Polygonal Patches Research Articles

Spatiotemporal variations and driving factors of farmland soil organic carbon in various landforms of a complex topography

Estimating the spatiotemporal variations and driving factors of farmland soil organic carbon density (SOCD) is of great significance for enhancing soil carbon sequestration capacity. Herein, a large region of complex topography was targeted, which includes hill–mountain, valley–basin, and plain–platform. Based on the massive amounts of sampling data (57,254 measured values) and a large-scale soil map of 1:10,000 (371,976 polygonal patches), the gravity center migration model and gray correlation model were used to quantify the spatiotemporal variations and driving factors of farmland SOCD. The results indicated that the farmland soils in the study area had dual functions of carbon source and sink during 1982–2018, of which 45.50 % and 54.50 % were identified as carbon source and sink, respectively. Specifically, the SOCD for the entire study area, its hill–mountain, and valley–basin increased from 2.79 kg m−2, 2.97 kg m−2, and 3.06 kg m−2 to 2.87 kg m−2, 3.06 kg m−2, and 3.14 kg m−2, respectively, with 0.08 kg m−2 carbon sequestrations and a northeast migration direction for the SOCD gravity center (angle: 21.94°, 23.56°, and 18.82°; distance: 1.56 km, 2.73 km, and 3.20 km). There was a smaller increase of 0.07 kg m−2 in SOCD for the plain–platform from 2.38 kg m−2 (1982) to 2.45 kg m−2 (2018), and the SOCD gravity center migrated to the southwest with an angle of −172.46° and a distance of 1.84 km. Thus, the spatiotemporal variations of farmland SOCD in various landforms varied greatly. Over the past 36 years, SOCD variations were driven by a combination of intrinsic soil factors and external factors such as human disturbance. However, the driving effects of these factors on the landforms of hill–mountain, valley–basin, and plain–platform were quite different in size and order. Therefore, we suggest that topography must be considered when formulating policies to improve soil carbon sequestration, and priority should be given to landform-specific SOCD variation and the factors contributing to them.

Generalized Bézier volumes over simple convex polyhedra

In recent years, there has been growing interest in the representation of volumes within the field of geometric modeling (GM). While polygonal patches for surface modeling have been extensively studied, there has been little focus on the representation of polyhedral volumes. Inspired by the polygonal representation of the Generalized Bézier (GB) patch proposed by Várady et al. (2016), this paper introduces a novel method for polyhedral volumetric modeling called the Generalized Bézier (GB) volume.GB volumes are defined over simple convex polyhedra using generalized barycentric coordinates (GBCs), with the control nets which are a direct generalization of those of tensor-product Bézier volumes. GB volumes can be smoothly connected to adjacent tensor-product Bézier or GB volumes with G1 or G2 continuity. Besides, when the parametric polyhedron becomes a prism, the GB volume also degenerates into a tensor-product form. We provide some practical examples to demonstrate the advantages of GB volumes. Suggestions for future work are also discussed.

DESIGN AND ANALYSIS OF MICROSTRIP ANTENNA FOR 5G APPLICATIONS

A new proposed antenna is presented in this article for 5G applications. The dimensions of this antenna are (32×32×0.8) mm³. The antenna that is suggested is built upon FR-4 epoxy dielectric substrate, with a loss tangent of 0.025 and relative permittivity of dielectric is 4.3 and, on the top layer of this substrate a polygon patch is etched with specific dimensions, also a ground plane on the bottom layer of the substrate is built. The patch of the antenna is fed from a microstrip feed line with a 50Ω characteristic impedance. The proposed antenna operates at 3.6 GHz as a resonance frequency with a bandwidth of (3.15 - 4.3) GHz, and gain (3.3) dBi at the operating frequency, these characteristics are suitable for 5G applications. To attain the targeted bandwidth and gain, distinct slots are carved onto both the patch and ground plane. The simulation outcomes are gathered using CST-MW 2020.

A Modified Polygon Shaped Microstrip Patch Antenna Array for Ultra-Wideband Applications

A single element and two elements array polygon shape microstrip antenna is proposed and analyzed in this paper for ultra-wideband (UWB) applications. The technique used to improve antenna performance is etching rectangular slots on the patch of the antenna with different dimensions and positions. Two Polygon Shape antenna patches are introduced to enhance the antenna properties. Also, multi-slots are reached to improve the antenna gain, impedance matching sweep parameter optimization technique is used to all antenna parameters to enhance antenna properties. The dimensions of the single element antenna are 30 x 33 mm2 and consist of a slotted polygon patch printed on an FR-4 substrate. The proposed antenna has a resonant frequency of 6.2 GHz, while the dimensions of two elements antenna array are 60 x 33 mm2 and the resonance frequency is 9.8 GHz. A technique of inset feed transmission line was utilized to match the 50 Ω microstrip feed line and the radiating patch. These considerations make the structure is suitable for fifth-generation generation (5G) mobile wireless applications. The proposed antenna was simulated by use Computer Simulation Technology (CST-2020) software.

A Wideband Antenna for GNSS Applications with Improved Orthogonal Dipole

This letter presents a wideband antenna for high-precision Global Navigation Satellite System (GNSS) applications. The antenna consists of a pair of improved orthogonal dipoles that are fed by a feed network with Composite Right/Left-Handed Transmission Lines (CRLH-TLs), a polygonal patch, and a reflector. By using improved orthogonal dipole, the beamwidth of the antenna is broadened. The CRLH-TLs is adopted in feed network to obtain outputs with stable phase difference. Experiment results indicate that the antenna has a less than 10-dB return-loss bandwidth in the range of 1.1 to 1.7 GHz, a 3-dB axial-ratio bandwidth from 1.2 to 1.6 GHz, and a larger than 6.37 dBi gain in the whole operating band. The measured results show that the proposed antenna has stable performance in the whole operating band, which means that it is a suitable antenna used for GNSS applications.

Mineralogy and Geochemistry of Ocelli in the Damtjernite Dykes and Sills, Chadobets Uplift, Siberian Craton: Evidence of the Fluid–Lamprophyric Magma Interaction

The study reports petrography, mineralogy and carbonate geochemistry and stable isotopy of various types of ocelli (silicate-carbonate globules) observed in the lamprophyres from the Chadobets Uplift, southwestern Siberian craton. The Chadobets lamprophyres are related to the REE-bearing Chuktukon carbonatites. On the basis of their morphology, mineralogy and relation with the surrounding groundmass, we distinguish three types of ocelli: carbonate-silicate, containing carbonate, scapolite, sodalite, potassium feldspar, albite, apatite and minor quartz ocelli (K-Na-CSO); carbonate–silicate ocelli, containing natrolite and sodalite (Na-CSO); and silicate-carbonate, containing potassium feldspar and phlogopite (K-SCO). The K-Na-CSO present in the most evolved damtjernite with irregular and polygonal patches was distributed within the groundmass; the patches consist of minerals identical to minerals in ocelli. Carbonate in the K-Na-CSO are calcite, Fe-dolomite and ankerite with high Sr concentration and igneous-type REE patterns. The Na-CSO present in Na-rich damtjernite with geochemical signature indicates the loss of the carbonate component. Carbonate phases are calcite and Fe-dolomite, and they depleted in LREE. The K-SCO was present in the K-rich least-evolved damtjernite. Calcite in the K-SCO has the highest Ba and the lowest Sr concentration and U-shaped REE pattern. The textural, mineralogical and geochemical features of the ocelli and their host rock can be interpreted as follows: (i) the K-Na-CSO are droplets of an alkali–carbonate melt that separated from residual alkali and carbonate-rich melt in highly evolved damtjernite; (ii) the Na-CSO are droplets of late magmatic fluid that once exsolved from a melt and then began to dissolve; (iii) the K-SCO are bubbles of K-P-CO2 fluid liberated from an almost-crystallised magma during the magmatic–hydrothermal stage. The geochemical signature of the K-SCO carbonate shows that the late fluid could leach REE from the host lamprophyre and provide for REE mobility.

Carbon storage in vegetation and soil in Chinese ecosystems estimated by carbon transfer rate method

AbstractTerrestrial carbon storage is split predominantly between vegetation and soils. However, the spatial distribution of terrestrial carbon and its presence in each carbon pool remains unclear. This study explored the spatial distribution of terrestrial carbon in these two carbon pools across Chinese ecosystems, which differ in vegetation types. Carbon storage was estimated using the carbon transfer rate method, which uses net primary productivity (NPP) and the turnover rate to estimate vegetation and soil carbon pools under the assumption of steady state. The distribution of carbon storage per unit area (carbon density) was shown based on the latest vegetation map (2008). Compared with recent estimates of 89.27 Pg C, our results showed that a total of only 55.46 Pg C have been stored over recent decades. Of this total, 18.19 and 37.27 Pg C were stored, respectively, in vegetation and in soil carbon pools. Among the eleven vegetation types in this study, needleleaf forest had the largest carbon storage (13.57 Pg C). The eleven vegetation types were classified into four major vegetation classes (forest, scrub, grass, and cultivated), of which forests had the higher carbon storage (21.7 Pg C) and the highest carbon density. Our estimates of the spatial distribution of carbon were consistent with previous studies. Both terrestrial and soil carbon pools exhibited higher carbon density in northeast China and the southeastern part of the Tibetan Plateau. Vegetation exhibited a high carbon density in eastern China but low carbon density in western China. Furthermore, our results had a higher spatial resolution of carbon distribution (75,000 polygon patches of the latest vegetation map) than previous studies. These results contribute to understanding carbon accumulation in different ecosystems.

Compact wide stopband microstrip lowpass filter using polygon patches and meandered lines

In this paper, a low pass filter based on T-Shaped resonator is presented. The T-Shaped resonator consists of meandered lines and rectangular patches. Also, the LC model and transfer function of the proposed resonator is presented. For suppression of spurious harmonics, a bandstop structure consists of hexangular patches and open stubs has been utilized. Finally, the wide stopband microstrip lowpass filter with cutoff frequency 2.72 GHz has been simulated, fabricated and measured. The LPF has good characteristics such as wide stopband and insertion loss lower than 0.18 dB in the passband region. The rejection level is less than -20 dB from 2.98 up to 21.3 GHz. The filter size is 10.5 mm×12.7 mm, or 0.131 λ<sub>g</sub>× 0.158 λ<sub>g</sub>, where λ<sub>g</sub> is the guided wavelength. The measured and simulated results of the filter is in good agreement with each other, which show the merits of low insertion loss and wide stopband.

A broadband dual‐polarized antenna with irregular polygon patches and trapezoidal coupling plates

AbstractIn this article, a small broadband dual‐polarized antenna is presented. The main structure consists of the four irregular polygon patches printed on the bottom layer of the substrate, two trapezoidal coupling plates printed on the top layer of the substrate, and a box‐shaped reflector at the back of the substrate at resonance distance. Design principles are based on the rules of complementary antennas, cross dual‐polarized antennas, and aperture antennas. The proposed antenna has technical specifications such as impedance bandwidth 48% (1.7‐2.7 GHz) with lower than 15 dB return loss, port‐to‐port isolation about 32 dB, high pattern stability, and half‐power beam width about 63 ± 9°. The antenna measurement results confirm these. At the end, a comparison between the proposed antenna and the other antennas of this type is presented. The proposed antenna has smaller dimensions, high gain, high port isolation, and excellent pattern stability over the whole bandwidth. The proposed antenna can be used in the base transceiver stations (BTSs) and multi input–multi output (MIMO) systems.

A novel compact lowpass filter with sharp roll-off and wide stopband

AbstractIn this paper, a microstrip lowpass filter adopting two main resonators with steep transition band and wide rejection band has been introduced. The first main resonance cell consists of meandered transmission lines which are loaded by modified T-shaped patches. The second main resonator is composed of high-impedance lines loaded by polygon patches. To obtain a steep skirt performance, the first and second resonators have been combined. Moreover, employing eight high–low impedance folded stubs and two rectangular open-stubs as suppressing cells has resulted in improving the stopband features. To comprehend the frequency behavior of the employed resonators and also their combination, the formulas of the transmission coefficient, reflection coefficient, and the transmission zeros of their equivalent LC circuits have been extracted, separately. According to the measurement results, the −3 dB operating frequency of this filter is 1.65 GHz. Moreover, a relative stopband bandwidth equal to 166% with a corresponding attenuation level of 23 dB and a sharp roll-off rate (393.61 dB/GHz) have been achieved. In the passband region from DC to 1.632 GHz, the insertion loss and return loss are better than 0.0763 and 15.85 dB, respectively, proving an acceptable in-band performance. Finally, the implemented structure brings about a high figure-of-merit equal to 81 672.

Active flow control using dense wireless sensor and actuator networks

This paper describes the design of an active flow control (AFC) system for aeronautics applications based on dense wireless sensor and actuator networks (WSANs). The objective of this AFC system is to track gradients of pressure (or wall shear stress) across the surface of the fuselage of commercial aircraft. This collected information is used to activate a set of actuators that will attempt to reduce the skin drag effect produced by the separation between laminar and turbulent flows. This is expected to be translated into increased lift-off forces, higher vehicle speeds, longer ranges and reduced fuel consumption. The paper describes the architecture of the system in the context of the European research project DEWI (dependable embedded wireless infrastructure) using the concept of the DEWI Bubble and its three-tier architecture especially designed to ensure dependability and interoperability in industrial WSANs. A system-level simulator is also proposed to model each process of the AFC system and the aeronautics DEWI Bubble infrastructure, highlighting the interactions between the network simulation and the results of the computational fluid dynamics (CFD) simulation. The key element in the proposed solution is a polygonal patch of wired sensors and actuators. This patch is provided with a wireless link to a central coordinator or access point conveniently located in the aircraft to maximize coverage to a network of distributed patches. A trade-off between scalability, size of the patches, fluid speed/viscosity, sampling sensor and actuator rates in space and time, and the capacity/delay characteristic of the wireless inter-patch and the wireline intra-patch communication technologies is also here discussed. The hybrid wireless/wired sensor and actuator network achieves great flexibility, scalability, manageability, troubleshooting, and modularity as compared to a solution exclusively based on wireline or wireless components. The final details of the prototype and results in a wind tunnel test-bed are here described, demonstrating the validity of the concept and the use of wireless technologies for aeronautical applications (flexible architecture and innovative services). Future issues regarding security, safety and trustiness of the AFC system are also briefly introduced in the context of the spin-off European project SCOTT (secure connected trusted things).

Analytical design for computer-generated Fourier holograms of shaded multi-polygonal three-dimensional objects

ABSTRACTWe report here on design and computer simulation of computer-generated holograms for three dimensional (3D) imaging and display. Angular spectrum of general polygon patches was calculated in closed analytical form that includes angular dependence of the intensity and linear gradient of phase at each polygon. Special attention was paid to reduction of the dynamic range in the amplitude transmittance of the hologram by proper random choices of slopes and initial phases of each polygon. Numerical computer simulation results proved that our polygon-patched design demonstrates halftones of object shades and shows expected sharp focusing of different parts of the reconstructed 3D images in their different cross-sections.

Equality testing for soil grid unit resolutions to polygon unit scales with DNDC modeling of regional SOC pools

Matching soil grid unit resolutions with polygon unit map scales is important to minimize the uncertainty of regional soil organic carbon (SOC) pool simulation due to their strong influences on the modeling. A series of soil grid units at varying cell sizes was derived from soil polygon units at six map scales, namely, 1:50 000 (C5), 1:200 000 (D2), 1:500 000 (P5), 1:1 000 000 (N1), 1: 4 000 000 (N4) and 1:14 000 000 (N14), in the Taihu Region of China. Both soil unit formats were used for regional SOC pool simulation with a DeNitrification-DeComposition (DNDC) process-based model, which spans the time period from 1982 to 2000 at the six map scales. Four indices, namely, soil type number (STN), area (AREA), average SOC density (ASOCD) and total SOC stocks (SOCS) of surface paddy soils that were simulated by the DNDC, were distinguished from all these soil polygon and grid units. Subjecting to the four index values (IV) from the parent polygon units, the variations in an index value (VIV, %) from the grid units were used to assess its dataset accuracy and redundancy, which reflects the uncertainty in the simulation of SOC pools. Optimal soil grid unit resolutions were generated and suggested for the DNDC simulation of regional SOC pools, matching their respective soil polygon unit map scales. With these optimal raster resolutions, the soil grid units datasets can have the same accuracy as their parent polygon units datasets without any redundancy, when VIV < 1% was assumed to be a criterion for all four indices. A quadratic curve regression model, namely, y =–0.80 × 10–6 x 2 + 0.0228x + 0.0211 (R 2 = 0.9994, P < 0.05), and a power function model R = 10.394Ŝ 0.2153 (R 2 = 0.9759, P < 0.05) were revealed, which describe the relationship between the optimal soil grid unit resolution (y, km) and soil polygon unit map scale (1:10 000x), the ratio (R, %) of the optimal soil grid size to average polygon patch size (Ŝ, km2) and the Ŝ, with the highest R 2 among different mathematical regressions, respectively. This knowledge may facilitate the grid partitioning of regions during the investigation and simulation of SOC pool dynamics at a certain map scale, and be referenced to other landscape polygon patches’ mesh partition.

Adaptive Poly-FEM for the analysis of plane elasticity problems

ABSTRACTIn this work, we present an adaptive polygonal finite element method (Poly-FEM) for the analysis of two-dimensional plane elasticity problems. The generation of meshes consisting of n − sided polygonal finite elements is based on the generation of a centroidal Voronoi tessellation (CVT). An unstructured tessellation of a scattered point set, that minimally covers the proximal space around each point in the point set, is generated whereby the method also includes tessellation of nonconvex domains. In this work, we propose a region by region adaptive polygonal element mesh generation. A patch recovery type of stress smoothing technique that utilizes polygonal element patches for obtaining smooth stresses is proposed for obtaining the smoothed finite element stresses. A recovery type a − posteriori error estimator that estimates the energy norm of the error from the recovered solution is then adopted for the Poly-FEM. The refinement of the polygonal elements is then made on an region by region basis through a refinement index. For the numerical integration of the Galerkin weak form over polygonal finite element domains, we resort to classical Gaussian quadrature applied to triangular subdomains of each polygonal element. Numerical examples of two-dimensional plane elasticity problems are presented to demonstrate the efficiency of the proposed adaptive Poly-FEM.

Planar elliptic function lowpass filter with sharp roll-off and wide stopband

A compact planar elliptic function lowpass filter with sharp roll-off at 20 dB attenuation level and wide stopband using microstrip stepped-impedance polygonal patch resonators is developed and investigated. Electromagnetic simulation is used to optimize the performance of the filter. The filter using cascaded multiple patch resonators provides a very sharp attenuation near cutoff frequency with a high stopband suppression level. The rejection bandwidth is enhanced by introducing additional transmission zeroes and the results are validated by the experiment. The filter has a compact size of 17.6 mm × 12.2 mm. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:133–136, 2016

Segmentation-based semi-regular remeshing of 3D models using curvature-adapted subdivision surface fitting

This paper proposes a novel method of semi-regular remeshing for triangulated surfaces to achieve superior triangles lead to advanced visualization of 3D model. It is based on mesh segmentation and subdivision surface fitting which uses curvature-adapted polygon patches. Our contribution lies in building a sophisticated system with three stages, i.e., curvature-aware mesh segmentation, submesh surface fitting to generate a high-quality semi-regular mesh and finally, stitching the segments using an efficient algorithm. Our method uses centroidal Voronoi tessellation and Lloyd’s relaxation to generate curvature-adapted site centers. Geodesic distances from site centers are used for labeling segments and indexing corner vertices for each segment boundary. Using information of site centers and corner vertices, feature-adapted polygonal patches are generated for each segment. These patches are then subdivided and optimized using squared distance metric to adjust position of the subdivision sampling with segment details and prevent oversampling. At last, an efficient stitching algorithm is introduced to connect regular submeshes together and build the final semi-regular mesh. We have demonstrated the results of our semi-regular remeshing algorithm on meshes with different topology and complexity and compared them with known methods. Superior triangle quality with higher aspect ratio together with acceptable distortion error is achieved according to the experimental results.

Polygon-Shaped Slotted Dual-Band Antenna for Wearable Applications

This letter presents the design of a wearable dual-band patch antenna for operating in the GSM-900 and 1800 bands. The proposed polygon patch antenna comprises a circular slot and vertical slits embedded on jeans substrate. This structure provides two paths for currents, making it viable for dual bands. The effect of patch length, slot radius, and slit length on the overall antenna performance is analyzed by performing a comprehensive parametric study. Further bending, crumpling, wetness, and on-body measurements have been performed to validate the structure. Specific absorption rate (SAR) values ranging between 0.00039-0.0035 W/Kg have been obtained for two different analyses.

Study of a Class of UWB CPW-Fed Monopole Antenna With Fractal Elements

This letter investigates a multiresonance technique to achieve ultrawideband (UWB) characteristics in a coplanar waveguide (CPW)-fed monopole antenna. It is found that by addition of small fractal elements at the corners of a polygon patch, standard UWB bandwidth can be covered while antenna dimensions are only 25 × 25 mm2. Parametric analysis is performed, and different shapes are added to the antenna as the fractal element in order to realize the multiresonance behavior. Fidelity factor of the antenna is greater than 0.92 in both elevation and azimuth planes. To validate the simulation results, prototypes of the proposed antenna are fabricated and tested.

Facial Contact Dermatitis and the Irritant Potential of Mobile Phone Screens

A teenager with atopic dermatitis presented with a 12-month history of recurrent, pruritic, round and polygonal patches on her face. Patch tests using the European standard series (including nickel, chromium, and cobalt chloride), a plastic and glue series of allergens, polyester components, and personal and environmental products in contact with the patient were conducted. For the patient and 3 of 14 healthy volunteers, positive reactions were observed to the patient's mobile phone touchscreen (TS), an extract solution from the TS, and a non-TS phone of another brand. Accordingly, the patient's dermatitis disappeared when contact with mobile phone screens was avoided.

A Wide-Band Antenna Design by Using Electromagnetic Simulation Software

A wide-band antenna coupling with an elliptical slot was discussed in this paper. To implement the wide band operation, an elliptical ring slot was etched on a polygonal patch. The properties of this design have been verified by using electromagnetic simulation software. Comparing to the conventional U-slot patch antenna fed by Π-shaped slot, the proposed structure is with the same impedance in bandwidth, but less than 10% in size.