Simulated Motion Research Articles

Stimulus Onset Asynchrony Affects Weighting-related Event-related Spectral Power in Self-motion Perception.

Self-motion perception relies primarily on the integration of the visual, vestibular, proprioceptive, and somatosensory systems. There is a gap in understanding how a temporal lag between visual and vestibular motion cues affects visual-vestibular weighting during self-motion perception. The beta band is an index of visual-vestibular weighting, in that robust beta event-related synchronization (ERS) is associated with visual weighting bias, and robust beta event-related desynchronization is associated with vestibular weighting bias. The present study examined modulation of event-related spectral power during a heading judgment task in which participants attended to either visual (optic flow) or physical (inertial cues stimulating the vestibular, proprioceptive and somatosensory systems) motion cues from a motion simulator mounted on a MOOG Stewart Platform. The temporal lag between the onset of visual and physical motion cues was manipulated to produce three lag conditions: simultaneous onset, visual before physical motion onset, and physical before visual motion onset. There were two main findings. First, we demonstrated that when the attended motion cue was presented before an ignored cue, the power of beta associated with the attended modality was greater than when visual-vestibular cues were presented simultaneously or when the ignored cue was presented first. This was the case for beta ERS when the visual-motion cue was attended to, and beta event-related desynchronization when the physical-motion cue was attended to. Second, we tested whether the power of feature-binding gamma ERS (demonstrated in audiovisual and visual-tactile integration studies) increased when the visual-vestibular cues were presented simultaneously versus with temporal asynchrony. We did not observe an increase in gamma ERS when cues were presented simultaneously, suggesting that electrophysiological markers of visual-vestibular binding differ from markers of audiovisual and visual-tactile integration. All event-related spectral power reported in this study were generated from dipoles projecting from the left and right motor areas, based on the results of Measure Projection Analysis.

Optimizing the utilization of structural resources of flight simulator motion systems

The object of the study is a six degrees-of-freedom motion system of the synergistic type of a flight simulator. The latter is the main technical means for training pilots and means of research and development of aircraft. The task of optimal utilization of its structural resources was solved, which provides an opportunity to improve the quality of motion cueing. The result is the developed method, which ensures optimal use of structural resources of motion systems of flight simulators. This is explained, first of all, by the use of the developed simplified operator for converting the movements of jacks into the movement of a motion system along individual degrees of freedom on the basis of quadratic approximation. Given this, it became possible to describe the coordinates of the centers of the axes of rotation of the motion system by cubic spline functions. Secondly, the solution of the task of estimating the structural resources of the motion system along linear degrees of freedom on the basis of the developed criterion was carried out by an effective modified method of the deformed polyhedron. This method combines the random search method in the first steps of the search and the gradient method in determining the global extremum. Thirdly, the problem of determining the dependence of the coordinates of the pitch and yaw axes along the pitch angle was stated and solved. Owing to the optimal utilization of the structural resources of motion systems, the coordinates of the axis of their rotation along pitch are as close as possible to the coordinate of the axis of the aircraft. Thus, the quality of motion cueing on the flight simulator is significantly increased and it is possible to use motion systems with shorter lengths of jacks, and therefore, to reduce the cost of their manufacture and operation

From ambient vibration data analysis to 1D ground-motion prediction of the Mj 5.9 and the Mj 6.5 Kumamoto earthquakes in the Kumamoto alluvial plain, Japan

We present horizontal ground motion predictions at a soft site in the Kumamoto alluvial plain for the Mj 5.9 and Mj 6.5 Kumamoto earthquakes of April 2016, in the framework of an international blind prediction exercise. Such predictions were obtained by leveraging all available information which included: (i) analysis of earthquake ground motions; (ii) processing of ambient vibration data (AMV); and (iii) 1D ground response analysis. Spectral analysis of earthquake ground-motion data were used to obtain empirical estimates of the prediction site amplification function, with evidence of an amplification peak at about 1.2 Hz. Horizontal-to-vertical spectral ratio analysis of AMV confirmed this resonance frequency and pointed out also a low-frequency resonance around 0.3 Hz at the prediction site. AMV were then processed by cross-correlation, modified spatial autocorrelation and high-resolution beamforming methods to retrieve the 1D shear-wave velocity (Vs) structure at the prediction site by joint inversion of surface-wave dispersion and ellipticity curves. The use of low frequency dispersion curve and ellipticity data allowed to retrieve a reference Vs profile down to few thousand meters depth which was then used to perform 1D equivalent-linear simulations of the M 5.9 event, and both equivalent-linear and nonlinear simulations of the M 6.5 event at the target site. Adopting quantitative goodness-of-fit metrics based on time–frequency representation of the signals, we obtained fair-to-good agreement between 1D predictions and observations for the Mj 6.5 earthquake and a poor agreement for the Mj 5.9 earthquake. In terms of acceleration response spectra, while ground-motion overpredictions were obtained for the Mj 5.9 event, simulated ground motions for the Mj 6.5 earthquake severely underestimate the observations, especially those obtained by the nonlinear approach.Graphical

Early Postoperative Activities of Daily Living Do Not Adversely Affect Joint Torques or Translation Regardless of Capsular Condition: A Cadaveric Study

To evaluate the impact of capsular management on joint constraint and femoral head translations during simulated activities of daily living (ADL). Using 6 (n= 6) cadaveric hip specimens, the effect of capsulotomies and repair was then evaluated during simulated ADL. Joint forces and rotational kinematics associated with gait and sitting, adopted from telemeterized implant studies, were applied to the hip using a 6-degrees of freedom (DOF) joint motion simulator. Testing occurred after creation of portals, interportal capsulotomy (IPC), IPC repair, T-capsulotomy (T-Cap), partial T-Cap repair, and full T-Cap repair. The anterior-posterior (AP), medial-lateral (ML), and axial compression DOFs were operated in force control, whereas flexion-extension, adduction-abduction, and internal-external rotation were manipulated in displacement control. Resulting femoral head translations and joint reaction torques were recorded and evaluated. Subsequently, the mean-centered range of femoral head displacements and peak signed joint restraint torques were calculated and compared. During simulated gait and sitting, the mean range of AP femoral head displacements with respect to intact exceeded 1% of the femoral head diameter after creating portals, T-Caps, and partial T-Cap repair (Wilcoxon signed rank P < .05); the mean ranges of ML displacements did not. Deviations in femoral head kinematics varied by capsule stage but were never very large. No consistent trends with respect to alterations in peak joint restrain torques were observed. In this cadaveric biomechanical study, capsulotomy and repair minimally affected resultant femoral head translation and joint torques during simulated ADLs. The tested ADLs appear safe to perform after surgery, regardless of capsular status, because adverse kinematics were not observed. However, further study is required to determine the importance of capsular repair beyond time-zero biomechanics and the resultant effect on patient-reported outcomes.

Undamped, Damped and Forced Motion, Physical Simulation with the Geogebra Tool

Currently due to the pandemic situation that has affected the world community without distinction of languages, customs and creeds, technology was incorporated massively to achieve the continuity of progress in research, and development of culture and academic education, through this progress. As an introduction we can mention that this research is achieved by the need to do physics using other tools easy to manipulate with basic programming knowledge, likewise in the repositories there are many other studies that applied computationally the development of simulations of different physical phenomena. The method to use is the GeoGebra tools applying the basic syntax that is obtained by entering the equations in the input bar of the GeoGebra software already preset, being these equations calculated many times by students using differential equations, which obtains the solution equation dependent on mass and time, in this way the simulation, undamped, damped and forced motion are achieved, with the aim to show in this research that physics can be done using tools for academic use, due to this software is not exactly a research tool, but it can simulate phenomena that have already been shown in experimental and computational laboratories. The results obtained are very interesting since they present an originality in its simulation in an objective way showing dynamically the oscillation and the appearance of the functions that correspond to it in the development of the movement of the spring mass system.

MATHEMATICAL MODEL OF STABLE EQUILIBRIUM OPERATION OF THE FLIGHT SIMULATOR BASED ON THE STEWART PLATFORM

This paper analyses the available mathematical models of flight simulators based on the Stewart platform. It was found that there is no model that describes the conditions for stable dynamic equilibrium operation of the Stewart platform as a function of a number of important motion parameters. In this context, a new physical model is proposed based on classical models of theoretical mechanics using the d’Alembert formalism, the concept of stable equilibrium of a mechanical system. This model mathematically separates the stable equilibrium of the flight simulator motion system from the general uniformly accelerated motion. The systems of equations obtained in the framework of the model connect the physical and geometrical parameters of the Stewart platform and make it possible to determine the reactions in the upper hinges of the platform support, the limit values of the position angles in the space of the base of the support of the Stewart platform, under which the condition of stable equilibrium operation of the Stewart platform is satisfied. The proposed physical model and the analytical relations obtained on its basis are of great practical importance: the operator controlling the operation of the Stewart platform-based flight simulator can control the range of parameters during training so as not to bring the flight simulator out of stable equilibrium.

Towards autonomous contact-free operations in aquaculture

As offshore fish farms are established farther away from the shore, increased exposure to the elements prevents regular operations from being performed safely with vessels moored alongside the flexible fish cage and personnel performing tasks standing on the collar. Due to the higher environmental impact at more exposed locations, new concepts and solutions for automating daily aquaculture operations need to be developed. One solution that has been proposed is to carry out operations using a robotic arm mounted on the main deck of a service vessel while it does stationkeeping next to the cage. The purpose of this article is to summarise our research on the viability of this concept. Vessel motions are simulated for a representative vessel model and realistic sea states, and a robotic arm does motion-compensated trajectory tracking while mounted on a hexapod platform moving according to the simulated vessel motions. Relevant challenges in marine aquaculture operations are summarised, the method used to obtain realistic simulated vessel motions is documented, the results of the experiments are presented, and the remaining open questions to evaluate the potential of the proposed system are discussed.

Convolutional variational autoencoder for ground motion classification and generation toward efficient seismic fragility assessment

AbstractThis study develops an end‐to‐end deep learning framework to learn and analyze ground motions (GMs) through their latent features, and achieve reliable GM classification, selection, and generation of simulated motions. The framework is composed of an analysis workflow that transforms and reconstructs GMs through short‐time Fourier transform (STFT), encodes and decodes their latent features through convolutional variational autoencoder (CVAE), and classifies and generates GMs by grouping and interpolating latent variables. A benchmark study is established to confirm the minor difference between original GMs and the corresponding reconstructed accelerograms. The encoded latent space reveals that certain latent variables are directly linked to the dominant physical features of GMs. Resultantly, clustering latent variables using the k‐means algorithm successfully classifies GMs into different groups that vary in earthquake magnitude, soil type, field distance, and fault mechanism. By linearly interpolating two parent latent variables, simulated GMs are generated with consistent class information and matching response spectra. Furthermore, seismic fragility models are developed for a steel frame building and a concrete bridge using different sets of GMs. Using five classified, top‐ranked motions, regardless of recorded or simulated accelerograms, can achieve reasonable and efficient fragility estimates compared to the case that adopts 230 GMs. The proposed deep learning framework addresses two compelling questions regarding seismic fragility assessment: How many GMs are sufficient and what types of motions should be selected.

Comparative analysis of signal accuracy of three SpO2 monitors during motion and low perfusion conditions

To compare pulse oximetry performance during simulated conditions of motion and low perfusion in three commercially available devices: GE HealthCare CARESCAPE ONE TruSignal SpO2 Parameter, Masimo RADICAL-7 and Medtronic Nellcor PM1000N. After IRB approval, 28 healthy adult volunteers were randomly assigned to the motion group (N = 14) or low perfusion (N = 14) group. Pulse oximeters were placed on the test and control hands using random assignment of digits 2–5. Each subject served as their own control through the series of repeated pair-wise measurements. Reference co-oximetry oxyhemoglobin (SaO2) measurements from the radial artery were also obtained in the motion group. SpO2 readings were compared between the test and control hands in both groups and to SaO2 measurements in the motion group. Accuracy was assessed through testing of accuracy root-mean squared (ARMS) and mean bias. In the simulated motion test group the overall Accuracy Root Mean Square (ARMS) versus SaO2 was 1.88 (GE), 1.79 (Masimo) and 2.40 (Nellcor), with overall mean bias of − 0.21 (Masimo), 0.45 (GE), and 0.78 (Nellcor). In the motion hand, ARMS versus SaO2 was 2.45 (GE), 3.19 (Masimo) and 4.15 (Nellcor), with overall mean bias of − 0.75 (Masimo), − 0.01 (GE), and 0.04 (Nellcor). In the low perfusion test group, ARMS versus the control hand SpO2 for low PI was 3.24 (GE), 3.48 (Nellcor) and 4.76 (Masimo), with overall bias measurements of − 0.53 (Nellcor), 0.96 (GE) and 1.76 (Masimo). Experimental results for all tested devices met pulse oximetry regulatory and testing standards requirements. Overall, SpO2 device performance across the three devices in this study was similar under both motion and low perfusion conditions. SpO2 measurement accuracy degraded for all three devices during motion as compared to non-motion. Accuracy also degraded during normal to low, very low, or ultra low perfusion and was more pronounced compared to the changes observed during simulated motion. While some statistically significant differences in individual measurements were found, the clinical relevance of these differences requires further study.

A Novel Decoupled Model Predictive Control-Based Motion Cueing Algorithm for Driving Simulators

The motion cueing algorithm (MCA) is used to reproduce the driving/flying motion sensation of the real land or air vehicles for the users of motion simulator. Highly accurate MCAs are required for the motion simulators to create realistic sensation for the simulator users, otherwise, they might cause motion sickness and user discomfort. Model predictive control (MPC) is a popular technique in development of the high-fidelity MCAs as it is able to consider the motion sensation as well as the workspace constraints of the simulator platform. Tilt coordination in MCA is in charge of creating sustained linear acceleration feeling through tilting the platform cabin and exploiting gravitational acceleration under human motion threshold, to not allow the user to perceive this as a rotational motion. However, the existing MPC-based MCAs have not considered the rate limit to constrain the tilt motion under human threshold which causes violations of the rotational sensation threshold during generating sustained acceleration feeling. Instead, some researchers increase the penalty weights of rotational motions in order to slow down rotational motions. Using this strategy slows down all the simulator rotational motions not only the ones coming from tilt coordination, to generate sustained acceleration feeling, but also from rotational channel (due to real vehicle rotation) which causes motion sensation error and consequently motion sickness. Therefore, as the existing MPC-based MCAs cannot differentiate the rotations of tilt coordination channel (due to sustained acceleration feeling generation), from rotational channel (due to vehicle rotational motions), they are not able to produce accurate rotational motion sensations because of insufficient rotational motions. In this research, a novel decoupled MPC-based MCA is developed to systematically address the issues related to the existing MPC-based MCAs, in terms of inaccurate motion generation, by redesigning the MPC-based MCA using a series of vestibular system-based MPC models and considering tilt rate limit in tilt coordination. The simulation study using MATLAB software is used to verify and validate the proposed MCA compared to the existing MCAs. The proposed decoupled MPC-based MCA is able to generate accurate motion cues compared to those of the existing MCAs.

Nonzero Phase Shifts of Acoustic Waves in the Lower Solar Atmosphere Measured from Realistic Simulations and Their Role in Local Helioseismology* *Current Version: 0.00.

Previous studies analyzing the evanescent nature of acoustic waves in the lower solar atmosphere, up to 300 km above the photosphere, have shown an unexpected phase shift of an order of 1 s between different heights. Those studies investigated the spectral line Fe i λ6173.3, commonly used for helioseismic measurements. Such phase shifts can contribute to a misinterpretation of the measured travel times in local helioseismology, complicating inferences of, e.g., the deep meridional flow. In this study, we carry out phase shift computations using a simulated, fully radiative, and convective atmosphere from which the Fe i λ6173.3 line is synthesized. The resulting phase shifts as functions of frequency across multiple heights show nonzero values in evanescent waves, similar to what was found in observational data. Comparing the Doppler velocities estimated from the synthesized absorption line with the true velocities directly obtained from the simulated plasma motions, we find substantial differences in phase shifts between the two. This leads us to hypothesize that the nonadiabaticity of the solar atmosphere yields extra phase shift contributions to Doppler velocities. Finally, computing phase differences for different viewing angles reveals a systematic center-to-limb variation, similar to what is present in observations. Overall, this study helps to improve our understanding of the physical cause of the helioseismic center-to-limb effect.

Design of Hardware-in-the-loop Simulation System for Image-guided Missiles

This paper introduces a design method of a hardware-in-the-loop simulation system applied to a certain type of image-guided missile. By studying the characteristics of a certain type of image-guided missile, the working principle of the image-guidance system is analyzed, the mathematical simulation scheme and the hardware-in-the-loop simulation scheme are designed, and the working mechanism of RTX is analyzed. Established a real-time hardware-in-the-loop simulation system based on RTX+Windows, analyzed the delay of the simulation computer, the simulated launch control computer, the flight motion simulator and the image simulator, and finally integrated the flight data and missed target amount of the hardware-in-the-loop simulation test, and obtained the hardware-in-the-loop simulation system meets the requirements.

Learning-Based Distortion Compensation for a Hybrid Simulator of Space Docking

By effectively utilizing the fidelity of a physical simulation and the flexibility of a numerical simulation, the hybrid simulation is applicable to test the complicated docking contact process of various kinds of spacecraft. However, the hybrid simulation of space docking often has a divergence or convergence distortion due to phase delays and structure dynamics in the system loops. In many cases, it is difficult to derive the loop models based on the first-principle for the compensator design. In this study, a learning-based distortion compensation method is proposed to compensate for the phase delays and structure dynamics existing in the simulator. The measurement system delay of the contact force is compensated by a learning-based force compensator (LFC). For the motion simulator, the delay of the actuation system of the lower platform is compensated by a learning-based actuation compensator (LAC), and the structure dynamics of the lower and upper platforms are compensated by a learning-based structure compensator (LSC). The proposed learning-based distortion compensation method does not require the system models. Some verifications show that the hybrid simulation error can be reduced and good accuracy can be achieved.

Stochastic Ground-Motion Simulation of the 2021 Mw 5.9 Woods Point Earthquake: Facilitating Local Probabilistic Seismic Hazard Analysis in Australia

ABSTRACT The 2021 Mw 5.9 Woods Point event is the largest onshore earthquake that has occurred in the recorded history of southeastern Australia since European settlement. To study its source and ground-motion characteristics and to extract information for local seismic hazard analysis, we employ a stochastic finite-fault simulation approach to simulate ground motions for this event based on the observations collected from 36 onshore stations. We determine the regional distance-dependent attenuation parameters using the horizontal Fourier acceleration amplitude spectrum in the frequency range of 0.1–20 Hz. We parameterize path parameters using different models to consider uncertainties and sensitivities. To investigate local site effects, we construct a VS30-based site amplification model. Source parameters are then determined by fitting the theoretical Brune’s ω2 model with a reference Fourier source spectrum at 1.0 km. The κ0 value for the reference rock site is estimated as κ0=0.01 s, and dynamic stress drop is found to be 41.0 MPa by minimizing the overall absolute residual of 5% damped pseudospectral acceleration. We validate the simulations by comparing simulated and observed ground motions in terms of various intensity measurements; analyses of residuals show that the simulations are in good agreement with observations (average residual is close to 0). To facilitate future probabilistic seismic hazard analysis, six selected ground-motion models are ranked using the deviance information criteria based on an independent data set consisting of field observations and simulated ground motions.

3D physics-based ground motion simulation and topography effects of the 05 September 2022 MW6.6 Luding earthquake, China

On September 5, 2022, a MW6.6 earthquake occurred in Luding, Sichuan Province, which caused a large number of casualties and serious damage to infrastructures. To represent the strong ground motion of the destructive shock, the SPECFEM 3D code is adopted to model the wave propagation and a hybrid kinematic source to model the fault rupture. As for the hybrid fault source, spatial heterogeneities aimed to simulate the high-frequency radiation are added to a prescribed asperity model used to generate the low-frequency part. With a conforming mesh of the established 100 km × 100 km × 60 km numerical model and the developed hybrid fault source, the maximum resolved frequency of the simulation is 5 Hz. First, the numerical model is validated by comparing the simulated results with the six recorded waveforms as well as the corresponding Spectral acceleration and Fourier amplitude spectra. Then, the wave fields and Synthetic seismograms are presented to investigate the velocity pulse-like ground motion in the near-fault region. Finally, the topographic effect on the ground motions is identified by comparing the results from the numerical model with (Topo) and without topography (Flat). It is demonstrated that the simulated ground motion well reproduces the near-fault fling-step effect and the wave scattering effect caused by the surface topography. The hill-canyon topography significantly amplifies the surface motion, with the amplification factors (Topo/Flat) of PGV at the peak of Gonggashan mountain and at the bottom of Daduhe river reach 1.9 and 1.4, respectively. Moreover, the PGV amplification factor is in good correlation with the topography's elevation, indicating that the topographic amplification can be predicted by establishing the relationship between amplification factor and elevation.

Evaluation of motion artefact reduction depending on the artefacts’ directions in head MRI using conditional generative adversarial networks

Motion artefacts caused by the patient’s body movements affect magnetic resonance imaging (MRI) accuracy. This study aimed to compare and evaluate the accuracy of motion artefacts correction using a conditional generative adversarial network (CGAN) with an autoencoder and U-net models. The training dataset consisted of motion artefacts generated through simulations. Motion artefacts occur in the phase encoding direction, which is set to either the horizontal or vertical direction of the image. To create T2-weighted axial images with simulated motion artefacts, 5500 head images were used in each direction. Of these data, 90% were used for training, while the remainder were used for the evaluation of image quality. Moreover, the validation data used in the model training consisted of 10% of the training dataset. The training data were divided into horizontal and vertical directions of motion artefact appearance, and the effect of combining this data with the training dataset was verified. The resulting corrected images were evaluated using structural image similarity (SSIM) and peak signal-to-noise ratio (PSNR), and the metrics were compared with the images without motion artefacts. The best improvements in the SSIM and PSNR were observed in the consistent condition in the direction of the occurrence of motion artefacts in the training and evaluation datasets. However, SSIM > 0.9 and PSNR > 29 dB were accomplished for the learning model with both image directions. The latter model exhibited the highest robustness for actual patient motion in head MRI images. Moreover, the image quality of the corrected image with the CGAN was the closest to that of the original image, while the improvement rates for SSIM and PSNR were approximately 26% and 7.7%, respectively. The CGAN model demonstrated a high image reproducibility, and the most significant model was the consistent condition of the learning model and the direction of the appearance of motion artefacts.

Development of Multibundle Virtual Ligaments to Simulate Knee Mechanics After Total Knee Arthroplasty.

Preclinical evaluation of total knee arthroplasty (TKA) components is essential to understanding their mechanical behavior and developing strategies for improving joint stability. While preclinical testing of TKA components has been useful in quantifying their effectiveness, such testing can be criticized for lacking clinical relevance, as the important contributions of surrounding soft tissues are either neglected or greatly simplified. The purpose of our study was to develop and determine if subject-specific virtual ligaments reproduce a similar behavior as native ligaments surrounding TKA joints. Six TKA knees were mounted to a motion simulator. Each was subjected to tests of anterior-posterior (AP), internal-external (IE), and varus-valgus (VV) laxity. The forces transmitted through major ligaments were measured using a sequential resection technique. By tuning the measured ligament forces and elongations to a generic nonlinear elastic ligament model, virtual ligaments were designed and used to simulate the soft tissue envelope around isolated TKA components. The average root-mean-square error (RMSE) between the laxity results of TKA joints with native versus virtual ligaments was 3.5 ± 1.8 mm during AP translation, 7.5 ± 4.2 deg during IE rotations, and 2.0 ± 1.2 deg during VV rotations. Interclass correlation coefficients (ICCs) indicated a good level of reliability for AP and IE laxity (0.85 and 0.84). To conclude, the advancement of virtual ligament envelopes as a more realistic representation of soft tissue constraint around TKA joints is a valuable approach for obtaining clinically relevant kinematics when testing TKA components on joint motion simulators.

Biomechanical effect of endplate defects on the intermediate vertebral bone in consecutive two-level anterior cervical discectomy and fusion: a finite element analysis

BackgroundIntermediate vertebral collapse is a newly discovered complication of consecutive two-level anterior cervical discectomy and fusion (ACDF). There have been no analytical studies related to the effects of endplate defects on the biomechanics of the intermediate vertebral bone after ACDF. This study aimed to compare the effects of endplate defects on the intermediate vertebral bone biomechanics in the zero-profile (ZP) and cage-and-plate (CP) methods of consecutive 2-level ACDF and to determine whether collapse of the intermediate vertebra is more likely to occur using ZP.MethodsA three-dimensional finite element (FE) model of the intact cervical spine (C2–T1) was constructed and validated. The intact FE model was then modified to build ACDF models and imitate the situation of endplate injury, establishing two groups of models (ZP, IM-ZP and CP, IM-ZP). We simulated cervical motion, such as flexion, extension, lateral bending and axial rotation, and compared the range of motion (ROM), upper and lower endplate stress, fusion fixation device stress, C5 vertebral body stress, intervertebral disc internal pressure (intradiscal pressure, or IDP) and the ROM of adjacent segments in the models.ResultsThere was no significant difference between the IM-CP model and the CP model in the ROM of the surgical segment, upper and lower endplate stress, fusion fixation device stress, C5 vertebral body stress, IDP, or ROM of the adjacent segments. Compared with the CP model, the endplate stress of the ZP model is significantly higher in the flexion, extension, lateral bending and axial rotation conditions. Compared with the ZP model, endplate stress, screw stress, C5 vertebral stress and IDP in IM-ZP were significantly increased under flexion, extension, lateral bending and axial rotation conditions.ConclusionsCompared to consecutive 2-level ACDF using CP, collapse of the intermediate vertebra is more likely to occur using ZP due to its mechanical characteristics. Intraoperative endplate defects of the anterior lower margin of the middle vertebra are a risk factor leading to collapse of the middle vertebra after consecutive 2-level ACDF using ZP.

Quantitative strong motion simulations at three locations in downtown Mashiki during the 2016 Kumamoto Earthquake (Mw 7.0) based on the nonlinear ground response analyses with soil liquefaction

The mainshock of the 2016 Kumamoto Earthquake (Mw 7.0) caused extensive damage to buildings in downtown Mashiki, Kumamoto Prefecture, Japan. The heavy building damage in the area was associated with both strong ground motion and building response characteristics. Fortunately, there were two strong motion stations in the area and the observed records during the mainshock were distributed, showing peak ground velocities exceeding 100 cm/s on the surface. The level of shaking would be sufficient to make soft surface sediments nonlinear. To reproduce observed ground motions quantitatively, one-dimensional nonlinear effective-stress time-history analyses were conducted at three locations in downtown Mashiki. The input wave was employed as either the observed underground wave or simulated outcrop input motion based on the diffuse field theory. The main purpose of the study was twofold: to investigate the proper soil constitutive relationship and its nonlinear parameters based on the limited amount of in situ information, and to validate the method of input motion evaluation at the seismological bedrock level based on diffuse field theory. The nonlinear time history analyses using the on-site boring survey and the outcrop wave based on diffuse field theory showed that the waveform of the mainshock observed on the ground surface was explained with sufficient accuracy. In addition, the results of the effective stress analysis indicated that soil liquefaction might have occurred in the area with thick surface layers along the Akitsu River where the water table was considered to be quite shallow.Graphical

Motion Simulation of Autonomous Guided Vehicles

Autonomous Guided Vehicles (AGVs) using omnidirectional wheels can change their moving direction flexibly without the use of steering wheel. Is it possible that a vehicle with standard pneumatic wheels (as in a normal vehicle) change its moving direction flexibly by the technique of regulating the driving torque supplied to each wheel? In this article, the simulated motion trajectories of the two types of vehicles were presented, that are the vehicle using Mecanum wheels and the vehicle using standard pneumatic wheels (normal wheels). For vehicles with normal wheels, the simulation was carried out in two cases of motion direction control: with and without using a steering wheel. Further, the main loop of the motion direction control algorithm by regulating the driving torque to the wheels was also presented for a prototype of a vehicle with normal wheel, which was used to simulate the motion direction control experimentally. The topic will focus on motion simulation and the comparison of simulation results to evaluate the application ability of the mentioned technique in AGVs as well as in passenger cars.