Sum Of Displacements Research Articles

Preliminary outcomes of the surgical navigation system combined with intraoperative three-dimensional C-arm computed tomography for zygomatico-orbital fracture reconstruction

This study analyzed the outcomes of zygomatico-orbital fracture reconstruction using the real-time navigation system with intraoperative three-dimensional (3D) C-arm computed tomography (CT). Fifteen patients with zygomatico-orbital or isolated orbital/zygoma fractures were enrolled in this prospective cohort. For zygoma reduction, the displacement at five key sutures and the differences between preoperative and intraoperative CT images were compared. For orbital reconstruction, the bilateral orbital volume differences in the anterior, middle, and posterior angles over the medial transitional buttress were measured. Two patients required implant adjustment once after the intraoperative 3D C-arm assessment. On comparing the preoperative and postoperative findings for the zygoma, the average sum of displacement was 19.48 (range, 5.1–34.65) vs. 1.96 (0–3.95) mm (P < 0.001) and the deviation index was 13.56 (10–24.35) vs. 2.44 (0.6–4.85) (P < 0.001). For the orbit, the mean preoperative to postoperative bilateral orbital volume difference was 3.93 (0.35–10.95) vs. 1.05 (0.12–3.61) mm3 (P < 0.001). The mean difference in the bilateral angles at the transition buttress was significantly decreased postoperatively at the middle and posterior one-third. There was no significant difference in orbital volume, angle of the transition zone, and the sum of five zygoma distances between post operative results and preoperative virtual planning. The surgical navigation system with the intraoperative 3D C-arm can effectively improve the accuracy of zygomatico-orbital fracture reconstruction and decrease implant adjustment times.

RADIOLOGIC PREDICTIVE FACTORS FOR CUT OUT FAILURE OF PROXIMAL FEMORAL NAIL ANTI-ROTATION IN TREATMENT OF INTERTROCHANTERIC FRACTURES

Background: Proximal femoral fractures are the most common type of fracture among elderly patients. Moreover, half of the fractures are unstable types (AO31A2-A3). The aim of surgical treatments of these fractures is to achieve stable fracture fixation allowing early weight-bearing and returning to pre-fracture functional status. Even though the Tip Apex Distance (TAD) less than 25mm has been used to identify the appropriate position of the lag screw, little data has demonstrated the optimized TAD using a helical blade.Objectives: The study aimed to identify radiologic factors influencing fixation failure using a newly designed Proximal Femoral Nail Anti-rotation (PFNA)Methods: A total o 400 cases of low energy intertrochanteric fractures undergoing PFNA fixation were reviewed. Of these, 10 cases of fixation failure were further investigated determining the exact cause. Of 390 patients with successful outcomes treated using PFNA fixation, 20 cases were randomized as a control group. A comparative study was conducted between those with fixation failure group and control group.Results: The displacement in lateral view and sum of displacement between AP and lateral view of radiographs were noted to have significant differences between the group (p=0.002 and 0.015). No significant differences were found between the groups in terms of Neck Shaft Angle (NSA) and Tip Apex Distance (TAD) including migration of the PFNA blade in the Cleveland zone. Additionally, the cutoff point was determined as less than 0.91 using the sum of the distance of displacement of AP with specificity of 95% and sensitivity of 80%. Moreover, the lateral view of the radiographs was less than 1.42 with specificity of 80% and sensitivity of 80%.Conclusion: This study demonstrated that the displacement in lateral hip view and sum of the displacement in both AP and lateral hip view were alternative parameters measured to decrease failure rate in PFNA. These parameters may be useful as an alternative to decrease the mechanical failure of PFNA fixation.

Deformation and failure mechanism of slope in three dimensions

Understanding three-dimensional (3D) slope deformation and failure mechanism and corresponding stability analyses are crucially important issues in geotechnical engineering. In this paper, the mechanisms of progressive failure with thrust-type and pull-type landslides are described in detail. It is considered that the post-failure stress state and the pre-peak stress state may occur at different regions of a landslide body with deformation development, and a critical stress state element (or the soil slice block) exists between the post-failure stress state and the pre-peak stress state regions. In this regard, two sorts of failure modes are suggested for the thrust-type and three sorts for pull-type landslides, based on the characteristics of shear stress and strain (or tensile stress and strain). Accordingly, a new joint constitutive model (JCM) is proposed based on the current stability analytical theories, and it can be used to describe the mechanical behaviors of geo-materials with softening properties. Five methods, i.e. CSRM (comprehensive sliding resistance method), MTM (main thrust method), CDM (comprehensive displacement method), SDM (surplus displacement method), and MPM (main pull method), for slope stability calculation are proposed. The S-shaped curve of monitored displacement vs. time is presented for different points on the sliding surface during progressive failure process of landslide, and the relationship between the displacement of different points on the sliding surface and height of landslide body is regarded as the parabolic curve. The comparisons between the predicted and observed load–displacement and displacement–time relations of the points on the sliding surface are conducted. The classification of stable/unstable displacement–time curves is proposed. The definition of the main sliding direction of a landslide is also suggested in such a way that the failure body of landslide (simplified as “collapse body”) is only involved in the main sliding direction, and the strike and the dip are the same as the collapse body. The rake angle is taken as the direction of the sum of sliding forces or the sum of displacements in collapse body, in which the main slip direction is dependent on progressive deformation. The reason of non-convergence with finite element method (FEM) in calculating the stability of slope is also numerically analyzed, in which a new method considering the slip surface associated with the boundary condition is proposed. It is known that the boundary condition of sliding surface can be described by perfect elasto-plastic model (PEPM) and JCM, and that the stress and strain of a landslide can be described properly with the JCM.

Displacements, mean-squared displacements, and codisplacements for the calculation of nonequilibrium properties.

We study two situations in which nonequilibrium phenomena can be efficiently calculated using displacements, mean-squared displacements, or codisplacements instead of accumulating velocities or currents. The flow velocity profile for a fluid confined within a pore can be expressed as a sum of displacements within slabs from a molecular dynamics trajectory. In this form, an accurate flow profile is obtained from very sparse sampling of the trajectory. We also recast the linear response theory expression for the flow velocity profile in terms of mean codisplacements and demonstrate that this provides an efficient route for estimating the Green-Kubo expression for the velocity profile. Finally, we calculate the ionic contribution to the frequency-dependent electric susceptibility using dipolar displacements, instead of the conventional current-current correlation function. We expect these methods to be useful for generating transport properties from stored trajectories in very large systems or systems where relaxation times are long.

The age and rate of displacement along the Main Central Thrust in the western Bhutan Himalaya

In western Bhutan, the Main Central Thrust (MCT) is broadly folded, creating multiple exposures of the fault surface over a ~70km across-strike distance. This unusual map pattern presents a unique opportunity to map the MCT and document both the magnitude and age of displacement. In situ Th-Pb (SIMS and LA-ICP-MS) geochronology of metamorphic monazite from the immediate hanging wall of the MCT indicates that prograde monazite growth in Greater Himalayan (GH) rocks continued until 20.8±1.1Ma, whereas crystallization of in situ melts, characterized by high Y monazite overgrowths, occurred during cooling from ca. 15–10Ma. Prograde monazite growth at 15Ma in Lesser Himalaya (LH) rocks in the immediate footwall requires that LH footwall strata began to be buried at this time, and the MCT had reached its southernmost, exposed extent. By combining prograde monazite ages in the immediate hanging wall and footwall, the duration of MCT displacement is bracketed between 20.8±1.1 and 15.0±2.4Ma. Immediately north of our study area, a published estimate of shearing along the outer-South Tibetan detachment (STD) argues for displacement between 20 and 15Ma, coeval with the age range for MCT displacement that we document in this study. However retrograde monazite grains as young as 10Ma suggest that GH rocks were cooling until ~10Ma, 5Myr later than motion on the outer-STD immediately to the north. This cooling was either the result of continued displacement on the MCT, or growth of a duplex that passively folded the MCT. Using a sequential reconstruction, we estimate a total displacement of ~230km, which is the sum of displacements on the MCT and the structurally-lower Paro Thrust, over a duration of 5.8±2.6Myr. This indicates a horizontal shortening rate of 4.0+3.2/−1.3cm/yr, which exceeds present rates estimated from geodetic measurements across the Himalaya, and MCT displacement rates (c. 2cm/yr) inferred from petrologic and thermal models in central Nepal but is indistinguishable from plate convergence rates calculated for eastern Bhutan between 23 and 20Ma (3.3±0.7cm/yr). Our study highlights that displacement on the MCT alone achieved plate velocity rates in western Bhutan, and that the age and rate of MCT displacement varied significantly across the Himalaya.

Air Compressor Plate Drum’s Reliability Analysis

Based on the finite element theory, air compressor plate drum is analyzed in the rotating and loading circumstances. The maximum displacement sum was regarded as a random output variable, when plate angular velocity the elastic modulus, Poisson’s ratio density and equivalent centrifugal force were randomized, and were considered as a random input variable. Supposed all input variables are normal distribution. After Monto Carlo sampling is implemented one thousand times, the reliability and sensitivity of air compressor plate drum can be obtained.

Paleoseismic activity on Wujiahe segment of Serteng piedmont fault, Inner Mongolia

Geomorphic study on Wujiahe segment of Serteng piedmont fault, Inner Mongolia is made. Through analysis of the available data in combination with the results of predecessors’ studies it can be obtained that average vertical displacement rate is 0.48–0.75 mm/a along the Wujiahe segment since the late Pleistocene (14.450–22.340 ka BP) and 0.56–0.88 mm/a since the early-middle Holocene (5.570–8.830 ka BP). Analyzing paleoseismic phenomena revealed in the excavated 5 trenches in combination with the results of predecessors’ studies of paleoearthquakes on the fault, we determine five paleoseismic events on the Wujiahe segment of Serteng piedmont fault since 27.0 ka BP and the recurrence interval to be about 4.300–4.400 ka. A cluster of paleoearthquakes occurred probably during 8.000–9.000 ka BP and two paleoseismic events in 10.000–20.000 ka BP may be missed. A comparison between height of fault scarps and sum of displacement caused by paleoseismic events revealed in trenches, and recurrence interval of paleoseismic events obtained from average displacement rate along the fault and the dislocation by one event suggest that three paleoseismic events are absent in Alagaitu trench. Two paleoseismic events may be absent on the whole active fault segment.

Automated regional myocardial displacement for facilitating the interpretation of dobutamine echocardiography

Quantification of stress echocardiography may overcome the training requirements and subjective nature of visual wall motion score (WMS) assessment , but quantitative approaches may be difficult to apply and require significant time for image processing. The integral of long-axis myocardial velocity is displacement, which may be represented as a color map over the left ventricular myocardium. This study was designed to explore the feasibility and accuracy of measuring long-axis myocardial displacement, derived from tissue Doppler, for the detection of coronary artery disease (CAD) during dobutamine stress echocardiography (DBE). One hundred thirty patients underwent standard DBE, including 30 patients at low risk of CAD, 30 patients with normal coronary angiography (both groups studied to define normal ranges of displacement), and 70 patients who underwent coronary angiography in whom the accuracy of normal ranges was tested. Regional myocardial displacement was obtained by analysis of color tissue Doppler apical images acquired at peak stress. Displacement was compared with WMS, and with the presence of CAD by angiography. The analysis time was 3.2 ± 1.5 minutes per patient. Segmental displacement was correlated with wall motion (normal 7.4 ± 3.2 mm, ischemia 5.8 ± 4.2 mm, viability 4.6 ± 3.0 mm, scar 4.5 ± 3.5 mm, p <0.001). Reversal of normal base-apex displacement was an insensitive (19%) but specific (90%) marker of CAD. The sum of displacements within each vascular territory had a sensitivity and specificity of 89% and 79%, respectively, for prediction of significant CAD, compared with 86% and 78%, respectively, for WMS (p = NS). The displacements in the basal segments had a sensitivity and specificity of 83% and 78%, respectively (p = NS). Regional myocardial displacement during DBE is feasible and offers a fast and accurate method for the diagnosis of CAD.

Nonlinear finite element analysis of thick composite plates using cubic spline functions

A nonlinear, thick, composite plate element is developed in which the usual Kirchhoff hypothesis of plane sections remaining plane and undeformed after loading is abandoned. The displacement field is characterized by the sum of displacements with respect to a reference surface and displacements through the thickness. The through-the-thickness deformations are modeled by imposing a cubic spline function and allowing the rotations at interlaminar boundaries to be degrees of freedom in the element. The theory is developed by considering the Lagrangian strains in conjunction with the second Piola-Kirchhoff stress. This formulation leads to a quasi-threedimensional element that encompasses large displacements with moderately large rotations but is restricted to small strains. Comparisons of linear and nonlinear thick orthotropic plate solutions with those of previously published analytical and numerical results show the validity of the method.

Development of faults as zones of deformation bands and as slip surfaces in sandstone

Three forms of fault are recognized in Entrada and Navajo Sandstones in the San Rafael Desert, southeastern Utah; deformation bands, zones of deformation bands, and slip surfaces. Small faults occur as deformation bands, about one millimeter thick, in which pores collapse and sand grains fracture, and along which there are shear displacements on the order of a few millimeters or centimeters. Two or more deformation bands adjacent to each other, which share the same average strike and dip, form a zone of deformation bands. A zone becomes thicker by addition of new bands, side by side. Displacement across a zone is the sum of displacements on each individual band. The thickest zones are about 0.5 m and total displacement across a thick zone rarely exceeds 30 cm. Finally, slip surfaces, which are through-going surfaces of discontinuity in displacement, form at either edge of zones of highly concentrated deformation bands. In contrast with individual deformation bands and zones of deformation bands, slip surfaces accommodate large displacements, on the order of several meters in the San Rafael Desert.