Compression Angle Research Articles

An analytical study for global buckling of circular tubes under axial and oblique compression

An analytical model is proposed for global buckling circular tubes of low diameter-to-thickness ratio (25<D/t<40) and moderate length (7<L/D<8), based on experimental observations and numerical simulations. Compared with FEM simulations, the current model gives accurate predictions on the whole load-displacement curve, energy dissipation and peak force.Employing this model, the energy absorption properties of circular metal tubes are analyzed. For global buckling tubes of same geometry, fixed boundary can absorb more energy than free boundary due to the bending plastic mechanism at ends. For oblique compression (compression angle ≤30°), the load-displacement curve of global buckling is similar to that of uniaxial compression. For tubes of different geometries under uniaxial compression, the total response and energy absorption ability are compared between global buckling and progressive buckling. If the effective stoke is small, the specific energy absorbing (SEA) of global buckling tube could be higher than progressive buckling tube.

Aberrant coordination geometries discovered in the most abundant metalloproteins.

ABSTRACTMetalloproteins bind and utilize metal ions for a variety of biological purposes. Due to the ubiquity of metalloprotein involvement throughout these processes across all domains of life, how proteins coordinate metal ions for different biochemical functions is of great relevance to understanding the implementation of these biological processes. Toward these ends, we have improved our methodology for structurally and functionally characterizing metal binding sites in metalloproteins. Our new ligand detection method is statistically much more robust, producing estimated false positive and false negative rates of ∼0.11% and ∼1.2%, respectively. Additional improvements expand both the range of metal ions and their coordination number that can be effectively analyzed. Also, the inclusion of additional quality control filters has significantly improved structure‐function Spearman correlations as demonstrated by rho values greater than 0.90 for several metal coordination analyses and even one rho value above 0.95. Also, improvements in bond‐length distributions have revealed bond‐length modes specific to chemical functional groups involved in multidentation. Using these improved methods, we analyzed all single metal ion binding sites with Zn, Mg, Ca, Fe, and Na ions in the wwPDB, producing statistically rigorous results supporting the existence of both a significant number of unexpected compressed angles and subsequent aberrant metal ion coordination geometries (CGs) within structurally known metalloproteins. By recognizing these aberrant CGs in our clustering analyses, high correlations are achieved between structural and functional descriptions of metal ion coordination. Moreover, distinct biochemical functions are associated with aberrant CGs versus nonaberrant CGs. Proteins 2017; 85:885–907. © 2016 Wiley Periodicals, Inc.

Oblique crushing performances of hybrid woven Kenaf fibre reinforced aluminium hollow cylinder

This paper presents crushing performances of hybrid woven kenaf fibre reinforced aluminium tubes under axial and oblique compression. According to open literature, lack number of works conducted to study the crushing responses when kenaf fibre in the form of woven is used to reinforce aluminium tubes. There are important parameters are used such as fibre orientations and oblique compression angles. Kenaf fibre in the form of woven is firstly wetted with polyester resin before it is wrapped around the tubes. After composite hardened, the hybrid tubes are quasi-statically compressed and force-displacement curves are recorded. Energy absorption performances are then determined and discussed in term of different fibre orientations and oblique angles. It is found that [±30°] fibre orientations capable to produce higher force-displacement responses and hybrid tubes are produced lower force ratio indicating the role of natural fibre in increasing the capability of energy absorptions.

New imaging characteristics for predicting postoperative neurologic status in patients with metastatic epidural spinal cord compression. A retrospective analysis of 81 cases

Background ContextSeveral clinical features have been proposed for the prediction of postoperative functional outcome in patients with metastatic epidural spinal cord compression (MESCC). However, few articles address the relationship between preoperative imaging characteristics and the postoperative neurologic status. PurposeThis study aims to analyze the postoperative functional outcome and to identify new imaging parameters for predicting postoperative neurologic status in patients with MESCC. Study DesignThis study is a retrospective consecutive case series of patients with MESCC who were treated surgically. Patient SampleWe assessed 81 consecutive patients who were treated with decompressive surgery for MESCC between 2013 and 2015. Outcome MeasuresEight imaging characteristics were analyzed for postoperative motor status by logistic regression models. Neurologic function was assessed using the Frankel grade preoperatively and postoperatively. MethodsThe following imaging characteristics were assessed for postoperative motor status: location of lesions in the spine, lamina involvement, retropulsion of the posterior wall, number of vertebrae involved, pedicle involvement, fracture of any involved vertebrae, T2 signal of the spinal cord at the compression site, and circumferential angle of spinal cord compression (CASCC). ResultsThe postoperative neurologic outcome was better than the preoperative neurologic status (p<.01). In the entire group, 40.7% of the patients were non-ambulatory before the surgical procedure, whereas 77.8% of the patients could walk after surgery (p=.01). In the multivariate analysis, the location of the lesions (odds ratio [OR]: 3.89, 95% confidence interval [CI]: 1.19–12.77, p=.02) and CASCC (OR: 2.31, 95% CI: 1.44–3.71, p<.01) were significantly associated with postoperative neurologic outcome. A CASCC of more than 180° was associated with an increased OR that approached significance, and the larger the CASCC, the higher the risk of poor postoperative neurologic status. ConclusionsThe postoperative neurologic status was dependent on the location of spine lesions and the CASCC. Patients with upper thoracic or cervicothoracic junction spine metastases or CASCC over 180° were at higher risk of relatively poor postoperative neurologic outcome. Timely, adequate surgical decompression is urgently warranted in these patients.

Nonlinear compression of picosecond chirped pulse from thin-disk amplifier system through a gas-filled hollow-core fiber**Project supported by the National Basic Research Program of China (Grant No. 2011CB808101), the Funds from the Chinese Academy of Sciences, and the National Natural Science Foundation of China (Grant Nos. 1112790, 10734080, 61221064, 60908008, and 61078037).

We theoretically study the nonlinear compression of a 20-mJ, 1030-nm picosecond chirped pulse from the thin-disk amplifier in a krypton gas-filled hollow-core fiber. The chirp from the thin-disk amplifier system has little influence on the initial pulse, however, it shows an effect on the nonlinear compression in hollow-core fiber. We use a large diameter hollow waveguide to restrict undesirable nonlinear effects such as ionization; on the other hand, we employ suitable gas pressure and fiber length to promise enough spectral broadening; with 600-μm, 6-bar (1 bar = 105 Pa), 1.8-m hollow fiber, we obtain 31.5-fs pulse. Moreover, we calculate and discuss the optimal fiber lengths and gas pressures with different initial durations induced by different grating compression angles for reaching a given bandwidth. These results are meaningful for a compression scheme from picoseconds to femtoseconds.

A Novel Elastographic Frame Quality Indicator and its use in Automatic Representative-Frame Selection from a Cine Loop

This study was aimed at developing a method for automatically selecting a few representative frames from several hundred axial-shear strain elastogram frames typically obtained during freehand compression elastography of the breast in vivo. This may also alleviate some inter-observer variations that arise at least partly because of differences in selection of representative frames from a cine loop for evaluation and feature extraction. In addition to the correlation coefficient and frame-average axial strain that have been previously used as quality indicators for axial strain elastograms, we incorporated the angle of compression, which has unique effects on axial-shear strain elastogram interpretation. These identified quality factors were computed for every frame in the elastographic cine loop. The algorithm identifies the section having N contiguous frames (N = 10) that possess the highest cumulative quality scores from the cine loop as the one containing representative frames. Data for total of 40 biopsy-proven malignant or benign breast lesions in vivo were part of this study. The performance of the automated algorithm was evaluated by comparing its selection against that by trained radiologists. The observer- identified frame that consisted of a sonogram, axial strain elastogram and axial-shear strain elastogram was compared with the respective images in the frames of the algorithm-identified section using cross-correlation as a similarity measure. It was observed that there was, on average (∼standard deviation), 82.2% (∼2.2%), 83.4% (∼3.8%) and 78.4% (∼3.6%) correlation between corresponding images of the observer-selected and algorithm-selected frames, respectively. The results indicate that the automatic frame selection method described here may provide an objective way to select a representative frame while saving time for the radiologist. Furthermore, the frame quality metric described and used here can be displayed in real time as feedback to guide elastographic data acquisition and for training purposes.

Radiological Prediction of Posttraumatic Kyphosis After Thoracolumbar Fracture.

Objectives:Classification methods that are currently being used for clinical decision making in thoracolumbar fractures, are limited by reproducibility and prognostic value. Additionally, they do not include kyphosis. As a posttraumatic kyphosis is related to persistent pain, it is of importance to determine a risk of posttraumatic kyphosis based on fracture type and patient characteristics.Purpose:To determine risk factors (AO classification, age, gender, localization) that may lead to progressive kyphosis after a thoracolumbar fracture. Materials and Methods:Retrospective radiographic analysis of a consecutive patientcohort that presented in our clinic with a traumatic fracture of the thoracolumbar spine between 2004 and 2011. Cobb angle, Gardner angle, vertebral compression angle and anterior vertebral body compression were measured on plain radiographs, direct post-trauma and at follow-up. Results:Age and localization are not significantly correlated, but there seems to be an increased risk of progression of kyphosis in age > 50 years and fractures localized at Th12 or L1. A3 type fractures are significantly more at risk for posttraumatic kyphosis compared to A1 and A2 type fractures. 30-50% of the A3 type fractures have an end Gardner angle and end vertebral compression angle of more than 20 degrees.Conclusion:AO-type A3 fractures appear to be at risk of progression of kyphosis. Localization at Th12-L1 and age above 50 years seem to be risk factors for significant posttraumatic kyphosis. These findings should be used in patient counseling and a meticulous evaluation by weekly radiographs is recommended to determine the treatment strategy of thoracolumbar fractures.

THE DESIGN METHOD RESEARCH FOR THE POSITION OF HIGH PRESSURE CAPTURING WING

The high pressure capturing wing configuration is a novel conceptual form which improves lift and lift-todrag ratios by the coupling relationship between the body and HCW. Based on the deign principle, the HCW position is determined by body compression shock and its own compression shock, while it is hard to obtain directly using theory. In order to solve this problem, this paper developed a kind of e ective method to design the position of capturing wing. The method is based on the analysis of parameters which determine the position of capturing wing, combined with the uniform experimental design method, the computational fluid dynamics analysis and surrogate model building to obtain the relationship between the position of capturing wing and the design parameters. The results from the validation case of cone body combination with capturing wing showed that this method can determine the optimal position of capturing wing in a large design space. In addition, cone compression angle, free field Mach number and blunted radius of capturing wing are the key parameters a ecting the position of capturing wing for the cone combination capturing wing. The results from the analysis of surrogate model showed that the position of capturing wing is in monotonic proportional relationship among the above three parameters.

이동속도의 증가에 따른 신발평가변인 분석

[PURPOSE] The purpose of this study was to analyze rearfoot control and impact force absorption variables with increments of running velocity, and provide essential data to enhance evaluation of sports shoes. [METHODS] Subjects in this study were ten healthy college students with normal foot function and without lower extremity injuries in the past year. Experimental shoes were shoes with a 50 of midsole hardness and 0.74 N/mm of bending stiffness. Motions of lower extremity at 3 different running velocities were analyzed through 3D cinematography and force platform. [RESULTS] Initial Achilles tendon angle, Initial 1/10 Achilles tendon angle, Maximal Achilles tendon angle were found to be larger than those reported in previous studies, but initial pronation was smaller while total pronation, compressive angle, torsion angle were similar. Most of the rearfoot angle and impact force absorption variables increased with increments of running velocity in comparisons with the previous studies. [CONCLUSIONS] These results indicate that some of the variables were extremely sensitive to running velocity while some were sensitive in a smaller range, and the other were not influenced by different running velocities. So, it is very important to control the running velocity if results should be compared for different shoes. The present study suggest that proper running velocity for shoe evaluation should be within 4㎧.

Compression Angle of Ossification of the Posterior Longitudinal Ligament and Its Clinical Significance in Cervical Myelopathy.

ObjectivesThe correction of clinical and radiologic abnormalities in patients with symptomatic ossification of the posterior longitudinal ligament (OPLL) is the current mainstay of treatment. This study aimed to identify radiographic predictors of severity of myelopathy in patients with symptomatic OPLL.MethodsFifty patients with symptomatic cervical OPLL were enrolled. Based on Japanese Orthopedic Association (JOA) scores, patients were divided into either the mild myelopathy (n=31) or severe myelopathy (n=19) group. All subjects underwent preoperative plain cervical roentgenogram, computed tomography (CT), and MR imaging (MRI). Radiological parameters (C2–7 sagittal vertical axis, SVA; C2–7 Cobb angle; C2–7 range of motion, ROM; OPLL occupying ratio; and compression angle) were compared. Compression angle of OPLL was defined as the angle between the cranial and caudal surfaces of OPLL at the maximum level of cord compressionResultsThe occupying ratio of the spinal canal, C2–7 Cobb angle, C2–7 SVA, types of OPLL, and C2–7 ROM of the cervical spine were not statistically different between the two groups. However, the OPLL compression angle was significantly greater (p=0.003) in the severe myelopathy group than in the mild myelopathy group and was inversely correlated with JOA score (r=-0.533, p<0.01). Furthermore, multivariate regression analysis demonstrated that the compression angle (B=-0.069, p<0.001) was significantly associated with JOA scores (R=0.647, p<0.005).ConclusionHigher compression angles of OPLL have deleterious effects on the spinal cord and decrease preoperative JOA scores.

A hybrid CFD/characteristics method for fast characterization of hypersonic blunt forebody/inlet flow

A hybrid CFD/characteristic method (CCM) was proposed for fast design and evaluation of hypersonic inlet flow with nose bluntness, which targets the combined advantages of CFD and method of characteristics. Both the accuracy and efficiency of the developed CCM were verified reliably, and it was well demonstrated for the external surfaces design of a hypersonic forebody/inlet with nose bluntness. With the help of CCM method, effects of nose bluntness on forebody shock shapes and the flowfield qualities which dominate inlet performance were examined and analyzed on the two-dimensional and axisymmetric configurations. The results showed that blunt effects of a wedge forebody are more substantial than that of related cone cases. For a conical forebody with a properly blunted nose, a recovery of the shock front back to that of corresponding sharp nose is exhibited, accompanied with a gradually fading out of entropy layer effects. Consequently a simplification is thought to be reasonable for an axisymmetric inlet with a proper compression angle, and a blunt nose of limited radius can be idealized as a sharp nose, as the spillage and flow variations at the entrance are negligible, even though the nose scale increases to 10% cowl lip radius. Whereas for two-dimensional inlets, the blunt effects are substantial since not only the inlet capturing/starting capabilities, but also the flow uniformities are obviously degraded.

Effect of Anode Structure on the Plasma Jet Characteristics of Arcjet Thruster

In order to study the effects of anode geometry on volt-ampere characteristics and plasma jet characteristics of the arcjet thruster, the arcjet thruster flow characteristics were simulated. Through numerical simulation, the velocity field and temperature field of thruster were calculated, and the volt-ampere characteristics were obtained at different anode geometry. The calculation results show that the influence of the anode throat diameter was the most obvious, compared to the influence of the anode throat length and compression angle on volt-ampere characteristics and plasma jet characteristic of the arcjet thruster.

Tests on Effects of Loading Rate on Modulus and Strength of Sandstone

For studying on the effects of loading rate on modulus and strength of sandstone, uniaxial compression experiment of the samples, from Balikun mine, was performed at different loading rates. The influence of loading rate on average modulus, uniaxial compressive strength and post-peak strength degradation angle was analyzed, and the results indicate that:: The average modulus of sandstone samples increases with loading rate increasing; the both almost obey linear relationship. The peak strength of sandstone grows with the increase of loading rate; there is an approximately exponential relationship between the two. With loading rate increasing, the post-peak strength degradation angle decreases; the relationship between the both is approximately exponential.

Multiobjective Design Optimization of a Cantilevered Ramp Injector Using the Surrogate-Assisted Evolutionary Algorithm

AbstractThe mixing efficiency of the fuel and the supersonic freestream has a great impact on the operation of the scramjet engine because of the very short residence time. In the current study, the cantilevered ramp injector was used to promote mixing of the fuel and the supersonic flow, and the injector’s configuration was optimized by the surrogate-assisted evolutionary algorithm—namely, the nondominated sorting genetic algorithm coupled with the Kriging surrogate model. In the optimization process, the swept angle, the ramp angle, the compression angle, the length of the step, and the diameter of the injector were considered as the design variables, and the mixing efficiency, the total pressure recovery efficiency, and the drag force were taken as the objective functions. Finally, the Pareto front for the multiobjective design optimization results was obtained, and the relationship between the objective functions was explored. The results show that optimized drag force increases with increased mixing ...

Quantitative comparison of striated toolmarks

A comparison of striated toolmarks by human examiners is dependent on the experience of the expert and includes a subjective judgment within the process.In this article an automated method is presented for objective comparison of striated marks of screwdrivers. The combination of multi-scale registration (alignment) of toolmarks, that accounts for shift and scaling, with global cross correlation as objective toolmark similarity metric renders the approach robust with respect to large differences in angle of attack and moderate toolmark compression. In addition, a strategy to distinguish between relevant and non-relevant spatial frequency ranges (geometric details) is presented.The performance of the method is evaluated using 3D topography scans of experimental toolmarks of 50 unused screwdrivers. Known match and known non-match similarity distributions are estimated including a large range of angles of attack (15, 30, 45, 60 and 75°) for the known matches. It is demonstrated that the system has high discriminatory power, even if the toolmarks are made at a difference in angle of attack of larger than 15°. The probability distributions are subsequently employed to determine likelihood ratios.A comparison of the results of the automated method with the outcome of a toolmark comparison experiment involving three experienced toolmark examiners reveals, that the automated system is more powerful in correctly supporting the hypothesis of common origin for toolmarks with a large difference in angle of attack (30°). In return, the rate of toolmark comparisons that yield incorrect support for the hypothesis of common origin is higher for the automated system.In addition, a comparison between estimating known match and known non-match distributions using 2D and 3D data is presented and it is shown that for toolmarks of unused screwdrivers, relying on 3D is slightly better than relying on 2D data.Finally, a comparison between estimating known match and known non-match distributions for two different types of screwdrivers suggests, that the method may be used for comparing marks of other tools as well.

Instability investigations of basaltic soil slopes along SH-72, Maharashtra, India

Mahabaleshwar is one of the most attractive and important destinations for tourists in Maharashtra, India, which experiences frequent slope failure due to high-intensity rain and complex geological conditions. The litho unit of the area is the Deccan Trap Basalt, the most famous consecutive basaltic flows during the late Cretaceous to Tertiary periods. The area is very susceptible to weathering, different degrees of alteration, formation of soils and occurrences of bole beds in between two consecutive basaltic flows. Soil formation process in this area is one of the most influencing factors for slope failure; in addition to this, joints, sub-vertical-to-vertical slopes, heavy rainfalls, etc. also play a pivotal role in instability. These transformed soils create instability on the slopes and ultimately converge to slope failures. Five types of soils have been identified during field investigations, petrographic study and X-ray diffraction that indicate change in composition and colour variations. Geomechanical properties viz. bulk density, grain size analysis, Atterberg limit, uniaxial compressive strength, cohesion and angle of internal friction were calculated for five types of soil samples. Effects of these soils on slope stability have been depicted with the help of numerical program Slide 6.0 based on limit equilibrium method.

Consistent Mode Mixity for the Interface Crack of the Bimaterial Disc under Diametric Compression Loading

The bimaterial disc specimen with central interface crack under diametric compression loading was simulated using the finite element method (FEM). The mode mixity for the interface crack was controlled by varying the compression angle. The consistent mode mixity independent of the assumed crack-extension size was obtained using the virtual crack closure technique (VCCT) by introducing an arbitrary normalizing length lG.The relations of the compression angle and the oscillation index ε to the consistent mode mixity were discussed with the simulation results. It found that the critical compression angles corresponding to pure mode ΙΙ got closed to 250 as the absolute value of ε was very small and a fitted formula of the critical compression angle and the absolute value of ε was also obtained.

Compressive Sensing-Based Angle Estimation for MIMO Radar with Multiple Snapshots

The issue of angle estimation for multiple-input multiple-output (MIMO) radar is studied and an algorithm for the estimation based on compressive sensing with multiple snapshots is proposed. The dimension of received signal is reduced to make the computation burden lower, and then the noise sensitivity is reduced by the eigenvalue decomposition (EVD) of the covariance matrix of the reduced-dimensional signal. Finally the signal subspace obtained from the eigenvectors is realigned to apply the orthogonal matching pursuit (OMP) for angle estimation. The angle estimation performance of the proposed algorithm is better than that of estimation of signal parameters via rotational invariance techniques (ESPRIT) algorithm, and reduced-dimension Capon. Furthermore, the proposed algorithm works well for coherent targets, and requires no knowledge of the noise. The complexity analysis and simulation results verify the effectiveness of the algorithm.

Uncertainty Assessments of Hypersonic Shock Wave-Turbulent Boundary-Layer Interactions at Compression Corners

Simulations of a shock emanating from a compression corner and interacting with a fully developed turbulent boundary layer are evaluated herein. Mission-relevant conditions at Mach 7 and Mach 14 are defined for a precompression ramp of a scramjet-powered vehicle. Two compression angles are defined: the smallest to avoid separation losses and the largest to force higher temperature flow physics. The Baldwin–Lomax and the Cebeci– Smith algebraic models, the one-equation Spalart–Allmaras model with the Catrix–Aupoix compressibility modification, and two-equation models, including the Menter shear stress transport model and the Wilcox k-! 98 and k-! 06 turbulence models, are evaluated. Comparisons are made to existing experimental data and Van Driest theory to provide preliminary assessment of model-form uncertainty. A set of coarse-grained uncertainty metrics are defined to capture essential differences among turbulence models. There is no clearly superior model as judged by these metrics. A preliminary metric for the numerical component of uncertainty in shock– turbulent-boundary-layer interactions at compression corners sufficiently steep to cause separation is defined as 55%. This value is a median of differences with experimental data averaged for peak pressure and heating and for extent of separation captured in new grid-converged solutions presented here.

Behavioural reconfigurable and adaptive data reduction in body sensor networks

Body area sensor networks have been attracting more and more applications which focus on human behaviour and monitoring, ranging from simple positioning to medical applications. These BSNs inherit unique specifications since are composed of light-weight embedded systems. In this paper, we focus on energy and lifetime requirements of these systems which is one of the most challenging design constraints. We study this problem from the angle of data compression and sampling which are both known to be very efficient in energy reduction specially when large amount of data is to be transmitted wirelessly. We introduce the notion of functional compression which utilises classes of data patterns to efficiently represent information through regenerative functions. Furthermore, we propose a reconfigurable compression methods which dynamically uses different compression methods to optimise compression ratio and energy savings. Later we study how sampling rate can be adaptively altered based on the behaviour of data pattern for further reduction in sample counts. We use the data from a wearable sensing system to illustrate the effectiveness of these methods which utilise the context and behaviour of the environment in system optimisation process.