Search results for "beam"
showing 10 items of 2126 documents
Resonant X-Ray Scattering of Biological Systems
1987
Nearly all synchrotron radiation laboratories at high energy electron storage rings put enormous effort into the developement of resonant (anomalous) X-ray scattering techniques. So does the Hamburger Synchrotronstrahlungslabor (HASYLAB) at Hamburg. One of these intruments which is built in cooperation with the university of Mainz at the beam line A1 of the storage ring DORIS. How does the physics of resonant scattering enter into the design of the X-ray instrument.
INTEREST OF BEAM QUALITY IN MATERIALS TREATMENTS BY HIGH POWER LASER
1991
The aim of the study is the increasing of performances of the YAG Lasers. For this, we use the principle established by Boquillon and Taisne : an X geometry of the resonator. In this case the number of emitted modes is lower than for the linear conception and the beam quality is greater. So, reached power density can be 7 times higher than for the classical cavity and consequently cutting speed can be about 2 times higher than for the linear one. Concerning welding, thick materials need a lot of energy and our system is not competitive. however it exists an interest for thin joining with an easely formed key hole and later a more important penetration.
On the moving load problem in beam structures equipped with tuned mass dampers
2017
This paper proposes an original and efficient approach to the moving load problem on Euler–Bernoulli beams, with Kelvin–Voigt viscoelastic translational supports and rotational joints, and in addition, equipped with Kelvin–Voigt viscoelastic tuned mass dampers (TMDs). While supports are taken as representative of external devices such as grounded dampers or in-span supports with flexibility and damping, the rotational joints may model rotational dampers or connections with flexibility and damping arising from imperfections or damage. The theory of generalised functions is used to treat the discontinuities of the response variables, which involves deriving exact complex eigenvalues and eigen…
Ex vivo measurement reliability using two different cbct scanners for orthodontic purposes
2012
Background There are many cone beam computed tomography (CBCT) scanners available on the market: detector technology, algorithm precision, and scanner settings influence image quality. The aim of this study was to compare the accuracy of linear measurements made on images of the same sample obtained using two different CBCT scanners. Methods Twenty-eight linear measurements between orthodontic anatomical landmarks that were marked with gutta-percha points on a fresh sacrificed lamb head were taken three times. The head was scanned with two CBCT scanners using different scanning parameters. Digital Imaging and Communications in Medicine (DICOM) images were reconstructed and the same measurem…
Characterisation of two new radiochromic gel dosimeters TruView™ and ClearView™ in combination with the vista™ optical CT scanner: A feasibility study
2018
This study aims at characterising the properties of TruView™ and ClearView™ two new gel dosimeters (Modus Medical Devices Inc.) and at studying the feasibility of relative dosimetry using these dosimeters and the Vista™ Optical CT scanner to accurately evaluate dose.In this work, we investigated key dosimetric aspects (dose response, energy and dose rate dependence) and stability of these radiochromic gels initiated in preliminary works (Huet et al., 2017; Colnot et al., 2017) using spectrophotometric measurements. Moreover, by mean of optical CT scanning (Vista™), their performances to measure relative depth dose (PDD) and cross profiles were analysed.TruView™ and ClearView™ present a line…
Differential cross section for the reaction 2H(γ, p)n from 133 to 158 MeV
1991
The cross section for the reaction 2H(γ, p)n has been measured at laboratory photon energies Eγ = 133−158 MeV and c.m. angles between 30° and 150°. The reaction was induced by a tagged bremsstrahlung photon beam incident on a liquid deuterium target. The uncertainty in the absolute cross sections is ⩽ 5%. There is now reasonable agreement between recent measurements in this energy region and the overall data set now defines the cross section sufficiently well to provide a test of current models of the reaction.
Regge phenomenology in π0 and η photoproduction
2017
The $\ensuremath{\gamma}N\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}N$ and $\ensuremath{\gamma}N\ensuremath{\rightarrow}\ensuremath{\eta}N$ reactions at photon beam energies above 4 GeV are investigated within Regge models. The models include $t$-channel exchanges of vector ($\ensuremath{\rho}$ and $\ensuremath{\omega}$) and axial-vector (${b}_{1}$ and ${h}_{1}$) mesons. Moreover, Regge cuts of $\ensuremath{\rho}\mathbb{P},\phantom{\rule{0.28em}{0ex}}\ensuremath{\rho}{f}_{2},\phantom{\rule{0.28em}{0ex}}\ensuremath{\omega}\mathbb{P}$, and $\ensuremath{\omega}{f}_{2}$ are investigated. A good description of differential cross sections and polarization observables at photon beam energies fr…
Electron Emission of Pt: Experimental Study and Comparison With Models in the Multipactor Energy Range
2016
Experimental data of secondary emission yield (SEY) and electron emission spectra of Pt under electron irradiation for normal incidence and primary energies lower than 1 keV are presented. Several relevant magnitudes, as total SEY, elastic backscattering probability, secondary emission spectrum, and backscattering coefficient, are given for different primary energies. These magnitudes are compared with theoretical or semiempirical formulas commonly used in the related literature.
High-sensitivity U–Pb rutile dating by secondary ion mass spectrometry (SIMS) with an O2+ primary beam
2012
Abstract We present a secondary ionization mass spectrometry (SIMS) technique for U–Pb geochronology of rutile at high spatial resolution and sensitivity using an O2+ primary ion beam coupled with surficial O2 gas deposition (O2 flooding). The O2+ beam is ~ 10 × more intense than conventionally applied O− or O2− beams at the same lateral resolution. Natural and synthetic rutile was determined to be conductive under O2+ bombardment, permitting higher excavation (sputter) rates than conventional SIMS using negatively charged O-beams without detrimental effects of sample charging. The main advantage of O2+ is rapid sputtering at shallow primary ion penetration depths. This minimizes the contri…
Epoche d'impianto e sistemi di allevamento per il fagiolo "Badda"
2010
The bean landrace"Badda" has been cultivated since long ago in the Madonie mountains in the northern side of Sicily.It is characterized by a bush indeterminate habit and comprises two ecoty termed 'Badda bianca ' and 'Badda nera' according to the seed colour. This paper describes the results of a study on the effects of four sowing dates (June 15 and 30, July 15 and 30) and two vertical training sustems 8a frame of Arundo donax dry canes or a trellis consisting of several strands of wire) on productivity of the phaseolus landrace 'Badda bianca'. Marketable yields obtained from 15 june sowing were significantly higher than those from June 30 and July 15 sowing dates which in turn were signif…