Nonlinear normal modes of a two degree of freedom oscillator with a bilateral elastic stop

A study of the non linear modes of a two degree of freedom mechanical system with bilateral elastic stop is considered. The issue related to the non-smoothness of the impact force is handled through a regularization technique. In order to obtain the Nonlinear Normal Mode (NNM), the harmonic balance method with a large number of harmonics, combined with the asymptotic numerical method, is used to solve the regularized problem. These methods are present in the software "package" MANLAB. The results are validated from periodic orbits obtained analytically in the time domain by direct integration of the non regular problem. The two NNMs starting respectively from the two linear normal modes of the associated underlying linear system are discussed. The energy-frequency plot is used to present a global vision of the behavior of the modes. The dynamics of the modes are also analyzed comparing each periodic orbits and modal lines. The first NNM shows an elaborate dynamics with the occurrence of multiple impacts per period. On the other hand, the second NNM presents a more simple dynamics with a localization of the displacement on the first mass

PERSISTENT HIGH WATER LEVELS AROUND ANDAMAN & NICOBAR ISLANDS FOLLOWING THE 26 DECEMBER 2004 TSUNAMI

During the tsunami of 26th December 2004 in the Indian Ocean, media reports suggested that high water levels persisted around the Andaman & Nicobar Islands for several days. These persistent high water levels can be explained by invoking the existence of trapped and partially leaky modes on the shelves surrounding these islands. It has been known in the studies of tides in the global oceans, that there are two distinct types of oscillations, separated in their frequencies by the period of the pendulum day. One species are the gravity waves, and the others are the rotational waves, associated with earth's rotation. Both these species can be found in tidal records around islands as well as near coastlines. Essentially these are either trapped or partly leaky modes, partly trapped on the continental shelves. These two types of modes are usually found in the tsunami records on tide gauges. The tide gauge records as well as visual descriptions of the water levels during and after the occurrence of a tsunami clearly show the presence of these oscillations

Novel types of anti-ecloud surfaces

In high power RF devices for space, secondary electron emission appears as the main parameter governing the multipactor effect and as well as the e-cloud in large accelerators. Critical experimental activities included development of coatings with low secondary electron emission yield (SEY) for steel (large accelerators) and aluminium (space applications). Coatings with surface roughness of high aspect ratio producing the so-call secondary emission suppression effect appear as the selected strategy. In this work a detailed study of the SEY of these technological coatings and also the experimental deposition methods (PVD and electrochemical) are presented. The coating-design approach selected for new low SEY coatings include rough metals (Ag, Au, Al), rough alloys (NEG), particulated and magnetized surfaces, and also graphene like coatings. It was found that surface roughness also mitigate the SEY deterioration due to aging processes.Comment: 4 pages, contribution to the Joint INFN-CERN-EuCARD-AccNet Workshop on Electron-Cloud Effects: ECLOUD'12; 5-9 Jun 2012, La Biodola, Isola d'Elba, Italy; CERN Yellow Report CERN-2013-002, pp.153-15

The Stripe Fortified GCT:A new GCT design for maximizing the controllable current

In this paper we introduce a new GCT design, namely the Stripe Fortified GCT, for the purpose of maximizing the controllable current by optimizing the current flow path in the device during turn-off. The main design of the new device along with variants are introduced. The MCC performance of this novel structure is assessed with a developed two dimensional model for full wafer simulations. Our results show that this new design is a very good candidate for increasing the MCC to values more than 5000A

Self-trapped electrons and holes in PbBr2_2 crystals

We have directly observed self-trapped electrons and holes in PbBr$_{2}$ crystals with electron-spin-resonance (ESR) technique. The self-trapped states are induced below 8 K by two-photon interband excitation with pulsed 120-fs-width laser light at 3.10 eV. Spin-Hamiltonian analyses of the ESR signals have revealed that the self-trapping electron centers are the dimer molecules of Pb$_2$$^{3+}$ along the crystallographic a axis and the self-trapping hole centers are those of Br$_2$$^-$ with two possible configurations in the unit cell of the crystal. Thermal stability of the self-trapped electrons and holes suggests that both of them are related to the blue-green luminescence band at 2.55 eV coming from recombination of spatially separated electron-hole pairs.Comment: 8 pages (7 figures, 2 tables), ReVTEX; revised the text and figures 1, 4, and

Novel Approach Toward Plasma Enhancement in Trench-Insulated Gate Bipolar Transistors

In this letter, a trench-insulated gate bipolar transistor (IGBT) design with local charge compensating layers featured at the cathode of the device is presented and analyzed. The superjunction or reduced surface effect proves to be very effective in overcoming the inherited ON-state versus breakdown tradeoff appearing in conventional devices, such as the soft punch through plus or field stop plus (FS+) IGBTs. This design enhances the ON-state performance of the FS+IGBT by increasing the plasma concentration at the cathode side without affecting either the switching performance or the breakdown rating

New Bi-Mode Gate-Commutated Thyristor Design Concept for High-Current Controllability and Low ON-State Voltage Drop

© 2016 IEEE. A new design approach for bi-mode gatecommutated thyristors (BGCTs) is proposed for high-current controllability and low ON-state voltage drop. Using a complex multi-cell mixed-mode simulation model which can capture the maximum controllable current (MCC) of large area devices, a failure analysis was performed to demonstrate that the new design concept can increase the MCC by about 27% at room temperature and by about 17% at 400 K while minimizing the ON-state voltage drop. The simulations depict that the improvement comes from the new approach to terminate the GCT part in the BGCT way of intertwining GCT and diode regions for reverse conducting operation

Structure and magnetism of Tm atoms and monolayers on W(110)

Under the terms of the Creative Commons Attribution License 3.0 (CC-BY).We investigated the growth and magnetic properties of Tm atoms and monolayers deposited on a W(110) surface using scanning tunneling microscopy and x-ray magnetic circular and linear dichroism. The equilibrium structure of Tm monolayer films is found to be a strongly distorted hexagonal lattice with a Moiré pattern due to the overlap with the rectangular W(110) substrate. Monolayer as well as isolated Tm adatoms on W present a trivalent ground-state electronic configuration, contrary to divalent gas phase Tm and weakly coordinated atoms in quench-condensed Tm films. Ligand field multiplet simulations of the x-ray absorption spectra further show that Tm has a |J=6,Jz=±5¿ electronic ground state separated by a few meV from the next lowest substates |J=6,Jz=±4¿ and |J=6,Jz=±6¿. Accordingly, both the Tm atoms and monolayer films exhibit large spin and orbital moments with out-of-plane uniaxial magnetic anisotropy. X-ray magnetic dichroism measurements as a function of temperature show that the Tm monolayers develop antiferromagnetic correlations at about 50 K. The triangular structure of the Tm lattice suggests the presence of significant magnetic frustration in this system, which may lead to either a noncollinear staggered spin structure or intrinsic disorder.This work was supported by the European Research Council (StG 203239 NOMAD), Agència de Gestió d’Ajuts Universitaris i de Recerca (2009 SGR 695), Spanish MINECO (Grants No. MAT2009-10040, No. MAT2010-15659, and No. MAT2012-31309), Gobierno de Aragón (Grant No. E81), Fondo Social Europeo, and the Swiss Competence Centre for Materials Science and Technology (CCMX).Peer Reviewe

The Ilizarov external fixator - a useful alternative for the treatment of proximal tibial fractures A prospective observational study of 30 consecutive patients

BACKGROUND: In dislocated proximal tibial fractures, the most frequently used treatment is ORIF with screws and plates. Minimally-invasive techniques using external fixation are an alternative. The aim of this study was to analyse the clinical and radiological results using the Ilizarov technique in both uni- and bicondylar tibial fractures. METHODS: Thirty consecutive patients with isolated fractures of the proximal tibia were treated with the Ilizarov technique, 11 Schatzker I-IV with 2–3 rings and 19 Schatzker V-VI with 3–4 tibial rings and a femoral, hinged, two-ring extension. Unrestricted weight-bearing was allowed. Pre and post-operatively, conventional radiographs, computerized tomography scans, post-operative pain assessments and complications were evaluated. The knee function was evaluated with the EQ-5D, NHP and KOOS scores, as well as self-appraisal. RESULTS: All the fractures healed. Twenty-five patients achieved a range of motion better than 10-100º. The type I-IV fractures had a shorter operating time and hospital stay, as well as better knee flexion, and the self-appraisal indicated that they tolerated the treatment better. Pin infections occurred in 4% of the pin sites, but only two patients required debridement. Two patients developed compartment syndrome and underwent fasciotomy. No patient complained of functional knee instability. Two patients underwent a total knee arthroplasty because of residual pain. The overall result was judged as satisfactory in twenty-seven patients. CONCLUSIONS: The Ilizarov method produces a good clinical outcome and is a valuable treatment alternative in proximal tibial fractures of all types