Wedge Angle Research Articles

Automation of radiation treatment planning for rectal cancer.

PurposeTo develop an automated workflow for rectal cancer three‐dimensional conformal radiotherapy (3DCRT) treatment planning that combines deep learning (DL) aperture predictions and forward‐planning algorithms.MethodsWe designed an algorithm to automate the clinical workflow for 3DCRT planning with field aperture creations and field‐in‐field (FIF) planning. DL models (DeepLabV3+ architecture) were trained, validated, and tested on 555 patients to automatically generate aperture shapes for primary (posterior–anterior [PA] and opposed laterals) and boost fields. Network inputs were digitally reconstructed radiographs, gross tumor volume (GTV), and nodal GTV. A physician scored each aperture for 20 patients on a 5‐point scale (>3 is acceptable). A planning algorithm was then developed to create a homogeneous dose using a combination of wedges and subfields. The algorithm iteratively identifies a hotspot volume, creates a subfield, calculates dose, and optimizes beam weight all without user intervention. The algorithm was tested on 20 patients using clinical apertures with varying wedge angles and definitions of hotspots, and the resulting plans were scored by a physician. The end‐to‐end workflow was tested and scored by a physician on another 39 patients.ResultsThe predicted apertures had Dice scores of 0.95, 0.94, and 0.90 for PA, laterals, and boost fields, respectively. Overall, 100%, 95%, and 87.5% of the PA, laterals, and boost apertures were scored as clinically acceptable, respectively. At least one auto‐plan was clinically acceptable for all patients. Wedged and non‐wedged plans were clinically acceptable for 85% and 50% of patients, respectively. The hotspot dose percentage was reduced from 121% (σ = 14%) to 109% (σ = 5%) of prescription dose for all plans. The integrated end‐to‐end workflow of automatically generated apertures and optimized FIF planning gave clinically acceptable plans for 38/39 (97%) of patients.ConclusionWe have successfully automated the clinical workflow for generating radiotherapy plans for rectal cancer for our institution.

Heat transfer enhancement and entropy generation minimization using CNTs suspended nanofluid upon a convectively warmed moving wedge: An optimal case study

AbstractThis paper aims to examine the effects of singleand multi‐walled carbon nanotubes (CNTs) nanoparticles on heat transfer enhancement and inherent irreversibility in the boundary layer of water base nanoliquid flow over a convectively heated moving wedge with thermal radiation. Manipulation of the angle positioning towards the flow stream provides the opportunity for comparing physical aspects in the flow states, where three main geometries of the well‐known Falkner–Skan problem include: (i) the flat plat (named Blasius flow), (ii) the wedge, and (iii) the vertical plate (named Hiemenz stagnation flow) have been considered to present a comprehensive development of this significant problem. Applying suitable similarity constraints, the model partial differential equations are transformed into a set of nonlinear ordinary differential equations. Solutions are obtained analytically via optimal homotopy asymptotic method and numerically via shooting technique coupled with the Runge–Kutta–Fehlberg fourth–fifth scheme. The impacts of solid volume fraction of carbon nanoparticles along with other germane factors, such as wedge angle, velocity ratio parameter, Biot number, thermal radiation, and so forth on velocity and thermal profiles, Nusselt number, heat transfer enhancement, rate of entropy generation, and irreversibility ratio, are scrutinized via graphical simulations and discussed. Optimization of such entropy developments in the system was found to depend on geometrical (β), dynamical (λ), and thermophysical (Bi, NR, Ec, φ) parameters. The ultimate objective of reducing the energy loss and enhancing heat transference was obtained with the geometrical manipulation of a flat plate case (β = 0). Dynamically (λ = 1) were spotted to exert the best fluidity irrespective of obstacle shapes (wedge or plate) in its way. In thermophysical aspects, reducing the convective heating develops a favorable situation for attaining the optimal balance between energy loss and heat transfer. SWCNT/water could be the better choice with enhanced thermal transference ability and exerts minimal irreversibility to overshadow the influences of all the above‐mentioned factors. The SWCNT suspended nanofluid can provide 12%–64% heat transfer enhancement when compared with the multiwalled CNT nanofluid which ranges from over 11% to 58% heat transference rate.

Performance of Microchannel Heat Sink Made of Silicon Material with the Two-Sided Wedge

New designs of the microchannel with a two-sided wedge shape at the base were studied numerically. Five different wedge angles ranging from 3° to 15° were incorporated into the microchannel design. Simulation of this novel microchannel was carried out using Computational Fluid Dynamics (CFD). Three-dimensional models of the microchannel heat sink were created, discretized, and based on Navier–Stokes and energy equations; laminar numerical solutions were obtained for heat transfer and pressure drop. Flow characteristics of water as coolant in a microchannel were studied. It was observed that numerical results are in good agreement with experimental results. It was found that the Nusselt number and friction factor are significantly varied with the increase in Reynolds number. The Nusselt number varies in the following ranges of 5.963–8.521, 5.986–8.550, 6.009–8.568, 6.040–8.609, and 6.078–8.644 at 3°, 6°, 9°, 12°, and 15°, respectively. The microchannel with a wedge angle of 15° was found to be better in terms of Nusselt number and thermo-hydraulic performance. The enhancement in the Nusselt number is found as 1.017–1.036 for a wedge angle of 15°; however, friction factors do not show the perceptible values at distinct values of wedge angle. Moreover, the thermo-hydraulic performance parameters (THPP) were evaluated and found to be maximum in the range of 1.027–1.045 for a wedge angle of 15°. However, minimum THPP was found in the range of 1.005–1.0185 for a wedge angle of 3°.

Impact of Wedge Parameters on Ultrasonic Lamb Wave Liquid-Level Sensor.

The ultrasonic Lamb wave detection principle can realize the noncontact measurement of liquid level in closed containers. When designing an ultrasonic Lamb wave sensor, it is vital to thoroughly study and select the optimal wedge size at the front of the sensor. In this paper, firstly, we select the best working mode of Lamb waves according to their propagation dispersion curve in aluminum alloy, and we obtain the best angle of wedge through experiments. Secondly, we study the impact of the size of the wedge block on the results, and we obtain the selection method of wedge block parameters. The evaluations show that, when the frequency–thickness product is 3 MHz·mm, the Lamb waves work in the A1 mode, and the experimental effect is the best. At this time, the incident angle of the ultrasonic wave is 27.39°. The wedge thickness should be designed to avoid the near-field area of the ultrasonic field, and we should choose the length as odd multiples of 1/4 wavelength. The rules obtained from the experiment can effectively select the best working mode for ultrasonic Lamb waves, while also providing a basis for the design of the wedge block size in a Lamb wave sensor.

Ship’s Wake on a Finite Water Depth in the Presence of a Shear Flow

The ship’s wake in the presence of a shear flow of constant vorticity at a finite water depth is investigated by expanding the Whitham-Lighthill kinematic theory. It has been established that the structure of a wave ship wake radically depends on Froude number Fr (in terms of water depth) and especially on the critical Froude number Frcr, which depends on the magnitude and direction of the shear flow. At its subcritical values Fr<Frcr two types of waves are presented: long transverse and short divergent waves inside the wedge area with an angle depending on Fr For the supercritical range Fr>Frcr only divergent waves are presented inside the wake region. Critical Froude number Frcr is variable and mostly depends on collinear with the ship path component of the shear flow: it decreases with the unidirectional shear flow and increases on the counter shear current. The wedge angle of the ship wake expands with an increase in the unidirectional shear flow and narrows in the oncoming flow in the subcritical mode of the ship’s motion Fr<Frcr. Wake angle decreased with Froude number for Fr>Frcr and only divergent waves with the crests almost collinear with ship path are finally presented in the narrow ship wake. For a critical value of the Froude number Fr=Frcr, the ship’s wake has a total wedge angle of 180° with waves directed parallel to the ship’s motion. The presence of a shear flow crossing the path of the ship gives a strong asymmetry to the wake. An increase in the perpendicular shear flow leads to an increase in the difference between the angles of the wake arms.

High-frequency permeability of porous media with thin constrictions. I. Wedge-shaped porous media

In this series of publications, the high-frequency behavior of the dynamic permeability of porous media with thin constriction is investigated. In Part I, the classical theory of Johnson et al. [“Theory of dynamic permeability and tortuosity in fluid saturated porous media,” J. Fluid Mech. 176, 379 (1987)] for soft-curved pore geometries is recalled. For wedge-shaped pore geometries, numerical computations (by finite element method) and analysis by Cortis et al. [“Influence of pore roughness on high-frequency permeability,” Phys. Fluids 15, 1766 (2003)] are revisited and confirmed, while leading to important new conclusions. Because the electric field is singular at the tip of wedges, the original model developed by Johnson et al., which links the viscous fluid flow problem to the electrical conduction problem, is inappropriate for describing the high-frequency behavior of the viscous fluid flow through wedge-shaped porous media. In particular, in the case of small wedge angles, we show that the real part of the dynamic permeability behaves in the high-frequency regime as ℜ(k(ω))∝ω−(3/2)(ln (ω)+constant), which differs from the predictions of the Johnson et al. model [ℜ(k(ω))∝ω−(3/2)]. However, our results show that the classical Johnson et al. high frequency limit can be a good approximation of the viscous fluid flow if the electrical conduction problem is solved over a fluid domain truncated by a boundary layer having a thickness comparable to the viscous skin depth. In Part II, we consider foam with perforated membranes involving different microstructural characteristic lengths: pore size, membrane aperture size, and membrane thickness. We assess the validity domain of the Johnson et al. approximation and test our modified high-frequency approximation for such porous materials.

High-frequency permeability of porous media with thin constrictions. II. Porous media containing thin holed membranes

In this series of publications, the high-frequency behavior of the dynamic permeability of porous media with thin constriction is investigated. In Paper I, the classical theory of Johnson et al. [J. Fluid Mech. 176, 379 (1987)] for soft-curved pore geometries is recalled. For wedge-shaped pore geometries, numerical computations (by the finite element method) and analysis by Cortis et al. [Phy. Fluids 15, 1766 (2003)] are revisited and confirmed, while leading to important new conclusions. Because the electric field is singular at the tip of wedges, the original model developed by Johnson et al., which links the viscous fluid flow problem to the electrical conduction problem, is inappropriate for describing the high-frequency behavior of the viscous fluid flow through wedge-shaped porous media. In particular, in the case of small wedge angles, we show that the real part of the dynamic permeability behaves in the high-frequency regime as ℜ(k(ω))∝ω−(3/2)(ln (ω)+constant), which differs from the predictions of the Johnson et al. model [ℜ(k(ω))∝ω−(3/2)]. However, our results show that the classical Johnson et al. high frequency limit can be a good approximation of the viscous fluid flow if the electrical conduction problem is solved over a fluid domain truncated by a boundary layer having a thickness comparable to the viscous skin depth. In Paper II, we consider foam with perforated membranes involving different microstructural characteristic lengths: pore size, membrane aperture size, and membrane thickness. We assess the validity domain of the Johnson et al. approximation and test our modified high-frequency approximation for such porous materials.

Flexible and wide-range tuning of liquid crystal polarization grating period based on single and interference-free exposure.

We propose a period control method of liquid crystal polarization grating (LCPG) based on an nterference-free and single exposure process. By adjusting three parameters of exposure setup, including incident angle of exposure beam, wedge angle of birefringent prism and tilt angle of the sample, polarization distribution of the exposure beam is changed. The spatially variant polarization of the exposure beam is transferred to liquid crystal (LC) molecules by an azo-dye photo-sensitive layer. Consequently, the LCPG with the target period is obtained. The proposed method has high flexibility and a wide range of period adjustment covering several microns to more than thousands of microns according to calculated results. Experimental results fit well with calculations. The LCPGs with different values of period from 4.5µm to more than 200µm have been realized experimentally. The proposed interference-free method would accelerate the application of LCPGs with a robust and simple fabrication process.

Percutaneous cortical bone trajectory screw fixation versus traditional open pedicle screw fixation for type A thoracolumbar fractures without neurological deficit.

Retrospective matched-cohort comparative study. Cortical bone trajectory screw (CBT) technique is a new insertion technique in terms of fixation strength and less invasiveness. The purposes of this study were to compare the clinical and radiological outcomes of percutaneous CBT fixation (PCBT) with traditional open posterior pedicle screw fixation (OPPS) technique. Between September 2019 and October 2020, patients undergoing posterior stabilization were matched for age, sex, diagnosis, fractured level, and AO classification. 24 control patients with OPPS were identified and appropriately matched to 24 consecutive patients with PCBT technique. Clinical outcomes and radiographic assessments including vertebral wedge angle (VWA) and sagittal index were recorded and compared between the two groups. Incision length, intraoperative blood loss and hospital stay in the PCBT group were significantly better than the OPPS group (P < 0.05). The VAS scores 5days after operation for PCBT patients were significantly lower than those for OPPS patients (P = 0.003), but these differences lost significance at last follow-up. There was no significant difference in VWA and sagittal index between OPPS and PCBT group (P > 0.05). While no complications were noted in the PCBT group, there were four cases with complications in the traditional OPPS group. The present study showed that PCBT is a safe and feasible method for the treatment of thoracolumbar fractures without neurological deficits. This new surgical treatment was more minimally invasive, yet yielded equivalent or superior clinical and radiographic outcomes compared to the traditional open pedicle screw fixation surgery.

Influence of Slip Parameter, Viscous Dissipation and Joule Heating Effect on Boundary Layer Flow and Heat Transfer Over a Power-Law Stretching Wedge-Shaped Surface with the Correlation Coefficient and Multiple Regressions

The influence of slip parameter, viscous dissipation, and Joule heating parameter on MHD boundary layer nanofluid flow over a permeable wedge-shaped surface was analysed. The PDEs and the associated boundary conditions were transformed to a set of non-similar ODEs and the obtained system of equations was solved numerically with the help of the spectral quasi-linearization method (SQLM) by applying suitable software. This method helps to identify the accuracy and convergence of the present problem. The current numerical results were compared with previously published work and are found to be similar. The fluid velocity, fluid temperature, and nanoparticle concentration within the boundary layer region for various values of the parameters such as the slip effect, magnetic strength, Prandtl number, Lewis number, stretching ratio, viscous dissipation, suction, Brownian motion, Joule heating, heat generation, and thermophoresis are studied. It is observed that the Brownian motion, Joule heating, viscous dissipation, and thermophoresis lead to decreases in the heat and mass transfer rate. The skin friction coefficient enhances with slip, magnetic, permeability, and suction parameters, but reduces with the Brownian motion, wedge angle, and stretching ratio parameters whereas there is no effect of mixed convection, thermophoresis, heat generation parameters, the Prandtl and Eckert number.

Numerical investigation on movement of triple points on oblique detonation surfaces

A normal detonation wave in a gaseous mixture is a transient, multidimensional structure containing triple points (TPs) that collide in pairs and then propagate oppositely. However, the TPs on an oblique detonation wave (ODW) almost propagate along the same direction in most studies. In this study, the reactive Euler equations coupled with a two-step induction–reaction kinetic model are used to solve a two-dimensional wedge-induced ODW. Two novel movement patterns are observed in most cases. Results show that the TPs of the ODW can propagate upstream and even stand on the wave surface. The movement patterns of TPs include downstream, upstream, and steady according to their propagation direction relative to the wedge. We find that the ratio of the post-ODW flow speed Uτ to the transverse wave speed UT dominates the TP movement types. When the speed ratio Uτ/UT is approximately equal to 1, the TPs can stand on the wave surface. Above unity, downstream TPs form, and upstream TPs correspond to a value smaller than 1. Furthermore, the inflow Mach number has little influence on UT, while Uτ changes significantly. This is largely due to the high sensitivity of the ODW angle to the inflow. The high heat release rate benefits upstream TPs, and steady TPs form under a large wedge angle. The results are confirmed by varying the inflow Mach number, wedge angle, and chemical parameters.

Efficacy of percutaneous short segment fixation in the treatment of Magerl A3 thoracolumbar fractures with low bone mineral density:a retrospective study

To explore the clinical efficacy of percutaneous pedicle screw short segment internal fixation with or without the intermediate screw in the treatment of Magerl A3 thoracolumbar fractures with low bone mineral density. Patients with Magerl A3 thoracolumbar fracture underwent percutaneous pedicle screw short segment internal fixation from January 2017 to July 2020 were retrospectively analyzed, 93 cases met the diagnosis and inclusion criteria, 9 cases were excluded according to the exclusion criteria, and the remaining 84 cases obtained complete imaging follow-up data. There were 38 males and 46 females, the age ranged from 56 to 73 years old with an average of (64.78±7.12) years old, bone mineral density (BMD) ranged from 0.61 to 0.89 g/cm3 with an average of (0.73±0.14) g/cm3, the follow-up time was 11 to 25 months with an average of (17.58±6.12) months. There were 45 cases in group A with intermediate screw and 39 cases in group B without intermediate screw. The operation time and intraoperative blood loss were recorded, Oswestry Disability Index (ODI) and visual analogue scale (VAS) were used for clinical evaluation. The Cobb angle, vertebral wedge angle (VWA) and anterior vertebral body height (AVBH) were measured by X-ray after the operation. The corrected loss of the above parameters was calculated. There were 5 cases of screw loosening in 84 patients (2 cases in group A and 3 cases in group B, P>0.05). There were significant differences in operation time and intraoperative blood loss between two groups(P<0.01). Clinical effects of two groups were good, postoperative VAS and ODI after operation obviously improved, there was no significant difference between two groups during all follow-up periods (3 days, 1 month after operation and the final follow-up) (P>0.05). Three days after the operation, the image evaluations (Cobb angle, VWA and AVBH) were significantly improved (P<0.05), but significant reduction loss was observed in both groups at 1 month after the operation and at the final follow-up (P<0.05). At the final follow-up, the loss of Cobb angle, VWA and AVBH in group A were (5.26±4.18) °, (4.63±3.80) ° and (9.54±8.71)%, respectively;group B was (6.01±4.34) °, (6.55±6.21) ° and (11.67± 9.95)%, respectively;however, there was no significant difference in reduction loss between the two groups(P>0.05). Although the curative effect of the patients is satisfactory, the stability of the patients can not be improved by increasing the middle injured vertebra screw placement, the two groups of percutaneous short segment internal fixation can not resist the reduction loss of Magerl-A3 thoracolumbar fracture with low bone mineral density. Because the injured vertebra screw increases the operation time and intraoperative blood loss, it is not significant to use the intermediate screw for the elderly Magerl A3 thoracolumbar fractures with low bone mineral density.

Stability Analysis of Unsteady Hybrid Nanofluid Flow over the Falkner-Skan Wedge.

Numerous manufacturing processes, including the drawing of plastic films, have a major impact on mass transport. These functionalities necessitate the solution of the Falkner–Skan equation and some of its configurations when applied to various geometries and boundary conditions. Hence, the current paper discusses the impact of unsteady hybrid nanofluid flow on a moving Falkner–Skan wedge with a convective boundary condition. This problem is modeled by partial differential equations, which are then converted into ordinary (similar) differential equations using appropriate similarity transformations. The bvp4c technique in MATLAB solves these ordinary differential equations numerically. Since more than one solution is possible in this paper, stability analysis is conducted. Thus, it is found that only one stable solution is identified as reliable (physically realizable in practice). The skin friction coefficient and heat transfer rate, along with the velocity and temperature profile distributions, are examined to determine the values of several parameters. The findings reveal that dual-type nanoparticles and wedge angle parameters improve thermal efficiency. A lower value of the unsteadiness parameter reduces the efficiency of hybrid nanofluids in terms of heat transfer and skin friction coefficient, whereas increasing the Biot number of the working fluid does not affect the critical point in the current analysis.

The effects of biomechanical factors on adjacent vertebral compression fractures after percutaneous kyphoplasty: a propensity score matching analysis.

As a routine treatment of OVCF, the postoperative refracture of PKP is a serious problem. The aim of our study was to explore the impact of lumbar biomechanical changes on the risk of AVCF. A propensity score matching was performed to balance the interference of osteoporosis, which is the primary risk factor of AVCF. A retrospective, single-center case-control study was performed. From September 2013 to March 2020, 1752 patients were enrolled, and AVCF was assessed in 80 of these patients. A propensity score matching (PSM) analysis was performed, and 5 potential confounding factors were matched (age, BMI, number of fractured vertebral bodies, fracture region, and HDL). The preoperative and postoperative radiological factors were measured in the matched cohort of 48 pairs. A conditional logistic regression analysis to adjust the comparative risks. The preoperative wedge angle and its postoperative recovery of the AVCF group were significantly higher than that of the non-AVCF group. The local kyphosis of the fractured vertebral body between the two groups was similar, but the recovery in the AVCF group was slightly higher than that in the non-AVCF group. The preoperative and postoperative relative anterior height (RAH) of the fractured vertebral body was familiar in two groups, so was the recovery of RAH. The preoperative spino-sacral angle (SSA) was significantly higher in the AVCF group than in the non-AVCF group. The preoperative wedge angle was identified as the only significant risk factor for AVCF in the multivariate analysis. In conclusion, a larger preoperative fracture vertebral wedge angle is a risk factor for AVCF. For such high-risk patients, surgeons should be cautious about surgical decisions. The postoperative active measures and tailored surveillance should be attached to great importance as well.

Entropy generation on magnetohydrodynamic laminar boundary‐layer Casson CNT‐based nanofluid flow across a wedge by using the homotopy analysis method

AbstractThe purpose of the study is to scrutinize the entropy generation analysis on magnetohydrodynamic heat transfer flow from Casson single‐walled carbon nanotube on a wedge with Joule heating and viscous dissipation. Kerosene oil is considered as base fluid because of its exclusive features, advanced thermal conductivity, application, and unique behavior. Using similarity variables, the regulating equations are modified into nonlinear coupled, ordinary differential equations, which are then tackled using homotopy analysis method. Impacts of emerging parameters on entropy generation, temperature, velocity, and Bejan number distributions are discussed and shown graphically. The Nusselt number and skin‐friction coefficient values are shown in a table. The results reveal that velocity enhances due to increasing magnetic and Casson parameters. It was inspected that entropy production enhances due to increasing wedge angle and magnetic parameter and decays with Casson parameter. Also, it is examined that the Bejan number upsurges due to larger Casson and wedge angle parameters but a reverse trend can be observed with increasing values of a magnetic parameter. The present results have been endorsed by comparing with the available data in the literature, it was discovered that they are in excellent agreement.

Structural Design and Dynamic Simulation Optimization of the Triggering Device in a Pressure-Holding Controller for Deep in Situ Coring

As Earth’s shallow coal resources are gradually depleted, humans turn their mining operations to deeper regions. However, because the mechanics of deep-rock masses have not been fully established, the development of deep resources lacks theoretical guidance, and the continuity of such engineering activities is poor. The basis of deep-rock mechanics theory is to achieve deep in situ rock fidelity coring (including the maintenance of pore pressure and temperature). To achieve this goal, deep in situ pressure-holding coring technology is needed. The pressure-holding controller is the key corer component for realizing deep in situ pressure-holding and coring technology. The flap-valve-type pressure-holding controller driven by an elastic force or gravity alone is not enough to provide the initial sealing pressure for the sealing surface. Therefore, a trigger mechanism that assists the pressure-holding controller in achieving closing and initial sealing was designed. Then, the action and friction characteristics of the triggering mechanism were calculated according to the experimental dynamics simulation calculations of different closing characteristics that are affected by gravity in pressure-holding controller space. Optimization was conducted to determine the optimal values of the trigger mechanism spring stiffness, wedge angle, and other parameters. The mechanism can provide technical support for deep pressure-holding coring and improve the pressure-holding power of deep in situ rock coring.

The progression of the vertebral body bruise associated with a spinal fracture

BackgroundAdvances in magnetic resonance imaging (MRI) have made it possible to find the vertebral body bruise (VBB), which was not found in computed tomography (CT) after trauma. There has been only one study with adult patients about whether traumatic VBB will cause a collapse of the vertebral body or not. The purpose is to elucidate the progression of VBB in non-osteoporotic adult patients and to identify the possible factors influencing the progression.MethodThe VBB was defined on MRI as band-like or diffuse zones of high signal intensity on T2-weighted sequences without fracture of the cortex based on CT. The study population with traumatic VBB associated with non-osteoporotic spinal fracture was composed of 15 females and 21 males. The minimal follow-up period was 6 months. The ratio of anterior to posterior heights of the VBB, the ratio of anterior heights of the VBB to the average of those of cranial and caudal adjacent vertebral bodies, the anterior wedge angle of the VBB, and the focal angle around the VBB were compared between the initial and final visits. We evaluated the age of the patients, the C2 plumb line distance, the regional location of VBB, the etiology of VBB, and the treatment methods of the fractures as possible risk factors influencing the progression.ResultsThere was no difference in the ratios and angles between the initial and final visits. The differences in the ratios and angles between the initial and final visits were not dependent on the possible risk factors. The anterior superior area is the most common in the distribution of VBB.ConclusionsUnlike compression fractures, the vertebral body with traumatic VBB found in adult patients with non-osteoporotic spinal fractures of AO classification A or B types did not develop collapse. In clinical practice, it is reasonable to diagnose it as a spinal fracture rather than a VBB if the collapse of a possible VBB occurs.

Stability of flow in a channel with repeated flow-facing wedge-shaped protrusions

Motivated by an interest in inciting instabilities and mixing for heat transfer enhancement in ducts, flow in a channel with repeated wedge-shaped protrusions is considered for various blockage ratios (wedge height to duct height), pitch (distance between wedges) and wedge angles. The stability of the two-dimensional base flow and its dependence on the geometric parameters is elucidated through a global linear stability analysis. A linearly unstable two-dimensional mode was found, contrasting similar confined flow set-ups. However, the primary instability is a three-dimensional mode manifesting as counter-rotating streamwise vortices over the wedge tip. Analysis of the kinetic energy budget indicates a lift-up mechanism leading to instability, with the dominant energy gain of the global three-dimensional mode due to shear in the base flow. Structural sensitivity and receptivity of the instability to momentum forcing identifies the core of the instability and locations important for flow control. An endogeneity approach is used to show that the local perturbation pressure gradient component dominates the distribution of the local contribution to the growth rate of the linear global eigenmode in most cases considered, despite its net contribution being identically zero. Weakly nonlinear Stuart–Landau analysis reveals that the primary bifurcation is supercritical across all tested geometric parameter combinations. This is consistent with the finding of low linear transient growth amplifications at subcritical Reynolds numbers, being orders of magnitude lower than in similar channel flow set-ups.

Numerical investigation on heat transfer performance of matrix cooling channels for turbine trailing edges

The paper investigated numerically the heat transfer and pressure loss characteristics of the converging matrix cooling channels for turbine trailing edges with response surface method. The three selected design factors are scale factor ( SF), rib inclination angle ( α) and channel wedge angle ( β). The discussed range for the design factors, SF, α and β, are 2.5–10; 30°–60° and 1.5°–2.5°. And the investigated Reynolds number range is from 15,000 to 40,000. The turbulence model selected was SST k- ω model. It is newly found that the heat transfer and pressure loss characteristics of the converging matrix cooling channels depend heavily on the scaling effect. The matrix cooling channels with larger scale factor generally present higher heat transfer enhancement, higher pressure loss and lower overall thermal performance. In addition, the converging matrix cooling channels with smaller rib inclination angle and larger channel wedge angle present higher heat transfer enhancement and larger pressure loss. Among all the 13 cases, Case 9 with SF = 2.5, α = 45° and β = 1.5° has the highest averaged thermal performance factor under 6 Reynolds numbers.

3.8-octave broadband nearfield generation with high stability and high tolerance using a gradually varying thickness thin-film waveguide

The generation of an optical near-field spot through a gradually varying thickness waveguide composed of metallic and dielectric thin films was comprehensively analyzed by the finite element method. The incident angle of the excitation beam, excitation wavelength, and material dependent strength of the near-field hotspot were evaluated using three different material combinations. The analysis showed that the waveguide can generate a near-field spot with an electric field stronger than that of the excitation beam in the wide spectral range, reaching from visible 488 nm to mid-infrared 7000 nm (3.8-octave). From the wedge angle and excitation position dependency, the thin-film waveguide with varying thickness indicated the high stability, high freedom of design, and high tolerance to process precision. These manifold advantages progress optoelectronics, plasmonics, and nanotechnologies, including nanometric spectroscopy.