Background Components Research Articles

Measurements of the total cross section of nat Be with thermal neutrons from a photo-neutron source

Abstract The total neutron cross sections of natural beryllium in the neutron energy region of 0.007 to 0.1 eV were measured by using a time-of-flight (TOF) technique at the Shanghai Institute of Applied Physics (SINAP). The low energy neutrons were obtained by moderating the high energy neutrons from a pulsed photo-neutron source generated from a 16 MeV electron linac. The time dependent neutron background component was determined by employing the 12.8 cm boron-loaded polyethylene (PEB) (5% w.t.) to block neutron TOF path and using the Monte Carlo simulation methods. The present data was compared with the fold Harvey data with the response function of the photo-neutron source (PNS, phase-1). The present measurement of total cross section of natBe for thermal neutrons based on PNS has been developed for the acquisition of nuclear data needed for the Thorium Molten Salt Reactor (TMSR).

Background model for the Majorana Demonstrator

The Majorana Collaboration is constructing a system containing 44 kg of high-purity Ge (HPGe) detectors to demonstrate the feasibility and potential of a future tonne-scale experiment capable of probing the neutrino mass scale to ∼15 meV. To realize this, a major goal of the Majorana Demonstrator is to demonstrate a path forward to achieving a background rate at or below 1 count/(ROI-t-y) in the 4 keV region of interest (ROI) around the Q-value at 2039 keV. This goal is pursued through a combination of a significant reduction of radioactive impurities in construction materials and analytical methods for background rejection, for example using powerful pulse shape analysis techniques profiting from the p-type point contact (PPC) HPGe detectors technology. The effectiveness of these methods is assessed using simulations of the different background components whose purity levels are constrained from radioassay measurements. Preliminary background results obtained during the engineering runs of the Demonstrator are presented.

Aero-elastic testing of multi-spanned transmission line subjected to downbursts

This paper reports the first aero-elastic test conducted under a scaled downburst wind field at the WindEEE dome facility at the University of Western Ontario, Canada. The main purpose of the test is to assess the dynamic response of a multi-span transmission line. The study starts by providing a characterization of the downburst wind field produced in WindEEE including a comparison with results of previously conducted numerical simulations. A number of test configurations, involving different locations of the downburst relative to the line, is considered. A decomposition approach is developed to separate between the resonant and the background components of the response. The results are presented in the form of a dynamic magnification factor that relates the peak response including the dynamic effect to the maximum quasi-static response. The test results show that the resonance contribution ranges between 5% and 10% of the peak response for the tower. They also show that the dynamic response of the conductors can reach up to 30% and 12% of the peak response at low and high downburst speeds, respectively.

Efficient scattering-angle enrichment for a nonlinear inversion of the background and perturbations components of a velocity model

Efficient scattering-angle enrichment for a nonlinear inversion of the background and perturbations components of a velocity model

Filtering of images of small-sized objects in systems with circular microscaning

This paper describes a model for detection of images obtained in circular microscanning. To detect objects on a low background with the use of an image detection system based on circular microscanning, an approach to image filtering is proposed. The calculation of the noise covariance matrix with respect to the data obtained by the numerical simulation method is used. The calculated matrix is used in filter construction. It is shown that the applied approach makes it possible to increase the signal/noise ratio in image processing with a low background component.

Coupled wind-induced responses and equivalent static wind loads on long-span roof structures with the consistent load–response–correlation method

Long-span roof structures with multiple vibration modes may undergo coupled motions when exposed to spatiotemporally varying dynamic wind loads. This article presents a framework for the analysis of coupled wind-induced responses and equivalent static wind loads on long-span roof structures. This framework takes into account the inter-modal coupling of modal response components and cross correlation between the background and resonance. The load–response–correlation method is widely used for the background equivalent static wind loads of rigid structures. Also, the concept of load–response–correlation was extended for the correct estimation of equivalent static wind loads by considering the correlation between the load and exact total responses. However, there is no detailed study for the correct estimation of equivalent static wind loads on the component of background, resonance, and their cross response using load–response–correlation method. In this article, a consistent load–response–correlation method for equivalent static wind loads is presented in a unified framework which contains the background, resonance, and modal coupling. First, the accuracy of wind-induced responses is ensured by considering the modal coupling. Meanwhile, the efficiency is improved by decomposing the covariance matrix of the generalized resuming forces. Second, several effects of the wind-induced responses are discussed in detail, such as the effect of the modal coupling, the effect of the modal participations to resonant responses, and the effect of the cross correlation between the background and resonance. Finally, the proposed equivalent static wind loads are represented by the composition of the external wind loads and inertial forces, which are both the most probable load distributions. Accordingly, the equivalent static wind load distribution and the responses by equivalent static wind loads are reasonable.

A systematic analysis of the XMM-Newton background: I. Dataset and extraction procedures

XMM-Newton is the direct precursor of the future ESA ATHENA mission. A study of its particle-induced background provides therefore significant insight for the ATHENA mission design. We make use of about 12 years of data, products from the third XMM-Newton catalog as well as FP7 EXTraS project to avoid celestial sources contamination and to disentangle the different components of the XMM-Newton particle-induced background. Within the ESA R&D AREMBES collaboration, we built new analysis pipelines to study the different components of this background: this covers time behavior as well as spectral and spatial characteristics.

Particular spectral singularity in the continuum energies: a manifestation as resonances

We study the coalescence of two bound energy eigenstates embedded in the continuous spectrum of a real Hamiltonian HW and the singular point produced by this coalescence. At the singular point, the two unnormalized Jost eigenfunctions are no longer linearly independent but coalesce to give rise to a bound state eigenfunction embedded in the continuum. We disturb the potential VW by means of a truncation; this perturbation breaks the singular point in two resonances. The phase shift shows a jump of magnitude and the shape of the cross section shows two inverted peaks; this behaviour is due to the interference between the two nearly degenerate resonances and the background component of the Jost function.

Modelling of tropospheric delays in geosynchronous synthetic aperture radar

As a direct consequence of the orbital height, the integration time in geosynchronous synthetic aperture radar (GEO SAR) with metric or decimetric azimuth resolutions is in the order of several hundreds or even thousands of seconds. With such long integration time, the compensation of residual tropospheric propagation terms poses one of the fundamental challenges associated with GEO SAR missions. In order to better characterise the impact of the propagation errors on GEO SAR imaging, we put forward a model for the simulation of the tropospheric delay appropriate for the accurate simulation of GEO SAR surveys. The suggested model, with a deterministic background component and a random turbulent one, incorporates some of the most recent meteorological data for the characterization of the troposphere. To illustrate the relevance of the derivation, the suggested model is used for performance estimation and raw data simulation of GEO SAR raw data. Substantialconclusion on the system impulse response and the associatedcalibration requirements is also drawn from the analysis.

Prediction of wind-induced buffeting response of overhead conductor: Comparison of linear and nonlinear analysis approaches

This study addresses the estimation of buffeting response of overhead conductor based on random vibration theory with closed-form formulations. Special attention is placed on the determination of static deformation with consideration of geometric nonlinearity, and its influence on the dynamic modal properties, aerodynamic modal damping and buffeting response. The dynamic response around the static equilibrium is separated into background and resonant components, which are calculated by using influence function and modal analysis, respectively. The aerodynamic modal damping ratios are estimated in closed-form formulations in which the influence of static swing of the conductor plane is explicitly accounted. Example studies presented in this study illustrate the accuracy and effectiveness of this linear buffeting analysis framework through comparison with nonlinear finite element model (FEM) analysis in the time domain. The importance of consideration of static deformation is revealed for the prediction of alongwind displacement and tension, especially, the resonant response component. The contributions of modal responses to various resonant responses are also examined.

(Invited) Recent Advances in SWCNT Analytical Spectroscopy

Since the 2002 assignment of absorption and emission transitions to specific (n,m) structures, optical spectroscopy has offered the potential for simple, detailed structure-resolved characterization of SWCNT samples. However, this goal has not been fully realized because of incomplete spectroscopic and photophysical knowledge and a lack of specialized instrumentation. We describe here recent progress in overcoming these problems to enable quantitative sample analysis through combined fluorescence and absorption spectroscopy. One important step was determining absolute E11 absorption cross sections (molar absorptivities) for a number of common (n,m) species. This was achieved by using a direct counting method to calibrate the absolute concentrations of reference samples, and then by extending the list of measured cross sections through variance spectroscopy determinations of (n,m)-resolved particle concentrations in mixed samples. To properly interpret fluorimetric data, we have measured, interpreted, and modeled emission spectra and excitation spectra for a range of semiconducting (n,m) species. Combinations of single particle and ensemble spectroscopies were used for these studies. The models were extrapolated to other (n,m) species to predict E11 line widths and shapes plus the positions, amplitudes, and widths of spectral sidebands. When combined with data on structure-dependent fluorimetric efficiencies, the results allow fluorescence spectra of nanotube mixtures to be simulated as a sum of contributions from multiple (n,m) species of determined relative concentrations. To convert those concentrations from relative into absolute values, the absorption spectrum of a mixed sample is simulated as a background function plus components determined from the fluorescence emission and excitation profiles for the (n,m) species that were found to be present. Then the separate E11 (n,m) absorbance components are divided by their structure-specific absorption cross sections to find absolute species concentrations. The overall process allows quantitation of semiconducting (n,m) concentrations from simple and quick spectral measurements.

A spectral-spatial method based on low-rank and sparse matrix decomposition for hyperspectral anomaly detection

ABSTRACTRecently, some methods based on low-rank and sparse matrix decomposition (LRASMD) have been developed to improve the performance of hyperspectral anomaly detection (AD). However, these methods mainly take advantage of the spectral information in hyperspectral imagery (HSI), and ignore the spatial information. This article proposes an LRASMD-based spectral-spatial (LS-SS) method for hyperspectral AD. First, the Go Decomposition (GoDec) algorithm is employed to solve the low-rank background component and the sparse anomaly component. Next, the sparse component is explored to calculate the spectral sparsity divergence index (SDI). Based on spectral SDI, the detection result in the spectral domain and the reliable background points, which are employed as training data to construct the background manifold by linear local tangent space alignment (LLTSA), can also be obtained. Then, based on the background manifold and the transformation matrix, the low-dimensional manifold of the whole data is computed by linear mapping. After that, the kernel collaborative representation detector (KCRD) is used in the low-dimensional manifold of the whole data for the spatial SDI. Finally, SS SDI is computed for the final detection result. The theoretical analysis and experimental results demonstrate that the proposed LS-SS can achieve better performance when compared with the comparison algorithms.

River channel segmentation in polarimetric SAR images: Watershed transform combined with average contrast maximisation

This publication presents a computer method allowing river channels to be segmented based on SAR polarimetric images. Solutions have been proposed which are based on a morphological approach using the watershed segmentation and combining regions by maximising the average contrast. The image processing methods were developed so that their computational complexity is as low as possible, which is of particular importance in analysing high resolution SAR/polarimetric SAR images, where it has a measurable impact on the total segmentation time. What is more, compared to the existing solutions known from the literature review: (1) in the proposed approach, there is no need to execute further steps necessary to eliminate objects (i.e. background components) located outside the river channel from the image as a result of the segmentation carried out, (2) there is no need to sample the entire image and carry out a pixel–wise classification to prepare the segmentation process. If the steps listed in items (1) – (2) are performed, they can, unfortunately, extend the segmentation time. The experiments completed on images acquired from the ALOS PALSAR satellite for different regions of the world have shown a high quality of the segmentations carried out and a high computational efficiency compared to state–of–the art methods. Consequently, the proposed method can be used as a useful tool for monitoring changes in river courses and adopted in expert and intelligent systems used for analysing remote sensing data.

Nicotine Population Pharmacokinetics in Healthy Adult Smokers: A Retrospective Analysis.

Background and ObjectiveCharacterizing nicotine pharmacokinetics is challenging in the presence of background exposure. We performed a combined retrospective population pharmacokinetic analysis of 8 trials, including exposure to Tobacco Heating System and cigarettes (both inhaled), nicotine nasal spray and oral nicotine gum.MethodData from 4 single product use trials were used to develop a population pharmacokinetic model with Phoenix® NLME™ and to derive exposure parameters. Data from 4 separate ad libitum use studies were used for external validation. A total of 702 healthy adult smokers (54% males; 21–66 years of age; smoking ≥10 cigarettes/day; from US, Europe and Japan) were eligible for participation.ResultsTwo-compartment linear disposition combined with zero-order absorption model was adequate to describe nicotine pharmacokinetics, and a mono-exponentially decreasing background component was utilized to account for nicotine carry-over effects. Apparent nicotine clearance was typically 0.407 L/min in males and 26% higher in females (68% inter-individual variability). Bioavailability was product-specific, decreased with increasing nicotine ISO yield, and increased with increasing body weight. Absorption duration was apparently prolonged with nicotine gum. The typical initial and terminal half-lives were 1.35 and 17 h, respectively. The presence of menthol did not impact the determinants of the area under the curve. The model adequately described the external validation data.ConclusionsThe population model was able to describe in different populations the nicotine pharmacokinetics after single product use and after 4 days of ad libitum use of Tobacco Heating System, cigarettes, and of different nicotine replacement therapies with various routes of administration.Electronic supplementary materialThe online version of this article (doi:10.1007/s13318-017-0405-2) contains supplementary material, which is available to authorized users.

Evidence against Star-forming Galaxies as the Dominant Source of Icecube Neutrinos

Abstract The cumulative emission resulting from hadronic cosmic-ray interactions in star-forming galaxies (SFGs) has been proposed as the dominant contribution to the astrophysical neutrino flux at TeV to PeV energies reported by IceCube. The same particle interactions also inevitably create γ-ray emission that could be detectable as a component of the extragalactic γ-ray background (EGB), which is now measured with the Fermi-LAT in the energy range from 0.1 to 820 GeV. New studies of the blazar flux distribution at γ-ray energies above 50 GeV place an upper bound on the residual non-blazar component of the EGB. We show that these results are in strong tension with models that consider SFGs as the dominant source of the diffuse neutrino backgrounds. A characteristic spectral index for parent cosmic rays in starburst galaxies of ΓSB ≃ 2.3 for dN / dE ∝ E − Γ SB is consistent with the observed scaling relation between γ-ray and IR luminosity for SFGs, the bounds from the non-blazar EGB, and the observed γ-ray spectra of individual starbursts, but underpredicts the IceCube data by approximately an order of magnitude.

Monte Carlo simulation of background characteristics of a HPGe detector operating underground in the Gran Sasso National Laboratory

Monte Carlo (MC) simulation of background components of an ultra-low background high purity germanium (HPGe) detector operating in a deep underground laboratory was carried out. The results show that the background of the HPGe detector is about two orders of magnitude higher than the MC prediction when accounting only for cosmic-ray induced background. The difference is due to natural radioactivity in the parts surrounding the Ge detector. To get reasonable agreement between MC simulations and the experiment, a contamination in the parts surrounding the Ge crystal from 40K, 208Tl and 214Bi of 0.1mBqkg−1 was required to include in the simulations.

A CO-based method to determine the regional biospheric signal in atmospheric CO2

Regional-scale inverse modeling of atmospheric carbon dioxide (CO2) holds promise to determine the net CO2 fluxes between the land biosphere and the atmosphere. This approach requires not only high fidelity of atmospheric transport and mixing, but also an accurate estimation of the contribution of the anthropogenic and background CO2 signals to isolate the biospheric CO2 signal from the atmospheric CO2 variations. Thus, uncertainties in any of these three components directly impact the quality of the biospheric flux inversion. Here, we present and evaluate a carbon monoxide (CO)-based method to reduce these uncertainties solely on the basis of co-located observations. To this end, we use simultaneous observations of CO2 and CO from a background observation site to determine the background mole fractions for both gases, and the regional anthropogenic component of CO together with an estimate of the anthropogenic CO/CO2 mole fraction ratio to determine the anthropogenic CO2 component. We apply this method to two sites of the CarboCount CH observation network on the Swiss Plateau, Beromünster and Lägern-Hochwacht, and use the high-altitude site Jungfraujoch as background for the year 2013. Since such a background site is not always available, we also explore the possibility to use observations from the sites themselves to derive the background. We contrast the method with the standard approach of isolating the biospheric CO2 component by subtracting the anthropogenic and background components simulated by an atmospheric transport model. These tests reveal superior results from the observation-based method with retrieved wintertime biospheric signals being small and having little variance. Both observation- and model-based methods have difficulty to explain observations from late-winter and springtime pollution events in 2013, when anomalously cold temperatures and northeasterly winds tended to bring highly CO-enriched air masses to Switzerland. The uncertainty of anthropogenic CO/CO2 emission ratios is currently the most important factor limiting the method. Further, our results highlight that care needs to be taken when the background component is determined from the site’s observations. Nonetheless, we find that future atmospheric carbon monitoring efforts would profit greatly from at least measuring CO alongside CO2.

Physical Layer Security Over Correlated Log-Normal Cooperative Power Line Communication Channels

Power line communication (PLC) has enabled many smart grid applications and functionalities over the past few years. Secure communications over such links however remain a crucial aspect for further development. Due to their shared nature, akin to wireless, PLC channels can benefit from many wireless-type security techniques, including physical layer security. To this end, and in contrast to existing studies, which focus on non-cooperative PLC systems, this paper considers the application of physical layer security in cooperative PLC networks in the presence of passive eavesdropping. We analyze the performance of such systems using log-normal correlated channel models considering background and impulsive noise components. Furthermore, the impact of PLC/wireless coding diversity on the system secrecy capacity is evaluated. The results include accurate mathematical expressions for providing an insight into the secrecy capacity and outage probability performance of such systems under various network scenarios.

Determining the Coupling Source on a Set of Oscillators from Experimental Data

Complex systems are a broad concept that comprises many disciplines, including engineering systems. Regardless of their particular behavior, complex systems share similar behaviors, such as synchronization. This paper presents different techniques for determining the source of coupling when a set of oscillators synchronize. It is possible to identify the location and time variations of the coupling by applying a combination of analytical techniques, namely, the source of synchronization. For this purpose, the analysis of experimental data from a complex mechanical system is presented. The experiment consisted in placing a 24-bladed rotor under an airflow. The vibratory motion of the blades was recorded with accelerometers, and the resulting information was analyzed with four techniques: correlation coefficients, Kuramoto parameter, cross-correlation functions, and the recurrence plot. The measurements clearly show the existence of frequencies due to the foreground components and the internal interaction between them due to the background components (coupling).

Further Improvement of the RITS Code for Pulsed Neutron Bragg-edge Transmission Imaging

The RITS code is a unique and powerful tool for a whole Bragg-edge transmission spectrum fitting analysis. However, it has had two major problems. Therefore, we have proposed methods to overcome these problems. The first issue is the difference in the crystallite size values between the diffraction and the Bragg-edge analyses. We found the reason was a different definition of the crystal structure factor. It affects the crystallite size because the crystallite size is deduced from the primary extinction effect which depends on the crystal structure factor. As a result of algorithm change, crystallite sizes obtained by RITS drastically approached to crystallite sizes obtained by Rietveld analyses of diffraction data; from 155% to 110%. The second issue is correction of the effect of background neutrons scattered from a specimen. Through neutron transport simulation studies, we found that the background components consist of forward Bragg scattering, double backward Bragg scattering, and thermal diffuse scattering. RITS with the background correction function which was developed through the simulation studies could well reconstruct various simulated and experimental transmission spectra, but refined crystalline microstructural parameters were often distorted. Finally, it was recommended to reduce the background by improving experimental conditions.