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In this paper, a common energy harvester is investigated which uses a specimen of magnetic shape memory alloy (MSMA). The aim of this study is to improve system performance and to evaluate the magneto-mechanical loading on the MSMA material. Since demagnetization effect is not included in the employed original MSMA model, a method to incorporate this effect is proposed which has a good performance for the specific magneto-mechanical loading of this problem. In order to decrease the need for bias magnetic field and increase system efficiency, a new return mechanism for the MSMA specimen is proposed. The results indicate that the maximum harvested power from the improved system is obtained at 0.55 T bias field, with 30% increase in power. Then, input mechanical loading in the system is studied. Firstly, applied strain rate caused by mechanical loading is studied, and a nonlinear relation between the induced RMS voltage and strain rate is observed. Next, 2D applied mechanical loading is investigated, and it is shown that by increasing the phase difference between mechanical loads in two directions, the induced voltage decreases. Moreover, applying dynamic effect to the model shows that for thin MSMA specimens, this effect is minor, but by increasing the thickness and loading frequency, the effect becomes tangible.

Central nervous system (CNS) uses vision, vestibular, and somatosensory information to maintain body stability. Research has shown that there is more lumbar proprioception error among low back pain (LBP) individuals as compared to healthy people. In this study, two groups of 20 healthy people and 20 non-specific low back pain participants (LBP) took part in this investigation. This investigation focused on somatosensory sensors and in order to alter proprioception, a vibrator (frequency of 70Hz, amplitude of 0.5 mm) was placed on the soleus muscle area of each leg and two vibrators were placed bilaterally across the lower back muscles. Individuals, whose vision was occluded, were placed on two surfaces (foam and rigid) on force plate, and trunk angles were recorded simultaneously. Tests were performed in 8 separate trials; the independent variables were vibration (4 levels) and surface (2 levels) for within subjects and 2 groups (healthy and LBP) for between subjects (4×2×2). MANOVA and multi-factor ANOVA tests were done. Linear parameters for center of pressure (COP) (deviation of amplitude, deviation of velocity, phase plane portrait (PPP), and overall mean velocity) and nonlinear parameters for COP and trunk angle ((recurrence quantification analysis) RQA and Lyapunov exponents) were chosen as dependent variables. Results indicated that NSLBP individuals relied more on ankle proprioception for postural stability. Similarly, RQA parameters for the COP on both sides and for the trunk sagittal angle indicated more repeated patterns of movement among the LBP cohort. Analysis of short and long Lyapunov exponents showed that people with LBP caused no use of all joints in their bodies (non-flexible), are less stable than healthy subjects.

Magnetic shape memory alloys (MSMAs) are a kind of smart materials which are of great importance due to some unmatched behaviors when subjected to a mechanical loading or a magnetic field. In this work, energy harvesting from an MSMA specimen is studied. The MSMA specimen is embedded in a common magnetic circuit in this field of research and by applying mechanical loading, its effect on the specimen magnetic characteristics and induced voltage is investigated. Mechanical loading is applied in the form of strain-input and three kinds of 2D loadings are used including sinusoidal-sinusoidal, sinusoidal-triangular and triangular-triangular. It is demonstrated that the highest voltage is obtained in sinusoidal-sinusoidal loading and there is a negative correlation between the phase difference of the applied loadings in two directions and output voltage.

Traumatic brain injury (TBI) has long been known as one of the most anonymous reasons for death around the world. This phenomenon has been under study for many years and yet it remains a question due to physiological, geometrical and computational complexity. Although the modeling facilities for soft tissue have improved, the precise CT-imaging of human head has revealed novel details of the brain, skull and meninges. In this study a 3D human head including the brain, skull, and meninges is modeled using CT-scan and MRI data of a 30-year old human. This model is named “Sharif University of Technology Head Trauma Model (SUTHTM)”. By validating SUTHTM, the model is then used to study the effect of +Gz acceleration on the human brain. Damage threshold based on loss of consciousness in terms of acceleration and time duration is developed using Maximum Brain Pressure criteria. Results revealed that the Max. Brain Pressure ≥3.1 are representation of loss of consciousness. 3D domains for the loss of consciousness are based on Max. Brain Pressure is developed.Copyright © 2016 by ASME

The biomechanical behavior of brain tissue is needed for predicting the traumatic brain injury (TBI). Each year over 1.5 million people sustain a TBI in the United States. The appropriate coefficients for modeling the injury prediction can be evaluated using experimental data. In the present paper, using an experimental setup on bovine brain tissue, unconfined compression tests at quasi-static strain rates of ε. = 0.0004s−1, 0.008s−1 and 0.4s−1 combined with a stress relaxation test under unconfined uniaxial compression with ε. = 0.67s−1 ramp rate are performed. The fitted visco-hyperelastic parameters were utilized by using obtained stress-strain curves. The finite element analysis (FEA) is validated using experimental data.

A single-degree-of-freedom model is considered for flexible exercise bars based on the lumped-element approach. By considering the side segment of a flexible bar as a cantilever beam with an equivalent mass at the free end, its free-vibration response, as well as the forced response under the excitation of the grip, are expressed parametrically. Experiments are performed on a particular flexible bar (FLEXI_BAR) in order to obtain numerical values for quantifying the model's parameters. The model is also computationally simulated to study the response of the flexible bar to various excitations. The results are imported into a multi-segment musculoskeletal software (AnyBody), where the effect of different initial hand positions on the lumbar disc and back muscle forces is investigated (including Longissimus, Iliocostalis, and Transversus) during up-down exercises. The results show that all intervertebral discs and muscles forces are more sensitive to the horizontal position of the bar as compared to its vertical position.

In this paper a complete design of a high speed optical motion analyzer system has been described. The main core of the image processing unit has been implemented by the differential algorithm procedure. Some intelligent and conservative procedures that facilitate the search algorithm have also been proposed and implemented for the processing of human motions. Moreover, an optimized modified direct linear transformation (MDLT) method has been used to reconstruct 3D markers positions which are used for deriving kinematic characteristics of the motion. Consequently, a set of complete tests using some simple mechanical devices were conducted to verify the system outputs. Considering the system verification for human motion analysis, we used the system for gait analysis and the results including joint angles showed good compatibility with other investigations. Furthermore, a sport application example of the system has been quantitatively presented and discussed for Iranian National Karate-kas. The low computational cost, the high precision in detecting and reconstructing marker position with 2.39 mm error, and the capability of capturing from any number of cameras to increase the domain of operation of the subject, has made the proposed method a reliable approach for real-time human motion analysis. No special environment limitation, portability, low cost hardware and built in units for simulations and kinematic analysis are the other significant specifications of this system.

Responses of human body were studied in two adult age groups. The healthy subjects with no records of falling down or occupation in a crowded and noisy environment were elected. Mean age was 24 and 71 yrs. in young and elderly groups, respectively. Four experimental tasks were presented to subjects. Two involving flat standing with open and closed eyes and two were involving imposed disturbances. Two optoelectronic camera systems were used to measure body motion. The extents of postural sway were determined by processing the recorded data from force plate. The results were compared, and also provided the basis for kinematics analysis of body segments. For dynamic analysis, we used 3-link biomechanical model on a stationary triangular foot. Results from dynamic analysis indicated that, (a) The angular displacement of body segments was larger in elderly group, especially at the trunk; (b) The visual system had a dramatic effect on balance control, and its omission along with onset of senescence, has progressive effect, i.e. increased the amplitude and frequency of body sway, up to 2.4 and 1.5 times, respectively; (c) It has been proved that, in response to sudden stimulation, body employs certain strategy for muscle contraction. “Maximum torque, occurs in ankle, and respectively diminishes in joints, on its course toward upper segments”. The point is well consistent with the literature in this contest.

Wearable system is a proper solution for rehabilitation and instrumentation applications for human daily activities. Recently, several researches are concentrated on this technology significantly because of new progress in sensors and fusion sensors. In the near future, wearable and ambulatory devices will be used considerably in biomedical applications. In this study, we reviewed some methods about wearable measuring system then introduced and designed innovative wearable clothing for this purpose. Some specifications and advantages of our system in comparison with relevant researches are; using painted sensors that are manufactured through nano electro active polymer technology, low weight, low price, applicable for daily activity, three dimensional detection of human body movements and noninvasive. We utilized textile sensor to measure the trunk movements in three dimensions. Twenty textile sensors were attached on the clothing in this version of system. In addition to wearable system, clothing was prepared in order to determine the positions of textile sensors on the body. Furthermore, an electronic board is developed for data acquisition and transfer data to computer real-time. Finally, the wearable clothing for ambulatory purposes was manufactured and also different methods for the system calibration have been presented.

We proposed a model to investigate the transient diffusion of drug (sulphate) into the intervertebral disc. Using finite element method, drug diffusion was simulated and the concentration of diffused drug in each region of disc including Nucleus pulpous (NP), Inner annulus fibroses (IA), and Outer annulus fibroses (OA) was measured. In addition, to investigate the role of CEP permeability on the amount of diffused drug, model was simulated with different cartilage endplate (CEP) permeability. Having obtained concentration distribution for different cases, it was clearly shown that the amount of diffused drug is affected by the endplate permeability and the more permeable CEP, the more diffused drug into the disc specifically at the center of the disc. © 2011 IEEE.

In this paper, two lowest resonant frequencies and sensitivities of an AFM V-Shaped microcantilever made of functionally graded materials are studied. The beam is modeled by Euler-Bernoulli beam theory in which rotary inertia and shear deformation is neglected. It is assumed that the beam is made of a mixture of metal and ceramic with properties varying through the thickness of the beam. This variation is function of volume fraction of beam material constituents. The interaction between AFM tip and surface is modeled by two linear springs which expresses the normal and lateral contact stiffness. A relationship is developed to evaluate the sensitivity of FGM micro cantilever beam. Effect of volume fraction of materials and geometric parameters on resonant frequencies and sensitivities is studied. Results show that natural frequencies and sensitivities are significantly affected by volume fraction of material constituents and geometric parameters. Using these results, optimum geometric parameters and mass distributions of material constituents can be chosen so that high resolution images could be obtained.Copyright © 2010 by ASME

A large number of people are exposed to whole body vibration in their occupational life. Measuring vibration is an important tool in rehabilitation and biomechanical fields of research. We have proposed image processing as a new method to record and determine the frequency response of human body. The arranged set up for forced vibration consisted of an AC motor, a variable speed drive unit and a shaking table for producing one directional sinusoidal vibration. Volunteers were asked to stand on the shaking table at a relaxed posture. Two digital camcorders were used to capture the motion of colored pencil-dot markers on the skin of human body (forehead) and on the edge of the shaking table. After color spotting each frame, the binary image results were processed using new circle factor criteria proposed in this work, for fast finding circles based on second order statistics. The extracted points were calibrated using our own extended version of the direct linear transformation (DLT) method. Subsequently Vibration measuring software has been completely developed in Borland Delphi 5.0. Finally obtained displacement function of the body and the shaking table has been used in conjunction with Matlab 6.5 to prepare a proper algorithm for analyzing human body vibration. We discussed mechanical characteristics of the body by obtaining mechanical impedance and transmissibility from the shaking table to the head as example applications of the conducted software. The important point is the fact that all devices used in our developed measurement system are usually available in a biomechanics laboratory where a Gait system is functioning. This gives the opportunity for such laboratory to add vibration measurement to its capabilities without much excessive costs. The system has the advantage of lower noise sensitivity in comparison to accelerometer. The main advantage of this method is working with a simple user-familiar hardware with no external device attached to the subject and also a user-friendly-software.Copyright © 2004 by ASME

The human being in the environments of modern technology has to endure stresses of many and varied kinds of vibrations [1]. Measuring vibration is an important tool in rehabilitation and biomechanical fields of research. We have proposed image processing as a new method to record and determine the frequency response of human body. The subjects were exposed to whole body periodical vibration while standing on a shaking table. Two digital camcorders were used to capture the motion of colored pencil-dot markers on the skin of human body (forehead) and on the edge of the shaking table. After color spotting each frame, the binary image results were processed using new circle factor criteria proposed in this work, for fast finding circles based on second order statistics. The extracted points were calibrated using our own extended version of the direct linear transformation (DLT) method. We subsequently used Borland Delphi 5.0 language to develop useful software for measuring and analyzing human body vibration. As a result, it was clear that the proposed method was lower noise-sensitive in comparison to accelerometer. In order to investigate the validity of the software, the obtained mechanical impedance of the body were compared with other investigations in literature and showed to be compatible. The main advantage of this method is working with a simple user-familiar hardware with no external device attached to the subject and also a user-friendly-software.Copyright © 2004 by ASME

In this paper a lumped mass model was used to simulate the behavior of the human body during vertical vibration. Force method has been used to obtain the differential equations of the model, which were solved using simulink toolbox of Matlab software the appropriate damping and stiffness coefficients of shoes were chosen by comparing the results with the experimental data. The model has been used to produce a useful package, which has various abilities. We obtained the kinematics characteristics for each links of the model, in response of sine wave stimulation. This package has also the ability of comparing results by changing the damping and stiffness coefficients for the contact point (shoe) of the model. One of the important specifications of this package is its flexibility. With a little change in the codes of the program we can obtain the curves in response of other kinds of stimulations like noises and pulses.Copyright © 2002 by ASME

A new wearable assistive device (WAD) was developed to decrease required force on the lumbar spine in static holding tasks. In order to obtain moments on lumbar spine in two conditions, with and without WAD, a biomechanical static model was used for estimation of external moments on lumbar spine. The results of biomechanical models indicated that there was a reduction in the lumbar moment ranging from 20% to 43% using WAD depending on the load and flexion angle. A total of 15 male healthy subjects were tested to experimentally verify the predicted reduction of external moments on the spine by wearing WAD. Normalized electromyography (EMG) of the right and left lumbar and thoracic erector spinae (LES, TES), latissimus dorsi (LD), external oblique (EO), internal oblique (IO) and rectus abdominus (RA) muscles were monitored at three lumbar flexion positions (0°, 30° and 60°) in symmetric posture with three different loads (0, 5 and 15 kg) in two conditions of with and without WAD. The effects of WAD and load were significant for all muscles but the interaction effects were only significant for extensor muscles groups (p < 0.016). Results of statistical analysis (ANOVA) on the normalized EMG while wearing WAD indicated that the muscle activity of right and left LES, TES and LD muscles significantly decreased (p < 0.001). This reduction for right LES, TES, LD muscles at 15 kg load and 60° trunk flexion were 23.2%, 30% and 27.8%, respectively which were in good agreement with the biomechanical model results.

Vibration measurement is an important tool in many research fields; there are several methods for measuring vibration of a system. In conventional methods accelerometers are fixed to the body, so there is a systemic error due to fixing an external object to the body surface that interferes with the true vibration of the body. We have proposed image processing as a new method to record and determine the frequency response of human body. This method provides vibration measuring without using contacting sensors. Moreover the main advantage is its lower noise sensitivity in comparison to accelerometers. Further more another important point is the fact that all devices used in our developed measurement system are usually available in the biomechanics laboratory where a Gait system is functioning. This gives the opportunity for such laboratory to add vibration measurement to its capabilities without much excessive costs.Copyright © 2005 by ASME