Sharif Digital Repository

Discriminative subspace analysis is a popular approach for a variety of applications. There is a growing interest in subspace learning techniques for face recognition. Principal component analysis (PCA) and eigenfaces are two important subspace analysis methods have been widely applied in a variety of areas. However, the excessive dimension of data space often causes the curse of dimensionality dilemma, expensive computational cost, and sometimes the singularity problem. In this paper, a new supervised discriminative subspace analysis is presented by encoding face image as a high order general tensor. As face space can be considered as a nonlinear submanifold embedded in the tensor space, a... 

Cephalometric analysis has an important role in diagnosis and treatment of dental disharmonies. In this paper, we propose an efficient, fast, and automatic method to localize cephalometric landmarks on digitized x-ray images. The proposed algorithm uses the information of the marked landmarks on a reference normal cephalometry image as the prior knowledge. In the first step of the proposed method, the image is automatically divided into several regions and three main control points are located on it. These are then matched to their corresponding points on the reference image to form an affine transform matrix that describes how other points on the reference image should be mapped to the... 

Purpose: This paper aims to improve the manufacturability of additive manufacturing (AM) for topology-optimized (TO) structures. Enhancement of manufacturability focuses on modifying geometric constraints and classifying the building orientation (BO) of AM parts to reduce stresses and support structures (SSs). To this end, artificial intelligence (AI) networks are being developed to automate design for additive manufacturing (DfAM). Design/methodology/approach: This study considers three geometric constraints for their correction by convolutional autoencoders (CAEs) and transfer learning (TL). Furthermore, BOs of AM parts are classified using generative adversarial (GAN) and classification... 

Phase morphology, state of compatibility and various properties of blends of polycarbonate (PC) with bottle-grade and fibre-grade polyethylene terephthalate (BPET and FPET, respectively) were investigated. It was found that these blends have two-phase separated morphology with partial miscibility. Scanning electron micrographs revealed separated domains of PC-rich and PET-rich zones. PC domains appear spherical increasing in size from 2 μm for PC20/FPET80 up to about 5 μm for PC60/FPET40 blend. Further increase in PC content up to 80% caused phase inversion in which FPET appears as finely dispersed domains in continuous PC matrix. Tg of PC-rich phase decreased from 153 deg;C for pure PC down... 

This paper proposes a deep deterministic policy gradient (DDPG) based nonlinear integral backstepping (NIB) in combination with model free control (MFC) for pitch angle control of variable speed wind turbine. In particular, the controller has been presented as a digital twin (DT) concept, which is an increasingly growing method in a variety of applications. In DDPG-NIB-MFC, the pitch angle is considered as the control input that depends on the optimal rotor speed, which is usually derived from effective wind speed. The system stability according to the Lyapunov theory can be achieved by the recursive nature of the backstepping theory and the integral action has been used to compensate for... 

In the image segmentation field, traditional techniques do not completely meet the segmentation challenges mostly posed by inherently fuzzy images. Fuzzy connectedness and fuzzy clustering are considered as two well-known techniques for introducing fuzzy concepts to the problem of image segmentation. Fuzzy connectedness-based Segmentation methods consider spatial relation of image pixels by "hanging togetherness" a notion based on intensity homogeneity. But, they do not inherently utilize feature information of image pixels. On the other hand, as the segmentation domain of fuzzy clustering-based methods is the feature space they do not consider spatial relations among image pixels. Recently,... 

Machine-learning based human posture-prediction tools can potentially be robust alternatives to motion capture measurements. Existing posture-prediction approaches are confined to two-handed load-handling activities performed at heights below 120 cm from the floor and to predicting a limited number of body-joint coordinates/angles. Moreover, the extrapolating power of these tools beyond the range of the input dataset they were trained for (e.g., for underweight, overweight, or left-handed individuals) has not been investigated. In this study, we trained/validated/tested two posture-prediction (for full-body joint coordinates and angles) artificial neural networks (ANNs) using both... 

This paper discusses the optimal deployment of a cluster consisting of connected AC-coupled, low voltage (48 V) multi-carrier microgrids within an integrated framework. The utilization of this integrated framework proves to be an effective approach for enhancing the reliability, resiliency, and operational quality of the clustered multi-carrier microgrids. Furthermore, it enables improved utilization of distributed energy resources in both grid-connected and stand-alone scenarios. In order to address local objectives, this paper presents a hybrid approach to determine the optimal integration and size of distributed energy resources in autonomous multi-carrier microgrids. Additionally, the... 

With increasing concern of environmental protection and economic considerations, Wind energy has drawn much attention recently due to its high benefits to the reduction of emissions and reduction of dependency on fossil fuels. In this paper, a load dispatch model is developed for the system consisting of both thermal generators and wind turbine by GAMS Software and the recently introduced optimization strategy, Imperialist Competitive Algorithm (ICA). In addition, transmission loss is considered which approximate the system losses as a quadratic function of the real power generation with B-losses coefficients. To better represent the conditions in real power systems, the cost of modern... 

In this study a membrane biological reactor (MBR) was operated at 25±1 °C and pH = 7.5±0.5 to treat synthetic wastewater containing high phenol concentrations. Removal efficiencies of phenol and chemical oxygen demand (COD)were evaluated at four various hydraulic retention times (HRTs) of 24, 12, 8, and 4 hours. The removal rate of phenol (5.51 kg-Phenol kg-VSS-1 d-1), observed at HRT of 4 h,was the highest phenol degradation rate in the literature.According toCODtests, therewere no significant organic matter in the effluent, and phenol was degraded completely by mixed culture. Substrate inhibition was calculated from experimental growth parameters using the Haldane, Yano, and Edward... 

This paper presents a new method for the design of variable fractional delay (VFD) FIR digital filters using Genetic Algorithm (GA). Each sub-filter of Farrow structure is designed individually with defined accuracy and bandwidth. A variable mutation probability is also employed, which improves the accuracy of the solution. Compared with existing methods, it reduces the computational complexity and enhances the design flexibility. Furthermore, a simple GA is used to compute the filter coefficients in canonic singed digit (CSD) representations. Since this algorithm selects the initial population in CSD representation and searches for the digits between [-1 1], most of the digits become zero.... 

As wind energy is becoming one of the fastest-growing renewable energy resources, controlling large-scale wind turbines remains a challenging task due to its system model nonlinearities and high external uncertainties. The main goal of the current work is to propose an intelligent control of the wind turbine system without the need for model identification. For this purpose, a novel model-independent nonsingular terminal sliding-mode control (MINTSMC) using the basic principles of the ultra-local model (ULM) and combined with the single input interval type-2 fuzzy logic control (SIT2-FLC) is developed for non-linear wind turbine pitch angle control. In the suggested control framework, the... 

As wind energy is becoming one of the fastest-growing renewable energy resources, controlling large-scale wind turbines remains a challenging task due to its system model nonlinearities and high external uncertainties. The main goal of the current work is to propose an intelligent control of the wind turbine system without the need for model identification. For this purpose, a novel model-independent nonsingular terminal sliding-mode control (MINTSMC) using the basic principles of the ultra-local model (ULM) and combined with the single input interval type-2 fuzzy logic control (SIT2-FLC) is developed for non-linear wind turbine pitch angle control. In the suggested control framework, the... 

This study aimed to investigate the influence of processing parameters on the mechanical properties of auxetic polyurethane foams including Poisson’s ratio and Young’s modulus. 12 different processing scenarios were considered using the method of Plackett–Burman in the design of experiments with three replicates for each one. Eventually, 36 foams were prepared with different densities and initial thicknesses, heating temperatures and times, applied compression ratios, and the rest times between two heating steps. The microstructures of the conventional and auxetic samples were observed by scanning electron microscopy (SEM). All samples were subjected to tensile loading in one direction with... 

This paper proposes a robust investment and operation model to attend the power and heat needs of a microgrid (MG) connected to the distribution system. The optimization algorithm decides on the best investment and operation of combined heat and power (CHP), boilers, PV power generation and battery energy storage systems (BESS). For the BESS, the algorithm estimates the optimal energy storage capacity (MWh) as well as the maximum hourly delivery capacity (MW). The non-linear and non-concave heat rate chart is recast by a mix-integer linear model to have a tractable and precise model. The model considers the uncertain in some parameters using probability density function (pdf) to portrait its... 

The main goal of this study is to investigate the role of vascular graft thickness in wall stress gradient in anastomosis region. Atherosclerosis is a common heart disease causes high mortality rates every year. The gold standard treatment of atherosclerosis is replacing with autologous vein extracted from patient's body. Since proper autologous vein is limited, researchers have made efforts to achieve compliance engineered blood vessels. Mechanical stress has great effect on both smooth muscle cells and endothelial cells and it is considered as a stimulus in plaque formation. In this study, we evaluate the role of thickness in wall stress of anastomosis region. For this purpose, two... 

The main goal of this study is to investigate the role of vascular graft thickness in wall stress gradient in anastomosis region. Atherosclerosis is a common heart disease causes high mortality rates every year. The gold standard treatment of atherosclerosis is replacing with autologous vein extracted from patient's body. Since proper autologous vein is limited, researchers have made efforts to achieve compliance engineered blood vessels. Mechanical stress has great effect on both smooth muscle cells and endothelial cells and it is considered as a stimulus in plaque formation. In this study, we evaluate the role of thickness in wall stress of anastomosis region. For this purpose, two... 

Previous in-vivo investigations on the stabilizing efficacy of knee bracing for ACL reconstructed patients have been often limited to 20-30 degrees of knee flexion. In this study, the effectiveness of a uniaxial hinged functional brace to improve the knee stability was assessed at 30, 60 and 90 degrees of knee flexion. Arthrometry tests were conducted on 15 healthy subjects before and following wearing the brace and the tibial displacements were measured at up to 150 N anterior forces. Results indicated that functional bracing has a significant stabilizing effect throughout the range of knee flexion examined (p < 0.05). The rate of effectiveness, however, was not consistent across the... 

Quality of Experience (QoE) measures the overall quality of a service from users’ point of view by considering several system, human, and contextual factors. There exist various objective and subjective methods for QoE prediction. Although the subjective approach is more expensive and challenging than the objective approach, QoE’s level can be more accurately determined by a subjective test. This paper investigates various features affecting QoE by proposing a comprehensive subjective evaluation. First, we show that many unconsidered factors can significantly affect QoE. We have generated voice samples featuring different values for novel factors related to the speaker, signal, and network.... 

The main goal of this study is to investigate the effects of plaque structure on its stress distribution. Rupture of plaque causes cerebrovascular diseases which lead to high mortality rates all over the world. Computers are powerful tools to understand the mechanism of plaque rupture. In this study, 3D fluid structure interaction simulation is constructed in ABAQUS 6.13 to clarify the relation between stress distribution of plaque and its structure. A model of common carotid artery with distributed stenosis was chosen for the simulation. To investigate the effects of plaque structure on stress distribution, thickness of fibrous cap and lipid core size were varied in the stenosis....