Sharif Digital Repository

In this paper we propose two mutual authentication protocols for RFID systems. Generally, in RFID systems, a reader can authenticate tags in the real-time and batch modes. This paper proposes the first authentication protocol for the real-time mode. It also proposes an efficient robust mutual authentication protocol for the batch mode. Some significant characteristics of the protocols are forward security, tag anonymity, location privacy, low complexity on the back-end server, and scalability. To the best of our knowledge, our protocols offer the most enhanced security features in RFID mutual authentication protocols with respect to user privacy. In analyzing the protocols, we show how... 

In general, reliability is the ability of a system to perform and maintain its functions in routine, as well as hostile or unexpected, circumstances. The Redundancy Allocation Problem (RAP) is a combinatorial problem which maximizes system reliability by discrete simultaneous selection from available components. The main purpose of this study is to develop an effective approach to solve RAP, expeditiously. In this study, the basic assumption is considering Erlang distribution density for component failure rates. Another assumption is that each subsystem can have one of cold-standby or active redundancy strategies. The RAP is a NP-Hard problem which cannot be solved in reasonable time using... 

The steer by wire system for vehicles has attracted much attention in recent years. Steer by wire systems provide many benefits in terms of functionality and at the same time present significant challenges too. It is essential to investigate the stability of steer by wire systems using a more sophisticated model rather than common approximated models. Fractional order modeling offers a good modeling framework for complex dynamical systems involving flexible structures such as multi-mass drives. In this paper a nonlinear fractional order model for steer by wire systems is presented  

In recent years, mobile social networks have largely been developed and gained considerable popularity. An approach to protecting privacy on mobile social networks is the use of encryption and access control. Good alternatives for use on mobile social networks are the Public Broadcast Encryption approach for appropriate concordance and consistency with the structure of social networks as well as the Attribute-Based Encryption owing to its capability and proper implementation of the access control policy. Accordingly, in this paper, a framework was presented based on the Public Broadcast Encryption and Attribute-Based Encryption. Using proxies, we outsourced some of these operations in the... 

Enhancing oil extraction from oil sands with a hydraulic fracturing technique has been widely used in practice. Due to the complexity of the actual process, modelling of hydraulic fracturing is far behind its application. Reproducing the effects of high pore pressure and high temperature, combined with, complex stress changes in the oil sand reservoir, requires a comprehensive numerical model which is capable of simulating the fracturing phenomenon. To capture all of these aspects in the problem, three partial differential equations, i.e., equilibrium, flow, and heat transfer, should be solved simultaneously in a fully implicit (coupled) manner. A fully coupled thermo-hydro-mechanical... 

Until now, many algorithms have been introduced for finding arbitrary shaped clusters, but none of these algorithms is able to identify all sorts of cluster shapes and structures that are encountered in practice. Furthermore, the time complexity of the existing algorithms is usually high and applying them on large dataseis is time-consuming. In this paper, a novel fast clustering algorithm is proposed. This algorithm distinguishes clusters of different shapes using a twostage clustering approach. In the first stage, the data points are grouped into a relatively large number of fuzzy ellipsoidal sub-clusters. Then, connections between sub-clusters are established according to the Bhatiacharya... 

Wireless sensor networks (WSNs) usually consist of many tiny sensor nodes and a Sink. Problems like nodes' misbehavior due to malicious, compromised or selfishness intentions, and WSNs' security vulnerabilities against different attacks due to free and unprotected communications, untrusted and broadcasted transmissions, hostile environments and limited resources, degrade the security and overall performance of WSNs. In another direction, most of the traditional security mechanisms are unsuitable for WSNs. One significant security solution against these problems is Trust Management System (TMS); TMS enhances the security by detecting the nodes' abnormal behaviors; it improves the cooperation... 

The continuing process of software systems enlargement in size and complexity becomes system design extremely important for software production. In this way, the role of software architecture is significantly important in software development. It serves as an evaluation and implementation plan for software development and software evaluation. Consequently, choosing the correct architecture is a critical issue in software engineering domain. Moreover, software architecture selection is a multicriteria decision-making problem in which different goals and objectives must be taken into consideration. In this paper, more precise and suitable decisions in selection of architecture styles have been... 

Abstract A visible-light-active Ag3PO4/BiPO4 nanocomposite with a p-n heterojunction structure was fabricated via a co-precipitation hydrothermal process using 2-hydroxylethylammonium formate (RTIL) as a room-temperature ionic liquid. The resulting catalysts were characterized by various techniques. The photocatalytic activity of the photocatalysts was evaluated by the photodegradation of phthalocyanine Reactive Blue 21 (RB21) under both visible and UV light irradiations. The results reveal that the heterojunction composite prepared in RTIL noticeably exhibited an improvement in both efficiency and rate of RB21 photodegradation in comparison with pure Ag3PO4 and BiPO4. The enhanced... 

In this paper, we consider a cellular cognitive radio network that uses opportunistic spectrum access for its transmission in the downlink direction from base stations toward cognitive radio users. Since the spectrum is licensed to a primary network, proper resource management should be employed in the secondary network to protect primary users against excessive interference while providing acceptable utilization for secondary users. We use game theory to propose a distributed method for joint frequency and power allocation in the downlink of cognitive radio networks. Earlier works in this area were based on centralized optimization-based approaches, whereas our proposed method solves the... 

Some fundamental and unique characteristics of space are (1) global perspective, (2) above the atmosphere, (3) gravity-free environment, (4) abundant resources, and (5) exploration of space itself. If the mission doesn't rely on some fundamental and unique characteristics of space, it will likely cost more to do in space than in air or on Earth [1]. On the other hand, design of complex systems like satellites involves selecting design parameters (DPs) to satisfy the required constraints while meeting desired performance objectives. These parameters are often coupled, and their relationships not easily understood, and it makes the design an iterative process with high complexity [2]. But in... 

Node cooperation approaches improve physical layer security in wireless networks without applying data encryption. Selecting the appropriate nodes to cooperate as relays or friendly jammers, to degrade eavesdropper's link, is a challenging problem which has attracted a lot of attention in recent years. Various approaches, based on conventional exhaustive search, have been suggested for optimal relay-jammer selection and power allocation in the literature. The complexity of these methods is proportional to the number of intermediate nodes. As the number of intermediate nodes exceeds a specific bound, conventional exhaustive search appears infeasible due to high computational complexity. In... 

Flood as a natural disaster causes heavy human and economic losses and social unrests in most areas of the world. As flood control cost and flood damage compensation is a heavy burden over countries' budget, traditional flood design methods are being replaced by more reliable risk-based methods employing comprehensive risk analysis. In this respect, flood damage estimation is an important step in flood control systems design and analysis. In large river basins with complex reservoir systems and various land uses, flood damage estimation is complex, data-intensive, time demanding, and uncertain task requiring an intensive hydrologic and hydraulic analysis. In this study a simple approach is... 

A very well-covered graph is a well-covered graph without isolated vertices such that the height of its edge ideal is half of the number of vertices. In this survey article, we gather together most of the old and new results on the edge and cover ideals of these graphs. © 2022, The Author(s), under exclusive licence to Springer Nature Switzerland AG  

We address the performance of the 802.11p protocol in terms of the packet delivery ratio (PDR) and the packet reception ratio (PRR) for broadcasting safety messages in highway environments. Regarding the semi-sparse and intermediate traffic, we try to answer to questions such as what are the upper, dominant and lower bounds of PDR and PRR in each traffic condition? How they may deviate from their average values? and What fraction of vehicles may experience such bounds? To answer to such questions, we propose to consider the communication graph formed among vehicles as a special type of the complex networks and we apply the recently proposed obligatory attachment ruleto synthesize such... 

Cost estimation plays an essential role in the development of aerospace systems that are perhaps the most complex, time- and labor-consuming ones. Regarding this matter, it is unavoidable to take a systematic approach to build a realistic model through a deliberative, heuristical and easy-to-do process in the early stages of design. In the current study, complexity index theory is utilized to develop a heuristic complexity-based method to estimate various costs of aerospace systems. This method promises to be logically and practically more reliable and accurate than classical parametric methods. Logically, manipulating a group of parameters, instead of only one or two, reduces the... 

The pipe-spool fabrication process is a critical operational section in the piping projects that usually used to accelerate and discipline the installation process, especially, when we have a particular deadline for the project. For this reason, the fast and optimal scheduling of the fabrication activities with considering the real conditions and using manual or traditional methods is a significant problem for the decision-makers. In this paper, we use a novel linear programming model to schedule the spool fabrication activities based on the flexible job shop scheduling problem (FJSP). Because FJSP is a challengeable NP-hard problem, we solve the proposed mathematical model with a heuristic... 

One of the main properties of fragile watermarking schemes is to indicate the location of changes made to the image, i.e. tamper localization, In addition to detection of watermarked image modifications. In this paper, the localization property Is added to the SVD(Singular Value Decomposition) based fragile watermarking scheme proposed by Byun et al. To do this, a hierarchical watermarking structure is used, where the Image is partitioned into blocks In a multilevel hierarchy, and then the SVD-based algorithm Is employed at each level to Insert authenticating data In sub-blocks. In the verification process, blocks at the lowest hierarchical level can detect modifications made to the... 

In the present work, the spectral difference lattice Boltzmann method (SDLBM) is implemented on unstructured meshes for the solution methodology to be capable of accurately simulating the compressible flows over complex geometries. Both the inviscid and viscous compressible flows are computed by applying the unstructured SDLBM. The compressible form of the discrete Boltzmann–BGK equation with the Watari model is considered and the solution of the resulting system of equations is obtained by applying the spectral difference method on arbitrary quadrilateral meshes. The accuracy and robustness of the unstructured SDLBM for simulating the compressible flows are demonstrated by simulating four... 

The IP Lookup Process is a key bottleneck in routing due to the increase in routing table size, increasing traffic and migration to IPv6 addresses. The IP routing lookup involves computation of the Longest Prefix Matching for which existing solutions, such as BSD Radix Tries, scale poorly when traffic in the router increases or when employed for IPv6 address lookups. In this paper, we describe a CREW PRAM multiprocessor organization lookup that uses P processor for solving LPM problem. By this technique P-1 IP addresses can be looked up simultaneously thus the performance of processors increase in linear manner. First we categorize all prefixes in some groups based on their first two bytes...