Relative Position Of Source Research Articles

SEASum: Syntax-Enriched Abstractive Summarization

Compared to traditional RNN-based models, abstractive summarization systems based on Pre-trained Language Models (PTMs) achieve dramatic improvements in readability. Thus, in the field of abstractive summarization, more attention should be devoted to the faithfulness issue that predicted summaries are not factually consistent with source texts. To alleviate this disadvantage, we propose a novel Syntax-Enriched Abstractive Summarization (SEASum) framework, which utilizes graph attention networks (GATs) to introduce syntactic features of source texts to generate faithful summaries. In the SEASum framework, the PTM-based semantic encoder encodes word sequence, while the GAT-based syntactic encoder captures explicit syntax, i.e., part-of-speech tags, parse trees, and dependency-based relative positions of source documents. A feature fusion module is introduced to incorporate encoded syntactic features into the summarization framework. Based on the proposed SEASum framework, we develop two summarization models: 1) parallel SEASum model, in which the semantic encoder and syntactic encoder work in parallel, a multi-head attention module fused two-stream features for the following decoding process; 2) cascaded SEASum model, which takes contextual word embeddings from semantic encoder as node embeddings for the syntactic encoder and employs highway networks to regulate information flow. Experimental results on CNN/DailyMail and Reddit-TIFU (short) datasets show our parallel SEASum model and cascaded SEASum model outperform state-of-the-art abstractive summarization approaches in the faithfulness measurement. The results also demonstrate that cascaded SEASum model is more effective than parallel SEASum model in boosting faithfulness.

Dosimetry of a novel converging X-ray source for kilovoltage radiotherapy.

The objective of this work was to evaluate phantom dosimetry of a novel kilovoltage (kV) X-ray source, which employs a stationary tungsten anode and a linearly swept scanning electron beam. The source utilizes converging X-ray collimation along with orthogonal mechanical rotation to distribute surface flux over large area. In this study, this was investigated as a potential solution to fast-falloff limitations expected with kV radiotherapy. This was done with the aim of future clinical development of a lower cost radiotherapy alternative to megavoltage (MV) linac systems. Radiochromic film was employed for dosimetry on the kV X-ray source of the linear-converging radiotherapy system (LCRS). The source utilizes charge particle optics to magnetically deflect and focus an electron beam along a stationary, reflection tungsten target in an ultra-high-vacuum stainless-steel chamber. Resulting X-rays were collimated into converging beamlets that span a large planar angle and converge at the system isocenter. In this study, radiochromic film dosimetry was done at 140 and 145 kVp for a designated planning treatment volume (PTV) of 4 cm diameter. An acrylic phantom was employed for dose distribution measurements of stationary and rotational delivery. Film dosimetry was evaluated in planes parallel to the source X-ray window at various depths, as well as in the plane of gantry rotation. At 140 and 145 kVp and using a collimated 4 cm square field at depth, lesion-to-skin dose ratio was shown to improve with additional beams from different relative source positions, where the different beams are focused at the same isocenter and do not overlap at the phantom surface. It was only possible to achieve a 1:1 Dmax -to-surface ratio with four delivery beams, but the ratio improved to 4:1 with 12 beams, focused at the same isocenter depth of 7.8cm in an acrylic phantom. For the tests conducted, the following Dmax -to-surface ratios were obtained: 0.4:1 lesion-to-skin ratio for stationary delivery from one entry beam, 0.71:1 lesion-to-skin ratio was obtained for two beams, 1.07:1 ratio for four beams, and 4:1 for 12 beams. Dose-depth profiles were evaluated for stationary and rotational dosimetry. Additionally, rotational dosimetry was measured for a case more analogous to a clinical scenario, where the isocenter was located at an off-center simulated lesion. The results demonstrate potential dose-depth improvements with kV arc therapy by distributing the surface flux with a wide converging beam along with perpendicular mechanical source rotation of the LCRS. The system delivered tolerable dose to a large surface area when a threshold of multiple, separated beams was reached. The radiochromic film data support the feasibility of the construct of the LCRS kV radiotherapy system design.

Computing light pollution indicators for environmental assessment

AbstractLight pollution modeling and monitoring has traditionally used zenith sky brightness as its main indicator. Several other indicators (e.g., average sky radiance, horizontal irradiance, and average sky radiance at given interval of zenith distances) may be more useful, both for general and specific purposes of ecology studies, night sky, and environmental monitoring. These indicators can be calculated after the whole sky radiance is known with sufficient angular detail. This means, for each site, to integrate the contribution in each direction of the sky of each light source in the radius of hundreds of km. This approach is extremely high time‐consuming if the mapping is desired for a large territory. Here, we present a way to obtain maps of large territories for a large subset of useful indicators, bypassing the need to calculate first the radiance map of the whole sky in each site to obtain from it the desired indicator in that site. For each indicator, a point spread function (PSF) is calculated from the whole sky radiance maps generated by a single source at sufficiently dense number of distances from the observing site. If the PSF is transversally shift‐invariant, that is, if it depends only on the relative position of source and observer, then we can further speed up the map calculation via the use of fast Fourier‐transform. We present here examples of maps for different indicators. Precise results can be calculated for any single site, taking into account the site and light sources' altitudes, by means of specific inhomogeneous (spatially variant) and anisotropic (nonrotationally symmetric) PSFs.Key points Light pollution is not anymore viewed as an astronomycentric issue. On the contrary, it is a multidisciplinary problem, involving, between others, physicists, ecologists, physiologists, engineers, politicians. Some of the disciplines that will directly take advantage from the methods explained here are: astronomy, ecology and ethology (in condition of altered night light), urban and landscape planning, environmental protection.

Room Acoustical Parameter Estimation From Room Impulse Responses Using Deep Neural Networks

We describe a new method to estimate the geometry of a room and reflection coefficients given room impulse responses. The method utilizes convolutional neural networks to estimate the room geometry and multilayer perceptrons to estimate the reflection coefficients. The mean square error is used as the loss function. In contrast to existing methods, we do not require the knowledge of the relative positions of sources and receivers in the room. The method can be used with only a single RIR between one source and one receiver. For simulated environments, the proposed estimation method can achieve an average of 0.04 m accuracy for each dimension in room geometry estimation and 0.09 accuracy in reflection coefficients. For real-world environments, the room geometry estimation method achieves an accuracy of an average of 0.065 m for each dimension.

Uniform high-reflectivity silver film deposited by planar magnetron sputtering

Abstract Following the development of various complex optical elements, especially those involving aluminum alloys with several free-form surfaces, it is critical to understand the material coating methods. This report provides guidance for coating aluminum alloy optical elements containing four free-form surfaces with reflective silver films. To determine a proper film deposition thickness with high reflectivity applied by magnetron sputtering, a model is proposed to explain how the reflectivity is affected by the thickness of the silver film on the aluminum alloy substrates. Additionally, to optimize the uniformity of film thickness deposited from a magnetron source, a more accurate distribution model was developed by introducing gas pressure parameters. This modified model provides excellent agreement between simulated and experimental results. Finally, the film thickness distribution on the optical element integrated with four free-form surfaces is simulated using the modified model, and the influence of the relative position of sources and substrates on the film thickness uniformity is explored.

Time-Resolved NIROT 'Pioneer' System for Imaging Oxygenation of the Preterm Brain: Preliminary Results.

In preterm infants, there is a risk of long-term cognitive, motor and behavioral impairments due to hemorrhagic and/or ischemic lesions. If detected early, lesions can be prevented. A bedside imaging modality, capable of early detection of both disorders, is necessary. We present the state of development of a tomographic imager (named Pioneer), that will be capable of determining the oxygenation of the preterm-infant brain with high spatial resolution. Pioneer is a time-resolved near-infrared optical tomography (TR NIROT) instrument. It employs multiple wavelength laser light in short pulses on 11 distinct locations and measures the re-emerging light in a contactless fashion by means of a time-correlated single-photon counting (TCSPC) camera (named Piccolo) covering ~4.9 cm2 with 300 detectors. Timing response of the entire system is 116 ps. An in-house designed biocompatible source ring ensures fixed relative positions of sources and detectors and provides a secure interface between the patient and the probe. At the present state, the NIROT Pioneer system successfully detected a 6x6x50 mm3 inclusion 3 cm deep inside a phantom. These results confirm that the Pioneer imager is working as expected and is on a solid path towards full 3D tissue oxygenation imaging.

DABFS: A robust routing protocol for warning messages dissemination in VANETs

Vehicular ad hoc networks play a pivotal role in the enrichment of transportation systems by making them intelligent and capable of avoiding road accidents. For transmission of warning messages, direction-based Greedy protocols select the next hop based on the current location of relay nodes toward the destination node, which is an efficient approach for uni-directional traffic. However, such protocols experience performance degradation by neglecting the movement directions of nodes in bi-directional traffic where topological changes occur dynamically. This paper pioneers the use of movement direction and relative positions of source and destination nodes to cater to the dynamic nature of bi-directional highway environments for efficient and robust routing of warning messages. A novel routing protocol, namely, Direction Aware Best Forwarder Selection (DABFS), is presented in this paper. DABFS takes into account directions and relative positions of nodes, besides the distance parameter, to determine a node’s movement direction using Hamming distance and forwards warning messages through neighbor and best route discovery. Analytical and simulation results demonstrate that DABFS offers improved throughput and reduced packet loss rate and end-to-end delay, as compared with eminent routing protocols.

Convective correction of metafluid devices based on Taylor transformation

The paper presents a method to modify the mechanical properties of a statically–designed metamaterial device in order to preserve its performance when operating in a non–uniform aerodynamic flow. The objective of the research is to contribute to the disclosure of the acoustic metamaterial potential in aeroacoustic applications, where acoustic propagation and scattering are deeply affected by aerodynamic convection. The emphasis is on aeronautical applications aiming at the development of methods for the design of breakthrough solutions for aircraft noise mitigation. The present approach is based on the application of the inverse Taylor transformation to the static design space in order to obtain the properties of an equivalent metamaterial in the convected space. The metamaterial so–obtained is capable to guarantee the target acoustic response in presence of a non–uniform background flow at low Mach number and with negligible vorticity. Numerical results obtained through finite–element simulations are presented for a free stream Mach number ≤0.35, which is compatible with the take–off and landing operation of a commercial airplane. The benchmark used is the widely assessed problem of the scattering cancellation (cloaking) of a circular obstacle. The acoustic disturbance is here assumed to be generated by an isotropic point source located in the vicinity of the scatterer and co–moving with it. The numerical results reveal that the effect of the proposed correction strongly depends on the relative position of the source and the metamaterial device, with the worst performance obtained when they are aligned with the free stream. The reason of this dependence is analytically explained and verified numerically. When the alignment of the source and the treated object is orthogonal to the flow, the Taylor–corrected metamaterial recovers almost completely its expected behaviour. This result makes the approach appealing for all those engineering applications where the relative position of sources and moving boundaries is fixed and compatible with the most favourable conditions.

Real-time localization and tracking of musical instruments with spherical microphone arrays

This research describes a method for dynamic beamforming with a particle filter to localize and track musical instruments in a real-time context. Using a spherical harmonic framework, spherical microphone arrays are able to decompose three-dimensional sound fields into their basic components, which enables detailed analysis and efficient spatial filtering algorithms. In recent years, methods for determining relative source positions around an array using steerable beams have been studied. By creating multiple weighting functions based on spherical harmonic components, many beams can be generated simultaneously and can be used to dynamically track instruments via an iterative process.

A method for real-time, multiple-source localization using spherical harmonic decomposition

By taking advantage of the spherical harmonic transform, spherical microphone arrays are able to decompose three-dimensional sound fields into their basic components, which enables detailed analysis and efficient spatial filtering algorithms. In recent years, methods for determining relative source positions around an array have been studied. Weighting functions can be generated to create a steerable beam which attenuates a sound field except in a specific direction. This research describes a real-time framework for multiple-source detection, which can be implemented using these methods. By finding the energy-sum distribution across a matrix of weighted harmonic signals, directional information may be simultaneously and efficiently obtained for multiple sources over time.

Understanding the acoustics of Papal Basilicas in Rome by means of a coupled-volumes approach

The paper investigates the acoustics of the four World-famous Papal Basilicas in Rome, namely Saint Peter׳s, St. John Lateran׳s, St. Paul׳s outside the Walls, and Saint Mary׳s Major. They are characterized by different dimensions, materials, and architectural features, as well as by a certain number of similarities. In addition, their complexity determines significant variation in their acoustics depending on the relative position of source and receivers. A detailed set of acoustic measurements was carried out in each church, using both spatial (B-format) and binaural microphones, and determining the standard ISO 3382 descriptors. The results are analyzed in relation to the architectural features, pointing out the differences observed in terms of listening experience. Finally, in order to explain some of the results found in energy-based parameters, the churches were analyzed as a system of acoustically coupled volumes. The latter explained most of the anomalies observed in the distribution of acoustic parameters, while showing at the same time that secondary spaces (aisles, chapels) play a different role depending on the amount of sound absorption located in the main nave.

At-sea experiment of adaptive time-reversal multiuser communication in the deep ocean

An at-sea experiment of multiuser communication in deep water using adaptive time reversal was carried out. In the experiment, two sources and a 20-channel receiver array were deployed at the range of 30 km in an area of 1500–2000 m water depth. One of the sources was moored and the other was suspended at various depths. For processing signals actually transmitted from two sources, it was demonstrated that adaptive time reversal could cancel multiuser interference independently of relative source positions. Additionally, for a more detailed investigation, the analysis of multiuser test signals by synthesizing signals from different depths was performed. As a result, especially in the case of adjacent sources, adaptive time reversal significantly suppressed crosstalk.

Uncertainty of Apollo deep moonquake locations and implications for future network designs

We determine location clouds for deep moonquakes by an adaptive grid search method, where each grid point inside the location cloud represents a possible solution of the location problem. We show that four distinct types of cloud shapes exist (i.e., ball, banana, cone, bowl), that their occurrence corresponds to the relative positions of source and receivers, and that the spatial distribution of these shapes provides a measure of the attenuation of elastic waves inside the Moon. Hence they provide an estimate of the location capability of the Apollo network and sparse network designs in general. Furthermore we develop a computationally cheap tool to analyze the location capability for future lunar seismic networks.

Cosmic magnetic lenses

Magnetic fields play a critical role in the propagation of charged cosmic rays. Particular field configurations supported by different astrophysical objects may be observable in cosmic ray maps. We consider a simple configuration, a constant azimuthal field in a disk-like object, that we identify as a cosmic magnetic lens. Such configuration is typical in most spiral galaxies, and we assume that it can also appear at smaller or larger scales. We show that the magnetic lens deflects cosmic rays in a regular geometrical pattern, very much like a gravitational lens deflects light but with some interesting differences. In particular, the lens acts effectively only in a definite region of the cosmic-ray spectrum, and it can be convergent or divergent depending on the (clockwise or counterclockwise) direction of the magnetic field and the (positive or negative) electric charge of the cosmic ray. We find that the image of a point-like monochromatic source may be one, two or four points depending on the relative position of source, observer and center of the lens. For a perfect alignment and a lens in the orthogonal plane the image becomes a ring. We also show that the presence of a lens could introduce low-scale fluctuations and matter-antimatter asymmetries in the fluxes from distant sources. The concept of cosmic magnetic lens that we introduce here may be useful in the interpretation of possible patterns observed in the cosmic ray flux at different energies.

Sensitivity of stable isotope mixing models to variation in isotopic ratios: evaluating consequences of lipid extraction

Summary 1. Stable isotopes of carbon and nitrogen are increasingly used in studies of animal diet reconstruction via mixing models. However, isotope ratios of both consumer and source tissues can be altered by various amounts of lipids, potentially leading to biased estimates of diet composition when they are not taken into account. 2. We investigated the consequences of lipid correction on the estimation of diet composition with mixing models. Using empirical data from three northern terrestrial trophic systems, we illustrated the direct effects of lipid extraction (LE) on the δ13C and δ15N of source and consumer tissues and its ultimate effects on the reconstruction of the consumer’s diet. 3. In parallel, we developed a simulation tool in R, called fatsim, to assess sensitivity of mixing models to variation in isotopic ratios of samples from source or consumer tissues. This tool can be used to assess the effect of shifts in isotopic ratios caused by LE, or other sources of variation, in any trophic system and thus aid in decision making regarding lipid removal. 4. Using fatsim, we showed that the potential effects of LE on estimates of diet composition cannot be predicted without simulations, even in relatively simple systems. The sensitivity of a mixing model isotopic shift depends on the complexity of the system (number of sources) and on the relative positions of sources and consumers within the isotopic mixing space. 5. Our study confirms that the presence of lipids in tissues can bias the interpretation of diet reconstruction results. In a given trophic system, testing the sensitivity of a mixing model to LE can help decide whether lipid removal is required in order to avoid this bias.

Absolute kinematics of radio source components in the complete S5 polar cap sample

We report on the first wide-field, high-precision astrometric analysis of the 13 extragalactic radio sources of the complete S5 polar cap sample at 15.4 GHz. We describe new algorithms developed to enable the use of differenced phase delays in wide-field astrometric observations and discuss the impact of using differenced phase delays on the precision of the wide-field astrometric analysis. From this global fit, we obtained estimates of the relative source positions with precisions ranging from 14 to 200 μas at 15.4 GHz, depending on the angular separation of the sources (from ~1.6 to ~20.8 degrees). These precisions are ~10 times higher than the achievable precisions using the phase-reference mapping technique.

Removal of contaminants released from room surfaces by displacement and mixing ventilation: modeling and validation

This paper presents the experimental and numerical modeling of contaminant dispersion in a full-scale environmental chamber with different room air distribution systems. For the experimental modeling, an area source with uniform emissions of a hypothetical contaminant (SF6) from the entire floor surface is designed and constructed. Two different types of ventilation are studied: displacement and mixing ventilation. A computer model for predicting the contaminant dispersion in indoor spaces was validated with experimental data. The validated model is used to study the effects of airflow and the area-source location on contaminant dispersion. Results show that the global airflow pattern has a strong impact on the distribution of the contaminants. In general, the personal exposure could be estimated by analyzing the relative source positions in the airflow pattern. Accordingly, the location of an exhaust diffuser may not greatly affect the airflow pattern, but can significantly affect the exposure level in the room. When designing ventilation in addition to bringing fresh air to occupants, it is important to consider the removal of contaminants released in the off-gassing of building materials. Typical indoor off-gassing examples are emissions of volatile organic compounds from building enclosure surfaces such as flooring and painted walls. In this study, we conducted experimental and numerical modeling of different area sources in a mock-up office setup, with displacement or mixing ventilation. Displacement ventilation was as successful as mixing ventilation in removing the contaminant source from the floor area. Actually, the most important consideration in the removal of these contaminants is the relative position of the area source to the main airflow pattern and the occupied zone.

Luminosity variation in (de) focusing microlensing

The luminosity variation of a stellar source due to the gravitational microlensing effect can be considered also if the light rays are defocused (instead of focused) toward the observer. In this case, we should detect a gap instead of a peak in the light curve of the source. Actually, we describe how the phenomenon depends on the relative position of source and lens with respect to the observer: if the lens is between, we have focusing, if the lens is behind, we have defocusing. It is shown that the number of events with predicted gaps is equal to the number of events with peaks in the light curves.

Gravitational Lensing of Millisecond Pulsars

AbstractGravitational lensing can significantly magnify the images of astrophysical sources, but only if the source lies within the Einstein ring of the lens. In consequence the chance of any Galactic star magnifying a more distant source is extremely small—much less than one in a million. However, the extra light travel time (‘Shapiro delay’) introduced by the presence of a lens can be large even when there is negligible effect on the image magnification, and as the relative positions of source and lens change so does the delay. In this paper we quantify these changes and the corresponding influence on apparent timing properties of pulsars. While the total Shapiro delay can be large, it is the temporal variations in this quantity which are measurable with pulsar timing. We find that the magnitude of the expected delay variations is too small to be detectable except during strong lensing events, which are extremely rare. Even in the case of a high-velocity pulsar in the Galactic Plane, the stochastic Shapiro delay is typically expected not to have a substantial influence on the timing properties. In consequence the viability of a pulsar-based time standard is not adversely affected by gravitational lensing.

Atomic position recovery by iterative optimization of reconstructed intensities: Overcoming limitations of holographic crystallography.

We propose a rapid new iterative scheme for accurately reconstructing the relative positions of source and scatterers directly from the data of a monoenergetic point-source diffraction pattern. It takes account of the squared object-wave terms neglected in traditional holographic algorithms, does not suffer from a twin-image problem, and even identifies the chemical species of the scattering atoms.