Sharif Digital Repository

Feature extraction and classification are the most important parts of BCI systems. The new branch of BCI studies focuses on the design of a classifier that is trained to function properly for each individual. This problem is known as Transfer Learning. In between-subject classification, due to the differences in the neural signals' distribution of different individuals, using the common methods of feature extraction for training the classifier, does not lead to high accuracy for the test subject. As a result, in this study, we present a method for extracting features that perform well in between subjects classifications. The data that we used in this study are EEG signals recorded during... 

Computational models of the central nervous system after a stroke helps to reveal the physiological mechanisms that may have strong impacts on the neuro-motor rehabilitation approaches. This paper studies the stroke subject's motor control mechanism in reaching movements by extending the previous study by incorporating the kinematics of motion as well as neural disconnection between the muscles and the CNS to further develop a planar patient specific neuro-musculoskeletal model of arm. The developed model was calibrated to eight post-stroke individuals by altering the Muscle Significance Factors (MFS) using numerical optimization to match the simulated motions with those measured... 

A large number of treatment approaches have been used for spinal cord injury improvement, a medically incurable disorder, and subsequently stem cell transplantation appears to be a promising strategy. The main objective of this study is to ascertain whether combinational therapy of human neural stem cells (hNSCs) together with lithium chloride improves cell survival, proliferation, and differentiation in a rat spinal contusion model, or not. Contusive spinal cord injury was implemented on Wistar male rats. Experimental groups comprised of: control, hNSCs transplanted, lithium chloride (Li), and hNSCs and lithium chloride (hNSCs + Li). In every experimental group, locomotor activity score and... 

Background: A few clinical trials have examined the effect of treatment interventions on postural control in patients with chronic low back pain, all of which have exclusively evaluated postural stability using traditional linear measures of postural sway. However, postural control improvement cannot be determined by exclusively relying on linear measurements, because these parameters provide no information on underlying motor control mechanisms. Objective: This study aimed to compare the effect of using lumbosacral orthoses (LSO) together with routine physical therapy, compared to routine physical therapy alone on postural control, using nonlinear analysis techniques. Methods: Forty-four... 

It is known that brain can create a sparse representation of the environment in both sensory and mnemonic forms (Olshausen & Field, 2004). Such sparse representation can be combined in downstream areas to create rich multisensory responses to support various cognitive and motor functions. Determining the components present in neuronal responses in a given region is key to deciphering its functional role and connection with upstream areas. One approach for parsing out various sources of information in a single neuron is by using linear blind source separation (BSS) techniques. However, applying linear techniques to neuronal spiking activity is likely to be suboptimal due to inherent and... 

There are relatively few comprehensive studies on driving errors and violations in Iran, a non-Western country with a high traffic fatality rate. In this study, 712 drivers completed a questionnaire at technical inspection centres and carwashes in Tehran, Iran. Respondents were asked about their demographic characteristics, accident involvement, traffic fines, and driving aberrations in the form of the Driver Behaviour Questionnaire (DBQ). The results of a principal component analysis of the DBQ showed a distinction between errors and two types of violations: speeding and non-speeding violations. Correlation analyses showed that DBQ violations were associated with a higher driving mileage, a... 

Control of Synchronous Motors at low speed has been the topic of several studies for the last years. Due to the lower amplitude of Back-EMF voltage in lower speed, it is inappropriate to merely rely on induced voltages for position estimation. In this paper, a new double carrier PWM modulation is presented in which two carrier frequencies are utilized for two legs of the inverter. This proposed method rectify the need of powerful processors which decreases the cost of the electric drive system. Employing a non-linear control system and an automatic gain control, ensures the sensorless control of the motor for a wide range of speed. © 2019 IEEE  

In this paper, a new post-fault vector control of an induction motor, fed by a faulty Cascaded H-Bridge (CHB) inverter, is presented. Among fault tolerant control methods, waveform based methods are suitable for closed-loop control and provide higher output voltage. In order to control the speed of the motor, a rotor field oriented control (RFOC) is used. During the fault, the FOC is modified to decrease the fault impact on the motor as low as possible. The proposed method is validated by means of simulation results for different loads and faults. The results show an improvement in both the final operating point and the transient response of the motor  

Objectives: To investigate the effects of competitive and noncompetitive volleyball exercises on the functional performance and motor control of the upper limbs in chronic stroke survivors. Design: Randomized clinical trial. Setting: Outpatient rehabilitation center. Participants: Chronic stroke survivors (N=48). Interventions: Participants were randomly assigned to competitive (n=16) or noncompetitive (n=16) volleyball exercise groups (60min/d volleyball exercise+30min/d traditional rehabilitation, 3d/wk for 7wk) and control group (n=16). Main Outcome Measures: Reach and grasp motor control measures were evaluated through kinematic analysis. Functional outcomes were assessed via Motor... 

Brain Computer Interface (BCI) systems, which are based on motor imagery, enable humans to command artificial peripherals by merely thinking about the task. There is a tremendous interest in implementing BCIs on portable platforms, such as Field Programmable Gate Arrays (FPGAS) due to their low-cost, low-power and portability characteristics. This article presents the design and implementation of a Brain Computer Interface (BCI) system based on motor imagery on a Virtex-6 FPGA. In order to design an accurate algorithm, the proposed method avails statistical learning methods such as Mutual Information (MI), Linear Discriminant Analysis (LDA), and Support Vector Machine (SVM). It also uses... 

A three phase electromagnetic stirrer was used to agitate aluminum A356 slurry and a dry and oxygen free argon gas was introduced in to the slurry by a porous graphite core at a same time. The prepared semi-solid slurry was then transferred into a metallic mold and was compacted by a drop weight. Results demonstrated a favorable increase in shape factor, decrease in aspect ratio and average diameter size at different intensities of stirring. The intensity of stirring was changed by altering the current passed through the magnetic coil and also bubbling intensity via the porous graphite diffuser. Different time intervals for electromagnetic stirring and gas induction were applied. Agitating... 

Brain Computer Interface (BCI) systems, which are based on motor imagery, enable humans to command artificial peripherals by merely thinking about the task. There is a tremendous interest in implementing BCIs on portable platforms, such as Field Programmable Gate Arrays (FPGAS) due to their low-cost, low-power and portability characteristics. This article presents the design and implementation of a Brain Computer Interface (BCI) system based on motor imagery on a Virtex-6 FPGA. In order to design an accurate algorithm, the proposed method avails statistical learning methods such as Mutual Information (MI), Linear Discriminant Analysis (LDA), and Support Vector Machine (SVM). It also uses... 

In directional drilling, the most important thing that leads to pulling out the drill string is end of mud motor working life. Considering the working conditions of down hole mud motors; increasing the mechanical properties of their stator’s elastomer is crucial. Some attempts were done to increase the motor performance through geometrical changes but lack of material improvement is significant in previous studies. In this study, NBR/nanoclay composite samples were prepared through melt intercalation in an internal mixer and tested with regard to the temperature and drilling mud of down hole. Hardness, tear, fatigue and tensile test results of neat NBR elastomer and nanocomposite of NBR and... 

Individuals with spinal cord injury (SCI) at lower thoracic levels might walk independently with the aid of mechanical orthoses and walker by using their unimpaired trunk and upper extremity muscles (TUEM). The required motor skills and the associated subtasks of the paraplegic locomotion, however, have not been well understood yet. The purpose of this study was to investigate the coordination of the TUEM activities throughout the paraplegic gait cycle using synergy analysis. For eight paraplegic individuals (30.6 ± 11.6 years; SCI level: T12), the kinematics data and the surface electromyography (EMG) signals of TUEM were recorded during 15 gait cycles. Non-negative matrix factorization... 

Active disturbance rejection control (ADRC) is applied to a one-axis gimbal mechanism. The dynamic model of the system is derived and validated from mathematical modeling and practical experiments. Disturbances acting on the complete model of the gimbal mechanism are introduced via base lateral acceleration and angular motion. The ADRC is designed by utilizing an extended state observer for observing and suppressing the effects of external disturbances and internal parameter uncertainties. A PID controller is used to form a basis of comparison for set-point tracking and disturbance rejection performance. The effects of identification errors and observer bandwidth are experimentally... 

Sub-harmonic stability issues due to the interaction between a load-commutated motor drive and a synchronous turbo-generator train in a Liquefied Natural Gas (LNG) station are studied in this paper. The sub-harmonic current injected by motor drives may excite the mechanical torsional modes of turbogenerator train. In this paper, the electro-mechanical interaction phenomenon is investigated and an active damper is proposed to absorb the sub-harmonic currents of motor drives and increase the damping of the electro-mechanical system. Simulations and experiments validate the instability problem and effectiveness of the proposed solution. © 2018 EPE Association  

Multi-phase induction motors feature a high fault-tolerance capability that makes them suitable for safety critical applications. On the other hand, concentrated winding is more fault-tolerant than conventional distributed winding. Therefore, the general idea is to use concentrated winding on the six-phase induction motor to gain more fault-tolerance capacity. Using concentrated winding has several advantages over distributed one, but it has the disadvantage of higher distortion of air gap flux density, which affects the motor performance significantly. In this paper, some concentrated windings are studied analytically by using the winding function analysis, and the layout with better... 

A linear ultrasonic motor (LUSM) with an elliptical-shaped metallic stator and two orthogonal vibration modes is presented in this research. The driving tip's desired vibration is generated by the excitation of two piezoelectric actuators installed inside the stator by two sinusoidal voltages with ±[Formula presented] phase difference. The working principle of the motor is described and mathematically formulated. Furthermore, finite element analysis and parametric optimization are performed to finalize the motor design. A prototype of the motor is fabricated and evaluated by identification and operation tests. The experimental and numerical characteristic curves of the motor are presented... 

Background and aim: Gait and balance disorders are common in the elderly populations, and their prevalence increases with age. This systematic review was performed to summarize the current evidence for subthreshold vibration interventions on postural control and gait in elderly. Method: A review of intervention studies including the following words in the title/abstract: insole, foot and ankle appliances, vibration, noise and elderly related to balance and gait. Databases searched included PubMed, ISI Web of Knowledge, Ovid, Scopus, and Google Scholar. Fifteen articles were selected for final evaluation. The procedure was followed using the preferred reporting items for systematic reviews... 

Currently PM2.5 is a major air pollution concern in Tehran, Iran due to frequent high levels and possible adverse impacts. In this study, which is the first of its kind to take place in Tehran, composition and sources of PM2.5 and carbonaceous aerosol were determined, and their seasonal trends were studied. In this regard, fine PM samples were collected every six days at a residential station for one year and the chemical constituents including organic marker species, metals, and ions were analyzed by chemical analysis. The source apportionment was performed using organic molecular marker-based CMB receptor modeling. Carbonaceous compounds were the major contributors to fine particulate mass...