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Trace Detection and Photothermal Spectral Characterization by a Tuneable Thermal Lens Spectrometer with White-Light Excitation
Humberto Cabrera, Dorota Korte, Mladen Franko, 2018, izvirni znanstveni članek

Opis: In the thermal lens experimental set-up we replaced the commonly employed pump laser by a halogen lamp, combined with an interference lter, providing a tuneable, nearly monochromatic pump source over the range of wavelengths 430–710 nm. Counter-propagating pump and probe beams are used and a 1 mm path-length sam- ple cell together with the interference lter makes an optical cavity, providing ampli cation of the thermal lens signal, which leads to enhancement of the measurement sensitivity, and enables detection of absorbances on the order of 5×10− 6. Ampli ed thermal lens signal allows us to replace the typical lock-in ampli er and digital os- cilloscope with a silicon photodetector, Arduino board, and a personal computer, offering the possibility for a compact, robust and portable device, useful for in- eld absorption measurements in low concentration or weakly absorbing species. The use of a white light source for optical pumping, an interference lter for wavelength selection and direct diagnostic of the thermal lens signal increase the versatility of the instrument and simpli- es substantially the experimental setup. Determination of Fe(II) concentrations at parts per billion levels was performed by the described white-light thermal lens spectrophotometer and the absorption spectrum for 50μg/ L Fe(II)-1,10-phenanthroline was well reproduced with an average measurement precision of 4%. The obtained limits of detection and quantitation of Fe(II) determination at 510nm are 3μgL− 1 and 11μgL− 1, respectively. The calibration curve was linear in the concentration range of LOQ-500μgL− 1 with reproducibility between 2% and 6%, con rming that this instrument provides good spectrometric capabilities such as high sensitivity, tune- ability and good reproducibility. In addition, the versatility of the instrument was demonstrated by recording the photothermal spectrum of gold nanostructured material and determination of excitation wavelength with most ef cient optical to thermal energy conversion, which differs considerably (cca 100 nm) from the absorption maximum of the investigated sample.
Ključne besede: thermal lens spectrometry, Fe(II) determination, photothermal technique, multi-wavelength excitation
Objavljeno v RUNG: 21.02.2018; Ogledov: 3962; Prenosov: 0
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Portrait of light
Marco Pelos Spagno, 2017, diplomsko delo

Opis: This work aims to research the basic structure of lighting in portraits in a controlled light situation. After providing a brief historical introduction to define where modern lighting comes from, I will describe and analyse the tools used to modify the light in a studio and the procedure to follow before a portrait session. I will present a series of images shot in a studio, and I will touch upon most possible basic lighting setups in a portrait session, from most simple ones to some more complex ones, describing the set of lights, the type of modifiers used, and the effects that the light can have on a viewer. My final aim is to build up a collection of light setups that can be helpful to anyone who wants to approach portrait photography and the studio workflow, not aiming to build a manual, but just providing a report on my personal research and study.
Ključne besede: portrait, light, studio, study, technique, photography, bw, model, modifiers, controloflight, history, paintings, art, exposure
Objavljeno v RUNG: 29.11.2017; Ogledov: 4734; Prenosov: 314
.pdf Celotno besedilo (6,53 MB)
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Experimental sessions: digital lock-in photothermal shadowgraph method
Dorota Korte, Angel Cifuentes, vabljeno predavanje na konferenci brez natisa

Ključne besede: Photothermal beam deflection technique, photothermal shadowgraph method
Objavljeno v RUNG: 13.03.2017; Ogledov: 4460; Prenosov: 0
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Nataša Smrekar, 2016, magistrsko delo

Opis: In my master's thesis, I have focused on radon gas in 43 buildings used for different purposes (23 schools, 3 kindergartens, 16 offices and a residential house) in which preliminary measurements had shown higher concentrations of radon gas. I carried out measurements of radon and short-lived radon products whilst simultaneously employing different measurement techniques. In all 43 buildings, I measured the instantaneous concentration of radon by using scintillation cells; in 18 buildings, I additionally measured the average concentration of radon by using solid state nuclear track detectors and in 10 buildings, I measured concentration retrospectively with solid state nuclear track detectors. In four selected buildings (a school, a kindergarten, an office and a residential house), I carried out the measurements by using all of the available equipment. I monitored the daily fluctuations of concentration of radon and short-lived radon products by using continuous monitors in 14 buildings. This is how I obtained the factor of radioactive equilibrium between radon and its short-lived products. Based on the results obtained, I calculated the effective doses. As the basis for calculating the doses, I used the instantaneous and average concentrations of radon and the equilibrium factor taken from literature (0.40) or own measurements. I compared the doses and critically evaluated them. In contrast to the previous research, I researched radon exclusively in areas with increased risk for radon. I studied the influence of the working regime on the concentration of radon in different working environments (i.e. a school, a kindergarten and an office).
Ključne besede: Radon, short-lived radon products, measurement technique, scintillation cell, solid-state nuclear track detector, retrospective detector, equilibrium factor, effective dose, comparison.
Objavljeno v RUNG: 28.09.2016; Ogledov: 6034; Prenosov: 282
.pdf Celotno besedilo (1,86 MB)

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