Sharif Digital Repository

Airport Traffic Control Towers (ATCTs) are among the most critical structures in an airport that are expected to keep their level of serviceability after severe strong earthquakes. Therefore analysis and design of these structures need a detailed investigation on the seismic behavior of the structure based on the structural characteristics. In this study three different existing reinforced concrete ATCTs have been investigated. As important parameters of earthquake design of structures, response modification factor (R-factor) of these towers will be determined. R-factor reduces elastic force level to design force level and contains the effect of ductility, overstrength. In Iranian seismic... 

Nowadays, prolific usage of free air as a medium for data transmission leads interests to optimize the conditions of devices which are involved in wireless communication systems. Inter-Symbol Interference (ISI) distortion is a natural characteristic of wireless channels that occurs due to propagating electromagnetic waves in different directions. Due to different paths between a transmitter and a receiver, the received signal consists of several copies of the transmitted signal with different delays. The most common way of eliminating or mitigating the effects of ISI is channel equalization. The present work leads to implementing a supervised equalization in wireless communication. The... 

Controlling the nonlinear processes is very important in industry. In this thesis, model predictive control is considered as a nonlinear control strategy and two nonlinear models, namely wiener and Hammerstein models are used and their identification methods are described. State-space model is also considered and closed-loop stability has been studied. Another strategy for controlling the nonlinear process is global linearization control. Some concepts and related theorems for this strategy are stated. PID controller is used as a linear controller for this strategy. In this model for estimating the state and load, two nonlinear observers are used. Stability analysis of output feedback... 

The objective of this thesis is to investigate the application of graph theory in managing emergency evacuations of passengers from airplanes and space stations. Given the critical importance of passenger safety and the necessity for optimized design of emergency evacuation routes, this research aims to provide a mathematical and analytical framework to reduce evacuation time under critical conditions. Common methods in this field are typically based on costly and time-consuming simulations that require significant financial and temporal resources. Instead of relying on these approaches, this study explores the application of analytical and mathematical methods, particularly graph theory.... 

Recent violation of security properties of e-voting protocols not using provable security, indicates the importance of provable security. In this thesis, we use the provable security approach to analyze security properties of e-voting protocols.In addition to presenting an efficient and provably secure protocol, the minimal assumptions to achieve privacyin e-voting protocols are analyzed. The firstcon-tribution of this thesis is presenting an efficient and provably secure coercion-resistant protocol, which is a variant of the JCJ e-voting protocol (Juels et al.,2010). It decreases the total number of JCJ’s operations fromO(n2) to O(n). The second contribution of this thesis is proving the... 

In most of the engineering applications, the mechanical behavior of materials in high strain rate deformations differs from their behavior in quasi-static deformations. In some engineering problems like impact loading on structures, metal forming and explosive forming, the range of strain rate is about . Taylor impact test is one of the experiments used for characterizing the dynamic behavior of materials in high strain rate deformations. In the Taylor impact test a rigid cylindrical projectile is impacted normally onto a hard and massive surface (anvil), the projectile deforms by mushrooming at the impact end. With plastic wave propagation analysis, the plastic deformation of projectile is... 

Safety is an important factor in the nuclear power plants due to its inherent human and environmental hazards. Therefore, in order to ensure the safety of the plant and proper functioning of its various components, a series of commissioning tests should be conducted according to international nuclear power plants standards, before its operational exploitation. On the other hand, safety of the plant can be guaranteed by modeling transient states and possible scenarios of accidents in different situations. In this study, a commissioning test of Bushehr Nuclear Power Plant (BNPP) and its associated accident is modelled by gathering geometric data and information about the facilities... 

Direct in vivo measurements of spinal loads and muscle forces are invasive. Investigators have thus used musculoskeletal biomechanical models that require kinematic data including trunk and pelvis angular movements as their inputs. . Novel devices measure anglular movements using both inertial sensors (such as gyroscopes and accelerometers) and miniature magnetometers. Relative low cost, portability, and accuracy are among specific characteristics of inertial tracking devices. The main objective of the present study was set to measure spinal kinematics including the lumbopelvic rhythm as the ratio of total lumbar rotation over pelvic rotation during trunk sagittal movement which is essential... 

The 1991 NIOSH Lifting Equation (NLE) is widely used to assess risk of injury to the spine by providing estimates of the recommended weight limit (RWL) in hands. The present study uses two biomechanical models of the spine to verify whether the RWL generates L5-S1 loads within the limits (e.g., 3400 N for compression recommended by NIOSH and 1000 N for shear recommended in some studies).Severallifting activities are simulated here to evaluate the RWL by the NLE and the L5-S1 loads by the models. In lifting activities involving moderate to large forward trunk flexion, the estimated RWL generates L5-S1 spine loads exceeding the recommended limits. The NIOSH vertical multiplier is the likely... 

Range of motion (ROM) of the thoracic spine has implications in patient discrimination for diagnostic purposes and in biomechanical models for predictions of spinal loads. Few previous studies have reported quite different thoracic ROMs. Total (T1-T12), lower (T5-T12) and upper (T1-T5) thoracic, lumbar (T12-S1), pelvis, and entire trunk (T1) ROMs were measured using an inertial tracking device as asymptomatic subjects flexed forward from their neutral upright position to full forward flexion. Correlations between body height and the ROMs were conducted. Effect of measurement errors of the trunk flexion (T1) on the model-predicted spinal loads was investigated. Mean of peak voluntary total... 

Etiological studies proves the fact that Low Back Pain (LBP) is one of the most expensive and prevalent desease all over the world. This fact illustrates the reqiurment of the special effort in ordet to reducing the pain due to this problem. Finite element modeling of human spine is one the suitable methods to simulate the behavior of human spine in different loading conditions. These conditions could be different daily occupational tasks. There is two general viewpoint toward finite element modeling of human spine. The fisrt method focuses on the detailed geometry and mechanical properties of spine, while the other complexities such as detailed muscle forces are overlooked. The latter... 

Low back pains (LBP) are prevalent and costly. One of the important factors causing LBP is excessive axial compression and shear forces that are applied on the intervertebral discs during different activities. Due to lack of direct in vivo measurement methods for estimating these loads, musculoskeletal biomechanical models have been emerged as indispensable tools under various activities. Different biomechanical models have been suggested to estimate muscle forces and spinal loads base on optimization, EMG and hybrid (EMG assisted optimization, EMGAO) methods. Although there have been a number of studies on the differences between various optimization and EMG-based methods, there has been no... 

Posterior lumbar surgery is often associated with extensive injuries to back muscles. In this thesis, the effect of such iatrogenic injuries in some patients was examined. For this purpose, the CSA of back muscles in 6 patients were measured using MR scan. To examine any natural change in CSAs of healthy people or instrument errors, same measurement were carried out on 10 healthy volunteers. In addition, a detailed anatomical model of an intact human spine was developed. With the aim of experimental studies and intact model, the post-operative model of patients was also developed. These two models were used to quantizing the change in activity of back muscles during some symmetric, normal... 

Musculoskeletal abnormalities affect joints and change their range of motion (RoM). Correcting these abnormalities thoroughly depends on the information related to the normal spine movement. Therefore, spine motion analysis can be used as an important tool to distinguish between healthy and patient individuals as well as to determine the intensity of such diseases. Additionally, existing biomechanical models need kinematics data in order to analyze spinal forces. The present study hence aims to measure 3D range of motion of thoracic and lumbar spine using inertial sensors. Their small size, portability, low weight, and relatively low cost make inertial sensors as indispensable tools in... 

The spine like every other mechanical pillar, is exposed to buckling and loss of stability. While existing biomechanical models emphasize the pressure force on the disk as the main cause of injury, there is also a possibility of local buckling phenomenon in vertebral discs. Because of the prevalence and high cost of lower back pain, it is essential to evaluate the forces carried by disks and lumbar muscles during occupational activities more accurately. In this regard, hybrid EMG-assisted optimization (EMGAO) approaches are most common methods for estimation of spinal loads. These models, not only use EMG data to be physiologically creditable, but also satisfy equilibrium requirements at all... 

We have recently designed/fabricated novel bilateral vertebra- and patient-specific drill guides for pedicle screw (PS) placements and tested their accuracy for both nondeformed and deformed thoracic spines. PS placement deviations from their preplanned positions significantly reduced when guide template were used; the success rate improved from ~72% (freehand placements) to 94% (guided placements). In the present study, we aim to use finite element (FE) analyses to evaluate the pull-out strength of these PSs inserted via either the freehand technique or our drill-guide templates. Two 3D-printed T1-T12 thoracic models of a severe scoliosis patient with a 47° thoracic dextro-scoliotic curve... 

Objective: To assess adequacy of the National Institute for Occupational Safety and Health (NIOSH) Lifting Equation (NLE) in controlling lumbar spine loads below their recommended action limits during load-handling activities in the stoop and squat using a detailed musculoskeletal model,that is, the AnyBody Modeling System.Background: The NIOSH committee employed simplistic biomechanical models for the calculation of the spine compressive loads with no estimates of the shear loads. In addition, NLE does not include the posture of the knee during manual material handling. It is therefore unknown whether the NLE would adequately control lumbar compression and shear loads below their... 

Biomechanical models require body posture to evaluate the risk of musculoskeletal injuries during daily/occupational activities like manual material handling (MMH). The procedure to measure body posture via motion-analysis techniques is complex, time-consuming, and limited to equipped laboratories. This study aims to develop an easy-to-use yet accurate model that predict human whole-body static posture (3D body coordinates and anatomical joint angles) during different MMH activities. Twenty healthy male right-handed individuals with body mass index between 18 and 26 performed 204 symmetric and asymmetric MMH activities. Each person reached (i.e., without any load in hands) the destinations... 

Body posture is an essential input of musculoskeletal models that evaluate spinal loads in occupational activities. Posture is either measured in vivo via video-camera motion capture systems or predicted via artificial neural networks (ANNs) [1]. As video-camera measurements are impractical for use in real workstations, we have recently developed an ANN that predicts full-body posture during one- and two-handed static load-handling activities. This ANN, trained based on the posture data of 20 subjects each performing 204 static load-handling activities, uses 3D coordinates of the hand-load, body weight, and body height of the worker to predict 3D coordinates of 41 full-body skin markers. The...