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The elastic wave bandgap (BG) properties of locally resonant phononic crystal (LRPC) make it has great potential in the research and development of damping composite material and the application of vibration control engineering. However, the number of BG of the traditional LRPC is only one, the BG frequency range is too concentrated, and the multi-frequency BGs is not opened, so the application in practical engineering is limited. In response to the above issues, this paper designs a concentric ring cement-based locally resonant phononic crystal (CRCBLRPC) composite material, and studies and analyzes its BG characteristics. Firstly, the improved plane wave expansion method (IPWEM) and finite element method (FEM) are used to calculate the band structure of the CRCBLRPC. Secondly, the transfer function and BG mechanism of CRCBLRPC are calculated using FEM. Then, the factors affecting the BG of CRCBLRPC are analyzed. Finally, an equivalent model of spring-mass system is proposed to theoretically estimate the BG range of CRCBLRPC. The results show that the CRCBLRPC opens multi-frequency and low frequency BGs within the 200 Hz frequency band, and the number of BGs is more than that of the traditional LRPC. Within the BG frequency range, the CRCBLRPC has a good inhibition effect on vibration. Among them, the density of the scatterer and the elastic modulus of the coating layer are the main factors affecting the BG of the CRCBLRPC. The established spring-mass system equivalent model can accurately calculate the BG range of the CRCBLRPC. The research content and related conclusions of this paper provide new perspectives and insights for the study and design of LRPC composite materials with multi-frequency and low frequency BGs, and can also provide new ideas and methods for solving low frequency vibration in practical engineering. [ABSTRACT FROM AUTHOR]

The world is experiencing unprecedented urbanization, particularly through the continuous growth of megacities, leading to significant urban land expansion. The spatial layout and growth patterns of urban areas play a critical role in determining cities' sustainable development. However, the optimal path for cities undergoing rapid urbanization remains uncertain. This study examines four megacities—Tokyo, Seoul, Beijing, and Shanghai—and, from the perspective of urban land density, compares their patterns and processes of land expansion in 1990, 2000, 2010, and 2020. Findings reveal that the urban land area of China's megacities has expanded nearly fourfold over the past three decades. Meanwhile, Tokyo and Seoul have adopted a polycentric urban structure, becoming increasingly compact. In contrast, Beijing and Shanghai are only beginning to show signs of polycentric development. The study concludes that cities experiencing rapid growth should not impose excessive limitations on urban expansion. Polycentric and compact development has become a critical strategy for megacities. These insights offer valuable guidance for urban planning and sustainable development in both established and emerging megacities across East Asia.

In order to find the optimal expansion effect of a new curing expansion material so that it can better meet the requirements of the efficient sealing of drilled holes, the expansion and creep characteristics of the new curing expansion material were studied. Based on the creep results of graded loading, the Kelvin–Volgt model was selected to analyze its mechanical parameters, and a new "concentric ring" reinforcement sealing method was proposed. Numerical simulation was employed to analyze and discuss the reinforcement radius and depth of the "protective wall rock hole ring" in the "concentric ring" model, and on-site application experiments were carried out in a soft coal seam. The results show that the "concentric ring" reinforcement sealing method can effectively solve the problems of easy collapse and stress concentration instability in the sealing section of soft coal seams, ensuring long-term and efficient sealing of gas extraction boreholes in soft coal seams. When the diameter of the extraction drilling hole is 100 mm, the optimal reinforcement radius for the "protective wall rock hole ring" is 0.16–0.18 m. A reasonable reinforcement depth of the "protective wall rock hole ring" for drilling in soft coal seams is about 0.8–1 times the width of the roadway. In the on-site application process, experimental boreholes using "concentric ring" reinforcement sealing technology did not show any collapse phenomena, and the volume fraction of extracted gas remained above 30% for the first 30 days. Moreover, the gas volume fraction on the 30th and 60th days was 2.5 times and more than 3 times that of bag sealing boreholes using expanded cement, further proving that the sealing quality of boreholes using "concentric ring" reinforcement sealing is higher. [ABSTRACT FROM AUTHOR]

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The world is experiencing unprecedented urbanization, particularly through the continuous growth of megacities, leading to significant urban land expansion. The spatial layout and growth patterns of urban areas play a critical role in determining cities' sustainable development. However, the optimal path for cities undergoing rapid urbanization remains uncertain. This study examines four megacities—Tokyo, Seoul, Beijing, and Shanghai—and, from the perspective of urban land density, compares their patterns and processes of land expansion in 1990, 2000, 2010, and 2020. Findings reveal that the urban land area of China's megacities has expanded nearly fourfold over the past three decades. Meanwhile, Tokyo and Seoul have adopted a polycentric urban structure, becoming increasingly compact. In contrast, Beijing and Shanghai are only beginning to show signs of polycentric development. The study concludes that cities experiencing rapid growth should not impose excessive limitations on urban expansion. Polycentric and compact development has become a critical strategy for megacities. These insights offer valuable guidance for urban planning and sustainable development in both established and emerging megacities across East Asia. • We compared the spatial and temporal variation of urban land density in East Asian megacities over the past 30 years. • We divided urban area using contour lines of urbanness with different thresholds. • A multi-center development pattern may help alleviate urban development pressure. [ABSTRACT FROM AUTHOR]

• Concentric ring arrays form circularly symmetric wide-viewing angle structural colors that are easy to identify and useful as markers. • The number of pulses is used to control the microscopic morphology, resulting in light and dark structural colors that can be used for anti-counterfeiting coding. • The high throughput of 40 mm2/s gives this structured color processing method great potential for low-cost mass manufacturing. The laser-induced structural coloring technique holds significant potential for various applications due to its precision, controllability, and versatility across different materials. However, laser-induced structural colors face the problems of durability, homogeneity and indistinguishability, which are not conducive to their application as large-scale identifiable markers. In this paper, an innovative approach has been developed to achieve a circular-symmetric structural color display on durable SiC surfaces by fabricating periodic concentric ring structure arrays using the sidelobe light field of a femtosecond zero-order Bessel beam. The research involved a systematic study of the effects of laser power and pulse number on SiC, along with a detailed analysis of the micro-nanostructures evolving on the SiC surface after laser scanning. Additionally, an examination of the characteristics of circular-symmetric structural color displays and their wide viewing angles in periodic circular structures was conducted. Finally, a comparison was made between the structural color display effects of a concentric ring structure generated by a single pulse and the Laser-Induced Periodic Surface Structures (LIPSS) generated by three pulses. This comparison underscores the potential application of alternating between the high saturation color of the concentric ring structure and the low saturation dark light of the LIPSS for anti-counterfeit coding purposes. The findings of this research present promising opportunities for low-cost mass manufacturing in anti-counterfeit labeling and the advanced processing of photonic devices using SiC. [ABSTRACT FROM AUTHOR]

This paper proposes a reconfigurable circular microstrip antenna to serve the wireless communication applications that make use frequency bands such as ISM (Industrial Scientific and Medical), WLAN (Wireless Local Area Network), UMTS (Universal Mobile Telecommunications Service). Reconfigurability is achieved with the help of four MEMS (Micro-Electro-Mechanical Systems) switches to change the frequency and radiation properties of the antenna. By choosing either of the two states of each of the MEMS switches, the radius of the circular patch is varied and subsequently the operating resonant frequency. This gives rise to multiple configurations of the antenna to serve for different wireless applications. Defected Ground Structure is employed in this design to lower the resonant frequency and improve the bandwidth. Concentric rings are implemented along with a core circular patch in order to increase the radiating area of the patch in association with the MEMS-based switches to operate in toggle mode of ON and OFF. The concentric rings also helping in obtaining dual-frequency behavior of the antenna and the measured results are showing good agreement with the simulation results. [ABSTRACT FROM AUTHOR]

Twenty seven (27) isolates of Alternaria porri were isolated from diseased leaf samples collected from different onion growing regions of Bangladesh and characterized for cultural, morphological and pathogenic variabilities. A. porri colonies colony colour ranged between light to dark olivacious and grayish white with irregular, regular with concentric ring and regular without concentric ring shape. Margin of colonies were entire, irregular and wavy with effuse, fluffy and velvety texture. Isolates impregnated media with colour ranged between grey to brown on the reverse of the plates. Growth rate of isolates ranged between 2.433 and 3.950 mm/day with fast growth in isolate DSTR 02 and least in MMBH. Morphological variation in conidia production was between 7.720×103 to 47.02×103 per mm2 with sporulation time 3.33 to 11.00 days. The conidial shape was straight to curve with light to deep brown colour. The number of horizontal and vertical separation in the conidia ranged from 3.00 to 6.00 × 1.00 to 2.00 with size from 11.20 to 39.20 × 4.76 to 11.43 µm. In pathogenicity test isolates also exhibited variations in size of the lesions (2.77 to 7.55 mm) produced on onion leaves. The results demonstrate existence of considerable variation in cultural, morphological, and pathogenic characters of A. porri isolates prevalent in Bangladesh environment.

In this paper, the design of concentric circular ring slot patch antenna with defected ground structure (DGS) is presented. The rectangular patch antenna is slotted with two concentric circular rings on radiating patch. The two diamond shaped patch is added to the microstrip-feed-line. The DGS is considered for obtain dual bands at 6.6 and 9.4 GHz with return loss − 14.7 and − 20.9 dB to operate for satellite communication and radar applications. The VSWR is less than 2 and axial ration is less than 3 dB for these two bands are obtained of proposed antenna. The surface current distribution is presented for analyzing the effect of the slots. It is observed that the simulation and measured values are having good agreement. [ABSTRACT FROM AUTHOR]

Geo-distributed network applications typically use relays to process and forward timely messages among clients. The state-of-the-art approaches greedily locate a relay that is closer to clients based on an overlay that favors neighbors in the immediate vicinity of the current node. Unfortunately, as clients are unknown a priori, the optimal relay is generally outside of the immediate vicinity of the current node. Consequently, the search process often terminates at a poor local minimum. In this paper, we address these challenges by designing and implementing a distributed relay-search system called MCR. In order to accurately locate a relay closer to clients, by observing that the latency space exhibits a proximity clustering phenomenon where nodes in the same cluster are typically within close proximity, we propose an overlay called MCRing that is aware of global proximity clusters. In order to scale well under dynamic relays, we maintain the proximity clusters via a gossiping-based clustering process. Furthermore, we propose a series of algorithms to accurately locate a relay that is closer to clients and satisfies the load constraints. We prove that the relay-search process achieves close to optimal results based on a doubling dimension-based analysis in an inframetric model. Finally, extensive evaluation via simulation and PlanetLab experiments shows that MCRing is able to locate near-optimal relays. [ABSTRACT FROM PUBLISHER]

Numerical studies were performed on natural convection heat transfer from radial heat sinks with perforated ring. The effects of perforation number (0–6), perforation diameter (0–3 mm), and perforation length (1.5–6 mm), and orientations angle (0–180°) on the thermal performance were investigated. The results show that radial heat sinks with a perforated ring obviously have better thermal performance than that with imperforated ring. Upwardly oriented radial heat sinks have the best thermal performance while sideward oriented radial heat sinks yield worst thermal performance. The geometric parameters of perforation is shown to affect the thermal performance of heat sink significantly at relatively higher heat transfer rate, especially for upward and sideward orientations. The thermal resistance of the radial heat sink with optimized perforated ring was shown to be less than that of imperforated ring by 17%, while reducing the mass of ring by up to 37%. This can be attributed to the unhindered natural convective flow through the perforation. [ABSTRACT FROM AUTHOR]

Twenty seven (27) isolates of Alternaria porri were isolated from diseased leaf samples collected from different onion growing regions of Bangladesh and characterized for cultural, morphological and pathogenic variabilities. A. porri colonies colony colour ranged between light to dark olivacious and grayish white with irregular, regular with concentric ring and regular without concentric ring shape. Margin of colonies were entire, irregular and wavy with effuse, fluffy and velvety texture. Isolates impregnated media with colour ranged between grey to brown on the reverse of the plates. Growth rate of isolates ranged between 2.433 and 3.950 mm/day with fast growth in isolate DSTR 02 and least in MMBH. Morphological variation in conidia production was between 7.720×10³ to 47.02×10³ per mm² with sporulation time 3.33 to 11.00 days. The conidial shape was straight to curve with light to deep brown colour. The number of horizontal and vertical separation in the conidia ranged from 3.00 to 6.00 × 1.00 to 2.00 with size from 11.20 to 39.20 × 4.76 to 11.43 μm. In pathogenicity test isolates also exhibited variations in size of the lesions (2.77 to 7.55 mm) produced on onion leaves. The results demonstrate existence of considerable variation in cultural, morphological, and pathogenic characters of A. porri isolates prevalent in Bangladesh environment. [ABSTRACT FROM AUTHOR]

Investigation and planning of future urbanization pathways necessitates knowledge and tools to better understand the physical spatial processes of urban expansion. In this study, the wave-shaped diffusion regularity of urban expansion in terms of the density of new urban land was detected and simulated with a Gaussian-based model, based on which the physical spatial process of urban expansion, as well as its long-term trends were characterized and understood. The Gaussian-based model provided a partitioning scheme to concentrically divide the urbanized areas of a given city into distinctive zones. Indices and methods were further developed to quantify compactness, rate, and development intensity of urban expansion processes. In particular, the model mathematically articulated how the macroscale urban form were invented from overlap of sequential physical spatial processes of urban expansion. The proposed model attained a fine fit with the density gradient of new urban land in 27 sample cities from 1990 to 2017, with an average R 2 value of approximately 0.87. The results revealed rapid urban expansion and path dependency in the compactness of urban expansion during this period. The concentric partitioning results in this study demonstrated tendency consistent with that reported in previous studies. The proposed model provides new insights into urban geography with a deeper understanding of the physical spatial processes associated with land urbanization • The physical spatial processes of urban expansion follow a wave-shaped regularity. • The regularity can be well represented by a Gaussian-based model. • The model provides a scheme for concentric partitioning of the urbanized areas. • Indices are developed for measurement of compactness and rate of urban expansion. • The model explains how the urbanized areas were created from sequential spatial processes of urban expansion. [ABSTRACT FROM AUTHOR]

In this study, the orientation effect on the thermal performance of radial heat sinks with a circular base, concentric ring, and rectangular fins were investigated experimentally and numerically. The effects of orientation angle with respect to gravity (0 ⩽ θ ⩽ 180°), Elenbaas number (0.5 < El < 50), and non-dimensional fins spacing (0.273 ⩽ s ∗ ⩽ 0.617) on Nusselt number are considered. Experimental results show that horizontally oriented radial heat sinks ( θ = 0° or 180°) have better thermal performance than vertically oriented radial heat sink ( θ = 90°). The present numerical model is shown to predict the experimental results well within error of 4%, and suggests that the inferiority of vertically oriented heat sink can be attributed to the existence of the concentric ring, which can shield the natural convective upward flow. The radial heat sink in orientation 0° is found to have slightly better thermal performance than that in 180° when s ∗ is relatively large, and vice versa. Based on the experimental and numerical results, a closed-form correlation with associated orientation effect factor is proposed for predicting Nusselt number, as a function of aforementioned nondimensional parameters. [ABSTRACT FROM AUTHOR]

This paper presents numerical and experimental studies on the heat transfer characteristics around a radial heat sink with a horizontal circular base, concentric ring, and rectangular fins that are subject to natural convection. An FVM (Finite Volume Method) numerical model was used to analyze the temperature and natural convection heat transfer on the surfaces of the radial heat sink for a wide range of geometric parameters. The effects of dimensionless fin length (0.40 ⩽ l ∗ ⩽ 0.53), dimensionless spacing between fins (0.127 ⩽ s ∗ ⩽ 0.288), and the Elenbaas number (0.5 < El < 50) on the Nusselt number of the heat sink were investigated. In order to support the numerical results, experimental study is performed. The experimental result indicates that the present numerical model predicts the Nusselt number well within a maximum error of 4%. Based on the numerical results, a generalized correlation for predicting the Nusselt number was developed as a function of the three aforementioned nondimensional parameters. This correlation can be widely utilized for predicting the thermal performance of radial heat sinks with concentric rings subject to natural convection. [ABSTRACT FROM AUTHOR]

We propose a new automatic method called the rotational pixel swapping (RPSW) method to detect circular features in binary images of remote sensing images. The method is based on a multiplication operation between the original image and the rotated images. We show that the RPSW selectively enhances rotational symmetric patterns and weakens nonrotational symmetric patterns, including noise components, without any noise reduction processes. The method can detect not only simple circles but also more complex circular features such as incomplete ring structures or several concentric rings. Furthermore, we demonstrate that the RPSW provides the stable detection of circular features such as terrestrial impact structures, which are irregular imperfect circular shapes, in binary images based on Earth-observation satellite images. The RPSW would provide a potential method of future surveys or statistical studies using huge data sets of multiband or hyperspectral images obtained by Earth-observation satellites. [ABSTRACT FROM PUBLISHER]

• A set of equations is proposed for the computation of the tail seal pressures. • Equations are proposed for the calculation of thrust jack geometrical quantities. • "Concentric" rings tend to a concentric position without distortion. • The position of "eccentric" rings is restrained at the expense of ring distortion. • Design guidelines for structural analysis of transient design situations are given. Despite growing evidence proving that sealing pressures and transverse jack forces are transient load cases relevant for concrete segmental lining (CSL) design, these TBM transverse actions are consistently omitted by current design guidelines. In this paper, the TBM transverse actions are examined in detail and a theoretical framework is proposed to help tunnel designers incorporate them into the basis of design and the analyses required for structural verification. The design guidelines are formulated starting with a set of equations for the computation of sealing pressures and the geometrical quantities governing the jack forces. The proposed calculation methods are deployed to classify and describe global construction scenarios of CSLs in transverse interaction with the TBM, including expected behaviour and damage modes. Guidelines for the definition of relevant transient design situations and subsequent engineering models are finally provided. [ABSTRACT FROM AUTHOR]

Plasmonic nanopatterned structures that can work as highly efficient surface-enhanced Raman scattering (SERS) substrates are presented in this study. A “coupled” concentric ring structure has been designed, fabricated, tuned, and compared to an “etched” concentric ring structure and plain gold film via SERS experiments. The proposed design gives Raman signal intensity 630 times larger than plain gold film and 8 times larger than an “etched” concentric ring structure. The surface plasmons were imaged with the fluorescence imaging technique and supporting numerical simulations were done. [ABSTRACT FROM PUBLISHER]

The inscription of Bragg gratings into the germanium-phosphorous co-doped rings of a photonic bandgap fiber with a ytterbium-doped core is reported. These cladding layers are observed to exhibit interesting modal properties, with each ring supporting near-degenerate modes that agree well with numerical modeling. Besides fiber laser applications, there are several potential sensing applications of gratings in such a fiber. [ABSTRACT FROM PUBLISHER]

We demonstrate the concept of multi-bits storage in concentric ferromagnetic rings fabricated using electron beam lithography and lift-off technique. At remenance, we observed that no two head-to-head or tail-to-tail domain walls exist at the same location in neighboring rings. Instead, they pin themselves with that of the opposite kind of the neighboring embedded ring, thereby minimizing the total free energy of the system. A unique arrangement of aligned alternating head-to-head and tail-to-tail domain walls in rings favoring antiparallel alignment of magnetization is observed at remenance. This results in the chirality of vortex configuration in each ring to be strongly dependent on its width and magnetostatic interaction with the neighboring embedded rings. The results are in good agreement with micromagnetic simulations. [ABSTRACT FROM AUTHOR]

In order to monitor electrical activity of the heart during daily life, we present an electrode of a medical instrument system which is able to measure the body surface potential difference by minimizing the electrode distance. The designed electrode is composed of concentric circles. It was made from the basis of the Laplacian equation, and implemented on PCB coated with gold. So that it does not cause the uncomfortable feeling of contact and possible skin troubles which are typical shortcoming of the conventional ECG measurement. The suggested method utilized three concentric circles on FR-4 substrate, so new amplifier design regarding measuring of small biological signal, is considered which has the characteristics of asymmetric input impedance since the area of concentric circular ring electrodes is not identical. Thereby, electrical activity of the heart was obtained successfully. However, its signal quality is a little bit degraded and the motion artifact still remains as a major problem as is in conventional electrocardiography measurement. Certainly stable measurement setup was needed to reduce the motion artifact originated from variation in static electricity between skin and electrode interfaces. [ABSTRACT FROM AUTHOR]

During apparent motion, spatially distinct items presented in alternation cause the perception of a visual stimulus smoothly traversing the intervening space where no physical stimulus exists. We used fMRI to determine whether the perceptual ‘filling-in’ that underlies this phenomenon has an early or late cortical locus. Subjects viewed a display comprised of concentric rings that elicited apparent motion (two concentric rings presented in alternation), flicker (the same rings presented simultaneously), or real motion. We independently localized the cortical regions corresponding to the path of apparent motion in early visual areas (V1, V2, VP, V3, V4v, V3A), as well as the human motion processing complex (MT+). Cortical activity in the path of apparent motion in early visual areas was similar in amplitude during both apparent motion and flicker. In contrast, cortical activity in MT+ was higher in amplitude during apparent motion than during flicker, but was lower in amplitude than during real motion. In addition, we observed overlap in the cortical loci of MT+ and the lateral occipital complex (LOC), a region involved in shape and object processing. This overlap suggests that these regions could directly interact and thereby support perceived object continuity during apparent motion. [Copyright &y& Elsevier]

We have studied structures where a concentric ring with an index higher than that of the cladding index is added to a conventional fiber core. The structure supports at least one additional symmetric mode with substantial power in the ring, besides the normal mode in the core. Within certain designed parameter regimes, the propagation constants of the lowest two symmetric modes cross at a certain wavelength. This is equivalent to saying that the LP01 mode can change from having more power in core to having more power in ring at a certain wavelength or vice versa. At this resonance, each of the two modes has substantial power in the core and the ring. This resonant nature of the structure creates a strong wavelength dependent mode field for LP01 and LP02 modes near the resonance wavelength. Filters based on this principle are demonstrated for the first time [ABSTRACT FROM PUBLISHER]

Rapid urbanization and land expansion persistently shrink urban green field, which accelerates soil sealing and land degradation. Spatio-tempral pattern analysis of green field caused by soil sealing contributes to its protection but quantitative tools are rare. Taking Shanghai-Hangzhou Bay Urban Agglomeration (SHBUA) as an example, we interpreted Landsat imagery into three categories: green filed (such as farmland, grass, forest etc.), gray field (impervious surface) and water bodies in 1994, 2003, 2009, and 2015. We first analyzed swallowed green field by soil sealing and then calculated density (proportion) of green field in concentric rings using gradient analysis. Results show that green field density increases slowly around the city center followed by a sharp increase from urban core areas to urban fringe, and then slowly increases again until at a stable level, presenting an S -shape overall. We proposed an S -shaped function that can fit the spatial gradient of green field density well in nine represented cities. We further compare spatial gradients of densities of green field and gray field. This study provides a quantitative tool to characterize the spatial distribution of green field within cities, which supports to find hotspots of green field loss due to soil sealing and further identify prior areas for green field protection. Unlabelled Image • We investigated spatial pattern of green fields in Shanghai-Hangzhou Bay Urban Agglomeration during 1994–2015. • Green field density in concentric rings increases with the distance to the city center. • We proposed an S-shaped function to fit the spatial gradient of green field density. • S-shaped function can help find hotspots and prior areas of green field protection. [ABSTRACT FROM AUTHOR]

In this paper, a refractive index sensor based on Stampfli-type photonic quasi-crystal with concentric ring microcavity is proposed. The variations of resonant wavelength and quality factor with the change of the width of concentric rings and the radius of air holes are researched. The transmission spectra of the sensor filled with analytes with different refractive index are detected, and a high sensitivity of 613 nm per refractive index unit (RIU), as well as a high quality factor of 79423, is obtained. This work will provide guidance for the application of photonic quasi-crystal microcavity in the field of optical sensing. • Refractive index sensor based on PQC with concentric ring microcavity is proposed. • A high sensitivity of 613 nm/RIU is reached. • A Q -factor of 79423 is obtained. • A FOM of 31872 is obtained. [ABSTRACT FROM AUTHOR]