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Publicatii proprii
Studies on terbium activated yttrium based tantalate phosphors
Terbium activated yttrium niobium tantalate phosphors were prepared by solid-state reaction and were characterized by photoluminescence measurements, X-ray diffraction and scanning electron microscopy. Photoluminescence (PL) of Y 0.95 Tb 0.05 Ta 1-x Nb x O 4 phosphors (x 0-1) are influenced by the host-lattice composition, degree of crystalline order and particle morphology and size. The effect of the morpho-structural properties on PL characteristics
Read moreStructural And Microstructural Investigation Of Cd x Zn 1-x In 2 S 4 Photocatalyst For Solar Hydrogen Production
A novel low temperature hydrothermal synthesis of II-III 2 -VI 4 (II = Zn, Cd; III = In; VI = S) mixed ternary chalcogenide semiconductors as visible photocatalysts for solar hydrogen production was performed. In this work, an X-ray diffraction based structural and microstructural study of chalcogenide semiconductors type Cd x Zn 1-x In 2 S 4 (0 ≤ x ≤ 1) is reported. The investigated powder samples were synthesized by a hydrothermal technique,
Read moreRIETVELD REFINEMENT OF POWDER X-RAY DIFFRACTION OF NANOCRYSTALLINE NOBLE METALS – TUNGSTEN TRIOXIDE
Tungsten trioxide powders were prepared from peroxo-tungstic acid (PTA) precursor obtained by sol-gel route, in aqueous medium. Two WO 3 samples were doped with noble metals, by "loading" them with silver and metallic palladium. The unit cell parameters of the WO 3 monoclinic phase, the effective crystallite mean size, D eff (nm), and the mean root mean square (rms) of the microstrains , 1/2 hkl ,were calculated by Rietveld refinement analysis. The
Read moreOCT4: Dynamic DNA binding pioneers stem cell pluripotency
OCT4 was discovered more than two decades ago as a transcription factor specific to early embryonic development. Early studies with OCT4 were descriptive and looked at determining the functional roles of OCT4 in the embryo as well as in pluripotent cell lines derived from embryos. Later studies showed that OCT4 was one of the transcription factors in the four-factor cocktail required for reprogramming somatic cells into induced pluripotent stem cells
Read moreEstudio de las tensiones en válvulas biplanas tipo mariposa
This paper presents the study of tensions developed as a result of the static actuation developed in a biplane valve, butterfly type, with a 1.500 mm diameter, loaded with a pressure of 1 MPa, using the finite element method, experimentally verified using a resistive electrical tensiometrical method. The proper knowledge of those valve types is very important in order to control the admissible losses.
Read moreTechnological aspects of assembling and processing narrow tubes
The paper presents the assembling, welding and processing of narrow tubes made of austenitic stainless steel used for the manufacturing of syringes and of food industry parts. At the same time, the paper discusses the various phenomena occurring during the processing of the materials previous to assembling and welding as well as during the welding operation proper. Following these studies and experiments, a suitable welding technology has been homologated
Read moreStudy of the materials used in the manufacturing of a tubular camshaft
In this workshop we elaborated several heat treatment tests to a large number of cams in order to achieve better results of mechanical resistance of a tubular camshaft made for an internal combustion engine. The most important results of our tests are represented in a few graphics and tables in this workshop
Read moreThe influence of the braking time on heat flow through the friction surfaces of the friction elements of disk brakes for railway vehicles
Disk brakes were first introduced on the suburban and urban coaches and high speed freight cars (V > 120 km/h) for the following reasons: shoe brakes reached their potential limits, especially at high speeds; the maintenance of disc brakes is cheaper; greater comfort; the friction coefficient of disk brake elements (friction pad and brake disc) presents lower variation in velocity and pressure; disk brakes present lower temperatures of friction surfaces.
Read moreMathematical model of three-phase induction machine connected to advanced inverter for traction system for electric trolley
This paper establishes a mathematical model of induction machine connected to a frequency inverter necessary to adjust the electric motor drive. The mathematical model based on the Park’s theory allows the analysis of the whole spectrum (electric car – frequency inverter) to drive the electric trolley bus made on ASTRA Bus Arad (Romania). To remove higher order harmonics, the PWM waveform of supply voltage is used, set in the general case. Operating
Read moreStructural properties of some transition metal highly doped carbon aerogels
Structural characterization of transition metal highly doped carbon aerogels obtained through the sol–gel polymerization process of the formaldehyde with the potassium salt of 2,4-dihydroxybenzoic acid, followed by metal ions exchange using Ni(II) and Cu(II) aqueous solutions, supercritical drying with liquid CO2 and carbonization at 1050 °C under inert atmosphere has been performed. Transmission electron microscopy (TEM), X-ray diffraction (XRD)
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