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Academic literature on the topic 'Imagined body kinematics'

Author: Grafiati
Published: 30 May 2022
Last updated: 31 May 2022

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Journal articles on the topic "Imagined body kinematics"

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Zhou, Chen, Xin-Hui Liu, Wei Chen, Fei-Xiang Xu, and Bing-Wei Cao. "Distribution of driving force beneath wheeled vehicle with varying center of gravity." Advances in Mechanical Engineering 11, no. 1 (January 2019): 168781401982559. http://dx.doi.org/10.1177/1687814019825591.

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Driving force analysis is performed on the no-spin differential and full-time all-wheel-drive vehicle; this thesis takes an automatic loading mixing vehicle as an example to introduce the compositions and working principle of the driving system. Based on the tire-ground mechanics, the model of the dynamics and the kinematics is established under the walking straight and steering conditions. According to the theoretical model, the influence of the vehicle’s gravity center on the moving system is analyzed. Co-simulation based on LMS Imagine Lab AMESim and LMS Virtual Lab Motion is performed to build the hydraulic driving system and the multi-body dynamics system models. Based on the tire-ground load environment simulation model built by 1D + 3D, various positions of the gravity center of the model are set to compare with the theoretical analysis. Various weight blocks are also added to change the location of the gravity center in the practical experiment. The conclusions that different gravity center positions lead to the change of the driving torque distribution are proved by the simulation results and experimental data.
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DelSole, Edward M., and John J. Mercuri. "Utility of Upright Weight-bearing Imaging in Total Hip Arthroplasty." Seminars in Musculoskeletal Radiology 23, no. 06 (November 19, 2019): 603–8. http://dx.doi.org/10.1055/s-0039-1697935.

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AbstractPlanning for total hip arthroplasty (THA) has traditionally been performed using static supine anteroposterior radiographs of the pelvis. Recent advances in imaging technology and the understanding of human spinopelvic kinematics have made weight-bearing radiography an important adjunct to supine imaging. Hip surgeons can use weight-bearing imaging to optimize THA component position to prevent hip instability and early component wear. The goal of this narrative review is to delineate the fundamentals of spinopelvic kinematics, the benefits of surgical planning using weight-bearing radiography, and the underpinnings of upright full-body stereoradiography as a useful adjunct to traditional supine radiographs.
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Gong, Zhen, and Huw Wiltshire. "Review on the Effects of High Heeled on Body Posture Based on Medical Images." Journal of Medical Imaging and Health Informatics 10, no. 5 (May 1, 2020): 1165–70. http://dx.doi.org/10.1166/jmihi.2020.3014.

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Purpose: From a motor control perspective, the balance and propulsion are needed to proceed smoothly, and using high heeled shoes based on two conditions led to more difficult and complex gait. High heeled alter the natural form of body and present a chain reaction of disadvantageous affected that throughout the entire body from the toe to spine. Therefore, the purpose of this review provides a comprehensive guide of understanding HH gait. Methods: Electronic database which includes PubMed, Embase, Medline, Amed, and Cinahl were searched for controlled trials comparing high heeled shoes with barefoot or flat shoes, which include changes of the lower limb and upper limb. The kinematic change of body was the primary outcome measure. The comparison was conducted with mean differences and 95% confidence intervals. Result: Major findings were focused on the joint of the ankle, knee, hip, pelvis, and spine. The results of collecting articles show that a significant difference in ankle and knee joint during the gait when high heels and barefoot are compared. There are still conflicting results in terms of lumbar lordosis, and few studies indicate that the pelvic anteversion increased significantly. Conclusion: On direction for future research should establish an effective method to estimate the result of the HH effect on body posture.
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Choi, Ahnryul, Su-Bin Joo, Euichaul Oh, and Joung Mun. "Kinematic evaluation of movement smoothness in golf: relationship between the normalized jerk cost of body joints and the clubhead." BioMedical Engineering OnLine 13, no. 1 (2014): 20. http://dx.doi.org/10.1186/1475-925x-13-20.

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Rocca, Maria A., Roberto Gatti, Federica Agosta, Paola Tortorella, Elisa Riboldi, Paola Broglia, and Massimo Filippi. "Influence of body segment position during in-phase and antiphase hand and foot movements: A kinematic and functional MRI study." Human Brain Mapping 28, no. 3 (June 9, 2006): 218–27. http://dx.doi.org/10.1002/hbm.20271.

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Shanthini, J., P. Arunkumar, S. Karthik, and N. Karthikeyan. "Interpretation of Gait Supervising Mechanism Using Sensor Integrated Makeshift and Analysing Pattern by K-Means Clustering Algorithm." Journal of Medical Imaging and Health Informatics 11, no. 10 (October 1, 2021): 2598–609. http://dx.doi.org/10.1166/jmihi.2021.3847.

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Human mobility or walking pattern(gait) is described as the interpreter movements of the rotatory body to achieve extensive range of locomotion. Gait analysis is foremost widely used technique for identifying abnormalities in the lower extremities and gait characteristics essentially support HAT (Head, Arm & Trunk). The act of walking is unconscious when there are no dysfunctions, but for ambulated the continuous monitoring is required. The existing clinical analysis method couldn’t achieve the daily walking routine within the confinement of a room.The proposed method focuses on developing an ambulatory system on daily routines by incorporating feasible techniques for achieving the gait pattern which is not confined to a room atmosphere where all possibilities of walking pattern can’t be reached.This system has expounded an ideology, to interpret the gait parameters using an insole type shoe integrated sensor system. Here, a wearable gait system which is incorporated with force resistive sensors, piezo sensors, inertial sensors and IR sensors are interfaced to the ESP 32. The corresponding sensors extract the data of kinematic angles, kinetics, foot pressure, step count and foot stride investigations.The system proved to be efficient in finding the phases and orientation of the individual by interpreting values from the device. Acquired data can be clustered together to find the abnormal and normal values by applying K-Means clustering algorithm, later the values are utilized in biomechanics for rectifying posture or movement related problems.The device will have several applications in sports, rehabilitation medicine and post-surgery treatment.
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Saadat, Shabnam, Diana Perriman, Jennie M. Scarvell, Paul N. Smith, Catherine R. Galvin, Joseph Lynch, and Mark R. Pickering. "An efficient hybrid method for 3D to 2D medical image registration." International Journal of Computer Assisted Radiology and Surgery, April 18, 2022. http://dx.doi.org/10.1007/s11548-022-02624-0.

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Abstract Purpose The purpose of this paper is to present a method for registration of 3D computed tomography to 2D single-plane fluoroscopy knee images to provide 3D motion information for knee joints. This 3D kinematic information has unique utility for examining joint kinematics in conditions such as ligament injury, osteoarthritis and after joint replacement. Methods We proposed a non-invasive rigid body image registration method which is based on two different multimodal similarity measures. This hybrid registration method helps to achieve a trade-off among different challenges including, time complexity and accuracy. Results We performed a number of experiments to evaluate the performance of the proposed method. The experimental results show that the proposed method is as accurate as one of the most recent registration methods while it is several times faster than that method. Conclusion The proposed method is a non-invasive, fast and accurate registration method, which can provide 3D information for knee joint kinematic measurements. This information can be very helpful in improving the accuracy of diagnosis and providing targeted treatment.
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Sers, Ryan, Steph Forrester, Massimiliano Zecca, Stephen Ward, and Esther Moss. "Objective assessment of surgeon kinematics during simulated laparoscopic surgery: a preliminary evaluation of the effect of high body mass index models." International Journal of Computer Assisted Radiology and Surgery, July 24, 2021. http://dx.doi.org/10.1007/s11548-021-02455-5.

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Abstract Purpose Laparoscopy is used in many surgical specialties. Subjective reports have suggested that performing laparoscopic surgery in patients with a high body mass index (BMI) is leading to increased prevalence of musculoskeletal symptoms in surgeons. The aim of this study was to objectively quantify the impact on surgeon upper body kinematics and dynamic workload when performing simulated laparoscopy at different BMI levels. Methods Upper body kinematics and dynamic workload of novice, intermediate and expert surgeons were calculated based on measurements from inertial measurement units positioned on upper body segments. Varying thicknesses of foam were used to simulate patient BMIs of 20, 30, 40 and 50 kg/m2 during laparoscopic training. Results Significant increases in the jerkiness, angular speed and cumulative displacement of the head, torso and upper arms were found within all experience groups when subject to the 40 and 50 kg/m2 models. Novice surgeons were found to have less controlled kinematics and larger dynamic workloads compared to the more experienced surgeons. Conclusions Our findings indicate that performing laparoscopic surgery on a high BMI model worsens upper body motion efficiency and efficacy, and increases dynamic workload, producing conditions that are more physically demanding when compared to operating on a 20 kg/m2 model. These findings also suggest that the head, torso, and upper arm segments are especially affected by high BMI models and therefore exposure to patients with high BMIs may increase the risk of musculoskeletal injury when performing laparoscopic surgery.
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Trube, Niclas, Werner Riedel, and Matthias Boljen. "How muscle stiffness affects human body model behavior." BioMedical Engineering OnLine 20, no. 1 (June 2, 2021). http://dx.doi.org/10.1186/s12938-021-00876-6.

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Abstract Background Active human body models (AHBM) consider musculoskeletal movement and joint stiffness via active muscle truss elements in the finite element (FE) codes in dynamic application. In the latest models, such as THUMS™ Version 5, nearly all human muscle groups are modeled in form of one-dimensional truss elements connecting each joint. While a lot of work has been done to improve the active and passive behavior of this 1D muscle system in the past, the volumetric muscle system of THUMS was modeled in a much more simplified way based on Post Mortem Human Subject (PMHS) test data. The stiffness changing effect of isometric contraction was hardly considered for the volumetric muscle system of whole human body models so far. While previous works considered this aspect for single muscles, the effect of a change in stiffness due to isometric contraction of volumetric muscles on the AHBM behavior and computation time is yet unknown. Methods In this study, a simplified frontal impact using the THUMS Version 5 AM50 occupant model was simulated. Key parameters to regulate muscle tissue stiffness of solid elements in THUMS were identified for the material model MAT_SIMPLIFIED_FOAM and different stiffness states were predefined for the buttock and thigh. Results During frontal crash, changes in muscle stiffness had an effect on the overall AHBM behavior including expected injury outcome. Changes in muscle stiffness for the thigh and pelvis, as well as for the entire human body model and for strain-rate-dependent stiffness definitions based on literature data had no significant effect on the computation time. Discussion Kinematics, peak impact force and stiffness changes were in general compliance with the literature data. However, different experimental setups had to be considered for comparison, as this topic has not been fully investigated experimentally in automotive applications in the past. Therefore, this study has limitations regarding validation of the frontal impact results. Conclusion Variations of default THUMS material model parameters allow an efficient change in stiffness of volumetric muscles for whole AHBM applications. The computation time is unaffected by altering muscle stiffness using the method suggested in this work. Due to a lack of validation data, the results of this work can only be validated with certain limitations. In future works, the default material models of THUMS could be replaced with recently published models to achieve a possibly more biofidelic muscle behavior, which would even allow a functional dependency of the 1D and 3D muscle systems. However, the effect on calculation time and model stability of these models is yet unknown and should be considered in future studies for efficient AHBM applications.
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Wochner, Isabell, Lennart V. Nölle, Oleksandr V. Martynenko, and Syn Schmitt. "‘Falling heads’: investigating reflexive responses to head–neck perturbations." BioMedical Engineering OnLine 21, no. 1 (April 16, 2022). http://dx.doi.org/10.1186/s12938-022-00994-9.

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Abstract Background Reflexive responses to head–neck perturbations affect the injury risk in many different situations ranging from sports-related impact to car accident scenarios. Although several experiments have been conducted to investigate these head–neck responses to various perturbations, it is still unclear why and how individuals react differently and what the implications of these different responses across subjects on the potential injuries might be. Therefore, we see a need for both experimental data and biophysically valid computational Human Body Models with bio-inspired muscle control strategies to understand individual reflex responses better. Methods To address this issue, we conducted perturbation experiments of the head–neck complex and used this data to examine control strategies in a simulation model. In the experiments, which we call ’falling heads’ experiments, volunteers were placed in a supine and a prone position on a table with an additional trapdoor supporting the head. This trapdoor was suddenly released, leading to a free-fall movement of the head until reflexive responses of muscles stopped the downwards movement. Results We analysed the kinematic, neuronal and dynamic responses for all individuals and show their differences for separate age and sex groups. We show that these results can be used to validate two simple reflex controllers which are able to predict human biophysical movement and modulate the response necessary to represent a large variability of participants. Conclusions We present characteristic parameters such as joint stiffness, peak accelerations and latency times. Based on this data, we show that there is a large difference in the individual reflexive responses between participants. Furthermore, we show that the perturbation direction (supine vs. prone) significantly influences the measured kinematic quantities. Finally, ’falling heads’ experiments data are provided open-source to be used as a benchmark test to compare different muscle control strategies and to validate existing active Human Body Models directly.
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Dissertations / Theses on the topic "Imagined body kinematics"

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Залевський, Владислав Володимирович. "Система аналізу даних уявної кінематики тіла із використанням методів глибинного навчання." Bachelor's thesis, КПІ ім. Ігоря Сікорського, 2021. https://ela.kpi.ua/handle/123456789/45447.

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Дипломна робота: 137 с., 13 табл., 32 рис., 2 додатки, 42 джерела. У роботі розглянуто та проаналізовано найбільш поширені методи та підходи глибинного навчання для аналізу даних ЕЕГ уявної кінематики тіла. Досліджено різні методи аугментації даних та попередньої обробки. Робота обраних для роботи методів була розглянута на практичній задачі, а саме класифікації уявних дій піддослідних. Об’єктом дослідження стали медичні показники (записи ЕЕГ) та їх значення для створення на основі даних уявної кінематики тіла нейрокомп’ютерних інтерфейсів здатних працювати в реальному часі. Предметом дослідження стали математичні методи глибинного навчання навчання, попередньої обробки та аугментації даних.
Thesis: 137 p., 13 tabl., 32 fig., 2 appendices, 42 sources. In this work the most common deep learning methods for the analysis of EEG data of imagined body kinematics are considered and analyzed. Various methods of data augmentation and pre-processing are investigated. Chosen methods efficiency was analysed on a practical task, namely on the classification of imagined actions of the subjects. Medical indicators, namely EEG recordings, were considered as the study object. It also analysed their significance for the creation of brain-computer interfaces capable of working in real-time through imagined body kinematics data. The subjects of the study were mathematical methods of deep learning, data pre-processing and data augmentation.
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Conference papers on the topic "Imagined body kinematics"

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Abiri, Reza, Soheil Borhani, Xiaopeng Zhao, and Yang Jiang. "Real-Time Brain Machine Interaction via Social Robot Gesture Control." In ASME 2017 Dynamic Systems and Control Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/dscc2017-5128.

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Brain-Machine Interaction (BMI) system motivates interesting and promising results in forward/feedback control consistent with human intention. It holds great promise for advancements in patient care and applications to neurorehabilitation. Here, we propose a novel neurofeedback-based BCI robotic platform using a personalized social robot in order to assist patients having cognitive deficits through bilateral rehabilitation and mental training. For initial testing of the platform, electroencephalography (EEG) brainwaves of a human user were collected in real time during tasks of imaginary movements. First, the brainwaves associated with imagined body kinematics parameters were decoded to control a cursor on a computer screen in training protocol. Then, the experienced subject was able to interact with a social robot via our real-time BMI robotic platform. Corresponding to subject’s imagery performance, he/she received specific gesture movements and eye color changes as neural-based feedback from the robot. This hands-free neurofeedback interaction not only can be used for mind control of a social robot’s movements, but also sets the stage for application to enhancing and recovering mental abilities such as attention via training in humans by providing real-time neurofeedback from a social robot.
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Goffredo, M., M. Schmid, S. Conforto, Marco Carli, and Tommaso D'Alessio. "Posture kinematics reconstruction and body model creation." In Electronic Imaging 2004, edited by Edward R. Dougherty, Jaakko T. Astola, and Karen O. Egiazarian. SPIE, 2004. http://dx.doi.org/10.1117/12.526840.

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Eberharter, Johannes K., and Bahram Ravani. "Kinematic Registration Using Line Geometry." In ASME 2004 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/detc2004-57549.

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This paper uses line geometry to find an elegant solution to the kinematic registration problem involving reconstruction of a spatial displacement from data on three homologous points at two finitely separated positions of a rigid body. The bisecting linear line complex of two position theory in kinematics is used in combination with recent results from computational line geometry to present an elegant computational geometric method for the solution of this old problem. The results have applications in robotics, manufacturing, and biomedical imaging. The paper considers when minimal, over-determined, and perturbed sets of point data are given.
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Lalone, Emily A., Colin P. McDonald, Louis M. Ferreira, Terry M. Peters, Graham J. W. King, and James A. Johnson. "Visualization of 3D elbow kinematics using reconstructed bony surfaces." In SPIE Medical Imaging. SPIE, 2010. http://dx.doi.org/10.1117/12.844229.

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Amadi, Hippolite O. "A 3D Shoulder Scan Compatible Humeral Coordinate System for Glenohumeral Joint Kinematics." In ASME 2009 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2009. http://dx.doi.org/10.1115/sbc2009-206387.

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Advanced surgical planning techniques often require modeling the functional characteristics of the affected body region. Most patient-specific modeling in vivo relies on medical image scans that are expensive and may also allow patient’s exposure to ionizing radiation. This poses a challenge for the modeling of the kinematics of the glenohumeral joint (GHJ) based on the tissue geometries of the affected patients. The humeral morphology uniquely presents its canal (HC) and epicondyle (EC) axes as the two longest axes that are nearly orthogonal. This gives them the mathematical advantages as best axes for the definition of humeral coordinate system (HCS), especially from 2D radiographic images. This is however limited in 3D in vivo kinematics as minimization of radiation exposure may not allow medical imaging of the whole volume of interest all the way down to the distal epicondyles. It is therefore necessary that landmarks for use are captured within the field of view (FOV) of standard shoulder scans. This would avoid extra radiation exposure to patients and imaging cost as the scan might have been used earlier for traditional diagnosis. The aims of this study were to (1) confirm that HC-axis quantified from a ‘stack of discs (SOD)’ technique was the most reliable and consistent (2) identify the most closely oriented or most inter-subject related axis to the EC-axis for its replacement or prediction respectively from 3D proximal humeral scan and (3) use these to propose a HCS definition procedure that can be applied to a standard shoulder scan.
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Sheets, Alison L., Stefano Corazza, and Thomas Andriacchi. "An Automated Image-Based Method of 3D Subject Specific Body Segment Parameter Estimation." In ASME 2008 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2008. http://dx.doi.org/10.1115/sbc2008-193068.

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Recent studies have suggested that limb kinetics during swing or float phase movements are important for ACL injury analysis and injury prevention [1]. Kinetic (moment and force) calculations during swing phase can be sensitive to the accuracy of subject-specific body segment parameters (BSP) including mass and inertial properties. While numerous methods for estimating BSP have been implemented including regression equations [2,3], geometric body shape estimations, medical imaging and optimization approaches, they all have application specific limitations. Almost all of these BSP estimation approaches are limited by assumptions that: the mass center (CM) lies on the axis connecting the segment’s proximal and distal joint center, the body principle moments of inertia are aligned with the segment axes [4], and the right and left limbs are symmetric. These assumptions could introduce errors in 3D kinematic analysis. Non-invasive methods of measuring the exact geometry and volume of body segments have the potential to reduce most sources of error.
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Mihcin, S., D. White, R. Holbrey, R. J. Hodgson, A. C. Redmond, and R. K. Wilcox. "Co-Registration of MRI and Motion Analysis Marker Sets: Proof of Concept." In ASME 2011 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2011. http://dx.doi.org/10.1115/sbc2011-53390.

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When studying human kinematics, the intention is usually to isolate and model the movements of bony segments. With motion capture based on skin mounted marker systems, there is confounding of the extent to which the surface represents the movements of the underlying bony structures1 . Soft tissue artifact (STA) is an important confounder, caused by the relative movement between the skin mounted markers and the underlying bones. STA is a commonly encountered problem in biomechanics2 . Furthermore, for applications such as motion analysis of composite joints in the spine, wrist and ankle, the inability to associate surface markers closely with underlying bony segments has inhibited the construction of meaningful mechanical models3. The research question underpinning this program of work is whether it may be possible to use data from cross sectional imaging modalities in combination with surface mounted marker sets, to solve for the error associated with surface markers and so produce refined functional models of activities in real world settings.
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Vepa, Kameswara S., Diederik Van Nuffel, Wim Van Paepegem, and Joris Degrieck. "Fully Coupled Time Domain Modelling of 3D Floating Bodies and Mooring Systems in Regular and Irregular Sea States." In ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/omae2012-83464.

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Research on floating bodies like Wave Energy Converters (WECs) and Laser Imaging Detection And Ranging (LIDAR) systems has recently known a large growth. To study the minute details of the working model, it is important to study the effect of interactions between the waves, floating bodies and the mooring systems that are controlling the motion of the floating body. To achieve a more realistic numerical model in the time domain, a number of programs are linked together. The idea is to use the strength of each individual program for better results and also reduce the computational time. This paper provides a solution in the direction of using a fully coupled time domain coupling code that controls the data flow between a fluid solver, a structural solver, and a kinematic system simulator. Two- and three-dimensional fully coupled models are studied for calculation times and accuracy of results, and scaling is tested through parallelization on a large HPC cluster. The time step size of the whole model can be controlled by the user. Calculation times and memory requirements vary largely based on the factors like: domain size, SPH particle size, material model used for the floating body and the mooring system, complexity of the mechanical system inside the floating body. As a test case, a rigid body model is presented in this paper.
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Dzulkefli, Farah Syazana, Kefeng Xin, Ahmad Riza Ghazali, Guo Qiang, and Tariq Alkhalifah. "Full Wavefield Redatuming: Accurate Velocity Modelling for Imaging Beneath Complex Overburden." In International Petroleum Technology Conference. IPTC, 2021. http://dx.doi.org/10.2523/iptc-21771-ms.

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Abstract Salt is known for having a generally low density and higher velocity compared with the surrounding rock layers which causes the energy to scatter once the seismic wavefield hits the salt body and relatively less energy is transmitted through the salt to the deeper subsurface. As a result, most of imaging approaches are unable to image the base of the salt and the reservoir below the salt. Even the velocity model building such as FWI often fails to illuminate the deeper parts of salt area. In this paper, we show that Full Wavefield Redatuming (FWR) is used to retrieved and enhance the seismic data below the salt area, leading to a better seismic image quality and allowing us to focus on updating the velocity in target area below the salt. However, this redatuming approach requires a good overburden velocity model to retrieved good redatumed data. Thus, by using synthetic SEAM model, our objective is to study on the accuracy of the overburden velocity model required for imaging beneath complex overburden. The results show that the kinematic components of wave propagation are preserved through redatuming even with heavily smoothed overburden velocity model.
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Gupta, Deepika, Anirudh Udupa, and Koushik Viswanathan. "Some Quantitative Analogies Between Large-Strain Plasticity and Rectilinear Fluid Flow." In ASME 2020 15th International Manufacturing Science and Engineering Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/msec2020-8276.

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Abstract The mechanics of chip formation involves a complex interplay between surface plastic flow, material microstructure and tool-chip interface dynamics. At the continuum scale, this process has often been approximated as being one of pure shear along a very narrow zone — the shear plane. The primary assumption behind this approximation is that of steady or time-independent plastic flow. This approximation addresses the exception rather than the rule, since most metal cutting processes involve unsteady time-dependent plastic flows. In this work, we attempt to develop parallels with an analogous problem in fluid mechanics — flow past a rigid fixed body — to quantify the unsteady nature of plastic flow. Here the role of the body is played by the tool, and the flow field corresponds to the plastically deforming material. The prerequisite for fully exploiting this kinematic analogy is full-field material flow measurements. This is provided by digital image correlation (DIC), a family of techniques that use in situ imaging of the cutting process to obtain instantaneous full-field material displacements. Given this kinematic flow information, we show how one can describe the cutting process more accurately using the fluid flow analogy, and without having to resort to specific preconceived models. For steady flows, the analogy is more than merely cosmetic — the pathlines, streamlines and streaklines, all determined kinematically, coincide exactly. The analogy also allows consideration of time-dependent unsteady plastic flows that are usually beyond the purview of theoretical analyses. One can, for instance, ask the question of whether the transition from steady to unsteady plastic flow observed in metal cutting can be described by a dimensionless parameter, analogous to the Reynolds number for fluids. We show that in the case of unsteady flows, the actual deformation field is far removed from that described by conventional shear plane or slip line field models. Now the streaklines develop undulations or folds for the same boundary conditions as for the steady case (cutting velocity, depth of cut). Of the three flow lines, we attempt to extract information from streaklines, since they contain information about both spatial and temporal gradient. We present analyses of these streakline curvature features using simple geometric techniques that reflect both the spatial and temporal flow evolution. Our results shed light on the importance of considering unsteady flows in chip formation and machining. Borrowing ideas from fluids to describe these flows appears to hold significant promise for quantifying unsteady flows and their consequences for practical machining operations.
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