Coherent Angle Research Articles

Coherent angle estimation in bistatic multi‐input multi‐output radar using parallel profile with linear dependencies decomposition

This study investigates the topic of coherent angle estimation in bistatic multi-input multi-output (MIMO) radar, and derives a scheme for coherent angle estimation by exploiting a parallel profile with linear dependencies (PARALIND) decomposition. The receive data can be mapped to a PARALIND model, after which the estimations of transmit/receive directional matrices and the correlated matrix of the sources are all obtained through PARALIND decomposition. Finally, the estimates of direction of departures and direction of arrivals can be obtained by least-square principle. In contrast to the forward–backward spatial smoothing-propagator (FBSS) method and FBSS-estimation method of signal parameters via rotational invariance techniques algorithms, the proposed method not only reaches paired estimates of the angles automatically but also has much better performance for angle estimation. On the other hand, our algorithm can be used for angle estimation in non-uniform linear transmit/receive array. Simulations present the effectiveness of our approach.

Transitivity analysis: A framework for the study of social values in the context of points of view

Since its inception, psychology has struggled with issues of conceptualization and operationalization of social-psychological phenomena. The study of social values and points of view has been prone to such difficulties, despite a predominant concern of qualitative distinctions in the variability of both of these phenomena across different individuals and social groups. And while interest in both traces a common origin in Rokeach's studies of narrow mindedness, the study of both phenomena has since proceeded apace. In this study, we posit a renewed reconciliation between the two that is best served through a social-psychological model of points of view in terms of the values that inspire them. We draw on critical linguistics to propose a theoretical and methodological framework that can aid a systematic study of value structures as they take different forms and meanings through particular types of points of view. In five stages of qualitative analysis, the model deconstructs utterances into distinct terms that reveal a predominant perspective-taking style that can be utilized towards the categorization of different points of view, in terms of values that imbue them and that serve to provide them with a coherent angle of constructing a particular narrative.

A RD-ESPRIT algorithm for coherent DOA estimation in monostatic MIMO radar using a single pulse

This paper discusses the problem of coherent direction of arrival (DOA) estimation in a monostatic multi-input multi-output (MIMO) radar using a single pulse, and proposes a reduced dimension (RD)-estimation of signal parameters via rotational invariance techniques (ESPRIT) algorithm. We reconstruct the received data and then utilise it to construct a set of Toeplitz matrices. After that, we use RD-ESPRIT to obtain the DOAs of the sources. The proposed algorithm is effective for coherent angle estimation based on a single pulse, and it has much better angle estimation performance than the forward backward spatial smoothing (FBSS)-ESPRIT algorithm and the ESPRIT-like of Li, as well as very close angle estimation performance to the ESPRIT-like of Han. For complexity comparison, our algorithm has very close complexity to the FBSS-ESPRIT algorithm, and lower complexity than the ESPRIT-like of Han and the ESPRIT-like of Li. Simulation results present the effectiveness and improvement of our approach.

EIGER characterization results

Characterization and performance measurements have been done on several EIGER detector systems, produced with chips coming from two different lots, both with a lab X-ray source and at the Swiss Light Source (SLS). Results on the detector calibration, electronic noise, threshold dispersion, minimum achievable energy threshold, maximum detectable incoming photon flux and maximum frame rate are presented.An EIGER module is constructed from a ∼4×8cm2 monolithic silicon sensor bump-bonded to 2 ×4 readout chips and contains 0.5Mpixel. The first EIGER 500K systems have been produced and images taken with these detectors are shown.Modules can be tiled together to form large area detectors; both a 9Mpixel and a 16Mpixel systems are at present under development for the coherent small angle X-ray scattering and protein crystallography beamlines of the SLS.

A PARALIND Decomposition-Based Coherent Two-Dimensional Direction of Arrival Estimation Algorithm for Acoustic Vector-Sensor Arrays

In this paper, we combine the acoustic vector-sensor array parameter estimation problem with the parallel profiles with linear dependencies (PARALIND) model, which was originally applied to biology and chemistry. Exploiting the PARALIND decomposition approach, we propose a blind coherent two-dimensional direction of arrival (2D-DOA) estimation algorithm for arbitrarily spaced acoustic vector-sensor arrays subject to unknown locations. The proposed algorithm works well to achieve automatically paired azimuth and elevation angles for coherent and incoherent angle estimation of acoustic vector-sensor arrays, as well as the paired correlated matrix of the sources. Our algorithm, in contrast with conventional coherent angle estimation algorithms such as the forward backward spatial smoothing (FBSS) estimation of signal parameters via rotational invariance technique (ESPRIT) algorithm, not only has much better angle estimation performance, even for closely-spaced sources, but is also available for arbitrary arrays. Simulation results verify the effectiveness of our algorithm.

Coherent angle estimation based on Hankel matrix construction in bistatic MIMO radar

In this article, a novel coherent angle estimation method is proposed for bistatic multiple-input multiple-output radar. First, a decorrelation operation is taken by constructing a Hankel block matrix whose rank equals the number of coherent targets and is independent of the coherency between these targets. Therefore, the signal and noise subspaces of the Hankel block matrix can be estimated properly. Then, in conjunction with the ESPRIT algorithm, the shift invariance properties of the transmit and receive arrays are exploited to estimate the angles of coherent targets with automatic pairing. The numerical simulations demonstrate its validity.

Resolution Calculation and Analysis in Bistatic SAR With Geostationary Illuminator

Bistatic synthetic aperture radar with geostationary illuminator (GeoBiSAR) has its own characteristics in terms of geometrical configuration. In this letter, we treat the Earth's surface as an ellipsoid surface and consider the case of large coherent integration angle and then combine them with the existing methods to determine three key elements describing 2-D resolution for GeoBiSAR and give the generalized resolution calculation formulas for GeoBiSAR. Simulation results verify the validity of the resolution calculation formulas and the related conclusions.

Making sense by measuring arcs: a teaching experiment in angle measure

I discuss a teaching experiment that sought to characterize precalculus students’ angle measure understandings. The study’s findings indicate that the students initially conceived angle measures in terms of geometric objects. As the study progressed, the students formed more robust understandings of degree and radian measures by constructing an arc length image of angle measures; the students’ quantification of angle measure entailed measuring arcs and conceiving multiplicative relationships between a subtended arc, a circle’s circumference, and a circle’s radius. The students leveraged these quantitative relationships to transition between units with a fixed magnitude (e.g., an arc length’s measure in feet) and various angle measure units, while maintaining invariant meanings for angle measures in different units. These results suggest that quantifying angle measure, regardless of unit, through processes that involve measuring arc lengths can support coherent angle measure understandings.

Mechanism and dynamics of block copolymer directed assembly with density multiplication on chemically patterned surfaces

In this work, we used scanning electron microscopy (SEM), in situ coherent small angle x-ray scattering (SAXS), and Monte Carlo molecular simulation to gain insights into the dynamics of block copolymer directed assembly with density multiplication on chemically patterned surfaces. During directed assembly, it was observed with SEM that poly(styrene-block-methyl methacrylate) initially formed discrete polystyrene domains that lacked long-range order at the free surface. After further annealing, the polystyrene domains gradually coalesced into linear domains that were not registered fully with the underlying chemical pattern. The linear domains could be trapped in metastable morphologies. Finally, the linear polystyrene domains formed perpendicular lamellae in full registration with the underlying chemical pattern. It was revealed with SAXS that scattering peaks characteristic of the period of the chemical pattern appeared and disappeared at the early stages of assembly. Finally, the morphological evolution of directed assembly of block copolymer on chemically patterned surfaces was modeled by molecular simulations.

Structure and dynamics of glassy charged colloids studied with coherent small angle X-ray scattering

Coherent small angle X-ray scattering methods have been used to investigate the structure and dynamics of charged colloidal systems with different volume concentration. The static structure factor indicates that the degree of ordering depends on both the electrostatic interactions and the volume fraction. All systems showed a compressed exponential form of the dynamic structure factor. The Q-dependence of the relaxation time τ hints towards ballistic motion of the colloidal particles in the glassy state. For the sample with the highest volume fraction we observe an influence of the static structure factor on the relaxation rate of the particles indicating a caging effect also for the ballistic type of motion.

Correction of higher order geometrical aberration by triple 3-fold astigmatism field

A new concept of a spherical aberration correction system using three dodecapoles is proposed. The system compensates for higher order aberration of 6-fold astigmatism, which generally limits a uniform phase area for image forming and probe forming in an electron microscope with a conventional two-hexapole corrector. Triple 3-fold astigmatism field is used to correct the spherical aberration of the objective lens, and the total 3-fold astigmatism is eliminated by their combination. The optimum azimuth relationship among three dodecapoles is calculated to eliminate the 6-fold astigmatism. The principle of the method was verified using a mathematically complex representation. This new concept was experimentally tested with a scanning transmission electron microscope at 60 kV acceleration. The 6-fold astigmatism was certainly compensated and the coherent convergent angle became almost twice compared to a conventional double hexapole system.

Energetic particle parallel diffusion in a cascading wave turbulence in the foreshock region

Abstract. We study parallel (field-aligned) diffusion of energetic particles in the upstream of the bow shock with test particle simulations. We assume parallel shock geometry of the bow shock, and that MHD wave turbulence convected by the solar wind toward the shock is purely transverse in one-dimensional system with a constant background magnetic field. We use three turbulence models: a homogeneous turbulence, a regular cascade from a large scale to smaller scales, and an inverse cascade from a small scale to larger scales. For the homogeneous model the particle motions along the average field are Brownian motions due to random and isotropic scattering across 90 degree pitch angle. On the other hand, for the two cascade models particle motion is non-Brownian due to coherent and anisotropic pitch angle scattering for finite time scale. The mean free path λ|| calculated by the ensemble average of these particle motions exhibits dependence on the distance from the shock. It also depends on the parameters such as the thermal velocity of the particles, solar wind flow velocity, and a wave turbulence model. For the inverse cascade model, the dependence of λ|| at the shock on the thermal energy is consistent with the hybrid simulation done by Giacalone (2004), but the spatial dependence of λ|| is inconsistent with it.

Remote Sensing of the Coastal Zone of Tropical Lakes Using Synthetic Aperture Radar and Optical Data

The coastal zone of Lake Malawi contains the greatest diversity of freshwater ichthyofauna in the world. The distribution of habitats along the coast has played an important role in the speciation of fishes but has not been mapped using remote sensing due to cloud cover. The discrimination of rock, sand, and vegetated coasts of tropical Lake Malawi are investigated using synthetic aperture radar (SAR) and optical remote sensing data. The effects of coherent fading, look direction, and incident angle on SAR backscatter are investigated using eight fine-beam RADARSAT SGX images covering 31 km of coast. Adaptive filter trials demonstrate pixels with relatively low backscatter values are identified as image noise most frequently. For each class most of the SAR backscatter averages derived from high and low incident angles within each look direction are similar or within sensor calibration limits. Average rock, sand, and vegetated image tones derived from shoreline segments 150 m in length are statistically separable. Linear discriminant Analyses (LDA) of the RADARSAT and SPOT data are used to attain maximal separation for 33% of rock, sand, and vegetated coastal data and to predict class membership for the 67% of coast for which class membership is known. The RADARSAT and SPOT are treated independently and then combined to use the complementary information available in multi-sensor data sets. LDA of a single extra fine beam RADARSAT image can separate rock, sand, and vegetation using SAR backscatter, coastal slope, and the angle of the shoreline relative to the satellite. Overall classification agreement is 98.5%. LDA of the four multispectral SPOT bands provided classification agreement of 79.3%. Coastal class discrimination is improved with the addition of one or more SAR images to the SPOT data. Classification is not improved above 98.9% when more than one SAR image is added to the data from SPOT. SAR data can be used to map rock, sand, and vegetated coastal zones in areas of persistent cloud cover.

Refraction and scattering into a sandy ocean sediment in the 30-40-kHz band

To observe sound penetration into a sandy sediment, a buried acoustic receiving array was insonified by a wide band sound source carried by a remotely operated vehicle. A slanting array design was used to avoid scattering artifacts. This design overcame possible problems in previous experiments, in which scattering artifacts from the array structure could be mistaken for a propagating wave. The experiments took place in a sandy sediment off the West coast of Florida, as part of the sediment acoustics experiment, which is a multidisciplinary effort to study sediment acoustics. A coherent angle, speed, and height estimation process searched through a four-dimensional search space, of source height and elevation angle, wave speed, and propagation delay to find spherical acoustic wave fronts. Three main categories of waves were found: first refracted, dominant nonrefracted and evanescent. Later acoustic arrivals, a fourth category, remain to be analyzed. Their relative intensities effectively characterize the sediment penetrating acoustic energy. The acoustic sound pressure level of penetrating waves below the critical grazing angle was found to be greater than expected for a flat interface.

Aging in a filled polymer: Coherent small angle x-ray and light scattering

Measurements are described using small angle coherent x-ray scattering and small angle dynamic light scattering of motion in fumed silica aggregates suspended in a poly(dimethyl siloxane) melt. At rest, this system develops weakly bound superstructures that are disrupted by mechanical stirring or thermal treatment. The observed relaxation rates correspond to a combination of liquidlike diffusion and a structural relaxation (flocculation) whereby the diffusing silica aggregates recombine into larger agglomerates at long times. Both processes are diffusion controlled. Two samples are investigated. The first, in which the silica is hydrophilic, is a highly viscous liquid for which the respective rate coefficients are about 5x10(-14) cm(2) s(-1) and 2x10(-15) cm(2) s(-1). The second sample, in which the silica surface is hydrophobic, is a thixotropic paste. The same aging mechanism in the diffusion is also observed, but with much slower rate constants, 2x10(-15) cm(2) s(-1) and 9x10(-16) cm(2) s(-1), respectively.

Small angle neutron scattering, total cross-sections and mass density measurements of concentrated NaCl and KCl solutions in H 2O or D 2O

The mass densities, total cold neutron cross sections and small angle scattering of concentrated NaCl and KCl solutions in H 2O or D 2O ( 2H 2O) were measured at 20°C. The partial specific volumes of both salts increase with salt concentration and are significantly smaller in D 2O than in H 2O, showing that these salt solutions cannot be considered as isomorphous in H 2O and D 2O. As salt concentration increases for both salts, the total coherent cross sections for neutrons of the solutions also increase while the coherent small angle scattering decreases—observations that are consistent, respectively, with increasing correlations involving the ion and water components and a decrease in the particle number density and/or concentration fluctuations, in the solutions. Changes in incoherent scattering with salt concentration are essentially those expected from the solution compositions and densities.

High resolution cross-sectional transmission electron microscopy of thermal oxide films on copper

The structure of thermal oxide films on copper has been investigated by transmission electron microscopy of ultramicrotomed sections. Sections of the copper substrate and its oxide film less than 10 nm thick and suitable for high resolution examinations were prepared with negligible damage to the oxide film and the oxide/metal interface. Such examination revealed the mosaic structure of the oxide and the oxide/metal interface with atomic resolution. Further, oxidation rate differences between individual metal grains and the extents of paths for easy diffusion are revealed. For metal grains of low oxidation rate, the platelet oxide structure suggests that coherent or low angle boundaries separating crystallites do not act as paths for easy diffusion. Conversely, where fine spherical oxide particles are present, incoherent boundaries between particles offer many potential sites for easy transport.

Characterization of urea optical parametric oscillators pumped by excimer lasers

An optical parametric oscillator (OPO), based on urea crystals of length up to 25 mm as the nonlinear medium and pumped by a line-narrowed injection-seeded pulsed XeCl excimer laser, is described. We report peak conversion efficiency at 90° phase matching of 65% and efficient generation of coherent visible radiation angle tunable from 537 to 720 nm. Requirements on OPO pump laser linewidth and beam divergence are considered. Variation of OPO threshold energy fluence as a function of various oscillator parameters has been investigated experimentally and compared with theoretically modeled predictions. Pumping of a urea OPO at 249 nm by a krypton fluoride excimer is reported for the first time to our knowledge.

Status of angular units

Angles should be considered as relative, i.e., dimensionless derived quantities. It is only by accepting the condition that angles are dimensionless that it is possible to maintain the generally accepted system of equations relating angles to other quantities, the accepted form of transcendental-function expansions in powers of angles, etc., as well as the normal system of dimensions. The angle units are relative, i.e., they belong to the category of derived units and, therefore, the coherent angle units, the radian and steradian, must be included in the category of derived SI units. The question of referring the angle units to the category of derived SI units should be proposed for discussion by the Consulting Committee on Units and an appropriate draft resolution should be presented to the forthcoming General Conference on Weight and Measures.

Kohärente Kleinwinkelstreuung hochenergetischer Pi-Mesonen an leichten Kernen ( 3He und 4 He)

Abstract The paper discusses recently obtained (theoretical) results on the coherent small angle elastic scattering of high energy pions on the nuclei 3 He and 4 He. Starting with the full suitably parametrized spin- and isospindependent pion-nucleon amplitude for pion laboratory energies between 0.826 and 2.01 GeV the Glauber’s plural scattering formula has been applied to derive the angular distribution of scattered pions. A concise report on the use of coherent high energy processes in the investigation of the nuclear structure and the hadron-nucleon scattering amplitude is given. The advantages and shortcomings as well as possible generalizations of the plural scattering model are outlined. The formalism applied to derive results on the structure of 3 He and 4 He and the conclusions drawn from the results on pion-helium scattering are presented in detail. It has been shown that an effective pion nucleon amplitude may safely replace the full amplitude in the present context and in the energy region mentioned above.