1,571 research outputs found
Multi-Higgs boson production in the Standard Model and beyond
We present a calculation of the loop-induced processes gg -> HH and gg ->
HHH, and investigate the observability of multi-Higgs boson production at the
CERN Large Hadron Collider (LHC) in the Standard Model (SM) and beyond. While
the SM cross sections are too small to allow observation at the LHC, we
demonstrate that physics beyond the SM can lead to amplified, observable cross
sections. Furthermore, the applicability of the heavy top quark approximation
in two- and three-Higgs boson production is investigated. We conclude that
multi-Higgs boson production at the SuperLHC is an interesting probe of Higgs
sectors beyond the SM and warrants further study.Comment: 17 pages, 17 figure
Introducing TAXI: a Transportable Array for eXtremely large area Instrumentation studies
A common challenge in many experiments in high-energy astroparticle physics
is the need for sparse instrumentation in areas of 100 km2 and above, often in
remote and harsh environments. All these arrays have similar requirements for
read-out and communication, power generation and distribution, and
synchronization. Within the TAXI project we are developing a transportable,
modular four-station test-array that allows us to study different approaches to
solve the aforementioned problems in the laboratory and in the field.
Well-defined interfaces will provide easy interchange of the components to be
tested and easy transport and setup will allow in-situ testing at different
sites. Every station consists of three well-understood 1 m2 scintillation
detectors with nanosecond time resolution, which provide an air shower trigger.
An additional sensor, currently a radio antenna for air shower detection in the
100 MHz band, is connected for testing and calibration purposes. We introduce
the TAXI project and report the status and performance of the first TAXI
station deployed at the Zeuthen site of DESY.Comment: 4 pages, 3 figures, presented at ARENA 2014, Annapolis, MD, June 201
ADJUSTMENT OF FUNCTIONAL ELECTRICAL STIMULATION (FES) ACCORDING TO KNEE FLEXION ANGLE
To clarify the different results of our simulation and FES-cycling tests, measurements on a knee dynamometer were made. The m. quadriceps of 16 healthy test persons was activated both by FES and voluntary contraction. Stimulated with the same level of intensity in a knee flexion angle range from 5° to 105°, the diagrams showed a very unusual course. The knee torque shows its maximum at the knee flexion angle of approx. 30°. Additional isometric measurements using stimulation intensity on constant on-verge-to pain levels for different knee angles were made. The measured courses of the resulting knee torque as a function of the knee angle are much closer to the results of physiologically activated muscle. These measurements show that for optimum power release, the stimulation intensity must be regulated depending on the knee flexion angle
Light-mediated strong coupling between a mechanical oscillator and atomic spins one meter apart
Engineering strong interactions between quantum systems is essential for many
phenomena of quantum physics and technology. Typically, strong coupling relies
on short-range forces or on placing the systems in high-quality electromagnetic
resonators, restricting the range of the coupling to small distances. We use a
free-space laser beam to strongly couple a collective atomic spin and a
micromechanical membrane over a distance of one meter in a room-temperature
environment. The coupling is highly tunable and allows the observation of
normal-mode splitting, coherent energy exchange oscillations, two-mode thermal
noise squeezing and dissipative coupling. Our approach to engineer coherent
long-distance interactions with light makes it possible to couple very
different systems in a modular way, opening up a range of opportunities for
quantum control and coherent feedback networks.Comment: 24 pages, 9 figure
Sport Consumer Behavior Research: Improving Our Game
Sport consumer behavior (SCB) research continues to grow in both popularity and sophistication. A guiding principle in much of this research is that sport consumers seek out sport related experiences, and the benefits they yield, in order to satisfy needs and wants. This approach has provided new knowledge and insight into sport consumers. One outcome of this focus is that the vast majority of research on sport consumers has centered on psychological characteristics of these sport experiences related to evaluative and affective components. In addition, this research has predominately relied on cross-sectional studies and attitudinal surveys to collect information with less emphasis on how various situational or environmental factors can influence attitudinal data patterns at the individual and group level. This special issue seeks to deepen our understanding of SCB by providing seven papers that demonstrate or validate findings using multiple studies or data collections
ANALYSIS OF HUMAN MOTION WITH METHODS FROM MACHINE LEARNING
Usually, predefined kinematic parameters are investigated in biomechanical studies of human motion. In recent years, techniques of machine learning have been added to this field of research (Chau, 2001). In this study different dimension reduction methods like Principal Component Analysis (PCA) and Fourier Transformation (FT) are investigated as an alternative to common biomechanical approaches in motion analysis
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Processability of high strength Aluminum-Copper alloys AW-2022 and 2024 by Laser Beam Melting in Powder Bed
Additive Manufacturing offers geometric freedom excellently suited for topology
optimized light weight designs. Ideally these should be produced from materials of high strength
to weight ratio such as aluminium-copper alloys. Yet these are considered unsuitable for welding.
With Laser Beam Melting of Metals in powder bed (LBM), the only class of aluminium alloys
widely processed is that of aluminium-silicon alloys, which are easily weldable and castable, too.
In this contribution we present results of LBM high-strength aluminium-copper alloys AW-2022
and AW-2024 under variation of laser power, scan speed and hatch distance. We achieved
relative densities well above 99 %. We analyzed thin walls, compared process windows as well
as microstructures observed using etched metallographic microsections. We analyzed the
chemical constitution of powders and produced samples using ICP-OES.Mechanical Engineerin
Next-to-leading order multi-leg processes for the Large Hadron Collider
In this talk we discuss recent progress concerning precise predictions for
the LHC. We give a status report of three applications of our method to deal
with multi-leg one-loop amplitudes: The interference term of Higgs production
by gluon- and weak boson fusion to order O(alpha^2 alpha_s^3) and the
next-to-leading order corrections to the two processes pp -> ZZ jet and u ubar
-> d dbar s sbar. The latter is a subprocess of the four jet cross section at
the LHC.Comment: 6 pages, 5 figures. Talk given at the 8th international Symposium on
Radiative Corrections (RADCOR), October 1-5 2007, Florence, Ital
Spectroscopy of electronic defect states in Cu(In, Ga)(S, Se)-based heterojunctions and Schottky diodes under damp-heat exposure
The changes of defect characteristics induced by accelerated lifetime tests
on the heterostructure n-ZnO/i-ZnO/CdS/Cu(In, Ga)(S, Se)/Mo relevant for
photovoltaic energy conversion are investigated. We subject heterojunction and
Schottky devices to extended damp heat exposure at 85C ambient
temperature and 85% relative humidity for various time periods. In order to
understand the origin of the pronounced changes of the devices, we apply
current--voltage and capacitance--voltage measurements, admittance
spectroscopy, and deep-level transient spectroscopy. The fill factor and
open-circuit voltage of test devices are reduced after prolonged damp heat
treatment, leading to a reduced energy conversion efficiency. We observe the
presence of defect states in the vicinity of the CdS/chalcopyrite interface.
Their activation energy increases due to damp heat exposure, indicating a
reduced band bending at the Cu(In, Ga)(S, Se) surface. The Fermi-level
pinning at the buffer/chalcopyrite interface, maintaining a high band bending
in as-grown cells, is lifted due to the damp-heat exposure. We also observe
changes in the bulk defect spectra due to the damp-heat treatment.Comment: 4 pages, 5 figure
Climate change and its effect on agriculture, water resources and human health sectors in Poland
Multi-model ensemble climate projections in the ENSEMBLES Project of the EU allowed the authors to quantify selected extreme-weather indices for Poland, of importance to climate impacts on systems and sectors. Among indices were: number of days in a year with high value of the heat index; with high maximum and minimum temperatures; length of vegetation period; and number of consecutive dry days. Agricultural, hydrological, and human health indices were applied to evaluate the changing risk of weather extremes in Poland in three sectors. To achieve this, model-based simulations were compared for two time horizons, a century apart, i.e., 1961–1990 and 2061–2090. Climate changes, and in particular increases in temperature and changes in rainfall, have strong impacts on agriculture via weather extremes – droughts and heat waves. The crop yield depends particularly on water availability in the plant development phase. To estimate the changes in present and future yield of two crops important for Polish agriculture i.e., potatoes and wheat, some simple empirical models were used. For these crops, decrease of yield is projected for most of the country, with national means of yield change being: –2.175 t/ha for potatoes and –0.539 t/ha for wheat. Already now, in most of Poland, evapotranspiration exceeds precipitation during summer, hence the water storage (in surface water bodies, soil and ground) decreases. Summer precipitation deficit is projected to increase considerably in the future. The additional water supplies (above precipitation) needed to use the agro-potential of the environment would increase by half. Analysis of water balance components (now and in the projected future) can corroborate such conclusions. As regards climate and health, a composite index, proposed in this paper, is a product of the number of senior discomfort days and the number of seniors (aged 65+). The value of this index is projected to increase over 8-fold during 100 years. This is an effect of both increase in the number of seniors (over twofold) and the number of senior-discomfort days (nearly fourfold)
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