Статті в журналах з теми "Mode field spatial distribution"
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1
RAGHU KANTH, S. T. G. "INTRINSIC MODE FUNCTIONS OF EARTHQUAKE SLIP DISTRIBUTION." Advances in Adaptive Data Analysis 02, no. 02 (April 2010): 193–215. http://dx.doi.org/10.1142/s1793536910000458.
Повний текст джерелаАнотація:
In this paper, empirical mode decomposition technique is used to analyze the spatial slip distribution of five past earthquakes. It is shown that the finite fault slip models exhibit five empirical modes of oscillation. The last intrinsic mode is positive and characterizes the non-stationary mean of the slip distribution. This helps in splitting the spatial variability of slip into trend and the remaining modes sum as the fluctuation in the data. The fluctuation component indicates that it can be modeled as an anisotropic random field. Important parameters of this random field have been estimated. The effect of these modes on ground motion is presented by simulating both acceleration and displacement time histories.
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Ledneva, H. P., A. V. Korzhov, L. A. Kotomtseva, and L. G. Astafyeva. "The effect of spatial field distribution on two-mode lasing in a spherical microparticle." Optics and Spectroscopy 94, no. 3 (March 2003): 476–80. http://dx.doi.org/10.1134/1.1563697.
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Sangeetha, S., and S. T. G. Raghukanth. "A Stochastic source model for the 2015 Mw 7.9 Gorkha, Nepal, Earthquake using Multi-Dimensional Ensemble Empirical Mode Decomposition technique." MATEC Web of Conferences 148 (2018): 08004. http://dx.doi.org/10.1051/matecconf/201814808004.
Повний текст джерелаАнотація:
The present study aims at developing a new strategy to model the spatial variability of slip on the rupture plane using multi-dimensional ensemble empirical mode decomposition (MEEMD) technique. Here, the earthquake slip distribution is split into finite number of empirical modes of oscillation called the intrinsic mode functions (IMFs). This help in identifying the fluctuation component and trend in the slip data. The trend is positive and characterizes the nonstationary mean of the slip distribution. The fluctuation component can be modelled as a stationary random field using an exponential power spectral density function. The trend can be modeled as an elliptic patch. This new technique is demonstrated for the slip distribution of the recent Nepal Earthquake, 2015. It is observed that the new model can be used to simulate the spatial complexity of slip distribution of any earthquake.
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Kuo, C.-W., M. Crawley, J. Cluts, and M. Samimy. "Near-field pressure waveform analysis of an excited Mach 0.9 jet." International Journal of Aeroacoustics 17, no. 1-2 (February 24, 2018): 114–34. http://dx.doi.org/10.1177/1475472x17743631.
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This work explores the effects of axisymmetric, helical, and flapping mode perturbations over a range of Strouhal numbers on the near-field pressure of an axisymmetric Mach 0.9 jet with a Reynolds number of 6.2 × 105. Excitation is generated by eight localized arc filament plasma actuators uniformly distributed around the nozzle exit. The excitation of jet shear layer instabilities resulted in large-scale structures. The signature of these structures in the irrotational near field appears as high-amplitude hydrodynamic pressure fluctuations with wavepacket-like growth, saturation, and decay. The excitation Strouhal number and, perhaps more importantly, the azimuthal mode, are seen to strongly affect the spatial evolution of the wavepacket in both axial and radial directions. The dominant excitation Strouhal number is around 0.3, and the most significant effect on the jet statistical properties (such as distributions of velocity and pressure) occurs further downstream for the flapping mode in comparison to the axisymmetric mode. Dynamic mode decomposition is performed to further describe the modal behavior and evolution of hydrodynamic pressure fluctuations. The pressure response in the near field of jet plumes in flapping mode excitation is shown to exhibit two azimuthal mode behaviors: axisymmetric and flapping. An empirical model of hydrodynamic pressure distribution is established with normalized axial and radial profiles. The amplitude and distribution of the hydrodynamic pressure component are well depicted by the empirical reconstruction.
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Liu, Yongkai, Jianli Wang, Lie Ma, Shijie Gao, Chenzi Guo, Kainan Yao, and Lei Sheng. "The Effect of Spatial Mode Distribution on Coupling Efficiency of Single-Mode Fiber: Theoretical Analysis and Experimental Verification." Applied Sciences 9, no. 16 (August 11, 2019): 3296. http://dx.doi.org/10.3390/app9163296.
Повний текст джерелаАнотація:
In this study, Zernike polynomials and optical fiber field theory are applied to build a mathematical model of coupling efficiency (CE) and spatial mode of aberrations. The theory built in this paper can be used to quickly calculate the CE affected by a single aberration as well as the aberrations caused by atmospheric turbulence. The aberrations are classified based on Zernike polynomials and the effects of aberrations on CE of different types and different spatial frequencies are analyzed. The influence of the effects of AO system residual errors is also analyzed. Adaptive optics (AO) equipment is applied to build a system on which the proposed theory was tested; the experimental results validate the theoretical analysis.
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Casper, Katya M., Justin L. Wagner, Steven J. Beresh, Russell W. Spillers, John F. Henfling, and Lawrence J. Dechant. "Spatial distribution of pressure resonance in compressible cavity flow." Journal of Fluid Mechanics 848 (June 11, 2018): 660–75. http://dx.doi.org/10.1017/jfm.2018.346.
Повний текст джерелаАнотація:
The development of the unsteady pressure field on the floor of a rectangular cavity was studied at Mach 0.9 using high-frequency pressure-sensitive paint. Power spectral amplitudes at each cavity resonance exhibit a spatial distribution with a streamwise-oscillatory pattern; additional maxima and minima appear as the mode number is increased. This spatial distribution also appears in the propagation velocity of modal pressure disturbances. This behaviour was tied to the superposition of a downstream-propagating shear-layer disturbance and an upstream-propagating acoustic wave of different amplitudes and convection velocities, consistent with the classical Rossiter model. The summation of these waves generates a net downstream-travelling wave whose amplitude and phase velocity are modulated by a fixed envelope within the cavity. This travelling-wave interpretation of the Rossiter model correctly predicts the instantaneous modal pressure behaviour in the cavity. Subtle spanwise variations in the modal pressure behaviour were also observed, which could be attributed to a shift in the resonance pattern as a result of spillage effects at the edges of the finite-width cavity.
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Durán, O., V. Schwämmle, P. G. Lind, and H. J. Herrmann. "Size distribution and structure of Barchan dune fields." Nonlinear Processes in Geophysics 18, no. 4 (July 13, 2011): 455–67. http://dx.doi.org/10.5194/npg-18-455-2011.
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Abstract. Barchans are isolated mobile dunes often organized in large dune fields. Dune fields seem to present a characteristic dune size and spacing, which suggests a cooperative behavior based on dune interaction. In Duran et al. (2009), we propose that the redistribution of sand by collisions between dunes is a key element for the stability and size selection of barchan dune fields. This approach was based on a mean-field model ignoring the spatial distribution of dune fields. Here, we present a simplified dune field model that includes the spatial evolution of individual dunes as well as their interaction through sand exchange and binary collisions. As a result, the dune field evolves towards a steady state that depends on the boundary conditions. Comparing our results with measurements of Moroccan dune fields, we find that the simulated fields have the same dune size distribution as in real fields but fail to reproduce their homogeneity along the wind direction.
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Козырева, Ольга, Olga Kozyreva, Вячеслав Пилипенко, Vyacheslav Pilipenko, Марк Энгебретсон, Mark Engebretson, Дмитрий Климушкин, Dmitriy Klimushkin, Павел Магер, and Pavel Mager. "Correspondence between the ULF wave power spatial distribution and auroral oval boundaries." Solar-Terrestrial Physics 2, no. 2 (August 10, 2016): 46–65. http://dx.doi.org/10.12737/20999.
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The world-wide spatial distribution of the wave power in the Pc5 band during magnetic storms has been compared with auroral oval boundaries. The poleward and equatorward auroral oval boundaries are estimated using either the British Antarctic Survey database containing IMAGE satellite UV observations of the aurora or the OVATION model based on the DMSP particle data. The “epicenter” of the spectral power of broadband Pc5 fluctuations during the storm growth phase is mapped inside the auroral oval. During the storm recovery phase, the spectral power of narrowband Pc5 waves, both in the dawn and dusk sectors, is mapped inside the auroral oval or around its equatorward boundary. This observational result confirms previously reported effects: the spatial/temporal variations of the Pc5 wave power in the morning/pre-noon sector are closely related to the dynamics of the auroral electrojet and magnetospheric field-aligned currents. At the same time, narrowband Pc5 waves demonstrate typical resonant features in the amplitude-phase latitudinal structure. Thus, the location of the auroral oval or its equatorward boundary is the preferred latitude for magnetospheric field-line Alfven resonator excitation. This effect is not taken into account by modern theories of ULF Pc5 waves, but it could be significant for the development of more adequate models.
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Dubrovin, V. F. "The field radiated by a single-mode optical waveguide excited by a field with a complex amplitude-phase spatial distribution." Journal of Communications Technology and Electronics 57, no. 12 (December 2012): 1249–53. http://dx.doi.org/10.1134/s1064226912110034.
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Wei, Shusheng, and Wusong Wen. "Antenna Current Calculation Based on Equivalent Transmission Line Model." Micromachines 13, no. 5 (April 30, 2022): 714. http://dx.doi.org/10.3390/mi13050714.
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This paper provides a new way for spatial current/field profiles for frequency-selective surface analytical approximation. It confirms that the per unit length radiation resistance of an equivalent transmission line model for line antenna has little influence on the normalized current distribution. The two-wire equivalent transmission line model (typically used for transmitting line antenna) is applied to the receiving line antenna. In this case, the corresponding incident field is decomposed into odd and even mode for asymmetric distribution. A one-wire equivalent transmission line model is then introduced for any antenna composed of relative narrow strips. The incident field does not need to be decomposed. According to the simulation, the transmission line loss has little influence on the current distribution.
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Amato, E. "A Model for the Spatial Distribution of Relativistic Electrons in the Crab Nebula." Symposium - International Astronomical Union 195 (2000): 371–72. http://dx.doi.org/10.1017/s0074180900163144.
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A model for the spatial distribution of relativistic electrons in the Crab Nebula is proposed. Particles injected in the vicinity of the pulsar propagate in a magnetic field of time-dependent but spatially constant intensity. A good description of the nebular synchrotron emission, from radio to X-ray frequencies, is obtained if particle diffusion with respect to the azimuthal field lines is taken into account.
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Consoli, Fabrizio, Luigi Celona, Giovanni Ciavola, Santo Gammino, Fabio Maimone, Rocco Salvatore Catalano, Sebastiano Barbarino, David Mascali, and Livia Tumino. "Dependence on Frequency of the Electromagnetic Field Distribution inside a Cylindrical Cavity Excited through an Off-Axis Aperture." Active and Passive Electronic Components 2008 (2008): 1–4. http://dx.doi.org/10.1155/2008/859052.
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To explain the relevant changes in the electron cyclotron resonance ion source behaviour for small variations of the exciting radiation frequency, we determine the spatial distribution of the field within the cavity for every resonant mode.
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Pathirana, A., and S. Herath. "Multifractal modelling and simulation of rain fields exhibiting spatial heterogeneity." Hydrology and Earth System Sciences 6, no. 4 (August 31, 2002): 695–708. http://dx.doi.org/10.5194/hess-6-695-2002.
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Abstract. Spatial multifractals are statistically homogeneous random fields. While being useful to model geophysical fields exhibiting a high degree of variability and discontinuity and including rainfall, they ignore the spatial trends embedded in the variability that are evident from large temporal aggregation of spatial fields. The modelling of rain fields using multifractals causes the information related to spatial heterogeneity, immensely important at some spatial scales, to be lost in the modelling process. A simple method to avoid this loss of the heterogeneity information is proposed. Instead of modelling rain fields directly as multifractals, a derived field M is modelled; this is the product of filtering observed rainfall snapshots with spatial heterogeneity as indicated by long term accumulations of rain fields. The validity of considering the field M as multifractal is investigated empirically. The applicability of the proposed method is demonstrated using a discrete cascade model on gauge-calibrated radar rainfall of central Japan at a daily scale. Important parameters of spatial rainfall, like the distribution of wet areas, spatial autocorrelation and rainfall intensity distributions at different geographic locations with different amounts of average rainfall, were faithfully reproduced by the proposed method. Keywords: spatial rainfall, downscaling, multifractals
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LUO, XIANGANG, YUEGUANG LV, CHUNLEI DU, JUNXIAN MA, HAO WANG, HAIYING LI, GAIRONG YANG, and HANMIN YAO. "SPATIAL DISTRIBUTION OF SURFACE PLASMON POLARITON FROM METALLIC NANOSTRUCTURES." Modern Physics Letters B 19, no. 12 (May 30, 2005): 599–606. http://dx.doi.org/10.1142/s0217984905008578.
Повний текст джерелаАнотація:
The spatial distribution of the interference of surface plasmon polariton (SPP) on metallic nanostructures has been studied. The results show that the transmission of electromagnetic radiation is remarkably enhanced for frequencies close to the surface plasmon band and the interference of SPP can redistribute the illumination light into subwavelength-scale spatial distribution with high intensity, which beats the Rayleigh diffraction limit. For an appropriate thickness, the transmission of an unperforated structure can be larger than that of holes or slits systems with the same periodicity and thickness when the coupled surface plasmon wave mode is excited. With the help of the interference of the horizontal plasmon excited by Bragg resonance due to the periodicity in the horizontal direction, the vertical plasmons, excited in z direction via Fabry–Perot cavity resonance in different grooves, are correlated, so the transmission is increased via the tunneling process. The properties of transparency for light but impenetrability for gas and liquid will be of importance for device applications. The information on near-field distribution from perforated metallic structures is important for understanding the underlying physics, as well as for optimizing photonic crystals for possible applications.
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Okayasu, Akio, Tomoya Shibayama, and Nobuo Mimura. "VELOCITY FIELD UNDER PLUNGING WAVES." Coastal Engineering Proceedings 1, no. 20 (January 29, 1986): 50. http://dx.doi.org/10.9753/icce.v20.50.
Повний текст джерелаАнотація:
In order to clarify the characteristics of the velocity field in the surf zone, three sets of detailed and precise two dimensional laboratory experiments were performed. Spatial distributions and time histories of velocity were measured by using a hot film velocimeter with a split type probe or a two components laser doppler velocimeter for regular wave conditions. Typical plunging breakers were formed during the experiments. Based on the experimental results, a model was investigated in order to estimate the two dimensional distribution of the on-offshore steady current below the trough level.
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Yakushev, Viktor, Aleksey Petrushin, Olga Mitrofanova, Evgenii Mitrofanov, Vitaly Terleev, and Aleksandr Nikonorov. "Spatial distribution prediction of agro-ecological parameter using kriging." E3S Web of Conferences 164 (2020): 06030. http://dx.doi.org/10.1051/e3sconf/202016406030.
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In modern agroecology, one of the most pressing problems is the problem of spatial data mapping. The development of information technology opens up a wide range of approaches for solving this problem. One of these approaches is based on the use of geostatistical methods. This study was carried out with the aim of developing ideas about the applicability of the ordinary kriging method for predicting the spatial distribution of the agro-ecological indicator with identifying the boundaries of in-field heterogeneity according to remote sensing data. For the model computational experiment, aerial photographs of the agricultural field in the red and near infrared ranges were used, which made it possible to obtain sets of uniformly distributed values of the vegetative index NDVI that were randomly generated. The high spatial resolution of the images allowed us to analyze the observational data for the studied agricultural field.
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Gautier, Athénaïs, David Ginsbourger, and Guillaume Pirot. "Goal-oriented adaptive sampling under random field modelling of response probability distributions." ESAIM: Proceedings and Surveys 71 (August 2021): 89–100. http://dx.doi.org/10.1051/proc/202171108.
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In the study of natural and artificial complex systems, responses that are not completely determined by the considered decision variables are commonly modelled probabilistically, resulting in response distributions varying across decision space. We consider cases where the spatial variation of these response distributions does not only concern their mean and/or variance but also other features including for instance shape or uni-modality versus multi-modality. Our contributions build upon a non-parametric Bayesian approach to modelling the thereby induced fields of probability distributions, and in particular to a spatial extension of the logistic Gaussian model. The considered models deliver probabilistic predictions of response distributions at candidate points, allowing for instance to perform (approximate) posterior simulations of probability density functions, to jointly predict multiple moments and other functionals of target distributions, as well as to quantify the impact of collecting new samples on the state of knowledge of the distribution field of interest. In particular, we introduce adaptive sampling strategies leveraging the potential of the considered random distribution field models to guide system evaluations in a goal-oriented way, with a view towards parsimoniously addressing calibration and related problems from non-linear (stochastic) inversion and global optimisation.
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Levchenko, Larysa. "Modeling the spatial distribution of magnetic fields of low frequency multiple sources." Advanced Information Systems 5, no. 2 (June 22, 2021): 34–37. http://dx.doi.org/10.20998/2522-9052.2021.2.05.
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The work is show that in conditions of dense the location of electrical equipment in the premises, buildings and on territories to ensure the regulatory levels of electromagnetic compatibility of personnel and the population, it is advisable to carry out preliminary modeling of the propagation of electromagnetic fields it is advisable. Considering the insignificant shielding of the magnetic field by the equipment cases, it is advisable to carry out modeling based on the magnetic component of the electromagnetic field. The mathematical ratio of the propagation of the magnetic field of individual sources, taking into account their dipole model, has been determined. The modeling was carried out for sources of the dipole and dipole-quadrupole types. Three-dimensional models of sources with the propagation of dipole, quadrupole and dipole-quadrupole harmonics of the field are provided, using the Matlab package. Application software has been developed in the C environment, using the SQL server database, and modeling of the propagation of the magnetic field of many sources in a certain plane has been carried out. This result is show that even for electrical equipment that operates to determine the reduced magnetic field isolines experimentally very difficult. At the design stages of equipment placement, modeling is the only tool for predicting the electromagnetic environment, which determines the electromagnetic compatibility of technical equipment and the electromagnetic safety of personnel and the public.
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Li, Guang-Xin, Ming-Bo Sun, Yi-Xin Yang, Tai-Yu Wang, and Yuan Liu. "Spatial structural characteristics of a combustion flow field in an ethylene-fueled supersonic combustor with a rear-wall-expansion cavity." Modern Physics Letters B 34, no. 18 (June 23, 2020): 2050208. http://dx.doi.org/10.1142/s0217984920502085.
Повний текст джерелаАнотація:
A hybrid large eddy simulation (LES)/assumed subgrid probability density function (PDF) closure model was employed to investigate the structural characteristics of the combustion flow field in an ethylene-fueled supersonic combustor with a rear-wall-expansion cavity. The wall pressure distribution from numerical simulation was compared with experimental data, and the numerical results are in good agreement with the experimental data. The spatial distribution characteristics of combustion heat release in the flow field are obtained from the simulation results. The reaction heat release zone is mainly distributed in the cavity. The cavity shear layer forms a concentrated reaction zone that produces a large amount of chemical heat release, thus further maintaining local stable combustion and forming a flame base. The front part of the cavity shear layer has the highest temperature in the whole flow field. There is still excess fuel reaching the cavity rear wall and producing a certain intensity of reaction. In addition, a dispersed small flame intermittently forms in the downstream near-wall region. The premixed combustion mode dominates the cavity recirculation zone, while the combustion in the downstream region evidently shows a non-premixed mode.
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Buland, Arild, Odd Kolbjørnsen, and Henning Omre. "Rapid spatially coupled AVO inversion in the Fourier domain." GEOPHYSICS 68, no. 3 (May 2003): 824–36. http://dx.doi.org/10.1190/1.1581035.
Повний текст джерелаАнотація:
Spatial coupling of the model parameters in an inversion problem provides lateral consistency and robust solutions. We have defined the inversion problem in a Bayesian framework, where the solution is represented by a posterior distribution obtained from a prior distribution and a likelihood model for the recorded data. The spatial coupling of the model parameters is imposed via the prior distribution by a spatial correlation function. In the Fourier domain, the spatially correlated model parameters can be decoupled, and the inversion problem can be solved independently for each frequency component. For a spatial model parameter represented on n grid nodes, the computing time for the inversion in the Fourier domain follows a linear function of the number of grid nodes, while the computing time for the fast Fourier transform follows an n log n function. We have developed a 3D linearized amplitude variation with offset (AVO) inversion method with spatially coupled model parameters, where the objective is to obtain posterior distributions for P‐wave velocity, S‐wave velocity, and density. The inversion algorithm has been tested on a 3D dataset from Sleipner field with 4 million grid nodes, each with three unknown model parameters. The computing time was less than 3 minutes on the inversion in the Fourier domain, while each 3D Fourier transform used about 30 s on a single 400‐MHz Mips R12000 CPU.
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Li, Guo Dong, Jun Hua Zhang, Zi Sheng Zhao, and Li Ping Zhao. "Application of Geostatistics Model Based on Geographic Information System in Urban Heat Environment." Applied Mechanics and Materials 58-60 (June 2011): 2303–7. http://dx.doi.org/10.4028/www.scientific.net/amm.58-60.2303.
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Geographic Information System (GIS) database is built by ArcGIS software based on observation data in Lanzhou city. GIS data set was analyzed, including testing data distribution, the trend analysis of spatial data, data outlier analysis. According to the analysis results, the appropriate spatial analysis model is chosen to simulate and predict thermal field. Cross validation method is used to verify simulation accuracy and validity of model. Simulation map of urban thermal in is output by optimal model and parameters eventually. Results show that urban thermal field presents regular distribution in summer. The spatial distribution characteristics of thermal field have directly relations with land use type, urban energy consumption, population density, building volume rate, and thermodynamic properties of underlying surface.
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Salnikov, M. V. "Approximate determination of the plasma potential spatial distribution in the isolated dust particle vicinity." Journal of Physics: Conference Series 2119, no. 1 (December 1, 2021): 012169. http://dx.doi.org/10.1088/1742-6596/2119/1/012169.
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Abstract In this paper, results of two numerical models are compared. The main purpose of these models is to determine the self-consistent spatial distributions of plasma (electric potential and space charge) near isolated spherical dust particles. In the first model, the spatial distribution of the self-consistent plasma potential is determined by expanding the plasma space charge spatial distribution in Legendre polynomials; in the second model, it is determined by direct numerical integration of the Poisson equation solution. The results show that the dependences of the system main parameters (wake magnitude and position, dipole moment of the ion cloud) coincide for small values of the external electrostatic field. With an increase in the external field strength, the dependences for two models cease to coincide, which is due to the inapplicability of Legendre polynomial decomposition in the case of strong anisotropy.
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Ohashi, Hideo. "Case Study of Pump Failure Due to Rotor-Stator Interaction." International Journal of Rotating Machinery 1, no. 1 (1994): 53–60. http://dx.doi.org/10.1155/s1023621x94000059.
Повний текст джерелаАнотація:
Fluiddynamic interaction between rotor and stator generates local pressure fluctuation and can be a cause ofstructural vibration of turbomachines. The interaction produces a spatial distribution of pressure fluctuation with a certain diametrical mode and propagating speed, known as rotating pressure field. When the frequency and mode of a rotating pressure field coincide with those of the structural vibration, a fluid-excited resonance takes place, leading to eventual severe structural damage. An example of such damage is described in detail using the case of PLR pump failure of a BWR plant.
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SURIYAGODA, L. D. B., M. H. RYAN, H. LAMBERS, and M. RENTON. "Comparison of novel and standard methods for analysing patterns of plant death in designed field experiments." Journal of Agricultural Science 150, no. 3 (July 4, 2011): 319–34. http://dx.doi.org/10.1017/s0021859611000566.
Повний текст джерелаАнотація:
SUMMARYThe present paper compares standard and novel methods for analysing aggregated patterns of plant death in designed field experiments; these methods include binomial (BN), beta-binomial (BBN), logistic-normal-binomial (LNB), BN models with random blocks, BN models with smooth-scale spatial components and principal coordinates of neighbour matrices (PCNM). PCNM is a relatively new technique used in ecology to determine how much observed variability can be explained by spatial and environmental variables, and has not yet been applied to agricultural studies. The survival data of two pasture species, collected from a designed field experiment that was replicated at multiple locations, were used. First, the occurrence of overdispersion was tested using the BN and BBN distributions. Goodness-of-fit tests proved that the BBN model provided a better description (better fit) of the observed data in some cases than did the BN distribution, indicating overdispersion was present. When overdispersion was not present, the BN distribution was adequate to describe the data, and the use of the BBN distribution was superfluous. It is then shown that the PCNM approach, the BN model with smooth-scale spatial components and the LNB model were able to account for some of the variation as spatial variability, thus reducing the species effect compared with that explained under the standard BN model. The amount of variation among species according to the BN model and the BN model with random blocks was similar. Therefore, it is argued that the novel PCNM approach warrants further testing when exploring the spatial variability in designed experiments in agriculture and using LNB, PCNM and BN with smooth-scale spatial components may provide better predictions of species effects than do other, more conventional, approaches.
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Chen, Deshen, Hongliang Qian, Huajie Wang, Wucheng Xu, and Jingfang Li. "Non-Uniform Temperature Field of Spatial Grid Structure under Construction Induced by Solar Radiation." Applied Sciences 10, no. 7 (April 3, 2020): 2445. http://dx.doi.org/10.3390/app10072445.
Повний текст джерелаАнотація:
The temperature of spatial structures under construction can have a significant non-uniform distribution induced by intense solar radiation. This temperature distribution affects the component assembly and results in closure difficulties, potentially causing safety hazards. A spatial grid structure model was designed and subjected to temperature field test under sunlight to study the temperature distribution of the structure and for comparison with numerical simulation methods. The distribution characteristics and the time-varying laws were analyzed based on the test data. Then, the ray-casting algorithm was introduced to analyze the shadow influence between members, so that the temperature distribution of the model was simulated accurately, which was verified by the test data. The results show that the spatial grid structure had an obvious non-uniform temperature distribution, with a maximum temperature rise of 16 °C when compared with ambient temperature and a maximum temperature difference between members of 11 °C. The variation laws were gained both from the test and the numerical simulation. The numerical simulation method proposed herein can be used to calculate the shadow distribution and the temperature field of the structure effectively. The research methods and conclusions can provide valuable references for thermal design, monitoring, and control of spatial grid structures.
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Bellugi, Dino G., David G. Milledge, Kurt M. Cuffey, William E. Dietrich, and Laurel G. Larsen. "Controls on the size distributions of shallow landslides." Proceedings of the National Academy of Sciences 118, no. 9 (February 26, 2021): e2021855118. http://dx.doi.org/10.1073/pnas.2021855118.
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Rainfall-triggered shallow landslides are destructive hazards and play an important role in landscape processes. A theory explaining the size distributions of such features remains elusive. Prior work connects size distributions to topography, but field-mapped inventories reveal pronounced similarities in the form, mode, and spread of distributions from diverse landscapes. We analyze nearly identical distributions occurring in the Oregon Coast Range and the English Lake District, two regions of strikingly different topography, lithology, and vegetation. Similarity in minimum sizes at these sites is partly explained by theory that accounts for the interplay of mechanical soil strength controls resisting failure. Maximum sizes, however, are not explained by current theory. We develop a generalized framework to account for the entire size distribution by unifying a mechanistic slope stability model with a flexible spatial-statistical description for the variability of hillslope strength. Using hillslope-scale numerical experiments, we find that landslides can occur not only in individual low strength areas but also across multiple smaller patches that coalesce. We show that reproducing observed size distributions requires spatial strength variations to be strongly localized, of large amplitude, and a consequence of multiple interacting factors. Such constraints can act together with the mechanical determinants of landslide initiation to produce size distributions of broadly similar character in widely different landscapes, as found in our examples. We propose that size distributions reflect the systematic scale dependence of the spatially averaged strength. Our results highlight the critical need to constrain the form, amplitude, and wavelength of spatial variability in material strength properties of hillslopes.
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Qian, Yi Xian, Fang Rong Hu, Xiao Wei Cheng, and Li Bao Yang. "Optimum Design of Laser Encoding and Decoding on Laser Beam-Riding Guidance." Applied Mechanics and Materials 121-126 (October 2011): 1028–32. http://dx.doi.org/10.4028/www.scientific.net/amm.121-126.1028.
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Operating principle of laser beam-riding guidance was set forth. Based on the principle of spatial frequency-encoding, an optimum laser encoding mode was designed, which can transfer continuous laser into pulse laser that represents different position information. Then the mathematic model of deviation from target is built, a modified encoding pattern was presented, which is composed of two light paths crossed 90. Azimuth information of target is given in orthogonal coordinate system and deviation from target is linearity. As well as, characteristic distribution of spatial laser field is analyzed. Corresponding decoding mode was presented, by testing in 2 kilometers outdoor; experimental results demonstrated that the receiver can receive correctly the encoded signal and can decode the signal, measurement for the missdistance is feasible and all the performance parameters satisfy the demand.
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Slyunyaev, N. N., A. O. Soldatkin, and Y. V. Chugunov. "A model of the expanding plasmasphere. 2. Spatial distribution of the electric field." Radiophysics and Quantum Electronics 55, no. 3 (August 2012): 143–55. http://dx.doi.org/10.1007/s11141-012-9355-3.
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Lishev, St, A. Shivarova, and Kh Tarnev. "Spatial distribution of the wave field of the surface modes sustaining filamentary discharges." Journal of Applied Physics 103, no. 1 (January 2008): 013304. http://dx.doi.org/10.1063/1.2828150.
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Sales, Maria Clécia Gomes, Elilson Gomes de Brito Filho, Milton César Costa Campos, José Maurício da Cunha, Guilherme Abadia Silva, Elyenayra Nogueira Pinheiro, Douglas Marcelo Pinheiro da Silva, Flávio Pereira de Oliveira, and Fernando Gomes de Souza. "Behavior of Soil Chemical Attributes in Field-Forest Succession in Southern Amazonas." Journal of Agricultural Studies 8, no. 3 (June 4, 2020): 807. http://dx.doi.org/10.5296/jas.v8i3.16846.
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The use of geostatistical methods in the identification of the size and structure of the spatial variability of soil chemical attributes has been a very important tool in the evaluation and behavior of soil attributes. This research aimed to evaluate the spatial variability of chemical attributes in natural field and forest areas, in the Humaitá region (AM). In these areas, meshes with dimensions of 70 m x 70 m were established at regular intervals of 10 minutes in the 0.0-0.2 m layers, totaling 64 samples per layer. It was determined: soil pH, phosphorus (P), potassium (K+), calcium (Ca2+), magnesium (Mg2+), aluminum (Al3+) and potential acidity (H++Al3+). Base saturation (V%) and sum of bases (SB) were calculated. The data were evaluated by descriptive statistics and spatial dependence analysis, based on the best models and semivariograms adjustment. The chemical attributes are spatially dependent, they present random distribution of ideal sample spacing, considering that the variables that showed dependence were adjusted to the exponential and spherical model. Geostatistic was presented as an appropriate tool, providing information that allows the understanding of the spatial distribution. The degree of dependence was strong and moderate. The highest reaches were recorded in the natural field area.
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Brown, P. E., O. F. Christensen, H. E. Clough, P. J. Diggle, C. A. Hart, S. Hazel, R. Kemp, et al. "Frequency and Spatial Distribution of Environmental Campylobacter spp." Applied and Environmental Microbiology 70, no. 11 (November 2004): 6501–11. http://dx.doi.org/10.1128/aem.70.11.6501-6511.2004.
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ABSTRACT Humans are exposed to Campylobacter spp. in a range of sources via both food and environmental pathways. For this study, we explored the frequency and distribution of thermophilic Campylobacter spp. in a 10- by 10-km square rural area of Cheshire, United Kingdom. The area contains approximately 70, mainly dairy, farms and is used extensively for outdoor recreational activities. Campylobacter spp. were isolated from a range of environmental samples by use of a systematic sampling grid. Livestock (mainly cattle) and wildlife feces and environmental water and soil samples were cultured, and isolates were presumptively identified by standard techniques. These isolates were further characterized by PCR. Campylobacter jejuni was the most prevalent species in all animal samples, ranging from 11% in samples from nonavian wildlife to 36% in cattle feces, and was isolated from 15% of water samples. Campylobacter coli was commonly found in water (17%) and sheep (21%) samples, but rarely in other samples. Campylobacter lari was recovered from all sample types, with the exception of sheep feces, and was found in moderate numbers in birds (7%) and water (5%). Campylobacter hyointestinalis was only recovered from cattle (7%) and birds (1%). The spatial distribution and determinants of C. jejuni in cattle feces were examined by the use of model-based spatial statistics. The distribution was consistent with very localized within-farm or within-field transmission and showed little evidence of any larger-scale spatial dependence. We concluded that there is a potentially high risk of human exposure to Campylobacter spp., particularly C. jejuni, in the environment of our study area. The prevalence and likely risk posed by C. jejuni-positive cattle feces in the environment diminished as the fecal material aged. After we took into account the age of the fecal material, the absence or presence of rain, and the presence of bird feces, there was evidence of significant variation in the prevalence of C. jejuni-positive cattle feces between grazing fields but no evidence of spatial clustering beyond this resolution. The spatial pattern of C. jejuni is therefore consistent with that for an organism that is ubiquitous in areas contaminated with cattle feces, with a short-scale variation in infection intensity that cannot be explained solely by variations in the age of the fecal material. The observed pattern is not consistent with large-scale transmission attributable to watercourses, wildlife territories, or other geographical features that transcend field and farm boundaries.
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Mustafic, Sanja. "Spatial distribution of runoff in Temstica river basin." Glasnik Srpskog geografskog drustva 86, no. 2 (2006): 45–52. http://dx.doi.org/10.2298/gsgd0602045m.
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The values of specific runoff are defined by model of multi factorial analyses combined with method of "grid" system. Elemental unit is presented by unit field of 0.5 x 0.5 km. Such multi regression model of high statistical significance enables analyses of specific runoff from many aspects. First aspect is establishing the amount and distribution of water for every altitude zone in total runoff creating. Second is presented in its altitude distribution in dependence of altitude existing of some lithologic-hydrologic complex; at the and from aspect from spatial regionalization it is possible to perceive water distribution within the river basin. By that we could realize water condition of some differential and contrast areas. Application of above mentioned methods as well as processing of each relevant parameter for studying these kinds of problems are carried out in GEOMEDIA program.
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Yan, Manjun, and Long Ma. "Generation of Higher-Order Hermite–Gaussian Modes via Cascaded Phase-Only Spatial Light Modulators." Mathematics 10, no. 10 (May 11, 2022): 1631. http://dx.doi.org/10.3390/math10101631.
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The spatial distribution of higher-order Hermite–Gaussian (HG) modes is more complicated than the fundamental mode, and the characteristics of different modes and their orthogonal characteristics have essential applications in the fields of measurement, imaging, and large-capacity communications. The main issue in future applications is how to efficiently generate higher-order HG modes. The spatial light modulator has high spatial resolution and excellent maneuverability, so it is a simple and effective way to generate higher-order HG modes. Here, the efficient generation of higher-order HG modes via cascaded spatial light modulators was experimentally investigated. For the HG90 mode, the conversion efficiency is 61%. The method with high conversion efficiency has promising application potentials in biophotonics, laser physics, and quantum information.
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Fuks, Henryk, and Anna T. Lawniczak. "Individual-based lattice model for spatial spread of epidemics." Discrete Dynamics in Nature and Society 6, no. 3 (2001): 191–200. http://dx.doi.org/10.1155/s1026022601000206.
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We present a lattice gas cellular automaton (LGCA) to study spatial and temporal dynamics of an epidemic of SIR (susceptible-infected-removed) type. The automaton is fully discrete,i.e., space, time and number of individuals are discrete variables. The automaton can be applied to study spread of epidemics in both human and animal populations. We investigate effects of spatial inhomogeneities in initial distribution of infected and vaccinated populations on the dynamics of epidemic of SIR type. We discuss vaccination strategies which differ only in spatial distribution of vaccinated individuals. Also, we derive an approximate, mean-field type description of the automaton, and discuss differences between the mean-field dynamics and the results ofLGCA simulation.
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Yan, Lei, Yanfei Li, Wei Chen, Yi Lin, Feizhou Zhang, Taixia Wu, Jouni Peltoniemi, Hongying Zhao, Siyuan Liu, and Zihan Zhang. "Temporal and Spatial Characteristics of the Global Skylight Polarization Vector Field." Remote Sensing 14, no. 9 (May 4, 2022): 2193. http://dx.doi.org/10.3390/rs14092193.
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There are two widely recognized global fields in nature: the gravity field and the geomagnetic field. Universal gravitation and Earth rotation are important sources of the Earth’s gravity and geomagnetic fields, which are well known to us. After years of long-term observation, global research, and analysis, it was discovered that we have neglected a direct incident energy of the universe on the Earth. Solar radiation, leading to energy exchange from the atmosphere 100 km above the land surface, is the energy source of the Earth. Polarization is one of the four basic physical properties of solar radiation. After the solar radiation reaches the surface of these media, it reflects, scatters or refracts, and exhibits different degrees of polarization. The polarized solar light forms the Earth–sky polarization vector field. The polarized light dispersion is expected to become a new method for global analysis of the human environment. Polarization detection is the best way to accurately explore the atmospheric effects. Local polarized skylight distribution was found in different sites in the world; however, the global distribution of the polarized sunlight radiation has never been explored. In this paper, we investigate the Global Skylight Polarization Field. This study aimed at providing new insight into the laws of polarization over our Earth. We use a Rayleigh scattering model to obtain the simulation results of the sky polarization field. Rayleigh scattering occurs when the particle size is much smaller than the wavelength of the incident electromagnetic wave. We also use a polarized fisheye camera to collect the sky polarization image and calculate the distribution pattern of the DOLP (degree of linear polarization) and AOLP (azimuth of linear polarization) of the skylight. The stability and gradual change in the degree of polarization in the zenith direction are verified, and the distribution law and daily change law of the degree of polarization in the sky are obtained. With the increase in the solar altitude angle, the degree of polarization will decrease. We also observed the skylight polarization in different weather conditions. Our results demonstrate the physical basis, characteristics, and usability of the polarization field. They show an inevitable trend from optical remote sensing to polarization remote sensing.
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Roy, Milita, Malini Kundu, Soumendranath Chatterjee, and Gautam Aditya. "Distribution of mosquito larvae in rice field habitats: a spatial scale analysis in semi-field condition." European Journal of Ecology 5, no. 1 (January 1, 2019): 38–48. http://dx.doi.org/10.2478/eje-2019-0006.
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Abstract The distribution of the mosquito larvae in the breeding habitats varies at the spatial scale depending on the availability of the resources and the predators. This proposition was assessed through the observation of the spatial distribution of Culex larvae (Culex tritaeniorhynchus) in artificially constructed rice field habitats. Using a binomial generalized linear model with logit link, the disparity in the abundance of the larvae was evaluated to justify the effects of light (light vs shade), vertical (surface vs bottom), and horizontal (wall vs center) distribution as explanatory variables. Under light availability, the spatial occupancy of the mosquito larvae was higher in the center than in the walls of the mesocosms. However, the larval orientation was higher on the surface than at the bottom of the mesocosms in all instances. In comparison to open spaces, the larval aggregation was higher in the presence of the floating vegetations like Azolla and Lemna, indicating that the habitat heterogeneity of the mesocosms influenced the distribution of the mosquito larvae in the available spaces. A reduction in the larval aggregation pattern in the spaces was observed in the presence of the predator (Anisops sp.) reflecting the possible evasion tactics of the mosquito larvae. The observations suggest that the mosquito larvae may utilize the vegetation in the rice field habitats quite effectively and occupy empty spaces of predators. The results may be considered as a prototype of the prospective localization of the mosquito larvae in the rice fields and help to frame the strategies of spraying the biopesticides to achieve optimal efficacy in mosquito regulation.
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Pearce, Tamieka L., Jason B. Scott, Frank S. Hay, and Sarah J. Pethybridge. "Mating-Type Gene Structure and Spatial Distribution of Didymella tanaceti in Pyrethrum Fields." Phytopathology® 106, no. 12 (December 2016): 1521–29. http://dx.doi.org/10.1094/phyto-01-16-0038-r.
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Tan spot of pyrethrum (Tanacetum cinerariifolium) is caused by the ascomycete Didymella tanaceti. To assess the evolutionary role of ascospores in the assumed asexual species, the structure and arrangement of mating-type (MAT) genes were examined. A single MAT1-1 or MAT1-2 idiomorph was identified in all isolates examined, indicating that the species is heterothallic. The idiomorphs were flanked upstream and downstream by regions encoding pyridoxamine phosphate oxidase-like and DNA lyase-like proteins, respectively. A multiplex MAT-specific polymerase chain reaction assay was developed and used to genotype 325 isolates collected within two transects in each of four fields in Tasmania, Australia. The ratio of isolates of each mating-type in each transect was consistent with a 1:1 ratio. The spatial distribution of the isolates of the two mating-types within each transect was random for all except one transect for MAT1-1 isolates, indicating that clonal patterns of each mating-type were absent. However, evidence of a reduced selection pressure on MAT1-1 isolates was observed, with a second haplotype of the MAT1-1-1 gene identified in 4.4% of MAT1-1 isolates. In vitro crosses between isolates with opposite mating-types failed to produce ascospores. Although the sexual morph could not be induced, the occurrence of both mating-types in equal frequencies suggested that a cryptic sexual mode of reproduction may occur within field populations.
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Bulatov, V. V., and Yu V. Vladimirov. "Asymptotics of the Far Fields of Internal Gravity Waves Excited by a Source of Radial Symmetry." Fluid Dynamics 56, no. 5 (September 2021): 672–77. http://dx.doi.org/10.1134/s0015462821050013.
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Abstract— The problem of the far field of internal gravity waves generated by a perturbation source of radial symmetry aroused at an initial instant of time is solved. The constant model distribution of the buoyancy frequency is considered and, using the Fourier–Hankel transform, an analytical solution to the problem is obtained in the form of the sum of wave modes. Asymptotics of the solutions that describe the spatial-temporal characteristics of elevation of the isopycnic lines and the vertical and horizontal velocity components far from the perturbation source are obtained. The asymptotics of the components of the wave field are expressed in terms of the square of the Airy function and its derivatives in the neighborhood of the wave fronts of an individual wave mode. The exact and asymptotic results are compared and it is shown that the asymptotic method makes it possible to calculate effectively the far wave fields at times of the order of ten and more of the Brunt–Väisälä periods.
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Hubin, Aliaksandr, Geir O. Storvik, Paul E. Grini, and Melinka A. Butenko. "A Bayesian Binomial Regression Model with Latent Gaussian Processes for Modelling DNA Methylation." Austrian Journal of Statistics 49, no. 4 (April 13, 2020): 46–56. http://dx.doi.org/10.17713/ajs.v49i4.1124.
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Epigenetic observations are represented by the total number of reads from a given pool of cells and the number of methylated reads, making it reasonable to model this data by a binomial distribution. There are numerous factors that can influence the probability of success in a particular region. Moreover, there is a strong spatial (alongside the genome) dependence of these probabilities. We incorporate dependence on the covariates and the spatial dependence of the methylation probability for observations from a pool of cells by means of a binomial regression model with a latent Gaussian field and a logit link function. We apply a Bayesian approach including prior specifications on model configurations. We run a mode jumping Markov chain Monte Carlo algorithm (MJMCMC) across different choices of covariates in order to obtain the joint posterior distribution of parameters and models. This also allows finding the best set of covariates to model methylation probability within the genomic region of interest and individual marginal inclusion probabilities of the covariates.
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Le, Thai-Hoa, and Dong-Anh Nguyen. "TEMPORO-SPECTRAL COHERENT STRUCTURE OF TURBULENCE AND PRESSURE USING FOURIER AND WAVELET TRANSFORMS." ASEAN Journal on Science and Technology for Development 25, no. 2 (November 22, 2017): 405–17. http://dx.doi.org/10.29037/ajstd.271.
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Studying the spatial distribution in coherent fields such as turbulent and turbulent-induced force ones is important to model and evaluate turbulent-induced forces and response of structures on the turbulent flows. Turbulent field-based coherent function is commonly used for the spatial distribution characteristic of induced forces in the frequency domain. This paper will focus to study spectral coherent structure of turbulence and forces in not only the frequency domain using conventional Fourier transform-based coherence, but also temporo-spectral coherent one in the time-frequency plane thanks to wavelet transform-based coherence for more understanding of the turbulence and force coherences and their spatial distributions. Effects of spanwise separations, bluff body flow and flow conditions on coherent structures of turbulence and induced pressure, comparison between turbulence and pressure coherences as well as intermittency of coherent structure in the time-frequency plane will be investigated here.
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Cardina, John, Denise H. Sparrow, and Edward L. McCoy. "Analysis of Spatial Distribution of Common Lambsquarters (Chenopodium album) in No-Till Soybean (Glycine max)." Weed Science 43, no. 2 (June 1995): 258–68. http://dx.doi.org/10.1017/s0043174500081157.
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The nonuniform spatial distribution of weeds complicates sampling, modeling, and management of weed populations. Principles of a rational approach to analysis of weed spatial distribution, combining classical and spatial statistics, are presented using data for cumulative emergence of common lambsquarters in no-tillage soybean fields in 1990 and 1993. Classical statistics, dispersion indices, mean/variance relationships, and frequency histograms confirmed that raw and loge-transformed data were not normally distributed, that populations were aggregated, and that large-scale trends in population means violated assumptions of spatial statistics. Detrending was accomplished by median polishing loge-transformed data and confirmed by evaluation of standardized residuals and frequency histograms. Detrended residuals were used to construct omni-directional and uni-directional semivariograms to describe the spatial structure of the populations. A spherical model fit to the data was verified by cross validation. Semivariograms showed that common lambsquarters density was spatially autocorrelated at distances to 16 m, with more than 30% of the variance in density due to distance between field locations. Comparisons of kriged estimates and their standard deviations with and without detrending indicated that estimates using detrended data were more appropriate and more precise. Kriged estimates of common lambsquarters density were used to draw contour maps of the populations.
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Krapp, Holger G., and Fabrizio Gabbiani. "Spatial Distribution of Inputs and Local Receptive Field Properties of a Wide-Field, Looming Sensitive Neuron." Journal of Neurophysiology 93, no. 4 (April 2005): 2240–53. http://dx.doi.org/10.1152/jn.00965.2004.
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The lobula giant movement detector (LGMD) in the locust visual system and its target neuron, the descending contralateral movement detector (DCMD), respond to approaching objects looming on a collision course with the animal. They thus provide a good model to study the cellular and network mechanisms underlying the sensitivity to this specific class of behaviorally relevant stimuli. We determined over an entire locust eye the density distribution of optical axes describing the spatial organization of local inputs to the visual system and compared it with the sensitivity distribution of the LGMD/DCMD to local motion stimuli. The density of optical axes peaks in the equatorial region of the frontal eye. Local motion sensitivity, however, peaks in the equatorial region of the caudolateral visual field and only correlates positively with the dorso-ventral density of optical axes. On local stimulation, both the velocity tuning and the response latency of the LGMD/DCMD depend on stimulus position within the visual field. Spatial and temporal integration experiments in which several local motion stimuli were activated either simultaneously or at fixed delays reveal that the LGMD processes local motion in a strongly sublinear way. Thus the neuron's integration properties seem to depend on several factors including its dendritic morphology, the local characteristics of afferent fiber inputs, and inhibition mediated by different pathways or by voltage-gated conductances. Our study shows that the selectivity of this looming sensitive neuron to approaching objects relies on more complex biophysical mechanisms than previously thought.
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Jiang, Ning, Wen-Jin Yao, Wen-Bin Li, Wei-Hang Li, and Da-Cheng Gao. "Dynamic Multiprojectile Attack and Killing Effects of Detonation Warheads." Shock and Vibration 2022 (March 20, 2022): 1–13. http://dx.doi.org/10.1155/2022/1701416.
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Dynamic spatial distribution and killing characteristics of warhead fragments are important topics in the field of weapon effectiveness and protection. However, there is little research on the fragment distribution formed by continuous dynamic attacks of multiple projectiles that explode above the ground. This study analyzes spatial distributions of warhead fragments using witness boards in a rectangular target test. The results show that the fragment distribution of multiple projectiles in continuous dynamic attacks demonstrates a spatial superposition characteristic. The superimposed distribution is the sum of the distributions of two independent fragment distributions. The distribution characteristics are consistent with fragment scattering behavior. Therefore, they can be used to analyze the killing effects of multiple projectiles conveniently. The effects of falling speed, falling angle, and explosion height on the damage range of fragments were explored by a fragment spatial distribution model obtained from experiments. Analysis indicates that the prefabricated fragment distribution conformed to a spatial superposition relationship under dynamic multiprojectile continuous attacks, and the superposition obeyed fragment scattering characteristics. As the projectile falling angle increased at the explosion center, or as the falling height decreased, the positive pressure duration increased gradually. The falling speed had the greatest impact on the specific impulse of overpressure. The falling angle had the greatest impact on the peak value of overpressure. Both the falling angle and the explosion height had the greatest impact on the positive pressure acting time.
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Khonina, Svetlana N., Alexey P. Porfirev, Sergey G. Volotovskiy, Andrey V. Ustinov, Sergey A. Fomchenkov, Vladimir S. Pavelyev, Siegmund Schröter, and Michael Duparré. "Generation of Multiple Vector Optical Bottle Beams." Photonics 8, no. 6 (June 12, 2021): 218. http://dx.doi.org/10.3390/photonics8060218.
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We propose binary diffractive optical elements, combining several axicons of different types (axis-symmetrical and spiral), for the generation of a 3D intensity distribution in the form of multiple vector optical ‘bottle’ beams, which can be tailored by a change in the polarization state of the illumination radiation. The spatial dynamics of the obtained intensity distribution with different polarization states (circular and cylindrical of various orders) were investigated in paraxial mode numerically and experimentally. The designed binary axicons were manufactured using the e-beam lithography technique. The proposed combinations of optical elements can be used for the generation of vector optical traps in the field of laser trapping and manipulation, as well as for performing the spatial transformation of the polarization state of laser radiation, which is crucial in the field of laser-matter interaction for the generation of special morphologies of laser-induced periodic surface structures.
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Chen, Youhua, Yongbin Wu, Weihua Chen, Tian Zhao, Wenyan Zhang, and Tsung-Jen Shen. "Application of a Negative Multinomial Model Gives Insight into Rarity-Area Relationships." Forests 11, no. 5 (May 20, 2020): 571. http://dx.doi.org/10.3390/f11050571.
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The distribution of individuals of different species across different sampling units is typically non-random. This distributional non-independence can be interpreted and modelled as a correlated multivariate distribution. However, this correlation cannot be modelled using a totally independent and random distribution such as the Poisson distribution. In this study, we utilized the negative multinomial distribution to overcome the problem encountered by the commonly used Poisson distribution and used it to derive insight into the implications of field sampling for rare species’ distributions. Mathematically, we derived, from the negative multinomial distribution and sampling theory, contrasting relationships between sampling area, and the proportions of locally rare and regionally rare species in ecological assemblages presenting multi-species correlated distribution. With the suggested model, we explored the cross-scale relationships between the spatial extent, the population threshold for defining the rarity of species, and the multi-species correlated distribution pattern using data from two 50-ha tropical forest plots in Barro Colorado Island (Panama) and Heishiding Provincial Reserve (Guangdong Province, China). Notably, unseen species (species with zero abundance in the studied local sample) positively contributed to the distributional non-independence of species in a local sample. We empirically confirmed these findings using the plot data. These findings can help predict rare species–area relationships at various spatial scales, potentially informing biodiversity conservation and development of optimal field sampling strategies.
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Kim, Changhwan, and Dae-Hong Kim. "Effects of Rainfall Spatial Distribution on the Relationship between Rainfall Spatiotemporal Resolution and Runoff Prediction Accuracy." Water 12, no. 3 (March 17, 2020): 846. http://dx.doi.org/10.3390/w12030846.
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We studied how rainfall spatial distribution affects the relationship between rainfall spatiotemporal resolution and runoff prediction accuracy under real field conditions. We gathered radar rainfall and discharge data for three rainfall events. These rainfall-runoff events were then reproduced using a kinematic wave model. Modeling accuracy was estimated quantitatively using the Nash–Sutcliffe model efficiency coefficient and peak discharge ratio. Normalized root-mean-square error ( nRMSE ), skewness ( S k ), and second scaled spatial moment of catchment rainfall ( δ 2 ) were employed to quantify rainfall spatial distribution characteristics. By relating the accuracy of modeling results to the rainfall spatial characteristics using various rainfall spatiotemporal resolutions, we found that the modeling results converged to a value as the nRMSE , | S k | and | 1 − δ 2 | decreased. That is, rainfall spatial distributions affect the relationship between lower limit of rainfall spatiotemporal resolution for runoff models and runoff prediction accuracy.
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Zwally, H. J., and M. B. Giovinetto. "Spatial distribution of net surface mass balance on Greenland." Annals of Glaciology 31 (2000): 126–32. http://dx.doi.org/10.3189/172756400781820318.
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AbstractThe spatial distribution of surface mass balance on the Greenland ice sheet is mapped on a 50 km grid using a combination of methods depending on a zonal characterization of the diagenetic snow fades. In the zones of dry snow and upper percolation fades, the accumulation rate is calculated from microwave emissivities derived from satellite measurements using a model that is calibrated with field accumulation data. In the lower percolation zone, accumulation rates are obtained from visual interpolation of previously compiled field data, with some modification so the balance is zero at the equilibrium line In the ablation zone, ablation rates are calculated as a function of ice-surface elevation and latitude. Average values of the surface balance are 263 kg m–2a–1 in the accumulation zone, (-) 1259 kg m–2 a–1 in the ablation zone and 1286 kg m–2 a–1 overall. Compared to the findings of a previous study using practically the same approach but different models, our bulk estimate of balance (216 Gt a–1) is 57% smaller, but the differences in the estimates of net accumulation and net ablation are, respectively, 30% and 172% larger. In this and other comparisons, there is evidence that the differences in estimates are primarily due to differences in the delineation of the equilibrium line and the estimate of ablation, and secondarily to the estimate of accumulation and interpolation of field data. The differences noted with six other estimates reported in the last two decades are all of a size close to the composite variation of the difference (±50Gtσ–1) . Our surface balance is smaller than three estimates, larger than one and in agreement with two. If substituted in the latest mass-budget estimate that indicates equilibrium, our surface balance estimate would suggest a negative budget of 55 Gt a–1 and thus a positive contribution to sea-level change of 0.15 mm a–1.
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Nelson, Robert D., Sharon R. Hasslen, and Stanley L. Erlandsen. "Application of high-resolution field-emission LVSEM, backscatter imaging, immunogold staining to definition of the spatial distributions of two human neutrophil adherence receptors." Proceedings, annual meeting, Electron Microscopy Society of America 51 (August 1, 1993): 36–37. http://dx.doi.org/10.1017/s0424820100146023.
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Receptors are commonly defined in terms of number per cell, affinity for ligand, chemical structure, mode of attachment to the cell surface, and mechanism of signal transduction. We propose to show that knowledge of spatial distribution of receptors on the cell surface can provide additional clues to their function and components of functional control.L-selectin and Mac-1 denote two receptor populations on the neutrophil surface that mediate neutrophil-endothelial cell adherence interactions and provide for targeting of neutrophil recruitment to sites of inflammation. We have studied the spatial distributions of these receptors using LVSEM and backscatter imaging of isolated human neutrophils stained with mouse anti-receptor (primary) antibody and goat anti-mouse (secondary) antibody conjugated to 12 nm colloidal gold. This combination of techniques provides for three-dimensional analysis of the expression of these receptors on different surface membrane domains of the neutrophil: the ruffles and microvilli that project from the cell surface, and the cell body between these projecting structures.
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Méndez-Giono, J. A., T. Minea, T. Thuillier, and A. Revel. "Self-consistent Monte Carlo model for ECRIS plasma simulation." Journal of Physics: Conference Series 2244, no. 1 (April 1, 2022): 012027. http://dx.doi.org/10.1088/1742-6596/2244/1/012027.
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Abstract A self-consistent iterative Monte Carlo model to simulate electron cyclotron resonance ion source (ECRIS) plasma is presented. It computes the species’ spatial and energy distribution in the whole plasma chamber in a three-dimensional mesh. A number of electrons and ions are propagated independently considering the static magnetic field, injected microwave field and local electrical potential field. The species trajectories populate the mesh allowing to compute their local density and velocity. Each species is pushed until it undergoes a destructive collision or after a fixed time limit. After each propagation phase, the local plasma potential and the heating electromagnetic microwave field are updated. This process is then iterated until convergence of species distributions and fields is reached. This method is intended to be a faster alternative to other methods to characterise the species distributions in the plasma for a specified ECRIS design and aid with their conception. The model and software development status are presented, along with prospects.
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Haueisen, J., L. Arendt-Nielsen, A. CN Chen, F. Zanow, and M. Gratkowski. "Decomposition of Biomedical Signals in Spatial and Time-frequency Modes." Methods of Information in Medicine 47, no. 01 (2008): 26–37. http://dx.doi.org/10.3414/me0355.
Повний текст джерелаАнотація:
Summary Objectives: The purpose of this paper is to introduce a new method for spatial-time-frequency analysis of multichannel biomedical data. We exemplify the method for data recorded with a 31-channel Philips biomagnetometer. Methods: The method creates approximations and decompositions of spatiotemporal signal distributions using elements (atoms) chosen from a very large and redundant set (dictionary). The method is based on the Matching Pursuit algorithm, but it uses atoms that are distributed both in time and space (instead of only time-distributed atoms in standard Matching Pursuit). The time-frequency distribution of signal components is described by Gabor atoms and their spatial distribution is modeled by spatial modes. The spatial modes are created with the help of Bessel functions. Two versions of the method, differing in the definition of spatial properties of the atoms, are presented. Results: The technique was validated on simulated data and real magnetic field data. It was used for removal of powerline noise from multichannel magnetoencephalography data, extraction of high-frequency somatosensory evoked fields and for separation of partially overlapping T- and U-waves in magnetocardiography. Conclusions: The method allows for parameterization of multichannel data in the time-frequency as well as in the spatial domains. It thus can be used for signal preserving filtering simultaneously in time, frequency, and space. Applications are e.g. the elimination of artifact components, extraction of components with biological meaning, and data exploration.