Discontinuous Ring Research Articles

Low-profile pattern reconfigurable patch antenna with dual bands characteristic for 5G NR communication

Abstract In this paper, a low-profile antenna with characteristic of reconfigurable of dual bands’ pattern for 5G New Radio (NR) communication is proposed to mitigate the problems of signal fading and multipath propagation. The design incorporates a turnstile-shaped patch, a circular patch with etched rectangular slots and a discontinuous ring patch. The circular patch with etched rectangular slots and discontinuous ring patch are placed in the same plane to obtain dual band characteristic. The discontinuous ring patch works as a near-field resonant parasitic unit to improve the front-to-back ratio values at the resonance points and adjust the beam direction. Eight diodes are loaded to control the connection states of the rectangle slots on the circular patch. By combining an electric dipole formed by diode-controlled slot with a magnetic dipole formed by the turnstile-shaped patch, then a dual-band antenna with diverse patterns is designed. The measured results show that the designed antenna has dual-band characteristics and operates in the bands of 3.39–3.62 GHz and 4.77–5.01 GHz with peak gains of 3.6 dBi and 4.2 dBi, respectively. Furthermore, the measured radiation pattern results show that it is feasible to reconfigure the pattern in both bands simultaneously at 45° intervals.

Polystemma stevensii (Apocynaceae, Asclepiadoideae), a new species from Michoacán, Mexico

Polystemma stevensii, a new species from Michoacán, Mexico, is described and illustrated. It grows in tropical deciduous forest in the Balsas Depression at elevations from 350 to 750 m. Polystemma stevensii is similar to P. viridiflorum but differs by having a gynostegial corona with five lobes fused at the base to form a discontinuous flat ring (vs. not forming a discontinuous flat ring), an internal corona with two deltate lobes (vs. with one ligulate lobe), and globose style head (vs. flat style head). A distribution map of the new species and a key to determine the Polystemma species of Michoacán are provided. Following IUCN Red List guidelines, it is assigned a preliminary category of endangered, EN B1ab(i,ii,iii)+2ab(i,ii,iii). Polystemma now includes eight species, of which five are endemic to Mexico.

The Inter-Annual Growth Characteristics of Rhododendron spp. Shrubs in Mt. Halla, Jeju Island, Korea Based on Their Tree Rings

The Rhododendron spp. (R. yedoense and R. mucronulatum) at high elevations of Mt. Halla in Jeju Island are the dominant species in the shrubland. Despite the recent damage to their growth due to climate change and the spread of Sasa spp., these species have not yet been studied systematically in Korea. Therefore, the current study aimed to verify the effect of abiotic factors, e.g., temperature and precipitation, and the spread of Sasa spp. as a neighbor species on their growth based on ring-width measurement data. In addition, the death years were dated using the cross-dating method developed in dendrochronology by comparing the individual ring-width time series from dead Rhododendron spp. with the corresponding chronology established using living trees. For the study, disk samples were obtained from 11 and 10 living R. yedoense and R. mucronulatum, respectively, to establish tree-ring time series. To investigate the death years, six disk samples were also collected from each shrub species. The relatively high occurrence of missing or discontinuous rings is a characteristic of shrubs, which makes tree-ring analysis difficult. Through cross-dating, it was verified that the R. mucronulatum and R. yedoense have 4.3% and 5.3% missing and/or discontinuous rings (the total number of missing and/or discontinuous rings/the total number of tree rings), respectively. All dead shrubs were successfully dated based on synchronization of the individual time series with the corresponding chronologies established using the cross-dated time series; nine shrubs died in the 2010s and the other two shrubs in 1996 and 2001, respectively. Most deaths occurred when Sasa quelpaertensis dominantly occupied the study sites. From the analysis of the relationships between the residual chronologies and the bioclimate predictors (BioClim), only R. mucronulatum showed reliable correlations with the Bio5 (maximum temperature of the warmest month) as +0.28 (p < 0.05) and the Bio18 (precipitation of warmest quarter) as −0.33 (p < 0.05). This result means that summer temperature is a limiting factor for the growth of R. mucronulatum. Through this study, it was verified that Rhododendron spp. at high elevations in Korea can be used for research using tree rings.

Coplanar Discontinuous Transmission Line Feed for Phase Gradient Metasurface Antenna

The aim of this study is to efficiently excite the radiation of phase gradient metasurface (PGM), a novel coplanar discontinuous transmission line feed is proposed for reduction of the profile, where 12 uniform discontinuous rectangular rings form the feeding structure. The unit cells of PGM are symmetrically placed on both sides of this feed structure at the same layer, and they are close enough. The measurements agree well with those of simulations in the range of 10.48–11.18 GHz.

Analytical approach for segmental tunnels considering nonlinear longitudinal joints in soft soils

As a discontinuous ring structure, joints are the weakness of a tunnel lining, which have a significant influence on the tunnel deformations and internal forces. Since the deformations at the joints are discontinuous, joint behaviors are treated as nonlinear rotational springs. Besides, the tunnel-soil interactions are modelled as a series of radial and circumferential nonlinear Winker springs. Thereafter, an analytical approach based on the beam-spring model is proposed. The reliability of this method is verified with three cases available in the literatures. It indicates that the proposed method is reasonable to estimate the tunnel deformations. Furthermore, parametric studies are carried out to reveal the influence of the coefficient of earth pressure at-rest, the soil stiffness and local surcharge loadings on the tunnel responses. It has been shown that increasing the coefficient of earth pressure and soil stiffness is beneficial for reducing tunnel convergences. Under the earth pressures, cracks are most likely to appear at the crown, waist, and bottom of the tunnel. For the metro tunnel in Shanghai, when the relative local surcharge loading is larger than 0.3 (the corresponding convergence is about 14‰D, D is the tunnel external diameter), joints subjected to the negative moment are susceptible to reaching the ultimate state.

Integrated transcriptome and proteome analysis reveals brassinosteroid-mediated regulation of cambium initiation and patterning in woody stem.

Wood formation involves sequential developmental events requiring the coordination of multiple hormones. Brassinosteroids (BRs) play a key role in wood development, but little is known about the cellular and molecular processes that underlie wood formation in tree species. Here, we generated transgenic poplar lines with edited PdBRI1 genes, which are orthologs of Arabidopsis vascular-enriched BR receptors, and showed how inhibition of BR signaling influences wood development at the mRNA and/or proteome level. Six Populus PdBRI1 genes formed three gene pairs, each of which was highly expressed in basal stems. Simultaneous mutation of PdBRI1-1, -2, -3 and- 6, which are orthologs of the Arabidopsis vascular-enriched BR receptors BRI1, BRL1 and BRL3, resulted in severe growth defects. In particular, the stems of these mutant lines displayed a discontinuous cambial ring and patterning defects in derived secondary vascular tissues. Abnormal cambial formation within the cortical parenchyma was also observed in the stems of pdbri1-1;2;3;6. Transgenic poplar plants expressing edited versions of PdBRI1-1 or PdBRI1-1;2;6 exhibited phenotypic alterations in stem development at 4.5months of growth, indicating that there is functional redundancy among these PdBRI1 genes. Integrated analysis of the transcriptome and proteome of pdbri1-1;2;3;6 stems revealed differential expression of a number of genes/proteins associated with wood development and hormones. Concordant (16%) and discordant (84%) regulation of mRNA and protein expression, including wood-associated mRNA/protein expression, was found in pdbri1-1;2;3;6 stems. This study found a dual role of BRs in procambial cell division and xylem differentiation and provides insights into the multiple layers of gene regulation that contribute to wood formation in Populus.

Numerical simulation and simplified analytical model for the longitudinal joint bending stiffness of a tunnel considering axial force

AbstractAs a discontinuous ring structure, segmental longitudinal joints are a weakness of shield tunnels and play an important role in the determination of tunnel deformation caused by ground pressure. A longitudinal joint bending test is first carried out by employing a detailed 3D numerical model for the Shanghai Metro tunnel. This reveals that the joint stiffness varies nonlinearly with the axial force and bending moment. Based on numerical results, an analytical model for determining the joint rotational stiffness is provided, which takes the influence of the mechanical behavior of the concrete and steel bolts, the geometrical dimensions of the joint cross section and the subjected loads into account. Then, a simplified fitting equation is proposed, which has been verified by the experimental test results. This reveals that the results obtained from the proposed fitting equation are in good agreement with the experimental results before the joint reaches the limit state. Therefore, this proposed equation can be preliminarily adopted for the simulation of joint bending behavior and the determination of tunnel deformation in the tunnel design stage.

Morphological, magnetic and EPR studies of ZnO nanostructures doped and co-doped with Ni and Sr

Herein, were analyzed the effects of Sr and Ni addition on the morphological, electronic and magnetic properties of ZnO nanoparticles synthesized by the sol gel route. Morphological analysis showed agglomerated particles with nonuniform shapes (polyhedral, hexagonal and spherical) and the average size distributions were calculated counting more than 100 nanoparticles (sizes between 43 and 75 nm). For pure ZnO sample, the selected area electron diffraction (SAED) showed bright and concentric discontinuous diffraction rings, while the co-doped samples, presented patterns well-organized concentric circular rings, typical of reflection of regularly arranged atoms. The electron paramagnetic resonance (EPR) was employed to analyze the intrinsic defects due to the dopant inclusion. In addition, the EPR spectra were simulated using the spin quantum number (S = 1) for Ni2+ to understand the experimental results. Ni ions were used as a local probe in the comparative study by EPR, capturing subtle modifications in the zero-field interactions due to induced strain in the lattice. Microscopically the changes observed, through the EPR study, result from the reduction of the axial distortion of the ligand field and increasing in the distortion perpendicular to the principal axis. Magnetic study showed a typical significant diamagnetism at 300 K, while a paramagnetic contribution was more evident at 4 K. The work contributes to clarify the complex magnetic response in ZnO nanoparticles doped and co-doped with Sr and Ni.

A Long‐Lasting Auroral Spiral Rotating Around Saturn's Pole

AbstractThe main ultraviolet auroral emission at Saturn consists of multiple structures forming a discontinuous ring of emission around the poles, occasionally organized in a global spiral. We present continuous observation of an auroral spiral rotating at ∼85% of rigid corotation during several hours. Simultaneously, energetic neutral atom (ENA) emissions revealed a hot magnetospheric plasma population located in the same local time sector as the ends of the rotating spiral. Following plasma theory, we propose that pressure gradients induced by the energized plasma distorted the magnetospheric current system, resulting in the spiral morphology of the aurora. The rotating hot plasma was several times reenergized in the dusk sector during at least 2 days, generating a long‐lasting auroral spiral. The ultraviolet spiral, the ENA emissions, and the ions revealed by this multi‐instrument data set are three signatures of a magnetosphere‐ionosphere coupling current system and of the associated hot plasma population rotating around Saturn.

English

The wood of three Nigerian species of Strychnos Linn. growing in different ecological zones was studied. The transverse, transverse longitudinal and radial longitudinal sections of the wood were made with sliding sledge microtome. The wood was macerated to measure its fiber and vessel dimensions. The wood was diffusing porous and intraxylary phloem occurred in the three species. Interxylary phloem in discontinuous ring occurred in the xylem cylinder of Strychnos innocua Del. and Strychnos usambarensis Gilg. Parenchyma was paratracheal and formed aliform to confluent patterns in S. spinosa Lam. but scanty in S. innocua and S. usambarensis. Vessel elements occurred singly and in radial and tangential multiples of two to four. The fiber lumen dimension of S. spinosa had the least value while its fiber cell wall thickness also had the greatest value. In S. spinosa, alkaloids and sterols were detected in the leaves and stem extracts. Alkaloids were found in the leaves, stem bark and fruits of S. usambarensis. The micro morphological features in each species were useful in making them adapt to the climatic conditions of the ecological zones where they grow. Key words: Interxylary phloem, Intraxylary phloem, Strychnos spinosa, Strychnos innocua, Strychnos usambarensis.

The buckling strength of a steel containment vessel with discontinuous stiffening rings of a nuclear power plant

The buckling strength of a steel containment vessel with discontinuous stiffening rings of a nuclear power plant

Study on the tensile and fatigue properties of the heat-treated HIP Ti-6Al-4V alloy after ultrasonic surface rolling treatment

This paper was mainly study on the tensile and fatigue performance change of HIP Ti-6Al-4V alloy treated by heat treatment combined with ultrasonic surface rolling (USR). Based on the use of heat treatment process to improve the microstructure and increase the mechanical properties, then USR treatment was used to further refine the grains in material surface modification layer and increase the residual stress and microhardness. The results showed that the plastic deformation layer of material surface was comparatively thin, and had a poorer grain refining effect. The SAED had the discontinuous ring spot pattern. Compared with the cut sample, the compressive residual stress value was −724 ± 23 MPa and increased by 50%, surface roughness was reduced to 0.17 ± 0.025 μm and decreased by 74.6%, and surface microhardness were increased to 467 ± 7.4 HV and increased by 43.6%. Finally, the tensile and yield strength increased by 3.6% and 3%, and the rate of reduction in area and the elongation decreased by 12.9% and 3.4% respectively. The fatigue strength at the high-cycle mechanism changed from 530 MPa to 570 MPa. The fatigue lifetime was increased by several times at the cycle stress of 700 MPa, and the only initial point of fatigue crack was located at the subsurface of the sample. Therefore this method could effectively improve tensile strength, fatigue strength and fatigue lifetime of HIP Ti-6Al-4V alloy.

A polarization reconfigurable discontinuous ring dipole antenna

AbstractA circularly polarized antenna is realized using a discontinuous ring dipole. With the introduction of p‐i‐n diodes, it has been possible to achieve polarization reconfigurability in the antenna. The antenna is fed by a tapered feed line, which also acts as a balun and biasing structure. The sense of rotation of the electric field vector (left‐hand or right‐hand) can be controlled by switching the states of the diodes. An equivalent circuit of the antenna is proposed, which has been used to compute the input reflection coefficient of the antenna. The performance of the antenna is verified by comparing the simulated results with the measured results. It has been observed that the antenna has 8.56% overlapping CP bandwidth (a common bandwidth for |S11| ≤ −10 dB and axial ratio, AR ≤3 dB) from 5.03to 5.48 GHz. A measured gain of 3.61 dBic is obtained for all polarization states. The proposed antenna can be used for the 5.2 GHz Wi‐Fi application.

Microstructural analysis of pitchblende in the Miaoershan area using TEM lattice imaging

This paper aims to reveal the formation process of pitchblende by analyzing its microstructural features on the nanoscale and atomic scale. Herein, we selected pitchblende samples from drilling cores from the Miaoershan area, southern China, as the research objects. The microstructural features of pitchblende particle cores were analyzed using high-resolution transmission electron microscopy (HRTEM), electron diffraction, energy spectrum (EDS) and electron microprobe analysis (EMPA), combined with density functional theory calculations. The results of this study reveal that the pitchblende grain boundaries are not clear, as they exhibit a cloudy distribution and some preferred orientations under HRTEM. The selected area electron diffraction (SAED) analyses show discontinuous ring patterns that are coherent with the presence of a preferred orientation. The HRTEM results reveal that pitchblende is a complex aggregate composed of nanocrystals with a diameter of 3–7 nm and unit cell parameters of a0 = 0.556 nm. The elements in the pitchblende are characterized by an irregular and scattered distribution of Ca, As, S, Fe, Mn, and Si. We assume that the formation of pitchblende is related to hard-base fluid in a reduced environment containing As and S. We used density functional theory calculations to obtain the pitchblende crystal structure model and simulated the positions of the U and O atoms to provide a reference for further analysis of the pitchblende crystal structure. We conjecture that uranium ions of U4+, U5+ and U6+ may coexist in pitchblende (stoichiometry U3O7).

Multi-functional regulator MapZ controls both positioning and timing of FtsZ polymerization.

The tubulin-like GTPase protein FtsZ, which forms a discontinuous cytokinetic ring at mid-cell, is a central player to recruit the division machinery to orchestrate cell division. To guarantee the production of two identical daughter cells, the assembly of FtsZ, namely Z-ring, and its precise positioning should be finely regulated. In Streptococcus pneumoniae, the positioning of Z-ring at the division site is mediated by a bitopic membrane protein MapZ (mid-cell-anchored protein Z) through direct interactions between the intracellular domain (termed MapZ-N (the intracellular domain of MapZ)) and FtsZ. Using nuclear magnetic resonance titration experiments, we clearly assigned the key residues involved in the interactions. In the presence of MapZ-N, FtsZ gains a shortened activation delay, a lower critical concentration for polymerization and a higher cooperativity towards GTP hydrolysis. On the other hand, MapZ-N antagonizes the lateral interactions of single-stranded filaments of FtsZ, thus slows down the formation of highly bundled FtsZ polymers and eventually maintains FtsZ at a dynamic state. Altogether, we conclude that MapZ is not only an accelerator to trigger the polymerization of FtsZ, but also a brake to tune the velocity to form the end-product, FtsZ bundles. These findings suggest that MapZ is a multi-functional regulator towards FtsZ that controls both the precise positioning and proper timing of FtsZ polymerization.

Direct Interaction between the Two Z Ring Membrane Anchors FtsA and ZipA.

The initiation of Escherichia coli cell division requires three proteins, FtsZ, FtsA, and ZipA, which assemble in a dynamic ring-like structure at midcell. Along with the transmembrane protein ZipA, the actin-like FtsA helps to tether treadmilling polymers of tubulin-like FtsZ to the membrane. In addition to forming homo-oligomers, FtsA and ZipA interact directly with the C-terminal conserved domain of FtsZ. Gain-of-function mutants of FtsA are deficient in forming oligomers and can bypass the need for ZipA, suggesting that ZipA may normally function to disrupt FtsA oligomers, although no direct interaction between FtsA and ZipA has been reported. Here, we use in vivo cross-linking to show that FtsA and ZipA indeed interact directly. We identify the exposed surface of FtsA helix 7, which also participates in binding to ATP through its internal surface, as a key interface needed for the interaction with ZipA. This interaction suggests that FtsZ's membrane tethers may regulate each other's activities.IMPORTANCE To divide, most bacteria first construct a protein machine at the plane of division and then recruit the machinery that will synthesize the division septum. In Escherichia coli, this first stage involves the assembly of FtsZ polymers at midcell, which directly bind to membrane-associated proteins FtsA and ZipA to form a discontinuous ring structure. Although FtsZ directly binds both FtsA and ZipA, it is unclear why FtsZ requires two separate membrane tethers. Here, we uncover a new direct interaction between the tethers, which involves a helix within FtsA that is adjacent to its ATP binding pocket. Our findings imply that in addition to their known roles as FtsZ membrane anchors, FtsA and ZipA may regulate each other's structure and function.

Analysis of profile and morphology of colloidal deposits obtained from evaporating sessile droplets

We experimentally investigate the profile and morphology of the ring-like deposits obtained after evaporation of a sessile water droplet containing polystyrene colloidal particles on a hydrophilic glass substrate. In particular, the coupled effect of particle size and concentration are studied. The deposits were qualitatively visualized under an optical microscope and profile of the ring was measured by an optical profilometer. The profile of the ring resembles a partial torus-like shape for all cases of particles size and concentration. The cracks on the surface of the ring were found to occur only at smaller particle size and larger concentration. We plot a regime map to classify three deposit types - discontinuous monolayer ring, continuous monolayer ring, and multiple layers ring - on particles concentration - particle size plane. Our data shows a possible existence of a critical concentration (particle size) for a given particle size (concentration) at which the monolayer ring forms. For the larger particle sizes, the immersion capillary forces between the particles dominate, aiding the formation of a monolayer ring of the particles. We measure the width and height of the ring and show that they scale with particle concentration by a power law for the multiple layers ring. This scaling corroborates with an existing continuum based theoretical model. We briefly discuss the effect of the interaction of growing deposit with shrinking free surface on the ring dimensions and profile. The present results aid understanding of the ring formation process and will be useful in guiding the design of self-assemblies of the colloidal particles formed by the evaporating droplets.

Spontaneous morphology reconfiguration of luminescent CH3NH3PbBr3 perovskites from monodispersed nanocrystals to discontinuous rings by dewetting-triggered solute migration

Morphology engineering is vital for tuning electronic and optical properties of perovskite nanocrystals (NCs). Though many 1D, 2D and 3D perovskite NCs have been prepared, perovskite rings are not reported. This work reported the preparation of perovskite rings by a simple method of dewetting perovskite NCs solution on the glass slide. Our results indicate that perovskites NCs can change their morphology from the starting nano-sized spherical shape to intermediate molecules/ions and finally to micron-sized perovskite rings during the dewetting process. The alteration of NCs–molecules–rings is driven by the dewetting-induced alteration of solvent environment for perovskite from the initial insoluble mixture of N,N-dimethylformamide (DMF) and toluene (1:50 v/v), to intermediate soluble DMF and finally to the glass slide without solvent. During the decomposing process from starting NCs to molecules/ions, the original oleic acid ligands of perovskite NCs will be released. These oleic acid surfactants will form ligand-stabilized gas bubbles, which act as in situ templates for reshaping of perovskite ring shape from molecules/ions.

High frequency of discontinuous rings in evergreen and deciduous hardwood species in a temperate forest

Tree age derived from annual-ring counts provides fundamental information on forest stands and individual trees in temperate forests. However, discontinuous growth in the trunk may cause inaccuracies in annual-ring counts, and the effect of radial growth rate and interspecific differences on discontinuous ring formation have not been evaluated in the same forest stand. We investigated the occurrence of discontinuous rings at the base of 435 tree trunk disks of 16 evergreen and 15 deciduous hardwood tree species growing in a temperate forest of Japan. The effects of tree age and radial growth rate on frequency of discontinuous rings and their interspecific differences were evaluated by a generalized linear mixed-effect model. Discontinuous rings were observed in 29 of the 31 species in 330 individuals, which is about 75% of the total number of individuals examined. The number of discontinuous rings proportionally decreased with the growth rate and increased with the tree age. On the other hand, the effects of the growth rate were different among species. The majority of species at the study site contained frequent discontinuous rings in the trunk base. Annual-ring counts from a single core would lead to underestimation of tree ages in this case. Stem disks or increment cores taken in multiple directions at ground level would be useful for accurate estimation of tree age in temperate hardwood forests.

Margin of Safety Estimation of Tongue and Groove Joint of Rocket Motors with Discontinuous End Ring

Rocket motors are used worldwide in both upper and booster stages.Solid rockets can provide high thrust for relatively low cost. Considering the large size of solid motors, these motors are to be designed as segmented motor cases. Segmented motor cases have to be joined by segment joint. Segment joint with tongue and groove configuration provides performance reliability in effective sealing of joints. A tongue-and-groove arrangement employs a pressure-energized metal seal which expands radially when the cylinders are internally pressurized. The radial expansion enhances the sealing effect of the metal seal between the tongue and the groove. Metal end rings welded to the shell motor cases and shear pins for the final assembly provides the sealing. The load sharing among the pins depends on the presence of the slit in a ring, whole & pin dimensional clearances, internal pressure and friction between the metal end rings. Structural analysis of a discontinuous metallic segment ring and shear pins iscarried out in this study. Structural analysis is based on detailed solid model for the segment joint. The load augmentation in the shear pin near the discontinuity is worked out based on a load augmentation factor derived out of FE analysis. The study further extended to a deviation in a nearby hole / pin combination at the vicinity of the discontinuity and is presented in this paper.