Sharif Digital Repository

This paper proposes a novel FPGA-based matrix-inversion technique that is specifically tailored and optimized for real-time electromagnetic transients simulation of power electronic converters with high switching frequency. This is the first reported solution that is capable of solving the real-time equations related to using ideal switch model and the associated circuitry in very small time-steps (e.g., an average of 36 ns in a three-phase back-to-back converter case study), without requiring large amount of memory, being limited to small number of switches, adding parasitic elements, or depending on a priori knowledge of the circuit operation or switching strategy. The accuracy of the... 

The Boolean satisfiability problem plays a central role in computational complexity and is often used as a starting point for showing NP lower bounds. Generalisations such as Succinct SAT, where a Boolean formula is succinctly represented as a Boolean circuit, have been studied in the literature in order to lift the Boolean satisfiability problem to higher complexity classes such as NEXP. While, in theory, iterating this approach yields complete problems for k-NEXP for all k > 0, using such iterations of Succinct SAT is at best tedious when it comes to proving lower bounds. The main contribution of this paper is to show that the Boolean satisfiability problem has another canonical... 

In this paper, a new fully analog technique is proposed by means of which the adverse effects of frequency dependent gain/phase errors in quadrature transmitters are suppressed. Two separate phase and gain mismatch cancellation loops are implemented which search for the minimum side-band component. A new sign detection method is also introduced which makes sure the direction of the loop is correct. Analytical models and mathematical derivations have been presented which corroborates the circuit implementation. A proof of concept prototype using off-the-shelf components have also been measured which suggests 38-dB side-band rejection (SBR). Furthermore, the measured TX EVM and BER are... 

Employing a small Non-Volatile Memory (NVM) as the Persistent Journal Area (PJA) along with a DRAM-based buffer is an efficient approach to overcome DRAM vulnerability, named NVB-Buffer. Spin-Transfer Torque Magnetic Random Access Memory (STT-MRAM) is one of the most promising PJA candidates thanks to providing high endurance, non-volatility, and DRAM-like latency. Despite these advantages, STT-MRAM faces major reliability challenges, i.e. Retention Failure, Read Disturbance, and Write Failure, which have not been addressed in previously suggested NVB-Buffers. In this paper, we first demonstrate that the retention failure is the dominant source of errors in NVB-Buffers as it suffers from... 

Performance and reliability are two prominent factors in the design of data storage systems. To achieve higher performance, recently storage system designers use DynamicDynamic RAMRAM (DRAM)-based buffers. The volatility of DRAM brings up the possibility of data loss and data inconsistency. Thus, a part of the main storage is conventionally used as the journal area to be able of recovering unflushed data pages in the case of power failure. Moreover, periodically flushing buffered data pages to the main storage is a common mechanism to preserve a high level of reliability. This scheme, however, leads to a considerable increase in storage write traffic, which adversely affects the performance.... 

Study Design. A cross-sectional study to quantify trunk motor control during multidirectional isometric tracking tasks.Objective. To investigate the effect of chronic low back pain (LBP) on trunk neuromuscular performance while participants performed isometric exertions of trunk muscles to track targets in different angles with various magnitudes.Summary of Background Data. Tracking tasks especially in multidirectional activities are among the common research methods to quantify human motor control in different conditions. However, little information is available on trunk motor control during these tasks. There is no study investigating trunk accuracy during multidirectional isometric... 

Sensors are among essential building blocks of any Cyber-Physical Systems (CPSs). Acquisition and processing of their sensory data contribute to the power consumption and computation load of the overall CPSs. For data acquisition, the conventional fixed frequency sampling in many such systems is sub-optimal since a sizable number of samples do not contain important information. In this work, we propose a Signal-Dependent Sampling (SDS) method and present its associated circuit implementation. Using the proposed SDS method, the number of retained samples is significantly reduced with little or negligible compromise in the quality of the (reconstructed) signal. The associated error and added... 

In this research, rubber based nanocomposites with presence of nanoparticle has been studied. Styrene butadiene rubber (SBR)/nanocopper (NC) composites were prepared using two-roll mill method. Transmission electron microscope (TEM) and scanning electron microscope (SEM) images showed proper dispersion of NC in the SBR matrix without substantial agglomeration of nanoparticles. To evaluate the curing properties of nanocomposite samples, swelling and cure rheometric tests were conducted. Moreover, the rheological studies were carried out over a range of shear rates. The effect of NC particles was examined on the thermal behavior of the SBR using thermal gravimetric analysis (TGA). Furthermore,... 

Given the emergence of the Internet of Things (IoT) Cyber-Physical Systems (CPSs) and their omnipresence, reducing their power consumption is among the major design priorities. To reduce the power consumption of such systems, we propose the use of a signal-dependent sampling method in a bottom-up fashion, which can lead to up to a 94% reduction in the overall system power with negligible or no loss in performance. Moreover, the proposed technique provides further flexibility for self-aware CPSs to dynamically adjust the number of data samples that are needed for processing (and consequently reduce the power consumption) based on the application at hand and the desired trade-off between... 

It has been suggested that the central nervous system simplifies muscle control through basic units, called synergies. In this study, we have developed a novel target-matching protocol and used non-negative matrix factorization (NMF) technique to extract trunk muscle synergies and corresponding torque synergies. Isometric torque data at the L5/S1 level and electromyographic patterns of twelve abdominal and back muscles from twelve healthy participants (five females) were simultaneously recorded. Each participant performed a total number of 24 isometric target-matching tasks using 12 different angular directions and 2 levels of uniaxial and biaxial exertions. Within- and between-subject... 

Local educational institutions produce in-house English for Specific Purpose (ESP) materials according to the curriculum policies designated and developed by the Ministry of Higher Education In Iran. To this end, this book aims to be used in the Iranian setting at the tertiary level for undergraduate students majoring in Mechanical Engineering. Moreover, the style of English usage in this ESP textbook is American.
Regarding the content of the textbook, it has both thematic organizations in which the topics are relevant and includes sufficient treatment of the target language areas necessary for the students. The principle organizing approach of this textbook is theme-based. In addition,... 

The aim of this study is to employ feedback control loops to provide a stable forward dynamics simulation of human movement under repeated position constraint conditions in the environment, particularly during stair climbing. A ten-degrees-of-freedom skeletal model containing 18 Hill-type musculotendon actuators per leg was employed to simulate the model in the sagittal plane. The postural tracking and obstacle avoidance were provided by the proportional—integral—derivative controller according to the modulation of the time rate change of the joint kinematics. The stability of the model was maintained by controlling the velocity of the body's centre of mass according to the desired centre of... 

A combination of silica chloride and wet SiO2 was used as an effective deacetalizating agent for the conversion of acetals to their corresponding carbonyl derivatives under mild and heterogeneous condition