Longitudinal Angle Research Articles

Regional LV deformation in healthy individuals during isovolumetric contraction and ejection phases assessed by 2D speckle tracking echocardiography

The main purpose of the this human study was by speckle tracking imaging to characterize the regional and temporal distribution of normal left ventricular (LV) deformation and the LV geometry during isovolumetric contraction (IVC) and the ejection phase. Twelve healthy young men [22 (2·3) years] were included. Longitudinal and circumferential strain and local twist angle were measured at four LV short-axis levels: basal, papillary, subpapillary and apical level during IVC and ejection phases. In addition, LV length from apex to the atrio-ventricular level, two diameters at LV basal short-axis level and atrio-ventricular plane displacement (AVPD) were measured to characterize LV shape during IVC. During IVC, longitudinal and circumferential shortening was demonstrated at all four short-axis levels from base to apex, while the LV made a basal counterclockwise and apical clockwise rotation representing untwist. In addition, there was a reduction in LV length and changes in short-axis diameters at basal level and AVPD from end-diastole to end-IVC, reflecting that the LV changed from an oval to a more spherical shape. At end-systole, longitudinal and circumferential shortening and local twist angle were significantly increased towards apex (P<0·05). This study demonstrated that the IVC in healthy humans is characterized by regional longitudinal and circumferential shortening and LV untwist, which occurs parallel to geometric changes of the LV into a spherical shape. During ejection, increased regional gradients of LV deformation towards apex in LV longitudinal and circumferential shortening and local and net twist angle were demonstrated.

Quantifying differences in local wall stress between carotid and femoral arteries

ObjectiveArterial remodeling after vascular procedures are mediated by pulsatile stress, but arterial wall biomechanics likely contribute; this study defines differences in arterial wall stress between healthy femoral and carotid arteries.MethodHealthy nonhuman primate arteries were tested on a custom‐made device to determine biaxial mechanical responses. A custom LABVIEW program was using for data acquisition and processing. Local wall stress was calculated based on a nonlinear, finite deformation framework utilizing an orthotropic material model. Residual stresses were considered in the analysis through quantifying circumferential and longitudinal opening angles. Heteroscedastic t‐tests were used to analyze the results.ResultsThe pressure‐diameter response of the arteries at the in vivo stretch demonstrate that femoral are stiffer than the carotid arteries (P=0.05); Fig. 1. Circumferential opening angle results (Fig. 2) also show a trend toward a greater opening angle in the femoral arteries (P=0.3).ConclusionsThese results support baseline biomechanical differences between femoral and carotid arteries in nonhuman primates. A better understanding of the matricellular differences between arteries may provide improved compatibility strategies for future therapies.(RLG:GTEC Foundation Endowment; NIH, NSF)

Cervical Transpedicular Fixation Aided by Biplanar Flouroscopy

PURPOSE; To evaluate the accuracy of fluoroscopyassisted cervical transpedicular fixation in different pathologies. 28 men and 17 women aged 34 to 65 (mean, 41) years underwent 210 one-stage cervical transpedicular fixations. The indications were trauma (n=35), degenerative disease leading to cervical spondylotic myelopathy (n=4), tumours (n=4), and Pott's disease (n=2). Regarding the 35 trauma patients, fractures were at C5-C6 (n=22), C4-C5 (n=8), and C3-C5 (n=5); 16 of them had dislocated vertebrae, of whom 13 had cervical disc herniation. Two of the patients with degenerative disease underwent additional laminectomy. Both anterior and posterior surgeries were performed for the 2 of the patients with tumours; all other patients underwent posterior surgery only. The length, diameters, and frontal, sagittal, and longitudinal angles of all pedicle screws were calculated. The dominant vertebral artery was detected using Doppler ultrasonography. Biplanar fluoroscopy was also used. Postoperatively, patients were allowed to mobilise at day 1; a collar was not used. The position of the pedicle screws was graded. The mean operating time was 105 (range, 90-155) minutes. The mean follow-up period was 26 (range, 17-34) months. Of the 210 pedicles fixed, 192 (91%) were at the correct screw position (grade I), 16 (8%) were at an acceptable position (grade II), and 2 (1%) were completely perforated but without morbidity (grade III). The overall perforation rate was 9%. There were no neurovascular injuries or instrumentation-associated complications (failure of implant components, screw loosening, or lucent zone formation around the pedicle screws). The fusion rate was 100%. Cervical transpedicular fixation provides strong stabilisation. With the aid of biplanar fluoroscopy, the risk of pedicle perforation was about 8%, but no neurovascular injury was ensued.

Undercarriage Lateral Tip-Over Criteria: a Parametric Study

URING the conceptual design phase of aircraft design, the integrationoftheundercarriagesystemisveryimportant,andit is often difficult to achieve the first time. The positioning of the undercarriage requires that the ground handling longitudinal and lateral stabilities of the aircraft are within certain geometric limits to ensure safe parking, taxiing, and takeoff rotation requirements. These geometric limits are based on the longitudinal and vertical positions of the aircraft cg and the range of cg travel as fuel is consumed and payload is loaded/unloaded. However, the aircraft cg is also influenced by the undercarriage placement. Furthermore, the stowagerequirementoftheundercarriagehasanimportantimpacton available internal volume for fuel and payload. The current design practice for undercarriage integration in the aircraft conceptual design phase is very much iterative, and it is somewhat of a hit and miss affair [1–3]; however, Currey [4] does provide some design equations to assist in the geometric development and design of the undercarriage layout. Currey’s approach is to assume the aircraft cg position on the aircraft fuselage and the wings are positioned accordingly (for flight stability requirements). Themainwheelsarethenpositionedtoachievetheappropriaterange of weight on the wheels (i.e., WMLG � 0:9WTO) and longitudinal tipback angle criterion. The longitudinal tipback angle criterion is based on tail strike angle, and it is determined using the stall angle of attack and nose or tail wheel positioned for best weight distribution. Thus, the aircraft geometric wheel base (WB) is determined. Wheel track(WT)dimensionisestimated,andonasketchoftheaircraft,the lateral tipover stability angle is measured and compared with the design best practice. Finally, wing-mounted stores, wing tips, and wing-mounted engine pod lateral clearances are checked. Then, as the undercarriage details are further developed (tire sizes, strut lengths,andpivotpoints)andrealaircraftweightsareknown,thetrue cgpositionisfoundandtheundercarriagepositiondesignischecked and revised accordingly. This process will be repeated several times during the development and modification of the aircraft conceptual design process. Theaimofthispaperistoprovideasetofundercarriagegeometric development design charts and relationships to assist the systems integration designer in determining an optimized geometric positioning of the undercarriage early in the conceptual design phase of the aircraft. This study is focused on conventional tricycle undercarriage systems based on a single nose strut and two main wheel struts. There are a number of assumptions used in this study to aid in the development of the parametric design options. These assumptions are as follows: 1) The cg vertical position above the ground is such that the angle between the cg vertical position and the main undercarriage ground

Span-wise wind fluctuations in open terrain as applicable to small flying craft

AbstractMicro air vehicles (MAVs) are typically of low mass and moment of inertia and have flight speeds comparable to birds and the larger insects. Such craft traverse the lower levels of the atmospheric boundary layer (ABL) which is a significantly different environment than that experienced by larger manned aircraft, which spend the majority of their time in relatively clean air and fly at speeds significantly higher than typical wind speeds in the ABL. Here a new series of measurements dedicated to understanding spatial and temporal velocity fields that MAVs experience are presented. Atmospheric wind measurements were taken by sampling four multi-hole dynamic pressure probes spanned perpendicular to the oncoming wind at spans of between 0·014m and up to 0·45m. It was noted that the variation of both longitudinal velocity and flow pitch angle against spacing followed a fractional power law and as such large variations were present even for the smallest inter-probe separations. This effect is thought to explain the increasing piloting difficulties experienced in maintaining good roll control for decreasing scales of craft.

Interventionelle Schmerztherapie mittels Ballon-Kyphoplastie bei Patienten mit osteoporosebedingten Insuffizienzfrakturen des Os sacrum

In older patients with reduced bone quality, fatigue fractures of the os sacrum are relatively common and are typically accompanied by strong, disabling pain. The aim of our study was to verify the feasibility and safety of sacroplasty using a balloon catheter as well as the reduction of pain. 25 patients were diagnosed with an os sacrum fracture in MRI. As a manifestation of an extant bone reconstruction process, all patients were diagnosed with distinctive edema on the basis of MRI strong T 2-weighted images. CT-controlled balloon sacroplasty was performed in all patients. To allow the cement to be dispensed at a longitudinal angle to the fracture, the balloon catheter is directed through a hollow needle in the os sacrum either from the caudal to the cranial direction or from the craniodorsal to the caudoventral direction. The thus created cavity was then filled with PMMA cement. A control CT and a conventional X-ray in two planes were then carried out. The pain intensity was defined by means of VAS before the intervention, on the second day, and 6 and 12 months after the intervention. The balloon sacroplasty yielded good technical performance in every patient. The control CT and the X-ray control of the os sacrum showed adequate distribution of the cement, and cement leakage was not detected. Before the operation, the average pain encountered was in accordance with VAS 8.3. On the second postoperative day, a considerable reduction with an average of 2.7 was reported, and this remained stable with an average of 2.5 after 6 and 12 months. Balloon sacroplasty is an effective treatment method for fast pain relief in patients with fatigue fractures of the os sacrum.

Influence of Interpersonal Geometrical Variation on Spinal Motion Segment Stiffness

A validated finite element model of an L3-L4 motion segment is used to analyze the effects of interpersonal differences in geometry on spinal stiffness. The objective of this study is to determine which of the interpersonal variations of the geometry of the spine have a large effect on spinal stiffness. This will improve patient-specific modeling. The parameters that define the geometry of a motion segment are vertebral height, disc height, endplate width, endplate depth, spinous process length, transverse process width, nucleus size, lordosis angle, facet area, facet orientation, and the cross-sectional areas of the ligaments. All these parameters differ between patients. The influence of each parameter on spinal stiffness is largely unknown and such knowledge would greatly help in patient-specific modeling of the spine. The range of interpersonal variation of each of the geometric parameters was set at mean±2SD (covering 95% of the population). Subsequently, we determined the effect of each of these ranges on the bending stiffness in flexion, extension, axial rotation, and lateral bending. Disc height had the largest influence; a maximal disc height reduced the spinal stiffness to 75-86% of the mean motion segment stiffness, and a minimal disc height increased the spinal stiffness to 154-226% of the mean motion segment stiffness. Lordosis angle, transversal and longitudinal facet angle, endplate depth, and area of the capsular ligament also had a substantial influence (>5%) on the stiffness, but considerable less than the influence of the disc height. Ligament areas, nucleus size, spinous process length, and length of processes are of negligible effect (<2%) on the stiffness. The disc height should be accurately determined in patients to estimate the spinal stiffness. Ligament areas, nucleus size, spinous process length, and transverse process width do not need patient-specific modeling.

Defects Inspection of Steel Ball Based on Optical Fiber Sensing Technique

Surface quality of bearing ball is one of important factors to improve service performance. It is difficult to detect bearing ball surface defects with high precision and low cost by conventional methods. In this paper one new classification method based on optical fiber sensing technology was put forward from the longitudinal section angle. Inspection mechanism of Y-type and coaxial fiber sensor were analyzed, the mathematical models of the two fiber sensors were established and numerical simulations were realized by Matlab software. Influence of optical fiber parameters on light intensity modulation characteristic regulation was studied. Light intensity modulation characteristic experiments were done with specimens of different reflectivity and processing methods. The results show optical fiber sensing technique is an effective method to separate different surface of steel ball with extracting of two parameters displacement and surface reflectivity.

Performance Optimization of the FGX Dry Separator for Cleaning High-Sulfur Coal

The main goal of the present study was not only to deshale (remove pure rock) raw coal extracted from Illinois mines but also to assess the maximum ash separation efficiency and sulfur rejection achievable using the FGX Dry Separator for cleaning raw coals of varying cleaning characteristics. A Model FGX-1 Dry Separator with feed throughput capacity of 10 tph was extensively tested at the Illinois Coal Development Park using multiple coal samples having distinctly different cleaning characteristics. Statistically designed experimental programs were conducted to indentify critical process variables and to optimize FGX Dry Separator performance by systematic adjustments of critical process variable parameters. The coal-cleaning performance of the FGX Dry Separator was evaluated for the particle size range of 4.75–63.5 mm in most cases, although FGX Dry Separator feed consisted of nominal 7minus;63.5 mm run-of-mine coals. Deck vibration frequency, longitudinal deck angle, feeder frequency, and baffle plate height were identified as critical process variables for the FGX Dry Separator. The best cleaning performance obtained from the FGX Dry Separator was described by specific gravity of separation (SG50) and probable error (Ep) values of 1.98 and 0.17, respectively. For a relatively easy-to-clean coal (having a Cleaning Index of 0.72), only about 0.42% of the clean coal (i.e., 1.6 float fraction) present in the feed was lost to the tailings stream. For a relatively difficult-to-clean coal (having a Cleaning Index of 0.53), about 0.98% of the clean coal present in the feed was lost to the tailings stream. The positive impact of having fine materials in the FGX feed stream was also noted in this study. A modified log-logistic partition model was developed using experimental data reported in literature and validated using new experimental data generated in this study. The results showed that this model could be effectively used to predict the FGX Dry Separator coal-cleaning performance.

테니스 양손 백핸드 스트로크 방법에 따른 어깨와 힙의 회전운동 변화

The purpose of this study was to examine differences between players who bend the left elbow and those who stretch it during the forward swing from BST to BC in a 2-handed backhand stroke among outstanding high school tennis players, and to assess the detailed 3D rotational kinematic characteristics of the shoulder and the hip. Statistically significant differences were observed between groups in the longitudinal axis rotation angle of the shoulder and the angle between the shoulder and the arm at BST, and in the side to side movement of the shoulder, the up and down movement of the hip, the side tilt angular velocity of the shoulder, the side tilt angular velocity of the hip, and the front tilt angular velocity of the hip at BC. The difference in the longitudinal axis rotation angle of the shoulder between the 2 groups suggests a difference in the flexibility of the joint in the shoulder arm racquet system. The longitudinal axis rotation angular velocity of the shoulder reached its peak at 75 % of the duration of the analyzed segment and then decreased little by little until BC. This time is considered the stage for increasing the angular velocity of the upper arm, the forearm, the hand and then the racquet, which are more distal segments than the shoulder.

Elastic lateral-distortional buckling of I-beams and the Meck Plot

Meck Plot is an adapted version of the well-known Southwell method to the case of lateral-torsional buckling, which indeed reflects the physical inter-dependence of lateral flexure (lateral displacement) and torsion (rotation) in the structure. In the recent reported studies, it has been shown experimentally and theoretically that lateral displacement of an I-beam undergoing elastic lateral-distortional mode of buckling is interestingly directly coupled with other various deformation characteristics such as web transverse strain, web longitudinal strain, vertical deflection, and angles of twist of top and bottom flanges, and consequently good results have been obtained as a result of application of the Meck`s method on lateral displacement together with each of the aforementioned deformation variables. In this paper, it is demonstrated that even web transverse and longitudinal strains, vertical deflection, and angles of twist of top and bottom flanges of an I-beam undergoing elastic lateral-distortional buckling are two-by-two directly coupled and the application of the Meck Plot on each pair of these deformation variables may still yield reliable predictions for the critical buckling load.

Numerical Modeling of Abutment Scour with the Focus on the Incipient Motion on Sloping Beds

A three-dimensional computational fluid dynamics model is applied to predict local scour around an abutment in a rectangular laboratory flume. When modeling local scour, steep bed slopes up to the angle of repose occur. To predict the depth and the shape of the local scour correctly, the reduction of the critical shear stress due to the sloping bed must be taken into account. The focus of this study is to investigate different formulas for the threshold of noncohesive sediment motion on sloping beds. Some formulas only take the transversal angle (perpendicular to the flow direction) into account, but others also consider the longitudinal angle (streamwise direction). The numerical model solves the transient Reynolds-averaged Navier-Stokes equations in all three dimensions to compute the water flow. Sediment continuity in combination with an empirical formula is used to capture the bed load transport and the resulting bed changes. When the sloping bed exceeds the angle of repose, the bed slope is corrected with a sand-slide algorithm. The results from the numerical simulations are compared with data from physical experiments. The reduction of the bed shear stress on the sloping bed improves the results of the numerical simulation distinctly. The best results are obtained with the formulas that use both the transversal and the longitudinal angle for the reduction of the critical bed shear stress.

Cleaning of South African coal using a compound dry cleaning apparatus

The compound dry cleaning principle is briefly described. A beneficiation test on South African coal was conducted using a model compound dry cleaning apparatus. Excellent results were obtained and the optimum operating parameters were determined. They are: an amplitude of 3.0 mm, a motor frequency of 47.5 Hz, an air volume of 50%, a transverse angle of 7°, and a longitudinal angle of −2°. These conditions yield a clean coal containing 11% ash and a coal production of 75%. The organic efficiency, η, is 95.86%. These results show that the South African coal can be separated effectively by compound dry cleaning, which will popularize the compound dry cleaning method.

Vibration of thin, tensioned, helically wrapped plates

Free vibration analysis of a thin tensioned plate, wrapped around a cylindrical guide in a helical manner is presented. The system is a model of a thin, flexible web wrapped around a turn-bar. The equation of motion of the wrapped plate is derived by using the energy method and with the Kirchhoff–Love assumptions. The weak form of the equation of motion was obtained by the finite element method and the eigenvalue problem was solved numerically. The effects of parameters such as plate tension, guide radius, longitudinal and helical wrap angles, plate width, and the lengths of the non-wrapped segments were investigated. Eigenmodes with same mode numbers were observed in symmetric and anti-symmetric fashion about the center of the plate, for symmetrically wrapped plates. It was shown that the plate/shell boundary of the wrapped plate effectively acts like a support. For non-helically wrapped plates the free edges cause a frequency clustering of the lateral modes about the dominant longitudinal mode. The frequency clustering diminishes when helical wrap is introduced.

Approximations to the magic formula

Pacejka’s tire model is widely used and well-known by the automotive engineering community. The magic formula describes the brake force, side force and self-aligning torque in terms of the longitudinal slip and slip angle, plus several corrections. This paper uses approximation theory to obtain different types of approximations to the magic formula: rational functions (RA) resulting from the Remez algorithm, expansions in a series of Chebyshev polynomials (ACh), a series of Chebyshev rational polynomials (ARChPs), a series of rational orthogonal functions (ORF) and a series of ARChPs that result from grade-1 ORFs. The last expansion shows the fastest convergence and most effective computation. Jacobi rational polynomials can also be obtained to complement this expansion and facilitate fine-tuning in specific areas of the error curve. This work is complemented by obtaining the original rational approximations to the inverse tangent function, which take advantage of the curve symmetry to reduce the computation load and provide models that include the influence of the vertical load. The convergence properties of the development in series and the error values resulting from numeric examples for the three types of stress are shown. The proposed final ARChP expressions show very low error (1%) compared to the original magic formula. They can be computed 20 times faster; they can be evaluated, derived and integrated analytically easily; and their coefficients can be obtained from tests using common least-squares algorithms.

A Mechanical Analysis of Conduit Arteries Accounting for Longitudinal Residual Strains

Identification of an appropriate stress-free reference configuration is critically important in providing a reasonable prediction of the intramural stress distribution when performing biomechanical analyses on arteries. The stress-free state is commonly approximated as a radially cut ring that typically opens into a nearly circular sector, relieving much of the circumferential residual strains that exist in the traction-free configuration. An opening angle is often used to characterize this sector. In this study, we first present experimental results showing significant residual deformations in the longitudinal direction of two commonly studied arteries in the pig: the common carotid artery and the left anterior descending coronary artery. We concluded that a radially cut ring cannot completely describe the stress-free state of the arteries. Instead, we propose the use of a longitudinal opening angle, in conjunction with the traditional circumferential opening angle, to experimentally quantify the stress-free state of an artery. Secondly, we propose a new kinematic model to account for the addition of longitudinal residual strains through employing the longitudinal opening angle and performed a stress analysis. We found that with the inclusion of longitudinal residual strains in the stress analysis, the predicted circumferential stress gradient was decreased by 3-fold and the predicted longitudinal stress gradient was increased by 5.7-fold. Thus, inclusion of longitudinal residual strains has a significant effect on the predicted stress distribution in arteries.

Non-destructive evaluation of elastic properties, and ultrasonic attenuation of transverse wave of anisotropic and heterogeneous media

In industry to limit the number of experimental models in RD projects, to better understand and well interpret the complex ultrasonic phenomena observed during controls on site, simulations of ultrasonic controls are carried out. These simulations are more realistic than the description of structures to control is accurate, especially in terms of elastic constants, and intrinsic attenuation. This study is dedicated to the adaptation of existing measurement techniques to coarse grains materiel characterization such as steels cast by centrifugation and alloys made of Nickel. The first aim of this survey is to improve knowledge on the influence of the metallurgical characteristics of anisotropic and heterogeneous materials on the ultrasonic propagation and the second is to enhance computing codes performances to trace reliably the elastic constants and ultrasonic attenuation from experimental measurements. For this purpose, an experimental system for measuring on a single specimen, first the stiffness constants and second the attenuation in oblique incidence has been developed. The originality of this device is that it allows us to work beyond the longitudinal critical angle and therefore to measure the attenuation properties of transverse waves. To get elastic constants from the measured ultrasonic velocities, we will show the potential of global optimization algorithms such as genetic algorithms, less likely to converge on local minima of the function that we seek to minimize. Measurements of transverse waves attenuation by decomposition of the beam spectrum of plane waves are presented. © Owned by the authors, published by EDP Sciences, 2010 DOI:10.1051/epjconf/20100636002 EPJ Web of Conferences 6, 36002 (2010)

Exponential Stability and Global Attractors for a Thermoelastic Bresse System

We consider the stability properties for thermoelastic Bresse system which describes the motion of a linear planar shearable thermoelastic beam. The system consists of three wave equations and two heat equations coupled in certain pattern. The two wave equations about the longitudinal displacement and shear angle displacement are effectively damped by the dissipation from the two heat equations. We use multiplier techniques to prove the exponential stability result when the wave speed of the vertical displacement coincides with the wave speed of the longitudinal or of the shear angle displacement. Moreover, the existence of the global attractor is firstly achieved.

On the application of the extrapolation techniques in elastic buckling

Abstract The critical buckling load of a structure undergoing lateral buckling can be determined experimentally by using the extrapolation or plotting techniques, without having to subject the structure to loading in the vicinity of critical. To achieve this, it is only necessary to have data relating load to a deformation characteristic. A search of the literature reveals that only certain and just a few deformation characteristics such as lateral displacement and/or twist have mostly been used by researchers in this regard. In this paper, the feasibility of application of various deformation variables for experimental determination of the critical buckling load is investigated in case of I-beams with different initial geometrical imperfections undergoing the elastic lateral–distortional mode of buckling. It is demonstrated that lateral displacement of the I-beams is directly coupled with different deformation variables such as web transverse and longitudinal strains, vertical deflection, and angles of twist of top and bottom flanges. Based on these key findings, the Southwell, Massey, Modified, and Meck Plot methods are applied on these various deformation variables, and consequently satisfactory and reliable estimates are obtained for the critical buckling loads. Finally, it may be concluded that the application of the extrapolation techniques does not actually need to be limited to some certain deformation variables.

Cyclic Behavior of RC Columns Strengthened by FRP and Steel Devices

This paper presents several results of a wide experimental program undertaken to evaluate the seismic performance of RC columns, externally confined with fiber-reinforced polymers (FRPs). Specimens consisted of full scale square columns, 300 mm on each side, reinforced by using both smooth and deformed steel rebars and subjected to a constant axial load and monotonic or cyclic flexure; in particular, two levels of the axial load were considered. Tests were conducted, in displacement control, on both FRP confined and unconfined RC columns: the confinement system was obtained by partially wrapping two or four unidirectional carbon (CFRP) or glass (GFRP) fiber layers around the member; additionally, some tests were performed on members strengthened by using both the external CFRP wrapping and longitudinal steel angles. Experimental results allowed evaluating depending on the level of applied axial load and on the type of steel rebars adopted for reinforcing each column—the benefits introduced by the considered strengthening systems in terms of strength, ductility, and energy dissipation capacity.