Sub-kHz lasing of a CaF_2 Whispering Gallery Mode Resonator Stabilized Fiber Ring Laser

We utilize a high quality calcium fluoride whispering-gallery-mode resonator to stabilize a simple erbium doped fiber ring laser with an emission frequency of 196 THz (wavelenght 1530 nm) to a linewidth below 650 Hz. This corresponds to a relative stability of 3.3 x 10^(-12) over 16 \mus. In order to characterize the linewidth we use two identical self-built lasers and a commercial laser to determine the individual lasing linewidth via the three-cornered hat method.Comment: 4 pages, 3 figure

Grammatical workspace sharing during language production and language comprehension: Evidence from grammatical multitasking

Grammatical encoding and grammatical decoding (in sentence production and comprehension, respectively) are often portrayed as independent modalities of grammatical performance that only share declarative resources: lexicon and grammar. The processing resources subserving these modalities are supposed to be distinct. In particular, one assumes the existence of two workspaces where grammatical structures are assembled and temporarily maintained—one for each modality. An alternative theory holds that the two modalities share many of their processing resources and postulates a single mechanism for the online assemblage and short-term storage of grammatical structures: a shared workspace. We report two experiments with a novel “grammatical multitasking” paradigm: the participants had to read (i.e., decode) and to paraphrase (encode) sentences presented in fragments, responding to each input fragment as fast as possible with a fragment of the paraphrase. The main finding was that grammatical constraints with respect to upcoming input that emanate from decoded sentence fragments are immediately replaced by grammatical expectations emanating from the structure of the corresponding paraphrase fragments. This evidences that the two modalities have direct access to, and operate upon, the same (i.e., token-identical) grammatical structures. This is possible only if the grammatical encoding and decoding processes command the same, shared grammatical workspace. Theoretical implications for important forms of grammatical multitasking—self-monitoring, turn-taking in dialogue, speech shadowing, and simultaneous translation—are explored

The mechanical properties and toughening mechanisms of an epoxy polymer modified with polysiloxane-based core-shell particles

AbstractAn epoxy resin, cured using an anhydride hardener, has been modified by the addition of pre-formed polysiloxane core-shell rubber (S-CSR) particles with a mean diameter of 0.18 μm. The glass transition temperature, Tg, of the cured unmodified epoxy polymer was 148 °C, and this was unchanged after the addition of the S-CSR particles. The polysiloxane rubber particles had a Tg of about −100 °C. Atomic force microscopy showed that the S-CSR particles were well-dispersed in the epoxy polymer. The addition of the S-CSR particles reduced the Young's modulus and tensile strength of the epoxy polymer, but at 20 °C the fracture energy, GIc, increased from 117 J/m2 for the unmodified epoxy to 947 J/m2 when 20 wt% of the S-CSR particles were incorporated. Fracture tests were also performed at −55 °C, −80 °C, and −109 °C. The results showed that the measured fracture energy of the S-CSR-modified epoxy polymers decreased significantly below room temperature. For example, at −109 °C, a fracture energy of 481 J/m2 was measured using 20 wt% of S-CSR particles. Nevertheless, this value of toughness still represented a major increase compared with the unmodified epoxy polymer, which possessed a value of GIc of 174 J/m2 at this very low test temperature. Thus, a clear fact that emerged was that the addition to the epoxy polymer of the S-CSR particles may indeed lead to significant toughening of the epoxy, even at temperatures as low as about −100 °C. The toughening mechanisms induced by the S-CSR particles were identified as (a) localised plastic shear-band yielding around the particles and (b) cavitation of the particles followed by plastic void growth of the epoxy polymer. These mechanisms were modelled using the Hsieh et al. approach [33,49] and the values of GIc of the S-CSR-modified epoxy polymers at the different test temperatures were calculated. Excellent agreement was found between the predictions and the experimentally measured fracture energies. Further, the experimental and modelling results of the present study indicated that the extent of plastic void growth was suppressed at low temperatures for the S-CSR-modified epoxy polymers, but that the localised shear-band yielding mechanism was relatively insensitive to the test temperature

The tensile fatigue behaviour of a silica nanoparticle-modified glass fibre reinforced epoxy composite

Abstract An anhydride-cured thermosetting epoxy polymer was modified by incorporating 10 wt.% of welldispersed 20 nm diameter silica nanoparticles. The stress-controlled tensile fatigue behaviour at a stress ratio of R = 0.1 was investigated for bulk specimens of the neat and the silica-modified epoxy. The addition of the silica nanoparticles increased the fatigue life by about three to four times. The neat and the nanoparticle-modified epoxy resins were used to fabricate glass fibre reinforced plastic (GFRP) composite laminates by resin infusion under flexible tooling (RIFT). Tensile fatigue tests were performed on these composites, during which the matrix cracking and stiffness degradation was monitored. The fatigue life of the GFRP composite was increased by about three to four times due to the silica nanoparticles. Suppressed matrix cracking and a reduced crack propagation rate in the nanoparticle-modified matrix were observed to contribute towards the enhanced fatigue life of the composite containing the silica nanoparticles

The tensile fatigue behavior of a glass-fiber reinforced plastic composite using a hybrid-toughened epoxy matrix

ABSTRACT A thermosetting epoxy-polymer was modified by incorporating 9 wt.% of carboxyl-terminated butadiene-acrylonitrile (CTBN) rubber microparticles and 10 wt.% of silica nanoparticles. The tensile fatigue behaviour at a stress ratio, R = 0.1 for both the neat (i.e. unmodified) epoxy-polymer and the hybridepoxy polymer was first investigated. The fatigue life of the hybrid-epoxy * Corresponding author: Tel. +91-80-2508 6310 ; Fax: +91-80-2508 6301 E-mail address: [email protected] (CM Manjunatha) 2 polymer was about six to ten times higher than that the neat-epoxy polymer. Secondly, the neat and the hybrid-epoxy resins were infused into a quasiisotropic lay-up, E-glass fiber fabric via a 'Resin Infusion under Flexible Tooling' (RIFT) set-up to fabricate glass-fiber reinforced-plastic (GFRP) composite panels. The tensile fatigue tests at a stress ratio, R = 0.1 were performed on both of these GFRP composites during which the matrix cracking and stiffness degradation were routinely monitored. The fatigue life of the GFRP composite increased by about six to ten times due to employing the hybrid-epoxy matrix, compared to the neat-epoxy matrix. Suppressed matrix cracking and a reduced crack propagation rate were observed in the hybrid-epoxy matrix, which resulted from the various toughening micromechanisms induced by the presence of both the rubber microparticles and silica nanoparticles. These factors were considered to contribute towards the enhanced fatigue life which was observed for the GFRP composite employing the hybrid-epoxy matrix

Neutrino spin oscillations in gravitational fields

We study neutrino spin oscillations in black hole backgrounds. In the case of a charged black hole, the maximum frequency of oscillations is a monotonically increasing function of the charge. For a rotating black hole, the maximum frequency decreases with increasing the angular momentum. In both cases, the frequency of spin oscillations decreases as the distance from the black hole grows. As a phenomenological application of our results, we study simple bipolar neutrino system which is an interesting example of collective neutrino oscillations. We show that the precession frequency of the flavor pendulum as a function of the neutrino number density will be higher for a charged/non-rotating black hole compared with a neutral/rotating black hole respectively.Comment: Replaced with the version accepted for publication in Gravitation and Cosmology, Springer. 10 pages. 4 figure

Validation of Kalman Filter alignment algorithm with cosmic-ray data using a CMS silicon strip tracker endcap

A Kalman Filter alignment algorithm has been applied to cosmic-ray data. We discuss the alignment algorithm and an experiment-independent implementation including outlier rejection and treatment of weakly determined parameters. Using this implementation, the algorithm has been applied to data recorded with one CMS silicon tracker endcap. Results are compared to both photogrammetry measurements and data obtained from a dedicated hardware alignment system, and good agreement is observed.Comment: 11 pages, 8 figures. CMS NOTE-2010/00

Mechanical and fracture performance of carbon fibre reinforced composites with nanoparticle modified matrices

The microstructure and fracture performance of carbon-fibre reinforced polymer (CFRP) composites with an epoxy resin cured with an anhydride hardener containing silica nanoparticles and/or polysiloxane core-shell rubber (CSR) particles was investigated in the current work. Double cantilever beam tests were performed in order to evaluate the fracture energy of the CFRP composites, while the single edge notched bend (SENB) specimen was employed to evaluate the fracture energy of the bulk polymers. Tests were conducted at room temperature and at -80°C. The transferability of the toughness from the bulk polymers to the fibre-composite systems is discussed, with an emphasis on elucidating the toughening mechanism