Development and global validation of a 1-week-old piglet head finite element model for impact simulations / 中华创伤杂志(英文版)

PURPOSE@#Child head injury under impact scenarios (e.g. falls, vehicle crashes, etc.) is an important topic in the field of injury biomechanics. The head of piglet was commonly used as the surrogate to investigate the biomechanical response and mechanisms of pediatric head injuries because of the similar cellular structures and material properties. However, up to date, piglet head models with accurate geometry and material properties, which have been validated by impact experiments, are seldom. We aim to develop such a model for future research.@*METHODS@#In this study, first, the detailed anatomical structures of the piglet head, including the skull, suture, brain, pia mater, dura mater, cerebrospinal fluid, scalp and soft tissue, were constructed based on CT scans. Then, a structured butterfly method was adopted to mesh the complex geometries of the piglet head to generate high-quality elements and each component was assigned corresponding constitutive material models. Finally, the guided drop tower tests were conducted and the force-time histories were ectracted to validate the piglet head finite element model.@*RESULTS@#Simulations were conducted on the developed finite element model under impact conditions and the simulation results were compared with the experimental data from the guided drop tower tests and the published literature. The average peak force and duration of the guide drop tower test were similar to that of the simulation, with an error below 10%. The inaccuracy was below 20%. The average peak force and duration reported in the literature were comparable to those of the simulation, with the exception of the duration for an impact energy of 11 J. The results showed that the model was capable to capture the response of the pig head.@*CONCLUSION@#This study can provide an effective tool for investigating child head injury mechanisms and protection strategies under impact loading conditions.

Dynamic Response and Damage Analysis of Human Head and Neck in Automobile Rear Impact / 医用生物力学

Objective To establish the precise finite element model of the head and neck based on human anatomical structure, so as to study neck injuries caused by rear impact at different speeds. Methods The model was based on CT scan images of the head and neck of human body. The Mimics software was used to reconstruct the three-dimensional (3D) bone, and the 3D solid ligaments, small joints and other tissues of the neck were improved and meshed by HyperMesh. The generated models included the head, 8 vertebrae (C1-T1), 6 intervertebral discs (annulus, nucleus pulposus and upper and lower cartilage endplates), facet joints (cartilage and joint capsule ligaments), ligaments, muscles, etc. Finally, the model verification and post-collision calculation were completed in the finite element post-processing software. Results The simulation results of the models under axial impact, front and back flexion and lateral flexion were compared with the experimental data to verify the effectiveness of the model. Then post-collision simulation at the speed of 20, 40, 60 and 80 km/h was conducted. At the speed of 20 km/h, there was no damage to the neck. At the speed of 40, 60 and 80 km/h, the ligament was the first to be damaged. As the speed increased, the stress on tissues of the neck increased continuously. At the speed of 80 km/h, the maximum stresses of the dense bone, cancellous bone and annulus of the cervical vertebrae were 226.4, 11.5, and 162.8 MPa, respectively. When the ligament strain reached the limit, tearing began to occur. Conclusions The finite element model of the head and neck established in this study has high bionics and effectiveness, and can be used for studying neck injury analysis in traffic accidents, which is helpful for the diagnosis, treatment and prevention of cervical spine injury to a certain extent.

A design of raster plot for illustrating dynamic neuronal activity during deep brain stimulation / 生物医学工程学杂志

Deep brain stimulation (DBS), which usually utilizes high frequency stimulation (HFS) of electrical pulses, is effective for treating many brain disorders in clinic. Studying the dynamic response of downstream neurons to HFS and its time relationship with stimulus pulses can reveal important mechanisms of DBS and advance the development of new stimulation modes (e.g., closed-loop DBS). To exhibit the dynamic neuronal firing and its relationship with stimuli, we designed a two-dimensional raster plot to visualize neuronal activity during HFS (especially in the initial stage of HFS). Additionally, the influence of plot resolution on the visualization effect was investigated. The method was then validated by investigating the neuronal responses to the axonal HFS in the hippocampal CA1 region of rats. Results show that the new design of raster plot is able to illustrate the dynamics of indexes (such as phase-locked relationship and latency) of single unit activity (i.e., spikes) during periodic pulse stimulations. Furthermore, the plots can intuitively show changes of neuronal firing from the baseline before stimulation to the onset dynamics during stimulation, as well as other information including the silent period of spikes immediately following the end of HFS. In addition, by adjusting resolution, the raster plot can be adapted to a large range of firing rates for clear illustration of neuronal activity. The new raster plot can illustrate more information with a clearer image than a regular raster plot, and thereby provides a useful tool for studying neuronal behaviors during high-frequency stimulations in brain.

Feedback of Dynamic Responses from the Middle Ear for Round Window Closure with Different Pathology / 医用生物力学

Objective To analyze the influence of round window lesion on dynamic responses from the middle ear. Methods Based on CT scan images of healthy human ear, the three-dimensional finite element model of human ear was rebuilt by PATRAN software, then NASTRAN software was applied to conduct coupled solid-fluid frequency response analysis. The feedback of round window lesion on dynamic response of the middle ear was investigated by numerical simulation. Results Round window closure caused by sclerosis led to more decline in amplitude of stapes than congenital round window closed, maximally can reach 30.2 dB, and the latter had no obvious influence on velocity of stapes. In term of phase angle, on condition of sclerosis, change of phase for stapes and round window reached 90° at most and kept a difference value of 180°. In contrast, on condition of congenital round window closed, change of phase for stapes reached 270° at most，meanwhile change of phase for round window disappeared. Conclusions The dynamic response of the middle ear showed different feedback to congenital and otosclerotic round window fixation based on amplitude, velocity and phase. The research findings provide the theoretical basis for diagnosing and fixing round window lesion in future.

Inverse dynamics simulation on lower limb responses of badminton athlete under impact loads / 医用生物力学

Objective To analyze the badminton athletes’dynamic responses in their lower limbs under impact loads. Methods A human musculoskeletal model was established based on AnyBody Modeling System software and verified by measuring surface electromyography (EMG). The muscle force, joint force, joint torque of lower limbs during right Front-Court Lunge Step in badminton were studied by inverse dynamic simulation and analysis through Vicon motion capture system and force platform. Results The musculoskeletal model was validated to be effective by EMG. During right Front-Court Lunge Step in badminton，the force peak of the hip and ankle joint in Z direction was larger than that in X and Y direction, and the force peak of the knee joint in X direction was larger than that in Y and Z direction. During buffer period, the hip joint in X, Y, Z direction showed adduction, extension and internal rotation torque, respectively, the knee joint in X, Y, Z direction showed abduction, flexion and external rotation torque, respectively, and the ankle joint in X, Y direction showed varus and plantar flexion torque, respectively. The peak torque of the hip, knee and ankle joint in X direction was significantly larger than that in Y and Z direction. Vastus lateralis, biceps femoris, anterior tibial and medial gastrocnemius played a larger role against the ground reaction, while rectus femoris, semitendinosus, soleus played a relatively smaller role against the ground reaction. Conclusions The established musculoskeletal model in the study can provide a technical platform to analyze athletes’biomechanical properties of lower limbs under impact loads. To avoid sport injuries, more attention should be paid to the effect from ground reaction force load at touchdown instant on hip, knee and ankle joints in anteroposterior and mediolateral direction during footwork similar to Front-Court Lunge Step in badminton, and at the same time, the strength training of vastus lateralis, biceps femoris, anterior tibial and medial gastrocnemius of badminton players should not be ignored during specialized training.

Head dynamic response based on reconstruction of vehicle-pedestrian accidents with the video / 医用生物力学

Objective To study the relationship between the severity of pedestrian head injury and the impact speeds, the vehicle types and the impact positions in pedestrian-vehicle accidents by computer simulation based on the real accident video. Methods A pedestrian-traffic accident with the video was reconstructed by the MADYMO multi-body dynamics software to obtain the initial and boundary conditions. Experimental impact simulations were conducted on different vehicles (car, SUV and minibus) and pedestrian impact positions (front, side and back structure) by different speeds (20, 30, 40, 50 and 60 km/h) to analyze head injuries, and the simulation results were validated by two real pedestrian-vehicle accidents. Results Not only the impact speed and the front structure influenced the pedestrian head injury severity, but also the impact position of pedestrian was an important factor. At the collision speed ≤30 km/h, the pedestrian head injury caused by the contact with the ground could be possibly more serious than the contact with the vehicle; while at the collision speed≥40 km/h, the pedestrian head injury was mainly caused by the contact with the vehicle. Conclusions The pedestrian traffic accident can be accurately reconstructed by using the real accident video to analyze the pedestrian head dynamic response. The severity of pedestrian head injuries can be effectively reduced by speed limitations on different types of vehicles at pedestrian traffic accident black-spots.

Effects from different head models on dynamic response of the head impact using material point method / 医用生物力学

Objective To investigate the effects of muscles and boundary conditions on head impact response. Methods Three different 3D material point impact models of human head were constructed from the CT scanned images. The first model was the simple head model (SHFr) including skull, membrane and brain, in which the head was free. The second model was the simple head model with muscle (MHFr) including skull, membrane, brain and muscle of the head, in which the head was free. The third model was the MHFr model with shoulder, in which the bottom edge of the shoulder was fixed (MHSFi). The three models were under the impact of a cylindrical lead hammer projected at a speed of 6.4 m/s to simulate the dynamic response of the three models using 3D explicit material point method code. Results The peak values of acceleration of the head centroid for the SHFr, MHFr and MHSFi model were 6.018×103, 4.69×103 and 4.76×103 m/s2, respectively. Conclusions The muscle of the head can disperse distributions of the contact force, enlarge the damage area and relieve the damage of the head. In case of short-time impact, whether the boundary of the head is free or the shoulder is fixed does not affect the dynamic response of the head impact.

Dynamic responses of head-neck complex in pilots during arrested deck landing / 医用生物力学

Objective To analyze the dynamic response and strain of the major muscles in head-neck complex of pilot with or without wearing the helmet during carrier aircraft arrested deck landing. Methods Ten-rigid body dynamic model of human head-neck complex was created including head, seven cervical vertebrae and two thoracic vertebrae; mechanical properties of the ligaments, intervertebral discs and other surrounding soft tissues were described by lumped parameter method; mechanical properties of the 15 pairs of muscles in this human head-neck complex were represented by non-linear stress-strain relationship. The model was validated by using experimental data of dynamic responses from the human head-neck complex in a set of different types of automobile crashes. Results The overload curve and strain of this 15 pairs of muscles in head-neck complex of the pilot during arrested deck landing were obtained. The results showed that the extension of splenius cervicis was the largest. The strain of splenius cervicis could reach 50% when the pilot wore the helmet, and it could reach as high as 56% if the helmet’s weight was 2.7 kg. Conclusions Wearing helmet would extend the stretch of neck muscles, and the simulation result could be used for further evaluation on head/neck injury of the pilot.

Effect of different connecting methods for artificial ossicle on dynamic response of ear / 医用生物力学

Objective To study the effects of the different connecting mode of artificial ossicle on hearing restoration. Method Geometrical model of human ear was established by an original C++ program based on clinical CT data, and imported this geometrical model into finite element software PATRAN to build up the numerical finite element model of human ear structure. Based on the finite element model, the fluid solid coupling was computed by harmonic response analysis method, and the effect of sound conduction on ear structure was analyzed according to different implantable methods and positions of artificial ossicle. Results The validity of this numerical model is confirmed by comparing the amplitude of umbo and stapes footplate on numerical model which is gained by dynamic response analysis on normal ear structure with published experimental measurements on human temporal bones. ConclusionsConnecting artificial ossicle to tympanic membrane at its central position is optimal for the dynamic response of ear structure as the amplitude of stapes footplate under this situation is slightly higher than other connecting methods since it conforms to physiological function of human ear, and the effect of hearing recovery could be better.

Simple procedure for evaluation of the frequency response of flow transducers used in spirometry / Procedimento simples para avaliação da resposta em frequência de transdutores de vazão usados em espirometria

In this research, we present a simple mechanical assembly for evaluation of frequency response of flow transducers. Also, two pneumotachometer/pressure transducer (PPT) ensembles were evaluated with this setup. The accuracy of the measurements depended mainly on the physical dimensions of a piston, without need for a closed-loop control for the generated flow, which would demand a pre-calibrated electronic pressure transducer or an optical position detection device. The gain and phase curves found for both evaluatedPPTs are presented. We conclude that the presented mechanism is suitable to evaluate the dynamic response of these PPTs in the range between 1.0 and 50.0  Hz. Regarding the evaluated PPTs, we concluded that the gain curves in the whole dynamic range of both assemblies were 0 and +2.63  dB for PPT assembly 1, and 0 and +6.70  dB for PPT assembly 2.

Este trabalho apresenta um sistema mecânico simples para levantamentoda resposta em freqüência de transdutores de vazão de gás. Dois conjuntos de pneumotacômetro/transdutor de pressão (PPT) foram avaliados com este sistema. A exatidão das medidas dependeu principalmente das dimensões de um pistão, sem a necessidade de controle com malha fechada da vazão gerada, o que demandaria o uso de um transdutor de pressão eletrônico pré-calibrado ou um dispositivo óptico para detecção de posição. As curvas de ganho e defasagem dos dois conjuntos PPT avaliados são apresentadas. É possível concluir que o mecanismo apresentado é capaz de avaliar a resposta dinâmica destes PPTs na faixa de 1,0 a 50,0  Hz. Em relação à avaliação dos PPTs, concluiu-se que as curvas de ganho em toda a faixa dinâmica avaliada em ambos PPTs ficaram entre 0 e +2,63  dB para o conjunto PPT 1 e entre 0 e +6,70  dB para o conjunto PPT 2.

Spectral analysis of respiratory flow and gas concentrations / Análise espectral de fluxo e concentrações de gases respiratórios

In this research we obtained samples of human respiratory flow, oxygen concentration and carbon dioxide concentration signals from 20 healthy subjects and evaluated the average power spectral density (PSD) of these signals. For each subject,the respiratory samples were acquired in four progressive levels of exercise in a cycle ergometer. Auto regressive moving average models were designed to represent the PSD found in each phase. An average PSD of the four levels was also calculated. Results have shown that the bandwidth of O2 concentration, CO2 concentration and flow signals was 8  Hz, 7 Hz, and 15  Hz, respectively, within the dynamic range of 50  dB. The PSD curves found can be used for optimal filter design for signal enhancing in fast on-line measurement of these signals.

Nesta pesquisa foram registradas amostras dos sinais respiratórios de fluxo, concentração de oxigênio e concentração de gás carbônico em 20 voluntários saudáveis. A densidade espectral de potência (DEP) média foi então calculada. Para cada voluntário, as amostras dos sinais foram registradas em quatro intensidades progressivas de esforço físico em uma bicicleta ergométrica. Para representar a DEP encontrada em cada fase foram ajustados modelos auto-regressivos de média móvel. Uma DEP média entre as quatro intensidades também é fornecida. Os resultados mostraram que as larguras de banda dos sinais de concentração de O2, concentração de CO2 e fluxo foram 8  Hz, 7  Hz e 15  Hz, respectivamente, dentro de uma faixa dinâmica de 50  dB. As curvas de DEP encontradas podem ser usadas em projetos de filtros ótimos para equalização destes sinais em medições em tempo real.

INVESTIGATION ON THE DYNAMIC RESPONSE PERFORMANCE OF A NOVEL THREE-WAY SOLENOID VALVE / 药物分析学报

Objective A novel high-speed three-way solenoid valve is developed, which is used for the common-rail injection system equipped on DME powered engine. In order to improve the dynamic response performance of the three-way solenoid. Methods Experimental studies have been conducted to investigate the effects of spool stroke, drive voltage, negative demagnetizing pulse and two drive schemes on the dynamic response performance of the three-way solenoid valve. Results The results show that the dynamic response performance of the three-way solenoid valve can be remarkably improved by shortening the spool stroke and increasing the drive voltage. Simultaneously, the difference between the response time of closing valve and that of opening valve decreases. At each different drive voltage, there exists an optimal negative demagnetizing pulse corresponding to the same positive exciting pulse. At this optimal pulse,the dynamic response performance of the three-way solenoid valve is the best. In addition, the high drive voltage can lead to the smaller optimal negative demagnetizing pulse. It is also indicated from the experiments that the dynamic response performance of the three-way solenoid valve is better when the NO. 1 drive scheme is adopted. The lower drive voltage results in the larger difference between the dynamic response performances for the two drive schemes.Conclusion The dynamic response performance of a novel three-way solenoid valve is good.