Search

Samples of LDPE (low-density polyethylene) and LDPE-PANSA (low-density polyethylene -4-Amino-3-hydroxy- 1-naphthalenesulfonic acid) copolymer with Ag0.5�Ni0.5�Fe2O4 powder (as a filler) composites were developed. Following the preliminary characterizations on the thermooxidability (by thermal analysis techniques), the dielectric behavior (by dielectric spectroscopy technique), the mechanical behavior, etc. it was found that the developed materials do not show significant changes after 240 h exposure to 150 mW / m2 UV. The addition of 3wt% PANSA in LDPE has the effect of increasing the mechanical performance of polymer composites with Ag0.5�Ni0.5�Fe2O4 filler. The addition of 15 wt% ferritic powder leads to significant increases in dielectric losses (by about 100% in the case of pure LDPE and about 185% of the LDPE copolymer with 3 wt% PANSA) and to the increase of the real component of the relative permittivity (by about 34.4 % in LPDE, respectively about 36.4% in LPDE copolymer / 3% wt PANSA). Dielectric behavior of the investigated materials indicates that the effect of Ag0.5�Ni0.5�Fe2O4 powder in LDPE and of copolimer LDPE with 3 wt% PANSA consists in the increasing of the shielding efficiency of electromagnetic waves - the maximum effect being recorded in the case of the composite material with the content: LDPE 84.5 wt%, 2.5 wt% / PANSA and 13% wt% Ag0.5�Ni0.5�Fe2O4.

A system for electromagnetic stimulation of microorganisms' activity from the active sludge of wastewater treatment plants was developed and preliminarily tested. Through electrochemical, gravimetric, XRD, and SEM-EDAX measurements, it was found that austenitic stainless steel 18/8 presents good stability to AC polarization in wastewater. Preliminary determinations performed through the dielectric spectroscopy technique indicated that the activated sludge's microbial flora is sensitive to 50 ± 0.1 Hz. The stimulation system developed and put into service on the biological aerobic treatment bioreactor consists of a pair of polarizing electrodes, made of perforated 18/8 stainless steel sheet, electrically connected to a power supply, which at 50 Hz is capable of debiting adjustable voltages between 5 and 24 Vrms at a maximum current of 5 A. Preliminary in situ measurements showed that following the stimulation of the microorganisms from the sludge suspension, as a result of an applied electromagnetic field of approximately 4.5 V/m at 50 Hz, the metabolism of residues is accelerated substantially (organic residues determined by oxygen demand decrease by about 42 %, nitrogen/ammonium content by about 44% and total phosphorus by about 50 % which results in an increase in free oxygen concentration by about 71 %).

By the extrusion and injection technique, polymer-based composite samples (polypropylene and thermoplastic polyurethane) were obtained with BaTiO3 filler in concentrations between 0 and 35 %. Following the preliminary characterizations performed by coupled thermal analysis techniques, it was found that the composite samples obtained have thermal stability up to a temperature of about 250 oC and can be processed by extrusion at temperatures between 180 and 240oC. Above this temperature, a series of degradation processes take place by successive thermooxidation with the formation of volatile products.The electrical characterization of the composite samples was performed by the dielectric spectroscopy technique, which showed that the A tga dielectric losses increase as the BaTiO3 content of the composite increases. The maximum increase being recorded at 50 Hz (the slope A tga /% BaTiO3 about 0.003 /% BaTiO3). It was also found, that the electrical conductivity (o) of the composite increases with the increase of content in BaTiO3 so that o at 100 kHz for the composite with 35 % BaTiO3 is about 50 times higher than for the reference sample M 0 (without filler).

A complex system for zonal earthquake prediction, warning, and local assessment of seismic events has been designed, performed, implemented, and experimented/validated. The system was designed to ensure simultaneously: the reception of warning signals following earthquakes with the epicentre on a radius of 1000 km; acquisition of local precursor data for a possible prediction of seismic events with the epicentre in the perimeter of the targeted locality and/or improvement of the database in the field of Earth physics purchased and processed centrally at the national seismic dispatcher; acquisition of data on the intensity of local seismic movements, based on which, when a predetermined threshold considered dangerous is exceeded, a real-time action order is issued for the protection of high-risk equipment and installations in operation. The realized system is structured on the national seismic dispatcher DSN (with the role of seismic data acquisition from the territory) connected by a bidirectional communication system with a local dispatcher DL which is provided with a system for acquiring and storing local seismic data (vibration detector 3D and temperature transducer mounted in a 40 m deep drilled well, radon detector and associated parameters: temperature, pressure, and humidity of the air mounted at the mouth of the drilled well). The implemented system is able, through the specialized software implemented, to take over the warning signals received from the national seismic dispatcher, to process the locally acquired data, and after the local validation of the seismic event to issue real-time action command (when exceeding values of pre-established major risk threshold) of the protections of high-risk installations in operation in the targeted perimeter. The experimentation/validation of the system, of the interconnection networks, and of the specialized software of the implemented application was done both by continuously recording the local seismic parameters, verifying the communication between DSN and DL, and by taking two warnings regarding seismic events produced (on 30.10.2020  Mw = 7, Greece and on 22.10.2020, at 20:22 hours, ML = 4 R, Vrancea, RO). By processing the data recorded during these events, the speeds of seismic waves in the respective directions were calculated. Thus, for the event of 30.10.2020 Greece, a speed of seismic waves of 7,418 km/second was determined and for the event from 22.10.2020 Vrancea, at 20:22 hours, it was calculated that the secondary waves are moving with 12,686 km/second and the surface seismic waves with 5,063 km/second. Following the analysis/comparison of acceleration intensities with the pre-set threshold level recorded locally for potentially dangerous events, it was found that these events were felt in Râmnicu Vâlcea at a level below the pre-set danger threshold and consequently, the specialized software of the application did not generate a control signal for actuating the protection of high-risk equipment in operation.

Through gravimetric determinations, volume resistivity, dielectric spectroscopy, and comparative thermal analysis (TG, DTA and DTG), the interactions between the distilled water and three different types of alkyd-epoxy-melamine, epoxy and polyurethane lacquers were studied. From the experimental determinations it was found that after 700 h of immersion in water at 20 � 2�C the alkyd-epoxy-melamine based lacquer has a maximum water uptake, respectively 1.76%, followed by the epoxy lacquer 1.4% and polyurethane 0.93%. The thermal analysis sugests that because the water retained by the investigated polymers does not change the TG diagrams in the temperature range up to 150 �C, which suggests that the weight increase of the samples during the immersion could be due to some chemical processes between the water and polymer by which the chemistry structure of the polymer changes. Through electrical measurementes one can observe that after the immersion in water (over 700 hours), dielectric loss increases and the volume resistivity (measured in DC) of the investigated lakes decreases, which is explained by the increasing of polar groups (-OH) in the polymer structure. A comparative analysis of the experimental data reveals that in electrical applications the lacquer LS (polyurethane) is superior to the lacquers L-528 (alkyd-epoxy-melamine) and LG (epoxy), because it has no mass losses (structural changes) up to 280�C it has a volume resistivity of about 21 % higher than L-G, and about 300 % higher than L-528, and has water uptake and dielectric loss substantially lower comparing to L-528 and L-G.

The energy consumption of a high-capacity wastewater treatment plant (up to 900,000 $\mathrm{m}^{3}$ wastewater/month), equipped with biogas production and energy recovery installations, was analyzed via long-term monitoring (76 months). The recorded data during the monitoring period show that the total active electricity (EE) consumption of 8,130,324 MWh (at an average power factor of 83.81%) was provided 48.4% from the electricity network, 51.41% from biogas, and 0.19% from the Safety Diesel generator. The specific global energy consumption recorded was 0.213 kWh/m3 treated wastewater, where the share of consumption related to biological aerobic and anaerobic processing stages is predominant (62.17%).

The power quality of a low-capacity domestic wastewater treatment plant with autonomous operation through automatic control of the technological process was analyzed by monitoring/recording the main electrical parameters. Determinations showed that, under concrete operating conditions (average effluent flow $9.8 m^{3}$/h, 5.9$^{\circ}C$ water temperature in aerobic and anaerobic bioreactors), the average active power absorbed is $11.103 kW$ at an average power factor of 0.73- which leads to a specific consumption of 1.125 kWh/m3 treated water. The evolution of the active power, reactive power, apparent power, power factor, total harmonic distortion of the voltage (THD V), and total harmonic distortion of the current (THD A) parameters show fluctuations determined by the consumers’ operating sequences. The frequent starts/stops of inductive consumers by electromagnetic contactors produce transients reflected on the evolution diagrams of the power factor and THD (both in voltage and current).

In 2020, the energy consumption and volumes of treated wastewater in four village wastewater treatment plants WTP (with a capacity below $10,000 m^{3}/$month), were monitored monthly. The acquired data showed that the specific energy consumption at the investigated WTP (depending on the period and location) was between 1.561 and $2.580 kWh/m^{3}$ treated wastewater, the annual averages being between 1.786 and $2.334 kWh/m^{3}$ (depending on WTP). Moreover, the consumption given by the equipment related to the biological treatment lines BgT primarily determines the total energy consumption in the WTP-the average annual values of the BgT share in the total energy consumption of the investigated WTP were between 0.632 and 0.729. These findings conclude that the WTP energy efficiency improvement is possible primarily by streamlining aerobic and anaerobic biological treatments.

In order to limit the material damages and the human victims caused by some earthquakes, a complex system of protection of high-risk equipment and installations were designed, built and tested in Râmnicu Vâlcea (Romania). Such are the power supply systems and electrical networks that have a warning in case of major earthquakes based on the local measurement / assessment of seismic events. The system was validated by the comparative presentation of the data recorded on the occasion of two recent seismic events -the earthquake of Mw = 6.4 of 2020/12/29 with depth = 10 km Croatia and the earthquake of ML = 4.2R of 2021/02/27 with depth = 125.9 km, Vrancea. The latter was felt in the area of Râmnicu Vâlcea at a distance from the epicenter of 633.9 km and 173.09 km, respectively, producing vibrations with an acceleration of 0.52 mm / s2 and 0.28 mm / s2 respectively. These values were below the 1.2 mm / s2 threshold (considered dangerous for gas and electricity networks) and no warning and command signal was issued.

In order to evaluate the possibility of reuse of some mixed waste from plastic and paper, composite samples of both HDPE and PP basis were made with different filler contents of crushed postage envelope waste. From the morphostructural characterization (SEM images) of the samples obtained it was observed that the HDPE and PP samples had had a homogeneous single-phase structure in contrast to the composite samples with filler from mixed plastic and paper waste. The latter, have a biphasic heterogeneous structure in which the cellulose particles are uniformly distributed. Determinations performed through the dielectric spectroscopy technique indicated that the cellulose content of the composite samples leads to a systematic increase of the dielectric losses (up to about 40% for the HDPE samples, respectively about 30% for the samples with PP), the increases being in direct correlation with the cellulose content of the composite.Mechanical determinations have shown that the average values of tensile strength recorded on the achieved samples, systematically decrease at the increase in the chips content of the samples - decreases up to 10% at an addition up to 15% chips from the waste are explained by the substantially lower mechanical strength of waste paper than that of the HDPE, respective PP.

The magnetic and dielectric behavior of Portland cement mortars with various fly ashes (waste from the thermoelectric power plant) with a Fe2O3 content of 13.8 % was studied. The dielectric losses, tgd, the real component of the dielectric permeability, e�,and the real magnet permeability, �, the parameters with which we calculated the shielding coefficients, a, of the investigated samples, have been determined for the purpose of determining the screening capacity of the investigated samples by magnetic and dielectric spectroscopy in the 50 Hz � 3 kHz (ELF) range. Following experimental data processing, it was found that by increasing the hematite microstructured hematite Fe2O3 content of mortar samples (by fly ash addition) increased shielding capacity in the ELF domain, recorded increases for shielding coefficients, a, to an addition of up to 40 % fly ash, being up to 14.5 times at 50 Hz and up to 21 times at 3 kHz.

This paper shows the ageing study of some coatings and / or impregnation lacquers due to microbiological stress through fungal attack. Dielectric spectroscopy has shown that the dielectric losses of the investigated materials increase as result of microbiological ageing. The mean recorded increases are about 4 times for the alkyl-epoxy-melamine copolymer, 2 times for epoxy polymer and 1.5 times for urethane polymer in agreement with the mould coverage degree of about 20 %, 10 %, and 3 %, respectively. The fungal attack of the investigated polymers led to a decrease in volume resistivity of about 65 % for the alkyl-epoxy-melamine copolymer, 45 % for the epoxy polymer, and 14 % for polyurethane, in agreement with the increase of dielectric losses and degree of mold coverage of the samples. FTIR determinations have shown that fungal attack significantly increased the number of aliphatic -OH and C-H bonds and decreased the number of C-O bonds, respectively of C-O-C oxiran groups and C-C aromatic bonds. DSC thermograms recorded at different temperature ranges and the activation energies calculation for first major oxidation process indicate that after the fungal attack the thermooxidative reactivity of the investigated polymers increases.

HDPE composite samples with aluminum and iron nanopowders were made by extrusion and injection. Samples of material obtained were characterized by comparative determinations of dielectric spectroscopy and SEM microscopy. SEM images have indicated that the agglomerations of the powders used are persistent, do not decompose during extrusion and injection processing. Determinations by dielectric spectroscopy indicated that HDPE composite materials with metal nanopowder filler have higher dielectric losses than pure HDPE (reference). The highest increases in tgd up to 2.6 times, were recorded for 50 nm nanopowders with specific high surface area (over 20 m2 / g). The electrical conductivity of the investigated samples increases with increasing frequency, both for pure HDPE and for HDPE with metal powder filler. As a result of the film effect in the HDPE case with metal filler, the increases in the high frequencies range are lower than in the extremely low frequencies range.

In order to evaluate the behavior in various electrical applications, the main mechanical and electrical characteristics of three different varieties of specifically chosen lacquers - based on alkyl-epoxy-melamine copolymer, the epoxy polymer and polyurethane were compared. From the mechanical determinations, it was found that at ambient temperature the polyurethane lacquer bending resistance was approximately equal to that of the epoxy lacquer and about 6.5 times higher that of the alkyl-epoxy-melamine copolymer. It has also been shown that at bending force of less than 150 Nm the investigated polyurethane lacquer has relatively large deformations of 0.4 mm / kN, which indicates a high capacity to take over relatively high deformations of the metal support (due to thermal expansion from various applications) without significant increasing mechanical stress. The recorded values for the alkyl-epoxy-melamine-based copolymer lacquer and the pure epoxy lacquer are 0.11 mm / kN and 0.03 mm / kN respectively. Determinations by dielectric spectroscopy have shown that at frequencies below 250 Hz the dielectric losses tgd for the epoxy and polyurethane lacquers are approximately equal and are about 2.9 times lower than for the alkyl-epoxy-melamine copolymer lacquer. It was also found that at frequencies higher than 250 Hz the investigated materials behave differently, respectively at the frequency increase up to 10 kHz, the dielectric loss tgd of the polyurethane lacquer remains constant at about 0.0045 in contrast to the epoxide lacquer at which the dielectric loss tgd increases monotone to 0.0095 at 10 kHz, respectively of the alkyl-epoxy-melamine copolymer at which the dielectric loss tgd is approximately constant 0.012 in the 250 Hz-10 kHz range.

In order to identify the causes that led to microbiological degradation by biofouling increases a top coat painting layer applied to a railway bridge was analyzed by both FTIR and the DSC methods; the analysed painting material was that used to paint the bridge in 2013.The determinations were performed comparatively on samples of a similar painting material after 10 days of curing in a natural atmosphere at 25 � 5 �C, after 60 days of storage under laboratory conditions (22 � 5 �C, RH 60 � 10 %, natural lighting), and on samples from the painting material of a certain railway bridge after approx. 4.5 years (exposed natural weathering of temperate climate with Mediterranean influences). From FTIR determinations, the amount of oxygen containing groups (C = O, C-O, C-O-C, -HO) resulted from ageing under various conditions of the painting material.From DSC determinations, the resistance of the paint to the oxidative degradation decreases with the ageing time as resulted from oxidation onset temperatures and oxidation activation energies values - which decreases with 4 kJ / mole (about 2.2 %) in only 60 days of storage in the laboratory and with 7 kJ/mole (about 3.9 %) following exposure to 100 w/m2 for only 15 h and 29 kJ / mole (over 16 %) after exposure to 4.5 years of natural weathering.

In built up media (complex built environment), the materials are simultaneously exposed to a series of physical, chemical and microbiological stress factors that act synergistically with disturbing electromagnetic fields and cause material degradation - with consequences on the durability and safety in exploitation of buildings and installations. The main generative sources of disturbing fields (stray current generators) on built up media are railroads with DC or AC traction with various operating voltage and frequency, medium and high voltage overhead power lines and unbalanced currents from a three-phase power system. The generated stray currents cause destruction both in metallic elements of built structures (railroads, power installations) and in neighbouring constructions and installations (belonging to other administrations) with negative environmental implications.

The species from the increased biofouling on the paint layers applied to the metallic strength structure of a railway bridge located in a Natura 2000 protected area have been identified by specific biologic and microbiological methods. As a result of the analysis of the biological samples taken on the field, it has been found that relatively large variety of filamentous molds are present (Aspergillus fumigatus, Asprgillus flavus, Aspergillus niger, Paecilomyces variotii, Chaetomium globosum, Trichoderma viride, Stachybotris atra, Trichoderma sp., Alternaria sp and Penicillium sp.). Samples also show, lichens (Xanthoria parietina and Hypogymnia physodes) and lower plants capable of photosynthesis such as algae (Chlorophyta Xanthophyceae, Chrysophyceae) and moss (Lunularia cruciata, Marchantiophyta).

Through specific chemical and microbiological determinations, the interaction of the extremely low-frequency (ELF) electric field (EF) of 49.9 Hz and 99.9 Hz with the living matter of the activated sludge from a wastewater treatment plant was studied. The determinations showed that a 49.9 Hz EF significantly stimulates both the multiplication of microorganisms (more than 2$\times$, compared to the reference) and the rate of pollutant metabolism, as opposed to a 99.9 Hz EF, where the stimulation of the multiplication of microorganisms is insignificant (below 1.1$\times$, compared to the reference), instead, more strongly stimulates the metabolism of pollutants.

By electrical determinations, digital microscopy and visual observations, the anticorrosive insulation capacity of the paint layers applied to the three sections of a bridge over the Tisza River was assessed. The visual observations have highlighted the fact that on the Eastern section repainted in 2013, biofouling increases are significant (covers up to 10 % of the surface) - both ferns have been identified (Hypogymnia physodes and Xanthoria parietina), filamentous molds (Aspergillus fumigatus and Aspergillus niger) as well as algae and moss (green - capable of photosynthesis). On paint applied in 1986, no bio fouling was visible but the painting material is aged and shows rust traces (5-10 % of the surface) and exfoliation between the paint layers (10-20 % of the surface). No bio fouling and/ or exfoliation/ degradation of the paint layer have been observed on the paint applied in 2014. Determinations of electrical insulation resistance correlated with those of the paint layers� thickness are closely related to the visual observations. The values obtained for the specific resistivity of the paint layers applied in 2013 (with bio fouling increases) are approx. 38 times lower than those applied in 2014. These findings suggest that the painting material used in 1983 for the top coat realization, showed major qualitative vices.

This paper presents an exhaustive study regarding the behaviour of copper in various insulating fluids when exposed to 1100C for 1000 hours in closed systems, with no access to atmospheric oxygen. Following the analysis carried out, it was found that the variation of oxygen concentration in the investigated oil samples, during the thermal treatment, may be best described using an exponential decrease versus time. Moreover, from the gas chromatography determinations with respect to the evolution of the CO and CO2 content in the oils during the thermal treatment one found out that these fit very well the Richards model, which corroborated with all the other analysis confirms the fact that the copper films undergo consistent morphological changes only when exposed to mineral oils, so that it is of paramount importance that, taking into account this aggressive character, the equipment placed in direct contact with these oils should be carefully inspected on a periodical basis. This behaviour is thought to be a direct consequence of the sulphur compounds contents for these oils, the secondary oxidation products of these compounds increasing their corrosive aggressiveness.

The amounts of flammable gases formed in some transformer oils during the long-term storage (1000 hours) at 110 � 3�C in closed containers (limited access to atmospheric oxygen) were determined qualitatively and quantitatively by gas chromatography technique. The comparative experimental results showed that when two types of mineral oils, one synthetic oil and two types of vegetable oils are in simultaneously contact with copper and insulating paper, the total amount of flammable gases formed by thermal aging is about 40 times higher in the mineral oils than in the ester based oils. It has also been established that the electrical-use copper foil catalyses the formation processes of the flammable gases, the maximum effect being for the mineral oils (an increase of 8 times of ethane and 25 times for methane gases). It has further been observed that the contact with the insulating paper during the thermal treatment of the ester based oils does not influence the formation of flammable gases, compared with the mineral oils where the amount of the formed gases is doubled.

ATR / FTIR and DSC techniques have been used to evaluate the thermal stability of some ageing paint materials by heat treatment while immersion in natural ester-based electro-insulating oil. Experimental determinations have highlighted the fact that the investigated paint materials (epoxy resins) have a high oxygen affinity and thus, in closed systems (such as power transformers), they oxidize before coming into contact with the transformer oil. This behavior indicates that the paint layer (suitably chosen) applied on the inside of the transformer vat functions as an antioxidant and results in increasing the thermal stability of the oil.

This paper presents a comparative study with respect to the behavior of some painting materials, used mainly for decorative and protective industrial applications, exposed to a controlled accelerated ageing process by using thermal storage and successive thermal cycles. The evaluation of the structural changes, as well as those concerning the dielectric loss were carried out in a comparative manner, on the initial samples, before any exposure to thermal stresses and during the ongoing process of the thermal treatments applied. As analysis techniques coupled thermal analysis and dielectric impedance spectroscopy have been used. It was found that there is a clear correlation between the structural changes of the investigated materials, particularly in the case of the epoxy materials subjected to the applied thermal treatments and the evolution of the dielectric losses in the material. As a result of these investigations, one may determine the characteristic acceptable zones for the thermal stresses (up to 1300 h of storage and 1500 thermal cycles), anything above these boundaries leading to strong increases in the dielectric losses and hence the deterioration of the materials rendered unfit to be used for the intended purpose.

For the purpose of using three different types of painting materials for the inner protection of the transformer vats, their behavior was studied under actual conditions of operation in the transformer (thermal stress in electro-insulating fluid based on the natural ester in contact with copper for electro-technical use and electro-insulating paper). By comparing determination of the content in furans products (HPLC technique) and gases formed (by gas-chromatography) in the electro-insulating fluid (natural ester with high oleic content) thermally aged at 130 �C to 1000 hours in closed glass vessels, it have been found that the presence the investigated painting materials lead to a change in the mechanism and kinetics of the thermo-oxidation processes. These changes are supported by oxygen dissolved in oil, what leads to decrease both to gases formation CO2, CO, H2, CH4, C2H4 and C2H6) and furans products (5-HMF, 2-FOL, 2 -FAL and 2-ACF). The painting materials investigated during the heat treatment applied did not suffer any remarkable structural changes affecting their functionality in the electro-insulating fluid based on vegetable esters.

The durability and safe operation of electrical equipment and devices with mixed insulation systems (solid/fluid - electro-insulating paper/oil) is determined by the insulation aging under simultaneous and synergic actions of electrical, thermal and chemical stress factors etc. In this context, degradations of insulating paper exposed to thermal aging in 5 different types of electro-insulating fluid have been studied experimentally. Liquid chromatography determinations have shown that the total content in furan products (resulting from cellulose degradation) in mineral oils is substantially higher than in electro-insulating fluid sorts based on of synthetic ester and/or natural ester (vegetable oil). This is due to the temperature between 90 oC and 130 oC when the activation energy of the furans formation process is up to 7.5 times lower in mineral oils than in ester-based oils. Degree determinations of cellulose polymerization (viscosimetric method) before and after exposure to heat treatment indicated that mineral oils degrade the electro-insulating paper much more strongly than ester-based oils (both synthetic and natural). Obtained results by liquid chromatography and by viscosity are in accordance with the images obtained by optical microscopy (at X 100).

The behaviour of copper and insulation paper in various electrical insulating fluids (transformer oils) exposed to thermal ageing at 110�30C for 1000 hours in closed vessels (without access to atmospheric oxygen) has been studied. The processing of the comparative experimental data revealed in all cases that the concentration of dissolved oxygen in the investigated oils decreases exponentially during the heat treatment. In the presence of the copper foil, the oxygen is almost depleted (the dissolved oxygen concentration is approaching zero), indicating a higher affinity of the copper to oxygen than the affinity to oxygen of the investigated oils. In the presence of the copper foil and / or of the insulation paper, the degradation processes of the mineral oils have a pronounced character, explained by the catalytic activity of the Cu2O film that has been formed and by the paper degradation, respectively. A high thermo-oxidative stability was noticed in the case of natural triglyceride oils, particularly for the synthetic ester-based oil.

UV radiation has a long-term effect on the durability of anti-corrosive coatings applied by painting, generating conditions for accelerated localized corrosion of the protected metallic structure with adverse effects on operational safety. This paper presents a comparative study of the behavior of some painting materials ageing by exposure to UV radiation relevant by the investigation of dielectric behavior using dielectric spectroscopy in conjunction with the thermal stability investigated by coupled techniques of thermal analysis. From a practical point of view, the UV radiation behavior of two materials based on epoxy resins and polyurethane resin used as paints for protective decorative coatings was studied. The results of experimental investigations have shown that in the aging process of the studied painting materials there is a direct correlation between the evolution of the maximum temperature characteristic of the first thermooxidation process and the evolution of the dielectric performances (dielectric loss - tgd).

The behaviour of some insulating fluids in contact with copper foil and / or insulation paper under thermal stress (110�30C for 1000 hours), in a closed system (the access of atmospheric oxygen being limited), has been studied by determining the changes in viscosity and concentration of CO2 and CO. The experimental data revealed that, following the applied heat treatment, the change in viscosity of the esters-based insulating fluids (both synthetic and vegetable) is approximately 7 times lower than in the case of the investigated mineral oils. It has also been found that, following the thermal ageing, the gas content of the mineral oils is substantially higher than in the esters-based oils (8 times higher for CO2 and 4 times higher for CO, respectively). The experimental results indicate superior values for the thermal stability and compatibility with the insulation paper of ester-based insulating fluids.

Polyethylene (PE) insulations have a wide applicability in the insulation of both underground pipelines and underground power cables. In this context, by coupled techniques of thermal analysis (TG/DTG+DTA) and microbiological determinations, have been studied thermooxidability and resistance to moulds action of some polyethylene sorts. Following the processing of the experimental data obtained by thermal analysis it was found that during the applied heat treatment (100 grd C), in the first approx. 380 h, there is a growth of LDPE (low density polyethylene) polymerization degree by elongation of the aliphatic chains, after which the predominant process consists in the structure crosslinking. For MDPE (mean density polyethylene) samples, during the thermal treatment applied, it was found that the crosslinking degree of polyethylene (PE) increased without significant molecular weight change (with all the related consequences of increasing the weight of the tertiary and quaternary carbon atoms in the molecule). Microbiological determinations have highlighted that the resistance to filamentous fungal action of LPDE is higher than that of the investigated MDPE. It was found that after heat treatment applied (1000 h and 100 oC), both at LDPE and at MDPE, decreases the resistance to moulds action is decreased. It has also been found that moulds action resistance is substantially decreased when inoculated culture media and PE samples are exposed to an alternative electric field of 50 Hz - 6 Vrms/cm.

In order to substantiate some impact studies, the paper presents some considerations regarding the main factors determining the local and global impact on the environment of the autonomy electric transport in comparison with the classic traction by internal combustion engines. The main conclusion of the paper is that from the point of view of the local impact, autonomy electric transport-independent of contact lines, is quite advantageous, but from a global point of view, especially for geographic areas where the share of fossil and biomass energy resources is major, Hybrid systems with internal (optimized)/ electric traction (besides other advantages) can have a significantly reduced impact.

The local, regional or global problems created by chemical, physical, noise, microbiological and, not least, electromagnetic environmental pollution are particularly complex. Due to their diverse nature, chemicals are indispensable to areas of great importance such as transport, agriculture, industry, etc. Chemistry and state-of-the-art technology can make our lives more comfortable but not better in terms of health. Pollutants released into the environment during combustion (SO 2 , NO x , PM 10, CO 2 , heavy metals) can affect all the components of the environment, the life of the animal, plant, and of man. Removing coal from the energy mix is a solution that would bring enormous benefits to people's health. The paper presents an assessment of the harmful emissions produced by coal-fired power plants and those produced by urban transport. Thus, an intercomparison of the level of concentrations of these harmful emissions from industrial sectors — energy and transport, the degree of dispersion of these harmful emissions in delimited areas as well as the noxious effects is a picture of the risk associated with the manufacture and use of chemicals, which may be diminished by using “green chemistry” processes and technologies. This pathway is one of the important alternatives to the sustainable development of the world in conditions of population growth without sacrificing the quality of the environment.

The corrosiveness and thermal stability of five types of insulating oils — both in contact and contactless with copper and S235J2G3 carbon steel — have been studied through gravimetric determination, XRF analysis and dynamic viscosity measurements. The experimental results showed that, after a heat treatment (700 hours) at 110± 30°C, the weight of the investigated samples by mineral oil drops (by volatilization) to be between 7 and 7.5%. For vegetable oils have not been registered remarkable changes in weight. The XRF analyzes revealed that the investigated new minerals oils have a sulfur content up to 0.03% and the used oil sample (30 years in transformer) up to 0.14%. Sulfur content in the vegetable oils has been not recorded. Corrosion of copper and carbon steel in the investigated oils increased due to increasing the sulfur content.

ZnO based surge protective devices have been made and characterized both morphological (SEM microscopy and interferometry) and electrical (U/I characteristic and dielectric spectroscopy). SEM microscopy analyzes revealed that the disks of metal oxides sintered at 12000C present a homogeneous distribution of ZnO grains, without pores and well-defined intergranular limits. It was also found that Ag electrodes (applied by Ag paste to 650°C) are well anchored in the structure of the sintered material. The interferometry measurements revealed that the sintered material surface roughness ranges within ± 3μm. The electrical measurements revealed that the threshold voltage of the achieved devices is proportional to the thickness of the disks of approximately 156V / mm. Reverse currents, measured at 0.8 of the threshold voltage were between 0.28 and 0.31mA. Also, the measurements of dielectric spectroscopy revealed that the dielectric loss is highly dependent on frequency, respectively about 0.15 at 40 Hz and decreases exponentially to 0.019 at 10 kHz.

In order to determine the durability of polymer coatings using investigation techniques based on X-rays diffraction and combined techniques for thermal analysis (TG-DTA-DTG), were determined the changes of structure and of their thermo-oxidative characteristics (6 different paint types having different characteristics) after exposure to UV radiation (60W/m2 in range of 300–400nm). The experimental results, indicate that UV radiation induce different changes (function of the commercial type of any paint) of the investigated topcoat paint films respectively, increase of the crystallinity (and, implicit, of the fragility) function of the exposure dose, which was between 0,0005 and 0,0150%/Wh/m2.

Based on recent bibliographical data, representative actions of microorganisms on materials used in electrical engineering have been analyzed. The analysis undertaken have been revealed that the microorganisms, especially filamentous molds, have an important role in biocorrosion of metallic materials — in their presence the corrosion rate can increase up to 10 times. Biofilm formation on the surface of magnets has as effect the increasing of corrosion rate of approx. 7 times and degradation of magnetic characteristics. Microorganisms, especially filamentous molds have an important role in aging of the underground power cables insulation by initiating degradation of external polymeric jackets. On the other hand the microorganisms have a beneficial contribution in the biodegradation of insulating oils reached in the environment accidentally, in soil remediation and surface water pollution, respectively. It is noted that the biochemical processes of some microorganisms are stimulated by exposing of cultures to 50 ± 0.2Hz electric field, where the biocorrosion and biodeterioration processes are substantially accelerated / amplified.

In the paper are evaluated the induced potential in pipeline based on the subdivision of the zone of influence AC Power Lines / electric traction line / gas pipeline, in a relatively great number of sections in order to be able to determine voltages at many positions along the gas pipeline. Is presented a practical case from Cluj, of subdivision of the zone of influence in sections (a circuit model) and is created a special interpolation algorithm for the precise calculation of the induced voltages values in different points on the pipeline taking into account the measured data. Because there are only a set of available reactance measurements, for a continuous function between the magnetic permeability and electrical induced currents, it is necessary to apply numerical interpolation methods and/or nonlinear curve fitting procedures.

In this paper an experimental study regarding the behavior of the yeast subjected to the electric field action at a frequency of 50 Hz is presented. The aqueous suspension was prepared from distilled water - 94 ml, dry yeast - 5 g and sugar - 1 g. The dielectric spectroscopy method was used in order to characterize the contributions of proteins to the dielectric properties of the suspension. The complex permittivity and conductivity were measured at 50 Hz at room temperature. The applied electric field varies between 1 V/cm and 6 V/cm (effective value). Conductivity and permittivity are found to increase, resulting in variations in magnitude of the applied field.