Browsing by Author "Evtodiev, S."

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Caracteristici numerice şi legităţi statistice în teoria fiabilităţii [Articol]
(Universitatea de Stat „Alecu Russo“ din Bălţi, 2015) Evtodiev, S.; Veleșcu, D.; Evtodiev, I.
Articolul dat se referă la caracteristicile numerice ale fiabilităţii şi repartiţia funcţiilor de fiabilitate după legităţile statistice din teoria fiabilităţii. Am studiat mai în detaliu Legea Gamma şi Legea Weibull cu 1 parametru, 2 parametri şi 3 parametri.
Emission spectra for analysing elements in clues using optical method [Articol]
(Universitatea de Stat „Alecu Russo“ din Bălţi, 2014) Evtodiev, S.; Koss, A.; Evtodiev, Igor
The following research was dedicated to the investigation of emission spectra of different elements and their use in the analysis of clues. The used equipment was a spectrometer, the "Red Tide USB-650", and an application called "Overture". The spectrometer has a spectral range from 350 nm to 1000 nm. It’s a very lightweight and portable device,not taking up much space and weighting only 190 g. The sensitivity of the device is 75 photons at a wavelength of 400 nm. The optical resolution of the spectrometer is 2 nm, while the program can display accurate graphs with a resolution of up to 0.1 nm. The spectrometer’s integration time ranges from 3 ms to up to 65 seconds, but typically it d oesn’t exceed 15 seconds. For very precise data recording the spectrometer can also use the optic fibres. The used program has a library of emission spectra of different elements. The experiment is performed by making the substance to emit photons by exciting it. The light from this substance is received by the spectroscope and the data are transmitted to the computer. The program generates an "Intensity-Wavelength" graph right away. But to analyse and to detect elements in clues a graph is not the only required thing. Luckily, we have access to the emission spectra library built into the program. Those can be enabled and disabled to detect if the given element is present in the earlier analysed substance.Such a method can be used to detect elements in clues using spectral analisys at remarkable speeds and accuracies.
The experimental study of real and ideal harmonic oscillators [Articol]
(Universitatea de Stat „Alecu Russo“ din Bălţ, 2014) Koss, A.; Evtodiev, S.; Evtodiev, Igor
The following research was dedicated to studying and experimenting with harmonic oscillators of all kinds. The used equipment was a portable computer, the “PASCO Spark”, a force sensor, 3 different springs and weights. The portable computer is responsible for storing the data received from the force sensor, and constructing a “Force-Time” graph. The force sensor has a range of ±50 N, an accuracy of 0.1 N and a recording speed of up to 1000 Hz. It is also equipped with a reset button to automatically set it to 0 N. The springs used in the experiment differed in damping. The first spring had a very low damping coefficient, so after the weight was released they continued oscillating for a very long time, fading away only very slightly. The second spring had a medium damping coefficient, so the time it took for the oscillations to fade was much shorter, then with the first spring. The third spring however had a very high damping coefficient, so the oscillations only continued for about 6 seconds. The experiment itself was performed by hanging a weight on the spring, and starting the data recording as soon as the weight is dropped. In all 3 experiments the data was recorded at a frequency of 100 Hz. Afterwards, the computer built “Force-Time” graphs for every experiment. This allowed us to visualize the difference between the 3 springs. The computer used in the experiment has a very useful ability of generating functions for graphs. This can be done in order to study ideal harmonic oscillations. The function generated from the graph continues forever, and can be used for further research in the field of beats, which are automatically calculated and simulated by the computer. Thanks to the precise data recording equipment human errors can be minimized, which leads to very little inaccuracies in calculations.
INVESTIGAŢII EXPERIMENTALE ASUPRA UNOR CARACTERISTICI FIZICO-CHIMICI DE DETERMINARE A CALITĂŢII APEI
(Universitatea de Stat „Alecu Russo“ din Bălţi, 2014) Luchian, E.; Evtodiev, S.
Caracteristicile fizico-chimice joacă un rol esențial la determinarea calității apei. Unele din aceste caracteristici sunt: conductivitatea electrică, concentrația ionilor de hidrogen, oxigenul dizolvat. Determinarea conductivității apei oferă informație asupra gradului de impuritate în eşantioanele analizate. Cercetările asupra determinării concentraţiei ionilor de hidrogen reprezintă gradul de aciditate sau alcalinitate a apei, caracteristici care direct influienţează sănătatea populaţiei. Lipsa de oxigen din apă duce la pierderea caracterului de prospeţime, apa devenind nepotabilă.Caracteristicile fizico-chimice experimental au fost investigate cu ajutorul senzorului multifuncţional de determinare a calităţii apei PS-2169.
Regulation of radiation transmittance through electro-optic technologies [Articol]
(Universitatea de Stat „Alecu Russo“ din Bălţi, 2014) Vizitiv, G.; Calancea, L.; Evtodiev, Igor; Evtodiev, S.
There are three fundamental mode of heat transfer: diffusion, convection and radiation. Although our modern windows are really good at blocking heat transferred from diffusion and convection, a lot of energy is able to pass through them in the form of electro-magnetic waves, mostly in the visible and infrared spectrum. It has been proven that even transparent curtains will afford adequate protection from optical radiation in the ultraviolet region, but that all of them will transmit high percentages of infrared radiation, while the solar irradiance is high in the infrared spectrum.Using a system of polarizers active specifically for the range of the IR spectrum with the highest irradiance and a liquid crystal cell (LCC) we can alter the energy transmittance of windows without blocking visible light. This way, using less energy than usual conditioning systems we can control the temperature of the environment, without rendering our windows opaque in the visible spectrum. This is achieved by using a system of combined Kerr and Pockels cells, with high electro-optic constant, low energy expenses and longitudinal applied voltage.