Radial Splitting Research Articles

Topology characteristics of liquid ammonia swirl spray flame

The utilization of liquid ammonia in gas turbines can reduce energy loss and start-up time. However, the flash boiling phenomenon and the high latent heat of liquid ammonia make the spray flame difficult to stabilize. Increasing the preheated air temperature or adding a small amount of hydrogen as a piloted fuel are considered as effective methods to enhance the stability. To understand the flame topological structure, simultaneous Mie scattering and planar laser-induced fluorescence of OH (OH-PLIF) techniques were used to visualize the liquid ammonia spray structure and flame region information. Results show that the liquid ammonia swirl spray flame exhibits the flame topological structure of distinct zoning characteristics, including the droplet zone, the mixing zone, and the flame zone. Increasing the preheated air temperature accelerates the evaporation of liquid ammonia, leading to an increase in the local equivalence ratio and radial flame splitting. At lower air temperature conditions, increasing the hydrogen blending ratio has minimal impact on the flame topological structure. However, at higher temperature conditions, hydrogen blending significantly promotes reaction intensity upstream and reduces the flame lift-off height, which makes the mixing zone smaller. In general, to achieve a better flame stability effect, the two factors need to be reasonably matched, which has important reference value for the development of liquid ammonia fueled gas turbine combustors.

Experimental PIV Radial Splitting Study on Expansive Soil during the Drying Process

Expansive soil is prone to shrinkage and cracking during the drying process, leading to strength and permeability problems that exist widely in water conservancy projects and geotechnical engineering, including foundation pits and cracks at the bottom of channels and slopes. Such problems are closely related to the tensile strength of the soil. In this study, Nanyang expansive soil is taken as the research object and radial splitting tests were performed using a particle image velocimetry (PIV) test system on both undisturbed and remolded expansive soil during the drying process. The results indicated that the load–displacement curve of the undisturbed and remolded expansive soil specimens showed a strain-softening phenomenon and that the peak load increased with decreasing water content. Under the same other conditions, the peak load of the remolded expansive soil specimen was higher than that of the undisturbed soil specimen, with the undisturbed soil specimen having distinctive structural and fractural features. The load–displacement relation curve, displacement vector field, and fracture characteristics had an obvious one-to-one correspondence in the stage division. The compression deformation stage, crack development stage after the peak value, crack maturity stage, and failure stage could be observed via the PIV technique. Moreover, the fracture characteristics of the remolded specimens were more regular than those of the undisturbed specimens. The above research results provide a scientific basis for the design and construction of geotechnical engineering related to expansive soil.

Experimental study on tensile strength of warm frozen soil based on hydraulic fracturing method

Tensile strength is one of the important parameters of frozen soil mechanics, which is widely used in engineering design of frozen soil and theoretical research of frost heave. At present, the research on tensile strength of frozen soil mainly focuses on low-temperature frozen soil, while that of warm frozen soil is less studied, thus limiting scientific evaluation of the tensile strength characteristics of warm frozen soil. In order to enrich the knowledge of tensile strength of warm frozen soil, the tensile strength experiments of silt clay from the Tibetan Plateau are carried out under various temperatures higher than −2 °C using the hydraulic fracturing method (HFM). Our results show that HFM can enable a reliable evaluation of the tensile strength of warm frozen soil, and the relationship between the tensile strength of warm frozen soil and negative temperature can be described by a power function. Compared with the results of uniaxial tension method (UTM) and radial splitting method (RSM), the feasibility of HFM can be regarded as an indirect tensile method in determining the tensile strength of frozen soil, and the suggestion for correcting the test results of indirect tensile method is given. In addition, the mechanism behind the influence of initial water content and temperature on tensile strength of warm frozen soil is analysed. Our results provide a new approach for researchers to analyse the tensile strength of warm frozen soil, thus can benefit the development of frost heave theory, and can reveal the influence of initial water content and temperature on the tensile strength of warm frozen soil.

A time-splitting local meshfree approach for time-fractional anisotropic diffusion equation: application in image denoising

Image denoising approaches based on partial differential modeling have attracted a lot of attention in image processing due to their high performance. The nonlinear anisotropic diffusion equations, specially Perona–Malik model, are powerful tools that improve the quality of the image by removing noise while preserving details and edges. In this paper, we propose a powerful and accurate local meshless algorithm to solve the time-fractional Perona–Malik model which has an adjustable fractional derivative making the control of the diffusion process more convenient than the classical one. In order to overcome the complexities of the problem, a suitable combination of the compactly supported radial basis function method and operator splitting technique is proposed to convert a complex time-fractional partial differential equation into sparse linear algebraic systems that standard solvers can solve. The numerical results of classical and fractional models are explored in different metrics to demonstrate the proposed scheme’s effectiveness. The numerical experiments confirm that the method is suitable to denoise digital images and show that the fractional derivative increases the model’s ability to remove noise in images.

Spin-orbit grating of light in coherent media

We explore the underlying spin-orbit coupling (SOC) mechanism for the interactions between complex structured light fields in a four-level tripod electromagnetically induced transparency (EIT) system. Because one coupling field in the system is a Bessel beam, the susceptibility of the EIT medium can be modulated quasiperiodically in the radial dimension. The paraxial propagation and evolution of a rotating spinor image as the probe field in the medium can be described by a Pauli-like equation with the SOC term. We calculate the spatial distributions of the diffracted patterns of the image in the near field and clearly show the tunable SOC-induced radial splitting of the oppositely polarized pseudospin states. Our scheme may be useful for all-optical processing of spatial multimode signals in coherent media.

Dynamic Mechanical Properties of Several High-Performance Single Fibers.

High-performance fiber-reinforced composites (FRCs) are widely used in bulletproof structures, in which the mechanical properties of the single fibers play a crucial role in ballistic resistance. In this paper, the quasi-static and dynamic mechanical properties of three commonly used fibers, single aramid III, polyimide (PI), and poly-p-phenylenebenzobisoxazole (PBO) fibers are measured by a small-scale tensile testing machine and mini-split Hopkinson tension bar (mini-SHTB), respectively. The results show that the PBO fiber is superior to the other two fibers in terms of strength and elongation. Both the PBO and aramid III fibers exhibit an obvious strain-rate strengthening effect, while the tensile strength of the PI fiber increases initially, then decreases with the increase in strain rate. In addition, the PBO and aramid III fibers show ductile-to-brittle transition with increasing strain rate, and the PI fiber possesses plasticity in the employed strain rate range. Under a high strain rate, a noticeable radial splitting and fibrillation is observed for the PBO fiber, which can explain the strain-rate strengthening effect. Moreover, the large dispersion of the strength at the same strain rate is observed for all the single fibers, and it increases with increasing strain rate, which can be ascribed to the defects in the fibers. Considering the effect of strain rate, only the PBO fiber follows the Weibull distribution, suggesting that the hypothesis of Weibull distribution for single fibers needs to be revisited.

Investigation on the time-dependent characterization of stimulation behaviors for the shale under fracturing fluid invading

In order to understand the time-dependent characteristics of stimulation behaviors during hydraulic fracturing, the self-developed hydraulic fracturing monitoring system under triaxial loading was employed to investigate the cracks' propagation under shale-fluid coupling process. The results reveal that with different duration of fracturing fluid invasion, the pressurization rate of fluid pressure and breakdown pressure (BP) value are obviously varied, and the tensile crack is the dominant crack type, the amounts of shear cracks change accordingly, as well as the failure mode's evolution includes radial split, oblique shear, and combination of oblique shear and radial split. Moreover, the stress regime evolution rules around the cracks are obtained based on the Mohr-Coulomb criterion. This investigation will provide theoretical support for the fracturing's implement in the field, also can be as the laboratory evidence for the interpretation of microseism induced by long-term hydraulic fracturing.

Effect of Chipping Edge Inclination Angle on Size Distribution of Pulp Chips Produced by Chipper-Canter

The effect of oblique cutting on the chipper-canter wood chipping mechanism was studied. A bent knife was modified to obtain inclination angles (IA) of 30° and 50° between the chipping edge and the log feeding direction. The standard knife had an IA of 40°. These three knives were tested on 15 logs each, under frozen (-10°C) and unfrozen conditions. Chip dimensions were assessed by thickness (Domtar distribution) and width/length (Williams distribution). Characteristics and physical properties of the log knots were also measured. Experiments revealed that IA had a significant effect on chip formation mechanism. The IA affected the chipping edge entering the log and the form of the wood slice that was transforming into chips. These changes provoked variations in chip size. An IA of 30° produced wider chips, mostly in the first half of the cut, shaped as an elongated parallelepiped that resulted from a tangential, oblique and radial splitting in a single chip. The shape of chips obtained with IAs of 40° and 50° was more like an upright parallelepiped that was detached mostly by radial and oblique splitting. At the beginning and at the end of the cut, chips were produced by tangential splitting. As a result, for a same chip length of 23 mm, weighted mean chip thickness (WCT) decreased almost 1 mm when IA decreased from 50° to 30°. The knot ratio (total knot area / cant total area) affected both chip size distributions and WCT. Chipping frozen wood at -10°C reduced the chip thickness by 0.55 mm with respect to unfrozen wood. The amount of fines and pin chips also increased nearly two times compared to unfrozen wood. The amount of the Williams accepts chip class increased by 6% when IA decreased from 50° to 30° and by 8% when chipping unfrozen wood compared to frozen wood.

Design of a 5.3-GHz 31.3-dBm Fully Integrated CMOS Power Amplifier Using Folded Splitting and Combining Architecture

A transformer (TF)-based folded radial power splitting and binary power combining architecture is developed for fully integrated CMOS PA design in this paper. The proposed folded splitting and combining architecture has advantages of in-phase RF signal splitting/combining scheme, compact size, uniform dc distribution, and symmetric dc current supply/return path. A 5.3-GHz fully integrated PA using the developed splitting/combining architecture is fabricated on a standard 0.18- $\mu \text{m}$ CMOS technology. The CMOS PA transmits saturation power ( $P_{\mathrm {sat}}$ ) of 31.3 dBm, output 1-dB compression point (OP1 dB) of 26.1 dBm, and power added efficiency (PAE) of 22% at 5.3 GHz. The measured small signal gain is 18.3 dB at 5.3 GHz. The EVM has been measured with IEEE 802.11ac WLAN modulated signals. Using the 20-MHz bandwidth OFDM 64-QAM modulated signal, the PA meets the WLAN EVM specification of 5.6% up to 20.4-dBm linear output power. To our knowledge, the CMOS PA achieves the highest $P_{\mathrm {sat}}$ and OP1 dB with decent PAE among other reported fully integrated CMOS PAs around 5 GHz to date.

Каменные индустрии среднего палеолита из южной галереи Денисовой Пещеры: материалы раскопок 2003 года

Research work resumed in South Chamber of Denisova cave in Altai requires a complete introduction of previously obtained collections into scientific use and the refinement of the techno-typological characteristics in these stone tool industries. This publication presents the results of a technical and typological analysis of stone industries from layers 22-19 and 14 in the mouth area of the southern chamber. The initial stages of the settlement of the cave characterize materials from the upper part of layer 22 and from layer 21, which were formed during the periods of MIS 8 and MIS 7, respectively. These industries are characterized mainly by radial splitting, various types of toothed, notched, spinous tools and scrapers, an abundance of chips with ventral upholstery of the longitudinal edges and with a remote residual impact platform. Further development of the Middle Paleolithic is reflected in the materials materials from layers 20, 19 and 14, which were most likely formed at the end of MIS 6 and in the first half of MIS 5 after a break in sedimentation. In the industries of this time, planar parallel and radial cores were distributed. A small series presents Levallois cores for flakes and plates. In the tool set against the background of the predominance of different types of the scraper, a well-pronounced gear-notched component is preserved. There are products of the Upper Paleolithic group.

Clinical Faceoff: The Role of Arthroscopic Partial Meniscectomy in the Treatment of Meniscal Tears.

Clinical Faceoff: The Role of Arthroscopic Partial Meniscectomy in the Treatment of Meniscal Tears.

Postnatal dilatation of umbilical cord vessels and its impact on wall integrity: Prerequisite for the artificial placenta.

A lung assist device, which acts as an artificial placenta, can provide additional gas exchange for preterm and term newborns with respiratory failure. The concept of the lung assist device requires a large bore access via umbilical vessels to allow pumpless extracorporeal blood flow rates up to 30 mL/kg/min. After birth, constricted umbilical vessels need to be reopened for vascular access. The objective is to study the impact of umbilical vessel expansion on vessel integrity for achieving large bore access. Umbilical cords from healthy term deliveries were cannulated and dilatated with percutaneous transluminal angioplasty catheters in 1 mm increments from 4 to 8 mm for umbilical artery and from 4 to 15 mm for umbilical vein, n = 6 per expansion diameter. Paraffin-embedded transverse sections of dilated and control samples were HE & Van Gieson stained. Effects of dilatation, shown by splitting, were measured. Umbilical vessel expansion led to concentric splitting, shown by areas devoid of extracellular matrix and nuclei in the tunica intima and media. No radial splitting was observed. Results suggest an expansion threshold of umbilical artery at 6 mm and umbilical vein at 7 mm, while maximal splitting was observed above this threshold (3.6 ± 0.8%, p = 0.043 for umbilical artery 7 mm and 6.3 ± 1.8%, p = 0.048 for umbilical vein 8 mm). Endothelial cell sloughing was present in all dilated samples but not in the control samples. The suggested thresholds for safe expansions are similar to in utero umbilical vessel diameters and demonstrate a proof of concept for attaining large bore access for the lung assist device.

Biophysical features of cereal endosperm that decrease starch digestibility

The influence of the physical structure of cereal endosperm on the natural structural integrity (intact cells) and starch bioaccessibility of the resultant flours was studied using maize as example. Endosperm hardness, defined by its intracellular (protein matrix) and extracellular (cell walls) constituents, affected the granular and molecular damage of the starch of the resultant flours leading to higher digestibility of raw hard than soft endosperm flours, but comparatively lower digestibility after cooking. After milling, hard endosperm possessed more damaged starch (radial splitting of amylopectin clusters) in the periphery of the resultant particles that increased in vitro starch digestibility of raw flours. Conversely, the hard endosperm plant tissue matrix significantly limited water availability and heat transfer on starch gelatinisation, thereby decreasing the digestion rate after hydrothermal processing (in particle size flours >80μm). This study provides a unique mechanistic understanding to obtain cereal flours with slow digestion property for commercial utilisation.

Synthetic seismic anisotropy models within a slab impinging on the core–mantle boundary

The lowermost few hundreds of kilometres of the Earth's mantle are elastically anisotropic; seismic velocities vary with direction of propagation and polarization. Observations of strong seismic anisotropy correlate with regions where subducted slab material is expected. In this study, we evaluate the hypothesis that crystal preferred orientation (CPO) in a slab, as it impinges on the core–mantle boundary, is the cause of the observed anisotropy. Next, we determine if fast polarization directions seen by shear waves can be mapped to directions of geodynamic flow. This approach is similar to our previous study performed for a 2-D geodynamic model. In this study, we employ a 3-D geodynamic model with temperature-dependent viscosity and kinematic velocity boundary conditions defined at the surface of the Earth to create a broad downwelling slab. Tracers track the deformation that we assume to be accommodated by dislocation creep. We evaluate the models for the presence of perovskite or post-perovskite and for different main slip systems along which dislocation creep may occur in post-perovskite [(100),(010) and (001)]—resulting in four different mineralogical models of CPO. Combining the crystal pole orientations with single crystal elastic constants results in seismically distinguishable models of seismic anisotropy. The models are evaluated against published seismic observations by analysing different anisotropic components: the radial anisotropy, the splitting for (sub-)vertical phases (i.e. azimuthal anisotropy), and the splitting for subhorizontal phases. The patterns in radial anisotropy confirm our earlier results in 2-D. Observations of radial anisotropy and splitting in subhorizontal phases are mostly consistent with our models of post-perovskite with (010)-slip and (001)-slip. Our model of (001)-slip predicts stronger splitting than for (010)-slip for horizontally propagating phases in all directions. The strongest seismic anisotropy in this model occurs where the slab impinges on the core–mantle boundary. The azimuthal anisotropy pattern for (001)-slip shows fast axis directions at the edges of the slab (sub-)parallel to flow directions, suggesting horizontal flows may be mapped out in the lowermost mantle using seismic observations.

Separation of spin angular momentum in space-variant linearly polarized beam

We show that the spin angular momentum (SAM) flux in a space-variant linearly polarized beam can be separated in the focal plane. Such a beam carries only orbital angular momentum (OAM) and develops a net SAM flux upon focusing. The radial splitting of the SAM flux density is mediated by the phase vortex (or OAM) and can be controlled by the topological charge of the phase vortex. Optical trapping experiments verify the separation of the SAM flux density. The proposed approach enriches the manipulation of the angular momentum of light fields and inspires more designs of focus engineering, which would benefit optical micromanipulation of microscopic particles.

A simple and safe technique for performing single-port laparoscopic resection of appendiceal mucocele

We report a new method of performing single-port laparoscopic surgery for appendiceal mucocele. The key points of our technique are placing a 3/4 circumferential skin incision with multiple radial splits on the confine of the umbilicus, use of a "home-made" multichannel port system, and trimming the skin incision straight through the confine of the umbilicus at the time of wound closure. A 65-year-old woman with appendiceal mucocele, 80 mm in diameter, successfully underwent ileocecal resection by this procedure. She remains in good health without any wound complications 8 months postoperatively.

Changes in Tibiofemoral Contact Mechanics Following Radial Split and Vertical Tears of the Medial Meniscus

The biomechanical effects of radial split tears and vertical tears of the medial meniscus are not well characterized. The goal of the present study was to determine the effects of these meniscal tears and meniscal repair on tibiofemoral joint contact pressure and area. Eleven fresh-frozen cadaveric knees were loaded to 1000 N of axial load at 0, 30, 60, and 90 of flexion with use of a custom testing apparatus attached to a materials testing machine. Tibiofemoral translations and internal-external and varus-valgus rotations were unconstrained. The knees were tested under four conditions: intact, medial meniscal tear, repaired meniscal tear, and total medial meniscectomy. Radial split tears were created in six knees, and vertical tears were created in five knees. Pressure-sensitive film was used to measure tibiofemoral contact pressure and area. Radial split tears of the medial meniscus did not cause significant changes in tibiofemoral joint contact pressure and area. Vertical tears of the medial meniscus caused increases in tibiofemoral joint contact pressure and reductions in contact area in the medial and lateral compartments that were not significantly different from those associated with total medial meniscectomy. The exception was at 90, where the lateral compartment pressure associated with the vertical tear of the medial meniscus was higher than that associated with total medial meniscectomy. In general, after repair of the vertical tear, contact pressure and area values were similar to those in the intact condition. Radial split tears of the medial meniscus that extend from the inner rim to the peripheral third of the meniscus do not cause significant changes in joint contact area and pressure. Vertical tears of the medial meniscus cause nonsignificant increases in joint contact pressure and reductions in contact area in the medial and lateral compartments.Repair of the vertical tear reverses these contact changes, resulting in contact pressure and area similar to the intact state.

Single-incision laparoscopic-assisted surgery for colon cancer via a periumbilical approach using a surgical glove: Initial experience with 9 cases

Our initial experience of performing a single-incision laparoscopic-assisted (SILS) colectomy using a “home-made” multichannel port system is presented. Nine patients (5 women) with a median age of 67 years (range, 55–72 years) and a median body mass index of 21.2 kg/m 2 (range, 17.8–26.7 kg/m 2) underwent the SILS colectomy for colon cancer between September 2009 and March 2010. The sites of the primary tumor were the ascending colon ( n = 2), hepatic flexure ( n = 1), transverse colon ( n = 2), and sigmoid colon ( n = 4). Each trocar was introduced intraperitoneally through each finger of a surgical glove attached to the wound protector, which was applied to a midline fasciotomy made via a ¾-circular periumbilical incision. If necessary, one to three radial splits were added to the incision. The colon was mobilized intracorporeally, and the vessels were ligated intra- or extracorporeally. All the patients underwent a curative segmental colectomy without conversion to a standard multiport laparoscopy or open surgery. The median operative time and blood loss were 140 min (range, 135–165 min) and 50 mL (range, 20–225 mL), respectively. The median number of harvested lymph nodes was 18 (range, 6–31). The pathological stages included stage 0 ( n = 2), stage I ( n = 6), and stage III ( n = 1). The median number of postoperative analgesic use was one (range, 0–6). No intra- or postoperative complications occurred in this series. Our SILS colectomy procedure seems feasible and safe in selected patients with colon cancer.

An element enriched formulation for simulation of splitting failure

Abstract Radial cracking propagation is often related to the bond transfer mechanism induced by slippage of a deformed bar. However, this failure pattern can also develop in other situations, namely: ( i ) concrete pipes submitted to an excessive inner pressure or ( ii ) concrete structures exposed to adverse environmental conditions under which corrosion or frost develops. In this paper a new contribution for the simulation of radial splitting failure is given. A discrete strong discontinuity formulation is presented which is fully capable of embedding radial discontinuities into axisymmetric finite elements. Numerical examples are used to show: ( i ) the capability of fully softening the applied inner pressure and ( ii ) mesh independence. Comparison with two published analytical approaches is performed for varying brittleness numbers. Finally, the model is applied to the simulation of both plain and reinforced concrete cylinders subjected to increasing inner pressure. A good agreement with experimental data is obtained.

Cartilage Collagen Matrix Reorientation and Displacement in Response to Surface Loading

An investigation of collagen fiber reorientation, as well as fluid and matrix movement of equine articular cartilage and subchondral bone under compressive mechanical loads, was undertaken using small angle X-ray scattering measurements and optical microscopy. Small angle X-ray scattering measurements were made on healthy and diseased samples of equine articular cartilage and subchondral bone mounted in a mechanical testing apparatus on station ID18F of ESRF, Grenoble, together with fiber orientation analysis using polarized light and displacement measurements of the cartilage matrix and fluid using tracers. At surface pressures of up to approximately 1.5 MPa, there was reversible compression of the tangential surface fibers and immediately subjacent zone. As load increased, deformation in these zones reached a maximum and then reorientation propagated to the radial deep zone. Between surface pressures of 4.8 MPa and 6.0 MPa, fiber orientation above the tide mark rotated 10 deg from the radial direction, with an overall loss of alignment. With further increase in load, the fibers "crimped" as shown by the appearance of subsidiary peaks approximately +/-10 deg either side of the principal fiber orientation direction. Failure at higher loads was characterized by a radial split in the deep cartilage, which propagated along the tide mark while the surface zone remained intact. In lesions, the fiber organization was disrupted and the initial response to load was consistent with early rupture of fibers, but the matrix relaxed to an organization very similar to that of the unloaded tissue. Tracer measurements revealed anisotropic solid and fluid displacement, which depended strongly on depth within the tissue.