Radial Position Research Articles

Anatomical Structure and Bending Properties of Calamus zollingeri

The relationship between the structure and mechanical properties of materials has been a hot topic. However, there is a lack of research on the relationship between the structure of rattan and its mechanical properties. This study investigated the anatomical structure and bending properties of Calamus zollingeri, a commercially important rattan species. Samples were collected from different radial positions of the stem and analyzed for their microstructural features and mechanical properties. The distribution and morphology of vascular bundles (VBs), parenchyma cells (PCs), vessels, and fibers were examined using light microscopy. Bending tests were conducted to determine the modulus of rupture (MOR) and modulus of elasticity (MOE). Stepwise linear regression analysis was employed to explore the relationship between structural features and mechanical properties. The results showed that the diameters, lengths and distribution densities of the vessel elements were 280.32 μm, 2163.56 μm, and 3.68 pcs/mm2, respectively; the double wall thickness, lumen diameter, diameter, length, length–width ratio were 7.55 μm, 4.30 μm, 11.85 μm, 1569.39 μm, and 134.08, respectively; the tissue ratios of the vessel elements, fibers, sieve elements, and PCs were 22.76%, 20.5%, 4.83%, and 51.87%, respectively. The MOR of C. zollingeri was 55.77 MPa, while the MOE was 2669.11 MPa. The MOR of C. zollingeri was mainly affected by a double wall thickness of fiber and the tissue ratio of PCs, while the MOE was mainly affected by a double arm thickness of fiber and the tissue ratio of the vessel elements. This research provides valuable insights into the structure–property relationships of rattan, which can inform its optimal utilization in various applications.

Steering Mechanism and Capability of Forced Steering Device for Low-Floor Light Rail Train

For 70% low-floor trains on the light rail lines in Changchun, a multi-linkage forced steering device (FSD) is developed aiming at relieving the independently rotating wheelset (IRW) excessive flange wear and improving IRW bogie system running safety on curve line. This FSD employs guiding mode of steering four independently rotating wheels separately in a two-axle bogie, that is, four FSDs are employed to work together to realize the steering of a two-axle bogie. One side of an FSD is connected to the axle of an independently rotating wheel while the other side is attached to the front or rear vehicle body. When train passes through curve, the yaw angle between the IRW bogie and the front or rear carbody drives the linkage system to rotate to guide the independently rotating wheel towards its radial position. The coupled vehicle-track dynamics model for a 6-module single-type low-floor light rail train is developed and simulations of the train passing through tangent and curved tracks with and without FSD proposed are carried out. The results indicate that the FSD can improve the IRW restoring capability on tangent track and curve negotiation performance on whether sharp, medium, or large curved track. For example, passing through a curve with a radius of 200[Formula: see text]m, the IRW friction work has the biggest drop by 62.07% and the wheelset attack angle is second with a reduction rate of 55.02%. Adopting of larger steering stiffness, smaller steering clearance, and lever ratio greater than the ideal value can guarantee the higher steering ability of FSD. Besides, lower longitudinal stiffness of the trailer primary suspension is recommended because it can also enhance the steering ability of the FSD.

Bubble characteristics in a novel microbubble gas-liquid-solid fluidized bed

The bubble characteristics are critical in gas-liquid-solid fluidized beds and microbubbles significantly enhance mass transfer in multiphase systems. In this work, a novel concept of microbubble gas-liquid-solid fluidized bed is proposed. Telecentric camera is employed to measure and analyze the microbubble characteristics including bubble size and gas holdup in this three-phase fluidized bed. Additionally, solid holdups in the fluidized bed are also examined. The results demonstrate that the bubble size adheres a lognormal distribution and is significantly influenced by superficial gas velocity. Bubble diameter exhibit a relatively uniform distribution in the radial direction. Bubbles exceeding than 1 mm substantially affect local gas holdup, and the microbubble flow promotes a more uniform distribution of local gas holdup in radial position. The average gas holdup deviation is less than 15 % compared to overall gas holdup obtained from pressure drop. Although microbubbles are more abundant, larger bubbles (> 1 mm) contribute more to solid particle fluidization. This paper introduces a methodology for assessing smaller-sized microbubbles in three-phase flow. The hydrodynamic analysis of the microbubble gas-liquid-solid fluidized bed establishes a foundational framework for enhancing gas-liquid mass transfer in fluidized bed.

The strength of an adhesive contact in the presence of interfacial defects

Adhesive contacts which possess a dominant stress concentration, such as at the contact edge in spherical junctions or at the detachment front in a peeling film, are well studied. More complex adhesive junction geometries, such as mushroom-shaped fibrils in bioinspired micropatterned dry adhesives, have exhibited a complex dependence of adhesive strength on the presence of interfacial defects within the contact. This has led to the emergence of statistical variation of the local behavior among micropatterned sub-contacts. In order to examine the interplay between geometry and interfacial defect character in control of the adhesive strength, the model system of a stiff cylindrical probe on an elastic layer is examined. Both experiments (glass on PDMS) and cohesive zone finite element simulations are performed, with analytical asymptotic limits also considered. The thickness of the elastic layer is varied to alter the interfacial stress distribution, with thinner layers having a reduced edge stress concentration at the expense of increased stress at the contact center. The size and position of manufactured interfacial defects is varied. It is observed that for the thickest substrates the edge stress concentration is dominant, with detachment propagating from this region regardless of the presence of an interfacial defect within the contact. Only very large center defects, with radius greater than half of that of the contact influence the adhesive strength. This transition is in agreement with analytical asymptotic limits. As the substrate is made thinner and the stress distribution changes, a strong decay in adhesive strength with increasing center defect radius emerges. For the thinnest substrate the flaw-insensitive upper bound is approached, suggesting that this decay is dominated by a reduction in the contact area. For penny-shaped defects at increasing radial positions, the adhesive strength for the thinnest substrates becomes non-monotonic. This confirms an intricate interplay between the geometry-controlled interfacial stress distribution and the size and position of interfacial defects in adhesive contacts, which will lead to statistical variation in strength when defects form due to surface roughness, fabrication imperfections, or contaminant particles.

INVESTIGATION OF PLASMA VISCOSITY AND MAGNETIC FORCES IN COAXIAL PLASMA DISCHARGE DEVICE

This paper investigates the axial plasma current sheath, PCS viscosity force, and its correlation with other magnetic forces acting on it at three different radial positions (2.625, 3.625, and 4.125 cm) within the annular space between the coaxial electrodes system of plasma discharge device (12 kV-56 kA) with positive central electrode. The rate of change of PCS momentum was also investigated at these axial and radial positions. The discharge processes are carried out with an argon gas pressure of 0.8 Torr. Experimental results of azimuthal magnetic induction as a function of axial and radial positions and Navier Stokes equation were employed to compute exactly, the rate of change of PCS momentum, axial magnetic force, magnetic pressure gradient force, and viscosity force.

Investigation on intermittent flow characteristics in horizontal pipe by visualization measurement method

Accurate measurement and prediction of the intermittent flow characteristics in horizontal pipes is important for constructing multiphase flow models and ensuring pipe flow safety. In this paper, a quantitative image post-processing technique for intermittent flow characteristics based on gray histogram image similarity is proposed, which can realize the measurement of slug frequency. In addition, the technique also has the ability to classify a large number of images, and can quickly find the elongated bubble head, liquid film area and liquid slug area of intermittent flow. On the basis of this technique, combined with image post-processing methods such as gas–liquid interface feature analysis, a set of intermittent flow image processing technique with perfect route is formed. Based on this post-processing technique, the similarity image oscillation trajectories of plug flow and slug flow are obtained. There are differences in the similarity image oscillation trajectories of the two intermittent sub-flow patterns, and the similarity image of the plug flow has an obvious platform period and trailing rising line, which can be used as a basis for the classification of the two intermittent sub-flow patterns. A correlation for predicting the slug frequency of intermittent sub-flow patterns is developed. The accuracy of this slug frequency prediction correlation can be improved by about 10 % compared to not dividing the sub-flow patterns. When the mixture Froude number Frm is less than 5.0, the radial position of the elongated bubble head decreases linearly as the Frm increases. When the Frm is greater than 5.0, the elongated bubble head oscillates near the middle of the pipe. Prediction correlations for the radial position of the elongated bubble head and the slug velocity are established separately, and the maximum error is ± 10 %. The modified mixed Froude number is proposed, and based on this, a new prediction model for the transition from plug flow to slug flow is established.

Magnetization States and Coupled Spin-Wave Modes in Concentric Double Nanorings.

Concentric multiple nanorings have previously been fabricated and investigated mainly for their different static magnetization states. Here, we present a theoretical analysis for the magnetization dynamics in double nanorings arranged concentrically, where there is coupling across a nonmagnetic spacer due to the long-range dipole-dipole interactions. We employ a microscopic, or Hamiltonian-based, formalism to study the discrete spin waves that exist in the magnetic states where the individual rings may be in either a vortex or an onion state. Numerical results are shown for the frequencies and the spatial amplitudes (with relative phase included) of the spin-wave modes. Cases are considered in which the magnetic materials of the rings are the same (taken to be permalloy) or two different materials such as permalloy and cobalt. The dependence of these properties on the mean radial position of the spacer were studied, showing, in most cases, the existence of two distinct transition fields. The special cases, where the radial spacer width becomes very small (less than 1 nm) were analyzed to study direct interfaces between dissimilar materials and/or effects of interfacial exchange interactions such as Ruderman-Kittel-Kasuya-Yoshida coupling. These spin-wave properties may be of importance for magnetic switching devices and sensors.

Radially patterned morphogenesis of murine hair follicle placodes ensures robust epithelial budding.

The bending of simple cellular sheets into complex three-dimensional (3D) forms requires developmental patterning cues to specify where deformations occur, but how positional information directs morphological change is poorly understood. Here, we investigate how morphogen signaling and cell fate diversification contribute to the morphogenesis of murine hair placodes, in which collective cell movements transform radially symmetric primordia into bilaterally symmetric tubes. Through live imaging and 3D volumetric reconstructions, we demonstrate that Wnt and Shh establish radial patterns of cell fate, cell morphology, and movement within developing placodes. Cell fate diversity at different radial positions provides unique and essential contributions to placode morphogenesis. Further, we show that downstream of radial patterning, gradients of classical cadherin expression are required for efficient epithelial rearrangements. Given that the transformation of epithelial discs into 3D tubes is a common morphological motif used to shape diverseorgan primordia, mechanisms of radially patterned morphogenesis are likely highly conserved across evolution.

Development of applicator to deliver hydrogel precursor powder for esophageal stricture prevention after endoscopic submucosal dissection

Esophageal stricture can be an adverse event following endoscopic submucosal dissection (ESD). Although particle-shaped materials could prevent post-ESD esophageal strictures, no applicator can efficiently deliver them to the ESD wound site. In this study, we developed an applicator to endoscopically deliver powders by combining polytetrafluoroethylene (PTFE) tubes and five types of catheter-tip nozzles with different structures fabricated using a 3D printer. The applicator with a T3S4 nozzle, with three and four holes on the tip and side, respectively, achieved lateral powder delivery from the endoscope catheter tip. The adhesion percentage to the ESD wound site, estimated using the esophagus mimicking model setup with tubes and wetted laboratory wipes, increased from 25 % (without the nozzle) to 55 % (with the T3S4 nozzle). In the computational fluid dynamics (CFD) simulation without a nozzle, the powder particles went straight, and hardly adhered to the ESD wound site. By contrast, the CFD simulation with the optimized T3S4 nozzle predicted that the adhesion percentage would increase by up to 55 %. Optimization of the axial position of the catheter affected the powder delivery efficiency, while optimizing the radial position and angle affected the homogeneity of powder delivery. An in vivo porcine ESD model using the developed applicator confirmed efficient and homogeneous powder delivery to the ESD wound site. These results suggest that the powder applicator development and CFD simulations are effective in treatments using endoscopic powder delivery.

MHD-induced beta limits in the Large Helical Device

Using the extended-magnetohydrodynamics code, M3D-C1, we perform a systematic numerical study of the effect of externally applied heating on the achievable plasma beta in a ten field-period heliotron. Heat sources of varying intensity are applied to a vacuum magnetic field that is representative of the standard configuration of the Large Helical Device, with R0=3.66 m, where R0 is the radial position of the magnetic axis in vacuum. As the system is driven to a state that is unstable to low-n magnetohydrodynamic (MHD) modes, nonlinear mode interactions lead to the formation of chaotic magnetic fields. With sufficiently strong heating, a collapse of the electron temperature profile is observed. This demonstrates the necessity of simulating the self-consistent evolution of plasma profiles, without imposing assumptions on the structure of the magnetic field, to accurately determine transport properties in stellarator plasmas. It also highlights the value of these advanced simulation capabilities for accelerating the development of high-performance stellarator operating scenarios.

Enhancement of beam quality and transmission using phase bunching in the central region of a cyclotron

Phase bunching in the central region of an azimuthally varying field (AVF) cyclotron contributed significantly to the improvement of the extracted beam quality. The phase bunching effect was demonstrated by measurements of the accelerated and extracted beam properties and by a theoretical analysis using the upgraded geometric trajectory model of the AVF cyclotron at the facility of Takasaki Ion accelerators for Advanced Radiation Application. The phase bunching effect on the beam extraction efficiency and emittance was estimated by a comparison between the 260 MeV 20Ne7+ beam of harmonic number h = 2 in the phase-bunching condition (PBC) and the 107 MeV 4He2+ beam of h = 1 in the non-phase-bunching condition (NBC). The PBC narrowed beam phase width and produced near-single-turn extraction, resulting in high extraction efficiency more than twice as high as that for the NBC. It was proved by beam current measurements. Reduction of the beam phase width was confirmed by the theoretical and experimental analysis of correlation between the radial positions at the phase-defining slits and the phase distribution of the particles passing through the slits. The theoretical analysis also showed that the beam emittance before extraction under the PBC is reduced to less than half of the NBC case. Furthermore, the measured normalized beam emittance in the horizontal direction after the extraction for the PBC was remarkably improved to 0.054π mm mrad nearly one-fourth of the emittance of 0.20π mm mrad for the NBC.

Toroidal Alfvén eigenmodes excited by energetic electrons in EAST low-density Ohmic plasmas

Abstract Operation in the quiescent regime with abundant trapped energetic electrons (EEs) has been achieved during the current flattop in EAST low-density Ohmic plasmas. This was facilitated by increasing the electron density to a specified level and subsequently reducing it slowly, resulting in the accumulation of a sufficient number of trapped EEs within the energy range of 150–250 keV. During the phase of decreasing electron density, toroidal Alfvén eigenmodes (TAEs) were observed to be excited by these EEs, with frequencies falling within the range of about 100–300 kHz. The experimental parameters were carefully set to satisfy the resonance conditions for TAE excitation by EEs, aligning well with predictions from ideal MHD theory. Statistical analysis indicated different density dependencies between the frequencies of TAEs and the Alfvén frequencies, due to their different radial excitation positions. The radial positions of the TAEs were found to be influenced by the energy distribution and the evolution of trapped EEs, which in turn were affected by the decay rate of electron density and loop voltage. Measurements of Hard X-rays (HXR) confirmed an energy distribution characterized by a “bump-on-tail” shape, with the TAEs observed near the energy bump. Theoretical considerations also demonstrate the possibility that the e-TAE can be driven unstable under this experiment condition even if the mode does not rotate in the electron-diamagnetic drift direction.

Inverse Estimation of Swirl Cooling Heat Transfer Coefficient

Swirl cooling is one of the most widely studied techniques in the field of heat transfer enhancement. This paper presents a novel, non-intrusive, and rather inexpensive inverse method to estimate the local heat transfer coefficient along the swirl chamber. First, the direct problem of two-dimensional heat conduction inside the chamber’s wall is solved numerically. The optimal number of sensors, their axial and radial positions, and other parameters concerning the inverse algorithm are determined using simulated experiments. The experimental setup is built based on these parameters. Transient temperature readings from several thermocouples embedded inside the chamber wall are fed to an inverse algorithm based on the conjugate gradient method. This algorithm takes advantage of an adjoint differential equation and the sensitivity differential equation to calculate the gradients and optimal step sizes, respectively. The local transient heat transfer coefficient is estimated for three Reynolds numbers along four straight lines parallel to the axis of the chamber.

Coupled influence of bypass ratio and throttling strength on characteristics and stall margin of variable-cycle fan

Three-dimensional numerical simulations of a first-stage fan in a variable-cycle engine (VCE) were performed to reveal the characteristics of the fan under different working conditions and the factors influencing them. The results indicated that several combinations of outer and inner bypass throttling could be used to achieve the same bypass ratio. To the best of our knowledge, this study is the first to establish the characteristic curves, which are dependent on the bypass ratio and throttling of the VCE fan. Consequently, the most suitable method of reducing the bypass ratio while ensuring a sufficient stall margin for the fan was to increase the outer bypass throttling and reduce the inner bypass throttling. Moreover, the only difference between the aerodynamic characteristic curves of the VCE fan for various bypass ratios at the same speed was the stall margin. An analysis of the flow field near the stall point revealed that the fan exhibited flow separation over an area with a large radius. Consequently, based on this flow separation, the reasons for the fan having different stall margins at different bypass ratios were explained. Furthermore, the axial position of the splitter was the primary factor affecting the throttling strength, whereas the radial position of the splitter determined the range of influence of throttling.

Wood density and chemical composition variation of Eucalyptus urophylla clone in different environments

Abstract Variability in Eucalyptus wood density and chemical properties is crucial to understanding important factors for the forest-based industry, such as sampling methods and wood suitability as raw material. This study aimed to evaluate the basic density and chemical composition of the radial positions of young wood from the Eucalyptus urophylla clone grown under different precipitation levels. Trees from E. urophylla clonal plantations were collected in Inhambupe, Jandaíra and Itanagra, Bahia State, Brazil. Trees’ basic density and chemical composition (total extractive, lignin, hemicelluloses and α-cellulose) were determined based on the basal log of each tree, at four radial positions (1, 2, 3 and 4). It was found that the basic density and α-cellulose of wood are influenced by the cambial age and the site rainfall. There was greater increase in sections close to the bark (positions 1 and 4) and in more humid environments (sites Itanagra and Jandaríra). This finding highlights the association between wood basic density and chemical composition, mainly in the holocellulose content.

Positional differences in the micro- and ultra-structural variations of ray parenchyma cells during the transformation from sapwood to heartwood.

Ray parenchyma cells are involved in the initiation of heartwood formation. The position within a ray influences the timing of ray parenchyma cell differentiation and function; however, there is little information concerning the positional influence on the cellular changes of ray parenchyma cells from sapwood and heartwood. In this study, radial variations in morphology, size, and ultrastructure of ray parenchyma cells were studied by combined transmission electron microscopy and optical microscopy. Results showed that cellular traits of ray parenchyma cells in Populus tomentosa were all affected by both radial position in the secondary xylem and position within a ray. Specifically, radial variations in cellular traits were more evident in isolation cells, which were not adjacent to vessel elements. Both cell length and cell width/length ratio of isolation cells were bigger than contact cells, which contacted adjacent vessel elements via pits. Moreover, the secondary wall thickening and lignification of contact cells developed in the current-year xylem, much earlier than isolation cells. Secondary walls in contact cells were in a polylamellate structure with a protective layer on the inner side. No alteration in the ultrastructure of contact cells occurred in the sapwood-heartwood transition zone, except that most contact cells died. By contrast, in the transition zone, isolation cells still lived. A thin secondary wall began to deposit on the thick primary wall of isolation cells, with two isotropic layers on the inner side of the primary wall and secondary wall respectively being characteristic. Meanwhile, starch grains in isolation cells were depleted, and dark polyphenolic droplets lost their spherical shape and flowed together. Furthermore, the intercellular spaces of isolation cells became densified in the transition zone. Overall, cellular changes suggested that the positional information of ray parenchyma cells appeared to be an important factor in the transformation from sapwood to heartwood. Unlike contact cells, isolation cells were more elongated, specialized in radial transport, had a delayed formation of secondary walls, and were involved in the synthesis of heartwood substances. Our result promotes the elucidation of the involvement of xylem rays in heartwood formation.

Temperature Field Measurements in Swirl Spray Flames Using Two-Line Planar Laser Induced Fluorescence Thermometry

Abstract This paper investigates the temperature fields in a centrally staged swirl spray combustor using two-line OH planar laser induced fluorescence (PLIF) thermometry at elevated inlet pressures and temperatures up to 0.62 MPa and 650 K. The pilot and main stages of the combustor were supplied with RP-3 kerosene. OH radicals were excited using the Q1(5) and Q1(14) transitions within the A2Σ←X2Π (1,0) band. Two laser excitation systems were operated simultaneously, where the two beams were spatially combined and separated by a small interval in time. The PLIF signals excited at the two wavelengths were captured by two identical sets of imaging system. The calibration coefficient needed for quantitative conversion from fluorescence ratio to temperature was determined based on results from independent coherent anti-Stokes Raman scattering (CARS) measurements. A joint threshold mask was developed to remove the noise and weak signals in the raw PLIF images. The high temperature zones in the temperature field were then obtained, and the pilot and main stage flames were identified. In addition, the radial position of the pilot flame showed marked variations at a nominally fixed condition. By extracting the radial profiles, a consistency between the peaks of PLIF intensity and temperature was found, suggesting that PLIF images could be a qualitative substitute for the high temperature zones in the temperature fields of these swirl spray flames. This study demonstrates the feasibility of temperature field measurements using two-line OH PLIF in aero-engine model combustors.

A numerical method for calculating the driven current of neutral beam injection in tokamaks

The current driven by neutral beam injection in tokamak is calculated, and the slowing-down distribution function of the fast ion is obtained by the backward Euler iteration method, including the pitch angle scattering collision. This study reveals that when the pitch-angle cosine is small, the trapped fast-ion current significantly contributes to the total driven current, particularly when the neutral beam is injected perpendicularly. In such cases, the current densities of passing and trapped ions are of the same order of magnitude, with the trapped fast-ion current contributing over 10% to the total neutral beam-driven current. This results in a parabolic profile of the total current in the radial direction, promoting the formation of a negative shear equilibrium structure in the core of the tokamak plasma. The numerical approach was validated against the NUBEAM code while considering electron shielding effects and applied to calculate the neutral beam-driven current in multiple tokamaks. The influence of pitch-angle cosine and neutral beam injection power on the driven current was studied at different radial positions.

Robotic Valve Turning with a Wheeled Mobile Manipulator via Hybrid Passive/Active Compliance.

This paper addresses the problems of valve-turning operation in rescue environments where a wheeled mobile manipulator (WMM) is employed, including the possible occurrence of large internal forces. Rather than attempting to obtain the exact position of the valve, this paper presents a solution to two main problems in robotic valve-turning operations: the radial position deviation between the rotation axes of the tool and the valve handle, which may cause large radial forces, and the possible axial displacement of the valve handle as the valve turns, which may lead to large axial forces. For the former problem, we designed a compliant end-effector with a tolerance of approximately 3.5° (angle) and 9.7 mm (position), and provided a hybrid passive/active compliance method. For the latter problem, a passivity-based force tracking algorithm was employed. Combining the custom-built compliant end-effector and the passivity-based control method can significantly reduce both the radial and the axial forces. Additionally, for valves with different installation types and WMMs with different configurations, we analyzed the minimum required number of actuators for valve turning. Simulation and experimental results are presented to show the effectiveness of the proposed approach.

Investigation of vaned diffuser endwall contouring technology for improving the stable operating range of a centrifugal compressor with an asymmetric volute

AbstractIn this study, nonaxisymmetric endwall contouring technology is employed as a passive control strategy to enhance the stable operating range of a centrifugal compressor with an asymmetric volute. The endwall contouring method is applied to the hub‐side wall of the vaned diffuser within a centrifugal compressor stage. Instead of utilizing a flat hub as the baseline diffuser, various diffuser configurations featuring hub‐side contoured endwalls are explored, with adjustments in the peak radial position and peak height of the convex and concave profiles. Numerical simulations are conducted to evaluate the performance of the centrifugal compressor stage with both the baseline and contoured vaned diffusers. The investigation explores the underlying flow control mechanisms and establishes the effective endwall contouring guidelines. The findings highlight the effectiveness of endwall contouring in enhancing the stable operating range of centrifugal compressors. Notably, a substantial enhancement of 15.1% in the stable operating range is achieved by employing the contoured diffuser with the peak radial position near the vane leading edge (LE) and the peak height at 20% of the vane height. The endwall contoured diffusers reduce the positive LE incidence angles to direct the fluid toward the suction side (SS), and increase the radial velocity near the SS to suppress the hub‐suction corner separations in the diffuser passages near the volute tongue. These improvements collectively contribute to the enhancement of diffuser flow characteristics. Finally, a set of effective endwall contouring guidelines is proposed to guide the endwall contouring design for enhancing the stable operating range of centrifugal compressors.