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A diffusion SEIAR model with Beddington-DeAngelis type incidence is proposed to characterize the spread of COVID-19 with spatial transmission. First, the well-posedness of solution is studied. Second, the basic reproduction number \begin{document}$ \mathcal R_{0} $\end{document} is derived and served as a threshold value to determine whether COVID-19 will spread. Meanwhile, we consider the effect of diffusion on the spread of COVID-19 in spatial homogenous environment, by which we can obtain that if \begin{document}$ \mathcal R_{0} , then the infection-free steady state is globally asymptotically stable, while if \begin{document}$ \mathcal R_{0}>1 $\end{document} , then the endemic steady state is globally asymptotically stable. Furthermore, according to the official reporting data about COVID-19 in Wuhan, China, the actual value of \begin{document}$ \mathcal R_{0} $\end{document} is estimated, and comparing with other types of incidence, we find that the estimated peak with Beddington-DeAngelis type incidence is more close to the cases in reality. Finally, by numerical simulations, we can see that the diffusion behavior has evident impact on the spread of COVID-19 in spatial heterogeneity than homogeneity of environment.

This article examines the results of a contrastive empirical study of conventional indirect requests in Peninsular and Uruguayan Spanish. The results reveal pragmatic similarities at the level of the linguistic encoding of utterances with both, Peninsular and Uruguayan Spanish speakers showing a negative correlation between (in)directness and social distance. The less familiar the interlocutors are with each other, the more likely it is for their requests to be realised indirectly. On the other hand, pragmatic differences were found in the tentativeness conveyed by the requests in these two language varieties. Uruguayan Spanish requests were more tentative than those in Peninsular Spanish. This tentativeness was achieved through a more frequent and more varied use of external modifications and a much higher incidence of internal modificating devices of the downgrading type.

The aerodynamic performance of a propeller at high incidence angles, in forward flight, has long been associated with wing-like behaviors. At low to intermediate angles, thrust generally decreases ...

A spatio-temporal model for HCV dynamics incorporating the spatial mobility of viruses and immune B cells, with general nonlinear incidence functions for both modes of infection transmission, namely, virus-to-cell as well as cell-to-cell transmission, is proposed and analyzed with the homogeneous Neumann boundary conditions. In addition, the model includes the role of B cell or antibody response and considers the non-cytolytic cure of productively infected hepatocytes. The existential conditions and global stability for the system equilibrium points are examined. The analytical results shows that the three types of equilibria for the model with general incidence functions are globally asymptotically stable under certain conditions along with criteria on the basic reproductive ratio. The numerical illustration of the analytical findings are presented for the case of bilinear as well as Holling type-II incidence function in a one-dimensional spatial domain. For both the incidence functions, the model populations converge to the corresponding levels of the infected or infection-free equilibrium, contingent upon the case of the basic reproductive ratio being greater than unity or not, respectively. Furthermore, it is observed that the diffusive coefficients do not influence the asymptotic behavior of the system. The infection will be eliminated when basic reproductive ratio is less than unity.

This paper introduces Riordan-Krylov matrices. These matrices naturally generalize Riordan matrices by using Krylov matrices and a more general class of algebras in place of formal power series. Fundamental properties of Riordan-Krylov matrices that are analogous to those of Riordan matrices are developed. These results and techniques are used to study incidence algebras of a poset as well as the chain and zeta-multichain polynomials of the poset. Throughout the paper applications to enumeration problems in combinatorics and number theory are provided.

Let $X$ be a finite connected poset, $F$ a field and $I(X,F)$ the incidence algebra of $X$ over $F$. We describe the bijective linear idempotent preservers $\varphi:I(X,F)\to I(X,F)$. Namely, we prove that, whenever $\mathrm{char}(F)\ne 2$, $\varphi$ is either an automorphism or an anti-automorphism of $I(X,F)$. If $\mathrm{char}(F)=2$ and $|F|>2$, then $\varphi$ is a (in general, non-proper) Lie automorphism of $I(X,F)$. Finally, if $F=\mathbb{Z}_2$, then $\varphi$ is the composition of a bijective shift map and a Lie automorphism of $I(X,F)$. Under certain restrictions on the characteristic of $F$ we also obtain descriptions of the bijective linear maps which preserve tripotents and, more generally, $k$-potents of $I(X,F)$ for $k\ge 3$., Comment: Final version published in Linear Algebra and its Applications

In this work, the maximum theoretical hydrodynamic efficiency of an onshore Oscillating Water Column (OWC) device is investigated in relation to the incidence angle of the wave and the configuration of the chamber. Linearized water wave theory is used, and the full solution of the associated boundary value problem (BVP) is achieved by using the simple matched eigenfunction expansion method (EEM) and the boundary element method (BEM) with second-order elements. This study is novel in using these techniques to address the influence of oblique water waves on the efficiency of an OWC with a thick front barrier. The hydrodynamic efficiency is analyzed for different directions of wave incidence and OWC chamber geometrical configurations. The semi-analytical and numerical approaches were found to be in good agreement with cases published in the specialized literature. The results show that both a thick front wall and a large incidence angle of the wave can significantly narrow the hydrodynamic efficiency band and modify the resonant frequency.

The well-known clinical axiom declaring that 'common things are common' attests to the pivotal role of probability in diagnosis. Despite the popularity of this and related axioms, there is no operationalized definition of a common disease, and no practicable way of incorporating actual disease frequencies into differential diagnosis. In this essay, we aim to disambiguate the definition of a common (or rare) disease and show that incidence-not prevalence-is the proper metric of disease frequency for differential diagnosis. We explore how numerical estimates of disease frequencies based on incidence can be incorporated into differential diagnosis as well as the inherent limitations of this method. These concepts have important implications for diagnostic decision making and medical education, and hold promise as a method to improve diagnostic accuracy.

The spread of worm virus has brought great loss to our production and life. In this paper, a new Vulnerable-Exposed-Infectious-Quarantined-Secured (VEIQS) worm propagation model with a saturated incidence and two delays is proposed. The local stability of the worm-existence equilibrium and the occurrence of Hopf bifurcation at the critical values of the two delays are obtained by regarding different combinations of time delays as bifurcation parameters. It shows that the model is ideal stable when the time delay is below the critical value and a Hopf bifurcation occurs when the time delay is above the critical value. In particular, direction and stability of the Hopf bifurcation are determined by using the center manifold theorem. Finally, some numerical simulations are presented in order to verify the analytical results.

Let [Formula: see text] denote the incidence algebra of a locally finite poset [Formula: see text] over a field [Formula: see text] and [Formula: see text] some equivalence relation on the set of generators of [Formula: see text]. Then [Formula: see text] is the subset of [Formula: see text] of all the elements that are constant on the equivalence classes of [Formula: see text]. If [Formula: see text] satisfies certain conditions, then [Formula: see text] is a subalgebra of [Formula: see text] called a reduced incidence algebra. We extend this notion to finitary incidence algebras [Formula: see text] for any poset [Formula: see text]. We investigate reduced finitary incidence algebras [Formula: see text] and determine their automorphisms in some special cases.

The last two decades have witnessed rapid developments and increasing interest in use of (1) genetic methods to estimate effective population size (Ne) and (2) close-kin mark-recapture (CKMR) methods to estimate abundance based on the incidence of close relatives. Whereas Ne-estimation methods have been applied to a wide range of taxa, all CKMR applications to date have been for aquatic species. These two fields of inquiry have developed largely independently, and this is unfortunate because deepest insights can be gained by joint evaluation of eco-evolutionary processes. In this synthesis, we outline factors (life-history traits; experimental design; stochasticity; ancillary information) that should be considered in identifying good candidate species and determining sampling/analytical regimes that can produce meaningful estimates. We show that the Ne/N ratio and the probability of a close-kin match both depend on a vector of parental weights that specify relative probabilities that different individuals will produce offspring. Although age-specific vital rates are central to both methodologies, for CKMR they are nuisance parameters that can bias abundance estimates unless properly accounted for, whereas they represent the signals of genetic drift that Ne estimation methods depend on. The most robust implementations of CKMR incorporate information from both parent-offspring pairs and siblings into a single, overarching framework, within which all demographic parameters can be jointly estimated in a way that allows coherent statements about uncertainty. Coordinating Ne and CKMR estimation methods using the same or overlapping datasets would facilitate joint evaluation of both the ecological and evolutionary consequences of abundance.

In this letter, the reflection elements based on artificial dielectric layers (ADLs) are proposed for broadband wide-angle bistatic radar cross section (RCS) reduction. ADLs are introduced to improve the interference cancellation bandwidth of the reflection elements, and avoid the dilemma of mixing multiple dielectric mediums. The reflection elements achieve an approximate 180° phase difference over the frequency range of 4.8–17.5 GHz (113.9%) under normal incidence, and the bandwidth under TE 40° incidence and TM 55° is 113.9% and 100%, respectively. To validate this design, a coding scatterer surface is simulated and fabricated. Measured results show that the proposed coding scatterer surface achieves a 10 dB bistatic RCS reduction from 5 to 17.5 GHz under normal incidence for both polarizations. Bistatic RCS reduction under oblique incidence is analyzed and presented as well.

Given a bipartite graph G = ( V 1 , V 2 , E ) , a biclique of G is a complete bipartite subgraph of G , and a biclique partitioning of G is a set A ⊆ E such that the bipartite graph G ′ = ( V 1 , V 2 , A ) is a vertex-disjoint union of bicliques. The biclique partitioning problem (BPP) consists of, given a complete bipartite graph G = ( V 1 , V 2 , E ) with edge weights w e ∈ R for all e ∈ E (thus, negative weights are allowed), finding a biclique partitioning A ⊆ E of minimum weight. The bicluster editing problem (BEP) is a variant of the BPP and consists of editing a minimum number of edges of an input bipartite graph G in order to transform its edge set into a biclique partitioning. Editing an edge consists of either adding it to the graph or deleting it from the graph. In addition to the BPP and the BEP, other problems in the literature aim at finding biclique partitionings, and this motivates the study of the biclique partitioning polytope P n m of the complete bipartite graph K n m (i.e., P n m is the convex hull of the incidence vectors of the biclique partitionings of K n m ). In this paper we develop such a polyhedral study and show that ladder, bellows, and grid inequalities induce facets of P n m . Our computational results show that these inequalities are very effective in solving the BEP. In particular, they are able to improve the value of the relaxed solution by up to 20%.

The optical analysis of Linear Fresnel Reflectors solar concentrators deals with the calculation of the absorbed flux at the receiver. Due to concentrator discrete and complex geometry ray tracing numerical simulations is the main used method, in parallel with some analytical approaches that have been developed for specific cases. This paper presents an analytical method for Linear Fresnel Reflectors with a flat receiver. It is based on Zhu’s vector-based method and Rabl’s concepts of acceptance and effective source, although new shading (including receiver shading), blocking, and cosine losses analyzes are presented, with the inclusion of end-losses effect. As shown, the problem is better described by the concept of intercept factor, the effective aperture area used to collect the incident sunlight. Comparison tests with ray tracing simulations performed in SolTrace for three different effective sources were carried out to validate the analytical model for both factorized and biaxial models of the intercept factor, including energetic evaluations for Evora, Portugal. In general, analytical results do agree very well with ray tracing, better for the factorized model than the biaxial. Errors in the analytical estimative of intercept factor can be high up to 132% for the biaxial model at high longitudinal incidence angles; on the other hand, errors in the amount of annual absorbed energy were high up to only 3%.

Banzhaf (Rutgers Law Rev 19:317–343, 1965) shows by citing a few examples that distortion in the bargaining power of the legislators may exist in the legislative body under weighted voting rules. Such a distortion leads to the incidence of unequal voting power of the citizens. In this paper, we investigate whether the distortion in the bargaining power is confined to a few weighted voting rules or is a general phenomenon. We show if the number of dominant political views (parties) present in a country is at most four, then there exists no weighted voting rule such that the distortion in the bargaining power can be avoided.

The complex aerodynamics of a propeller at incidence involve multiple asymmetric flow conditions around the disk, with each originating from different physical phenomena. These asymmetries give ris...

As the generalization of the digraph, the directed hypergraph (dihypergraph), denoted by $${H}$$ , is considered in this paper. First, we introduce the notions of the zeta function of $${H}$$ and dihypergraph coverings over $${H}$$ . Next, several expressions for the zeta function of $${H}$$ are given, and all dihypergraph coverings over $${H}$$ are generated by permutation voltage assignments on the incidence bipartite digraph or the edge-colored digraph of $${H}$$ . Final, we derive two explicit decomposition formulae for the zeta function of any dihypergraph covering $$\overline{{H}}$$ over $${H}$$ , which turn out that the zeta function of $${H}$$ divides the zeta function of $$\overline{{H}}$$ .

Developing small-angle neutron scattering techniques at compact accelerator-driven neutron sources (CANS) is of great importance for expanding the user community and advancing CANS capability. At the Compact Pulsed Hadron Source (CPHS) at Tsinghua University, neutron-focusing mirrors are under intensive research to address the challenge. A grazing-incidence focusing SANS (gif-SANS) project is initialized. It employs a nested supermirror assembly with a large collecting area to achieve ⩾ 10 5 n/s neutron intensity at Q min ⩽ 0.007 Å − 1 . It will equip two detectors, one being a 3He detector for normal Q-range measurements, and the other being a high-resolution detector for extending the Q min down to 10 − 3 Å − 1 . In this work, we present the conceptual design of the gif-SANS at CPHS. Such a scheme is conducive to enable high-performance SANS measurements at CANS.

The study of structure-property relations including the transformations of molecules is of utmost importance in correlations with corresponding physicochemical properties. The graph topological indices have been used effectively for such study and, in particular, bond-based indices play a vital role. The bond-additive topological indices of a molecular graph are defined as a sum of edge measures over all edges in which edge measures can be computed based on degrees, closeness, peripherality, and irregularity. In this study, we provide the mathematical characterization of the transformation of a structure that can be accomplished by the novel edge adjacency and incidence relations. We derive the exact expressions of bond type indices such as second Zagreb, sigma indices, and their coindices of total transformation and two types of semitransformations of the molecules which in turn can be used to characterize the topochemical and topostructural properties.

We establish a formalism for working with incidence algebras of posets with symmetries, and we develop equivariant Kazhdan-Lusztig-Stanley theory within this formalism. This gives a new way of thinking about the equivariant Kazhdan-Lusztig polynomial and equivariant Z-polynomial of a matroid.

Using multidimensional particle-in-cell simulations, we show that an electron beam with a huge space charge can be accelerated to high energies by irradiating the edge of a solid density target with an intense femtosecond laser pulse at parallel incidence. The process of energy gain of each electron is divided into two parts: the transverse laser field and the longitudinal field of the excited surface plasma wave (SPW). It is shown that the longitudinal field of the SPW dominates the acceleration of the major part of electrons. This process leads to generation of a highly collimated electron beam with a huge space charge.

Given a monomial $m$ in a polynomial ring and a subset $L$ of the variables of the polynomial ring, the principal $L$-Borel ideal generated by $m$ is the ideal generated by all monomials which can be obtained from $m$ by successively replacing variables of $m$ by those which are in $L$ and have smaller index. Given a collection $\mathcal{I}=\{I_1,\ldots,I_r\}$ where $I_i$ is $L_i$-Borel for $i=1,\ldots,r$ (where the subsets $L_1,\ldots,L_r$ may be different for each ideal), we prove in essence that if the bipartite incidence graph among the subsets $L_1,\ldots,L_r$ is chordal bipartite, then the defining equations of the multi-Rees algebra of $\mathcal{I}$ has a Gr\"obner basis of quadrics with squarefree lead terms under lexicographic order. Thus the multi-Rees algebra of such a collection of ideals is Koszul, Cohen-Macaulay, and normal. This significantly generalizes a theorem of Ohsugi and Hibi on Koszul bipartite graphs. As a corollary we obtain that the multi-Rees algebra of a collection of principal Borel ideals is Koszul. To prove our main result we use a fiber-wise Gr\"obner basis criterion for the kernel of a toric map and we introduce a modification of Sturmfels' sorting algorithm., Comment: 29 pages, 4 figures

Purpose: The ionospheric channel is widely used for the communication, radio navigation, radar, direction finding, radio astronomy, and remote radio probing systems. The radio channel parameters are characterized by nonstationarity due to the dynamic processes in the ionosphere, and therefore their study is one of the topical problems of space radio physics and earth-space radio physics of geospace. This work aims at presenting the results of synthesis of temporal variations in the Doppler spectra obtained by the Doppler probing of the ionosphere at vertical and quasi-vertical incidence. Design/methotology/approach: One of the most effective methods of ionosphere research is the Doppler sounding technique. It has a high time resolution (about 10 s), a Doppler shift resolution (0.01–0.1 Hz), and the accuracy of Doppler shift measurements (~0.01 Hz) that permits monitoring the variations in the ionospheric electron density (10–4–10–3) or the study of the ionospheric plasma motion with the speed of 0.1-1 m/s and greater. The solution of the inverse radio physical problem, consisting in determination of the ionosphere parameters, often means solving the direct radio physical problem. In the Doppler sounding technique, it belongs with the construction of variations in Doppler spectra and comparing them with the Doppler spectra measurements. Findings: For the radio wave ordinary component, three echoes being produced by three rays are observed. Influence of the geomagnetic fi eld and large horizontal gradients in the electron density of δ≥10 % give rise to complex ray structures with caustic surfaces. The ionospheric disturbances traveling along the magnetic meridian form the skip zones. The longitudinal and transverse displacement of the ray reflection point attains a few tens of kilometers along the vil. Haidary to vil. Hrakove quasi-vertical radiowave propagation path, for which the great circle range is 50 km. For the vertical incidence, the signal azimuth at the receiver coincides with the traveling ionospheric disturbance azimuth. The synthesis of temporal variations in the HF Doppler spectra has been made and compared with the temporal variations in the Doppler spectra recorded with the V. N. Karazin Kharkiv National University radar. The estimate of δ=15 % obtained confirms the existence of large horizontal gradients in electron density. Conclusions: Temporal variations in Doppler spectra and in azimuth have been calculated for the vertical and quasi-vertical incidence with allowance for large horizontal gradients of the electron density caused by traveling ionospheric disturbances. Key words: ionosphere, Doppler sounding at oblique incidence, synthesis of temporal variations in HF Doppler spectra, traveling ionospheric disturbances, electron density

A high-coverage algorithm termed enhanced camera assisted received signal strength ratio (eCA-RSSR) positioning algorithm is proposed for visible light positioning (VLP) systems. The basic idea of eCA-RSSR is to utilize visual information captured by the camera to estimate first the incidence angles of visible lights. Based on the incidence angles, eCA-RSSR utilizes the received signal strength ratio (RSSR) calculated by the photodiode (PD) to estimate the ratios of the distances between the LEDs and the receiver. Based on an Euclidean plane geometry theorem, eCA-RSSR transforms the ratios of the distances into the absolute values. In this way, eCA-RSSR only requires three LEDs for both orientation-free 2D and 3D positioning, implying that eCA-RSSR can achieve high coverage. Based on the absolute values of the distances, the linear least square method is employed to estimate the position of the receiver. Therefore, for the receiver having a small distance between the PD and the camera, the accuracy of eCA-RSSR does not depend on the starting values of the non-linear least square method and the complexity of eCA-RSSR is low. Furthermore, since the distance between the PD and camera can significantly affect the performance of eCA-RSSR, we further propose a compensation algorithm for eCA-RSSR based on the single-view geometry. Experiment results show that positioning errors of less than five centimeters is achievable for eCA-RSSR. Simulation results show that eCA-RSSR can achieve 80th percentile accuracy of about four centimeters and can improve the coverage ratio at low cost.

This paper derives the incidence of a pollution tax in a stylized general equilibrium framework, building on previous work by Fullerton and Heutel. Using the CPI as numeraire, we show that tax incidence is a simpler problem than previously thought and that general insights can be derived without the need to restrict the parameter space. In addition, the counterintuitive possibility that an increase in the tax could increase the pollution level vanishes. The choice of the CPI as numeraire is further justified by the fact that environmental taxes, notably carbon taxes, are typically indexed on inflation.

The first purpose of this paper is to solve completely the finite field cone restriction conjecture in four dimensions with $-1$ non-square. The second is to introduce a new approach to study incidence problems via restriction theory. More precisely, using the cone restriction estimates, we will prove sharp point-sphere incidence bounds associated with complex-valued functions for sphere sets of small size. Our incidence bounds with a specific function improve significantly a result given by Cilleruelo, Iosevich, Lund, Roche-Newton, and Rudnev., Title was changed

Teleseismic full-waveform inversion has recently been applied to image subwavelength-scale lithospheric structures (typically a few tens of kilometers) by utilizing hybrid methods in which an efficient solver for the 1D background model is coupled with a full numerical solver for a small 3D target region. Among these hybrid methods, the coupling of the fre-quency–wavenumber technique with the spectral element method is one of the most com-putationally efficient ones. However, it is normally based on a single plane-wave incidence, and thus cannot synthesize secondary global phases generated at interfaces outside the target area. To remedy the situation, we propose to use a multiple plane-wave injection method to include secondary global phases in the hybrid modeling. We investigate the performance of the teleseismic full-waveform inversion based on single and multiple plane-wave incidence through an application in the western Pyrenees and compare it with previously published images and the inversion based on a global hybrid method. In addi-tion, we also test the influence of Earth’s spherical curvature on the tomographic results. Our results demonstrate that the teleseismic full-waveform inversion based on a single plane-wave incidence can reveal complex lithospheric structures similar to those imaged using a global hybrid method and is reliable for practical tomography for small regions with an aperture of a few hundred kilometers. However, neglecting the Earth’s spherical curvature and secondary phases leads to errors on the recovered amplitudes of velocity anomalies (e.g., about 2.8% difference for density and VS, and 4.2% for VP on average). These errors can be reduced by adopting a spherical mesh and injecting multiple plane waves in the frequency–wavenumber-based hybrid method. The proposed plane-wave teleseismic full-waveform inversion is promising for mapping subwavelength-scale seismic structures using high-frequency teleseismic body waves ( > 1 Hz) including coda waves recorded at large N seismic arrays. Ministry of Education (MOE) SciNet is funded by the Canada Foundation for Innovation; the Government of Ontario; Ontario Research Fund— Research Excellence; and the University of Toronto. K. W. (after January 2020) and Y. Y. are supported by the Australian Research Council Discovery Grants DP190102940. K. W. (before January 2020), X. S. (before July 2019), and Q. L. are supported by the Natural Sciences and Engineering Research Council (NSERC) Discovery Grant 487237. P. T. is supported by Singapore Ministry of Education (MOE) AcRF Tier-1 Grant 04MNP000559C230.

Identifying graphs with extremal properties is an extensively studied topic in spectral graph theory. In this paper, we study the log-concavity of a type of iteration sequence related to the $\alpha$-normal weighted incidence matrices which is presented by Lu and Man for computing the spectral radius of hypergraphs. By using results obtained about the sequence and the method of some edge operations, we will characterize completely extremal k-graphs with the smallest spectral radius among bicyclic hypergraphs with given size., Comment: 22 pages, 3 figures

This study investigated the effect solar incidence angles and irradiance intensity on two commercially available semi-transparent organic photovoltaics panels. The results of electrical measurements taken for the panels at different solar incidence angles and in sunny and overcast conditions is presented. This data is compared to diurnal data of the same panels on a frame at 30° tilt facing south. It was found that the panels behaved very differently under different solar incidence angles and irradiance conditions. Panel A had high absorption from the underside of the panel, whereas panel B did not. Panel A efficiency and fill factor values were highest under lower irradiance and panel B efficiency was highest under higher irradiance. In sunny conditions, panel A efficiencies and fill factors increased with increasing solar incidence angles, indicating a higher absorption of the panel in lower irradiance. Panel B fill factor reduced, efficiency remained constant and % transmittance reduced with increased solar incidence angles, indicating reflected irradiance increased with increasing θ. Diurnal measurements showed that for both panels, efficiency and fill factor were higher in the morning compared to the afternoon with the same incident irradiance levels, indicating an overnight recovery phenomenon.

The probabilistic characteristics of the graph of k-fold iteration of uniform random mapping are studied. Formulas for the distribution of the length of the aperiodicity segment of an arbitrary vertex with some restrictions are calculated. We obtain exact expressions for the probabilities that two arbitrary vertices belong to the same connected component, that an arbitrary vertex belongs to the preimage set of another vertex and that there exists a collision in the considered graph.

In this study, we conducted theoretical analyses and experiments related to the acoustic characteristics of the situation where sound waves are incident upon the side surfaces of a group of cylinders forming a pin-holder structure. The sound-absorption coefficient, entering its clearance between cylinders through the geometrical dimension of the clearance or the physical property of gas, was calculated. In the analytical model, the gap part of the pin-holder structure was divided into elements and approximated as a gap surrounded by two parallel planes. The characteristic impedance and propagation constant of the approximate gap were obtained and treated as one-dimensional transfer matrices; the sound-absorption coefficient was then calculated using the transfer-matrix method. The calculated value was compared to that obtained in an experiment with a sample prepared using a 3D printer; the sound-absorption coefficient was measured using a 2-microphone impedance-measuring tube. We attempted to make a simple yet accurate estimation of sound-absorption coefficient using these procedures. Our theoretical values displayed a similar tendency to that obtained by experiment.

In this research article, we initiate the novel idea of picture fuzzy incidence graphs (PFIGs). We explain some innovative notions comprising of picture fuzzy cut-vertices, picture fuzzy bridges, picture fuzzy incidence cutpairs, and picture fuzzy incidence cut-vertices. Some rudimentary theorems and essential results are also examined in the PFIGs. Further, we determine the different concepts together with the order, size, and certain kinds of degrees in PFIG. A new type of PFIGs namely, complete picture fuzzy incidence graphs (CPFIGs) and complement of (PFIGs) are also furnished. A comparative analysis of PFIGs with fuzzy incidence graphs is also presented. Finally, an application of PFIGs in the control of illegal transportation of people from India to America is provided

By using elementary linear algebra methods we exploit properties of the incidence map of certain incidence structures with finite block sizes. We give new and simple proofs of theorems of Kantor and Lehrer, and their infinitary version. Similar results are obtained also for diagrams geometries. By mean of an extension of Block’s Lemma on the number of orbits of an automorphism group of an incidence structure, we give informations on the number of orbits of: a permutation group (of possible infinite degree) on subsets of finite size; a collineation group of a projective and affine space (of possible infinite dimension) over a finite field on subspaces of finite dimension; a group of isometries of a classical polar space (of possible infinite rank) over a finite field on totally isotropic subspaces (or singular in case of orthogonal spaces) of finite dimension. Furthermore, when the structure is finite and the associated incidence matrix has full rank, we give an alternative proof of a result of Camina and Siemons. We then deduce that certain families of incidence structures have no sharply transitive sets of automorphisms acting on blocks.

In this work, two typical interfaces are established for the antisymmetric plate wave by introducing linear defect in between phononic crystals with opposite valley Hall phases. The evolution of projected curves is demonstrated as the defect width increases, which magnifies the occurrence of multiple edge states on both interfaces. The mapping of transmission coefficient is obtained upon the incidence of transversely symmetric and antisymmetric sources, respectively. It is shown that the first edge state contains only symmetric or antisymmetric component regardless the defect width modulation, while other edge states contain both components. When void cavity occurs on the interfaces, the mapping of transmission coefficient shows that the first edge state is topologically protected and its transverse symmetry or antisymmetry is almost unperturbed by the void cavity, while other edge states do not perform the same way. Our work provides useful guidance for the design of topological edge states, and bridges the topological edge states and linear defect modes on the same interface.

Social deficits are a common feature in individuals with low incidence disabilities. Current solutions used to teach social skills are not always effective, especially when it comes to generalizing these skills to novel contexts. General case programming (GCP) is an instructional methodology founded on the science-based tenets of Direct Instruction, designed to clearly communicate the multiple contexts and response variations a learner is likely to encounter in their complex social environments. The purpose of this article is to describe how GCP can be utilized to help program for generalization of social skills.

We give a full description of the Poisson structures on the finitary incidence algebra F I ( P , R ) of an arbitrary poset P over a commutative unital ring R.

The dissipation theorem is applied to fully developed turbulent flow past a flat plate. Most of the velocity profile occurs in a thin layer near the surface, but a layer of turbulence (represented by the eddy viscosity) extends substantially farther into the fluid.

An incidence of a graph G is a vertex-edge pair ( v , e ) such that the vertex v is incident with the edge e. A proper incidence k-coloring of a graph is a coloring of its incidences involving k colors so that two incidences ( u , e ) and ( w , f ) receive distinct colors if and only if u = w , or e = f , or u w ∈ { e , f } . In this paper, we present some idea of using the incidence coloring to model a kind of multi-frequency assignment problem, in which each transceiver can be simultaneously in both sending and receiving modes, and then establish some theoretical and algorithmic aspects of the incidence coloring. Specifically, we conjecture that if G is the Mycielskian of some graph then it has a proper incidence ( Δ ( G ) + 2 ) -coloring. Actually, our conjecture is motivated by the “ ( Δ + 2 ) conjecture” of Brualdi and Quinn Massey in 1993, which states that every graph G has a proper incidence ( Δ ( G ) + 2 ) -coloring, and was disproved in 1997 by Guiduli, who pointed out that the Paley graphs with large maximum degree are counterexamples (yet they are all known counterexamples to the “ ( Δ + 2 ) conjecture”, and are not Mycielskians of any graph). To support our conjecture, we prove in this paper that if G is the Mycielskian of a graph H with | H | ≥ 3 Δ ( H ) + 2 , then we can construct a proper incidence ( Δ ( G ) + 1 ) -coloring of G in cubic time, and if G is the Mycielskian of an incidence ( Δ ( H ) + 1 ) -colorable graph H with | H | ≤ 2 Δ ( H ) , or the Mycielskian of an incidence ( Δ ( H ) + 2 ) -colorable graph H with | H | ≥ 2 Δ ( H ) + 1 , then G has a proper incidence ( Δ ( G ) + 2 ) -coloring. The minimum positive integer k such that the Mycielskian of a cycle or a path has a proper incidence k-coloring is also determined.

The understanding of factors that affect the dissemination of a viral infection is fundamental to help combat it. For instance, during the COVID-19 pandemic that changed the lives of people all over the world, one observes regions with different incidences of cases. One can speculate that population density might be one of the variables that affect the incidence of cases. In populous areas, such as big cities or congested urban areas, higher COVID-19 incidences could be observed than in rural regions. It is natural to think that if population density is such an important factor, then a gradient or difference in population density might lead to a diffusion process that will proceed until equilibrium is reached. The aim of this paper consists of the inclusion of a diffusion concept into the COVID-19 modeling. With this concept, one covers a gradient-driven transfer of the infection next to epidemic growth models (SIR-type models). This is discussed for a certain period of the German situation based on the quite different incidence data for the different federal states of Germany. With this ansatz, some phenomena of the actual development of the pandemic are found to be confirmed. The model provides a possibility to investigate certain scenarios, such as border-crossings or local spreading events, and their influence on the COVID-19 propagation. The resulting information can be a basis for the decisions of politicians and medical persons in charge of managing a pandemic.

Objectives. Previous research has shown that the acquisition of personal pronouns benefits from input with higher amounts of stable reference. This paper aims to provide more evidence of how input is structured. The language under study is Slovak, a pro-drop language, allowing to extend the study of input to verb marking. Participants and setting. The longitudinal study follows speech directed to three children in two families from the age 1;9 to 3;0. Hypotheses. It was hypothesised that the incidence of the first and second person singular pronouns and verb marking as expressions with shifting reference grows with the child’s age while the incidence of proper names and category names as expressions with stable reference decreases with the child’s age. Statistical analysis. Occurrences of first and second person singular pronouns and verb marking as expressions with shifting reference as well as proper names and category names referring to the speaker and addressee as expressions with stable reference were found and analysed. Simple regression analysis testing was conducted on the data. Results. The results confirm the hypothesis, showing an increase in the first and second person singular pronouns and verb marking over time, at the expense of proper names and category names referring to the speaker and the addressee. Study limitations. The study is limited by the size of the sample.

This research analyzes the incidence and efficiency of impact deflectometry to evaluate and design the road reinforcements of a section of the central highway. For this study, a "non-destructive" methodology has been used, based on the collection, processing, and interpretation of the deflections measured on the road surface with the impact deflectometer equipment; these deflections reflect a response of the structural package under a given load, its measurement is simple, fast and "non-destructive," that is, we do not alter the structural package, and above all, we do not cause vehicular congestion as it would be with the conventional methodology. The deflections are analyzed using the back-calculation technique, which allows us to know the total Structural Number in the function of the characteristics of rigid pavement, obtaining a structural number Sn of 6.2 and 5.6 for the right and left the roadway, respectively. This research presents the results of the current condition of the road under study. It proposes a technique for calculating the Structural Number of an asphalt reinforcement on concrete from the back-calculation.

Let $$n$$ be a positive integer and $$\mathcal{R}$$ be a $$2$$ and $$n!$$ -torsion free commutative ring with unity. Let $$X$$ be a locally finite pre-ordered set. If any two directed edges in each connected component of the complete Hasse diagram $$(X,\mathfrak{D})$$ are contained in one cycle, then every $$n$$ -commuting map on the incidence algebra $$I(X,\mathcal{R})$$ is proper.

The algebraic monoid structure of an incidence algebra is investigated. We show that the multiplicative structure alone determines the algebra automorphisms of the incidence algebra. We present a formula that expresses the complexity of the incidence monoid with respect to the two sided action of its maximal torus in terms of the zeta polynomial of the poset. In addition, we characterize the finite (connected) posets whose incidence monoids have complexity $\leq 1$. Finally, we determine the covering relations of the adherence order on the incidence monoid of a star poset., Comment: The final version of this article will appear in the Semigroup Forum

Bronchopneumonia is the most common infectious disease in children, and it seriously endangers children's health. In this paper, a deep neural network combining long short-term memory (LSTM) layers and fully connected layers was proposed to predict the prevalence of bronchopneumonia in children in Chengdu based on environmental factors and previous prevalence rates. The mean square error (MSE), mean absolute error (MAE), and Pearson correlation coefficient (R) were used to detect the performance of the deep learning model. The values of MSE, MAE, and R in the test dataset are 0.0051, 0.053, and 0.846, respectively. The results show that the proposed model can accurately predict the prevalence of bronchopneumonia in children. We also compared the proposed model with three other models, namely, a fully connected (FC) layer neural network, a random forest model, and a support vector machine. The results show that the proposed model achieves better performance than the three other models by capturing time series and mitigating the lag effect.

In this paper, we consider a delayed diffusive SVEIR model with general incidence. We first establish the threshold dynamics of this model. Using a Nonstandard Finite Difference (NSFD) scheme, we then give the discretization of the continuous model. Applying Lyapunov functions, global stability of the equilibria are established. Numerical simulations are presented to validate the obtained results. The prolonged time delay can lead to the elimination of the infectiousness. Electronic Supplementary Material Supplementary material is available in the online version of this article at 10.1007/s10473-021-0421-9.

This paper presents a perfectly matched inhomogeneous receiving metasurface for line source incidence, based on the effective medium equivalency. Each building block of the inhomogeneous metasurface has effective constitutive parameters that satisfy a specific relationship dependent on the location of the line source. By doing so, the reflection from the receiving metasurface for the cylindrical wave incidence can be significantly suppressed, improving the total reception efficiency greatly. Theoretical analysis, numerical calculation, full‐wave simulations and experimental results are consistent with each other, showing promising applications in some short‐range wireless power transmission systems, where the incident wave is non‐planar.