Scatter Characteristics Research Articles

Possibilities for separation of scalar and vector characteristics of acoustic scatterer in tomographic polychromatic regime

Abstract The inverse wave problem of tomographic type is considered. It consists in reconstruction of several scatterer’s characteristics in the form of spatial distributions for sound speed, medium density, absorption coefficient and power index of its frequency dependence, as well as vector of flow velocity. In the form of a survey material (based on several publications), a sequence of steps is discussed that leads to reconstruction of each individual spatial distribution in the presence of different combinations of the mentioned characteristics. The minimum number of frequencies required for reconstruction is discussed when the complete set of scattering data is available at each of the frequencies. For the first time, two possible approaches to reconstruct the scatterer characteristics in the presence of inhomogeneous spatial distributions of the density and the flow velocity vector are compared, and attention is drawn to the perspectives of reconstruction by functional algorithms in this case. The possibility of separating the sought spatial distributions during the inverse problem solution is illustrated by numerical modeling.

The Scattering Characteristics of Vortex Radio-Frequency Waves for Wireless Communication

As a solution to the shortage of transmission capacity, the vortex radio frequency waves have been applied to wireless transmission technology. The potential of vortex radio frequency waves applying to the fields of wireless communication, radar detection and radar imaging will be invaluable. The scattering characteristics of the vortex waves are the basis for its application in radar detection imaging and identification. This paper focuses on the theoretical derivation, including the main effects on the scattering characteristics, and the future applications and prospects of scattering characteristics. The state of art in research area is reviewed, followed by a brief discussion on future directions.

A Man-Made Target Extraction Method Based on Scattering Characteristics Using Multiaspect SAR Data

Multiaspect synthetic aperture radar (SAR) can obtain the response of the target to the radar illumination in the angle dimension. The radar cross section data referring to scattering behavior can be obtained by multiaspect SAR. The anisotropy characteristics of the man-made target in the imaging scene can reflect its scattering changing behavior. Meanwhile, the amplitude characteristics of man-made target in some observing angles is target's another scattering property. Based on man-made target's anisotropy characteristics and amplitude characteristics, a dual-channel model (DCM) based on distribution and membership for man-made target extraction is generated in this article. The model considers man-made target's data changing in different observing aspects and strong points in specific aspects. First, the preprocessing of multiaspect data using low-rank matrix decomposition is discussed. Then, the parameters of SAR amplitude images’ distribution function are calculated by using expectation maximization method. Third, one channel is fuzzy C-means (FCM) method combining spatial neighborhood information for amplitude characteristics extraction. Another channel is statistical distribution model for anisotropy characteristics extraction. Finally, The calculated membership degree (MD) and statistical probability describe the man-made target and natural target. C-band circular SAR data is used to validate our method. The result of our DCM is compared with the result of only using a single channel model. The man-made targets are extracted better using the DCM.

Time-Domain Scattering Characteristics and Jamming Effectiveness in Corner Reflectors

The outboard corner reflectors are widely used as a countermeasure to radar tracking and detection. Therefore, it is essential to determine the composite time-domain scattering characteristics of the corner reflector and ship against the sea background and the jamming effectiveness of the corner reflector array. In this paper, the composite electromagnetic scattering characteristics of ship target, corner reflector, and the sea surface are studied based on the time-domain bouncing ray method (TDSBR). The radar echo and broadband radar cross section (RCS) results for the time domain pulse incident are also obtained and the high-resolution range profile (HRRP) is calculated. We then devise an evaluation system based on centroid jamming intensity and range profile similarity to determine the jamming characteristics of passive jamming. We further propose an array composing of three sizes of corner reflectors. Finally, the centroid jamming effectiveness is analyzed by comparing the RCS of the corner reflector array and the ship, and the deception jamming effectiveness is measured by calculating the range profile similarity based on the cosine similarity method and the range profile peak envelope overlap. Simulation results show that the reflector array can achieve a good performance both for centroid and range profile deception. The simulation results given and the evaluation method proposed in this paper provides significant practical insights into the design and analysis of the passive jamming systems.

Radiowave Scattering Characteristics of Melting Layer Measured by a Dual Ka-band Radar System

Radiowave Scattering Characteristics of Melting Layer Measured by a Dual Ka-band Radar System

双颗粒凝聚气溶胶的吸湿增长模型及散射特性

双颗粒凝聚气溶胶的吸湿增长模型及散射特性

Surface Field Distribution and Composite Scattering Characteristics of Three-dimensional Micro-nano Hemispherical Periodic Structure Optical Surface

Surface Field Distribution and Composite Scattering Characteristics of Three-dimensional Micro-nano Hemispherical Periodic Structure Optical Surface

Regulation of Hierarchical Structure on Surface-enhanced Raman Scattering Characteristics of Nanoporous Metals

Regulation of Hierarchical Structure on Surface-enhanced Raman Scattering Characteristics of Nanoporous Metals

A Study of Composite Scattering Characteristics of Movable/Rotatable Targets and a Rough Sea Surface Using an Efficient Numerical Algorithm

The composite electromagnetic scattering characteristics of movable/rotatable targets coexisting with a randomly rough sea surface are studied by the extended propagation-inside-layer expansion (EPILE) combined with the generalized forward-backward method (GFBM). The composite scattering formulation is given. The multiple scattering characteristics related to the self- and mutual coupling of the targets and sea surface under different parameters are numerically implemented and analyzed.

Two dimensional spacial soliton in atomic gases with PT-symmetry potential.

We propose a realistic physical scheme to realize linear Gaussian optical potential with parity-time (PT) symmetry and two dimensional (2D) spacial solitons in a coherent atomic gas. It is shown that the PT-symmetric potential can be created through the spatial modulation of the control and relevant atomic parameters. We find that the Gaussian PT potential parameters, the imaginary part and the width and the position, play crucial roles in the occurrence of the PT phase transition. We demonstrate that the system supports stable 2D dipole solitons and vortex solitons, which can be managed via tuning PT potential. Furthermore, the dynamic characteristics of the symmetric scatter and collision of solitons are shown.

Scattering and Attenuation Characteristics at Volcanoes Inferred From Envelope Widths of Natural and Active Seismic Sources

AbstractSeismic scattering and attenuation at volcanoes, thought to be strongest on the Earth, can be used to map volcanic feeding systems. We systematically analyzed high‐frequency (5–10 Hz) seismograms of volcano‐tectonic earthquakes at Galeras volcano (Colombia) and active sources at Kirishima, Unzen, Bandai, and Iwate volcanoes (Japan) to investigate their scattering and attenuation characteristics. The envelope widths estimated from these seismograms were compared with those calculated by Monte Carlo envelope simulations for 1D layered models parameterized by the scattering mean free path and the quality factor of medium attenuation for S waves. Our results indicated a surficial, highly heterogeneous, and attenuative layer up to around 1 km thickness at all studied volcanoes. The strongest heterogeneities at volcanoes thus exist in a thin surface layer, likely comprising unconsolidated and/or highly fractured materials. Using the space‐weighting function for diffusive wavefields, we mapped the residuals between observed envelope widths and those calculated with our estimated 1D models at Kirishima, Unzen, Bandai, and Iwate. These maps showed spatial distributions of the envelope‐width residuals were unique to each volcano and correlated with P wave velocity tomographic images. Areas of positive residuals correspond to low‐velocity anomalies and thus to heterogeneous, strongly scattering rocks, whereas areas of negative residuals correspond to high‐velocity anomalies and thus less heterogeneous volcanic or basement rocks. Our results demonstrate that envelope widths can improve the characterization of scattering and attenuation structures beneath volcanoes.

The Low-Frequency Acoustic Scattering Characteristics Study on Underwater Elastic Targets by the Coupled FEM-BEM Method

A mathematical model about calculating acoustic scattering of elastic shell with air inside unbounded fluid was developed using a coupled finite element and boundary element technique. The coupling of elastic shell with air and shell with fluid was included in this model. To validate the scheme, the scattering characteristic of spherical shell with air submerged in water was calculated. Comparison of the numerical results with the corresponding analytical solutions shows that they are in good agreement in low frequency. On this basis, the low-frequency acoustic scattering characteristic of underwater elastic target was calculated with this method. The results showed the shell thickness and material have little effect on the target strength in the transverse direction, when the frequency is 100-300 Hz. In the omni-direction, the target strength of titanium alloy shell is higher than that of steel shell, and the larger the shell thickness, the greater the target strength. As the frequency is 200 Hz, the steel shell with a thickness of 28 mm has the phenomenon of acoustic resonance, resulting in a sharp increase in the target strength.

ИССЛЕДОВАНИЕ СОГЛАСОВАННОСТИ ЭКСПЕРТНЫХ ОЦЕНОК ПРИ ЗАВИСИМЫХ ВЫБОРКАХ

The problem of the agreement in experts’ opinions is one of the main ones in making collective decisions. The quality of the collective decision (accuracy, reliability, reliability, number of experts, time and laboriousness of decision making) depends on the degree of consistency of expert decisions. The article discusses the issues of reliability of estimates given by a group of experts for dependent samples. The dependence of random variables in samples is manifested, first of all, in testing systems. The dependence can be between the test questions, as well as between the student’s answers to the test questions on different topics. A connection can also be found between the answers of different trainees with a similar assimilation of the educational material. In the article, to determine the consistency of expert assessments, the indicator is the sum of centered values of random variables corresponding to the assigned estimates. This indicator characterizes the total scatter of expert assessments relative to the arithmetic mean of the collective assessment. In case of complete agreement of opinions, the value of the indicator is zero. The characteristics of the scatter of estimates are derived from the Chebyshev theorem. The lower and upper bounds of the estimation error are obtained. The confidence interval for the correlation coefficient is built. A formula for finding the proportion of possible deviations in the score is derived. The behavior of the boundaries of the confidence interval was investigated for different values of the point estimate. The case is considered when all correlation coefficients are non-negative. A comparison is made of the behavior of the boundaries of the confidence intervals for non-negative correlation coefficients and the general case. The results obtained can be used, for example, in testing systems for personnel training, in product quality control systems, to select promising technologies, and medical diagnostics.

Analyzing the Electromagnetic Scattering Characteristics of a Hypersonic Vehicle Based on the Inhomogeneity Zonal Medium Model

A new electromagnetic (EM) calculation model, the inhomogeneity zonal medium model (IZMM) (based on the physical optics (PO) method), is proposed to calculate and analyze the EM scattering characteristics of hypersonic vehicle covered with a plasma sheath. First, the flow field of the plasma sheath is divided into nonuniform calculation subregions with different spacing sizes. The shape of the external flow field of the aircraft is modeled by fitting with a paraboloid and circular platform with different radii. Then, the electron density, temperature, and pressure distribution are obtained by collecting data from different points in the flow field of the sheath. Finally, a piecewise PO method is used to calculate the backscattering radar cross section (BRCS) of the hypersonic vehicle covered with plasma sheath from L-band to X-band. The numerical results show that the EM scattering characteristics of a target spacecraft covered with a plasma sheath can be described more accurately by using zoned medium model simulation. Under different flying conditions, the BRCS of hypersonic vehicle covered with a plasma sheath appears to be reduced to different degrees in the S-band and the band range of 7-11 GHz, and a large attenuation of BRCS occurs in the head area of the aircraft. The research results enrich the EM modeling method of hypersonic vehicles, overcome some shortcomings of the existing PO method, and provide technical support and innovative ideas for the accurate analysis of the EM scattering characteristics of hypersonic targets.

An effective numerical strategy for retrieving all characteristic parameters of an elastic scatterer from its FFP measurements

A new computational strategy is proposed for determining all elastic scatterer characteristics including the shape, the material properties (Lamé coefficients and density), and the location from the knowledge of far-field pattern (FFP) measurements. The proposed numerical approach is a multi-stage procedure in which a carefully designed regularized iterative method plays a central role. The adopted approach is critical for recognizing that the different nature and scales of the sought-after parameters as well as the frequency regime have different effects on the scattering observability. Identification results for two-dimensional elastic configurations highlight the performance of the designed solution methodology.

Contribution of immunophenotype to the investigation and differential diagnosis of Burkitt lymphoma, double-hit high-grade B-cell lymphoma, and single-hit MYC-rearranged diffuse large B-cell lymphoma.

There are no immunophenotypic guidelines for the investigation of MYC-rearranged lymphomas. We aimed to identify simple immunophenotypic features that would help to differentiate between MYC-rearranged lymphomas and guide cytogenetic analysis. We reviewed diagnostic samples from patients diagnosed with Burkitt lymphoma (BL), double-hit lymphoma (DHL), MYC-rearranged diffuse large B-cell lymphoma (MYC-DLBCL), and standard (non-MYC-rearranged) DLBCL over the last decade in our Institution. Using flow cytometry (with antibodies CD20, CD10, CD38, bcl-2, Ki-67, FMC-7, CD43, CD27, CD79b, CD23, and CD22) we determined antigen% expression and median-fluorescence intensity ratios (MFIR). The forward scatter (FS) and side scatter (SS) characteristics of tumor B-cells were compared with normal T-cells (B/T ratios) for patients with MYC-rearranged lymphomas. We identified 51 patients of whom 14 had BL, 10 had DHL (6 MYC+/BCL2+; 4 MYC+/BCL6+), 8 MYC-DLBCL, and 19 standard DLBCL. The significant differences (p <.05) were: higher CD38% in BL than standard DLBCL; higher CD10% in BL and DHL versus MYC-DLBCL and standard DLBCL; higher CD10MFIR in BL than MYC-DLBCL and standard DLBCL; higher Ki-67% in BL than DHL and MYC-DLBCL; higher bcl-2% in DHL than BL; higher FMC-7% in BL than MYC-DLBCL and standard DLBCL; and lower SS (B/T) ratio in DHL than MYC-DLBCL. The combination of CD38% > 90, CD10% > 80, CD10MFIR > 10, bcl-2% < 30, and Ki-67% > 70 was characteristic of BL. "Deviation" from these cut-offs should raise suspicion for DHL and, therefore, BCL2 and/or BCL6 FISH is required. We also found that a diagnosis of DHL rather than of MYC-DLBCL was significantly associated with CD10% > 60, Ki-67% > 50, and SS (B/T) <1.5.

The Nonlinear Scattering Characteristics of Sound Waves by a Bubble

The scattering characteristics of sound waves by bubbles have been widely applied to ship tracking, wake-homing torpedo and reverberation suppression. To explore the nonlinear scattering characteristics of sound waves by bubbles, the Keller-Miksis equation of bubble vibration was adopted and a numerical solution to the nonlinear equation is presented. Then, the characteristics of nonlinear scattering, including the intensity of the scattered waves, the frequency and radius selection under pulse excitation and the scattered wave duration, are studied. The nonlinear scattered waves by a bubble are too small to be detected when the intensity of the excitation source is small. As the intensity of the excitation source increases, so does that of scattered harmonics by the bubble. If the intensity of the excitation source is further increased to a certain extent, the scattered waves by the bubble occurs dispersion phenomenon, emitting broadband noise. It may be the reason why a broadband noise will be produced by the cavitation of bubbles.

Adaptive optics permits label-free intravital imaging of tissue resident and infiltrating immune cells in the mouse retina

Abstract The eye is ideally suited for unperturbed longitudinal intravital imaging of immune responses. No confounding inflammatory surgery, externalization or depressurization is required for access as it is uniquely transparent. Directly imaging immune cells in vivo would greatly advance our biological understanding but it is not currently possible in man, and only feasible in mice using exogenous fluorescent labeling or transgenic modification which can result in physiologically unrepresentative results. We discover both tissue resident and infiltrating immune cells can be visualized in the retina using a custom adaptive optics scanning light ophthalmoscope (AOSLO) employing phase contrast detection of reflected 796nm light. This is analogous to scatter characteristics observed in flow cytometry, with motile cells visible within the laminated structure of the retina. Anesthetized mice underwent intraocular injection of LPS to induce acute inflammation before repeated imaging at the same anatomical location across intervals from 6 hours to 2 months. Leukocyte rolling within post-capillary venules and tissue infiltration was visible without exogenous contrast. We confirmed 83% of this population were neutrophils by co-localization following tail vein injection of Alexa Fluor-647 anti-Ly6G antibody. Tracking the same location revealed reduced motility (24 vs 6 hours) despite cellular persistence preceding resolution of inflammation. Microglia could be imaged including their highly motile processes, confirmed using healthy eyes from Cx3cr1GFP/+ reporter mice. This is the first report of label-free immune cell imaging within the mouse retina and the approach could feasibly translate to existing human AOSLO platforms.

Determination of Integral Scattering Characteristics

We consider issues related to the determination of integral characteristics of the scattering phase function for media with a highly forward directed scattering function. We show that, as a rule, the standard method of calculation of the average cosine of the scattering angle does not take into account the contribution that is important for scattering in the direction of small angles. We present a technique that makes it possible to obtain necessary corrections for the integral scattering characteristics in this case.

Water equivalence of a solid phantom material for radiation dosimetry applications.

Radiological water equivalence of solid phantoms used for radiotherapy is often desired, but is non-trivial to achieve across the range of therapeutic energies. This study evaluated the water equivalence of a new solid phantom material in beam qualities relevant to radiotherapy applications. In-phantom measured depth distributions were compared to that in water to assess the relative attenuation and scatter characteristics of the material. The phantom material was found to be dosimetrically equivalent to water within (1.0 ± 1.0)% for megavoltage photon beam qualities, (1.5 ± 1.3)% for megavoltage electron beam qualities, (1.5 ± 1.5)% for medium-energy kilovoltage X-rays and (3.0 ± 1.5)% for low-energy kilovoltage X-rays.