794 research outputs found
Norm minimized Scattering Data from Intensity Spectra
We apply the minimizing technique of compressive sensing (CS) to
non-linear quadratic observations. For the example of coherent X-ray scattering
we provide the formulae for a Kalman filter approach to quadratic CS and show
how to reconstruct the scattering data from their spatial intensity
distribution.Comment: 26 pages, 10 figures, reordered section
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Impacts of variable renewable energy on wholesale markets and generating assets in the United States: A review of expectations and evidence
We synthesize available literature, data, and analysis on the degree to which growth in variable renewable energy (VRE) has impacted or might in the future impact bulk power system assets, pricing, and costs in the United States. Most studies of future scenarios indicate that VRE reduces wholesale energy prices and capacity factors of thermal generators. Traditional baseload generators are more exposed to these changing market conditions than low-capital cost and more flexible intermediate and peak-load generators. From analysis of historical data we find that VRE is already influencing the bulk power market through changes in temporal and geographic patterns areas with higher levels of VRE. The most significant observed impacts have concentrated in areas with significant VRE and/or nuclear generation along with limited transmission, with negative pricing also often occurring during periods with lower system-wide load. So far, however, VRE, has had a relatively modest impact on historical average annual wholesale prices across entire market regions, at least in comparison to other drivers. The reduction of natural gas prices is the primary contributor to the decline in wholesale prices since 2008. Similarly, VRE impacts on thermal plant retirements have been limited and there is little relationship between the location of recent retirements and VRE penetration levels. Although impacts on wholesale prices have been modest so far, impacts of VRE on the electricity market will be more significant under higher VRE penetrations
Study of chiral symmetry restoration in linear and nonlinear O(N) models using the auxiliary field method
We consider the O(N) linear {\sigma} model and introduce an auxiliary field
to eliminate the scalar self-interaction. Using a suitable limiting process
this model can be continuously transformed into the nonlinear version of the
O(N) model. We demonstrate that, up to two-loop order in the CJT formalism, the
effective potential of the model with auxiliary field is identical to the one
of the standard O(N) linear {\sigma} model, if the auxiliary field is
eliminated using the stationary values for the corresponding one- and two-point
functions. We numerically compute the chiral condensate and the {\sigma}- and
{\pi}-meson masses at nonzero temperature in the one-loop approximation of the
CJT formalism. The order of the chiral phase transition depends sensitively on
the choice of the renormalization scheme. In the linear version of the model
and for explicitly broken chiral symmetry, it turns from crossover to first
order as the mass of the {\sigma} particle increases. In the nonlinear case,
the order of the phase transition turns out to be of first order. In the region
where the parameter space of the model allows for physical solutions,
Goldstone's theorem is always fulfilled.Comment: 25 pages, 9 figures, 1 table, improved versio
Excitation spectrum of bosons in a finite one-dimensional circular waveguide via the Bethe ansatz
The exactly solvable Lieb-Liniger model of interacting bosons in
one-dimension has attracted renewed interest as current experiments with
ultra-cold atoms begin to probe this regime. Here we numerically solve the
equations arising from the Bethe ansatz solution for the exact many-body wave
function in a finite-size system of up to twenty particles for attractive
interactions. We discuss the novel features of the solutions, and how they
deviate from the well-known string solutions [H. B. Thacker, Rev. Mod. Phys.\
\textbf{53}, 253 (1981)] at finite densities. We present excited state string
solutions in the limit of strong interactions and discuss their physical
interpretation, as well as the characteristics of the quantum phase transition
that occurs as a function of interaction strength in the mean-field limit.
Finally we compare our results to those of exact diagonalization of the
many-body Hamiltonian in a truncated basis. We also present excited state
solutions and the excitation spectrum for the repulsive 1D Bose gas on a ring.Comment: 13 pages, 12 figure
Low temperature/short duration steaming as a sustainable method of soil disinfection
This report was presented at the UK Organic Research 2002 Conference. Soil samples containing resting structures of fungal crop pathogens (Verticillium dahliae, Sclerotinia sclerotiorum, Sclerotium cepivorum, Pythium ultimum), potato cyst nematodes (Globodera rostochiensis and Globodera pallida) and weeds (Chenopodium album and Agropyron repens) were treated with aerated steam in the laboratory at temperatures ranging from 50β80oC in a specially constructed apparatus. Steaming at 50 or 60oC for three minutes, followed by an eight-minute resting period in the steamed soil and immediate removal from the soil thereafter, resulted in 100% kill of all weeds, fungi and nematodes. Low temperature/ short duration soil steaming could become a sustainable alternative to chemical or high-temperature steam soil disinfestation
Recruitment kinetics of DNA repair proteins Mdc1 and Rad52 but not 53BP1 depend on damage complexity.
The recruitment kinetics of double-strand break (DSB) signaling and repair proteins Mdc1, 53BP1 and Rad52 into radiation-induced foci was studied by live-cell fluorescence microscopy after ion microirradiation. To investigate the influence of damage density and complexity on recruitment kinetics, which cannot be done by UV laser irradiation used in former studies, we utilized 43 MeV carbon ions with high linear energy transfer per ion (LET = 370 keV/Β΅m) to create a large fraction of clustered DSBs, thus forming complex DNA damage, and 20 MeV protons with low LET (LET = 2.6 keV/Β΅m) to create mainly isolated DSBs. Kinetics for all three proteins was characterized by a time lag period T(0) after irradiation, during which no foci are formed. Subsequently, the proteins accumulate into foci with characteristic mean recruitment times Ο(1). Mdc1 accumulates faster (T(0) = 17 Β± 2 s, Ο(1) = 98 Β± 11 s) than 53BP1 (T(0) = 77 Β± 7 s, Ο(1) = 310 Β± 60 s) after high LET irradiation. However, recruitment of Mdc1 slows down (T(0) = 73 Β± 16 s, Ο(1) = 1050 Β± 270 s) after low LET irradiation. The recruitment kinetics of Rad52 is slower than that of Mdc1, but exhibits the same dependence on LET. In contrast, the mean recruitment time Ο(1) of 53BP1 remains almost constant when varying LET. Comparison to literature data on Mdc1 recruitment after UV laser irradiation shows that this rather resembles recruitment after high than low LET ionizing radiation. So this work shows that damage quality has a large influence on repair processes and has to be considered when comparing different studies
Bis(triphenylΒphosphoΒranylΒidene)ammonium iodide
The title compound, C36H30NP2
+Β·Iβ, was obtained accidently from crystallization of a reaction mixture containing [(Ph3P)2N]OH and B(OH)3, which was contaminated with MeI. There are two independent [(Ph3P)2N]+ cations and two Iβ anions within the asymmetric unit. The central PNP angles are non-linear [137.6β
(2) and 134.4β
(2)Β°] and the phenyl substituents on P centres adopt different conformations within these two cations
Integral representations for correlation functions of the XXZ chain at finite temperature
We derive a novel multiple integral representation for a generating function
of the \s^z-\s^z correlation functions of the spin-\2 XXZ chain at finite
temperature and finite, longitudinal magnetic field. Our work combines
algebraic Bethe ansatz techniques for the calculation of matrix elements with
the quantum transfer matrix approach to thermodynamics.Comment: 33 pages, 2 figures, v2: 2 typos corrected, 1 figure adde
Analysis of the accuracy of ten algorithms for orientation estimation using inertial and magnetic sensing under optimal conditions: One size does not fit all
The orientation of a magneto and inertial measurement unit (MIMU) is estimated by means of sensor fusion algorithms (SFAs) thus enabling human motion tracking. However, despite several SFAs implementations proposed over the last decades, there is still a lack of consensus about the best performing SFAs and their accuracy. As suggested by recent literature, the filter parameters play a central role in determining the orientation errors. The aim of this work is to analyze the accuracy of ten SFAs while running under the best possible conditions (i.e., their parameter values are set using the orientation reference) in nine experimental scenarios including three rotation rates and three commercial products. The main finding is that parameter values must be specific for each SFA according to the experimental scenario to avoid errors comparable to those obtained when the de-fault parameter values are used. Overall, when optimally tuned, no statistically significant differ-ences are observed among the different SFAs in all tested experimental scenarios and the absolute errors are included between 3.8 deg and 7.1 deg. Increasing the rotation rate generally leads to a significant performance worsening. Errors are also influenced by the MIMU commercial model. SFA MATLAB implementations have been made available online
A Levenberg-Marquardt Algorithm for Sparse Identification of Dynamical Systems
Low complexity of a system model is essential for its use in real-time applications. However, sparse identification methods commonly have stringent requirements that exclude them from being applied in an industrial setting. In this article, we introduce a flexible method for the sparse identification of dynamical systems described by ordinary differential equations. Our method relieves many of the requirements imposed by other methods that relate to the structure of the model and the dataset, such as fixed sampling rates, full state measurements, and linearity of the model. The Levenberg-Marquardt algorithm is used to solve the identification problem. We show that the Levenberg-Marquardt algorithm can be written in a form that enables parallel computing, which greatly diminishes the time required to solve the identification problem. An efficient backward elimination strategy is presented to construct a lean system model.publishedVersio
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