This paper presents a solution for measurement automation of spectral characteristics in near and mid-infrared region using the Oriel 77250 monochromator and a general-purpose digital storage oscilloscope. To automate the task a USB controlled stepper motor was attached to the monochromator. The stepper motor and data acquisition through the oscilloscope is controlled from the host computer by means of dedicated LabVIEW software. The acquired data from the detector are processed in real-time and displayed in a form of a graph. Both raw and processed data are then saved for their later post-processing. This solution enables to make measurements at the maximum speed of 1.1 wavelength steps per second. In the first diffraction order the minimum wavelength step is 0.05 nm and the precision is ±0.05 nm. and V práci je představeno řešení automatizace měření spektrálních charakteristik v blízké a střední infračervené oblasti s využitím monochromátoru Oriel 77250 a digitálního paměťového osciloskopu. Pro automatizaci měření byl k monochromátoru připojen krokový motor ovládaný přes USB rozhraní. Krokový motor a sběr dat z digitálního osciloskopu je řízen počítačem pomocí vlastního programu napsaného ve vývojové prostředí LabVIEW. Získaná data z detektoru jsou zpracována v reálném čase a zobrazena ve formě grafu. Jak nezpracovaná, tak zpracovaná data jsou uložena v počítači pro případné pozdější využití. Toto řešení umožňuje provádět měření maximální rychlostí 1,1 bodů spektra za sekundu. V prvním difrakčním řádu je minimální krok měření 0,05 nm a přesnost ±0,05 nm.
This paper is concerned with the determination of the relationship for the calculation of the discharge coefficient at free overflow over a rectangular sharp-edged broad-crested weir without lateral contraction. The determination was made on the basis of new measurement in a range of the relative thickness of the weir from 0.12 to 0.30 and newly in a large range of relative height of the weir extremely from 0.24 to 6.8 which greatly expands the application possibilities of low weirs. In addition, the effects of friction and surface tension on the value of the discharge coefficient were evaluated as well as the effect of the relative thickness of the weir. The new equation for discharge coefficient, expressed using the relative height of the weir, was subjected to verification made by an independent laboratory which confirmed its accuracy.
Mid-infrared region (2-8) μm is currently in the focus of laser physics, which is trying to develop new materials capable of generating coherent laser radiation in this region. This point of interest is connected to the so called infrared atmospheric window which offers new possibilities for solid-state lasers to be used as radars, LIDARs, tools for atmosphere diagnostics, etc. One of these new materials is the dysprosium doped lead-thiogallate (Dy:PbGa2 S4 ). In this article, we present brief characteristics of this laser active medium from the point of view of laser physics and we demonstrate the output radiation characteristics of three laser systems with dysprosium doped lead-thiogallate as their active media generating radiation at 2400 nm, 4300 nm a 5400 nm. The spatial structure, energy, impulse length and emission spectra of the output radiation were determined. and Stredná infračervená oblasť (2-8) μm je v súčasnosti terčom záujmu laserovej fyziky, ktorá sa snaží vyvinúť nové materiály, ktoré by mohli poskytovať koherentné laserové žiarenie v tejto oblasti. Tento záujem sa spája s existenciou tzv. infračerveného atmosférického okna, ktoré otvára nové možnosti aplikácií laserov generujúcich žiarenie v tejto oblasti ako sú radary, LIDARy, prostriedky pre diagnostiku atmosféry a podobne. Jedným z týchto nových materiálov majúcich takéto vlastnosti je dyspróziom dopovaný olovo-thiogalát (Dy:PbGa2 S4 ). V tomto článku prezentujeme stručnú charakteristiku tohto laserového aktívneho prostredia z pohľadu laserovej fyziky a demonštrujeme vlastnosti troch laserových systémov, obsahujúcich Dy:PbGa2 S4 ako aktívne médium, generujúcich žiarenie na vlnových dĺžkach 2400 nm, 4300 nm a 5400 nm. Výstupné žiarenie charakterizujeme z hľadiska priestorovej štruktúry, energie, dĺžky impulzu a emisného spektra.
Modelling of supercritical turbulent flow in an open channel with transversal ribs on its bottom was concentrated particularly on the development of flow separation behind ribs and on the corresponding changes of free surface. Further, the pressure drag of individual ribs was investigated including its dependence on the rib spacing, as well as the origin of secondary flow near the side walls of the channel behind ribs. Numerical results obtained by the software ANSYS CFX 11,0 were compared with experiments carried out by means of LDA and PTV techniques in free-surface water experiments carrid out by means of LDA and PIV techniques in free-surface water channel 200 x 200 mm with one or two transversal ribs 10 x 10 mm with various spacing. and Obsahuje seznam literatury
Modelling of turbulent flow in curved channels and diffusers of rectangular cross-section was aimed at the evolution of secondary flow and origin of flow separation and their connection with energy losses and pressure recovery. Results of numerical simulations carried out using software CFX TASCflow 2.12 were compared with experiments made in a water channel. Turbulent flow in diffusers of rectangular cross-section with the constant channel height, flow turn angle 90 deg and area ratio AR = 1.5 was investigated. Numerical simulation was carried out for flow in diffusers with the cylindrical inner wall and with the cylindrical centreline. Turbulent flow in a curved channel of constant cross-section was investigated for comparison. Further, the effect of the inner wall radius on the character of flow in the diffuser was studied. Flow separation occurs on the inner wall of the channel before the bend exit and its extent is restricted to the central part of the channel due to secondary flow going from the sidewalls to the channel axis. The extent of separation region and consequently the energy losses decrease with the increasing radius of the inner wall curvature. and Obsahuje seznam literatury
The article deals with the characteristics and tunability possibilities of radiation generated by diode (1452 nm) pumped Er:YAG laser. The laser was operated in pulsed regime (pulse length of 10 ms, repetition rate of 10 Hz) at the wavelength of 1645 nm; the maximum mean laser output power and maximum slope efficiency were 67.1 mW and 48.8 %, respectively. Output radiation tunability in the eye-safe region was realized by a birefringent filter placed inside of the laser resonator. Wavelength tunability was reached in four spectral regions with maxima centered at wavelengths of 1616, 1633, 1645 and 1657 nm. The broadest tunability was 6.4 nm (reached at 1616 nm laser transition) and a corresponding maximum output power was 37.5 mW. and Článek se zabývá charakteristikami a možností přeladění záření generovaného diodově (1452 nm) čerpaným Er:YAG laserem. Laser byl provozován v pulzním režimu (délka pulsu 10 ms, opakovací frekvence 10 Hz) na vlnové délce 1645 nm, maximální střední výkon laseru byl 67,1 mW a maximální diferenciální účinnost 48,8 %. Laditelnosti výstupního záření v oku bezpečné oblasti spektra bylo dosaženo pomocí dvojlomného filtru uvnitř laserového rezonátoru. Přeladitelnosti bylo dosaženo ve čtyřech oblastech s maximy na vlnových délkách 1616 nm, 1633 nm, 1645 nm a 1657 nm. Nejširší laditelná oblast dosahovala šířky 6,4 nm a maximální odpovídající generovaný výkon záření byl 37,5 mW.
The paper deals with selected procedures used to calculate the shape of compact nappe during free overfall from a smooth horizontal channel with rectangular cross section. Calculated and measured water surface and velocity conditions in the end section, the level of water surface upstream in front of the end section and the shape of the compact part of an overfall nappe are described for a particular compared case.
The main goal of this work was to characterize the spectroscopic properties (absorption, fluorescence, and lifetime) of the samarium ion in the yttrium-aluminum-garnet matrix. The Sm:YAG crystals with various samarium concentrations (1, 3, 6.4, 10, 15 and 20 at.% Sm/Y) were produced by the edge-defined, film-fed growth technique. Absorption characteristics were investigated in the spectral range of 185 nm - 3100 nm with detailed measurements in the near-infrared range of 1058 to 1125 nm. The results indicate that the specific absorption properties of the Sm:YAG crystal could be advantageously used to an absorb of parasitic fluorescence around 1064 nm (dominant emitted wavelength of Nd:YAG laser). The dependence of lifetime on the samarium ions concentration in the YAG matrix was proven. and Hlavním cílem této práce bylo experimentálně zjistit spektroskopické vlastnosti iontu samaria v matrici ytrium-aluminium-granátu. Pomocí metody EFG byly vyrobeny krystaly s různou koncentrací samaria (1, 3, 6,4, 10, 15, 20 at.% Sm/Y). Absorpční charakteristiky byly zkoumány ve spektrálním rozsahu 185 nm - 3100 nm, s detailním měřením v oblasti vlnové délky 1064 nm. Dále byly proměřeny emisní závislosti a doba života.