Annular Distribution Research Articles

Interannual variations in spring lightning activity and convective rainfall over South China during the TRMM era

The interannual variability of spring lightning activity over South China (SC) and its driving mechanism are examined using the Tropical Rainfall Measuring Mission (TRMM) satellite-estimated convective rain rate and merged lightning flash rate datasets together with atmospheric and oceanic reanalysis products over the TRMM period (1998–2014). SC is climatologically characterized by high lightning flash densities, strong convective rainfall, and large convective available potential energy (CAPE) during spring. The spring SC lightning activity (SCLA) has a strong year-to-year variability, and the standard deviation of flash rates shows a spatially coherent annular distribution centered over the Pearl River Delta. The interannual variations of spring SCLA are not only highly correlated with those of convective rainfall and CAPE, but also significantly correlated with El Nino–Southern Oscillation (ENSO). The anomalously frequent SCLA tends to follow El Nino events, while infrequent SCLA preferentially follows La Nina events. Composite analyses demonstrate that during spring for the more frequent SCLA cases, the upper tropospheric atmospheric response to El Nino-related sea surface temperature anomaly (SSTA) patterns leads to strong southwesterlies over SC in conjunction with tropical westerlies over the tropical Indian Ocean, forming a divergent environment over SC. The upper-level divergence is coupled with low-level moisture convergence, generating strong mid-tropospheric updrafts to lift more air parcels to reach their level of free convection, thereby producing stronger convection with frequent SCLA. In contrast, the anomalous circulation forced by La Nina-related SSTA patterns is conducive to suppressed convection over SC and infrequent SCLA.

A novel gradient composition spreading and nanolayer stacking process for combinatorial thin-film materials library fabrication.

A novel magnetron sputtering process is proposed to fabricate a combinatorial thin-film materials library with highly precise composition spreading. In order to produce a gradient composition spreading for a specific target, a moving shutter is used to cover the deposition substrate step by step with a fixed step-length. By rotating the substrate and repeating the step-by-step masked deposition with different targets in turn, a heterogeneous precursor structure is obtained with alternate stacking of different material layers, each of which is in a step-by-step wedge-shaped thickness cross section. By controlling the thickness of each layer at the nanometer scale, a multilayer structure is formed to facilitate the interlayer diffusion between different precursor layers. It may also define the boundaries of individual sample pixels, resulting in improved composition spreading resolutions for the prepared materials library. A combinatorial magnetron sputtering system is designed with reciprocating rectangular targets, a narrow slit between the substrate and the target, and a quartz crystal microbalance feedback to control the deposition uniformity, resulting in a variation better than 3% across a 76 × 76 mm substrate. Three individual deposition chambers are designed in an annular distribution with 90° angle between each other. Moreover, a step-by-step moving shutter and a rotating substrate holder are incorporated. Combinatorial materials libraries with more than 10 000 individual compositions could be obtained using this system. A Ti-Zr-Ni ternary alloy library was fabricated for demonstration in which the sheet resistance spreading diagram of the Ti-Zr-Ni library was studied as a function of the composition.

Interfacial current distribution between helium plasma jet and water solution

The plasma–liquid interaction holds great importance for a number of emerging applications such as plasma biomedicine, yet a main fundamental question remains about the nature of the physiochemical processes occurring at the plasma–liquid interface. In this paper, the interfacial current distribution between helium plasma jet and water solution was measured for the first time by means of the splitting electrode method, which was borrowed from the field of arc plasma. For a plasma plume in continuous mode, it was found that the mean absolute current distribution at the plasma–liquid interface typically had an annular shape. This shape could be affected by regulating the air doping from the surrounding atmosphere, the gas flow rate, the applied voltage and the conductivity of the water solution. However, only the air doping fraction and the water conductivity could fundamentally change the interfacial current distribution from the annular shape to the central maximum shape. It was deduced that a certain amount of ambient air doping (mainly N2 and O2) and a low conductivity (typically <300 μS cm−1) of the treated water were essential for the formation of the annular current distribution at the plasma–liquid interface.

Effect of Concentric Annular Gap Flow on Wall Shear Stress of Stationary Cylinder Pipe Vehicle under Different Reynolds Numbers

The tube-contained raw material pipeline hydraulic transportation technology is an optimization and improvement of traditional hydraulic capsule pipeline (HCP) transport. It has the advantages of lower resource consumption, environmental protection, and less demand for human resources and has the ability to directly transport solids, liquids, and gases. The cylinder pipe vehicle is the core component of tube-contained raw material pipeline hydraulic transportation; its motion characteristics and energy consumption are affected by wall shear stress. When the cylinder pipe vehicle is stationary, the annular gap flow will affect the wall shear stress. This paper studies the wall shear stress and annular flow field distribution of a stationary cylinder pipe vehicle under different Reynolds numbers. The results show that as the Reynolds number increases, both the wall shear stress and the annular gap flow velocity show a gradually increasing trend. The wall shear stress and the velocity of the annular gap flow show some correlation, but there are differences in the trend of axial and circumferential wall shear stress along the length of the cylinder pipe vehicle. The research in this article will further improve the theoretical system of hydraulic conveyance of barrel-loading pipelines and provide a theoretical basis for the realization of industrial applications as soon as possible.

Geomorphologic Characteristics of Sandspit from the Yellow River Estuary: Impact on Land Cover Classification

Liu, X.; Xu, Y., and Song, J., 2020. Geomorphologic characteristics of sandspit from the Yellow River estuary: Impact on land cover classification. In: Zheng, C.W.; Wang, Q.; Zhan, C., and Yang, S.B. (eds.), Air-Sea Interaction and Coastal Environments of the Maritime and Polar Silk Roads. Journal of Coastal Research, Special Issue No. 99, pp. 257–262. Coconut Creek (Florida), ISSN 0749-0208.It is of great importance to study the response of land cover classification to micro-geomorphic type, which is an important non-zonal environmental factor. In this study, digital elevation modeling and two pairs of synthetic aperture radar data captured by Landsat8 OLI in 2018 and Landsat5 TM in 2010 were used to interpret the relationship between the land cover classification and geomorphological type for sandspit from the Yellow River estuary, China. The results showed that water accounted for the largest proportion of the total study area (> 40%), followed by Tamarix–Suaeda (18.59%), naked tidal-flat (13.25%), Tamarix–Phragmites australis (9.70%), Suaeda (5.35%), Phragmites australis (4.34%), Spartina alterniflora (4.28%), and scattered manmade objects (1.74%). The vegetation communities of the sandspit in the Yellow River delta were affected by the dual effects of seawater and river water, and presented a concentric, annular distribution trend towards the sea. Plants such as Spartina alterniflora and Suaeda heteropera were affected by the ocean and were mostly distributed in the estuarine coastal area. Phragmites australis communities were greatly affected by the river, and were mostly distributed around the river banks and farther away from the coast.

Origin of Batch Hydrothermal Fluid Behavior and Its Influence on Nanomaterial Synthesis

Summary Batch hydrothermal reactor is known as a closed system, and what happens in this “black box” is mysterious. Now, by using the tendency of graphene oxide (GO) to align along the flow and the fixation effect of thermoset resin, the hydrothermal annular convection can be inferred from the axisymmetric poloidal structure and GO-assembled annular distribution. Temperature difference and geometric symmetricity of the reactor account for the annular convection, which is also found to be affected by solution viscosity and reactor parameters. Numerical simulations reproduce the annular convection and are used to investigate the parameter space beyond experiments. Plume flows occur at the bottom of the reactor due to flow instability. Irregular and intensive flow is against the synthesis of high-aspect-ratio nanomaterials and monolithic gels. It is noteworthy that large-scale batch hydrothermal synthesis may not be feasible for some nanowires, nanosheets, and particularly gels due to the non-negligible flow influence.

Annular Neighboring Points Distribution Analysis: A Novel PLS Stem Point Cloud Preprocessing Algorithm for DBH Estimation

Personal laser scanning (PLS) has significant potential for estimating the in-situ diameter of breast height (DBH) with high efficiency and precision, which improves the understanding of forest structure and aids in building carbon cycle models in the big data era. PLS collects more complete stem point cloud data compared with the present laser scanning technology. However, there is still no significant advantage of DBH estimation accuracy. Because the error caused by merging different point cloud fragments has not yet been eliminated, overlapping and inaccurate co-registered point cloud fragments are often inevitable, which are usually the leading error sources of PLS-based DBH estimation. In this study, a novel pre-processing algorithm named annular neighboring points distribution analysis (ANPDA) was developed to improve PLS-based DBH estimation accuracy. To reduce the impact of inaccurately co-registered point cloud fragments, ANPDA identified outliers through iterative removal of outermost points and analyzing the distribution of annular neighboring points. Six plots containing 247 trees under different forest conditions were selected to evaluate the ANPDA. Results showed that in the six plots, error reductions of 53.80–87.13% for bias, 38.82–57.30% for mean absolute error (MAE), and 27.17–56.02% for root mean squared error (RMSE) were achieved after applying ANPDA. These results confirmed that ANPDA was generally effective for improving PLS-based DBH estimation accuracy. It appeared that ANPDA could be conveniently fused with an automatic PLS-based DBH estimation process as a preprocessing algorithm. Furthermore, it has the potential to predict and warn operators of potential large errors during hierarchical semi-automatic DBH estimation.

Yb: YAG laser welding of Ti6Al4V sheet using conventional and annular power density distribution: microstructure mechanical properties relationship

Development of high power laser beams with increasing beam quality and decreasing purchase cost lead to a strong development of laser welding techniques. Narrow weld beads, high welding speed, and low heat input are the main advantages of this reliable and repeatable joining process. The aim of this study is to investigate properties of weld seam obtained by Gaussian and annular power distribution, on butt joints of 0.9 mm annealed Ti6Al4V sheet by mean of an experimental design varying power level, spot size and shape, welding speed, and face gaseous protection flow. Examined characteristics of the weld seams are geometrical (Fusion Zone FZ and Heat Affected Zone HAZ shapes and dimensions, defects like porosities, undercut and underfill, distorsions of welded plates), microstructural (FZ and HAZ nature and morphology) and mechanical (tensile test, hardness filiations). Major features concerning the use an annular power distribution concern the flawless weld seam geometry and fair mechanical properties, with relatively low levels of distortions due to residual stresses.

Laser Cutting with annular intensity distribution

An annular intensity distribution has been assumed theoretically with great potential to provide high quality improvements to the cut flank during laser cutting process. We introduce several optical concepts to realize an annular intensity distribution with a high-power laser beam, such as an optical fiber with an annularly formed fiber core, a diffractive optical element, and axicons. Furthermore, cutting experiments for an axicon telescope with stainless steel are presented. With a specific optical setup and appropriate cutting parameters, a burr free cut flank with a surface roughness comparable to the state of art could be achieved. By means of cut front analysis, we assume that the burr free cut flank is a result of an improved gas coupling and the change of cut front geometry at the bottom side of the sheet.

Drillstring Buckling Prediction and Its Impact on Tool-Joint Effects in Extended Reach Wells

The mechanism of buckling has been extensively studied in pipes and tubings. But these studies more often has been restricted to continuous or straight body pipes. In reality most pipes and other drillstring elements have end couplings or connections known as tool joint. Tool joint presence changes the annular geometry, hydraulics and stress distribution of the pipe or tubulars in the wellbore. Modelling drillstring in highly deviated wells with no regards to the tool joint effects has been a major source of error in many drilling mechanics analysis. This has often led to misleading information on buckling and bending of the pipe which could lead to drilling and completion problems and costly well interventions. Thus it becomes necessary to model tool joint effect in the drillstring as it is subjected to downhole forces and stresses. In this study, emphasis is made on the determination of tool joint effect on pipe buckling for highly deviated extended reach wells (ERWs). WellPlan T&D spreadsheet software was used for the simulation. The simulation was runned for pipe with tool joint and the same pipe with the tool joints removed. Results show that jointed pipes has similar buckling behaviour with continuous straight body pipes with buckling starting from sinusoidal buckling mode and gradually entering the helical buckling mode for both types of pipes. Furthermore, result revealed that tool joint presence increases the critical buckling force by an average of 28.9% for helical as well as (AWA) sinusoidal buckling modes.

Design of Photonic Crystal Fiber Capable of Carrying Multiple Orbital Angular Momentum Modes Transmission

For the traditional photonic crystal fibers with circular air holes, rectangular air holes are added to the fiber cladding. The periodic arrangement of the inner rectangular air holes allows the fiber structure to better match the annular mode field distribution of the vortex beam. The fiber structure was analyzed and calculated by COMSOL Multiphysics 5.4 finite element software, and the characteristics of fiber were analyzed, such as the dispersion, confinement loss, effective mode area and nonlinear coefficient. The results reveal that the photonic crystal fiber structure capable of carrying 50 orbital angular momentum (OAM) modes at the wavelength of 1.15 to 2.0 μm (850 nm). The effective refractive index difference Δneff between vector modes can reach 1 × 10-3, and larger difference can effectively separate the vector modes and improve the transmission performance of OAM modes. Moreover, the fiber has good performance, such as flat dispersion distribution of the low-order modes, low confinement loss below 10-9 dB·m-1, large effective mode field area and small nonlinear coefficient in the 850 nm wavelength range. Therefore, this fiber structure can be applied to the high-capacity communication system of fiber multiplexing OAM. In addition, the good characteristics of this fiber structure are of great significance for the transmission of vortex beam in fiber.

Control of laser-beam spatial distribution for correcting the shape and refraction of eye cornea

The results of calculation and development of a device aimed at forming a laser beam with an annular intensity distribution and spatial mode homogenisation, as well as approbation of this device for biological phantoms and eyes in ex vivo experiments with laser non-ablative correction of the cornea profile, are presented. The radiation intensities and thermal field distributions on the surfaces of a phantom and isolated rabbit’s eye are investigated. The absence of significant heating in the central region of eye is confirmed. It is shown that this device can be used for laser impact in order to change symmetrically eye’s refraction.

Development of a wellbore heat transfer model considering circulation loss

Well loss is a common and complex accident in drilling engineering. The wellbore temperature under lost circulation plays a very important role on safe drilling and affects rheology of fluid, wellbore pressure, well-wall stability, etc. At present, the study on wellbore temperature profile under lost condition is quite limited. And, factors that have obvious impact on the wellbore temperature distribution are neglected in the existing heat transfer model under lost circulation, which reduces the accuracy of simulated results. In this paper, a wellbore heat transfer model is developed to predict the wellbore temperature profile under the condition of lost circulation. The effects of drilling fluid lost into zone, complex casing programs, and heat sources on wellbore temperature under the condition of lost circulation are fully considered in the model. And, the model is solved by iterative method. Then, the model is validated by the measured temperature data and the existing model. Comparison results show that the simulated results by the model in this paper are more consistent with the true value after considering these factors. Last, case study is conducted under lost circulation condition. Some meaningful conclusions are listed below: (a) The annular fluid temperature near the wellhead is less than the fluid temperature inside the drill pipe under lost circulation; (b) Different from normal circulation, there is an inflection point on the temperature difference curve under lost circulation; (c) The number of inflection points on the annular fluid temperature distribution curve increases with the increase of loss zone number; (d) Under the same change of loss rate, flow rate, thermal conductivity of formation, and heat capacity of fluid, the variation range of fluid temperature at bottom-hole is greater than the variation range of fluid temperature at wellhead.

Rice granule epicapsular stars.

A 32-year-old male presented with vision of 20/20 in both the eyes. Right eye showed pigmented deposits on the anterior capsule of the lens [Fig. 1a and b] resembling rice granules [Fig. 1c]. As the deposits were not in the visual axis, patient was asked to follow-up regularly.Figure 1: (a) Diffuse slitlamp illumination of right eye showing annular distribution of pigmented stars. (b) Magnified picture of the pigmented stars on the anterior capsule resembling rice granules. (c) Rice granulesPersistent pupillary membrane (PPM) is a remnant of tunica vasculosa lentis and is of 3 types.[123] Type-1 variants are membranes that are attached to iris. Type-2 variants are membranes with iridolenticular adhesions also termed the epicapsular pigmented stars with “chicken track” like deposits.[4] These are pigmented dendritic iris stromal melanocytes deposited on the anterior lens capsule either singly or in clumps.[5] Type-3 variants are membranes attached to cornea. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

Numerical Analysis of Stress and Temperature Fields in a Composite Stratum Based on a New Method of Shield Construction for Safety and Environmental Protection.

Safety and environmental protection are key issues in shield construction. Due to wear, the cutter of a shield machine must be changed after a period of excavation. In order to realize the tool change operation of a shield machine at atmospheric pressure, a method of cutter head freezing of the shield machine is described in this paper. The finite element simulation method is used to analyze the construction of a shield machine with a frozen cutter head in a composite stratum. For a composite stratum with uneven hard and soft layers in a ratio of 1:1, the stress and temperature fields are analyzed, and the stress change around the hob is recorded. Through numerical simulation, the change of the temperature field around the shield machine is determined in real time. As time goes on, the temperature around the shield machine decreases, and the frozen range expands. When the temperature field in a specific point reaches a critical value, the temperature at that point will remain constant, and the stress field around the cutter head will also tend to become stable. The isothermal region of the soil presents an annular distribution, and the final temperature tends to be stable and gradually increase as the distance from the frozen cutter head increases. The final temperature of the monitoring area reaches a stable value corresponding to −26.5 °C, the axial depth of the frozen wall is more than 2.5 m, the minimum frozen radius is 3.2 m, the stress distribution around the cutter head is unbalanced, the maximum stress is measured in the hard rock layer, and the stress around the cutter head at the hob level indicates that tool change is necessary. Compared with the traditional method, the construction method of a frozen cutter head is more effective and more environmentally friendly. Further research will allow a broad application of this method in shield excavation in a composite stratum.

Stacking Faults and Growth Twins in Long‐Period Stacking‐Ordered Structures in Mg–Co–Y Alloys

Herein, by atomic‐scale high‐angle annular dark field scanning transmission electron microscopy, the structure, symmetry, and distribution of stacking faults (SFs) and growth twins in 12H, 15R, and 18R long‐period stacking‐ordered (LPSO) structures in Mg88Co5Y7 and Mg92Co2Y6 (at%) as‐cast alloys are characterized. The SFs or growth twins in LPSO structures are denoted as the faulted arrangement of n‐Mg components, and some of them possess inversion centers or mirror symmetry. The formation of SFs or growth twins in 15R and 18R structures depends on whether the sum of Mg layers in all the n‐Mg components of the defect is an even number or an odd number, whereas only SFs form in 12H structures. Various types of SFs or SFs of the same kind can distribute locally in the LPSO structures in Mg–Co–Y alloys, and then some other LPSO structures with a longer period are detected via orderly distribution of SFs.

Research of coherent edge radiation generated by electron beams oscillating free-electron lasers

We have studied far-infrared coherent radiation with S-band linacs at Laboratory for Electron Beam Re-search and Application (LEBRA) at Nihon University and at Kyoto University Free Electron Laser. We have already developed a couple of terahertz-wave sources based on coherent synchrotron radiation and coherent transition radiation, which have been applied to spectroscopic research. Moreover, we developed coherent edge radiation (CER) at the downstream bending magnets in the FEL sections. Because the edge radiation has an annular shape distribution characterized by the asymmetric first-order Laguerre-Gaussian mode, the CER can be extracted from an optical cavity of the FEL system without a diffraction loss of the FEL beam. The root-mean-squared bunch length of the electron beam was evaluated by measuring the CER spectra, which was about the same level as the FEL micropulse width. Although the infrared FELs at LEBRA had a long slippage length, the FEL energy became higher as the bunch length was shorter. The CER intensity can be a guidepost enhancing the FEL power because of the existence of their correlation.

Resistance ceramic-filled annular welding of thin steel sheets

To meet the requirements of automobiles for high-strength steel welding and thin-sheet welding, a composite ceramic-filled annular electrode (A-electrode) was designed by controlling welding energy distribution. By embedding a circular non-conductive ceramic rod in the center of a conventional copper electrode, the welding heat changed from centralization in the center of the nugget of traditional spot welding to a more dispersed annular distribution. As a result, an annular nugget that corresponds to the annular copper end face was formed. Given the energy dispersion, a higher current was required to bond the sheets by the A-electrode than that by a traditional electrode. However, the indentation depth on the surface of the nugget decreased effectively. The stress distribution indicated that the stress was concentrated at the edge of the nugget under the load, and the unconnected part in the middle did not affect the strength. The size of the annular nugget was designed by adjusting the structure of the A-electrode. The strength of the nugget could be improved by forming a large nugget area.

Orbital angular momentum of a laser beam behind an off-axis spiral phase plate.

Here we obtain a simple formula for the relative total orbital angular momentum (OAM) of a paraxial light beam with arbitrary rotationally symmetric complex amplitude, passed through an off-axis spiral phase plate (SPP). The formula shows that the OAM is zero if the incident light is bounded by a diaphragm, and the SPP center is outside it. Another consequence of the obtained formula is that if the incident light is limited by an annular diaphragm then the full angular momentum is the same, regardless of the position of the SPP center inside the shaded circle of the annular diaphragm. This means that it is more appropriate to illuminate the SPP by beams with an annular intensity distribution because, in this case, the inaccurate alignment of the SPP center and the center of the annular intensity distribution do not affect the total OAM of the beam. In addition, we obtain a formula for the OAM density of such a light beam in the initial plane. The experimentally measured OAM is in good agreement with that calculated by the obtained formula.

Application of biharmonic equation in impeller profile optimization design of an aero-centrifugal pump

Purpose The purpose of this paper is to improve the hydraulic efficiency without changing the overall dimension. The blade profile optimization design of the aero-centrifugal pump based on the biharmonic equation surrogate model has been studied. Design/methodology/approach First of all, Bezier curves and linear function are used to control the annular angle distribution and the stacking angle of blade profile under the MATLAB platform. Grid independence analysis has been studied to find the finest mesh scheme. After the precision comparison of test data and computation fluid dynamics 15 sets of design parameters are carried out as the boundary condition of the biharmonic equation. The efficiency surrogate model of the biharmonic equation is constructed via iteratively solving of a discrete difference equation. The other two surrogate models of response surface model (RSM) and radial basis function neural network surrogate model (RBFNNSM) are compared with the biharmonic equation surrogate model by the standard of modified complex correlation coefficient R2 and root mean square deviation (RSME). Finally, the artificial fish swarm algorithm has been used to find the global optimal design parameters with the objective function of highest efficiency. Findings The results show that the design parameters code conversion method can reduce the number of optimization parameters from five to three, makes the design space become a cube, and compared with RSM and RBFNNSM, the biharmonic equation surrogate model has higher precision with R2 is 0.8958, RSME is 0.1382. The final optimum result of AFSA is at the point of [1 −1 −1]. The internal flow field analysis shows that after optimization the outlet relative velocity becomes more uniform and the wake effect has been significantly decreased. The hydraulic efficiency of the optimized pump is about 59.45 per cent increasing 5.4 per cent compared with a prototype pump. Originality/value This study developed a new method to optimize the design parameters of aero-centrifugal pump impeller based on biharmonic equation surrogate model, which had a good agreement with experimental values within just 15 sets of the original design. The optimization results shows that the method can improve the hydraulic efficiency significantly.