Nonlinear Scatter Research Articles

Comparison of Bayesian, k-Nearest Neighbor and Gaussian process regression methods for quantifying uncertainty of suspended sediment concentration prediction

Suspended sediment transport in river system is a complex process influenced by many factors that their interactions lead to nonlinear and high scatter of concentration-discharge relationships. This makes the model prediction subject to high uncertainty and providing one value as the model prediction is somehow useless and cannot provide adequate information about the model accuracy and associated uncertainty. Current study compares the efficiency of Bayesian (i.e. Bayesian segmented linear regression (BSLR) and Bayesian linear model (BLR)), Gaussian Process Regression (GPR) and k-Nearest Neighbor (k-NN) in quantifying uncertainty of the suspended sediment concentration prediction in three watersheds namely Arazkoseh, Oghan and Jajrood located in Iran. Three input combinations including, contemporary discharge, slow and quick flow components and contemporary, one and two antecedent days discharge, were used. The BSLR model was able to identify threshold value, furthermore, pre-threshold and post-threshold slopes of BSLR model indicated that for Arazkoseh watershed channel and for Oghan and Jajrood watersheds, upland area are dominate sediment sources. In all three studied cases, given prediction interval width and the percent of enclosed observed data by prediction interval, k-NN model provided more reliable prediction interval. Moreover, separation stream flow into slow and quick flow components lead to improved performance of GPR and k-NN models in the studied watersheds, and the best results for Arazkoseh and Oghan watersheds were obtained when slow and quick flow components were used as the model input.

Energy Transmission of Vortex Beams Through 3rd Order Intensity Dependent Nonlinear Optical Limiters

Third order optical limiting utilizes nonlinear absorption or scatter to preferentially reduce the optical throughput of intense light through a medium. While these processes are dependent on intensity, it is often the transmitted energy or power that needs to be limited to avoid eye, sensor or detector damage. This is problematic when the input is a vortex mode or other higher order Gaussian distributions such as Bessel-Gaussian modes where the relationship between optical power and the on axis intensity is more complicated than for the TEM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">00</sub> Gaussian mode. Here we show that for higher order Bessel-Gaussian modes that beam power transmission is not equivalent to peak intensity transmission through intensity dependent absorption or scatter based optical limiters. We present a theoretical model and experimental data that demonstrates that the power throughput in these media, increases by 4 and 7 times for n = 1 and 2 Bessel-Gaussian modes, respectively, over that observed when a TEM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">00</sub> mode is used.

Effect of weaving structures on the geometry variations and mechanical properties of 3D LTL woven composites

This paper presents a comprehensive experimental study of the effect of weaving structures on the geometry variations and mechanical properties of three dimensional (3D) layer-to-layer interlock (LTL) woven composites. 3D woven composites with four different weaving structures are prepared. Geometry variations of the unit cell structures are investigated based on the micro-computed tomography (micro-CT) images. Tension and compression tests are performed to the four composites. The digital image correlation (DIC) method is used to obtain surface strain fields of the specimens under tension load. Both tension and compression properties of the composites are affected by the waviness of load-bearing yarns. The addition of stuffer yarns significantly improves the warp direction performance. Nonlinear behavior, failure modes and scatter of testing results for the specimens are closely related to the weaving structures.

A binary water wave optimization for feature selection

A search method that finds a minimal subset of features (over a feature space) that yields maximum classification accuracy is proposed. This method employs rough set theory (RST) along with a newly introduced binary version of the water wave optimization approach (WWO) which is denoted by BWWO. WWO simulates the phenomena of water waves, such as propagation, refraction, and breaking and is one of the newest nature inspired methods for global optimization problems. In our approach, BWWO utilizes the phenomena of water waves propagation, refraction, and breaking in a binary version. Two main experiments based on the rough set approach and wrapper method as a part of the objective function are carried out to verify the performance of the proposed algorithm. In the first experiment, the effectiveness of the proposed approach based on RST is demonstrated on 16 different datasets. The proposed approach is compared with various typical attribute reduction methods and popular optimizers in the literature, such as ant colony, nonlinear great deluge algorithm, scatter search and others. For the second experiment, a feature subset that maximizes the classification accuracy (using cross-validated kNN classifier) with minimizing the number of selected features is obtained over 17 different datasets. In wrapper experiment BWWO is compared with the binary gray wolf optimization, binary particle swarm optimizer, binary cat swarm optimization, binary dragonfly algorithm and the binary bat algorithm. The computational results demonstrate the efficiency and effectiveness of the proposed approach in finding a minimal features subset that maximize the classification accuracy. Furthermore, Friedman test and Wilcoxon's rank-sum test are carried out at 5% significance level in this study.

Enhanced target detection and classification using two-pulse sonar methods

A number of two-pulse sonar techniques can be employed to separate linear and nonlinear scatterers. Twin Inverted Pulse Sonar (TWIPS) and Biased Pulse Summation Sonar (BiaPSS) are processes that exploit nonlinear bubble dynamics to perform such a classification, with clutter reduction. Consequently, these techniques can be used to enhance target detection in bubbly waters. TWIPS and BiaPSS rely upon bubbles being driven to large nonlinear pulsations, but this is dependent upon availability of a high-amplitude source. Previous studies could only access a narrow-band source and therefore used a low frequency so that, over the rarefaction cycle, most ocean bubbles would expand sufficiently (the size range of near-surface ocean bubbles under waves and wakes being large). However, recent access to a broadband high-power source has allowed exploitation of bubble resonances. This talk presents results of investigations using broadband linear sine sweeps, of which one is based upon the simulation of an Atlantic Bottlenose Dolphin (Tursiops truncatus) echolocation click from Capus et al. (2006). Insonifying a cloud of bubbles with a wide band of frequencies excites as many of those sizes at, or close to, their resonance. As such, the contrast between linear and nonlinear scatter is enhanced, improving the target detection capability.

Preparation of graghene oxide/chitosan composite films and investigations on their nonlinear optical limiting effect

As a new kind of carbon nanostructured material, graphene and its derivatives have attracted extensive attention owing to their outstanding optical limiting (OL) properties. However, most of the current studies concentrate on liquid matrix. In this work, we use chitosan (CS) as matrix and homogeneously disperse graphene oxide (GO) into it to prepare GO-CS composite films. We comparatively study the different OL effects and mechanisms of GO in liquid and solid matrix. The results show that GO presents stronger nonlinear optical effect and weaker nonlinear optical scatter, which indicates that different from carbon nanotubes, GO may possess multi sort of nonlinear optical effects.

Existence and properties of ageostrophic modons and coherent tripoles in the two-layer rotating shallow water model on the -plane

AbstractWe study formation and properties of new coherent structures: ageostrophic modons in the two-layer rotating shallow water model. The ageostrophic modons are obtained by ‘ageostrophic adjustment’ of the exact modon solutions of the two-layer quasi-geostrophic equations with the free surface, which are used to initialize the full two-layer shallow water model. Numerical simulations are performed using a well-balanced high-resolution finite volume numerical scheme. For large enough Rossby numbers, the initial configurations undergo ageostrophic adjustment towards asymmetric ageostrophic quasi-stationary coherent dipoles. This process is accompanied by substantial emission of inertia–gravity waves. The resulting dipole is shown to be robust and survives frontal collisions. It contains captured inertia–gravity waves and, for higher Rossby numbers and weak stratification, carries a (baroclinic) hydraulic jump at its axis. For stronger stratifications and high enough Rossby numbers, ‘rider’ coherent structures appear as a result of adjustment, with a monopole in one layer and a dipole in another. Other ageostrophic coherent structures, such as two-layer tripoles and two-layer modons with nonlinear scatter plot, result from the collisions of ageostrophic modons. They are shown to be long-living and robust, and to capture waves.

A new approach to detect congestive heart failure using Teager energy nonlinear scatter plot of R–R interval series

A novel approach to distinguish congestive heart failure (CHF) subjects from healthy subjects is proposed. Heart rate variability (HRV) is impaired in CHF subjects. In this work hypothesizing that capturing moment to moment nonlinear dynamics of HRV will reveal cardiac patterning, we construct the nonlinear scatter plot for Teager energy of R–R interval series. The key feature of Teager energy is that it models the energy of the source that generated the signal rather than the energy of the signal itself. Hence, any deviations in the genesis of HRV, by complex interactions of hemodynamic, electrophysiological, and humoral variables, as well as by the autonomic and central nervous regulations, get manifested in the Teager energy function. Comparison of the Teager energy scatter plot with the second-order difference plot (SODP) for normal and CHF subjects reveals significant differences qualitatively and quantitatively. We introduce the concept of curvilinearity for central tendency measures of the plots and define a radial distance index that reveals the efficacy of the Teager energy scatter plot over SODP in separating CHF subjects from healthy subjects. The k-nearest neighbor classifier with RDI as feature showed almost 100% classification rate.

Collisions of ageostrophic modons and formation of new types of coherent structures in rotating shallow water model

We study collisions of recently discovered ageostrophic modons in rotating shallow water model at different values of impact parameter and find that two new types of coherent vortex structures may be formed during this process: “nonlinear” modons, i.e., coherent dipoles with essentially nonlinear scatter plot and coherent tripoles. Both are known for incompressible 2D Euler equations, but were not reported in the “compressible” shallow water model. Inelastic scattering with strong filamentation and shearing is also possible. Surprisingly, the strongly nonlinear process of coherent structure formation leads to almost no emission of inertia-gravity waves.

Acoustic Rayleigh scattering at individual micron-sized bubbles

A microacoustic system based on a wide-bandwidth commercial piezoelectric transducer is presented in this letter. The system allows objective measurement of nonlinear Rayleigh scatter from single microbubbles. Two different types of microbubbles were exposed to a range of ultrasonic frequencies and amplitudes. Statistical examination of their scatter provides an understanding of their dissolution/destruction behavior and an insight on inertial cavitation. These high sensitivity measurements are key to the understanding of nonlinear scatter, may be employed to devise new signal processing techniques for imaging and better microbubble engineering.

Online planning and delivery technique for radiotherapy of spinal metastases using cone-beam CT: Image quality and system performance

To assess the feasibility of an online strategy for palliative radiotherapy (RT) of spinal bone metastasis, which integrates imaging, planning, and treatment delivery in a single step at the treatment unit. The technical challenges of this approach include cone-beam CT (CBCT) image quality for target definition, online planning, and efficient process integration. An integrated imaging, planning, and delivery system was constructed and tested with phantoms. The magnitude of CBCT image artifacts following the use of an antiscatter grid and a nonlinear scatter correction was quantified using phantom data and images of patients receiving conventional palliative RT of the spine. The efficacy of online planning was then assessed using corrected CBCT images. Testing of the complete process was performed on phantoms with assessment of timing and dosimetric accuracy. The use of image corrections reduced the cupping artifact from 30% to 4.5% on CBCT images of a body phantom and improved the accuracy of CBCT numbers (water: +/- 20 Hounsfield unit [HU], and lung and bone: to within +/- 130 HU). Bony anatomy was clearly visible and was deemed sufficient for target definition. The mean total time (n = 5) for application of the online approach was 23.1 min. Image-guided dose placement was assessed using radiochromic film measurements with good agreement (within 5% of dose difference and 2 mm of distance to agreement). The technical feasibility of CBCT-guided online planning and delivery for palliative single treatment has been demonstrated. The process was performed in one session equivalent to an initial treatment slot (<30 min) with dosimetric accuracy satisfying accepted RT standards.

Safety of the Galactose–Based Ultrasound Contrast Agent Levovist

The introduction of microbubble suspensions represents a new class of contrast agents for enhancement of vascular imaging in ultrasound. The effective ingredients of this class of contrast agents are acoustically active and produce micrometer-sized inhomogeneities in the blood pool. The microbubbles interact with the sound field either by scattering the incident sound beam or by oscillations that produce resonance, which at higher acoustic power can lead to the destruction of the microbubbles. Different processing of the various microbubble echo responses led to a number of new imaging modes that exhibit varying sensitivity and specificity for microbubble detection, of which the nonlinear scatter during destruction (“stimulated acoustic emission”) is the most sensitive, enabling the detection of a single microbubble in a capillary bed. With these techniques, the visualization of organ perfusion with ultrasound became possible. These agents are characterized not only by their physicochemical uniqueness but also by their unique pharmaceutical properties. All microbubble contrast agents can be considered to be “particulates,” which, by nature of their size, remain in the blood pool until the gas is dissolved or until they are sequestered by the reticulendothelial system (RES). Their character as blood pool agents makes them ideally suited for enhancing vascular imaging. The galactose–based agent Levovist (Schering AG, Berlin, Germany) was the first microbubble agent to enter the market with sufficient stability to provide enhancement of the total body blood pool following intravenous (IV) injection. Due to the particulate character, the risk profile of this new class of agents differs from contrast agents for x-ray or magnetic resonance imaging (MRI). The theoretical risks are generated by the tolerance of the tracer medium, its osmolality, the microbubble shell material, and the microbubble particles themselves. Gas bubbles may grow either by coalescence or by inward diffusion of gases, potentially occluding small vessels in the lung and periphery. In addition, microbubbles provide a theoretical nidus for cavitation. The purpose of this article is to report the broader experience in clinical routine as regards the safety of this new class of contrast agents.

Scattering of Spiral Density Waves to Lower Arm Number

It is shown that spiral density waves in astrophysical disks can undergo nonlinear resonance and scatter to waves with lower azimuthal wavenumber. The process is a fluid analog to nonlinear Landau damping, in which two linear modes exchange energy, mediated by a virtual beat mode. The scattering rate is calculated for a thin fluid disk model, using a weak turbulence expansion. It is shown that down-scattering is related to outward angular momentum transport and hence plays a role in mass accretion.

Piece-Wise Multiplicative Scatter Correction Applied to Near-Infrared Diffuse Transmittance Data from Meat Products

This paper presents a nonlinear scatter correction method, called piece-wise multiplicative scatter correction (PMSC), that is a further development of the multiplicative scatter correction (MSC) method. Near-infrared diffuse transmittance (NIT) data from meat and meat product samples were used to test the predictive performances of the PMSC and the MSC methods. With the use of PMSC, the prediction errors, expressed as the root mean square error of prediction (RMSEP), were improved by up to 36% for protein, up to 55% for fat, and up to 37% for water, in comparison to uncorrected data. The corresponding improvements by using PMSC compared to MSC were up to 22%, 24%, and 31% for protein, fat, and water, respectively.

Maserlike nonlinear scatter from human breath, a surface-enhanced far infrared scatter effect

A cotton tip applicator was utilized to stimulate far IR scatter (emission) from human breath. The reticulated cotton tip was vibrated at 200 Hz, the acoustic frequency that matches the average vibration frequency of common species of mosquitoes. Mosquitoes have open resonator dielectric sensillae (spines) on their antenna that match the 643 cm −1 (15.5) Cabannes line in the 667 cm −1 region of CO 2 rotation line, acoustic Stokes Brillouin and Stokes Raman lines are noted. Implications of such maserlike (coherent or partial coherent) scatter lines to insect control and disease diagnostics are discussed.

Non-linear multi-plane wave solutions of self-dual Yang-Mills theory

New solutions of self-dual Yang-Mills (SDYM) equations are constructed in Minkowski space-time for the gauge groupSL(2, ℂ). After proposing a Lorentz covariant formulation of Yang's equations, a set of Ansätze for exact non-linear multiplane wave solutions are proposed. The gauge fields are rational functions ofe x·ki (K 2 =0, 1≦i≦N) for these Ansätze. At least, three families of multisoliton type solutions are derived explicitly. Their asymptotic behaviour shows that non-linear waves scatter non-trivially in Minkowski SDYM.

Cross Sections and Radar Equation for Nonlinear Scatterers

The nonlinear system concepts of nonlinear transfer functions are extended to nonlinear cross sections which may be used to quantitatively describe the characteristics of a nonlinear scatter. The concept of nonlinear cross sections is used to generalize the radar equation for nonlinear scattering objects.