1,720,980 research outputs found
Use of Radiation Sorces with mercury isotopes for real – time highly sensitive and selective benzene determination in air and natural gas by differential absorption spectrometry with the direct Zeeman effect
No full textA new analytical portable system is proposed for the direct determination of benzene vapor in the ambient air and natural gas, using differential absorption spectrometry with the direct Zeeman effect and innovative radiation sources: capillary mercury lamps with different isotopic compositions (196Hg, 198Hg, 202Hg, 204Hg, and natural isotopic mixture). Resonance emission of mercury at a wavelength of 254 nm is used as probing radiation. The differential cross section of benzene absorption in dependence on wavelength is determined by scanning of magnetic field. It is found that the sensitivity of benzene detection is enhanced three times using lamp with the mercury isotope 204Hg in comparison with lamp, filled with the natural isotopic mixture. It is experimentally demonstrated that, when benzene content is measured at the Occupational Exposure Limit (3.2 mg/m3 for benzene) level, the interference from SO2, NO2, O3, H2S and toluene can be neglected if concentration of these gases does not exceed corresponding Occupational Exposure Limits. To exclude the mercury effect, filters that absorb mercury and let benzene pass in the gas duct are proposed. Basing on the results of our study, a portable spectrometer is designed with a multipath cell of 960 cm total path length and detection limit 0.5 mg/m3 at 1 s averaging and 0.1 mg/m3 at 30 s averaging. The applications of the designed spectrometer to measuring the benzene concentration in the atmospheric air from a moving vehicle and in natural gas are exemplified
Diamond synthesis using plasma chemical vapor deposition
No full textDimanta sintēze, izmantojot plazmas ķīmisko tvaiku nogulsnēšanas metodi.
Ē. Elksnis. Zinātniskie vadītāji Dr. ķīm. A. Vīksna., Dr. fiz. A. Skudra. Maģistra darbs, 65 lappuses, 64 attēli, 3 tabulas, 26 literatūras avoti, 1 pielikums. Latviešu valodā.
Maģistra darbā tiek pētītas plazmas ģenerēšanas metodes, plazmā notiekošās ogļūdeņražu pārvērtības un to pielietojums ķīmijā. Darba izstrādes procesā tika uzbūvēta līdzstrāvas plazmas iekārta, optimizēta tās darbība un veikta dimanta sintēze.
Darba rezultāti tika prezentēti starptautiskajā funkcionālo materiālu un nanotehnoloģiju (FM&NT) konferencē, 17.-20. aprīlī, 2012. gadā.
DIMANTA SINTĒZE, ĶĪMISKĀ TVAIKU NOGULSNĒŠANA, PLAZMAS ĢENERĒŠANAS METODES, PLAZMAS ĢENERĒŠANAS IEKĀRTAS, LĪDZSTRĀVAS PLAZMA, OGĻŪDEŅRAŽU PĀRVĒRTĪBAS PLAZMĀ.Diamond synthesis using plasma chemical vapor deposition. Ē. Elksnis. Scientific supervisors Dr. chem. A. Vīksna., Dr. phys. A. Skudra. Master thesis, 65 pages, 64 figures, 3 tables, 26 literature sources, 1 attachment. In Latvian.
In the Master Thesis plasma generation methods, hydrocarbons transformations in DC plasma and their applications in chemistry were described. DC plasma equipment was designed, operating parameters were optimized and synthesis of diamonds was realized.
Results of this work were presented at an International functional materials and nanotechnology (FM&NT) Conference, 17-20 April, 2012.
DIAMOND SYNTHESIS, CHEMICAL VAPOUR DEPOSITION, PLASMA GENERATING METHODS, PLASMA GENERATION EQUIPMENT, DIRECT CURRENT PLASMA, TRANSFORMATION OF HYDROCARBONS IN PLASMA
Spectroscopic investigation of Solar spectrum
No full textBakalaura darbā apskatīts debess difūzais starojums 45 grādu leņķī pret horizontu dienas gaitā. Papildus mērījumu datiem tiek izmantoti gaisa temperatūras un relatīvā mitruma meteoroloģiskie dati, lai veiktu to korelācijas pētījumu ar spektrālajiem uzņēmumiem. Dažādās dienās tiek novērtētas korelācijas starp spektra maksimuma intensitāti un integrālo spektru.
Tika novērots atšķirīgs difūzā debess starojuma spektrālais sadalījums no rīta, pusdienlaikā un vakarā. Arī tiešajam Saules starojumam tika iegūts spektrs, kas bija atšķirīgs no difūzā debess tarojuma spektra.
Darbā veikta spektrometra kalibrācija difūzā debess starojuma spektru mērījumiem absolūtajās vienībās, kas varētu kalpot tālākai atmosfēras starojuma kvantitatīvu lielumu noteikšanai.In the Bachelor Thesis a diffuse irradiation to Earth is observed onto a 45 degrees tilted surface. Additional to measurements, for correlation investigation purposes meteorological data of air temperature and relative humidity are used. On different days correlations between spectrum maximum intensity and integral spectrum are observed.
Differences in diffuse light spectrum where observed in the morning, at midday and in the evening. Also for the direct Sun radiation differences from diffuse light spectrum were registered.
Spectrometer calibration has been accomplished for irradiance absolute intensity measurements, which could further serve determining quantitative values of atmosphere
Spectroscopic diagnostics of high – frequency electrodeless low – temperature plasma
No full textDarbā tika veikti Fulcher-α (2-2)Q joslu sistēmas līniju spektrālo līniju intensitāšu mērījumi piecām dažādām ūdeņraža augstfrekvences bezelektrodu lampām, lai noteiktu plazmas temperatūru: trīs ūdeņraža-hēlija lampām, divām ūdeņraža-argona lampām ar kopējo spiedienu 1 Torr.
Spektrālo līniju relatīvās intensitātes tika reģistrētas ar spektrometru SPEX 1000M un lādiņu saites matricu Symphony CCD spektrālajā apgabalā – 620nm-630nm darbinot augstfrekvenču ģeneratoru ППБЛ-3M sešos dažādos režīmos pie 80 mA, 100 mA, 140mA, 160mA, 180mA un 200mA strāvas stipruma. Dati tika apstrādāti ar Origin-7.0 un Microsoft Excel programmu palīdzību. Tika noteikta spektrālo līniju intensitāšu atkarība no izlādes strāvas. Noteikta plazmas temperatūra pēc ūdeņraža molekulas Fulcher-α (2-2)Q joslas pirmo piecu līniju relatīvo intensitāšu sadalījuma.
Darbā arīdzan tika veikti spektrālo līniju kontūru reģistrēšana divām dažādām ūdeņraža augstfrekvences bezelektrodu lampām – vienai hēlija lampai un vienai argona lampai, kuras arī tika izmantotas Fulcher-a (2-2)Q joslu sistēmas spektrālo līniju intensitāšu mērījumos. Lai salīdzinātu iegūtās temperatūras vērtības, tika veikti spektrāllīniju kontūru mērījumi ar Fabrī-Pero interferometru He 667,8nm un Ar 772nm līnijām (pie piecām dažādām augstfrekvenču ģeneratora ППБЛ-3M strāvām ar stiprumu 100mA, 120mA, 140mA, 160mA, 180mA). No šīm kontūrām, izmantojot programmas Origin-7.0 un Microsoft Excel, tika atrasti Doplera paplašinājumi un atbilstoši arī plazmas temperatūras vērtības.In this work the Fulcher-α (2-2)Q band system line spectral intensity measurements have been done for five, different types of hydrogen containing high-frequency electrodeless gas discharge lamps to obtain plasma temperature: three hydrogen-helium lamps, two hydrogen-argon lamps with total pressure of 1 Torr.
Relative intensities of the emission spectral lines were measured by means of SPEX 1000M spectrometer and CCD camera Symphony in the wavelength range of 620 nm-630 nm using high-frequency generator ППБЛ-3M at six power regimes (80mA,100mA, 140mA, 160mA, 180mA and 200mA). The obtained data were analyzed by means of programs Origin-7.0 and Microsoft Excel. The plasma temperatures were obtained from the dependencies of the hydrogen molecule Fulcher-α (2-2)Q band system first five spectral line intensities.
For the comparison of the obtained temperature values, the spectral line shape measurements were made for two different hydrogen containing high-frequency electrodeless gas discharge lamps, which also were used in Fulcher-α (2-2)Q band system line spectral intensity measurements – one hydrogen-helium lamp and one hydrogen-argon lamp. The line shapes of He 667,8 nm and Ar 772 nm were recorded by means of Fabry-Perot interferometer at five power regimes (100mA, 120mA, 140mA, 160mA and 180mA). The analysis of the line shapes was done using Origin 7.0 and Microsoft Excel programs. Plasma temperature values were obtained from the Doppler broadening of the recorded line shapes
Measurements of SiO2 glass surface parameters by microscopy methods
No full textŠajā bakalaura darbā tiek pētīta dažādu apstrādes veidu ietekme uz SiO2 stikla virsmu. Tika ņemtas piecas dažādi apstrādātas augstfrekveņču bezelektrodu lampas. Pirmā lampa bija bez jebkādas apstrādes, otra un trešā tika ķīmiski apstrādātas ar tekilu un spirtu, ceturtā un piektā tika apstrādātas ar Ar un Se, un Ar un As plazmu. No lampām tika iegūti stikla virsmas paraugi. Attiecīgi to virsmas tika pētītas ar atomspēku mikroskopu (AFM) un rezultāti apstrādāti ar datu apstrādes programmatūru. Rezultātā tika iegūti dati par piecu dažādu apstrādes veidu ietekmi uz stikla virsmu un tās parametriem. Mērījumus ir iespējams apskatīties 2D, 3D un tabulas veidā ar raksturīgajiem parametriem. Būtiskākais secinājums- ka katrs apstrādes veids virsmu ietekmē citādāk.In this BSc thesis I am researching how different type of treatment changes surface of SiO2 glass. There were five differently treated high-frequency electrodeless light sources. First one was without treatment, second and third lamp was chemically treated with tequila and alcohol, fourth and fifth was treated with Ar and Se, and Ar and As plasma. To explore surface of those lamps, it was necessary to obtain glass samples. Then those samples were measured by atomic force microscope and processed with analytical data program. In the end I got results about five differently treated SiO2 glass surfaces. It is possible to see those results in 2D, 3D or in table with characteristic parameters. The main conclusion in my opinion is- every treatment method changes surface and its characteristics
Spectroscopic measurements of Mercury-containing high-frequency electrodeless lamps
No full textDarba gaitā ar speciālās infrasarkanās kameras un iepriekš izstrādātās termoregulācijas sistēmas palīdzību tika precizēts temperatūras diapazons, kurā augstfrekvences bezelektrodu lampas aukstākais punkts paliek kontaktā ar termostatu.
Tika veikti vairāki uzlabojumi paštaisītai termoregulācijas iekārtai, kas paredzēta augstfrekvences bezelektrodu lampu (ABL) emisijas spektra pētījumiem atkarībā no ABL aukstākā punkta temperatūras. Ņemot vērā precizēto temperatūras diapazonu, tika izmainīts spektru uzņemšanas algoritms, kas padarīja procesu vieglāku, ātrāku, bet pašus mērījumus precīzākus.
Pēc padarītajiem uzlabojumiem tika uzņemti emisijas spektri 6 dažādām ABL, kuras pildītas ar Hg un inertās gāzes maisījumu.
Tika konstatēts, ka, pieaugot temperatūrai, emisijas intensitāte lampām mainas ar dažādu ātrumu. Lampām ar lielāku inertās gāzes spiedienu, vai ar smagāku inerto gāzi, 184.9 nm dzīvsudraba rezonanses līnijas intensitātes izmaiņa ir lēnāka un izskatās lineārāka.During this work, using special infrared camera and previously developed thermoregulation system the correct experimental temperature range has been determined, where the “cold spot” of high frequency electrodeless lamp (HFEDL) remains in contact with thermostat.
Several improvements have been made to the self-developed thermoregulating system, which can be used for HFEDL emission spectra investigation depending on “cold spot” temperature. According to the adjusted experimental temperature range the algorithm of spectra registration has been modified, so the process of data accumulation became faster and simpler, and the accuracy of mesuraments was increased.
The emission spectra of 6 different HFEDLs with Hg and inert gas mixture were obtained after the improvements have been made.
It was found that by increasing the cold spot temperature the emission intensity increases. For lamps with higher inert gas pressure or a heavier inert gas the 184.9 nm mercury resonance line intensity changes are slower and look more linear
Spektrāllīniju profilu analīze zemtemperatūras plazmā, risinot apgriezto nekorekto problēmu
No full textPromocijas darbs ir veltīts zemtemperatūras plazmas diagnostikas metodes attīstīšanai, augstfrekvences bezelektrodu lampām (ABL). Darbā tika izstrādāta jauna metode spektroskopisko datu apstrādei un reālo spektrāllīniju kontūru noteikšanai, risinot nekorekto apgriezto uzdevumu, kas balstās uz Tihonova regularizācijas algoritmu. Metode tika testēta aprēķinot patiesās profilu formas izmantojot eksperimentāli iegūtas Hg līnijās, emitētas no specialas formas mikro ABL. Tika pierādīts, ka aparatūras funkcijas neņemšana vērā zemtemperatūras plazmas gadījumā var ieviest lielu neprecizitāti, nosakot profilu formu un platumu un, sekojoši, ABL temperatūru. Tika analizēta arī atkarība no bufergāzes veida. Šī darba rezultāti tika nopublicēti 3 zinātniskas žurnālos (SCOPUS), 8 konferenču rakstu krājumos (5 - SCOPUS) un 8 tēzes. Atslēgvārdi : nekorektais apgrieztais uzdevums, regularizacija, spektrāllīnijas reālo profilu noteikšana, ABL diagnostikaThis thesis is dedicated to the development of the diagnostic methods of the low temperature plasma in case of high - frequency electrodeless discharge lamps (HFEDLs) . The new method of the restoring the real profile of the measured spectral lines by means of ill posed inverse task solution based on Tikhonov regularizing algorithm was developed in this thesis. The method was tested using experimental Hg spectral line shapes emitted from special design microsize HFEDLs. The influence of the instrumental function on the form and FWHM of the lines profiles were analyzed. It was proved that the neglecting the instrument function gives huge error for the FWHM estimation in the case of low – pressure or cold plasma. The influence of the type of buffer gas was investigated also. The results of this work are presented in 3 scientific journals (all in Scopus), 8 Proceedings of International Conferences (5 - Scopus) and 8 books of the abstracts. Keywords: ill posed inverse task, regularzaton, restoring the real profile of the spectral lines, diagnostic of HFEDL
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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