Wedge Angle Research Articles

Prediction of Progressive Collapse in Osteoporotic Vertebral Fractures Using Conventional Statistics and Machine Learning.

Retrospective cohort study. The objective of this study was to determine prognostic factors for the progression of osteoporotic vertebral fracture (OVF) following conservative treatment. Few studies have evaluated factors associated with progressive collapse (PC) of OVFs. Furthermore, machine learning has not been applied in this context. The study involved the PC and non-PC groups based on a compression rate of 15%. Clinical data, fracture site, OVF shape, Cobb angle, and anterior wedge angle of the fractured vertebra were evaluated. The presence of intravertebral cleft and the type of bone marrow signal change were analyzed using magnetic resonance imaging. Multivariate logistic regression analysis was performed to identify prognostic factors. In machine learning methods, decision tree and random forest models were used. There were no significant differences in clinical data between the groups. The proportion of fracture shape ( P <0.001) and bone marrow signal change ( P =0.01) were significantly different between the groups. Moderate wedge shape was frequently observed in the non-PC group (31.7%), whereas the normative shape was most common in the PC group (54.7%). The Cobb angle and anterior wedge angle at diagnosis of OVFs were higher in the non-PC group (13.2±10.9, P =0.001; 14.3±6.6, P <0.001) than in the PC group (10.3±11.8, 10.4±5.5). The bone marrow signal change at the superior aspect of the vertebra was more frequently found in the PC group (42.5%) than in the non-PC group (34.9%). Machine learning revealed that vertebral shape at initial diagnosis was a main predictor of progressive vertebral collapse. The initial shape of the vertebra and bone edema pattern on magnetic resonance imaging appear to be useful prognostic factors for progressive collapse in osteoporotic vertebral fractures.

A comparative study of PSPVP and PSIBG inthe treatment of stageII-III Kummell's disease.

Percutaneous kyphoplasty (PKP) or percutaneous vertebroplasty (PVP) are commonly employed for Kummell's disease in stagesII-III; however, these techniques produce some complications. To compare the clinical efficacy and imaging results of percutaneous vertebroplasty + bone cement-augmented short-segment pedicle screw fixation (PSPVP) versus transpedicular intracorporeal bone grafting + pedicle screw fixation (PSIBG) in the treatment of stageII-III Kummell's disease. A total of 69 patients admitted between November 2017 and March 2021 were included in this study; 36 of these were treated with PSPVP, and 33 were treated with PSIBG. Patients in the two groups were compared in terms of perioperative, follow-up, and imaging data. No statistically significant differences were found between the two groups in terms of operation duration (P >0.05). However, the PSPVP group was superior to the PSIBG group in terms of incision length, intraoperative blood loss, and length of stay (P <0.05). All patients were followed up for more than 12 months. The VAS score, height of anterior vertebral margin, kyphosis Cobb angle, wedge angle of the affected vertebra at seven days after surgery and last follow-up, and the ODI index at the last follow-up of the two groups were significantly improved compared with figures before surgery (P <0.05). Compared with values before surgery, no statistically significant differences were found in the height of the posterior vertebral margin in the PSPVP group at seven days after surgery and at the last follow-up (P >0.05). There were also no statistically significant differences in the VAS score, ODI index, kyphosis Cobb angle, and wedge angle of the affected vertebra between the two groups at corresponding time points (P >0.05). The heights of the anterior and posterior vertebral margins in the PSIBG group were better than those in the PSPVP group after surgery and at the last follow-up (P <0.05). In the PSPVP group, a pedicle screw fracture occurred in one patient two months after surgery, while an upper adjacent vertebral fracture occurred in one patient eight months after surgery. Both PSPVP and PSIBG can achieve good early clinical efficacy in the treatment of stage II-III Kummell's disease, with PSPVP being relatively less invasive while producing a poorer orthopedic effect and more complications than PSIBG.

The study of functional outcome in traumatic thoracolumbar spine fractures treated with Moss-Miami instrumentation

Thoraco lumbar fractures are grave injuries of utmost concern. If left untreated may result in marked morbidity and disability to the patient. Most of the polytrauma patients suffer from spine fractures which in turn can be associated with neurological deficits which makes the treatment of the spine fractures an important entity. Hence the present study was undertaken to study efficacy, evaluate the clinical and radiographic results, to study the advantages, complications and to facilitate early mobilization of patients and thus helping easy nursing care of the patients in order to recreate a stable, pain free spinal column by using Moss-Miami (pedicular screw). This prospective study was undertaken in the department of orthopaedics KIMS hospital and research centre, Bangalore, conducted on 20 patients fulfilling the inclusion and exclusion criteria. This study was undertaken from December 2020 to June 2022. Patients were followed up at 6, 12 and 24 weeks for data collection. The mean age of the study group was 45.7 years. The most common vertebrae involved in this series were between T11-L2 to the extent up to 65%. Among all the subjects 75% were able to return to previous employment with some restriction 75% had occasional minimal pain with no need for medication. The results of this study demonstrate the superiority of pedicle screw-rod instrumentation as a treatment for vertebral fracture with very high statistical significance in restoration of vertebral body height, mean regional angle, mean anterior wedge angle and considerable amount of neurological healing.

Design of a concept wedge-shaped self-levelling railway sleeper

Differential railway track settlement can result in ballast voids, leading to sleepers that hang from the rail and are no longer supported by the ballast. These hanging sleepers are damage for track component. As a solution, this paper proposes and investigates a new concept sleeper with a wedge-shaped geometry, intended to stimulate the migration of ballast into any voids, thus reducing the occurrence of hanging sleepers. A series of scaled laboratory tests and 2D and 3D discrete element simulations are used to investigate different wedge-shaped geometries. The investigations include the wedge type (single long wedge versus multiple mini-wedges) and the wedge angle (30, 45, 60 degrees). First, the scaled laboratory tests are used to study the performance of different wedge geometries. Next, 3D DEM simulations are performed to analyse the contact forces in the ballast due to different wedge designs. Finally, 2D DEM simulations are performed to study the settlement behaviour. The main conclusions are that a single long wedge is preferable compared to multiple smaller wedges. when the wedge sleeper angle is larger than the ballast’s angle of repose, particles have the freedom to migrate into the settlement induced voids. Also, an increased wedge sleeper angle stimulates greater particle migration and thus improves the support correction. However the longer wedge also leads to a decrease in effective ballast height under sleeper which may make retrofitting on existing lines challenging.

Biomimetic Micropillar Wick for Enhanced Thin-Film Evaporation

Sustainable liquid cooling solutions are recognized as the future of thermal management in the chip industry. Among them, phase change heat transfer devices such as heat pipes and vapor chambers have shown tremendous potential. These devices rely on the physics of capillary-driven thin-film evaporation, which is inherently coupled with the design and optimization of the evaporator wicks used in these devices. Here, we introduce a biomimetic evaporator wick design inspired by the peristome of the Nepenthes alata that can achieve significantly enhanced evaporative cooling. It consists of an array of micropillars with multiple wedges along the sidewall of each micropillar. The efficacy of the wedged micropillar is evaluated based on a validated numerical model on the metrics of dryout heat flux and effective heat transfer coefficient. The wedge angle is chosen such that wedged micropillars cause liquid filaments to rise along the micropillar vertical walls. This results in a significant increase in thin-film area for evaporation. Additionally, the large mean curvature of the liquid meniscus produces strong capillary pumping pressure and simultaneously, the wedges increase the overall permeability of the wick. Consequently, our model predicts that the wedged micropillar wick can attain ∼234% enhancement of dryout heat flux compared to a conventional cylindrical micropillar wick of similar geometrical dimensions. Moreover, the wedged micropillars can also attain a higher effective heat transfer coefficient under dryout conditions, thus outperforming the cylindrical micropillar in terms of heat transfer efficiency. Our study provides insight into the design and capability of the biomimetic wedged micropillars as an efficient evaporator wick for various thin-film evaporation applications.

Mode I interlaminar fracture toughness of two-dimensional continuous fiber reinforced ceramic matrix composites using wedge-loaded double cantilever beam method

In this study, the wedge-loaded double cantilever beam (W-DCB) method was applied to evaluate the mode I interlaminar fracture toughness of two-dimensional (2D) continuous fiber-reinforced ceramic matrix composites (CMCs). Based on the elastic foundation theory, a W-DCB model was built and its compliance formula was derived by considering the axial force effect, shear effect, asymmetric propagation, and incomplete interlaminar contact. The friction effect was analyzed and measured using the theory of error transfer and a quasi-in-situ measurement method, respectively. The results reveal that rational selection of the wedge angle and friction coefficient can reduce the friction effect. Meanwhile, the W-DCB formula was comprehensively verified by compliance curves, crack tip behaviors, and the cohesive zone of 2D CMCs, which demonstrates its accuracy in conjunction with the experimental data. Finally, the energy release rate (ERR) of the 2D CMCs calculated using the W-DCB theory was consistent with the measured data.

Functional and Surgical Outcomes of Corpectomy in Patients with Unstable Spinal Fractures.

Unstable fractures of the spine should be managed surgically. An anterior approach allows for precise decompression of the vertebral canal and reconstruction of the fractured vertebral body. The aim of the study was to evaluate the functional and surgical outcomes of anterior surgical approaches for vertebral body removal and prosthetic reconstruction. The objectives of this paper were accomplished by reviewing the course of treatment and treatment outcomes of patients operated on at the Orthopaedic Oncology Department in Brzozw and the Department of Orthopaedics and Traumatology in District Hospital in Stalowa Wola in the years 2020-2021. In total, the treatment of 54 patients was analyzed. The study only included patients with traumatic and pathological fractures who underwent a single-level corpectomy. A total of 18 patients with fractures of the cervical spine, 15 of the thoracic spine and 21 of lumbar spine were treated. Before and after treatment, patients&apos; neurological status was assessed according to the Frankel classification, performance was assessed with the Karnofsky score and pain intensity was analyzed with a VAS. The vertebral wedge angle (alpha), the ratio of the anterior height of the fractured vertebral body to the anterior height of the upper adjacent vertebral body (a/c), the ratio of the anterior height to the posterior height of the fractured vertebra (a/b) and the distance between the vertebral endplates adjacent to the fractured vertebra, measured between their anterior edges (A-B) were assessed. The most common general medical and surgical complications were also evaluated. After the surgery, significant pain relief measured using a VAS was noted (the median was 7 preoperatively and 4 postoperatively) and an improvement in performance according to the Karnofsky score was observed (the median was 50 preoperatively and 70 postoperatively). Out of the 14 patients with neurologic deficits 11 improved, while 5 regained the ability to walk. In four patients, the implant migrated into an adjacent vertebra and three patients suffered a fracture of the upper adjacent vertebra. The correction of the spine deteriorated in all 7 patients. There was no postoperative neurological deterioration of patients and no infectious complications. During the surgery, three patients suffered dura mater injury, which was identified intraoperatively and repaired. 1. Corpectomy followed by vertebral body replacement is an effective and safe method that enables the restoration of the shape of the vertebra, restoration of the physciological spinal curvature and direct neural decompression. 2. The treatment outcomes are good. Pain significantly decreases and performance improves in most patients. 3. Treatment complications are rare. The most often observed complication was migration of the implant into an adjacent vertebral endplate, fractures above the place of fixation and dura mater injury.

Spontaneous Transport Mechanics of Water Droplets under a Synergistic Action of Designed Pattern and Non-Wetting Gradient.

The controllable spontaneous transport of water droplets on solid surfaces has a broad application background in daily life. Herein, a patterned surface with two different non-wetting characteristics was developed to control the droplet transport behavior. Consequently, the patterned surface exhibited great water-repellant properties in the superhydrophobic region, and the water contact angle reached 160° ± 0.2°. Meanwhile, the water contact angle on the wedge-shaped hydrophilic region dropped to 22° after UV irradiation treatment. On this basis, the maximum transport distance of water droplets could be observed on the sample surface with a small wedge angle of 5° (10.62 mm), and the maximum average transport velocity of droplets was obtained on the sample surface with a large wedge angle of 10° (218.01 mm/s). In terms of spontaneous droplet transport on an inclined surface (4°), both the 8 μL droplet and 50 μL droplet could move upward against gravity, which showed that the sample surface possessed an obvious driving force for droplet transport. Surface non-wetting gradient and the wedge-shaped pattern provided unbalanced surface tension to produce the driving forces in the process of droplet transport, and the Laplace pressure as well is produced inside the water droplet during this process. This work provides a new strategy to develop a patterned superhydrophobic surface for droplet transport.

Advantages of Posterior Indirect Decompression Surgery in Thoracolumbar Burst Fractures with Neurologic Symptoms

Objective: Approximately 90% of spinal fractures occur at the thoracolumbar (T-L) junction and may be accompanied by neurological symptoms, in which decompression and post-fixation are generally performed. However, decompression surgery can aggravate patients’ symptoms due to adverse incidents, such as developing postoperative hematomas or iatrogenic spinal cord injury. This study compared the surgical and radiographic outcomes of patients with T-L junction burst fractures and neurological deficits who underwent direct or indirect decompression.Methods: We retrospectively reviewed all patients who had undergone posterior surgical treatment for T-L junction burst fractures with neurologic deficits. Patients were classified according to the procedure: indirect decompression (group 1) or spinal decompression through laminectomy and facetectomy (group 2). Clinical results and radiologic findings were compared between the two groups for 2 years.Results: Among 57 patients who met the inclusion criteria, 29 were categorized into group 1, and 28 were categorized into group 2. Group 1 had a statistically significantly lower Oswestry Disability Index score than group 2 at the final follow-up visit (p=0.03). In group 1, both the T-L junction angle and wedge angle of the injured vertebrae improved significantly, both immediately after surgery (p=0.02 and p=0.01, respectively) and at the final follow-up visit (p=0.01 and p=0.01, respectively). In group 2, the difference between the pelvic incidence and lumbar lordosis was significantly greater than in group 1 at the final follow-up visit (p=0.02).Conclusion: This study confirmed that symptoms could be sufficiently improved with indirect decompression, which should be kept in mind for cases where it is difficult to perform direct decompression,

Impact of Microstructures on the Movement of Droplets Regulated by Bioinspired Functional Wedge‐Shaped Surfaces

At present, bioinspired functional surfaces have garnered widespread research attention due to the application of directional droplets movement. Herein, inspired by the anisotropic of rice leaves and conical structures of cactus, a bionic wedge‐shaped surface with microstructure of “rice leaf” based on the laser method is reported. In addition, the impact of the microstructure geometrical parameters in the wedge‐shaped surface on the droplet moving anisotropy and manipulation capacity is discussed. Herein, it is found that the movement distance of droplets is effectively improved by regulating the rib‐like microstructure topography and changing the wedge angle. Meanwhile, the movement distance and spreading direction of droplets are controlled by constructing an alternating interface. The results demonstrate that the droplet got optimal displace distance, up to 13 mm by 6.43 s, with the rib‐like microstructure of 0.03 mm and the wedge angle of 10°. When the droplet volume is 40 μL, the droplet is able to separate from the control distance in the alternating interface, after that the droplet moves along the new microstructure direction in the wedge‐shaped surface. Herein, it provides a useful reference for droplet directional movement and water collection.

Efficacy of percutaneous kyphoplasty on vertebral compression fractures with different bone mineral densities: a retrospective study

BackgroundThis study was performed to investigate the clinical efficacy of percutaneous kyphoplasty (PKP) for vertebral compression fractures with different bone mineral densities (BMD).MethodsWe performed a retrospective analysis of 232 patients with single-segment vertebral compression fractures who underwent PKP. Patients were divided into the normal BMD, osteopenia, and osteoporosis groups according to their average lumbar BMD before surgery. The visual analog scale (VAS) was used to compare differences in pain relief before and after surgery in each group. Corrections of the wedge angle and kyphotic angle before and after surgery were observed using anteroposterior and lateral radiographs and compared among the groups, as was the incidence of bone cement leakage.ResultsPatients were followed up for 6–12 months, with an average follow-up time of 9.12 ± 1.68 months. The VAS score, wedge angle, and kyphotic angle of the three groups of patients decreased significantly at the end of the follow-up (P < 0.05). The changes in VAS score and wedge angle correction in the osteoporosis group were significantly larger than those in the normal BMD and osteopenia groups (P < 0.05). There were no significant differences among the three groups in terms of kyphotic angle correction or bone cement leakage rates (P > 0.05).ConclusionsPKP has a positive effect on vertebral compression fractures with different BMD, and is especially suitable for osteoporotic vertebral compression fractures.

Equivalent values between anterior vertebral height, wedge ratio, and wedge angle for evaluating vertebral mobility and deformity in osteoporotic vertebral fractures: a conventional observational study

BackgroundVertebral mobility (V-mobility) has been used to diagnose fresh osteoporotic vertebral fractures (OVFs) and determine bone union by setting cutoff values for these purposes. V-mobility is the difference in vertebral height on dynamic radiographs taken in the sitting and lateral decubitus or supine positions. The dimensions for V-mobility were presented as anterior vertebral height (Ha; mm), wedge ratio (WR; %), and wedge angle (WA; °) in previous reports. This study was performed to obtain WR and WA values equivalent to V-mobility of 1.0 mm in Ha.MethodsLateral radiographs of 284 OVFs (grade 1–3 deformed vertebrae) from T11 to L2 were obtained from 77 patients with OVF. V-mobility presented as Ha, posterior vertebral height, and WA was obtained by the difference in these dimensions on dynamic radiographs. The WR and WA values equivalent to 1.0 mm in Ha were obtained by dividing the V-mobility values for WR and WA by that for Ha.ResultsThe mean WR values corresponding to 1.0 mm in Ha for grade 1, 2, and 3 vertebrae were 3.2% ± 1.4%, 3.2% ± 0.9%, and 3.4% ± 1.0%, respectively, and the corresponding value for grade 1–3 vertebrae was 3.3% ± 1.0%. The mean WA values corresponding to 1.0 mm in Ha for grade 1, 2, and 3 vertebrae were 1.5° ± 0.8°, 1.5° ± 0.6°, and 1.5° ± 0.8°, respectively, and the corresponding value for grade 1–3 vertebrae was 1.5° ± 0.7°.ConclusionsThe WR and WA values equivalent to V-mobility of 1.0 mm in Ha were 3.3% and 1.5°, respectively, in grade 1–3 vertebrae. These findings may be useful to secure a reliable value of V-mobility of OVFs using simultaneous measurements in three dimensions (Ha, WR, and WA) in clinical practice and to establish cutoff values for V-mobility to determine bone union.

Intelligent backpropagated predictive networks for dynamics of the power-law fluidic model with moving wedge and flat plate

A novel application of intelligent computing is presented to study the dynamics of the power-law fluidic problem (PLFP) of moving-wedge and flat-plate models using a multilayer structure of feedforward neural networks (FFNNs) optimized with the Levenberg-Marquardt method (LMM), i.e. FFNN-LMM. The reference dataset for inputs and targets of FFNNs is generated through the Adams numerical solver for the non-Newtonian power-law fluidic system in the case of dilatant, pseudo-plastic, and other thinning/thickening fluids with different values of wedge angle and velocity ratio parameters. The designed FFNNs backpropagated with LMM are constructed with the help of arbitrary samples for training, testing, and validation via mean squared error (MSE)-based figure of merit. Comparison of the proposed computing platform FFNN-LMM with reference standard solutions in terms of MSE, state transition statistics of the algorithm, error histogram studies, and regression outcomes endorse the accuracy and convergence for solving different scenarios in PLFPs.

Density field measurement deflectometry for supersonic wind tunnels.

A method for the quantitative measurement of two-dimensional density field distributions based on deflectometry is proposed. With this method, from the point of view of the inverse Hartmann test, the light rays emitted from the camera reach the screen after being disturbed by the shock-wave flow field. After the coordinates of the point source are obtained by using the phase information, the deflection angle of the light ray can be calculated, and then the distribution of the density field can be determined. The principle of density field measurement deflectometry (DFMD) is described in detail. In the experiment, the density fields in wedge-shaped models with three different wedge angles are measured in supersonic wind tunnels, the experimental results from the proposed method are compared with the theoretical results, and the measurement error is found to be around 2.76 × 10-3kg/m3. This method has the advantages of fast measurement, a simple device, and low cost. It provides a new approach, to the best of our knowledge, to measuring the density field of a shock-wave flow field.

FOIL ACTIVATION TECHNIQUE-A TOOL FOR THE EVALUATION OF PHOTO-NEUTRON DOSE IN RADIOTHERAPY.

Treatment of cancer is carried out using photon beams from high-energy medical linear accelerators. Photo-neutrons are also produced as an unwanted by product in the process of dose delivery to the cancer patients during their radiation treatments. In the present study, photo-neutron dose equivalents (both thermal and fast components) per unit delivered gamma-photon dose were measured at different depths, as function of distances from iso-centre in patient plane, field sizes, wedge angles and at LINAC head for a 15-MV medical linear accelerator model Elekta Precise using multi-foil activation technique. The neutron dose equivalents determined for the above-mentioned parameters were found to be lower (<0.05%) in comparison with the therapeutic photon dose delivered and within the prescribed limits recommended by the national regulatory authority.

Analytical and Numerical Simulation of Surface Pressure of an Oscillating Wedge at Hypersonic Mach Numbers and Application of Taguchi's Method

This paper aims to estimate the surface pressure of a wedge at hypersonic Mach numbers at a considerable angle of incidence. The Ghosh similitude, corresponding strip theory, and piston theory are used to determine the pressure distribution analytically, and the results are compared to those of the CFD analysis. The theory is valid when the shock wave is attached to the leading edge of the nose of the wedge. Pressure on the windward surface was considered in the analysis. The pressure on the Lee surface is neglected. The condition for the validity of the theory is that the Mach number M2 behind the shock wave is greater than 2.5. The parameters taken into account for the study are the wedge angle and Mach number. The range of wedge angle considered is from 5 to 25 degrees and the Mach number considered is from 5 to 15. The analytical and the CFD results are in good agreement. The findings indicate that the parameters like wedge angle and Mach number are influential parameters that influence the wedge surface static pressure. The surface static pressure rises with an increase in Mach number and wedge angle.

Numerical exploration of forced convection hydromagnetic hyperbolic tangent nanofluid flow over a permeable wedge with melting heat transfer

In this communication, the joint impacts of the process of melting as well as wedge angle entity on hydromagnetic hyperbolic tangent nanofluid flow owing to permeable wedge-shaped surface in the incidence of suspended nanoparticles along with radiation, Soret and Dufour numbers are scrutinized. The mathematical model which represents the system consists of a system of highly non-linear coupled partial differential equations. These equations are solved using a finite-difference-based MATLAB solver which implements the Lobatto IIIa collocation formula and is fourth-order accurate. Further, the comparison of computed results is carried out with the previously reported articles and outstanding conformity is recorded. Emerged physical entities affecting the bearings of tangent hyperbolic MHD nanofluid velocity, distribution of temperature, and concentration of nanoparticles are visualized in graphs. In another line, shearing stress, the surface gradient of heat transfer, and volumetric rate of concentration are recorded in tabular form. Most interestingly, momentum boundary layer thickness and thicknesses of thermal as well as solutal boundary layers enhance with an increment of Weissenberg number. Moreover, an increment on tangent hyperbolic nanofluid velocity and decrement on the thickness of momentum boundary layer is visualized for the increment of numerical values of power-law index entity, which can determine the behavior of shear-thinning fluids.This study has applications for coating materials used in chemical engineering, such as strong paints, aerosol manufacturing, and thermal treatment of water-soluble solutions.

Prognostic factors of balloon kyphoplasty for osteoporotic vertebral fractures with diffuse idiopathic skeletal hyperostosis.

The authors aimed to determine the poor prognostic factors of balloon kyphoplasty for the treatment of fractures of the most distal or distal-adjacent vertebrae in ankylosing spines with diffuse idiopathic skeletal hyperostosis (DISH). Eighty-nine patients with fractures of the most distal or distal-adjacent vertebrae of ankylosing spines with DISH were included and divided into two groups: those with (n = 51) and without (n = 38) bone healing 6 months postoperatively. Clinical evaluation included age, sex, time from onset to surgery, the visual analog scale score for low-back pain, and the Oswestry Disability Index (ODI). The VAS scores and ODI were measured both preoperatively and at 6 months postoperatively. Radiological evaluations included bone density; wedge angles of the fractured vertebrae in the supine and sitting positions on lateral radiographs; differences in the wedge angles (change in wedge angle); and the amount of polymethylmethacrylate used. The preoperative ODI, vertebral wedge angles in the supine and sitting positions, change in wedge angle, and amount of polymethylmethacrylate were significantly different between the two groups and were significantly associated with delayed bone healing in univariate logistic regression analysis. Multivariate logistic regression analysis showed that only a change in the wedge angle was significantly associated with delayed healing, with a cutoff value of 10°, sensitivity of 84.2%, and specificity of 82.4%. Treatment with balloon kyphoplasty alone should be avoided in patients with a difference ≥ 10° in the wedge angle of the fractured vertebrae between the supine and sitting positions.

Mach reflection of detonation wave on porous wall

This study reports the Mach reflection of gaseous detonation on porous wedges experimentally, in which the porous wall is consisted of equidistant inline square columns. The smoked foil technique was utilized to monitor the evolution of the triple-point trajectory and detonation cells in the Mach stem region. In addition to the wedge angle and initial pressure of gaseous mixture, this paper also focuses on the effect of porosity and pore size on the Mach reflection and its mechanism. The results show that the strength of the Mach stem is significantly weakened by the porous media compared with that on the smooth wedge, which is ascribed to the diffraction and reflection waves generated by the interaction of the Mach stem front with the pore. Furthermore, the onset of the triple-point trajectory is delayed, the angle of which is decreased. The porosity and pore size present distinct influence on the Mach stem height. With the increase in the porosity and the decrease in the pore size, the Mach stem region is attenuated more dramatically and the Mach stem is harder to be formed or even could not be observed. Furthermore, the triple-point trajectory on the porous wall exhibits local self-similarity and satisfies the frozen limit in the near field and the equilibrium limit in the far field. However, the lengths of the existence of the frozen limit and the transition to the equilibrium limit on the porous wall are found to be much shorter than the hydrodynamic thickness, and the recovery of the self-similarity depends largely on the porosity and pore size.

직선형 파동유도관에서 벽면 쐐기의 길이에 따른 초음파 전파

This study focuses on the ultrasonic propagation along the wedge length of the wall in a straight waveguide designed to reduce the minimum detection distance of an ultrasonic sensor for distance measurement. Wedges are created on the waveguide wall to avoid ultrasound interference caused by reflection on a smooth wall, and the wedge dimensions must be chosen carefully. The magnitude of the ultrasonic signal was evaluated according to the wedge length in terms of the ratio of the target reflection to the exit reflection while maintaining the wedge angle selected in the previous study. The propagation of ultrasonic waves was studied using finite element analysis. The wedge length that maximizes the magnitude of the ultrasonic signal was found to be similar to the wavelength. It was possible to reduce unwanted reflection and increase target reflection by adjusting the waveguide wall wedge length.