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Electron impact spectra of silane and germane have been recorded using electrons of 200 eV incidence at scattering angles of ∼2°–9°. The range of energy losses covers the entire region of single electron excitation from the valence shell. In the bound state spectrum evidence is presented supporting the existence of two valence transitions in addition to anticipated s, p, and d Rydberg transitions. The 9° spectra reveal much structural detail in the ∼4 eV energy range preceding the 2A1 ion state. The most prominent band consists of a superposition of an optically allowed valence excitation and a symmetry forbidden Rydberg transition. The remaining peaks may be members of vibrational progressions belonging to either [d(t2), a1], [p, a1] ← (a1)2 dipole allowed or [d(e), a1], [s,a1] ← (a1)2 dipole forbidden channels. Of these two possibilities the evidence presented here favors the latter choice. [ABSTRACT FROM AUTHOR]

We have examined the electronic structure of HgCl2 and HgBr2 from 5 to 14 eV by high resolution electron energy loss spectroscopy. Our measurements include the near-UV region which has not been examined by any previous technique and which is found to be rich in Rydberg states. In particular, in each molecule we identify members of two optically allowed Rydberg series and one forbidden series with electronic structues σ2gσ2uπ4uπ3g [npπu, npσu, and ndπg, or (n+1)sσg] which converge to the 2∏g ground ionic state. In addition, other structures which form the dominant energy loss mechanisms in our spectra are identified as arising from optically allowed Rydberg states associated with the excited ionic states 2Πu, 2Σu, and 2Σg. Measurements at energy loss below 9 eV confirm previous valence states observed in photoabsorbtion and suggest the existence of two new valence states in each molecule. Angular measurements facilitate identification of many of the newly observed structures in our electron-energy loss spectra. [ABSTRACT FROM AUTHOR]

In this article, the finite element method (FEM) using cohesive element is applied to predict the delamination behavior in laminated composite with double delaminations embedded in different depth positions under compressive load. In particular, compared with single delamination composites, the interaction between delaminations and the complicated propagation behavior are discussed. Furthermore, the study is focused on the significant effects of double delaminations on delamination buckling and growth behavior, such as the distance between double delaminations and the delaminations' depth position. [ABSTRACT FROM AUTHOR]

Proton energy loss spectroscopy (PELS) has been used to investigate the very high overtone states of the ν3 mode in CF4. With a new scattering apparatus, which is described here in detail, it has been possible to directly measure the energy levels of the dominantly excited ν3 mode up to its 14th overtone with an energy resolution of δE=10–15 meV, corresponding to 80–120 cm-1. The data are interpreted using the Hecht vibrational Hamiltonian which predicts the tensor splitting of the ν3 mode energy levels into sublevel bands. By adjusting the values of the anharmonicity parameters X33, G33, and T33, previously determined by IR spectroscopy and introducing a second-order anharmonicity parameter X333, it was possible to fit the ν3 mode energy levels to the measured energy loss distributions. A model based on the earlier theoretical work of Levene and Perry [H. B. Levene and D. Perry, J. Chem. Phys. 84, 4385 (1986)] for the proton–CF4 scattering process is extended to allow the simulation of complete spectra including contributions from combinations with the ν1 and ν4 mode for comparison with the experimental energy loss spectra. The influence of all relevant parameters on the simulated data is analyzed in detail. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Dynamic responses of a composite marine propeller in spatially wake were investigated in this paper. A hydroelastic model was developed to identify the response characteristics of the composite propeller blades using a finite element method (FEM) coupled with a computational fluid dynamics (CFD) method. Rotational effects and added mass were considered. A coupled matrix was established and solved by the Newton-Raphson numerical procedure. The dynamic characteristics and responses of the composite blade were calculated and compared with those of the counterpart rigid blade. Effects of various parameters, including the layer lamination and fiber orientation were investigated. [ABSTRACT FROM AUTHOR]

The purpose of the paper is to analyze the damping characteristics of several advanced fibre-reinforced composites, and ulteriorly optimize the damping performance of a composite structure. Numerical modelling of the damping was developed considering the finite element method based on the modal strain energy. The modal damping characteristics of the fibre-reinforced composites were evaluated, including the modal frequencies, modal shapes and modal loss factors. The damping performances of different fibre-reinforced composites were compared. Furthermore, the damping performance of a laminated composite structure was optimized by considering the effects of different lay-up sequences and layer orientations. An optimum design scheme of the composite structure was presented. [ABSTRACT FROM AUTHOR]

Energy loss distributions of He+ ions after collisions with HF molecules in a secondary beam at laboratory collision energies in the range 25–50 eV show a regular structure indicating rotational excitation up to ΔJ=35 with no clear evidence for vibrational excitation. The observed propensity for large ΔJ transitions decreases with increasing collision energy but increases with increase in scattering angle. Three dimensional quasiclassical trajectory calculations using a potential energy surface based on the He+–Ne interaction at short range and a damped long range ion–dipole (quadrupole) interaction reproduce all the essential features of the experimental results. [ABSTRACT FROM AUTHOR]

Development of low radioactive technique allows to investigate many other rare nuclear and subnuclear processes: double decay, rare and decays, and to search for hypothetical particles and processes like axions, charge nonconserving decays, the nucleon, di-nucleon and tri-nucleon decays into invisible channels, to test the Pauli principle. Here, we present results of the rare processes searches and development of instrumentation for low counting experiments. [ABSTRACT FROM AUTHOR]

Experimental observations and theoretical arguments at Galaxy and larger scales have suggested that a large fraction of the Universe is composed by Dark Matter (DM) particles. This has motivated the DAMA experimental efforts to investigate the presence of such particles in the galactic halo by exploiting a model independent signature with highly radiopure setups deep underground. In this paper, a review of the results obtained with the total exposure of 1.04 ton × yr collected by DAMA/LIBRA-phase1 deep underground at the Gran Sasso National Laboratory (LNGS) of the INFN during seven annual cycles is given. The DAMA/LIBRA-phase1 data give evidence for the presence of DM particles in the galactic halo, on the basis of the exploited model independent DM annual modulation signature by using highly radiopure NaI(Tl) target, at 7.5 C.L. Including also the data of the first generation DAMA/NaI experiment (cumulative exposure 1.33 ton × yr, corresponding to 14 annual cycles), the C.L. is 9.3 and the modulation amplitude of the single-hit scintillation events in the (2-6) keV energy interval is: (0.0112 ± 0.0012) cpd/kg/keV; the measured phase is (144 ± 7) days and the measured period is (0.998 ± 0.002) yr, values well in agreement with those expected for DM particles. No systematic or side reaction able to mimic the exploited DM signature has been found or suggested by anyone over more than a decade. [ABSTRACT FROM AUTHOR]

The DAMA/LIBRA-phase1 and the former DAMA/NaI data (cumulative exposure 1.33 ton yr, corresponding to 14 annual cycles) give evidence at 9.3 C.L. for the presence of Dark Matter (DM) particles in the galactic halo, on the basis of the exploited model independent DM annual modulation signature by using highly radio-pure NaI(Tl) target. Results and comparisons will be shortly recalled. Recent analyses on possible diurnal effects and on the Earth shadowing effect (the latter holds only for some DM candidates) will be mentioned. The analysis of the time distribution of the low-energy single-hit events in DAMA/LIBRA-phase1 is reported for the first time. Finally, some perspectives of the presently running DAMA/LIBRA-phase2 will be mentioned. [ABSTRACT FROM AUTHOR]

The DAMA project is an observatory for rare processes operating deep underground at the Gran Sasso National Laboratory of the I.N.F.N.. In particular, the main apparatus DAMA/LIBRA is mainly dedicated to the investigation of the presence of Dark Matter (DM) particles in the galactic halo by exploiting the model independent DM annual modulation signature. The present DAMA/LIBRA and the former DAMA/Nal (exposed masses: ≃250 kg and ≃ 100 kg of highly radiopure Nal(Tl), respectively) experiments have released so far a total exposure of 1.17tonxyr, collected over 13 annual cycles. They have obtained a positive model independent result for the presence of DM particles in the galactic halo at 8.9σ C.L.. Some of the obtained results are shortly summarized and future perspectives mentioned. [ABSTRACT FROM AUTHOR]

Experimental observations and theoretical arguments at Galaxy and larger scales have suggested that a large fraction of the Universe is composed by Dark Matter particles. This has motivated the DAMA experimental efforts to investigate the presence of such particles in the galactic halo by exploiting a model independent signature and very highly radiopure setup in deep underground. Few introductory arguments are summarized before presenting a review of the present model independent positive results obtained by the DAMA/NaI and DAMA/LIBRA setups at the Gran Sasso National Laboratory of the INFN. Implications and model dependent comparisons with other different kinds of results will be shortly addressed. Some arguments put forward in literature will be confuted. [ABSTRACT FROM AUTHOR]

The DAMA/LIBRA experiment has a sensitive mass of about 250 kg highly radiopure NaI(Tl). It is running at the Gran Sasso National Laboratory of the INFN in Italy and is mainly devoted to the investigation of dark matter (DM) particles in the galactic halo by exploiting the model-independent DM annual modulation signature. The present DAMA/LIBRA and the former DAMA/NaI experiments (the first generation experiment having an exposed mass of about 100 kg) have thus far cumulatively released the results of data collected over 13 annual cycles (total exposure: 1.17 t year). They give model-independent evidence of the presence of DM particles in the galactic halo on the basis of the investigated DM signature at 8.9 σ C.L. for the cumulative exposure. The main aspects of the obtained results are summarized and some comments are addressed. L'expérience DAMA/LIBRA utilise un détecteur de 250 kg de NaI(Tl) de haute pureté radioactive. Les mesures sont prises au Laboratoire National du Gran Sasso de l'I.N.F.N. en Italie et l'expérience se concentre sur la recherche de particules de matière noire (DM) dans le halo galactique en exploitant la signature indépendante des modèles de la modulation annuelle de ces particules (DM). L'actuelle expérience DAMA/LIBRA et sa prédécesseur DAMA/NaI un (la première génération avec un détecteur de 100 kg) ont produit les résultats cumulatifs de données colligées sur 13 cycles annuels (capture totale: 1.17 tonne années). Ces résultats suggèrent, de façon indépendante des modèles, la présence de particules de matière noire dans le halo galactique sur la base de leur signature, avec un intervalle de confiance de 8.9 σ pour le cumulatif des données. Nous résumons les aspects principaux des données et y ajoutons quelques commentaires. [ABSTRACT FROM AUTHOR]

Some extensions of the Standard Model provide Dark Matter candidate particles with sub-GeV mass. These Light Dark Matter particles have been considered for example in Warm Dark Matter scenarios (e.g. the keV scale sterile neutrino, axino or gravitino). Moreover, MeV scale DM candidates have been proposed in supersymmetric models and as source of the 511 keV line from the Galactic center. In this paper the possibility of direct detection of a Light Dark Matter candidate is investigated considering the inelastic scattering processes on the electron or on the nucleus targets. Some theoretical arguments are developed and related phenomenological aspects are discussed. Allowed volumes and regions for the characteristic phenomenological parameters of the considered scenarios are derived from the DAMA/NaI annual modulation data. [ABSTRACT FROM AUTHOR]