Sharif Digital Repository

Predictive business process monitoring is concerned with predicting the process-related Key Performance Indicators (KPIs) and forecasting the future behavior of the process in realtime. Despite the amount of work contributed by researches to this field of research, the performance of existing solutions is not desirable for practical settings. Indeed, these approaches are typically context-unaware and lack generality. However, in real-life use cases, business processes are not isolated from the surrounding working environment, and thus they are influenced by many contextual events, such as events generated by IoT devices. To the best of our knowledge, there is no comprehensive study... 

Energy demand in Iran is increasing because of many reasons, for instance, low price, population and GDP growth. Its trend shows that this situation could not continue for many years, so it needs reviewing in energy policy in Iran. The aim of this paper is reviewing the whole energy system of Iran and its possible future and offering some policies for solving current and future problems. First of all, this study investigates the trend of growth of some parameters like GDP, electricity price, population, CO2 emission and electricity consumption in eight years. After that, by calculating the price of electricity generated in Iran under three different circumstances, this study is able to... 

Stress is a body's natural way of responding to any kind of demand or challenge that everyone experiences from time to time. Although short-Term stress typically does not impose a health burden, exposure to prolonged stress can lead to significant adverse physiological and behavioral changes. Coping with the impact of stress is a challenging task and in this context, stress assessment is essential in preventing detrimental long-Term effects. The public embracement of connected wearable Internet of Things (IoT) devices, as well as the proliferation of Artificial Intelligence (AI) and Machine Learning (ML) technologies, have generated new opportunities for personalized stress tracking and... 

In this paper, an underwater wireless sensor network (UWSN) is modeled with the help of queueing theory in order to evaluate the maximum stable throughput of the network. To this end, a new scenario for multi-layer mobile UWSN is considered. Then, a new MAC algorithm comprised of random access scheme (like MACAW) and CDMA-based data transmission along with a simplified routing algorithm is proposed. In order to analyze the considered UWSN scenario, we propose two related queueing networks, one for modeling the wireless node mobility and the other for representing the process of multi-hop packet transmission according to considered MAC and routing algorithms. Finally, the maximum stable... 

A nonlinear inverse finite element method is developed for estimation of initial blank shape and strain distribution in final shape. This method often based on implicit static algorithms, causes sometimes convergence problems because of strong nonlinearities. In order to avoid the converging problems, especially in the quasi vertical walls, an appropriate initial guess is introduced. By using this initial guess, the number of iterations in the nonlinear numerical solution is decreased, solution speed is significantly increased and complicated geometries can be analyzed by this method with good accuracy. Application to a Srail part shows good agreement between commercially available finite... 

An experimental study was carried out on an axisymmetric supersonic inlet with external compression in order to investigate the buzz phenomenon at different angles of attack and mass flow rates. The model was equipped with accurate and high-frequency pressure sensors, and the tests were conducted at Mach numbers varying from 1.8 to 2.5, for various angles of attack. Shadowgraph visualization technique, together with a high-speed camera, was used to provide the visual description of the shock structure in front of the inlet and to study the characteristics of buzz. Furthermore, pressure distribution over the spike surface was measured using several pressure sensors. Frequency of the buzz and... 

An experimental study was carried out on an axisymmetric supersonic inlet with external compression in order to investigate the buzz phenomenon at different angles of attack and mass flow rates. The model was equipped with accurate and high-frequency pressure sensors, and the tests were conducted at Mach numbers varying from 1.8 to 2.5, for various angles of attack. Shadowgraph visualization technique, together with a high-speed camera, was used to provide the visual description of the shock structure in front of the inlet and to study the characteristics of buzz. Furthermore, pressure distribution over the spike surface was measured using several pressure sensors. Frequency of the buzz and... 

An experimental study was carried out on an axisymmetric supersonic inlet with external compression in order to investigate the buzz phenomenon at different angles of attack and mass flow rates. The model was equipped with accurate and high-frequency pressure sensors, and the tests were conducted at Mach numbers varying from 1.8 to 2.5, for various angles of attack. Shadowgraph visualization technique, together with a high-speed camera, was used to provide the visual description of the shock structure in front of the inlet and to study the characteristics of buzz. Furthermore, pressure distribution over the spike surface was measured using several pressure sensors. Frequency of the buzz and... 

The most applications of gold nanoparticles are in the photo-electronical accessories and bio-chemical sensors. Chloride solution with cysteine additive was used as electrolyte in gold nanoparticles electrodeposition. The nucleation and growing mechanism were studied by electrochemical techniques such as cyclic voltammetry and chronoamperometry, in order to obtain a suitable nano structure. The deposition mechanism was determined as instantaneous nucleation and the dimension of particles was controlled in nanometric particle size range. Atomic Force Microscope was used to evaluate the effect of cysteine on the morphology and topography of gold nanoparticles. Finally the catalytic property of... 

A simplified efficient finite element method called the inverse approach (IA) has been developed to estimate initial blank and strain distribution in sheet metal forming. This algorithm is an inverse method since the position of points in final shape is known and their corresponding position in the initial blank should be determined. This approach deals with the geometric compatibility of finite elements, plastic deformation theory, and virtual work principle. This method often based on implicit static algorithms, sometimes causes convergence problems because of strong nonlinearities. This paper introduces an initial guess to speed up the convergence of Newton- Raphson solution. The... 

In this study, a general methodology has been developed to design the proper bearing in order to eliminate the curvature of the final product in extrusion process. Three smooth curved (advanced-surface) dies with non-symmetric T-shaped sections and different off-centricities have been studied. For each die, the proper bearing has been designed and physical and numerical modeling have been performed to validate the design. The design procedure is as follows: A formulation, based on Bezier curves, has been used to determine the exit velocity profile. Since the result of Bezier method is different from the actual velocity profile, the Chitkara corrective function has been modified and applied... 

The evolution of the organizational attitudes regarding strategic management of system physical assets and the emergence of new technologies call for special attention to maintenance and reliability. State-of-the-art literature suggested a number of techniques and strategies for estimating the equipment failure rates; however, paralyzed by lack of real-world data, existing literature mostly relied on simplifications that may bring about unique challenges and result in low-accuracy estimations. This paper reviews the existing literature in estimating and modeling the failure rate of power system equipment. The review includes the existing models and the ongoing research on degradation,... 

Carbon emissions significantly contribute to global warming, amplifying the occurrence of extreme weather events and negatively impacting the overall environmental transformation. In line with the global commitment to combat climate change through the Paris Agreement (COP21), the European Union (EU) has formulated strategies aimed at achieving climate neutrality by 2050. To achieve this goal, EU member states focus on developing long-term national strategies (NLTSs) and implementing local plans to reduce greenhouse gas (GHG) emissions in alignment with EU objectives. This study focuses on the case of Sweden and aims to introduce a comprehensive data-driven framework that predicts CO2... 

Firmware serves as a foundational software layer in modern computers, initiating as the first code executed on platform hardware, similar in function to a minimal operating system. Defined as a software interface between an operating system and platform firmware, the Unified Extensible Firmware Interface (UEFI) standardizes system initialization and management. A prominent open-source implementation of UEFI, the EFI Development Kit II (EDK2), plays a crucial role in shaping firmware architecture. Despite its widespread adoption, the architecture faces challenges such as limited system resources at early stages and a lack of standard security features. Furthermore, the scarcity of open-source... 

This work presents the details of a finite element-based numerical method to analyse general contact/impact problems, called united elements method (UEM). In contrast to usual methods, that is Lagrange Multipliers and Penalty Function, this method is conceptual, suitable for computer programming, and free from inherent deficiencies of those methods. The key points of this procedure are elimination of the normal degree of freedom of the contactor node from the system energy potential functional in terms of target surface motion, and proper calculation of target element unbalanced forces, to incorporate the contact constraints. After a review on classic formulations, the mathematical and... 

The authors propose asynchronous level crossing (LC) A/D converters for low redundancy voice sampling. They propose to utilise the family of iterative methods with adaptive thresholding (IMAT) for reconstructing voice from non-uniform LC and adaptive LC (ALC) samples thereby promoting sparsity. The authors modify the basic IMAT algorithm and propose the iterative method with adaptive thresholding for level crossing (IMATLC) algorithm for improved reconstruction performance. To this end, the authors analytically derive the basic IMAT algorithm by applying the gradient descent and gradient projection optimisation techniques to the problem of square error minimisation subjected to sparsity. The... 

According to the increasing desire towards heat transfer rate enhancement with various methods in different industries, this has been an interesting topic of many researchers. The effects of adding TiO2 and Al2O3 nanoparticles to water on heat transfer and fluid flow characteristics are investigated with a semi-analytical method in this study. Two nanofluids flow and heat transfer in a microtube are studied in presence of slip boundary conditions and magnetic fields. The nanoparticles volume fraction, magnetic fields strength, slip parameter and NBT coefficient (the ratio of Brownian to thermophoretic diffusions) effects on the nanoparticle's distribution, velocity profile, temperature... 

High-altitude test facilities are usually used to evaluate the performance of space mission engines. The supersonic exhaust diffuser, a main part of high-altitude test facility, provides the required test cell vacuum conditions by self-pumping the nozzle exhaust gases to the atmosphere. However, the plume temperature is often much higher than the temperature the diffuser structure is able to withstand, usually above 2500 K. In this study, an efficient cooling system is designed and analyzed to resolve the thermal problem. A water spray cooling technique is preferred among various existing techniques. Here, a new algorithm is developed for a spray cooling system for a supersonic exhaust... 

Feasibility of an innovative buzz detection technique through measuring the static pressure outside a mixed-compression supersonic inlet is studied. The buzz is an instability phenomenon that occurs almost in all supersonic inlets. During the buzz, shock oscillation along with pressure and mass flow fluctuations affects the performance characteristics of the inlet. The main objective of this paper is to introduce a simple and easy-to-implement method for investigation of the buzz phenomenon in a supersonic inlet. The experimental data for far field-based are compared with those of the model-based one at free stream Mach numbers of 1.8, 2.0, and 2.2 and at zero degrees angle of attack for a... 

Predicting the reaction and function of marine structures towards sea waves, is of significant importance in the design of them. There are some uncertain parameters which can be optimized to increase safety factors as well as to decrease the costs. Knowing the maximum oscillation of marine structures due to dynamic forces will play a great role on structures' safe design. The objective of this paper is to employ a reliable numerical technique to analyze the interaction between marine structures and sea waves. Simulink is an object oriented dynamic simulation package. It can develop new analysis tools aimed at a better understanding and prediction of the physics that governs the behavior of...