Annular Structure Research Articles

Numerical investigation on natural convection heat transfer of the annular structure in heat exchangers and solenoids

In heat exchangers and heated solenoids, the annular structure is widely used and it often transfers heat through natural convection. So, the heat-transfer characteristics of the annular structure are numerically studied in the range of 10≤Ra≤5×105 in this paper. The chimney effect and the air-heating effect are investigated. When the combined effect of two is the strongest, the ratio of the average Nusselt number of the annulus to that of the cylinder reaches the maximum value of 1.019 and the thermal boundary layer is tangent to each other. By the research, the heat exchange efficiency is the worst in the position of θ=0° due to the air-heating effect when 10≤Ra≤102 meanwhile in the position of 278°≤θ≤285° for 103≤Ra≤5×105. At last, the Nusselt number correlation has been fitted: Nu¯=0.6398×Ra0.2205. The specific study of the heat transfer characteristics on the outer flow of the annulus and the correlating equation can provide guidance for the design of heat exchangers, solenoids, and enrich the basic research content of natural convection.

Recent Research Progress on Tropical Cyclone Structure and Intensity

ABSTRACT This article provides a balanced, brief review on the research progress in the area of tropical cyclone (TC) structure and intensity achieved in the past three decade. Efforts have been made to introduce basic concepts and new findings relevant to the understanding of TC structure and intensity in ways as simple and appreciate as possible. After a brief discussion on the axisymmetric and asymmetric structure of mature TCs, progress in our understanding of spiral rainbands, concentric eyewall cycle, annular hurricane structure, and the inner-core size of TCs is highlighted. This is followed by discussions on the maximum potential intensity (MPI) of TCs and factors that limit TC maximum intensity. Some important remaining issues that need to be studied and addressed in the near future by the research community are identified and briefly discussed as well.

Exceptional high thermal conductivity of inter-connected annular graphite structures

Based on the experimentally observed templating effects in CNTs containing carbon fibers, new types of inter-connected annular graphite structures are proposed and designed in order to significantly improve the cross-plane thermal conductivity of graphite. The calculations of the thermal conductivity of the newly designed structures were carried out by combining macroscopic continuous equations and microscopic molecular dynamic (MD) simulations. First, MD simulation was used to examine the influence of bending curvature on the in-plane thermal conductivity of a graphene sheet along and perpendicular to the rolling direction. Next, various types of annular graphite structures with single and inter-connected double/triple multi-layered graphite sheets were designed. Finally, finite element analysis was used to calculate the effective out of plane thermal conductivities of these structural models. The cross-plane thermal conductivity of a common graphite film is 2-3 orders of magnitude lower than its in-plane thermal conductivity, which strongly restricts its heat dissipation ability. However, the formation of annular graphite structures and the inter-connections of the outer layers lead to a dramatic improvement of effective out of plane thermal conductivity from 2.3 W m-1 K-1 to 799.8 W m-1 K-1 in this work, which is superior to common metal materials, especially considering the relatively lower density of carbon materials. These results would be valuable for designing and fabricating highly thermally conductive carbon materials for heat dissipation and temperature management.

Boxed Ring Resonator for Liquid Dielectric Constant Measurement

The present study describes a compact and low-cost microstrip based resonant sensor that is specially developed for measurements of dielectric constant for liquid and paste at a frequency of 2.45GHz. The sensor utilizes shielded, boxed microstrip annular ring resonator structure, enabling a simple method to place a sample of liquid to be measured. The Transmission Line Model (TLM) of the multilayer system is successfully developed. The inverse algorithm is used to calculate real (e’) and imaginary parts (e”) of the permittivity for the liquid sample with the inputs of the changes in the resonant frequency (fr) and the quality factor (Q). Experimental data is testified against the related theory and compared with the results obtained by other researchers. CST MWS simulation software is used for the optimization of the boxed annular ring and concentric ring resonator structure. The comparison is done for the annular ring and concentric ring resonator boxed structure. Annular ring resonator structure has better accuracy than concentric ring resonator structure. This measurement system indicates high potential towards the development of a portable technique for quality analysis of liquids.

GAG content, fiber stiffness, and fiber angle affect swelling-based residual stress in the intact annulus fibrosus.

Biological tissues with a high glycosaminoglycan (GAG) content have an excellent ability to swell by absorbing water molecules from the surrounding environment. Our recent work showed that anisotropy in tissue swelling depends on the fiber-network architecture, including fiber angle, fiber stiffness, and lamellae structure. However, that work did not evaluate the effect of in situ boundary conditions, such as the kidney-bean shape of the annulus fibrosus (AF), on swelling behavior. The biochemical composition of intact AF is inhomogeneous with respect to GAG composition, collagen fiber angle, and fiber stiffness. Moreover, the GAG content in the inner AF decreases significantly with degeneration. In this study, we investigated the role of GAG content, fiber angle, and fiber stiffness in AF swelling and residual strain development using a finite element model based on a human lumbar disk. Our results showed that the annular ring structure had a great impact on swelling by developing region-dependent compressive stress/stretch in the inner layers and tensile stress/stretch in the outer AF. Swelling-based residual stretch was comparable to experimentally measured values, suggesting an important role of tissue swelling in maintaining residual stresses. Moreover, GAG loss in the inner AF, as observed with degeneration, decreased circumferential-direction stress by over 65%. Homogeneous distributions of fiber angle and stiffness overestimated or underestimated AF swelling behavior, such as swelling ratio, circumferential/axial stretch, and fiber stretch/reorientation. These findings demonstrate the need to include native fiber architecture in finite element models, to accurately predict tissue failure, as well as to cultivate engineered disks.

A Dual-Band Printed Antenna Design Based on Annular Koch Snowflake Slot Structure

The design of a fractal based slot antenna, to serve the dual-band communication applications, is proposed in this paper. The structure of the proposed antenna is based on the Koch snowflake fractal geometry of the third iteration as applied to the outer and inner perimeters of an annular ring slot configuration. The antenna slot structure has been etched on one side of a substrate representing its ground plane, and a microstrip line feed is printed on the other side. The realized results proved that the proposed antenna could excite three resonant modes. The first one was assigned for the lower resonating band from (2.24–2.93) GHz, while the second and third modes have been merged forcibly to generate the upper resonating band from (4.48–5.54) GHz. In terms of the guided wavelength, λg, the resulting antenna has a compact size of 0.57λg × 0.57λg. The results reveal that the antenna yields two resonant bands with a significant extent of the frequency ratio. To improve the antenna performance at the two resonant bands, investigation of current density distributed on the surface of the antenna is conducted at selected frequencies within the swept range. With the aid of this study, it has been found that when applying a defected ground structure (DGS) on the antenna ground plane, it can be considered as a tuning means of the two resonant bands. Measured results carried out on two fabricated prototypes confirm those theoretically predicted.

Modulated Response of Subtropical Gyres: Positive Feedback Loop, Subharmonic Modes, Resonant Solar and Orbital Forcing

Evidence of long-term variability in the upper ocean has emerged for two decades. Most of the issues discussed raise a lot of questions. What is the driver of the decadal oscillation of rainfall in Europe that has been observed since the end of the 20th century? How to explain low-frequency variability as observed in the Atlantic Multidecadal Oscillation (AMO)? More generally, how does solar and orbital forcing occur during very long-term climate change? The observations suggest that both a positive feedback loop amplifies the effects of the insolation gradient on the climate system and a resonance phenomenon occurs, filtering out some frequencies in favour of others. Throughout this paper, some answers to these problems are given from a new concept based on the modulated response of subtropical gyres to solar and orbital forcing. Subtropical gyres turn out to be the main driver of long-term climate variability because they tightly control, via the western boundary currents, heat transport from the tropics into middle and high latitudes. Specifically, the theoretical foundations of long-period Rossby waves winding around the subtropical gyres are laid, suggested by the observations of persistent sea surface temperature anomalies at mid-latitudes. Multi-frequency Gyral Rossby Waves (GRWs) exhibit properties resulting from their annular structure and their coupling. Using a β-cone approximation, the momentum equations are solved in polar coordinates. The gradient β of the Coriolis parameter depends on the mean radius of the annulus and remains constant all around the latter. GRWs result from the variation in the Coriolis Effect with the mean radius of the annulus. The speed of the anti-cyclonically wind-driven circulation being higher than the phase velocity of cyclonically propagating GRWs, amplified forcing effects occur as well as resonances for periods consistent with the observations.

Diffraction-limited ring beam generated by radial grating

Laser beams with ring-shaped intensity distributions have attracted much attention for a wide variety of applications in science and technology. In these applications, commonly used techniques for generating ring-shaped beams involve use of optical elements such as spiral phase plates or axicons. However, the ring-shaped beams formed by these methods have non-diffraction-limited resolution because the practical numerical aperture of a ring-shaped beam is smaller than that of a Gaussian beam. This is due to a reduction of the effective numerical aperture of the propagating beam after passing through the element. To overcome the issue, we propose an optical element composed of a radial grating to obtain a diffraction-limited ring-shaped beam. We found that a key point for optimizing the diffraction-limited ring-shaped beam is fine-tuning of the phase distribution in the ring-shaped beam. In an experiment for femtosecond laser processing with a ring-shaped beam, we demonstrated that the debris on a morphological structure fabricated by single-shot irradiation was considerably reduced because the subsequent pulse did not destroy the melt-solidification structure. Furthermore, we demonstrated the fabrication of an annular structure by single-shot ring-shaped beam irradiation in water without any inhibitory influence due to laser-induced bubble generation.

CIRCOAST: a statistical hypothesis test for cellular colocalization with network structures.

MotivationColocalization of structures in biomedical images can lead to insights into biological behaviors. One class of colocalization problems is examining an annular structure (disk-shaped such as a cell, vesicle or molecule) interacting with a network structure (vascular, neuronal, cytoskeletal, organellar). Examining colocalization events across conditions is often complicated by changes in density of both structure types, confounding traditional statistical approaches since colocalization cannot be normalized to the density of both structure types simultaneously. We have developed a technique to measure colocalization independent of structure density and applied it to characterizing intercellular colocation with blood vessel networks. This technique could be used to analyze colocalization of any annular structure with an arbitrarily shaped network structure.ResultsWe present the circular colocalization affinity with network structures test (CIRCOAST), a novel statistical hypothesis test to probe for enriched network colocalization in 2D z-projected multichannel images by using agent-based Monte Carlo modeling and image processing to generate the pseudo-null distribution of random cell placement unique to each image. This hypothesis test was validated by confirming that adipose-derived stem cells (ASCs) exhibit enriched colocalization with endothelial cells forming arborized networks in culture and then applied to show that locally delivered ASCs have enriched colocalization with murine retinal microvasculature in a model of diabetic retinopathy. We demonstrate that the CIRCOAST test provides superior power and type I error rates in characterizing intercellular colocalization compared to generic approaches that are confounded by changes in cell or vessel density.Availability and implementationCIRCOAST source code available at: https://github.com/uva-peirce-cottler-lab/ARCAS.Supplementary information Supplementary data are available at Bioinformatics online.

Design of a Multimode UWB Antenna Using Characteristic Mode Analysis

In this communication, a low-profile ultrawide band (UWB) antenna is designed, fabricated, and measured for TV white space devices (TVWSDs). Starting from a simple annular ring, the proposed design procedure is guided by the characteristic mode analysis. First, a closed-form estimation to the resonant frequencies of the first two characteristic modes for the annular ring structure is provided. Then, the annular ring is modified to introduce more characteristic modes resonating within the interested spectrum. To excite these modes and to achieve a wideband antenna covering the whole ultrahigh frequency (UHF) TV spectrum, the feeding structure is also carefully designed and refined. Finally, a prototype is fabricated and measured to verify its UWB performance, and radiation patterns at different frequencies are presented to prove the switching of dominating resonating modes. The analyses and performance evaluation show that the proposed antenna is a strong contender to be used for TVWSDs. Furthermore, thanks to the simplicity of tuning and controlling modal resonant frequencies, this procedure can be flexibly applied to various antenna designs.

Multidecadal Fluctuation of the Wintertime Arctic Oscillation Pattern and Its Implication

The multidecadal fluctuations in the patterns and teleconnections of the winter mean Arctic Oscillation (AO) are investigated based on observational and reanalysis datasets. Results show that the Atlantic center of the AO pattern remains unchanged throughout the period 1920–2010, whereas the Pacific center of the AO is strong during 1920–59 and 1986–2010 and weak during 1960–85. Consequently, the link between the AO and the surface air temperature over western North America is strong during 1920–59 and 1986–2010 and weak during 1960–85. The time-varying Pacific center of the AO motivates a revisit to the nature of the AO from the perspective of decadal change. It reveals that the North Pacific mode (NPM) and North Atlantic Oscillation (NAO) are the inherent regional atmospheric modes over the North Pacific and North Atlantic, respectively. Their patterns over the North Pacific and North Atlantic remain stable and change little with time during 1920–2010. The Atlantic center of the AO always resembles the NAO over the North Atlantic, but the Pacific center of the AO only resembles the NPM over the North Pacific when the NPM–NAO coupling is strong. These results suggest that the AO seems to be fundamentally rooted in the variability over the North Atlantic and that the annular structure of the AO very likely arises from the coupling of the atmospheric modes between the North Pacific and North Atlantic.

Wave propagation in compact, thin-walled, layered, and heterogeneous structures using variable kinematics finite elements

ABSTRACTThe article investigates wave propagation characteristics for a class of structures using higher-order one-dimensional (1D) models. 1D models are based on the Carrera Unified Formulation (CUF), a hierarchical formulation which provides a framework to obtain refined structural theories via a variable kinematics description. Theories are formulated by employing arbitrary expansions of the primary unknowns over the beam cross-section. Two classes of beam models are employed in the current work, namely Taylor Expansion (TE) and Lagrange Expansion (LE) models. Using the principle of virtual work and finite element method, the governing equations are formulated. The direct time integration of equation of motion is carried through an implicit scheme based on the Newmark method and a dissipative explicit method based on the Tchamwa–Wielgosz scheme. The framework is validated by comparing the response for the stress wave propagation in an isotropic beam to an analytical solution available in the literature. The capabilities of the proposed model are demonstrated by presenting results for wave propagation analysis of a sandwich beam and a layered annular cylinder structure. The ability of CUF models to detect 3D-like behavior with a reduced computational overhead is highlighted.

Tricuspid valve imaging.

The right ventricle and tricuspid valve (TV) have long been neglected by cardiologists. Functional tricuspid regurgitation (TR) is nowadays the most common cause of severe TR and is emerging as a prognostic factor in many heart diseases. A multimodality imaging approach is fundamental for defining the pathophysiology of TR, using both two-dimensional and three-dimensional echocardiography, as well as CT scan. In particular, 3D echocardiography can characterize TV apparatus and tricuspid annulus; CT offers complementary information about annular structure, and its relationship with the right coronary artery. The following review will describe TV anatomy, define transthoracic and transesophageal echocardiographic views for evaluating TV morphology, function and TR grading with some clues on interventional perspectives.

Circular RNAs and exosomes in cancer: a mysterious connection.

Circular RNAs (CircRNAs) are a type of non-coding RNAs (NcRNAs) with a closed annular structure. Until next-generation sequencing (NGS) is developed, the misunderstanding of circRNAs 'splicing error' has changed, and the mysterious veil of circRNAs has been revealed. NGS provides an approach to investigate circRNAs. Many scholars point out that circRNAs may play an important role in many diseases, especially cancer. At the same time, exosomes, as a kind of extracellular vesicles loaded with many contents, are a hotspot in recent years. They can act as 'messengers' between cells, especially in cancer. Lately, it is interesting circRNAs are enriched and stable in exosomes, also called exo-circRNAs, and there have been several articles on circRNAs associated with exosomes. In this review, we summarize the characteristics of circRNAs, especially its main functions. Then, we briefly introduce exosomes and their function in cancer. Finally, the known relation between circRNAs and exosomes is discussed. With further researches, exo-circRNAs may be a novel pathway for cancer diagnosis and targeted therapy.

Experimental study on NOx emissions of pulverized bituminous coal combustion preheated by a circulating fluidized bed

This study investigated nitrogen oxide (NOx) emissions of pulverized coal combustion preheated by a circulating fluidized bed (CFB). During the test process, high-temperature fuel preheated in a CFB was burned in a down-fired combustor (DFC). The effect of air distribution on NOx emissions was studied in the DFC, including three types of secondary air nozzle structures, five secondary air ratios, and three tertiary air position arrangements. Under stable conditions, the conversion ratio of fuel-nitrogen to N2 in the CFB was 41.4%, which resulted in lower NOx emissions in the platform. In this study, secondary air could be injected into the combustor at the top (annular) or through the side wall (circular) of the DFC, both with high combustion efficiency. This means that the secondary air is completely separated from the burner, and burner structure is greatly simplified. NOx emissions from secondary air nozzle structures of center, annular, and circular ports were 565.66, 345.45, and 220.38 mg/Nm3 (@6% O2) respectively. NOx emissions initially decreased then increased with increases in secondary air ratio with the annular nozzle structure. NOx emissions could be further inhibited by rationally arranging tertiary air positions.

Layer structured bismuth selenides Bi2Se3 and Bi3Se4 for high energy and flexible all-solid-state micro-supercapacitors

In this work, bismuth selenides (Bi2Se3 and Bi3Se4), both of which have a layered rhombohedral crystal structure, have been found to be useful as electrode materials for supercapacitor applications. In a liquid electrolyte system (6M KOH), Bi2Se3 nanoplates exhibit much better performance as an electrode material than Bi3Se4 nanoparticles do, delivering a higher specific capacitance (272.9 F g−1) than that of Bi3Se4 (193.6 F g−1) at 5 mV s−1. This result may be attributed to the fact that Bi2Se3 nanoplates possess more active electrochemical surfaces for the reversible surface redox reactions owing to their planar quintuple stacked layers (septuple layers for Bi3Se4). To meet the demands of electronic skin, we used a novel flexible annular interdigital structure electrode to support the all-solid-state micro-supercapacitors (AMSCs). The Bi2Se3 AMSC device delivers a much better supercapacitor performance, exhibits a large stack capacitance of 89.5 F cm−3 at 20 mV s−1 (Bi3Se4: 79.1 F cm−3), a high energy density of 17.9 mWh cm−3 and a high power density of 18.9 W cm−3. The bismuth selenides also exhibit good cycle stability, with 95.5% retention after 1000 c for Bi2Se3 (Bi3Se4:90.3%). Clearly, Bi2Se3 nanoplates can be promising electrode materials for flexible annular interdigital AMSCs.

The higher grain production, the more social deprivation? A case study of Henan province in traditional agricultural areas of China

This paper examines the spatial-temporal dynamics of inequality from the perspective of social deprivation in the context of continuous growth of grain production using national census data from 2000 and 2010 for Henan province, China. Our analytical results show an overall level of social deprivation that is high and a widening social deprivation gap at the county level. The social deprivation shows great spatiotemporal heterogeneity, the higher deprived counties are mainly distributed in central and eastern Henan province, while counties with lower social deprivation are clustered in northwestern regions, formed a belt-shape spatial differential between the south (higher deprived counties clustered) and northwest (low deprived counties clustered) Henan in 2000, and changed toward a core-periphery semi annular spatial structure in 2010, the low deprived counties surrounded by high deprived counties. The social deprivation shows a “west low and east high” spatial pattern, similar to the grain production in Henan province. Socioeconomic development level was low in most counties in Yudong plain despite of keeping the continuous increase of grain production, meaning the higher grain output did not result in the more social development expected in Chinese traditional agricultural areas, and the regional disparity is expected to increase in the near future if development conditions are not changed, which could inspire more targeted rural governance options.

Polymer Flooding Separate Injection and High Efficiency Measurement and Adjustment Technology

Daqing Oilfield is the largest onshore oil field in China. Polymer flooding plays an important role in the development of Daqing oil field, producing more than 10 million tons of oil for 11 consecutive years. If the injection is not carried out separately, polymer solution will advance along the high permeability layer, which will lead to the serious ineffective and low efficiency cycle, and reduce the production degree of the low and medium permeability layers, which will affect the overall development effect of polymer flooding. Therefore, stratified injection must be carried out, and a new type of delamination injection process string should be developed.1 The whole process integrated separate injection column was designed. The throttle element adopted the streamline annular pressure reducer structure. When the polymer solution passed, the molecular chain expanded and contracted, forming the effective throttling pressure difference and the flow rate 70m3/d. The maximum throttling pressure difference can reach 2.5 MPa, which can effectively control the injection amount into the high permeability layer and improve the production degree of the reservoir. The structural design of streamline ring pressure reducer can effectively control the degradation of polymer solution and reduce the viscosity loss rate from 12.3% to 8%, which ensures the maximum economic benefit of injecting polyacrylamide dry powder. The oil displacement effect of polymer solution is improved effectively. Developed a complete set Electric direct and high efficiency measuring and adjusting technology are used in this paper. From the manual to the cable controlled direct reading mechatronics, the injection test is developed from the manual trial to the cable controlled direct reading era. This technique has been applied in 6464 wells in Daqing Oilfield. The success rate of one salvage operation has been raised from 75% to 96.4% and the testing time of the 3-5 interval wells has been reduced from 5.2 days to 2.5 days, and the injection profile has been obviously improved. The effective production thickness ratio is increased from 62.8% to 74.7%, the oil production ratio is increased from 52.1% to 68.7%, and the oil recovery factor is increased by 2 percentage points. It is especially suitable for the old oil field to enter into the high water cut development. Effective technology for further improving oil recovery after stage.

Investigation of the Effect of Er:Cr:Ysgg Laser 2780 nm in Comparison with xp-Endo Finisher on Root Canal Dentin Permeability and Smear Layer Removal: An In Vitro Study

The aim of this study was to assess the effect of Er:Cr:YSGG 2780nm laser in comparison with Xp-endo Finisher in elimination of smear layer in terms of root canal dentin permeability and SEM analysis. Method: twenty-eight single-rooted extracted lower premolars were instrumented up to size X4 (protaper Next, Dentsaply) and divided into two groups according to the irrigation system, first group activated by Xp-endo Finisher and second one by Er:Cr:YSGG laser 2780 nm, pulsed mode, 1.25 W. Afterward, the roots were made externally impermeable, filled with 2%methylene blue dye, divided horizontally into three segments representing the apical, middle, and coronal thirds then examined under stereomicroscope. Using analytical software, the root section area and dye penetration area were measured, and then, the percentage of net dye penetration area was calculated. Moreover, scanning electron microscope investigations were accomplished. Results The non-parametric Mann-Whitney U test was done and showed a highly significant difference between the two experimental groups over the three root thirds. Dye penetration in Erbium laser group was significantly higher over the whole root length compared to other group. Scanning electron micrographs of Erbium laser group showed a distinctive removal of smear layer with preservation of the annular structure of dentinal tubules, while Xp-endo finisher group result in uneven removal of smear layer, and the dentinal tubules appear in sickle shape which indicate that they are partially opens especially in the apical third.

Mechanics modelling of fern cavitation catapult

Cavitation is often regarded as a failure mode in soft materials. An intriguing phenomenon has been recently discovered that fern sporangium can take advantage of drying-induced cavitation instability in annulus cells to disperse spores at an extraordinarily high acceleration. Briefly, the decrease of environmental humidity causes continuous bending of the sporangium and growth of cavities inside the annulus cells, with the elastic energy accumulated in sporangium walls. When the humidity is lower than a critical value, the cavities suddenly expand dramatically inside the cells, causing a quick release of the elastic energy stored in the annular structure. As a result, like a catapult, the sporangium snaps back and ejects the seeds at a high speed. Motivated by the observation, in this article, we study cavitation instability in a similar structure as the sporangium. To simplify the problem, in our model, the mechanics of cells in the sporangium are described by the polymer gel model, while the sporangium wall is modelled as a hyperelastic material. When the environmental humidity is lower than a critical value, through energetic analyses, we can predict the cavitation catapult phenomenon using the model. We hope that our study in this article can provide useful insights into the bio-inspired design of structures which can take advantage of cavitation instability in soft materials.