2,078 research outputs found
Spectral Efficiency of One-Bit Sigma-Delta Massive MIMO
We examine the uplink spectral efficiency of a massive MIMO base station employing a one-bit Sigma-Delta ( \Sigma \Delta ) sampling scheme implemented in the spatial rather than the temporal domain. Using spatial rather than temporal oversampling, and feedback of the quantization error between adjacent antennas, the method shapes the spatial spectrum of the quantization noise away from an angular sector where the signals of interest are assumed to lie. It is shown that, while a direct Bussgang analysis of the \Sigma \Delta approach is not suitable, an alternative equivalent linear model can be formulated to facilitate an analysis of the system performance. The theoretical properties of the spatial quantization noise power spectrum are derived for the \Sigma \Delta array, as well as an expression for the spectral efficiency of maximum ratio combining (MRC). Simulations verify the theoretical results and illustrate the significant performance gains offered by the \Sigma \Delta approach for both MRC and zero-forcing receivers
Hard breakup of the deuteron into two Delta-isobars
We study high energy photodisintegration of the deuteron into two
-isobars at large center of mass angles within the QCD hard
rescattering model (HRM). According to the HRM, the process develops in three
main steps: the photon knocks the quark from one of the nucleons in the
deuteron; the struck quark rescatters off a quark from the other nucleon
sharing the high energy of the photon; then the energetic quarks recombine into
two outgoing baryons which have large transverse momenta. Within the HRM, the
cross section is expressed through the amplitude of scattering which we evaluated based on the quark-interchange
model of hard hadronic scattering. Calculations show that the angular
distribution and the strength of the photodisintegration is mainly determined
by the properties of the
scattering. We predict that the cross section of
the deuteron breakup to is 4-5 times larger than that
of the breakup to the channel. Also, the angular
distributions for these two channels are markedly different. These can be
compared with the predictions based on the assumption that two hard
-isobars are the result of the disintegration of the preexisting
components of the deuteron wave function. In this case, one
expects the angular distributions and cross sections of the breakup in both and channels to be similar.Comment: 17 pages, 3 figure
Mean-Reverting Stochastic Processes, Evaluation of Forward Prices and Interest Rates
We consider mean-reverting stochastic processes and build self-consistent models for forward price dynamics and some applications in power industries. These models are built using the ideas and equations of stochastic differential geometry in order to close the system of equations for the forward prices and their volatility. Some analytical solutions are presented in the one factor case and for specific regular forward price/interest rates volatility. Those models will also play a role of initial conditions for a stochastic process describing forward price and interest rates volatility. Subsequently, the curved manifold of the internal space i.e. a discrete version of the bond term space (the space of bond maturing) is constructed. The dynamics of the point of this internal space that correspond to a portfolio of different bonds is studied. The analysis of the discount bond forward rate dynamics, for which we employed the Stratonovich approach, permitted us to calculate analytically the regular and the stochastic volatilities. We compare our results with those known from the literature.: Stochastic Differential Geometry, Mean-Reverting Stochastic Processes and Term Structure of Specific (Some) Economic/Finance Instruments
Quantifying Flexibility Real Options Calculus
We expose a real options theory as a tool for quantifying the value of the operating flexibility of real assets. Additionally, we have pointed out that this theory is an appropriated methodology for determining optimal operating policies, and provide an example of successful application of our approach to power industries, specifically to valuate the power plant of electricity. In particular by increasing the volatility of prices will eventually lead to higher assets values.real options, Black-Scholes Approach, Wiener processes, stochastic processes, Quantifying Flexibility, volatility
QCD Structure of Nuclear Interactions
This dissertation investigated selected processes involving baryons and
nuclei in hard scattering reactions. Through these processes, this work
explored the constituent structure of baryons and the mechanisms through which
the interactions between these constituents ultimately control the selected
reactions. First, hard nucleon-nucleon elastic scattering was studied
considering the quark exchange (QE) between the nucleons to be the dominant
mechanism of interaction in the constituent picture. It was found that an
angular asymmetry exhibited by proton-neutron (pn) elastic scattering data is
explained within this framework if a quark-diquark picture dominates the
nucleon's structure instead of a more traditional SU(6) model. The latter
yields an asymmetry around 90 deg center of mass scattering with a sign
opposite to what is experimentally observed. The second process is the hard
breakup by a photon of a nucleon-nucleon system in light nuclei. Proton-proton
(pp) and pn breakup in 3He, and double Delta-isobars production in deuteron
breakup were analyzed in the hard rescattering model (HRM), which in
conjunction with the QE mechanism provides a QCD description of the reaction.
Cross sections for both channels in 3He photodisintegration were computed
without the need of a fitting parameter. The results presented here for pp
breakup show excellent agreement with recent experimental data. In double
Delta-isobars production in deuteron breakup, HRM angular distributions for the
two double Delta channels were compared to the pn channel and to each other. An
important prediction from this study is that the Delta++ Delta- channel
consistently dominates Delta+Delta0, which is in contrast with models that
unlike the HRM consider a double Delta system in the initial state of the
interaction. For such models both channels should have the same strength.Comment: http://digitalcommons.fiu.edu/etd/44
Proposal of a novel design for linear superconducting motor using 2G tape stacks
This paper presents a new design for a su-
perconducting linear motor (SLM). This SLM uses stacks
of second-generation (2G) superconducting tapes, which
are responsible for replacing yttrium barium copper oxide
bulks. The proposed SLM may operate as a synchronous
motor or as a hysteresis motor, depending on the load
force magnitude. A small-scale linear machine prototype
with 2G stacks was constructed and tested to investigate
the proposed SLM topology. The stator traveling magnetic
field wave was represented by several Nd-Fe-B permanent
magnets. A relative movement was produced between the
stator and the stack, and the force was measured along the
displacement. This system was also simulated by the finite
element method, in order to calculate the induced currents
in the stack and determine the electromagnetic force. The
H-formulation was used to solve the problem, and a power
law relation was applied to take into account the intrin-
sically nonlinearity of the superconductor. The simulated
and measured results were in accordance. Simulated re-
sults were extrapolated, proving to be an interesting tool to
scale up the motor in future projects. The proposed motor
presented an estimated force density of almost 500 N/kg,
which is much higher than any linear motor.This work was supported in part by the following agencies: CNPq/CAPES/INERGE, CNPqâCi Ë encias sem Fronteiras, FAPERJ, Catalan Government 2014- SGR-753, CONSOLIDER Excellence Network MAT2014-56063-C2-1-R and MAT2015-68994-REDC, Eurofusion EU COST ACTIONS MP1201/ MP1014/PPPT-WPMAG 2014, EUROTAPES FP7-NMP-Large-2011- 280432, FORTISSIMO FP7-2013-ICT-609029, and Spanish Govern- ment AgenciesâSevero Ochoa Programme Centres of Excellence in R&D. (Corresponding author: Guilherme G. Sotelo.
Adaptive detection probability for mmWave 5G SLAM
In 5G simultaneous localization and mapping (SLAM), estimates of angles and delays of mm Wave channels are used to localize the user equipment and map the environment. The interface from the channel estimator to the SLAM method, which was previously limited to the channel parameters estimates and their uncertainties, is here augmented to include the detection probabilities of hypothesized landmarks, given certain a user location. These detection probabilities are used during data association and measurement update, which are important steps in any SLAM method. Due to the nature of mm Wave communication, these detection probabilities depend on the physical layer signal parameters, including beamforming, precoding, bandwidth, observation time, etc. In this paper, we derive these detection probabilities for different deterministic and stochastic channel models and highlight the importance of beamforming
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