13 research outputs found
ANTHROPIC IMPACT ON AIR QUALITY IN THE DANUBE REGION
There were monitored by data acquisition
both in summer and winter period, the concentrations
of pollutants - SO2, NO2 and particulate matter
(PM10) – existing in air on the territory of 6 counties
bordering the Danube. After processing and analysis
of collected data have been found that: SO2 pollution
may be due primarily burning fuel with high sulfur
content and / or industrial activities for carbonic
products (anodes for obtaining the electrolytic
aluminum, graphite electrodes etc.); pollution with
NO2 comes primarily from automobile exhaust gases;
particulate matter pollution may be due both loess
soil (high winds in dry periods) characteristic of the
area
DURABILITY OF ANTICORROSIVE PROTECTION COATINGS FOR ELECTRO-ENERGETIC EQUIPMENT
Determining the working life of the
anticorrosive protection layers is of great importance
for electro-energetic installations. In order to assess
the durability of the paint layers have been achieved
films of 100 ÷ 120µm from six different commercial
types of paint. After polymerization/drying, the
dielectric characterization of the obtained films has
been achieved by dielectric spectroscopy - both before
and after their exposure to controlled doses of UV
radiation. The experimental results have been
revealed that the polymer matrix of the painting
materials, over a critical dose of UV radiation
(specific commercial sort), suffers a complex process
of aging after which the anticorrosive insulation
capacity decreases
Structure and Adhesive Properties of Nanocomposites Based on Functionalized Nanofillers
Nanocomposite samples of the copolymer of ethylene and vinyl acetate containing carbon nanofibers and nanotubes have been prepared by mixing in solution. In order to improve interfacial interactions in the polymer-nanofiller system they were subjected to a preliminary chemical functionalization. The efficiency of functionalization was estimated by the IR spectroscopy. The X-ray diffraction and strength characteristics of the obtained nanocomposites filled by the untreated and functionalized carbon nanofibers and nanotubes with different filling degree were compared
STUDY OF SOME INSULATING OILS AGING BY THERMAL CYCLING
The By gravimetric measurements and
coupled thermal analysis techniques (DTG+TG+DTA)
the aging of different sorts of insulating oil was
studied by thermal cycling between -400C and 850C.
The experimental results showed that, during the
thermal cycling of the investigated mineral oils, their
composition changes due to the volatilization of the
volatile fractions (mass losses between 3.9% and
5.8%), unlike the investigated vegetable oil that
showed a mass increase of approx. 0.66%. It has also
been found that the mineral oils can be ensure a safe
operation, without significant changes up to a
maximum of 1000C, as long as investigating vegetable
oil can be used without degradation risk up to 2000C
INFLUENCES OF 50HZ ELECTRIC FIELDS ON GROWTH AND MULTIPLICATION OF SOME MICROORGANISMS
By dielectric spectroscopy and specific
microbiological techniques have been studied the
development (cell multiplication) of Saccharomyces
cerevisiae and Aspergillus niger growing and
multiplication - both on culture media with sucrose
and on those with starch. The experimental results
have been revealed that the biochemical processes of
the studied biomasses have significant changes in
certain frequencies in the range 1 - 160Hz,
characteristic of the different species/metabolized
carbon source, respectively species/ metabolized
carbon source/ development phase. It has also been
found that in the case of Saccharomyces cerevisiae, the
electric field of 50 Hz up to 20V/cm reduces the length
of the LAG time and increases the growth rate of
intensive increasing phase. Cultures of Aspergillus
niger on culture medium with sucrose are stimulated
(increasing the spores production by approx. 50%
and reducing the maturity time) of 50Hz signals up to
15V/cm. Electric fields higher than 30 V/cm in all
media and investigated cultures carry on to the
growth reduction / multiplication - up to a complete
inhibition of growth at approx. 50V/c
On the relationship between optical and structural properties of polymer films modified by carbon micro and nanopartciles
The studies were concentrated on investigations of optical and structural characteristics of polymeric films filled by carbon micro and nanoparticles. Light transmission in the region of visible spectra of the films based on gelatin and polyvinyl alcohol was found to be almost independent of the wavelength. Carbon particles appeared to have no intrinsic absorption bands within the UV region. In the case of aggregation, nanotubes start to form clusters with an optical fractal structure, while the films display spatial fluctuations in transparency accompanied by deviations from the Bourguer-Lambert-Beer law. In contrast to nanoparticles, microparticles reduce the roentgen level of crystallinity of the films
A REVIEW ON COUNTER-ROTATING WIND TURBINES DEVELOPMENT
On a dynamic energy market
characterized by the constant energy demand
increase and economic as well as environmental
constraints, the study and development of efficient
conversion systems of wind’s energy has been
approached by a considerable number of researchers.
Given the modern economic and environmental
challenges regarding the energy production and
consumption, an advance in the research of
innovative or improved wind energy conversion
solutions has been registered. The objective of this
paper is to provide a comprehensive, but not
exhaustive overview of research achievements in
counter-rotating wind turbine systems development,
characterization and use. The review presents the
first theoretical results that led to the counterrotating
wind turbines development as well as the
related methods used for investigating their
performance. Valuable results have been found
within various studies, which are carried out for
different testing systems and conditions.
Furthermore, there is still need of extensive studies,
taking into account that the counter-rotating wind
turbines have to prove their reliability in real
operating conditions
Sciatic nerve schwannoma: Case report
Background. Schwannomas are common, benign tumors of the sheath of peripheral nerves. Sciatic schwannomas are rare. PURPOSE: We report a case of a large sciatic schwannoma, emphasizing the role of nerve preservation. Material & methods. A 54 years old female was admitted in our clinic for persistent right sciatalgia, and right L5 and S1 motor loss, symptoms lasting for almost 2 years. Patient underwent surgery in a different department, but the operation was stopped, because of excessive bleeding. Results Neurological examination revealed right sciatalgia, right L5 and S1 motor loss and diminished ankle jerk reflex, but failed to reveal relevant symptoms for disc herniation clinical diagnostic. Thigh CT-scan and MRI showed a large (70/80/75 mm) encapsulated, contrast-enhancing tumor, located in the middle third of the posterior thigh, in intimated relation with the sciatic nerve. Associated chronic myeloproliferative syndrome required oncological treatment and surgery postponement. We performed a subtotal resection of a large, solid tumor, infiltrating the sciatic nerve on 4 cm length, with anatomic integrity of sciatic preservation. Histopathological examination found cellular schwannoma. Outcome was favorable, and on follow-up examination the patients present no additional deficits and thigh CT-scan showed any evidence of tumor regrowing. Discussions & Conclusions. Diagnostic is challenging, in many symptoms are attributed to degenerative spinal pathology. Any persistent sciatlagia, with irrelevant lumbar MRI must raise the suspicion of a peripheral sheath tumor, and must be further investigated. Surgery is very demanding and associated co-morbidities must be treated prior surgery. Preserving the integrity of the sciatic nerve, assure favorable outcome, with no additional neurological deficits
GASSING OF THE ELECTRICAL INSULATING FLUIDS - A DETERMINANT FACTOR OF THE TRANSFORMERS SAFETY IN OPERATION
The influence on the quality of the electrical insulating fluids on the safety in operation of the transformers has been evaluated. After processing the comparative experimental data obtained by gas chromatography technique on 5 different sorts of electrical insulating fluids (a sort of vegetable oil with high oleic content and with addition of 0.5% antioxidant "functional model" - compared with two commercial sorts of mineral oil, 1 mainly vegetable commercial oil, 1 commercial synthetic ester), thermal aged in contact with electrical insulating paper and copper for electrical use, at 110 ± 3 °C for 1000 hours in closed vessels (limited access to atmospheric oxygen) it has been found that at the transformers filled with mineral oils, the risk of explosion and fire is approx. 10 times higher than those filled with synthetic or vegetal ester. It has also been found that the ageing of the insulation paper is approx. 15 times slower in the synthetic and natural ester than in the mineral oils normally used in transformers