Value Of Relative Displacement Research Articles

Biomechanical behaviour of a novel bone cement screw in the minimally invasive treatment of Kummell's disease: a finite element study

ObjectiveTo investigate and evaluate the biomechanical behaviour of a novel bone cement screw in the minimally invasive treatment of Kummell's disease (KD) by finite element (FE) analysis.MethodsA validated finite element model of healthy adult thoracolumbar vertebrae T12-L2 was given the osteoporotic material properties and the part of the middle bone tissue of the L1 vertebral body was removed to make it wedge-shaped. Based on these, FE model of KD was established. The FE model of KD was repaired and treated with three options: pure percutaneous vertebroplasty (Model A), novel unilateral cement screw placement (Model B), novel bilateral cement screw placement (Model C). Range of motion (ROM), maximum Von-Mises stress of T12 inferior endplate and bone cement, relative displacement of bone cement, and stress distribution of bone cement screws of three postoperative models and intact model in flexion and extension, as well as lateral bending and rotation were analyzed and compared.ResultsThe relative displacements of bone cement of Model B and C were similar in all actions studied, and both were smaller than that of Model A. The minimum value of relative displacement of bone cement is 0.0733 mm in the right axial rotation of Model B. The maximum Von-Mises stress in T12 lower endplate and bone cement was in Model C. The maximum Von-Mises stress of bone cement screws in Model C was less than that in Model B, and it was the most substantial in right axial rotation, which is 34%. There was no substantial difference in ROM of the three models.ConclusionThe novel bone cement screw can effectively reduce the relative displacement of bone cement by improving the stability of local cement. Among them, novel unilateral cement screw placement can obtain better fixation effect, and the impact on the biomechanical environment of vertebral body is less than that of novel bilateral cement screw placement, which provides a reference for minimally invasive treatment of KD in clinical practice.

Biomechanical evaluation of novel intra- and extramedullary assembly fixation for proximal humerus fractures in the elderly.

Purpose: A novel intra- and extramedullary assembly fixation method was introduced, which achieved good clinical results in complex proximal humeral fractures; however, evidence of its comparability with traditional fixation is lacking. This biomechanical study aimed to compare it with traditional fixation devices in osteoporotic proximal humeral fractures. Methods: Three-part proximal humeral fractures with osteopenia were created on 12 pairs of fresh frozen humerus specimens and allocated to three groups: 1) lateral locking plate, 2) intramedullary nail, and 3) intra- and extramedullary assembly fixation. The specimens were loaded to simulate the force at 25° abduction. Thereafter, an axial stiffness test and a compound cyclic load to failure test were applied. Structural stiffness, number of cycles loaded to failure, and relative displacement values at predetermined measurement points were recorded using a testing machine and a synchronized 3D video tracking system. Results: In terms of initial stiffness and the number of cycles loaded to failure, the intra- and extramedullary assembly fixation group showed notable improvements compared to the other groups (p <0.017). The mean relative displacement value of measurement points in the intra- and extramedullary assembly fixation group was smaller than that in the other two groups. However, there was no significant difference until 10,000 cycles. The mean relative displacement of the intramedullary nail group (3.136mm) exceeded 3mm at 7,500 cycles of loading. Conclusion: In this test model, axial fixation can provide better mechanical stability than non-axial fixation. The intra- and extramedullary assembly fixation is better able to prevent the varus collapse for elderly proximal humeral fractures with posteromedial comminution.

DEVELOPMENT OF A PRE-CLINICAL EXPERIMENTAL MODEL TO MEASURE MEDIAL MENISCUS POSITION DURING A SIMULATED GAIT CYCLE OF THE KNEE JOINT

The aim of this work was to develop a novel, accessible and low-cost method, which is sufficient to measure changes in meniscal position in a whole-knee joint model performing dynamic motion in a knee simulator.An optical tracking method using motion markers, MATLAB (MATLAB, The MathWorks Inc.) and a miniature camera system (Raspberry Pi, UK) was developed. Method feasibility was assessed on porcine whole joint knee samples (n = 4) dissected and cemented to be used in the simulator (1). Markers were placed on three regions (medial, posterior, anterior) of the medial meniscus with corresponding reference markers on the tibial plateau, so the relative meniscal position could be calculated. The Leeds high kinematics gait profile scaled to the parameters of a pig (1, 2) was driven in displacement control at 0.5 Hz. Videos were recorded at cycle-3 and cycle-50. Conditions tested were the capsule retained (intact), capsule removed and a medial posterior root tear. Mean relative displacement values were taken at time-points relating to the peaks of the axial force and flexion-extension gait inputs, as well as the range between the maximum and minimum values. A one-way ANOVA followed by Tukey post hoc analysis were used to assess differences (p = 0.05).The method was able to measure relative meniscal displacement for all three meniscal regions. The medial region showed the greatest difference between the conditions. A significant increase (p &lt; 0.05) for the root tear condition was found at 0.28s and 0.90s (axial load peaks) during cycle-3. Mean relative displacement for the root tear condition decreased by 0.29 mm between cycle-3 and cycle-50 at the 0.28s time-point. No statistically significant differences were found when ranges were compared at cycle-3 and cycle-50.The method was sensitive to measure a substantial difference in medial-lateral relative displacement between an intact and a torn state. Meniscus extrusion was detected for the root tear condition throughout test duration. Further work will progress onto human specimens and apply an intervention condition.

How to improve the biomechanical stability of endosteal augmentation for proximal humerus fracture with osteopenia? A cadaveric study

BackgroundEndosteal augmentation enhances the stability of osteoporotic proximal humeral fracture fixation, but the optimal configuration is unknown. The purpose of this study was to compare the biomechanical properties of different lengths of fibula with or without calcar screw in osteoporotic proximal humeral fracture. MethodsThree-part proximal humeral fractures with osteopenia were created on 20 pairs of fresh-frozen humeri specimens and allocated to four groups: (1) locking plate with a 6-cm fibular strut allograft, (2) locking plate with a 6-cm fibular strut allograft and additional calcar screws, (3) locking plate with a 12-cm fibular strut allograft，and (4) locking plate with a 12-cm fibular strut allograft and additional calcar screws. Specimens were loaded to simulate the force at 25° abduction. Thereafter, an axial stiffness test and a compound cyclic load to failure test were applied. Structural stiffness, number of cycles loaded to failure and relative displacement values for 5000 cycles at predetermined measurement points were recorded using a testing machine and a synchronized 3D video tracking system. FindingsIn terms of initial stiffness, number of cycles loaded to failure, and relative displacement values, the groups with 12-cm fibular strut showed obvious improvement compared to the groups with 6-cm fibular strut irrespective of the influence of calcar screw implementation. Further, the groups implemented with calcar screws also showed promising biomechanical stability irrespective of fibular length. InterpretationLateral locking plate with longer endosteal fibular augmentation and calcar screw can significantly improve biomechanical stability for elderly proximal humeral fractures with posteromedial comminution.

Study of interference fit between steel and brass parts

Interference fits are generally used in mechanical systems because they have low-cost production and their assembly parts are much smaller than other mechanical joints. Also, their geometric shapes and material properties allow technicians to actively determine how strong the fits are. In this study, let’s present research on interference fits between steel and brass assembly parts. The experimental processes were accomplished with five pairs of specimens to evaluate the behaviours of surface asperities under a high loading condition. Specifically, the specimen pair includes a C45 steel shaft and a C2680 brass hub, which have different surface roughness values (Ra). Let’s apply high-precision methods in measuring all dimensional parameters and employed axial load tests for distinctively inspecting the steel-brass interference fit performance. In every experiment, the measured responses are:&#x0D; 1) the surface roughness values (Ra) before and after loading cycles;&#x0D; 2) the axial load (Fa);&#x0D; 3) the relative displacement value or the real-time interface length in loading stages (l).&#x0D; The aim of this study is to propose a new relative interference value specifically between steel and brass assembly parts, which can help determine the interference loss value more accurately. It was not concluded that with the relative interference of 2.25 ‰ the load capability of steel-brass interference fits is extended. Besides, let’s narrow down the predictive loss coefficient (a) for steel-brass interference assemblies ranging from 1.1 to 2.1, which varies from widely used standards considering a=3. This result helps minimize inaccuracies in interference fit designs, calculations, and work capabilities.

Mechanical and Wear Behavior of Steel Wires in Typical Contact Area Under Tension-tension Fatigue

In this study, the issues of the complex mechanical behavior inside steel wire rope and wear evolution of internal wire at typical contact areas where the fracture of the wire is more likely to occur is particularly considered. First, the fretting parameters of steel wires at typical contact areas were calculated. Then the wear evolution process under tensile loads with different stress ratios was simulated by using the finite element method (FEM) based on the calculated parameters. Finally, the micro-morphology and element concentration and distribution of wear scars at typical contact areas were observed. The results demonstrate that: (1) The relative displacement value and normal contact stress between the outer layer steel wires of core strand and outer strands are maximum, which cause the most severe wear in this area. As the stress ratio decreases from 0.5 to 0.25, the fretting parameters of steel wires increase. (2) The wear evolution process is divided into running-in stage and stable wear stage, which are characterized by the rapid decline and stabilization of wear rate, respectively. (3) Compared with other contact areas, the concentration of iron, carbon and chlorine in the contact area between strands is obviously higher. Meanwhile, there exist strong plastic deformation, severe delamination and primary and secondary cracks in this region, resulting in stress concentration and thus the fatigue life decrease of steel wire.

"Fishing net" suture augmenting tension-band wiring fixation in the treatment of inferior pole fracture of the patella.

Inferior pole fracture of the patella (IPFP) is difficult to repair and stabilize clinically. Although various fixation techniques have been developed, fixation strength and mobility remain daunting challenges to orthopedic surgeons. The goal of this research is to evaluate the biomechanical strength and clinical outcomes of a novel "fishing net" suture fixation procedure. Four finite element models, modified tension-band wiring fixation, anchor suture fixation, basket plate fixation and "fishing net" suture fixation were built to compare the fixing efficacy of "fishing net" suture fixation with three other fixation methods during IPFP fixation. From January 2018 to February 2019, 17 patients who suffered IPFP and treated by "fishing net" suture (FNS) fixation were compared with 20 patients treated by tension-band wiring (TBW) fixation in database and the two groups were evaluated postoperatively using the modified Cincinnati knee rating system. Biomechanical evaluation showed that the relative displacement values of proximal patella measured by three pairs of points on both sides of the fracture line were the lowest using the "fishing net" suture fixation, while fixation using tension-band wiring and basket plate showed similar levels of stability that were less desirable than the "fishing net" method. As to clinical outcomes, there were 17 (100%) patients exhibited excellent or good results with no internal fixation failures in the FNS group compared to three internal fixation failures in the TBW group. The biomechanical and clinical results suggest that the "fishing net" suture fixation is a viable candidate for fixation of IPFP.

Are the unreamed nails indicated in diaphyseal fractures of the lower extremity? A biomechanical study

IntroductionIntramedullary nailing is generally accepted as the first choice for the treatment of diaphyseal fractures of femur and tibia, with a gradual incease in the use of unreamed nails. Different studies during last years show controversial outcomes. Some authors strongly favor unreamed nailing, but most of the authors conclude that reamed nailing have proved to be more successful. Material and methodsThis study simulates unreamed intramedullary nailing of four femoral and three tibial fracture types by means of Finite Element (FE) models, at early postoperative stages with a fraction of physiological loads, in order to determine whether sufficient stability is achieved, and if the extent of movements and strains at the fracture site may preclude proper consolidation. ResultsThe behavior observed in the different fracture models is very diverse. In the new biomechanical situation, loads are only transmitted through the intramedullary nail. Mean relative displacement values of fractures in the femoral bone range from 0.30 mm to 0.82 mm, depending on the fracture type. Mean relative displacement values of the tibial fractures lie between 0.18 and 0.62 mm, depending on the type of fracture. Concerning mean strains, for femoral fractures the maximum strains ranged between 12.7% and 42.3%. For tibial fractures the maximum strains ranged between 10.9% and 40.8%. ConclusionsThe results showed that unreamed nailing provides a very limited mechanical stability, taking into account that analyzed fracture patterns correspond to simple fracture without comminution. Therefore, unreamed nailing is not a correct indication in femoral fractures and should be an exceptional indication in open tibial fractures produced by high-energy mechanism.

Numerical Analysis of Twin Tunnels Lining under Different Seismic Conditions

The last seismic events showed that tunnel lining may suffer extensive damage. Employing numerical modeling has a great importance in predicting the seismic performance of tunnels. This paper tests the tunnel lining of the Zaouit Ait Mellal (ZAM) twin tunnels located between the cities of Marrakesh and Agadir in Morocco. Dynamic analysis was adopted by FLAC 2D software using the finite-difference elements. Four soil cross-sections were chosen, with different support devices installed along the twin tunnels, such as rock bolts and steel ribs. The seismic signals introduced as input were obtained from three different earthquakes: Al Hoceima 2004 in Morocco, EL Centro 1940 in the USA, and Kobe 1995 in Japan. The numerical results show that the deformation of the tunnel lining is more noteworthy in the sections using steel ribs compared to those using rock bolts, which is observed by the large values of relative displacement, reaching 1020 (mm) and 2.29 × 105 (N.m/m) of maximum bending moment. The analysis indicates that these sections present higher vulnerability during an earthquake, which should be considered when looking at the overall safety of the tunnel.

The importance of modeling the human cerebral vasculature in blunt trauma

BackgroundMultiple studies describing human head finite element (FE) models have established the importance of including the major cerebral vasculature to improve the accuracy of the model predictions. However, a more detailed network of cerebral vasculature, including the major veins and arteries as well as their branch vessels, can further enhance the model-predicted biomechanical responses and help identify correlates to observed blunt-induced brain injury.MethodsWe used an anatomically accurate three-dimensional geometry of a 50th percentile U.S. male head that included the skin, eyes, sinuses, spine, skull, brain, meninges, and a detailed network of cerebral vasculature to develop a high-fidelity model. We performed blunt trauma simulations and determined the intracranial pressure (ICP), the relative displacement (RD), the von Mises stress, and the maximum principal strain. We validated our detailed-vasculature model by comparing the model-predicted ICP and RD values with experimental measurements. To quantify the influence of including a more comprehensive network of brain vessels, we compared the biomechanical responses of our detailed-vasculature model with those of a reduced-vasculature model and a no-vasculature model.ResultsFor an inclined frontal impact, the predicted ICP matched well with the experimental results in the fossa, frontal, parietal, and occipital lobes, with peak-pressure differences ranging from 2.4% to 9.4%. For a normal frontal impact, the predicted ICP matched the experimental results in the frontal lobe and lateral ventricle, with peak-pressure discrepancies equivalent to 1.9% and 22.3%, respectively. For an offset parietal impact, the model-predicted RD matched well with the experimental measurements, with peak RD differences of 27% and 24% in the right and left cerebral hemispheres, respectively. Incorporating the detailed cerebral vasculature did not influence the ICP but redistributed the brain-tissue stresses and strains by as much as 30%. In addition, our detailed-vasculature model predicted strain reductions by as much as 28% when compared to current reduced-vasculature FE models that only include the major cerebral vessels.ConclusionsOur study highlights the importance of including a detailed representation of the cerebral vasculature in FE models to more accurately estimate the biomechanical responses of the human brain to blunt impact.

Influence of Superior Vibration Modes on the Seismic Response of Reinforced Concrete Structures with Eigen-Periods Near Code Control Periods

Abstract The current paper studies the effect of superior eigen-modes on the seismic response for a series of reinforced concrete structures having eigen-periods near code control periods. Although the structural design is based on Romanian seismic design codes (“P100-1/2013 - Seismic design code - Part 1 - Design provisions for buildings” and “SR-EN 1998/2004 - Design of structures for earthquake resistance”), it carries some importance for other countries with similar seismic design spectra. A total of twenty-four models for structures were considered by varying their location (through control period values), three-dimensional regularity, overall dimensions and height regime. Results were compared and conclusions were drawn based on percentage values of relative displacements (storey drifts) and base shear forces.

BaZrO3 stability under pressure: The role of nonlocal exchange and correlation

The ground-stale structure of BaZrO3 is experimentally known to be cubic down to absolute zero. However, there exist several measured properties and experimental characterizations that earlier computational works have failed to accurately describe and explain within this cubic symmetry. Among these properties and observations are the dielectric constant and the parallel mean-squared relative displacement value that tracks the fluctuations in distance for Ba-O atom pairs. Previous density-functional theory (DFT) studies have resolved the issue by assuming that BaZrO(3 )undergoes a phase transition from cubic to tetragonal I4/mcm symmetry, possibly while forming a glasslike state that reflects cubic symmetry on average. In this paper, we show that the set of experimental results can indeed be satisfactorily explained by DFT entirely within the cubic symmetry. We find that past theory limitations arose from the choice of exchange-correlation-functional approximations and that the inclusion of Fock exchange in hybrids significantly improves the DFT performance. We also find that the inclusion of nonlocal correlation effects is beneficial. We conclude by making a prediction for the phase-transition pressure for the transition from cubic to tetragonal symmetry at zero kelvin.

Optimization Damping of Viscous Dampers to Prevent Collisions Between Adjacent Structures with Unequal Heights as a Case Study

Currently, construction is very dense especially in city centers, and adjacent structures are generally preferred in areas where available land is scarce. These structures often have different heights and are generally constructed without a structural connection to each other. Since adjacent structures may have different dynamic characteristics, collisions may occur when the structures contact each other under earthquake effects. Therefore, this study investigated the optimum values of viscous dampers placed between adjacent structures of unequal height to prevent collisions under different earthquake effects. In the optimization problem determined, the objective function was selected to minimize the total damping coefficient of viscous dampers added to the stories. A new algorithm utilizing numerical optimization methods to find the values of dampers between the structures was introduced to avoid collisions between adjacent structures of different heights. Structural models were used to examine the effects of variations in the height ratios of the structures, the value of damping from the viscous dampers on each floor, the vibration mode of the structures and the values of relative displacement. The proposed method showed that when viscous dampers were optimally placed between adjacent buildings of different heights, the relative displacements under earthquake impacts could be reduced below a target value, thereby avoiding the risk of collisions.

Effect of Electrical Damping Ratio on Maximum Average Power of an Electromagnetic Vibration Harvester at Resonance and off-Resonance Conditions

Energy harvesting has opened up new ways to power low energy electronics without any need for batteries. The most advanced types of harvesters are piezoelectric, electrostatic and electromagnetic which use kinetic energy in form of vibrations. Electromagnetic harvesters (EHs) are efficient, less costly and offer huge design flexibility. As such, in this paper some analytical and experimental studies on maximum average harvestable power (Pave) from typical design of EH using the popular coupling architecture (a cylindrical magnet oscillating in a copper coil) have been carried out. The effect of frequency of excitation and electrical (ζe ) and mechanical damping ratios (ζm) on Pave obtained from an EH has been investigated. For this purpose, an EH using NdFeB (neodymium magnet) magnet oscillating in a copper coil has been designed and developed. An experimental test set up has developed which comprises of (i) a cam-follower type drive mechanism to simulate a vibration source with variable amplitude and frequency of base excitation, (ii) a spring-mass system with an EH system in parallel with the spring to provide the relative motion between the magnet and the copper coil, (iii) the attendant instrumentation comprising of ultrasonic sensor to sense the displacements of base and mass, motor drive speed measurement and an open source platform (ARDUINO) with programmable circuit board and software and data acquisition system. Using the developed experimental set up, (i)frequency response curve for vibrating system with EH has been obtained from which equivalent electrical damping ζe has been determined using half power point method, and (ii)the values of relative displacements of magnet and coil, at various excitation frequencies have been recorded. Using the analytical expression for the Pave of SDOF EH has been determined both at resonance and off resonance conditions, for three different values of ζe namely ζe = ζm, ζe = 5ζm, and ζe = 10ζm. It is observed that the maximum Pave is obtained for condition ζe = ζm. As the value of ζe increases, the Pave increases, at resonant frequency and considerable power is made available at off-resonance frequencies. It is concluded that ζe should be increased to enhance the maximum average harvestable power from EH and vibrating system should be so designed to have ζm, as small as possible.

Adaptive Backstepping Control of Uncertain Gear Transmission Servosystems With Asymmetric Dead-Zone Nonlinearity

In this paper, an adaptive backstepping control scheme is presented to solve the position control problem for a gear transmission servosystem with unknown asymmetric sandwiched dead-zone nonlinearity. All the parameters involved in both the system and dead-zone models are allowed to be totally unknown. In contrast to the previous results where the effects of symmetric dead zone can be treated as additive disturbances in a transformed system, most of the unknown parameters of the transformed system are now time varying and dependent on the real-time value of relative displacement between the driving and driven gears. To deal with the above issue, new compensating terms in the quadratic form are introduced in the design of the virtual control signal for each recursive step. With the adaptive laws modified correspondingly, we can still show that all the closed-loop signals are ensured to be bounded and the output regulation error will converge to a compact set. Simulation results are provided to show the effectiveness of the proposed adaptive control scheme.

Visual Identity-Based Earthquake Ground Displacement Testing Method

Ground deformation observation is wildly concerned in the field of earthquake engineering. This paper proposes a high-precision displacement measurement technology based on both computer vision and numerical simulation. During the earthquake, the vision-based testing system collects visual data of the target installed on the location to be observed. The visual data streams can be quantified to the dynamic relative displacement value automatically, by employing mathematical vision algorithms and then by taking the relative displacement as an intermediate quantity, which is brought into the numerical model for iteration. When the test result is close to the simulated one, the absolute ground displacement data could be obtained approximately. A series of experiments have been carried out to suggest that the proposed method presents an innovative and low-cost solution to ground measurement in high accuracy. The method not only realizes the real-time ground deformation observation; moreover, it also provides a wider range of reliable data support to understand deformation mechanism, investigate seismic source information, and recognize the ground motion characteristics.

A Linearization Method of Piecewise Linear Systems Based on Frequency Domain Characteristics With Application to Semi-Active Control of Vibration

In this paper, a new approach is presented for linearization of piecewise linear systems with variable dry friction, proportional with absolute value of relative displacement. The transmissibility factors of considered systems, defined in terms of root-mean-square (RMS) values, are obtained by numerical time integration of motion equations for a set of harmonic inputs with constant amplitude and different frequencies. A first-order linear differential system is attached to the considered piecewise linear system such as the first component of solution vector of attached system to have the same transmissibility factor as the chosen output of nonlinear system. This method is applied for the semi-active control of vibration with balance logic strategy. Applications to base isolation of rotating machines and vehicle suspensions illustrate the effectiveness of the proposed linearization method.

First post-IR IRSL dating results of Quaternary deposits from Bilogora (NE Croatia): Implications for the Pleistocene relative uplift and incision rates in the area

Bilogora is a hilly terrain in the SW Pannonian Basin, along the SW margin of the Drava Depression in Croatia. It is genetically linked to the tectonic evolution of the Drava Depression during the Neogene and Quaternary and the associated palaeo-Drava River System. The Quaternary sedimentary succession is represented by four aggradational Drava River terraces composed of thick series of gravel intercalated by sand, silt and clays. Stratigraphically, the oldest terraces exposed in the investigated area are unconformably overlain by Pleistocene loess and loess-like deposits.In order to establish a chronological framework of the Quaternary deposits, luminescence dating was applied on loess and loess-like sediments as well as sand intercalated within the terrace gravel deposits. The dating was performed on feldspar coarse-grains from the sand and on the polymineral fine-grained material from loess, using the pIRIR290 protocol. The luminescence signals of the sand are in saturation and therefore very likely point to a Middle Pleistocene age of the river terrace, whereas the covering loess can be correlated to the Last Glacial. The obtained pIRIR290 dating results indicate the timing of the abandonment of the investigated river terrace, whereas the relation of the relative displacement values of the investigated river terrace to the obtained age could imply the relative uplift rates of the area.According to the relative displacement values, sampling heights above the present Drava River level and the obtained pIRIR290 ages of >359 ka and >450 ka, the calculated relative uplift rates were 0.56 mm/a for Mučna Reka and 0.43 mm/a for Cabuna. For the same sampling locations, the calculated relative incision rates of the Drava River were of 0.09 and 0.22 mm/a. The results of relative uplift rates show a higher value concentrated in the NW part of Bilogora, being associated with multiple mapped neotectonic active faults in the Drava Depression Boundary fault zone and Kalnik Mt. Fault Zone. On the other hand, the low incision rates that probably accommodate a portion of the tectonic uplift of Bilogora, point to lower erosion of the paleo-Drava River. Moreover, the Drava River is dominated by the aggradation of alluvial deposits during the Quaternary. We believe that the computed incision rates represent only one relative portion of the Drava process, whereas the tectonics, sediment transportation and accumulation were dominant processes in the study area and can be correlated with the climate oscillations during the Pleistocene and Holocene.

SU-G-JeP1-14: Respiratory Motion Tracking Using Kinect V2

Purpose: Investigate capability and accuracy of Kinect v2 camera for tracking respiratory motion to use as a tool during 4DCT or in combination with motion management during radiotherapy treatments. Methods: Utilizing the depth sensor on the Kinect as well as code written in C#, the respiratory motion of a patient was tracked by recording the depth (distance) values obtained at several points on the patient. Respiratory traces were also obtained using Varian's RPM system, which traces the movement of a propriety marker placed on the patient's abdomen, as well as an Anzai belt, which utilizes a pressure sensor to track respiratory motion. With the Kinect mounted 60 cm above the patient and pointing straight down, 11 breathing cycles were recorded with each system simultaneously. Relative displacement values during this time period were saved to file. While RPM and the Kinect give displacement values in distance units, the Anzai system has arbitrary units. As such, displacement for all three are displayed relative to the maximum value for the time interval from that system. Additional analysis was performed between RPM and Kinect for absolute displacement values. Results: Analysis of the data from all three systems indicates the relative motion obtained from the Kinect is both accurate and in sync with the data from RPM and Anzai. The absolute displacement data from RPM and Kinect show similar displacement values throughout the acquisition except for the depth obtained from the Kinect during maximum exhalation (largest distance from Kinect). Conclusion: By simply utilizing the depth data of specific points on a patient obtained from the Kinect, respiratory motion can be tracked and visualized with accuracy comparable to that of the Varian RPM and Anzai belt.

Seismic damage mechanism and dynamic deformation characteristic analysis of mountain tunnel after Wenchuan earthquake

After the 2008 Wenchuan earthquake (Mw=8.3), many mountain highway tunnels in the affected area were severely damaged. In order to improve the current knowledge about the seismic performance of mountain tunnels under strong earthquakes, a forensic investigation was conducted on 52 tunnels after the earthquake. Based on the seismic damage data, the damage level of the inspected tunnels was classified using a new damage evaluation criterion. Subsequently, typical seismic damage characteristics and mechanisms of mountain tunnels were analyzed based on three different damage patterns: damage to shallow tunnel, damage to deep-buried tunnel structure and damage to pavement. Finally, based on the relative displacement (RD) method, a three-dimensional numerical model was developed to investigate the deformation characteristics of the portal structure under a strong earthquake. The numerical results showed that the tunnel lining cross section exhibited an alternate tension–compression deformation at the diagonal directions, and the relative displacement value of the upper-structure (above the sidewall) was generally more than that of the lower-structure (under the sidewall). Three stress states of the lining were deduced from the numerical model, which provided a good interpretation for the seismic tunnel damages observed after the Wenchuan earthquake.