Element Spacing Research Articles

Just In Time! Assessment of Internal Medicine Resident Point of Care Ultrasound (POCUS) Attitudes and Behaviors After Spaced Intervention at Two Residency Programs

Point of care ultrasound (POCUS) is a complex psychomotor skill that requires scaffolded support for skill acquisition. However, the effect of spaced curricular elements on learner POCUS behaviors are not clearly understood. Using a multi-site observational cross-sectional survey study, we measured resident baseline POCUS use, behaviors, and attitudes and then implemented POCUS workflow and just-in-time POCUS curricula during internal medicine resident ward rotations and assessed changes. Self-reported personal and team POCUS use and documentation habits all improved between baseline and the just-in-time teaching. Personal POCUS use correlated with team POCUS use (ρ=0.431; p<0.001) and co-resident POCUS use (ρ=0.242; p=0.035). Attending POCUS use correlated with team POCUS use (ρ=0.523; p< 0.001), but not personal use. Overall, we found moderate, but statistically significant, improvements in reported resident and team performance of POCUS and documentation habits, suggesting that just-in-time interventions may promote POCUS use. Co-learning also appears to be a key influencer for POCUS use.

Nodal auxiliary space preconditioners for mixed virtual element methods

We propose nodal auxiliary space preconditioners for facet and edge virtual elements of lowest order by deriving discrete regular decompositions on polytopal grids and generalizing the Hiptmair-Xu preconditioner to the virtual element framework. The preconditioner consists of solving a sequence of elliptic problems on the nodal virtual element space, combined with appropriate smoother steps. Under assumed regularity of the mesh, the preconditioned system is proven to have bounded spectral condition number independent of the mesh size and this is verified by numerical experiments on a sequence of polygonal meshes. Moreover, we observe numerically that the preconditioner is robust on meshes containing elements with high aspect ratios.

A Near‐Zero Index Metamaterial Lens for Reduced Complexity and High‐Performance Active Electronically Scanned Arrays

AbstractA lens consisting of an anisotropic near‐zero index metamaterial (NZIM) is introduced for improving the far‐field performance of active electronically scanned arrays (AESA). Several simulation studies demonstrate how the NZIM lens (metalens) can be functionalized to transform the embedded element pattern of an array from a typical cosinusoidal shape to a flat‐topped pattern, dramatically reducing the gain at wider angles. This corresponds to reductions in scan loss and suppression of grating lobes in the desired field of view (FOV), especially for arrays with large element spacing (i.e., sparse or thinned arrays). The metalens concept is demonstrated through several simulation studies illustrating the beam shaping capability of NZIM materials. A fabricated metalens demonstrates full suppression of grating lobes and minimal scan loss with a ±10° FOV, which is ideally suited for limited FOV applications such as geosynchronous satellite communications.

A study on color visual perception of museum exhibition space based on eye movement experiments

Color is an essential element in the exhibition space of museums, influencing people’s visual experience. To quantitatively study the relationship between color and individual visual perception in museum exhibition spaces, the study used eye-tracking technology combined with a questionnaire, exploring the relationship between color and visual perception in the exhibition environments of history museums in terms of hue, saturation, and brightness of color. Taking the Ruijin Central Revolutionary Base in Jiangxi Province as a historical display space for research, the results show that when the saturation is 69–77%, or the hue is red (0°H), the exhibited. environments have stronger color attractiveness. The study demonstrated that the first fixation duration in eye movement data significantly negatively correlates with the subject’s personal preference, comfort, pleasure, and attractiveness. Researchers can use this as an evaluation parameter for visual perception of exhibition space.

Making Quick-Build Sidewalk Extensions Accessible to Pedestrians with Vision Disabilities

Quick-build sidewalk extensions that shorten crossing distances and improve visibility between drivers and pedestrians waiting to cross the street are understood by most travelers, but wayfinding is difficult for pedestrians with vision disabilities who are unlikely to know they exist without specific familiarization. This research evaluated the effectiveness of three potential treatments for mitigating these wayfinding problems, all of which resulted in improvements in measures of wayfinding: 1) removing the detectable warning surface (DWS) from the curb ramp and installing DWS across the width of the crosswalk at the perimeter of the sidewalk extension; 2) placing a 24-inch wide strip of raised-bar tactile direction indicators with bars oriented perpendicular to the crossing direction along one side of the curb ramp and extending through the sidewalk extension to the DWS at the perimeter; and 3) placing trapezoidal tactile warning delineators (TWDs) along the edges of the crosswalk, within the sidewalk extension, to delineate the pedestrian path. A combination of moving the DWS and installing TWDs along crosswalk edges resulted in the most accurate and effective wayfinding to and through the quick-build sidewalk extension. The spacing of vertical perimeter elements (e.g., flexible posts) to ensure they were detectable by pedestrians with vision disabilities was also evaluated. Participants who traveled outside the crosswalk reliably encountered and detected at least one vertical perimeter element when the maximum separation between vertical elements was 24 inches. The perimeter was not reliably encountered and detected when the separation between vertical elements was considerably greater.

Efficient side lobe level reduction technique for planar antenna arrays

This paper presents a novel array synthesis technique based on the virtual antenna array (VAA) concept for side lobe level (SLL) reduction of uniform planar antenna arrays (UPAA). The VAA decomposes the (M×N) UPAA into vertical and horizontal uniform linear antenna arrays (V–ULAA and H–ULAA) consisting of M and N antenna elements, respectively. The V-ULAA and H-ULAA are positioned perpendicularly and closely enough apart to form a new (M+N) virtual UPAA. Consequently, the number of antenna elements is significantly reduced, which in turn minimizes the computational complexity and signal processing time required to synthesize the desired radiation pattern. Therefore, instead of reducing the SLL of the entire UPAA, we simply reduce the SLL of each ULAA using the well-known hybrid Method of Moments/Genetic Algorithm (MoM/GA) array synthesis technique, which adjusts both the excitation coefficients and element spacings to achieve low SLL. The MoM/GA results in non-uniform V-LAA and H-LAA having two non-uniform excitation vectors AV and AH, respectively, and much lower SLLs than the corresponding V-ULAA and H-ULAA. Finally, the synthesized excitation vectors AV and AH are used to synthesize either the virtual (M+N) planar antenna array (V-PAA) or the physical (M×N)PAA with more than two-fold reductions in the SLL.

Investigating spatial and temporal characteristics and elements influencing running among residents of Nanchang city in green open areas

Understanding the exercise behaviors of urban residents in green open spaces is crucial for optimizing future urban spatial planning and improving residents’ quality of life. This study provides an in-depth analysis of residents’ running behaviors across 87 green open spaces in Nanchang City. Running data collected from the exercise platform Keep, coupled with urban geographic data and field research, reveals the spatial distribution and temporal variations of running activities, including running flow, distance, time, and pace. A set of indicator systems, such as total area, landscape form index, surrounding residential land area, and road conditions, is used to analyze its relationship with the environmental elements of green open spaces. The research results show that the running flow, running distance, and running time in green open spaces in Nanchang City are significantly influenced by different objective elements, while running pace shows little correlation with these environmental elements. Specifically, the study highlights the significant impact of elements such as total area and road length, as well as the number of nearby bus stops and population density, on residents’ running behaviors in Nanchang City’s green open spaces.

Eccentric p-Summing Lipschitz Operators and Integral Inequalities on Metric Spaces and Graphs

The extension of the concept of p-summability for linear operators to the context of Lipschitz operators on metric spaces has been extensively studied in recent years. This research primarily uses the linearization of the metric space M afforded by the associated Arens–Eells space, along with the duality between M and the metric dual space M# defined by the real-valued Lipschitz functions on M. However, alternative approaches to measuring distances between sequences of elements of metric spaces (essentially involved in the definition of p-summability) exist. One approach involves considering specific subsets of the unit ball of M# for computing the distances between sequences, such as the real Lipschitz functions derived from evaluating the difference in the values of the metric from two points to a fixed point. We introduce new notions of summability for Lipschitz operators involving such functions, which are characterized by integral dominations for those operators. To show the applicability of our results, in the last part of this paper, we use the theoretical tools obtained in the first part to analyze metric graphs. In particular, we show new results on the behavior of numerical indices defined on these graphs satisfying certain conditions of summability and symmetry.

Pore-scale study of droplet settling on a heterogenous surface structure

Equilibrium contact angle of a droplet is influenced by surface characteristics and fluid properties. In addition to increasing the solid–liquid contact line, surface roughness also alters the surface free energy, which has a significant influence on contact angle values. Droplets are more likely to impinge on vertices as surface roughness increases. Anisotropic wetting of chemically heterogeneous surfaces further controls the total surface free energy. The free energy Lattice Boltzmann method is utilized to study the effects of wettability heterogeneity and roughened surfaces. Initial model comparisons with experiments showed excellent agreement. The rough surface is modeled with different pillar shapes on a smooth wall, with surface wettability ranging from hydrophilic to neutral conditions. The length scale of surface patterns matches the droplet size, making the Cassie–Baxter and Wenzel equations inapplicable. Results indicate that droplets pin on the vertices of rectangular pillars, while frustum shapes facilitate movement. Studies cover nearly neutral wet, moderately wet, and strongly wet conditions. The effects of relative surface roughness, roughness distribution, mixed wetting surfaces, and body force on equilibrium contact angle are examined. Additionally, the interaction between fluid flow and surface roughness elements shows that smaller spacing and greater height of roughness elements enhance thermal performance, with Nusselt numbers fluctuating significantly. Findings suggest that the ratio of droplet size to pillar surface area is crucial for minimizing surface free energy. On superhydrophilic surfaces, droplet pinning at pillar edges causes the surface to behave hydrophobically. In mixed-wet rough surfaces, pillar wettability significantly influences the equilibrium contact angle.

A study on environmental elements of residential open spaces for grandparent-child rearing based on a field survey in Tianjin, China

With the advent of an aging society, grandparents' involvement in childcare is becoming increasingly common, saving families and society huge nursing costs. Residential open space (ROS) is a common place for grandparents' outdoor childcare activities, influencing the health of grandparents and children. However, existing research on the ROS environmental needs of intergenerational users is still insufficient. This study regards grandparents and children as a cohesive entity, based on environment behavior theory, and constructs a research framework for the ROS environmental elements needs for grandparent-child rearing. Taking a residential area in Tianjin as an example, four types of grandparent-child rearing are identified based on the age of the children. Through interviews with grandparents and observation of outdoor activities involving grandparent-child rearing, significant differences in the needs of ROS environmental elements such as enclosure feeling, pet control, and adult fitness equipment among different types of grandparent-child rearing were found, stemming from different caregiving patterns. This study provides important implications for constructing supportive childcare environments and promoting physical activities and childcare education among intergenerational populations.

Frequency-domain sound field from the perspective of band-limited functions.

A model that approximates the sound field well is useful in various fields, such as acoustic signal processing and numerical simulation. We have proposed an effective model in which the wideband instantaneous sound field is regarded as an element of a spherically band-limited function space, using the reproducing kernel of that space. In this paper, the frequency-domain sound field is regarded as an element of some band-limited function space, and a representation of the field as a linear combination of the reproducing kernel in that space is proposed. This model has the strongest representational capacity of all function systems when we know only the sound pressure information at arbitrary positions. The proposed model can be considered a generalization of the existing three-dimensional sound field model using the reproducing kernel of the solution space of the Helmholtz equation to the spatial dimension. One of the advantages of capturing the frequency-domain sound field in this way is the simplicity achieved for the estimation formula of the wavenumber spectrum. Two numerical simulations were conducted to validate the proposed methods.

A Dual‐Polarized Wide‐Angle Scanning Linear Phased Array Antenna With Simple Decoupling Structure

ABSTRACTA dual‐polarization linear phased array with a simple decoupling structure is designed for wide scanning in this letter. The suggested antenna is made up of two printed dipole antennas that are orthogonally arranged and have a high cross‐polarized isolation. Metal sheets cladding on antenna substrates serve as a decoupling structure, with an array element spacing of 0.48 . A linear phased array of seven elements is fabricated and measured to ensure that the planned array is feasible. The simulated and measured results demonstrate that the phased array can scan its main beam up to ±75° in dual‐polarized excitations at 5.6–6.4 GHz. The co‐polarized mutual coupling is below −28 dB, and the active reflection coefficient of the element is less than −15 dB.

Uniform boundary stabilization of a high-order finite element space discretization of the 1-d wave equation

Uniform boundary stabilization of a high-order finite element space discretization of the 1-d wave equation

An asymptotic-preserving and exactly mass-conservative semi-implicit scheme for weakly compressible flows based on compatible finite elements

We present a novel asymptotic-preserving semi-implicit finite element method for weakly compressible and incompressible flows based on compatible finite element spaces. The momentum is sought in an H(div)-conforming space, ensuring exact pointwise mass conservation at the discrete level. We use an explicit discontinuous Galerkin-based discretization for the nonlinear convective terms, while treating the pressure and viscous terms implicitly, so that the CFL condition depends only on the fluid velocity. To handle shocks and damp spurious oscillations in the compressible regime, we incorporate an a posteriori limiter that employs artificial viscosity and is based on a discrete maximum principle. By using hybridization, the final algorithm requires solving only symmetric positive definite linear systems. As the Mach number approaches zero and the density remains constant, the method naturally converges to an H(div)-based discretization of the incompressible Navier-Stokes equations in the vorticity-velocity-pressure formulation. Several numerical tests validate the proposed method.

Improved Sparrow Search Algorithm for Rectangular Planar Array Synthesis

To optimize sparse rectangular planar array antennas under multiple constraints, including array aperture, number of elements, and minimum element spacing, an improved sparrow search algorithm (ISSA) is proposed. Initially, a position distribution matrix is generated using the Blackman window weighting method. The sparrow search algorithm (SSA) is then enhanced by incorporating Kent mapping for population initialization, which improves the initial population’s diversity. Additionally, the strategy for updating the discoverer’s position integrates elements from the sine cosine algorithm (SCA), along with a nonlinear sine learning factor, thereby enhancing global search capability. Finally, a crossover strategy is embedded into the SSA to refine the optimization accuracy by improving the search methodology used by the vigilantes. To verify the efficacy of our approach, we carried out simulation experiments. The results demonstrate that this method significantly enhances the performance of the array antenna by reducing the peak sidelobe level and minimizing the zero-trap depth. These findings validate the reliability and effectiveness of the suggested method.

Time-dependent electromagnetic scattering from dispersive materials

Abstract This paper studies time-dependent electromagnetic scattering from obstacles that are described by dispersive material laws. We consider the numerical treatment of a scattering problem in which a dispersive material law, for a causal and passive homogeneous material, determines the wave–material interaction in the scatterer. The resulting problem is nonlocal in time inside the scatterer and is posed on an unbounded domain. Well-posedness of the scattering problem is shown using a formulation that is fully given on the surface of the scatterer via a time-dependent boundary integral equation. Discretizing this equation by convolution quadrature in time and boundary elements in space yields a provably stable and convergent method that is fully parallel in time and space. Under regularity assumptions on the exact solution we derive error bounds with explicit convergence rates in time and space. Numerical experiments illustrate the theoretical results and show the effectiveness of the method.

تحولات الحيز في الخطاب الروائي الإماراتي النسوي في القرن الواحد والعشرين: رواية رائحة الزنجبيل لصالحة عبيد غابش أنموذجًا

This study aims to shed light on one of the aspects of Emirati novels, particularly the transformations that have emerged due to the changes undergone by the Emirati society in the 21st century. The study focuses on the element of space to highlight, critique, and analyze these transformations, since space is a crucial element in the narrative discourse. Through space, the reader can unveil the hidden meanings within the text, and a critical analysis of space allows the reader to comprehend the narrative content and its intricacies. Additionally, space often reflects the influence of the environment on the writer's psyche and emotions, which is what we aimed to address in this study. We were able to achieve this through the examination of one of the most prominent novels in the Emirati literary scene, namely: Rā’iḥa Al-Janzabīl [The Scent of Ginger] by the novelist Ṣalḥa ‘Ubayd Ġābish.

Sobolev regularity of bivariate isogeometric finite element spaces in case of a geometry map with degenerate corner

We investigate Sobolev regularity of bivariate functions obtained in Isogeometric Analysis when using geometry maps that are degenerate in the sense that the first partial derivatives vanish at isolated points. In particular, we show how the known C1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$C^1$$\\end{document}-conditions for D-patches have to be tightened to guarantee square integrability of second partial derivatives, as required when computing finite element approximations of elliptic fourth order PDEs like the biharmonic equation.

On some energy‐based variational principles in non‐dissipative magneto‐mechanics using a vector potential approach

AbstractThis contribution covers the variational‐based modeling of non‐dissipative magneto‐mechanical systems using a vector potential approach and the thorough analysis and discussion of corresponding conforming finite element methods. Since the construction of divergence‐free finite element spaces explicitly enforcing the Coulomb gauge poses some major challenges, we propose some primal and mixed variational principles that ensure well posedness of the problem and allow to seek the vector potential in unconstrained function spaces. The performance of these methods is assessed in two comparative benchmark studies. The focus of both studies lies on the accurate approximation of field quantities in systems with material discontinuities and re‐entrant corners.

Three-dimensional Change Detection and Description in Complex Construction Scenarios

Abstract. In large-scale engineering construction scenarios, construction objects and equipment are numerous; their spatial positions and postures change frequently and are complex and varied. Describing the changes between construction entities and the entities themselves in a three-dimensional (3D) geometric space and functional semantic space is challenging. In response to this challenging, we propose a novel workflow to detect and describe the changes in a construction site. First, we add the constraint of object surface continuity to the octree change detection (OCD), exclude the independently changing cells, and improve the change detection robustness. Second, based on the changes in entity elements that occur in the 3D geometric space, we introduce six-type semantics to characterize the changes that occur. Differing from existing change detection semantic description methods that focus on the attribute semantics of changed entity elements, our method focuses on the semantic description of the change process. Finally, for the variations in different semantic types, we propose specific quantization methods that can better quantify the variations in entity elements in 3D geometric space. For the proposed solution, we tested it using two sets of multi-period time-series point cloud data, which can accurately identify the changing construction entities in space and complete the calculation of bridge construction progress, including the building demolition and construction, and the change in the construction apparatus position.