sensors gives a high estimation accuracy. [ABSTRACT FROM AUTHOR]

Abstract: Various compositions of nano-sized (NiMoO4) x -doped Bi2Ti4O11 (x =0.01, 0.05, 0.1) composites have been prepared by chemical solution decomposition (CSD) method using triethanolamine (TEA) as complexing agent. Ni(II) is one of reactive species on the catalyst surface and Mo(VI) ion helps to compensate the charge of the lattice. The photocatalysts based on the above compositions have been tested for photobleaching of methyl orange (MO) solution under Hg-lamp. The prepared nanopowders are characterized by XRD, EDAX, UV–vis spectra, specific surface area (BET), zeta potential, ESR and HRTEM analyses. The average particle size of nickel molybdate-doped bismuth titanate lies around 30±2nm measured from TEM. Result shows nickel molybdate-doped bismuth titanate (NiMoO4) x (Bi2Ti4O11)1−x (NM x BT1−x ; x =0.01) composite is found to be more photoactive compared all the compositions studied except degussa P25 titania. [Copyright &y& Elsevier]

Abstract: Different compositions of [CuMoO4] x -doped Bi2Ti4O11 nanophotocatalyst (x =0.05, 0.1, 0.5) have been prepared by chemical precursor decomposition (CPD) method using triethanolamine (TEA) and HNO3. Cu(II) is one of reactive species on the catalyst surface and Mo(VI) ion helps to generate charge compensation of lattice having poor catalytic properties. The photocatalytic properties based on the prepared samples for photodecolorization of thymol blue (TB) solutions are examined by Hg-lamp. The crystal structures of the prepared nano-powders are characterized by XRD, EDAX, UV–vis spectra, specific surface area (BET), and HRTEM analyses. The average particle size of copper molybdate-doped bismuth titanate ranges 32±5nm measured from TEM. Results show doping of copper molybdate of 5mol% with bismuth titanate can significantly increase the photoactivity of bismuth titanate compared all the compositions studied except degussa P25 titania. The observed increased photocatalytic activity of copper molybdate-doped bismuth titanate ((CuMoO4) x (Bi2Ti4O11)1−x ; CM x BT1−x ) is attributed to the strong absorption of OH groups at the surface of the catalyst. [Copyright &y& Elsevier]

Abstract: To cure diglycidyl ether of bisphenol A (DGEBA) resin, with new curing agents like amine functional aniline formaldehyde condensates (AFAFC) and amine functional chloroaniline formaldehyde condensates (AFCFC) as a function of concentration of the curing agents, an investigation was carried out. The AFAFC and AFCFC were synthesized from the reaction of aniline and formaldehyde and chloroaniline and formaldehyde, respectively, in acid medium and characterized by FT-IR and NMR spectroscopic analyses, elemental analysis, viscosity measurements, mole of primary and secondary amine analysis and gel permeation chromatography (GPC) analysis. Equimolecular mixture of curing agent and epoxy resin was subjected to curing reaction and the reaction was followed by differential scanning calorimetry (DSC) analysis. The DSC exotherms showed the occurrence of effective curing reaction and the cure kinetics studied from those exotherms revealed that the curing reactions were first order. The mechanical properties, dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) of cured epoxy were also reported. [Copyright &y& Elsevier]

Amine-terminated poly(ethylene glycol) benzoate (ATPEGB), synthesized from the esterification reaction of poly(ethylene glycol) (PEG) with 4-amino benzoic acid, was used to modify the toughness of bisphenol-A diglycidyl ether epoxy resin (DGEBA) cured with room temperature curing agent, triethylene tetramine. ATPEGB was characterized by FT-IR and H-NMR spectroscopies, viscosity measurements, solubility parameter calculation and molecular weight determination with gel-permeation chromatography (GPC). The modified epoxy network was evaluated for its impact, adhesive, tensile, flexural and thermal properties. Improvement in mechanical properties depends upon the concentration of the ATPEGB modifier. The optimum properties were obtained at 12.5 phr (parts per hundred parts of resin) concentration of the modifier. The ATPEGB modified cured epoxy was thermally stable up to 315°C. The morphology of cured epoxy was also analyzed by scanning electron microscopy (SEM) investigation of fracture surfaces. [ABSTRACT FROM AUTHOR]

Partial Discharge (PD) is one of the most critical electrical phenomena affecting the life of electrical equipment. Repetitive PD leading to arcing faults is a recurrent problem in many air insulated systems, such as high voltage air-insulated switchgears. Hence, detection and localization of PD inside such electrical equipment is necessary for early prevention of impending failure. Keeping this in mind, this paper proposes a methodology to localize single and multiple PD sources employing two recent developments in signal processing and machine learning techniques. Optical sensors have been used to record the PD data inside a cubical steel box. A cylindrical barrier has been inserted inside this box to emulate geometrical structures inside Switchgears. Mathematical Morphology aided feature extraction has been employed to extract important features from the PD signal. Sparse Representation classification has been employed to classify the extracted features and to identify the type and location of PD source. The results show that this methodology gives very high classification accuracy corresponding to both single and multiple PD sources. [ABSTRACT FROM AUTHOR]

Plasmodium falciparumdihydroorotate dehydrogenase (PfDHODH) catalyses the fourth reaction ofde novopyrimidine biosynthesis in parasites, and represents an important target for the treatment of malaria. In this study, we describe pharmacophore-based virtual screening combined with docking study and biological evaluation as a rational strategy for identification of novel hits as antimalarial agents. Pharmacophore models were established from knownPfDHODH inhibitors using the GALAHAD module with IC50values ranging from 0.033 μM to 142 μM. The best pharmacophore model consisted of three hydrogen bond acceptor, one hydrogen bond donor and one hydrophobic features. The pharmacophore models were validated through receiver operating characteristic and Günere–Henry scoring methods. The best pharmacophore model as a 3D search query was searched against the IBS database. Several compounds with different structures (scaffolds) were retrieved as hit molecules. Among these compounds, those with a QFITvalue of more than 81 were docked in thePfDHODH enzyme to further explore the binding modes of these compounds.In silicopharmacokinetic and toxicities were predicted for the best docked molecules. Finally, the identified hits were evaluatedin vivofor their antimalarial activity in a parasite inhibition assay. The hits reported here showed good potential to become novel antimalarial agents. [ABSTRACT FROM PUBLISHER]

An experiment was conducted to study the effect of day length, sex, and genotype (Ross x Ross 308 and 708) on mortality causes, bird mobility, footpad health, and ocular size, with 4 trials within the experiment. Four graded day lengths were chosen to allow the study of relationship between day length and health parameters, including 14L:10D, 17L:7D, 20L:4D, and 23L:1D. The primary statistical tools used to assess the day length relationships were regression analysis (Proc Reg and RSReg of SAS). Data were also analyzed as a 4 (lighting program) x 2 (sex) x 2 (genotype) factorial arrangement. Total mortality, as well as mortality due to metabolic and skeletal disease, decreased linearly with increasing inclusion of darkness (7- to 32-, 7- to 38-, and 7- to 48-d periods). Infectious disorders were quadratically related to day length (7-to 48-d period only), with birds under 20L having the highest level. Day length was linearly or quadratically related to average gait score in a positive fashion, and the incidence of birds falling in painful gait score cat-egories increased linearly with increasing day length. Average footpad lesion scores increased with increasing day length (28 and 35 d). The 23L photoperiod resulted in heavier eye weights than other lighting programs. Males had a higher mortality and morbidity rate and a higher average gait score than females. Average footpad score was lower for males than females (28 and 35 d). Overall mortality was higher for 308 than 708 broilers; hence, levels of specific mortality causes were higher. Average gait scores were lower for 308 than 708 birds in 2 of the 3 time periods measured and footpad le-sions were higher. To conclude, many aspects of broiler health improve with decreasing day length. [ABSTRACT FROM AUTHOR]

Abstract: Different metal molybdates incorporated titanium dioxide were prepared by the chemical solution decomposition (CSD) method. Among many transition-metal molybdates, nickel molybdate incorporated titanium dioxide (NMTI) was found to be more photoactive than P25 TiO2 and other metal molybdate doped TiO2 (M x Mo x Ti1−x O6) (M=Ni, Cu, Zn; x =0.05), for photocatalytic oxidation of various dyes solution to harmless decolorized solution at room temperature with the help of Hg lamp. The prepared nano powders were characterized by XRD, UV–vis spectra, specific surface area (BET), UV–vis diffuse reflectance spectrum, EPR spectrum and TEM analyses. The average particle size of NMT1 was found to be 15nm measured from TEM and calculated band gap from adsorption edge is found to be 2.66eV. [Copyright &y& Elsevier]

In this paper, frequency dependent dielectric parameters of pure oils and nanofluids have been studied at different temperatures to investigate any improvement of the dielectric properties due to the presence of nanoparticles. In power transformers, mineral oil is popularly used as an insulating material. However, mineral oils have inherent drawbacks associated with fire hazards and environmental issues. So, as an alternative, vegetable oils are drawing more attention of the researchers in this field. But, pure vegetable oil exhibits weak dielectric properties to be used under high electric stresses. Considering the drawbacks, extensive research work is going on to improve the dielectric strength of eco-friendly vegetable oils by using nanoparticles as additives. In this work, nanoparticles (TiO 2 and Al 2 O 3) based mineral and vegetable (FR3) oil samples have been prepared in laboratory for investigation of their dielectric properties for use in high voltage equipment through frequency domain spectroscopy. The dielectric dissipation factors obtained from FDS measurement have been compared for the aforesaid liquids. Furthermore, frequency domain spectroscopy has been conducted on pure oils and nanofluids at different temperatures to study the effect of temperature on their dielectric properties. Based on the experimental results, LFD of the insulation has been investigated to obtain an idea about aging status of it. • TiO 2 and Al 2 O 3 based nanofluids have been prepared in laboratory. • Temperature effects on Dielectric properties of Mineral and vegetable oil based nanofluids upto 90 °C. • Frequency Domain Spectroscopy has been conducted for different nanofluids at different temperatures. • Corelation between tanδ losses and low frequency dispersion (ΔC) has been proposed. [ABSTRACT FROM AUTHOR]