Region-shrinking: a hybrid segmentation technique for isolating continuous features, the case of oceanic eddy detection

In remote sensing image analysis, limited attention has been devoted to the isolation of fuzzy objects, namely those with inherently indeterminate boundaries, from continuous field data. This study develops a “region-shrinking” segmentation technique tailored specifically to the problem of fuzzy object identification, and applies it to the test case of oceanic eddy detection. The region-shrinking technique employs an evolutionary boundary definition procedure to simultaneously identify segments containing oceanic eddies, and refine the boundaries of these segments to correspond to eddy perimeters. This algorithm combines a Non-Euclidean Voronoi segmentation technique with insights from existing work on eddy detection from an oceanographic perspective, with the goal of improving the detection of eddy features through sea level anomaly imagery. It takes into account multiple criteria (vorticity, size, amplitude, the existence of local sea level extrema, concave or convex shape) to iteratively refine the identification and demarcation of oceanic eddies. The resulting polygons define tightly fitted eddy boundaries, and conform to the key rotational and cross-sectional height profile characteristics used by physical oceanographers to identify eddies

Three-dimensional seismic stability of locally loaded slopes under a rotational velocity field

In practical engineering, slopes subjected to local loads, like footings of buildings, are common. This paper aims to give an insight into the effect of seismic force on the stability of locally loaded slopes. Numerical methods can be used to study this problem, but they require much computational time. Contrarily, limit analysis method is an approach to perform slope stability analysis with high computational efficiency. Thus, an accurate approach in mechanical points is proposed for this problem based on limit analysis method herein. In the framework of limit analysis, existing research about this problem used a kinematically translational velocity field. However, the velocity field of the locally loaded slope at failure is proved to be rotational possibly. Thus, to fill this gap, a 3D rotational velocity field is employed herein to obtain limit loads on the slope top, which improves the existing upper-bound solutions obtained by using the translational velocity field. The particle swarm optimization algorithm and the Nelder-Mead simplex algorithm are employed to search the global minimum of the upper-bound estimation of the limit load. Parametric analysis is performed and it shows that the limit load increases with the increase of a/H or the internal friction angle φ but decreases as the slope angle β or the length-to-width ratio (L/t) of the local load increases. Furthermore, the limit load is found to decrease with the increase of the seismic coefficient kh and it is proportional to the seismic coefficient

Reading Promotion: Conceptual Models and Category Frameworks Analysis

The paper summarizes the practical and theoretical development of reading promotion in various countries in the world and reveals the status of the magnificent practices and active research of reading promotion in China. According to the conceptual object, the existing definitions of reading promotion are divided into the goal-oriented conceptual model and the content-oriented conceptual model . The defining principles and conceptual scopes of these two models are analyzed. Starting with confirming the defining principle and analyzing the scopes of conceptual elements, the definitions of reading promotion and library reading promotion are given. The research is beneficial for librarians to better cognize the conceptual scope of reading promotion and to plan the work

A Compact Monopole Antenna With Filtering Response for WLAN Applications

A novel compact monopole antenna with filtering response for WLAN applications is presented in this paper. The antenna is composed of a capacity-loaded matching patch, two resonators, and two end-coupled monopoles. The resonators consist of wide rectangular patches and narrow shorted lines to form the resonance, and the resonators are printed on the different layers to increase the design flexibility. Two meandering monopoles are located at the edges of the top layer with capacitive coupling at each other's end. The mutual couplings between the meander monopoles are utilized to produce two radiation nulls at the two band-edges. Based on the design method, the prototype of the proposed antenna was designed, fabricated and measured. The measured results show that the antenna has a broad bandwidth of 16% for S 11 <; -10 dB. Also, ideal omnidirectional radiation patterns, and steep band-edge selectivity with two radiation nulls are achieved for the proposed antenna

Crystal Structure of Spirocyclic Pentaerythritol Phenol Ester of Phosphoric Acid

Spirocylic pentaerythritol phosphate ester, a kind of intumescent flame retardant, has good compatibility with the polypropylene and excellent flame retardant on PP. However the correlation between the space structures of the intumescent flame retardant and polypropylene has not been revealed. In this paper crystal diffraction of spirocyclic pentaerythritol phenol ester of phosphoric acid are used to study its structure features and the results show that the phenol ester crystal is orthorhombic, Pna21 space group, and there are two six-member rings linked to the same atom which belongs to similar chair conformation forming a stable spiro structure and an irregular axisymmetric structure, and none weak hydrogen bonds exists in the system

Millimetre-Wave Dual-Polarized Differentially-Fed 2D Multibeam Patch Antenna Array

In this paper, a novel millimetre-wave dual-polarized 2D multibeam antenna array incorporating differentially-fed antenna elements is proposed to achieve high cross-polarization discrimination (XPD) when the beams scan to the maximal pointing angles. The antenna element is composed of a SIW cavity with four shorted patches placed inside, and it is differentially excited for dual-polarization by a pair of feeding strips and transverse slots beneath the patches. Differential excitation is realized by a power divider designed on two laminate layers. Two Butler Matrices placed perpendicularly with each other in different laminates are employed to generate four tilted beams with dual-polarization. A 2 × 2 dual-polarized 2D multibeam antenna array working at 28 GHz is designed, fabricated, and measured. The operation bandwidth of the antenna is 26.8 GHz – 29.2 GHz. The improvement in the XPD is experimentally demonstrated by far-field measurement. When the beams scan to 30◦ off the boresight, the measured XPDs are 28 dB at the centre frequency and higher than 25 dB over the operation bandwidth, which confirms that the cross-polarized radiation in the 2D multibeam antenna array is suppressed by using the differential-feeding technique. The measured gain is in the range from 7.6 dBi to 10.5 dBi

A Wideband Series-Fed Circularly Polarized Differential Antenna by Using Crossed Open Slot-Pairs

A novel method of designing a wideband series-fed circularly polarized (CP) differential antenna by using crossed open slot-pairs is presented in this paper. The near-field distributions and input impedance analyses show that the closely spaced open slot-pairs can radiate as the crossed dipoles and have stable radiating resistance with a compact radiator size. Besides, a wideband half-power phase shifter by using open slot is proposed and utilized to realize CP radiation. The proposed CP antenna is composed of a wide slot-pair and a narrow slot-pair. In the antenna design, the narrow slot-pair is not only excited as a radiator, but also elaborately loaded to provide wideband half-power output and quadrature phase excitation to the wide slot-pair. Both the proposed half-power phase shifter and CP antenna are illustrated by the corresponding equivalent circuits. Based on these analyses, the proposed antenna is designed, fabricated and measured. Compared to the simulated traditionally designed counterpart, 2.1 times wider axial ratio bandwidth is achieved for the proposed antenna. The measured overlapped bandwidth for axial ratio 10 dB is 1.95-3.45 GHz (55.6%). Also, the antenna gain and radiation patterns are measured, which agree well with the simulated results

A Dual-Polarized Planar Antenna Array Differentially-Fed by Orthomode Transducer

This paper presents a new design of a differentially-fed substrate integrated planar antenna array with dual-polarization. Compared with the traditional dual-polarized antenna arrays, the proposed array antenna has the advantages of simple configuration, high cross-polarization discrimination (XPD) and high gain. 2×2-element subarray design with a vialoaded crossover structure is used, which reduces the complexity of the array antenna. The operation bandwidth is improved by generating three resonances in the subarray. One 8×8 antenna array is designed, prototyped and tested to exemplify its potential applications in large dual-polarized antenna arrays. A planar orthomode transducer is used to achieve differential excitation for the antenna array. The measured results show that the proposed antenna array has an impedance bandwidth of 19.2–20.7 GHz for |S11| < −10 dB and port isolation higher than 20 dB. The array antenna exhibits a high XPD of 43 dB and a flat gain about 22.2 dBi within the bandwidth

A Low Complexity 16 X 16 Butler Matrix Design Using Eight-Port Hybrids

Beamforming networks such as Butler Matrices are important for multibeam array antenna applications. The challenge for Butler Matrix design is that their complexity increases with the number of ports. In this paper, a novel approach of designing a 16 X 16 Butler Matrix with significant structure simplification is presented. The eight-port hybrids with no crossovers are used to simplify the network. To ensure the network has the same magnitude and phase responses as the standard one, the location and phase shifting value of each fixed phase shifter are derived from the $S$ -matrix of each hybrid. A $16\times 16$ Butler Matrix network operating from 9 GHz–11 GHz is designed to validate this concept. The compensated microstrip 3-dB/90° directional coupler, the phase shifter with a shunt open-and-short stub and the crossover with a resonating patch are used to reduce the transmission loss and enable broadband operation