Spatial Width Research Articles

Spectral analysis of the extended linear discontinuous method for one-dimensional monoenergetic discrete ordinates transport problems in non-multiplying media

Accurate solution of neutron transport problems in the discrete ordinates (SN) formulations is relevant in many areas of engineering and nuclear science. Several researches have led to a variety of numerical differencing schemes in order to generate even more accurate numerical solutions. However, most differencing schemes seem to become unstable for sufficiently large spatial cell width and negative solutions may arise, which are non-physical results. In this work, we present a spectral analysis of the Extended Linear Discontinuous (ELD) and the classical Linear Discontinuous (LD) difference schemes for one-dimensional monoenergetic SN problems with isotropic scattering in non-multiplying media. This analysis can predict analytic threshold values for the discretization cell width, beyond which SN numerical solutions become unstable. Analytical threshold values were calculated by means of the spectrum of spatially discretized SN equations and tested by solving two model problems to compare the practical results with the theoretical predictions offered in this paper.

Trapping two types of Rayleigh particles simultaneously by a focused rotational elliptical Laguerre–Gaussian correlated Schell-model beam

We analyze the optical radiation forces, produced by a focused rotational elliptical Laguerre–Gaussian correlated Schell-model (ELGSM) beam, on the dielectric particles of different refractive indices in the Rayleigh scattering regime. It is found that through a judicious modulation of the initial spatial coherence width and the beam order of the correlation function of the rotational ELGSM beam, the particles with higher refractive index (compared with the ambient) can be trapped along an elliptical ring centered at the focus, the particles with lower refractive index, at the same time, will be trapped at the focal point. Our results also show that the trapping area/range can be modulated by structuring the correlation function of the beam. By comparing the gradient, scattering, Brownian, and gravity forces acting on the particles, the trapping stability is analyzed. Our results indicate that the coherence structure engineering can be used as an alternative approach to modulate the symmetry of the optical trapping area.

The dynamics of electron holes in current sheets

We present 1.5D Vlasov code simulations of the dynamics of electron holes in non-uniform magnetic and electric fields typical of current sheets and, particularly, of the Earth's magnetotail current sheet. The simulations show that spatial width and amplitude of electron holes do not substantially vary in the course of propagation, but there arises a double layer localized around the electron hole and manifested as a drop of the electrostatic potential along the electron hole. We demonstrate that electron holes produced around the neutral plane of a current sheet slow down in the course of propagation toward the current sheet boundaries. The leading contribution to electron hole braking is provided by the non-uniform magnetic field although electrostatic fields typical of the current sheets do provide a noticeable contribution. The simulations also show that electron holes with larger amplitudes are slowed faster. The simulation results suggest that some of the slow electron holes recently reported in the Earth's plasma sheet boundary layer may appear due to braking of initially fast electron holes in the course of propagation in the current sheet.

Broadband wide-angle active phased L-band antenna array emitters

The purpose of this article is to review and justify the choice of emitters for constructing energy-efficient high-performance broadband active phased L-band antenna array with wide-angle scanning in 2 planes. Phased antenna array characteristics, accepted as reference: wide scan angle in the H-plane  not less than ± 450; a wide range of frequencies  at least 40%; small overall dimensions of the radiating aperture, not allowing to consider the canvas without taking into account edge effects; high energy potential, which means high electric strength (up to 1 kW per channel); reduced spurious emission outside the scanning area (more than 45 °). Here are the requirements for the emitters of the above-described active phased antenna array: Emitters dimensions must comply with the structural requirements for the antenna array construction (array step, emitters arrangement method) and not «obscure» each other in the area of the working scanning angles in the E and H plane. Emitters spatial bottom width in the grating should not be less than the angular width of the area of electronic scanning of the active phased antenna array beam. Beam main lobe distortion in the scanning area by an amount higher than 1 dB is not allowed. The emitter in the grating should be consistent with the power system in the working range of scanning angles and frequencies. Reduced spurious emission in directions outside the scanning area. High efficiency, to ensure both reception and transmission, and sufficient dielectric strength with limited dimensions. As active phased antenna array emitters, the simplest weakly directional antennas are used, which is associated with their low cost and high manufacturability. Technical solutions in the class of vibrator antennas (dipoles) are subjected to further analysis. The use of dipole antenna arrays in wide-angle and broadband applications leads to a number of technical limitations, such as: limited broadband emitters (including and as part of the antenna array), determined by their design features and mutual influence; a limited sector of the formation of unidirectional radiation (shape stability (radiation pattern) in the frequency band, determined by the condition for the appearance of interference lobes and the mutual influence of the emitters, leading to distortion of the amplitude-phase distribution; the occurrence of the effect of «blinding» of the lattice in individual sectors of the scan and frequencies associated with the effects of external (spatial) and internal interaction of emitters. Based on the above requirements for emitters, taking into account the design features of the AFAR, the following most important technical problems can be identified, the solution of which must be considered: ensuring a wide working frequency band; ensuring consistency in a wide sector of scanning angles; ensuring a stable spatial pattern of the emitter in the grating. Consider the general constructive methods that can be used to solve the above problems. Group them according to the constituent structural elements of the vibrator: Shoulders shape of the vibrators. The main limitation of the classical symmetric vibrator emitter using is its small working frequency band (up to 10%). So the passband ( 2f ) of a symmetric half-wave vibrator can be estimated by the following expression [5, p. 187]: 4 73,1 2 f f0 ,  WВ where is WВ  the wave impedance of the vibrator. It is determined by the cross section, shape and length of the shoulders. Balancing device type. Using a coaxial line determines the presence of balancing devices to power the shoulders of the vibrators. In the decimeter range, various types of balancing devices are used, the basis of which are various loops (including the U-elbow), glasses, transformers and slots, as well as their combinations. 3. Reflector shape (including matching structural elements). In fixed sector vibrator headlamps, a solid conductive surface is usually used as a reflector. Its shape and location relative to the shoulders has a strong effect on the bottom of the emitter in the grating and the matching of the grating in wide scanning angles and in the frequency range. The factor taking into account the influence of a flat aperiodic reflector on the DN is estimated by the expression: Fра  sin(kdr cos ) , where is dr  the distance from the vibrator to the reflector.

A risk analysis procedure for urban trees subjected to wind- or rainstorm

Urban trees can play a crucial role in developing sustainable, safe and resilient cities, but at the same time they can pose risks. With an engineering approach, the study deals with a procedure able to quantify the risk that a tree subjected to the action of extreme wind events, without (windstorm) or with (rainstorm) ongoing precipitation, can cause by falling on potential targets. Such a Quantitative Risk Analysis (QRA) is based on the combination of four components (hazard, exposure, vulnerability and damage) that can be modeled more or less accurately depending on the objectives of the analysis. The innovative aspect is the characterization of the analysis, by means of two factors: the “Scale”, to describe the spatial width over which the QRA is performed, and the “Degree of Knowledge” (DoK), to state the accuracy used to estimate each QRA component. Firstly, QRA components and principles behind such a distinction in DoKs are explained. Then, the proposed procedure is tested by means of a practical example, where a sensitivity analysis considering different DoKs for hazard is carried out. Despite further studies are required to improve the procedure reliability, the results are encouraging. Even considering low DoKs, the procedure is able to quantify the risk that can be used in comparative terms, especially useful when quantifying the efficacy of risk mitigating actions.

Optogenetic Tuning Reveals Rho Amplification-Dependent Dynamics of a Cell Contraction Signal Network

SummaryLocal cell contraction pulses play important roles in tissue and cell morphogenesis. Here, we improve a chemo-optogenetic approach and apply it to investigate the signal network that generates these pulses. We use these measurements to derive and parameterize a system of ordinary differential equations describing temporal signal network dynamics. Bifurcation analysis and numerical simulations predict a strong dependence of oscillatory system dynamics on the concentration of GEF-H1, an Lbc-type RhoGEF, which mediates the positive feedback amplification of Rho activity. This prediction is confirmed experimentally via optogenetic tuning of the effective GEF-H1 concentration in individual living cells. Numerical simulations show that pulse amplitude is most sensitive to external inputs into the myosin component at low GEF-H1 concentrations and that the spatial pulse width is dependent on GEF-H1 diffusion. Our study offers a theoretical framework to explain the emergence of local cell contraction pulses and their modulation by biochemical and mechanical signals.

Silicon waveguide as virtual photonic bandgap structure array for realizing compact optical filters

ABSTRACT An engineered silicon rib waveguide on Silicon-On-Insulator platform which can act as virtual photonic bandgap structure is proposed. Selective periodic etching of materials from a rib waveguide is done to create a periodic rib-ridge structure. Each of the rib-ridge sections will therefore have different effective refractive indices and will act as virtual multilayered periodic structure or one-dimensional photonic bandgap structure. Their spatial positions and widths can be controlled to realize different type of photonic filters for integrated photonics applications. Realization of narrowband, multi-band and band-pass filter are shown here. These types of waveguide based monomaterial optical filters avoid the challenges generally faced while fabricating multilayer structures of different heterogeneous materials having different refractive indices. Moreover, as the device is waveguide based, its size is very small and will be useful for compact integrated photonics.

Influence of the degree of spatial coherence on the Goos–Hänchen shifts for a three-dimensional Dirac semimetal

We study the behavior of Goos–Hänchen shift (GHS) using s- and p-polarized partial coherent beam incident on three-dimensional (3D) Dirac semimetal. By studying the real part of permittivity of 3D Dirac semimetal, we identify the dielectric, epsilon near zero (ENZ) metamaterial, and metallic regions for the incident wavelength. Interestingly, for s- and p-polarized partial coherent beam, we get a completely different behavior of GHS in the reflected beam in the dielectric and metallic regions. Some factors such as spatial coherence, the wavelength and spatial width of the incident beam, temperature, and thickness of 3D Dirac semimetal are discussed in the influence of GHS. We can have negative and positive GH shifts in these three regions of Dirac semimetal for s- and p-polarized partial coherent beam.

1D and 2D error assessment and correction for extrusion-based bioprinting using process sensing and control strategies

The bioprinting literature currently lacks: (i) process sensing tools to measure material deposition, (ii) performance metrics to evaluate system performance, and (iii) control tools to correct for and avoid material deposition errors. The lack of process sensing tools limits in vivo functionality of bioprinted parts since accurate material deposition is critical to mimicking the heterogeneous structures of native tissues. We present a process monitoring and control strategy for extrusion-based fabrication that addresses all three gaps to improve material deposition. Our strategy uses a non-contact laser displacement scanner that measures both the spatial material placement and width of the deposited material. We developed a custom image processing script that uses the laser scanner data and defined error metrics for assessing material deposition. To implement process control, the script uses the error metrics to modify control inputs for the next deposition iteration in order to correct for the errors. A key contribution is the definition of a novel method to quantitatively evaluate the accuracy of printed constructs. We implement the process monitoring and control strategy on an extrusion-printing system to evaluate system performance and demonstrate improvement in both material placement and material width.

Sensitivity of age of air trends to the derivation method for non-linear increasing inert SF<sub>6</sub>

Abstract. Mean age of air (AoA) is a diagnostic of transport along the stratospheric Brewer–Dobson circulation. While models consistently show negative trends, long-term time series (1975–2016) of AoA derived from observations show non-significant positive trends in mean AoA in the Northern Hemisphere. This discrepancy between observed and modelled mean AoA trends is still not resolved. There are uncertainties and assumptions required when deriving AoA from trace gas observations. At the same time, AoA from climate models is subject to uncertainties, too. In this paper, we focus on the uncertainties due to the parameter selection in the method that is used to derive mean AoA from SF6 measurements in Engel et al. (2009, 2017). To correct for the non-linear increase in SF6 concentrations, a quadratic fit to the time series at the reference location, i.e. the tropical surface, is used. For this derivation, the width of the AoA distribution (age spectrum) has to be assumed. In addition, to choose the number of years the quadratic fit is performed for, the fraction of the age spectrum to be considered has to be assumed. Even though the uncertainty range due to all different aspects has already been taken into account for the total errors in the AoA values, the systematic influence of the parameter selection on AoA trends is described for the first time in the present study. For this, we use the EMAC (ECHAM MESSy Atmospheric Chemistry) climate model as a test bed, where AoA derived from a linear tracer is available as a reference and modelled age spectra exist to diagnose the actual spatial age spectra widths. The comparison of mean AoA from the linear tracer with mean AoA from a SF6 tracer shows systematic deviations specifically in the trends due to the selection of the parameters. However, for an appropriate parameter selection, good agreement for both mean AoA and its trend can be found, with deviations of about 1 % in mean AoA and 12 % in AoA trend. In addition, a method to derive mean AoA is evaluated that applies a convolution to the reference time series. The resulting mean AoA and its trend only depend on an assumption about the ratio of moments. Also in that case, it is found that the larger the ratio of moments, the more the AoA trend gravitates towards the negative. The linear tracer and SF6 AoA are found to agree within 0.3 % in the mean and 6 % in the trend. The different methods and parameter selections were then applied to the balloon-borne SF6 and CO2 observations. We found the same systematic changes in mean AoA trend dependent on the specific selection. When applying a parameter choice that is suggested by the model results, the AoA trend is reduced from 0.15 to 0.07 years per decade. It illustrates that correctly constraining those parameters is crucial for correct mean AoA and trend estimates and still remains a challenge in the real atmosphere.

Effects of 22q11 deficit syndrome on mental symptoms and cognitive function in children and adolescents with schizophrenia

To investigate the expression of 22 q11 deletion syndrome in children and adolescents with schizophrenia and its effect on mental symptoms and cognitive function. Case-control method was used. 134 cases of children and adolescents diagnosed with schizophrenia in hospital from April 2016 to December 2018 were selected as the case group, and the patients in the case group were divided into the two groups including 22 q11 deletion group and the non-deletion group. The control group included 418 healthy children with no history of mental illness or family history. In situ hybridization was used to diagnose 22 q11 microdeletion syndrome, and positive and negative symptom scales and Chinese version of schizophrenia cognitive function battery test were used to score the patients in the case group. The expression of 22 q11 microdeletion was more significant in children and adolescents with schizophrenia(χ~2=33. 52, P<0. 0001). The negative symptoms(P=0. 034), general condition(P=0. 005) and total score(P=0. 001) were significantly increased in the 22 q11 deletion group. The five indicators of attachment test, verbal memory, spatial span, emotional management, continuous operation and total score in the 22 q11 deletion group were significantly lower than those in the non-deletion group(P<0. 05). Among children and adolescents with schizophrenia, there was a significant decrease in the FA value in the 22 q11 deletion group compared with the non-deletion group, mainly distributed in the corpus callosum, the knee and the cingulate tract(P<0. 05), and no increase in the FA value was observed in other brain areas. FA value of corpus callosum somatic white matter in the absence group was positively correlated with visual memory and language fluency. FA value of the knee in corpus callosum was positively correlated with language fluency. FA value of the buckle was positively correlated with spatial width(all P values were less than 0. 05). 22 q11 microdeletion is more common in children and adolescents with schizophrenia, which may affect visual memory, language fluency and spatial span by reducing FA values in corpus callosum, knee and cingulate tract.

Effect of outer scale on partially coherent Sinh-Gaussian beams in inhomogeneous atmospheric turbulence

The root-mean-square (rms) spatial and angular widths of partially coherent Sinh-Gaussian (PCShG) beams propagating through inhomogeneous atmospheric turbulence are investigated based on the generalized extended Huygens-Fresnel principle. Analytical formulae of the rms spatial and angular widths are derived, and the effect of the outer scale on the beam spreading for PCShG beams in inhomogeneous atmospheric turbulence is also studied by using the modified von Kármán spectrum and Hufnagel-Valley atmospheric turbulence profile model. The impacts of the turbulent parameters (inner scale and outer scale), coherent parameter and decentered parameter on PCShG beams are discussed by numerical calculations. It is shown that the rms spatial width increases with increasing the outer scale, and the effect is obvious especially for the PCShG beam with the smaller decentered parameters and larger zenith angles. Typically, the saturation value of rms angular width becomes larger for a larger outer scale.

Noise-resolution uncertainty principle in classical and quantum systems

We show that the width of an arbitrary function and the width of the distribution of its values cannot be made arbitrarily small simultaneously. In the case of ergodic stochastic processes, an ensuing uncertainty relationship is then demonstrated for the product of correlation length and variance. A closely related uncertainty principle is also established for the average degree of fourth-order coherence and the spatial width of modes of bosonic quantum fields. However, it is shown that, in the case of stochastic and quantum observables, certain non-classical states with sub-Poissonian statistics, such as for example photon number squeezed states in quantum optics, can overcome the “classical” noise-resolution uncertainty limit. This uncertainty relationship, which is fundamentally different from the Heisenberg and related uncertainty principles, can define an upper limit for the information capacity of communication and imaging systems. It is expected to be useful in a variety of problems in classical and quantum optics and imaging.

A survey of the recent architectures of deep convolutional neural networks

Deep Convolutional Neural Network (CNN) is a special type of Neural Networks, which has shown exemplary performance on several competitions related to Computer Vision and Image Processing. Some of the exciting application areas of CNN include Image Classification and Segmentation, Object Detection, Video Processing, Natural Language Processing, and Speech Recognition. The powerful learning ability of deep CNN is primarily due to the use of multiple feature extraction stages that can automatically learn representations from the data. The availability of a large amount of data and improvement in the hardware technology has accelerated the research in CNNs, and recently interesting deep CNN architectures have been reported. Several inspiring ideas to bring advancements in CNNs have been explored, such as the use of different activation and loss functions, parameter optimization, regularization, and architectural innovations. However, the significant improvement in the representational capacity of the deep CNN is achieved through architectural innovations. Notably, the ideas of exploiting spatial and channel information, depth and width of architecture, and multi-path information processing have gained substantial attention. Similarly, the idea of using a block of layers as a structural unit is also gaining popularity. This survey thus focuses on the intrinsic taxonomy present in the recently reported deep CNN architectures and, consequently, classifies the recent innovations in CNN architectures into seven different categories. These seven categories are based on spatial exploitation, depth, multi-path, width, feature-map exploitation, channel boosting, and attention. Additionally, the elementary understanding of CNN components, current challenges, and applications of CNN are also provided.

Texture Recognition Using Gabor Filter for Extracting Feature Vectors With the Regression Mining Algorithm

This article considered only natural types of texture and then applying the Gabor filter for better classifications. The concept used is to discard the stochastic features to avoid any mixing of feature vector while it is extracting from the image dataset. The proposed approach has considered the Gabor filter for texture recognition primarily but with the combined method of spatial width and orientation to get the optimal alignment, this optical alignment mine the maximum feature vector by applying the REP algorithm over the data mined from the texture. This will result in better accuracy in the results. Initially, the frequency response over the surface due to applying Gabor filter has been calculated and then the work proceeded in a manner that first natural images are loaded into the MATLAB tool then it is preprocessed, and then final classifications are performed for final results. The primarily concentrated over texture information of image datasets rather than the multispectral information along with REP regression algorithm to do actual mining of feature vectors. Unlike the conventional approach of the Gabor filter, this article focuses on the variance and spatial relationship between two or more than two pixels. The deviation calculated is used for normalizing the feature vectors, and the accuracy can be hence increase using the proposed commuted technique.

Sparse recovery methodologies for quasi-distributed dynamic strain sensing

Quasi-distributed measurement of strain and/or temperature is often implemented using arrays of weakly reflecting fiber Bragg gratings (FBGs) whose reflection peaks are centered at the same nominal wavelength. The signals are obtained by measuring the phase difference between the reflections of consecutive FBGs. Typically, in such a system, the spatial resolution of the interrogator must be compatible with the spatial separation between consecutive FBGs. Insufficient resolution leads to an overlap of reflection peaks, a decrease in the differential-phase signal and poor sensitivity. In this paper, we study the use of two different sparsity based methodologies for improving the sensitivity of such quasi distributed acoustic sensing systems in the case where traditional signal processing approaches do not provide sufficient spatial resolution. These methods enable relaxing the requirements regarding the interrogator or, alternatively, reducing the needed separation between reflectors. Experimentally, these techniques were used to measure 1 kHz dynamic strain induced in a fiber segment between two discrete reflectors, located at the end of a 4 km long fiber. The separation between the reflectors was 18 m while the pulse (spatial) width was intentionally chosen bigger than that. It yielded approximately 5 dB increase in the measured signal compared to the traditional processing approach and an order of magnitude improvement in the sensitivity, .

Estimation of Variance and Spatial Correlation Width for Fine-Scale Measurement Error in Digital Elevation Model

In this article, we borrow from the blind noise parameter estimation (BNPE) methodology early developed in the image processing field an original and innovative no-reference approach to estimate digital elevation model (DEM) vertical error parameters without resorting to a reference DEM. The challenges associated with the proposed approach related to the physical nature of the error and its multifactor structure in DEM are discussed in detail. A suitable multivariate method is then developed for estimating the error in gridded DEM. It is built on a recently proposed vectorial BNPE method for estimating spatially correlated noise using noise informative areas and fractal Brownian motion. The new multivariate method is derived to estimate the effect of the stacking procedure and that of the epipolar line error on local (fine-scale) standard deviation and autocorrelation function width of photogrammetric DEM measurement error. Applying the new estimator to Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) GDEM2 and Advanced Land Observing Satellite (ALOS) World 3D DEMs, good agreement of derived estimates with results available in the literature is evidenced. Adopted for TanDEM-X-DEM, estimates obtained agree well with the values provided in the height error map. In future works, the proposed no-reference method for analyzing DEM error can be extended to a larger number of predictors for accounting for other factors influencing remote sensing (RS) DEM accuracy.

Mid-infrared diffraction-free space-time wave packets

Joint structuring of the spatio-temporal spectrum of a pulsed optical beam can lead to a host of unusual properties, such as diffraction-free propagation and tunable group velocities in free space. Such ‘space-time’ wave packets have been synthesized exclusively in the visible and near-infrared spectral regions. Here we synthesize the first space-time wave packet in the mid-infrared exploiting a transmissive phase plate fabricated via gray-scale lithography. A mid-infrared wave packet having a bandwidth of ∼60 nm at a wavelength of 2.35 μm is synthesized such that its transverse width is ∼300 μm and is monitored for a propagation distance of 7 m, corresponding to 80 × the Rayleigh range of a Gaussian beam at the same wavelength and having the same initial transverse spatial width. The experimental methodology presented here and the reported results will help appropriate spatio-temporally structured light in the mid-infrared for a wide variety of applications including imaging, sensing, and metrology.

Analytical and semi-analytical ample solutions of the higher-order nonlinear Schrödinger equation with the non-Kerr nonlinear term

In this paper, we investigate distinct novel analytical and semi-analytical solutions of the higher-order nonlinear Schrödinger equation with the non-Kerr nonlinear term by the employment of there different schemes. These schemes are the generalized auxiliary equation method, the generalized exp--ϕξ expansion method, and the Adomain decomposition method that are considered as useful tools in this field. The suggested model in this study is used to explore the dynamics of light pulses for sub-10-fs-pulse propagation in the framework of computational simulations. The primary research of our study focuses on the case where the carrier wavelength of the soliton is much shorter than the spatial width. Herewith, the soliton frequency is smaller than the carrier frequency. The shorter femtosecond pulses (<100fs) is desired to increase the bit rate of pulse propagation. Their loss for the short-wavelength pulses that are propagating through the wave-guide is negligible. New analytical solutions are obtained, then it used to evaluate the initial and boundary conditions that are used in calculating the semi-analytical. Moreover, the accuracy of obtained solutions is explained by evaluating the absolute value of error between the obtained analytical and semi-analytical.

Optical wave solutions of the higher-order nonlinear Schrödinger equation with the non-Kerr nonlinear term via modified Khater method

This research paper studies the optical soliton wave solutions of the model of sub-10-fs-pulse propagation by the implementation of the modified Khater method. This model describes the dynamics of light pulses that represent a higher-order nonlinear Schrödinger equation with the non-Kerr nonlinear term. The validity of this model depends on one primary hypothesis, which is the carrier wavelength of the soliton is much shorter than the spatial width. This means that the amplitude of the soliton frequency must be less than the carrier frequency. The shorter femtosecond pulses ([Formula: see text]100 fs) are desired to increase the bit rate of pulse propagation. The losing of distribution in such short-wavelength pulses through waveguides is a negligible loss. Our solitary analytical wave solutions are approved with the waveguide made of highly nonlinear optical materials.