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81.
Quarter wave plates are optical elements commonly used in photoelasticity to obtain circularly polarized light. They divide the incident light field into two linearly polarized orthogonal components with a phase difference of a quarter of the light wavelength. Due to the tolerance in manufacturing, however, the actual phase shifting produced by the plates is affected by an error, which noticeably influences the photoelastic measurements performed by means of various automated methods. This paper presents a technique, based on the phase stepping method, for the full field automatic evaluation of the quarter wave plate error. 相似文献
82.
A reliable and sensitive analytical optical method for the determination of phosphorous in oceanographic and environmental materials does not exist. In this work, a novel hydride generation method was used to form phosphine from a sample containing phosphate mixed with 7% sodium borohydride. By heating the mixture to 500 °C, phosphine was reproducibly generated and collected in a cold trap. Phosphine was then introduced into an ICP where several atomic emission lines for phosphorous were observed. Copper emission did not spectrally interfere with phosphorous atomic emission with this hydride generation-ICP-AES method. This hydride generation method allows the use of small sample volumes (< 5 μL). 相似文献
83.
84.
Chloride was determined at nanogram levels by adding excess of indium to the sample introduced into a graphite furnace and measuring the laser induced molecular fluorescence of indium chloride. The diatomic molecules of indium chloride were excited by a pulsed dye laser at 267 nm and fluorescence was measured at 359 nm. The effects of various parameters including amount of indium added, furnace thermal conditions and presence of concomitants were also studied. A linear calibration in the range of 0.025-1.25 ng and a detection limit of 17 pg of chloride were obtained under optimum conditions. The analytical usefulness of the method was checked by determining the chloride content in National Institute of Standards and Technology, Standard Reference Materials 1571a and 1571b Orchard Leaves. 相似文献
85.
The performance of graphite-tube electrothermal atomizers is evaluated for laser-excited atomic-fluorescence spectrometry for several elements. Three pulsed laser systems are used to pump tunable dye lasers which subsequently are used to excite Pb, Ga, In, Fe, Ir, and Tl atoms in the hot graphite tube. The dye laser systems used are pumped by nitrogen, copper vapour and Nd:YAG lasers. Detection limits in the femtogram and subfemtogram range are typically obtained for all elements. A commercial graphite-tube furnace is important for the successful utilization of the laser-based method when the determination of trace elements is intended, especially when complicated matrices may be present. 相似文献
86.
Armstrong TA Bettoni D Bharadwaj V Biino C Borreani G Broemmelsiek D Buzzo A Calabrese R Ceccucci A Cester R Church MD Dalpiaz P Dalpiaz PF Dibenedetto R Dimitroyannis D Fabbri MG Fast JE Gianoli A Ginsburg CM Gollwitzer KE Hahn AA Hasan MA Hsueh SY Lewis RA Luppi E Macrí M Majewska AM Mandelkern MA Marchetto F Marinelli M Marques JL Marsh W Martini M Masuzawa M Menichetti E Migliori A Mussa R Palestini S Pallavicini M Pastrone N Patrignani C Peoples J Pesando L Petrucci F Pia MG Pordes S 《Physical review D: Particles and fields》1993,48(7):3037-3044
87.
Armstrong TA Bettoni D Bharadwaj V Biino C Borreani G Broemmelsiek D Buzzo A Calabrese R Ceccucci A Cester R Church M Dalpiaz P Dalpiaz PF Dibenedetto R Dimitroyannis D Fabbri M Fast J Gianoli A Ginsburg CM Gollwitzer K Hahn A Hasan MA Hsueh S Lewis R Luppi E Macrí M Majewska AM Mandelkern M Marchetto F Marinelli M Marques J Marsh W Martini M Masuzawa M Menichetti E Migliori A Mussa R Palestini S Pallavicini M Pastrone N Patrignani C Peoples J Pesando L Petrucci F Pia MG Rapidis PA Ray R Reid J 《Physical review letters》1993,70(20):2988-2991
88.
We show that cavitation of a solution of thorium-228 in water induces its transformation at a rate 104 times faster than the natural radioactive decay would do. This result agrees with the alteration of the secular equilibrium of thorium-234 obtained by a Russian team via explosion of titanium foils in water and solutions. These evidences further support some preliminary clues for the possibility of piezonuclear reactions (namely nuclear reactions induced by pressure waves) obtained in the last ten years. 相似文献
89.
Since the glass is a birefringent material, the analysis of residual stress in glass is usually carried out by means of photoelastic methods. This paper considers the automation of the “test fringes” method which is based on the use of a Babinet compensator or of a beam subjected to bending. In particular, two automated methods are proposed: the first one is based on the use of the centre fringe method in monochromatic light and the second one is based on the use of RGB photoelasticity in white light. The proposed methods have been applied to the analysis of membranal residual stresses in some tempered glasses, showing that they can effectively replace manual methods of photoelastic analysis of residual stresses in glass. 相似文献
90.
The intensity of spectra emitted by hollow copper cathodes with and without the superposition of 2450-MHz microwaves was studied under different operating conditions with argon as the filler gas. The hollow-cathode discharge was operated at 25–200 mA, with argon pressures ranging from 166 to 690 Pa. The intensities of the copper spectral lines are usually higher in the presence of microwaves, whereas the argon lines are weaker. The differences in the copper spectral lines with and without microwaves increase with increasing pressure of the filler gas and decreasing current. Analogous conclusions were reached for aqueous solutions of gold and silver ions placed in the cathode cavity and dried prior to discharge. The suitability of the method for improving the detection limits obtainable with the hollow-cathode discharge could thus be demonstrated. 相似文献