Limits on a Strong Electroweak Sector from e^+ e^- -> 2gamma + missing E at LEP2

We study the process $e^+ e^- \to \gamma \gamma \nu \bar{\nu}$ in the context of a strong electroweak symmetry breaking model, which can be a source of events with two photons and missing energy at LEP2. We investigate bounds on the model assuming that no deviation is observed from the Standard Model within a given experimental error.Comment: 7 pages, Latex, one figur

Impact of Power Allocation and Antenna Directivity in the Capacity of a Multiuser Cognitive Ad Hoc Network

This paper studies the benefits that power control and antenna directivity can bring to the capacity of a multiuser cognitive radio network. The main objective is to optimize the secondary network sum rate under the capacity constraint of the primary network. Exploiting location awareness, antenna directivity, and the power control capability, the cognitive radio ad hoc network can broaden its coverage and improve capacity. Computer simulations show that by employing the proposed method the system performance is significantly enhanced compared to conventional fixed power allocation

Saturated Critical Heat Flux in a Multi-Microchannel Heat Sink Fed by a Split Flow System

An extensive experimental campaign has been carried out for the measurement of saturated critical heat flux in a multi-microchannel copper heat sink. The heat sink was formed by 29 parallel channels that were 199 μm wide and 756 μm deep. In order to increase the critical heat flux and reduce the two-phase pressure drop, a split flow system was implemented with one central inlet at the middle of the channels and two outlets at either end. The base critical heat flux was measured using three HFC Refrigerants (R134a, R236fa and R245fa) for mass fluxes ranging from 250 to 1500 kg/m2 s, inlet subcoolings from −25 to −5 K and saturation temperatures from 20 to 50 °C. The parametric effects of mass velocity, saturation temperature and inlet subcooling were investigated. The analysis showed that significantly higher CHF was obtainable with the split flow system (one inlet–two outlets) compared to the single inlet–single outlet system, providing also a much lower pressure drop. Notably several existing predictive methods matched the experimental data quite well and quantitatively predicted the benefit of higher CHF of the split flow

Visco-hyperelastic model with damage for simulating cyclic thermoplastic elastomers behavior applied to an industrial component

In this work a nonlinear phenomenological visco-hyperelastic model including damage consideration is developed to simulate the behavior of Santoprene 101-73 material. This type of elastomeric material is widely used in the automotive and aeronautic sectors, as it has multiple advantages. However, there are still challenges in properly analyzing the mechanical phenomena that these materials exhibit. To simulate this kind of material a lot of theories have been exposed, but none of them have been endorsed unanimously. In this paper, a new model is presented based on the literature, and on experimental data. The test samples were extracted from an air intake duct component of an automotive engine. Inelastic phenomena such as hyperelasticity, viscoelasticity and damage are considered singularly in this model, thus modifying and improving some relevant models found in the literature. Optimization algorithms were used to find out the model parameter values that lead to the best fit of the experimental curves from the tests. An adequate fitting was obtained for the experimental results of a cyclic uniaxial loading of Santoprene 101-73

Low-complexity motion estimation for the Scalable Video Coding extension of H.264/AVC

The recently standardized Scalable Video Coding(SVC) extension of H.264/AVC allows bitstream scalability with improved rate-distortion efficiency with respect to the classical Simulcasting approach, at the cost of an increased computational complexity of the encoding process. So one critical issue related to practical deployment of SVC is the complexity reduction, fundamental to use it in consumer applications. In this paper, we present a fully scalable fast motion estimation algorithm that enables an excellent complexity performance

New Fast Search Algorithm for Base Layer of H.264 Scalable Video Coding Extension

In this contribution, a fast search motion estimation algorithm for H.264/AVC SVC (scalable video coding) [2] base layer with hierarchical B-frame structure for temporal decomposition is presented and compared with fast search motion estimation algorithm in JSVM software [1], that is the reference software for H.264/AVC SVC. The proposed technique is a block-matching based motion estimation algorithm working in two steps, called Coarse search and Fine search. The Coarse search is performed for each frame in display order, and for each 16x16 macroblock chooses the best motion vector at half pel accuracy. Fine search is performed for each frame in encoding order and finds the best prediction for each block type, reference frame and direction, choosing the best motion vector at quarter pel accuracy using R-D optimization. Both Coarse and Fine Search test 3 spatial and 3 temporal predictors, and add to the best one a set of updates. The spatial predictors for the fine search are the result of the Fine search already performed for the previous blocks, while the temporal predictors are the results of Coarse Search scaled by an appropriate coefficient. This scaling is performed since in the Coarse search each picture is always estimated with respect to the previous one, while in the Fine Search the temporal distance between the current picture and its references depend on the temporaldecomposition level. Moreover in Fine search the number and the value of the updates tested depend on the distance between the current picture and its references. These sets of updates are the result of a huge number of simulations on test sequences with different motion features. The proposed algorithm has been tested on the set of test sequences proposed by JVT group, using different resolutions and temporal decomposition structures. The proposed method can reduce the average coding complexity in terms of motion vector tested from 70 to 90 percent with respect to the Fast-ME JVT method, while the quality loss depends on the GOP dimension, that is the most critical parameter for the performance of the algorithm. In fact for small GOP dimensions (4 or 8) the algorithm has the same quality at equal bit-rate respect to the Fast-ME JVT method for almost all the sequences and better quality for some sequences. For medium and long GOP dimensions (16-32) the algorithm has a quality loss lower than 0.5 dB for all the tested sequences

Herschel PACS Spectroscopic Diagnostics of Local ULIRGs: Conditions and Kinematics in Mrk 231

In this first paper on the results of our Herschel PACS survey of local Ultraluminous Infrared Galaxies (ULIRGs), as part of our SHINING survey of local galaxies, we present far-infrared spectroscopy of Mrk 231, the most luminous of the local ULIRGs, and a type 1 broad absorption line AGN. For the first time in a ULIRG, all observed far-infrared fine-structure lines in the PACS range were detected and all were found to be deficient relative to the far infrared luminosity by 1 - 2 orders of magnitude compared with lower luminosity galaxies. The deficits are similar to those for the mid-infrared lines, with the most deficient lines showing high ionization potentials. Aged starbursts may account for part of the deficits, but partial covering of the highest excitation AGN powered regions may explain the remaining line deficits. A massive molecular outflow, discovered in OH and 18OH, showing outflow velocities out to at least 1400 km/sec, is a unique signature of the clearing out of the molecular disk that formed by dissipative collapse during the merger. The outflow is characterized by extremely high ratios of 18O / 16O suggestive of interstellar medium processing by advanced starbursts.Comment: Accepted for publication in the Astronomy and Astrophysics Herschel Special Issue, 5 pages, 4 figure

Educational Outcomes of Postsecondary Occupational Students

This Brief discusses a research study that was conducted to determine the rates of degree completion of community college occupational students compared with other types of postsecondary students, and to identify factors that might explain those differences. Much of the existing literature on college persistence and completion is focused on baccalaureate students and pays little attention to students in community colleges, and even fewer studies consider differences by students’ program of study. Therefore, it is important to investigate whether students in occupational programs in community colleges persist in postsecondary education and attain degrees at similar rates as their academic and baccalaureate peers

Classical sum rules and spin correlations in photoabsorption and photoproduction processes

In this paper we study the possibility of generalizing the classical photoabsorption ($\gamma a \to b c$) sum rules, to processes $b c \to \gamma a$ and crossed helicity amplitudes. In the first case, using detailed balance, the sum rule is written as $\int_{\nu_{th}}^\infty {\frac{{d\nu}}{\nu}} K\Delta \sigma_{Born} (\nu)=0$ where $K$ is a kinematical constant which depends only on the mass of the particles and the center of mass energy. For other crossed helicity amplitudes, we show that there is a range of values of $s$ and $t$ for which the differential cross section for the process $\gamma b \to a c$ or $a c \to \gamma b$ in which the helicities of the photon and particle $a$ have specific values, is equal to the differential cross section for the process in which one of these two helicities is reversed (parallel-antiparallel spin correlation).Comment: 9 pages, 2 figure