319 research outputs found
Semi-parametric forecasts of the implied volatility surface using regression trees
We present a new semi-parametric model for the prediction of implied volatility surfaces that can be estimated using machine learning algorithms. Given a reasonable starting model, a boosting algorithm based on regression trees sequentially minimizes generalized residuals computed as differences between observed and estimated implied volatilities. To overcome the poor predictive power of existing models, we include a grid in the region of interest, and implement a cross-validation strategy to find an optimal stopping value for the boosting procedure. Back testing the out-of-sample performance on a large data set of implied volatilities from S&P 500 options, we provide empirical evidence of the strong predictive power of our mode
Look ma(rket), No Hands! Optimism Bias and Illusion of Control in Finance Professionals
The optimism bias is the tendency to judge one’s own risk as
less than the risk of others. In the present study we found that
also finance professionals (N = 60) displayed an optimism
bias when forecasting the return of an investment made by
themselves or by a colleague of the same expertise. Using a
multidimensional approach to the assessment of risk
perception, we found that participants’ forecasts were biased
not because they judged negative consequences as less likely
for themselves, but because they were overconfident in their
ability to avoid and control them
Inclusive semileptonic decays in the Standard Model and beyond
Inclusive semileptonic decays of beauty baryons are studied using the heavy
quark expansion to , at leading order in . The
case of a polarized decaying baryon is examined, with reference to .
An extension of the Standard Model effective Hamiltonian inducing transitions ( and ) is
considered, which comprises the full set of D=6 semileptonic operators with
left-handed neutrinos. The effects of the new operators in several observables
are described.Comment: 50 pages, 12 figures. Corrected a typo in eq. (B.46
Recycling of Pre-Washed Municipal Solid Waste Incinerator Fly Ash in the Manufacturing of Low Temperature Setting Geopolymer Materials
In this work, three samples of municipal solid waste incinerators fly ash (MSWI-FA) have been stabilized in systems containing coal fly ash to create geopolymers through a polycondensation reaction. Monolithic products have been obtained with both MSWI fly ash as received and after the partial removal of chloride and sulfate by water washing. The polycondensation products have been characterized qualitatively by means of Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy and quantitatively, through the determination of the volume of reacted water and silicate. Furthermore, the heavy metals and chloride releases together with the physico-mechanical properties have been evaluated on the hardened products. In conclusion, considering the technological and environmental performances of the obtained geopolymers, they could be suitable for many non-structural applications, such as backfilling of abandoned quarries, decorative materials or brick fireplaces, hearths, patios, etc
Thermal noise and optomechanical features in the emission of a membrane-coupled compound cavity laser diode
We demonstrate the use of a compound optical cavity as linear displacement
detector, by measuring the thermal motion of a silicon nitride suspended
membrane acting as the external mirror of a near-infrared Littrow laser diode.
Fluctuations in the laser optical power induced by the membrane vibrations are
collected by a photodiode integrated within the laser, and then measured with a
spectrum analyzer. The dynamics of the membrane driven by a piezoelectric
actuator is investigated as a function of air pressure and actuator
displacement in a homodyne configuration. The high Q-factor ( at mbar) of the fundamental mechanical mode at kHz guarantees a detection sensitivity high enough for direct measurement
of thermal motion at room temperature ( pm RMS). The compound cavity
system here introduced can be employed as a table-top, cost-effective linear
displacement detector for cavity optomechanics. Furthermore, thanks to the
strong optical nonlinearities of the laser compound cavity, these systems open
new perspectives in the study of non-Markovian quantum properties at the
mesoscale
Dalitz decays
The Dalitz decays of the positive parity charmed mesons,
with and ,
are important processes to investigate the nature of the states.
We analyze the full set of decays, considering the four lightest
mesons as belonging to the heavy quark spin doublets and , with the
spin-parity of the light degrees of freedom in mesons. The description implies
relations among the observables in various modes. We study the decay
distributions in the dilepton invariant mass squared and the distributions in
the angle between the charged lepton momentum and the momentum of the produced
meson, which are expressed in terms of universal form factors and of effective
strong couplings. Such measurements are feasible at the present facilities.Comment: LaTeX, 23 pages, 6 figures. Version to appear on PR
Stretching graphene using polymeric micro-muscles
The control of strain in two-dimensional materials opens exciting
perspectives for the engineering of their electronic properties. While this
expectation has been validated by artificial-lattice studies, it remains
elusive in the case of atomic lattices. Remarkable results were obtained on
nanobubbles and nano-wrinkles, or using scanning probes; microscale strain
devices were implemented exploiting deformable substrates or external loads.
These devices lack, however, the flexibility required to fully control and
investigate arbitrary strain profiles. Here, we demonstrate a novel approach
making it possible to induce strain in graphene using polymeric micrometric
artificial muscles (MAMs) that contract in a controllable and reversible way
under an electronic stimulus. Our method exploits the mechanical response of
poly-methyl-methacrylate (PMMA) to electron-beam irradiation. Inhomogeneous
anisotropic strain and out-of-plane deformation are demonstrated and studied by
Raman, scanning-electron and atomic-force microscopy. These can all be easily
combined with the present device architecture. The flexibility of the present
method opens new opportunities for the investigation of strain and
nanomechanics in two-dimensional materials
Experimental Evaluation of a Full-Scale HVAC System Working with Nanofluid
Nowadays, energy saving is considered a key issue worldwide, as it brings a variety of benefits: reducing greenhouse gas emissions and the demand for energy imports and lowering costs on a household and economy-wide level. Researchers and building designers are looking to optimize building efficiency by means of new energy technologies. Changes can also be made in existing buildings to reduce the energy consumption of air conditioning systems, even during operational conditions without dramatically modifying the system layout and have as low an impact as possible on the cost of the modification. These may include the usage of new heat transfer fluids based on nanofluids. In this work, an extended experimental campaign (from February 2020 to March 2021) has been carried out on the HVAC system of an educational building in the Campus of University of Salento, Lecce, Italy. The scope of the investigation was comparing the COP for the two HVAC systems (one with nanofluid and the other one without) operating concurrently during winter and summer: simultaneous measurements on the two HVAC systems show that the coefficient of performance (COP) with nanofluid increased on average by 9.8% in winter and 8.9% in summer, with average daily peaks of about 15%. Furthermore, the comparison between the performance of the same HVAC system, working in different comparable periods with and without nanofluids, shows a mean increase in COP equal to about 13%
Flavour anomalies, correlations, hadronic uncertainties, and all that
We present a short overview of the so-called flavour anomalies, discussing
their significance and the connections with QCD issues discussed at the HADRON
2023 conference.Comment: LaTeX, 6 pages + references, 3 figures. Plenary talk at HADRON 2023,
Genova 5-9 June 2023. To appear in the proceeding
Object-based audio reproduction and the audio scene description format
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.The introduction of new techniques for audio reproduction such as HRTF-based technology, wave field synthesis and higher-order Ambisonics is accompanied by a paradigm shift from channel-based to object-based transmission and storage of spatial audio. Not only is the separate coding of source signal and source location more efficient considering the number of channels used for reproduction by large loudspeaker arrays, it also opens up new options for a user-controlled interactive sound field design. This article describes the need for a common exchange format for object-based audio scenes, reviews some existing formats with potential to meet some of the requirements and finally introduces a new format called Audio Scene Description Format (ASDF) and presents the SoundScape Renderer, an audio reproduction software which implements a draft version of the ASDF
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