Sharif Digital Repository

The main objective of this work is to provide an electric supply to remote Iranian villages that have no access to electricity grid using a stand-alone hybrid system. The hybrid systems considered in this study consist of a photovoltaic array, wind turbine, diesel generator, and battery storage. Measured wind speed data was used for a wind turbine energy production model. The hybrid system optimized the electricity supply of villages with 6, 14, 20, 40, and 60 households in Bojnord, Moorchekhort, Kish, Langroud, Khash, and Meshkinshahr. The main purpose of this optimization is to find an economical system configuration that is able to fulfill the energy requirements of a given load... 

In this paper, a distributed secondary power sharing approach with low bandwidth communication network is proposed for low voltage direct current (LVDC) microgrids. Conventional droop control causes voltage drop in the grid and also a mismatch on the current of converters in the case of consideration of the line resistances. Proposed control system carry out the current value of the other converters to reach the accurate current sharing and suitable voltage regulation as well. Voltage and current controllers locally regulate the voltage and current of converters as a secondary controller. Secondary controller is realized locally and the communication network is only used to transfer the data... 

With the development of modern power systems, Smart Grid as the intelligent generation of electricity networks, has been faced with a tremendous attention. The Smart Grid systems are made up of fine-grained power grid measurements to achieve a high stability and reliability. In these networks, the data security and privacy issues for secure data sharing among the components of the system have emerged as the basic requirement. Typically, a service provider securely shares the data/commands with the smart meters under an arbitrary policy which is determined by the service providers. As the smart grid components are considered to have constrained computational resources, we cannot directly use... 

In this paper, we investigate the effect of incorrect disk replacement service on the availability of data storage systems. To this end, we first conduct Monte Carlo simulations to evaluate the availability of disk subsystem by considering disk failures and incorrect disk replacement service. We also propose a Markov model that corroborates the Monte Carlo simulation results. We further extend the proposed model to consider the effect of automatic disk fail-over policy. The results obtained by the proposed model show that overlooking the impact of incorrect disk replacement can result up to three orders of magnitude unavailability underestimation. Moreover, this study suggests that by... 

Recently, caching of the popularity video files in the caches near to the users has been proposed as a promising way to reduce data traffic. These caches can be considered as the nodes which their transmission ranges are limited but have significant storage capacity and are known as the helper nodes. To evaluate the performance and efficiency of the caches, a suitable model for their distributions should be taken into account. Stochastic geometry is a useful tool for modeling these nodes. In this paper, the helper nodes and users are distributed according to the Poisson point process distribution. However, to manage the interferences and their access to a distributed cache, the helper nodes... 

With the recent development in Non-Volatile Memory (NVM) technologies, several studies have suggested using them as an alternative to SRAMs in on-chip caches. However, limited endurance of NVMs is a major challenge when employed in the caches. This paper proposes a data manipulation technique, so-called Wearout Informed Pattern Elimination (WIPE), to improve the endurance of NVM-based caches by reducing the activity of frequent data patterns. Simulation results show that WIPE improves the endurance by up to 93% with negligible overheads. © 2017 IEEE  

Data storage systems (DSSs) and their availability play a crucial role in contemporary datacenters. Despite using mechanisms such as automatic failover in datacenters, the role of human agents and consequently their destructive errors is inevitable. Due to very large number of disk drives used in exascale datacenters and their high failure rates, the disk subsystem in storage systems has become a major source of data unavailability (DU) and data loss (DL) initiated by human errors. In this paper, we investigate the effect of incorrect disk replacement service (IDRS) on the availability and reliability of DSSs. To this end, we analyze the consequences of IDRS in a disk array, and conduct... 

Efficient utilization of renewable generation inside microgrids remains challenging. In most existing studies, the goal is to optimize the energy cost of microgrids by working in synergy with the main grid. This work aimed at maximizing the self-consumption of on-site photovoltaic (PV) generation using an electrical storage, as well as demand response solutions, in a building that was also capable of interacting with the main grid. Ten-minute resolution data were used to capture the temporal behavior of the weather. Extensive mathematical models were employed to estimate the demand for hot-water consumption, space cooling, and heating loads. The proposed framework is cast as mixed-integer... 

The Internet of Things (IoT) technology enables numerous things with different processing power and storage capacity to communicate and share data with each other. Considering the constrained devices of the IoT network in terms of processing and storage, designing a lightweight authentication scheme is quite important. So in this paper, we propose a lightweight authentication scheme based on Chebyshev Chaotic Maps. In the proposed scheme we apply a hierarchical structure to define different access controls for various entities. We then provide a formal analysis via the BAN logic to show the security of our scheme. Moreover, we compare our proposed scheme with previous ones in terms of... 

Gels are composed of crosslinked polymer network and solvent molecules. When the main chain network is incorporated with functional groups that can undergo photo-chemical reaction upon light irradiation, the gel becomes light-responsive. Under irradiation, the photosensitive groups may undergo photo-ionization process and generate charges that are attached to the main chain or diffuse into the solvent. The newly generated ions disturb the osmotic balance of the gel medium. As a result, water molecules and mobile ions are driven into or out of the network to compensate the osmotic imbalance, which eventually leads to macroscopic swelling or shrinking of the gel. In this work, we develop a... 

We propose a novel way of spreading data over multiple servers in Content Delivery Networks. Such approach provides a framework to explore trade-off between three key parameters of a content delivery network; namely, delay, storage size and communication cost. After presenting proper models for such trade-off, fundamental limits and lower and upper bounds on parameters of interest are provided for basic one-and two-dimensional spatial server arrangements. The observation that both delay and storage size can be reduced at the expense of moderate communication cost can be of great importance in a number of practical scenarios of interest. © 2018 IEEE  

The widespread use of cloud computing services raises the question of how one can delegate the processing tasks to the untrusted distributed parties without breaching the privacy of its data and algorithms. Motivated by the algorithm privacy concerns in a distributed computing system, in this paper, we introduce the private function retrieval (PFR) problem, where a user wishes to efficiently retrieve a linear function of K messages from N non-communicating replicated servers while keeping the function hidden from each individual server. The goal is to find a scheme with minimum communication cost. To characterize the fundamental limits of the communication cost, we define the capacity of PFR... 

Fragile data hiding has been extensively used for secure transmission of the sensitive data using cover images, audios and videos. In the past decade, increasingly the remote sensing applications require transmission and archiving of large number of aerial images and videos. Storage and processing of remote sensing data in the public cloud computing and storage platforms, with servers outside the control of the data owners, requires sufficient attention to persevering the privacy of the data. Furthermore, in the past few years the applications of drones and unmanned aerial vehicles demand algorithms designed especially for low altitude remote sensing data. In this paper, a novel fragile data... 

In new 400 volt energy distribution systems for telecommunication sites and data centers power density is an influential factor which is commonly desired to be provided such that the systems occupy a small space. On top of that in 400 volt energy distribution systems galvanic isolation is investigated to be inevitable. In this paper a new method is presented that makes it possible to interleave the topology of an isolated low-cost low-size rectifier in which the DC link capacitor of power factor correction stage and DC-DC stage inductor are eliminated and as result it is shown that all the benefits of interleaving such as low current ripple and higher power density are combined with the... 

The energy consumption for processing modern workloads is challenging in data centers. Due to the large datasets of cloudworkloads, the miss rate of the L1 data cache is high, andwith respect to the energy efficiency concerns, suchmisses are costly formemory instructions because lower levels ofmemory hierarchy consume more energy per access than the L1. Moreover, large last-level caches are not performance effective, in contrast to traditional scientific workloads. The aim of this article is to propose a large L1 data cache, called Domino, to reduce the number of accesses to lower levels in order to improve the energy efficiency. In designing Domino, we focus on two components that use the... 

Temporary keyword search on confidential data in a cloud environment is the main focus of this research. The cloud providers are not fully trusted. So, it is necessary to outsource data in the encrypted form. In the attribute-based keyword search (ABKS) schemes, the authorized users can generate some search tokens and send them to the cloud for running the search operation. These search tokens can be used to extract all the ciphertexts which are produced at any time and contain the corresponding keyword. Since this may lead to some information leakage, it is more secure to propose a scheme in which the search tokens can only extract the ciphertexts generated in a specified time interval. To... 

Transformers are the key component in power system transmission and distribution networks. Condition-based maintenance will increase their expected life, and online monitoring is essential to ensure operation reliability. In this paper, a new approach to transformer online monitoring is provided based on partial discharge (PD) measurement. Simultaneous measurements of PD using IEC60270 and radio frequency (RF) techniques are employed to explore new features that can be used to distinguish between internal PDs and external interference, as well as among different internal PD sources. Stream clustering based on the density grid method with only a few features required is used to categorize... 

The Internet of Things (IoT) technology enables numerous things with different processing power and storage capacity to communicate and share data with each other. Considering the constrained devices of the IoT network in terms of processing and storage, designing a lightweight authentication scheme is quite important. So in this paper, we propose a lightweight authentication scheme based on Chebyshev Chaotic Maps. In the proposed scheme we apply a hierarchical structure to define different access controls for various entities. We then provide a formal analysis via the BAN logic to show the security of our scheme. Moreover, we compare our proposed scheme with previous ones in terms of... 

Fragile data hiding has been extensively used for secure transmission of the sensitive data using cover images, audios and videos. In the past decade, increasingly the remote sensing applications require transmission and archiving of large number of aerial images and videos. Storage and processing of remote sensing data in the public cloud computing and storage platforms, with servers outside the control of the data owners, requires sufficient attention to persevering the privacy of the data. Furthermore, in the past few years the applications of drones and unmanned aerial vehicles demand algorithms designed especially for low altitude remote sensing data. In this paper, a novel fragile data... 

In a secure multiparty computation (MPC) system, there are some sources, where each one has access to a private input. The sources want to offload the computation of a polynomial function of the inputs to some processing nodes or workers. The processors are unreliable, i.e., a limited number of them may collude to gain information about the inputs. The objective is to minimize the number of required workers to calculate the polynomial, while the colluding workers gain no information about inputs. In this paper, we assume that the inputs are massive matrices, while the workers have the limited computation and storage at each worker. As proxy for that, we assume the link between each source...