Search results for: lateral motion

Authors: Xie Kai, Laith K. Abbas, Chen Dongyang, Yang Fufeng, Rui Xiaoting

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Effect of plunging motion on the pitch oscillating NACA0012 airfoil is investigated using computational fluid dynamics (CFD). A simulation model based on overset grid technology and k - ω shear stress transport (SST) turbulence model is established, and the numerical simulation results are compared with available experimental data and other simulations. Two cases of phase angle φ = 0, μ which represents the phase difference between the pitching and plunging motions of an airfoil are performed. Airfoil vortex generation, moving, and shedding are discussed in detail. Good agreements have been achieved with the available literature. The upward plunging motion made the equivalent angle of attack less than the actual one during pitching analysis. It is observed that the formation of the stall vortex is suppressed, resulting in a decrease in the lift coefficient and a delay of the stall angle. However, the downward plunging motion made the equivalent angle of attack higher the actual one.

Keywords: dynamic stall, pitching-plunging, computational fluid dynamics, helicopter blade rotor, airfoil

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Authors: Sundaresan Soundararajan, George Ezekiel Silvananthan, Chor Ngee Tan

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Introduction: Transforaminal Interbody Fusion (TLIF) has been adopted for many decades now, however, XLIF, still in relative infancy, has grown to be accepted as a new Minimally Invasive Surgery (MIS) option. There is a paucity of reports directly comparing lateral approach surgery to other MIS options such as TLIF in the treatment of lumbar degenerative disc diseases. Aims/Objectives: The objective of this study was to compare the efficacy and clinical outcomes between Minimally Invasive Transforaminal Interbody Fusion (TLIF) and Minimally Invasive Lateral Interbody Fusion (XLIF) in the treatment of patients with degenerative disc disease of the lumbar spine. Methods: A single center, retrospective cohort study involving a total of 38 patients undergoing surgical intervention between 2010 and 2013 for degenerative disc disease of lumbar spine at single L4/L5 level. 18 patients were treated with MIS TLIF, and 20 patients were treated with XLIF. Results: The XLIF group showed shorter duration of surgery compared to the TLIF group (176 mins vs. 208.3 mins, P = 0.03). Length of hospital stay was also significantly shorter in XLIF group (5.9 days vs. 9 days, p = 0.03). Intraoperative blood loss was favouring XLIF as 85% patients had blood loss less than 100cc compared to 58% in the TLIF group (P = 0.03). Radiologically, disc height was significantly improved post operatively in the XLIF group compared to the TLIF group (0.56mm vs. 0.39mm, P = 0.01). Foraminal height increment was also higher in the XLIF group (0.58mm vs. 0.45mm , P = 0.06). Clinically, back pain and leg pain improved in 85% of patients in the XLIF group and 78% in the TLIF group. Post op hip flexion weakness was more common in the XLIF group (40%) than in the TLIF group (0%). However, this weakness resolved within 6 months post operatively. There was one case of dural tear and surgical site infection in the TLIF group respectively and none in the XLIF group. Visual Analog Scale (VAS) score 6 months post operatively showed comparable reduction in both groups. TLIF group had Owsterty Disability Index (ODI) improvement on 67% while XLIF group showed improvement of 70% of its patients. Conclusions: Lateral approach surgery shows comparable clinical outcomes in resolution of back pain and radiculopathy to conventional MIS techniques such as TLIF. With significantly shorter duration of surgical time, minimal blood loss and shorter hospital stay, XLIF seems to be a reasonable MIS option compared to other MIS techniques in treating degenerative lumbar disc diseases.

Keywords: extreme lateral interbody fusion, lateral approach, minimally invasive, XLIF

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Authors: Mohamed Bendoukha, Mustapha Mosbah

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The Radiographic apparent assumed that the asymptomatic adjacent segment disease ASD is common after lumbar fusion, but this does not correlate with the functional outcomes while compensatory increased motion and stresses at the adjacent level of fusion is well-known to be associated to ASD. Newly developed, the hybrid stabilization are allocated to substituted for mostly the superior level of the fusion in an attempt to reduce the number of fusion levels and likelihood of degeneration process at the adjacent levels during the fusion with pedicle screws. Nevertheless, its biomechanical efficiencies still remain unknown and complications associated with failure of constructs such screw loosening and toggling should be elucidated In the current study, a finite element (FE) study was performed using a validated L2/S1 model subjected to a moment of 7.5 Nm and follower load of 400 N to assess the biomedical behavior of hybrid constructs based on dynamic topping off, semi rigid fusion. The residual range of motion (ROM), stress distribution at the fused and adjacent levels, stress distribution at the disc and the cage-endplate interface with respect to changes of bone quality were investigated. The hybrid instrumentation was associated with a reduction in compressive stresses compared to the fusion construct in the adjacent-level disc and showed high substantial axial force in the implant while fusion instrumentation increased the motion for both flexion and extension.

Keywords: intervertebral disc, lumbar spine, degenerative nuclesion, L4-L5, range of motion finite element model, hyperelasticy

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Authors: Bernstein Ran, Shafir Tal, Tsachor Rachelle, Studd Karen, Schuster Assaf

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Laban Movement Analysis (LMA), developed in the dance community over the past seventy years, is an effective method for observing, describing, notating, and interpreting human movement to enhance communication and expression in everyday and professional life. Many applications that use motion capture data might be significantly leveraged if the Laban qualities will be recognized automatically. This paper presents an automated recognition method of Laban qualities from motion capture skeletal recordings and it is demonstrated on the output of Microsoft’s Kinect V2 sensor.

Keywords: Laban movement analysis, multitask learning, Kinect sensor, machine learning

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Authors: Seungyeong Choi, Namkyu Lee, Dong Il Shim, Young Mun Lee, Yong-Ki Park, Hyung Hee Cho

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Effect of the cross-sectional geometry on heat transfer and particle motion of circulating fluidized bed riser for CO₂ capture was investigated. Numerical simulation using Eulerian-eulerian method with kinetic theory of granular flow was adopted to analyze gas-solid flow consisting in circulating fluidized bed riser. Circular, square, and rectangular cross-sectional geometry cases of the same area were carried out. Rectangular cross-sectional geometries were analyzed having aspect ratios of 1: 2, 1: 4, 1: 8, and 1:16. The cross-sectional geometry significantly influenced the particle motion and heat transfer. The downward flow pattern of solid particles near the wall was changed. The gas-solid mixing degree of the riser with the rectangular cross section of the high aspect ratio was the lowest. There were differences in bed-to-wall heat transfer coefficient according to rectangular geometry with different aspect ratios.

Keywords: bed geometry, computational fluid dynamics, circulating fluidized bed riser, heat transfer

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Authors: Saeed Rahjoo, Babak H. Mamaqani

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Concentric bracing systems have been in practice for many years because of their effectiveness in reducing seismic response. Depending on concept, seismic design codes provide various response modification factors (R), which itself consists of different terms, for different types of lateral load bearing systems but configuration of these systems are often ignored in the proposed values. This study aims at considering the effect of different x-bracing diagonal configuration on values of ductility dependent term in R computation. 51 models were created and nonlinear push over analysis has been performed. The main variables of this study were the suitable location of X–bracing diagonal configurations, which establishes better nonlinear behavior in concentric braced steel frames. Results show that some x-bracing diagonal configurations improve the seismic performance of CBF significantly and explicit consideration of lateral load bearing systems seems necessary.

Keywords: bracing configuration, concentrically braced frame (CBF), push over analyses, response reduction factor

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Authors: Hadjoui Abdelhamid, Saimi Ahmed

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The hybrid h-p finite element method for the dynamic behavior of nonlinear rotors is described in this paper. The standard h-version method of discretizing the problem is retained, but modified to allow the use of polynomially-enriched beam elements. A hierarchically enriching element will thus not affect the nodal displacement and rotation, but will influence the values of the nodal bending moment and shear force is used. The deterministic movements of rotation and translation of the support which are coupled to the excitations due to unbalance are also taken into account. We study also the geometric dissymmetry of the shaft and the disc, thus the equations of motion of the rotor contain variable parametric coefficients over time that can lead to a lateral dynamic instability. The effects of movements combined support for bearings are analyzed and discussed through Campbell diagrams and spectral analyses. A program is made in Matlab. After validation of the program, several examples are studied. The influence of physical and geometric parameters on the natural frequencies of the shaft is determined through the study of these examples. Among these parameters, we include the variation in the diameter and the thickness of the rotor, the position of the disc.

Keywords: Campbell diagram, critical speeds, nonlinear rotor, version h-p of FEM

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Authors: Yingyi Zhou, Tohru Kawabe

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With the spread of EVs (electric Vehicles), the ride comfort has been gaining a lot of attention. The influence of the lateral acceleration is important for the improvement of ride comfort of EVs as well as the longitudinal acceleration, especially upon turning of the vehicle. Therefore, this paper proposes a practical optimal speed control method to greatly improve the ride comfort in the vehicle turning situation. For consturcting this method, effective criteria that can appropriately evaluate deterioration of ride comfort is derived. The method can reduce the influence of both the longitudinal and the lateral speed changes for providing a confortable ride. From several simulation results, we can see the fact that the method can prevent aggravation of the ride comfort by suppressing the influence of longitudinal speed change in the turning situation. Hence, the effectiveness of the method is recognized.

Keywords: electric vehicle, speed control, ride comfort, optimal control theory, driving support system

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Authors: V. T. Ngo, D. M. Xie

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Frequently, in the design of machines, some of parameters that directly affect the rotor dynamics of the machines are not accurately known. In particular, bearing stiffness support is one such parameter. One of the most basic principles to grasp in rotor dynamics is the influence of the bearing stiffness on the critical speeds and mode shapes associated with a rotor-bearing system. Taking a rig shafting as an example, this paper studies the lateral vibration of the rotor with multi-degree-of-freedom by using Finite Element Method (FEM). The FEM model is created and the eigenvalues and eigenvectors are calculated and analyzed to find natural frequencies, critical speeds, mode shapes. Then critical speeds and mode shapes are analyzed by set bearing stiffness changes. The model permitted to identify the critical speeds and bearings that have an important influence on the vibration behavior.

Keywords: lateral vibration, finite element method, rig shafting, critical speed

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Authors: Erwin, Cheng-Cheng Chen, Charles J. Salim

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One of the method to solve the lateral torsional buckling (LTB) problem is by using side plates to increased the buckling resistance of the beam. Some modifications in designing the side plates are made in this study to simplify the construction in the field and reduce the cost. At certain region, side plates are not added: (1) At the beam end to preserve some spaces for bolt installation, but the beam is strengthened by adding cover plate at both flanges and (2) at the middle span of the beam where the moment is smaller. Three small scale full span beam specimens are tested under cyclic loading to investigate the LTB resistant and the ductility of the proposed design method. Test results show that the LTB deformation can be effectively suppressed and very high ductility level can be achieved. Following the test, a finite element analysis (FEA) model is established and is verified using the test results. An intensive parametric study is conducted using the established FEA model. The analysis reveals that the length of side plates is the most important parameter determining the performance of the beam and the required side plates length is determined by some parameters which are (1) beam depth to flange width ratio, (2) beam slenderness ratio (3) strength and thickness of the side plates, (4) compactness of beam web and flange, and (5) beam yield strength. At the end of the paper, a design formula to calculate the required side plate length is suggested.

Keywords: cover plate, earthquake resistant design, lateral torsional buckling, side plate, steel structure

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Authors: Soheil Arash Moghadam, Abdol R. Kashani Nia, Ali Akrami Zade

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Considering numerous applications of Autonomous Underwater Vehicles in various industries, there has been plenty of researches and studies on the motion control of such vehicles. One of the useful aspects for studying is the guidance of these vehicles. In this paper, while presenting motion equations with six degrees of freedom for Autonomous Underwater Vehicles, Proportional Navigation Guidance Law and the first order sliding mode control for TAIPAN AUV was used to address its guidance for the purpose of collision with a moving target.

Keywords: Autonomous Underwater Vehicle (AUV), degree of freedom (DOF), hydrodynamic, line of sight(LOS), proportional navigation guidance(PNG), sliding mode control(SMC)

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Authors: B. Kenny, M. Dixon, A. Boshell

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The use of alcoholic surgical prep was recently introduced into the Royal Newcastle Center for elective procedures. In the past 3 months there have been a significant number of burns believed to be related to ‘pooling’ of this surgical prep in patients undergoing procedures where they are placed in the lateral position with hip bolsters. The aim of the audit was to determine the reason for the burns, analyze what pre-existing factors may contribute to the development of the burns and what can be changed to prevent further burns occurring. All patients undergoing a procedure performed on the hip who were placed in the lateral position with sacral and anterior, superior iliac spine (ASIS) support with ‘bolsters’ were included in the audit. Patients who developed a ‘burn’ were recorded, details of the surgery, demographics, surgical prep used and length of surgery were obtained as well as photographs taken to document the burn. Measures were then taken to prevent further burns and the efficacy was documented. Overall 14 patients developed burns over the ipsilateral ASIS. Of these, 13 were Total Hip Arthroplasty (THA) and 1 was a removal of femoral nail. All patients had Chlorhexidine 0.5% in Alcohol 70% Tinted Red surgical preparation or Betadine Alcoholic Skin Prep (70% etoh). Patients were set up in the standard lateral decubitus position with sacral and bilateral ASIS bolsters with a valband covering. 86% of patients were found to have pre-existing hypersensitivities to various substances. There is very little literature besides a few case reports on surgical prep-related burns. The case reports that do exist are related to the use of tourniquet-related burns and there is no mention in the literature examining ‘bolster’ related burns. The burns are hypothesized to be caused by pooling of the alcoholic solution which is amplified by the use of Valband.

Keywords: arthroplasty, chemical burns, wounds, rehabilitation

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Authors: Zi-Ang Li, Mu-Xuan Tao

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During the process of the industrialization of steel structure housing, a composite structural system with separated gravity and lateral resistant systems has been applied in engineering practices, which consists of composite frame with hinged beam-column joints, steel brace and RC shear wall. As an attempt in steel structural system area, seismic performance evaluation of the separated composite structure is important for further application in steel housing. This paper focuses on the seismic performance comparison of the separated composite structural system and traditional steel frame-shear wall system under the same inter-story drift ratio (IDR) provision limit. The same architectural layout of a high-rise building is designed as two different structural systems at the same IDR level, and finite element analysis using pushover method is carried out. Static pushover analysis implies that the separated structural system exhibits different lateral deformation mode and failure mechanism with traditional steel frame-shear wall system. Different indexes are adopted and discussed in seismic performance evaluation, including IDR, safe factor (SF), shear wall damage, etc. The performance under maximum considered earthquake (MCE) demand spectrum shows that the shear wall damage of two structural systems are similar; the separated composite structural system exhibits less plastic hinges; and the SF index value of the separated composite structural system is higher than the steel frame shear wall structural system.

Keywords: finite element analysis, new composite structural system, seismic performance evaluation, static pushover analysis

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Authors: Ameer A. Jebur, William Atherton, Rafid M. Alkhaddar, Edward Loffill

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Understanding the behaviour of the piles under the action of the independent lateral loads and the precise prediction of the capacity of piles subjected to different lateral loads are vital topics in foundation design and analysis. Moreover, the laterally loaded behaviour of deep foundations penetrated in cohesive and non-cohesive soils is basically analysed by the Winkler Model (beam on elastic foundation), in which the interaction between the pile embedded depth and contacted soil is simulated by nonlinear p–y curves. The presence of many approaches to interpret the behaviour of soil-pile interaction has resulted in numerous outputs and indicates that no general approach has yet been adopted. The current study presents the result of numerical modelling of the behaviour of steel tubular piles (25.4mm) outside diameter with various embedment depth-to-diameter ratios (L/d) embedded in a sand calibrated chamber of known relative density. The study revealed that the shear strength parameters of the sand specimens and the (L/d) ratios are the most significant factor influencing the response of the pile and its capacity while taking into consideration the complex interaction between the pile and soil. Good agreement has been achieved when comparing the application of this modelling approach with experimental physical modelling carried out by another researcher.

Keywords: deep foundations, slenderness ratio, soil-pile interaction, winkler model (beam on elastic foundation), non-cohesive soil

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Authors: Edgar Teixeira, Eurico Carrapatoso

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As 3D displays become increasingly affordable, while production techniques and computational resources to create stereoscopic content being ever more accessible, a new dimension is literally introduced along with new expressive and immersive potentialities in support of designing for the screen. Prospective design visionaries have already at the reach of their hands an innovative and powerful visualization technology, which enables them to actively envision future trends and vanguardist directions. This paper explores the aesthetic and informational potentialities of stereoscopic motion graphics, providing insight on the application of 3D displays in design practice, proposing strategies to investigate stereoscopic communication, discussing potential repercussions to extant theory and impacts on audience.

Keywords: design, visual communication, technology, stereoscopy, 3D media

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Authors: Tao Song, Hao Cheng, Guangfeng Tian, Chuang Xu

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An autonomous emergency braking system is an advanced driving assistance system that enables vehicle collision avoidance and pedestrian collision avoidance to improve vehicle safety. At present, because the pedestrian target is small, and the mobility is large, the pedestrian AEB system is faced with more technical difficulties and higher functional requirements. In this paper, a method of pedestrian target selection based on a variable width funnel is proposed. Based on the current position and predicted position of pedestrians, the relative position of vehicle and pedestrian at the time of collision is calculated, and different braking strategies are adopted according to the hazard level of pedestrian collisions. In the CNCAP standard operating conditions, comparing the method of considering only the current position of pedestrians and the method of considering pedestrian prediction position, as well as the method based on fixed width funnel and variable width funnel, the results show that, based on variable width funnel, the choice of pedestrian target will be more accurate and the opportunity of the intervention of AEB system will be more reasonable by considering the predicted position of the pedestrian target and vehicle's lateral motion.

Keywords: automatic emergency braking system, pedestrian target selection, TTC, variable width funnel

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Authors: G .D. B. N. Kulasaooriya, H. B. S. Ariyarathne, I. Abeygunawardene, A. A. J. Rafarathne, B. V. Perera

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Elephant is the largest resident of the wild and has small surface to volume ratio as well as less number of sweat glands which cause challenges to the thermoregulation of this mammal. However, this megaherbivore has adopted specialised meachanisms to maintain its thermal balance through behavioral adaptations, ear flapping and well anastomosed arterioles and venules of the ear. Nevertheless, little is known on the involvement of the skin in the process of thermoregulation. The present study was undertaken to monitor the water evaporation rate from the skin of unrestrained wild elephant calves throughout the day and to understand its importance in the thermoregulation. Seven baby elephants housed in the elephant transit home, Udawalawe were used. Ambient temparature, relative humidity (RH) and radiation heat load was monitored throughout the day of the study period. Similarly, surface temparature of the skin was taken at six points including lateral ear pinna, lateral body and the rump during the same period. The skin water evaporation was also measured from the same sites using cobolt chloride method. The surface are of the skin was determined by assigning geometrical shapes to each body part. The results showed that the ambient temperature gradually increased with the day reaching maximum around 3.00 pm. The relative humidity was lowest early in the morning. The radiation heat load did not show any significant change in the study period. The skin temperature was different among lateral ear pinna, lateral body and the rump where the highest temperature was on the rump and the lowest on the lateral ear pinna. The skin temperature gradually increase with increasing ambient temperature but there was not a strong correlation (R2 =53.53) between these two. The skin temperature had strong correlation with RH (p<0.05 R2 =70.84% ) but a significant relationship was not considered since the radiation heat load was not varying in large scale. The skin evaporative water loss had a weak negative correlation with ambient temperature (correlation coefficient= -0.01) whereas strong positive correlation with RH (correlation coefficient= 25.275 ) and no corelation with radiation heat load. It also appeared that skin water loss increases as the skin temperature increased. In the present study, it was observed that on average, skin of the baby elephant looses 403 g/m2/h of water. Based on these observations it can be concluded that a large volume of water is evaporated from the skin of baby elephants and evaporative heat loss may be contributing significantly to the thermoregulation. However, further investigation on the influence of environmental factors on evaporative heat loss has to be conducted to understand the thermoregulatory mechanisms of the baby elephant.

Keywords: thermoregulation, behavioral adaptations, evaporation, elephant

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Authors: Qiang Zhang, Chun Yuan

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Since the PU (Prediction Unit) decision process is the most time consuming part of the emerging HEVC (High Efficient Video Coding) standardin intra and inter frame coding, this paper proposes the fast PU decision algorithm and speed up the algorithm using CUDA (Compute Unified Device Architecture). In intra frame coding, the fast PU decision algorithm uses the texture features to skip intra-frame prediction or terminal the intra-frame prediction for smaller PU size. In inter frame coding of HEVC, the fast PU decision algorithm takes use of the similarity of its own two Nx2N size PU's motion vectors and the hierarchical structure of CU (Coding Unit) partition to skip some modes of PU partition, so as to reduce the motion estimation times. The accelerate algorithm using CUDA is based on the fast PU decision algorithm which uses the GPU to make the motion search and the gradient computation could be parallel computed. The proposed algorithm achieves up to 57% time saving compared to the HM 10.0 with little rate-distortion losses (0.043dB drop and 1.82% bitrate increase on average).

Keywords: HEVC, PU decision, inter prediction, intra prediction, CUDA, parallel

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Authors: Ross Calvert, Colin Whittaker, Alison Raby, Alistair G. L. Borthwick, Ton S. van den Bremer

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Large concentrations of plastic have polluted the seas in the last half century, with harmful effects on marine wildlife and potentially to human health. Plastic pollution will have lasting effects because it is expected to take hundreds or thousands of years for plastic to decay in the ocean. The question arises how waves transport plastic in the ocean. The predominant motion induced by waves creates ellipsoid orbits. However, these orbits do not close, resulting in a drift. This is defined as Stokes drift. If a particle is infinitesimally small and the same density as water, it will behave exactly as the water does, i.e., as a purely Lagrangian tracer. However, as the particle grows in size or changes density, it will behave differently. The particle will then have its own inertia, the fluid will exert drag on the particle, because there is relative velocity, and it will rise or sink depending on the density and whether it is on the free surface. Previously, plastic pollution has all been considered to be purely Lagrangian. However, the steepness of waves in the ocean is small, normally about α = k₀a = 0.1 (where k₀ is the wavenumber and a is the wave amplitude), this means that the mean drift flows are of the order of ten times smaller than the oscillatory velocities (Stokes drift is proportional to steepness squared, whilst the oscillatory velocities are proportional to the steepness). Thus, the particle motion must have the forces of the full motion, oscillatory and mean flow, as well as a dynamic buoyancy term to account for the free surface, to determine whether inertia is important. To track the motion of a floating inertial particle under wave action requires the fluid velocities, which form the forcing, and the full equations of motion of a particle to be solved. Starting with the equation of motion of a sphere in unsteady flow with viscous drag. Terms can added then be added to the equation of motion to better model floating plastic: a dynamic buoyancy to model a particle floating on the free surface, quadratic drag for larger particles and a slope sliding term. Using perturbation methods to order the equation of motion into sequentially solvable parts allows a parametric equation for the transport of inertial finite-sized floating particles to be derived. This parametric equation can then be validated using numerical simulations of the equation of motion and flume experiments. This paper presents a parametric equation for the transport of inertial floating finite-size particles by ocean waves. The equation shows an increase in Stokes drift for larger, less dense particles. The equation has been validated using numerical solutions of the equation of motion and laboratory flume experiments. The difference in the particle transport equation and a purely Lagrangian tracer is illustrated using worlds maps of the induced transport. This parametric transport equation would allow ocean-scale numerical models to include inertial effects of floating plastic when predicting or tracing the transport of pollutants.

Keywords: perturbation methods, plastic pollution transport, Stokes drift, wave flume experiments, wave-induced mean flow

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Authors: Qazi Umer Jamil, Abubakr Siddique, Mubeen Ur Rehman, Nida Aziz, Mohsin I. Tiwana

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This paper discusses a brain controlled robotic gait trainer for neurorehabilitation of Spinal Cord Injury (SCI) patients. Patients suffering from Spinal Cord Injuries (SCI) become unable to execute motion control of their lower proximities due to degeneration of spinal cord neurons. The presented approach can help SCI patients in neuro-rehabilitation training by directly translating patient motor imagery into walkers motion commands and thus bypassing spinal cord neurons completely. A non-invasive EEG based brain-computer interface is used for capturing patient neural activity. For signal processing and classification, an open source software (OpenVibe) is used. Classifiers categorize the patient motor imagery (MI) into a specific set of commands that are further translated into walker motion commands. The robotic walker also employs fall detection for ensuring safety of patient during gait training and can act as a support for SCI patients. The gait trainer is tested with subjects, and satisfactory results were achieved.

Keywords: brain computer interface (BCI), gait trainer, spinal cord injury (SCI), neurorehabilitation

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Authors: Radoslaw Pytlak, Damian Suski

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The aim of the paper is to provide a computational tool for planning a haemodialysis process. It is shown that optimization methods can be used to obtain the most effective treatment focused on removing both urea and phosphorus during the process. In order to achieve that, the IV–compartment model of phosphorus kinetics is applied. This kinetics model takes into account a rebound phenomenon that can occur during haemodialysis and results in a hybrid model of the process. Furthermore, vector fields associated with the model equations are such that it is very likely that using the most intuitive objective functions in the planning problem could lead to solutions which include sliding motions. Therefore, building computational tools for solving the problem of planning a haemodialysis process has required constructing numerical algorithms for solving optimal control problems with hybrid systems. The paper concentrates on minimum time control of hybrid systems since this control objective is the most suitable for the haemodialysis process considered in the paper. The presented approach to optimal control problems with hybrid systems is different from the others in several aspects. First of all, it is assumed that a hybrid system can exhibit sliding modes. Secondly, the system’s motion on the switching surface is described by index 2 differential–algebraic equations, and that guarantees accurate tracking of the sliding motion surface. Thirdly, the gradients of the problem’s functionals are evaluated with the help of adjoint equations. The adjoint equations presented in the paper take into account sliding motion and exhibit jump conditions at transition times. The optimality conditions in the form of the weak maximum principle for optimal control problems with hybrid systems exhibiting sliding modes and with piecewise constant controls are stated. The presented sensitivity analysis can be used to construct globally convergent algorithms for solving considered problems. The paper presents numerical results of solving the haemodialysis planning problem.

Keywords: haemodialysis planning process, hybrid systems, optimal control, sliding motion

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Authors: Chadlia Ounissi, Maher Gzam, Tahani Hallek, Salah Mahmoudi, Mabrouk Montacer

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This work consists of a morphological study of the coastal domain at the central fringe of the Gulf of Gabes, Southeast of Tunisia, belonging to the structural domain of the maritime Jeffara. The diachronic study of tidal mouths in the study area and the observation of morphological markers revealed the existence of hydro-sedimentary processes leading to sedimentary accumulation and filling of the estuarine system. This filling process is materialized by the genesis of a sandy cord and the lateral migration of the tidal mouth. Moreover, we have been able to affirm, by the use of satellite images, that the dominant and responsible current at this particular coastal morphology is directed to the North, having constituted a controversy on the occurrence of what is previously mentioned in the literature. The speed of the lateral displacement of the channel varies as a function of the hydrodynamic forcing. Wave-dominated sites recorded the fastest speed (18 m/year) in the image of the mouth of Wadi el Melah. Tidal dominated sites in the Wadi Zerkine satellite image recorded a very low lateral migration (2 m / year). This variation in speed indicates that the intensity of the coastal current is uneven along the coast. This general pattern of hydrodynamic circulation, to the north, of the central fringe of the Gulf of Gabes, is disturbed by hydro-sedimentary cells.

Keywords: tidal mouth, direction of current, filling, sediment transport, Gulf of Gabes

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Authors: Praveen Battula

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Any high performance car has the tendency to over steer and Understeer under slippery conditions, An Electronic Stability Control System is needed under these conditions to regulate the steering of the car. It uses Anti-Lock Braking System (ABS) and Traction Control and Wheel Speed Sensor, Steering Angle Sensor, Rotational Speed Sensors to correct the problems. The focus of this paper is to improve the driving dynamics and safety by controlling the forces applied on each wheel. ESC Control the Yaw Stability, traction controls the Roll Stability, where actually the vehicle slip rate and lateral acceleration is controlled. ESC uses differential braking on all four brakes independently to control the vehicle’s motion. A mathematical model is developed in Simulink for the FlexRay based Electronic Stability Control. Vehicle steering is developed using Neuro Fuzzy Logic Controller. 7 Degrees of Freedom Vehicle Model is used as a Plant Model using dSpace autobox. The Performance of the system is assessed using two different road Scenarios, Vehicle Control under standard maneuvering conditions. The entire system is set using Dspace Control Desk. Results are provided by comparison of how a Vehicle with and without Electronic Stability Control which shows an improved performance in control.

Keywords: ESC, flexray, chassis control, steering, neuro fuzzy, vehicle dynamics

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Authors: Sangbaek Park, Seungju Lee, Soo-Won Chae

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Unstable shoes are known to strengthen lower extremity muscles and improve gait ability and to change the user’s gait pattern. The change in gait pattern affects human body enormously because the walking is repetitive and steady locomotion in daily life. It is possible to estimate the joint motion including joint moment, force and inertia effect using kinematic and kinetic analysis. However, the change of internal stress at the articular cartilage has not been possible to estimate. The purpose of this research is to evaluate the internal stress of human body during gait with unstable shoes. In this study, FE analysis was combined with motion capture experiment to obtain the boundary condition and loading condition during walking. Motion capture experiments were performed with a participant during walking with normal shoes and with unstable shoes. Inverse kinematics and inverse kinetic analysis was performed with OpenSim. The joint angle and muscle forces were estimated as results of inverse kinematics and kinetics analysis. A detailed finite element (FE) lower extremity model was constructed. The joint coordinate system was added to the FE model and the joint coordinate system was coincided with OpenSim model’s coordinate system. Finally, the joint angles at each phase of gait were used to transform the FE model’s posture according to actual posture from motion capture. The FE model was transformed into the postures of three major phases (1st peak of ground reaction force, mid stance and 2nd peak of ground reaction force). The direction and magnitude of muscle force were estimated by OpenSim and were applied to the FE model’s attachment point of each muscle. Then FE analysis was performed to compare the stress at knee cartilage during gait with normal shoes and unstable shoes.

Keywords: finite element analysis, gait analysis, human model, motion capture

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Authors: Ossama Salman

Abstract:

Background and objective: Sacroiliac joint pain is a common cause for chronic axial low back pain, with up to 20% prevalence rate. To date, no effective long-term treatment intervention has been embarked on yet. The aim of our study was to compare steroid block to radiofrequency ablation for SIJ pain conditions. Methods: A randomized, blind, study was conducted in 30 patients with sacroiliac joint pain. Fifteen patients received radiofrequency denervation of L4-5 primary dorsal rami and S1-3 lateral sacral branch, and 15 patients received steroid under fluoroscopy. Those in the steroid group who did not respond to steroid injections were offered to cross over to get radiofrequency ablation. Results: At 1-, 3- and 6-months post-intervention, 73%, 60% and 53% of patients, respectively, gained ≥ 50 % pain relief in the radiofrequency (RF) ablation group. In the steroid group, at one month post intervention follow up, only 20% gained ≥ 50 % pain relief, but failed to show any improvement at 3 months and 6 months follow up. Conclusions: Radiofrequency ablation at L4 and L5 primary dorsal rami and S1-3 lateral sacral branch may provide effective and longer pain relief compared to the classic intra-articular steroid injection, in properly selected patients with suspected sacroiliac joint pain. Larger studies are called for to confirm our results and lay out the optimal patient selection and treatment parameters for this poorly comprehended disorder.

Keywords: lateral branch denervation, LBD, radio frequency, RF, sacroiliac joint, SIJ, visual analogue scale, VAS

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Authors: Chung-Chun Hsiao, Yu-Kai, Ting, Kai-Yuan Liu, Pang-Wei Yen, Jia-Ying Tu

Abstract:

In this paper, a new design of spherical robotic system based on the concepts of gimbal structure and gyro dynamics is presented. Robots equipped with multiple wheels and complex steering mechanics may increase the weight and degrade the energy transmission efficiency. In addition, the wheeled and legged robots are relatively vulnerable to lateral impact and lack of lateral mobility. Therefore, the proposed robotic design uses a spherical shell as the main body for ground locomotion, instead of using wheel devices. Three spherical shells are structured in a similar way to a gimbal device and rotate like a gyro system. The design and mechanism of the proposed robotic system is introduced. In addition, preliminary results of the dynamic model based on the principles of planar rigid body kinematics and Lagrangian equation are included. Simulation results and rig construction are presented to verify the concepts.

Keywords: gyro, gimbal, lagrange equation, spherical robots

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Authors: O. Punjarat, S. Chucheepsakul, T. Phanyasahachart

Abstract:

This paper focuses on a variational formulation of large amplitude free vibration behavior of a very sag marine cable. In the static equilibrium state, the marine cable has a very large sag configuration. In the motion state, the marine cable is assumed to vibrate in in-plane motion with large amplitude from the static equilibrium position. The total virtual work-energy of the marine cable at the dynamic state is formulated which involves the virtual strain energy due to axial deformation, the virtual work done by effective weight, and the inertia forces. The equations of motion for the large amplitude free vibration of marine cable are obtained by taking into account the difference between the Euler’s equation in the static state and the displaced state. Based on the Galerkin finite element procedure, the linear and nonlinear stiffness matrices, and mass matrices of the marine cable are obtained and the eigenvalue problem is solved. The natural frequency spectrum and the large amplitude free vibration behavior of marine cable are presented.

Keywords: axial deformation, free vibration, Galerkin finite element method, large amplitude, variational method

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Authors: Y. Johnson

Abstract:

Study of multi-satellite formation flight systems has drawn wide attention recently due to so many potential advantages. The present work aims to model the relative motion dynamics in terms of change in classical orbital parameters between the two satellites-chief and deputy- under Earth’s oblateness effect. The required impulsive thrust control is calculated to minimize these orbital parameter changes. The formation configuration is initialized by selecting a set of orbital parameters for the chief and deputy satellites such that bounded motion is maintained for a long time in a J_2-invariant relative non-circular orbit between the satellites. The solution of J_2-modified Hill’s equations is also derived in this paper.

Keywords: satellite, formation flight, j2 effect, control

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Authors: Wei Liu, Shuquan Wang, Yang Gao

Abstract:

Microgravity Science Experiment Rack (MSER) will be onboard TianHe (TH) spacecraft planned to be launched in 2018. TH is one module of Chinese Space Station. Microgravity Vibration Isolation System (MVIS), which is MSER’s core part, is used to isolate disturbance from TH and provide high-level microgravity for science experiment payload. MVIS is two stage vibration isolation system, consisting of Follow Unit (FU) and Experiment Support Unit (ESU). FU is linked to MSER by umbilical cables, and ESU suspends within FU and without physical connection. The FU’s position and attitude relative to TH is measured by binocular vision measuring system, and the acceleration and angular velocity is measured by accelerometers and gyroscopes. Air-jet thrusters are used to generate force and moment to control FU’s motion. Measurement module on ESU contains a set of Position-Sense-Detectors (PSD) sensing the ESU’s position and attitude relative to FU, accelerometers and gyroscopes sensing ESU’s acceleration and angular velocity. Electro-magnetic actuators are used to control ESU’s motion. Firstly, the linearized equations of FU’s motion relative to TH and ESU’s motion relative to FU are derived, laying the foundation for control system design and simulation analysis. Subsequently, two control schemes are proposed. One control scheme is that ESU tracks FU and FU tracks TH, shorten as E-F-T. The other one is that FU tracks ESU and ESU tracks TH, shorten as F-E-T. In addition, motion spaces are constrained within ±15 mm、±2° between FU and ESU, and within ±300 mm between FU and TH or between ESU and TH. A Proportional-Integrate-Differentiate (PID) controller is designed to control FU’s position and attitude. ESU’s controller includes an acceleration feedback loop and a relative position feedback loop. A Proportional-Integrate (PI) controller is designed in the acceleration feedback loop to reduce the ESU’s acceleration level, and a PID controller in the relative position feedback loop is used to avoid collision. Finally, simulations of E-F-T and F-E-T are performed considering variety uncertainties, disturbances and motion space constrains. The simulation results of E-T-H showed that control performance was from 0 to -20 dB for vibration frequency from 0.01 to 0.1 Hz, and vibration was attenuated 40 dB per ten octave above 0.1Hz. The simulation results of T-E-H showed that vibration was attenuated 20 dB per ten octave at the beginning of 0.01Hz.

Keywords: microgravity science experiment rack, microgravity vibration isolation system, PID control, vibration isolation performance

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Authors: Ophir Segal, Daniel Weltsch, Shay Tenenbaum, Ran Thein

Abstract:

Purpose: Patients with lateral patellar dislocation (LPD) are not always referred to perform an MRI. This might be the case in first time LPD patients without surgical indications or in patients with recurrent LPD who had MRI in previous episodes. Unfortunately, in some cases, there are additional knee pathological findings, which include tearing of the collateral or cruciate ligaments and injury to the tendons or menisci. These findings might be overlooked during the physical examination or masked by nonspecific clinical findings like knee pain, effusion, or hemarthrosis. The prevalence of these findings, which can be revealed by MRI, is misreported in literature and is considered rare. In our practice, all patients with LPD are sent for MRI after LPD. Therefore, we have designed a retrospective comparative study to evaluate the prevalence of additional pathological findings in patients with acute traumatic LPD that had performed MRI, comparing different groups of patients according to age, sex, and Tibial Tuberosity-Trochlear Groove(TT-TG) distance. Methods: MRI of the knee in patients after traumatic LPD were evaluated for the presence of additional pathological findings such as injuries to ligaments: Anterior/Posterior cruciate ligament(ACL, PCL), Medial/Lateral collateral ligament(MCL, LCL), injuries to tendons(QUADICEPS, PATELLAR), menisci(Medial/Lateral meniscus(MM, LM)) and tibial plateau, by a fellowship-trained, senior musculoskeletal radiologist. A comparison between different groups of patients was performed according to age (age group < 25 years, age group > 25 years), sex (Male/Female group), and TT-TG distance (TT-TG<15 groups, TT-TG>15 groups). A descriptive and comparative statistical analysis was performed. Results: 150 patients were included in this study. All suffered from LPD between the years 2012-2017 (mean age 21.3( ± SD 8.9), 86 males). ACL, PCL, MCL, and LCL complete or partial tears were found in 17(11.3%), 3(2%), 22(14.6%), and 4(2.7%) of the patients, respectively. MM and LM tears were found in 10(6.7%) and 3(2%) of the patients, respectively. A higher prevalence of PCL injury, MM tear, and LM tear were found in the older age group compared to the younger group of patients (10.5% vs. 1.8%, 18.4% vs. 2.7%, and 7.9% vs. 0%, respectively, p<0.05). A higher prevalence of non-displaced MM tear and LCL injury was found in the male group compared to the female group (8.1% vs. 0% and 8.1% vs. 0% respectively, p<0.05). A higher prevalence of ACL injury was found in the normal TT-TG group compared to the pathologic TT-TG group (17.5% vs. 2.3%, p= 0.0184). Conclusions: Overall, 43 out of 150 (28.7%) of the patient's MRI’s were positive for additional pathological radiological findings. Interestingly, a higher prevalence of additional pathologies was found in the groups of patients with a lower risk for recurrent LPD, including males, patients older than 25, and patients with TT-TG lower than 15mm, and therefore might not be referred for an MRI scan. Thus, we recommend a strict physical examination, awareness to the high prevalence of additional pathological findings, and to consider performing an MRI in all patients after LPD.

Keywords: additional findings, lateral patellar dislocation (LPD), MRI scan, traumatic patellar dislocation, cruciate ligaments injuries, menisci injuries, collateral ligaments injuries

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