Sharif Digital Repository

We study the problem of joint information and energy transfer in a two-hop channel with a Radio frequency (RF) energy harvesting relay. We consider a finite battery size at the relay and deterministic energy loss in transmitting energy. In other words, to be able to send an energy-contained symbol, the relay must receive multiple energy-contained symbols. Thus, we face a kind of channel with memory. We model the energy saved in battery as channel state with the challenge that the receiver does not know the channel state. First, we consider the problem without any channel noise and derive an achievable rate. Next, we extend the results to the case with an independent and identically... 

In this paper, we study the degrees of freedom (DoF) of a frequency-selective K-user interference channel in the presence of an instantaneous relay (IR) with multiple receiving and transmitting antennas. We investigate two scenarios based on the IR antennas’ cooperation ability. First, we assume that the IR receiving and transmitting antennas can coordinate with each other and that the transmitted signal of each transmitting antenna can depend on the received signals of all receiving antennas, and we derive lower and upper bounds for the sum DoF of this model. In an interference alignment scheme, we divide receivers into two groups called clean and dirty receivers. We design our scheme such... 

In this letter, we consider a cache-enabled cloud radio access network with single-antenna base stations and single-antenna mobile users. Each base station can access the central processor of the network via a separate backhaul link with limited capacity. We utilize the interference alignment scheme as the transmission strategy between base stations and users. By assuming a block transmission scheme, we define a related data transmission delay. We derive the transmission delay and network power consumption. At last, we solve the problem of joint optimization of data transmission delay and network power consumption using DC programming algorithm. In our numerical results, we investigate the... 

In this paper, we study the degrees of freedom (DoF) region and sum DoF of the time-selective K-user interference channel in the presence of intelligent reflecting surfaces (IRSs). We consider both active and passive IRSs. While both types of IRS can attenuate the amplitude and change the phase of a reflected electromagnetic wave, active IRSs are also capable of amplifying the wave. We derive inner and outer bounds for the DoF region and lower and upper bounds for the sum DoF of the K-user interference channel in the presence of an active IRS and prove that the maximum value of K for the sum DoF can be achieved if the number of IRS elements exceeds a certain finite value. The analysis... 

In this letter, we examine the positioning in wireless networks in the presence of IRSs. We show that IRSs can be used to localize the user when there are not enough transmitters (Base Station). To this end, we consider a network of one transmitter, few IRSs, and one receiver, whose location should be determined. Our results indicate that we can achieve the accuracy required in the localization by controlling the number of elements of IRSs and properly selecting the location of IRSs for a given region. © 2012 IEEE  

Since compressive sensing utilizes a random matrix to map the sparse signal space to a lower dimensional transform domain, it may be possible to apply this matrix at the same time for encrypting the signal opportunistically. In this paper, a compressed sensing based encryption method is considered and the secrecy of measurement matrix of compressive sensing is analysed from the detection theory perspective. Here, the detection probability of intended and unintended receivers are compared by applying the Neyman-Pearson test. We prove that the detection probability of eavesdropper will be reduced significantly because he does not know the transform domain subspace. Furthermore, in some... 

This paper introduces a new applicable Gaussian wiretap channel with side information. In this channel, the state of the channel to the wiretapper is separated from the main channel's one. It means that the legitimate receiver and the wiretapper are listening to the transmitted signal through the different channels with different channel states which may have some correlation to each other. The state of the main channel, is assumed to be known at the transmitter, helps the sender to encrypt its messages. The achievable equivocation-rate region for this model is drived in the Gaussian case and the results are reduced to the previous works as special cases  

The secrecy problem in the state-dependent cognitive interference channel is considered in this paper. In our model, there are a primary and a secondary (cognitive) transmitter–receiver pairs, in which the cognitive transmitter has the message of the primary one as side information. In addition, the channel is affected by two channel state sequences, which are known at the cognitive transmitter and the corresponding receiver, separately. The cognitive transmitter should cooperate with the primary one, and it wishes to keep its message secure at the primary receiver. The achievable equivocation-rate regions for this channel are derived using two approaches: the binning scheme coding and... 

In this paper we consider a cognitive interference channel with two confidential messages. In our scenario, although the cognitive transmitter cooperates with the primary sender, the primary and cognitive messages must be secure at unintended receivers. The level of secrecy is measured by the equivocation rate. Also an expression is obtained for the rate-equivocation region of the discrete memoryless cognitive interference channel with confidential primary and secondary messages  

Thanks to a wide range of pore sizes by nano/macro composites of SiOC/Al2O3, such composites can serve as different layers of the structure of Packed Bed Reactor Membranes (PBRM). In the present study, the Polymer-Derived Ceramics method (PDC) has been used to synthesize nano/macro structures. Firstly, the effect of toluene as an extra carbon source on structure and microstructure of SiOC glass-ceramics was evaluated, such that, 4% (Vol) toluene was recognized as the proper amount to facilitate the synthesis of β-SiC at 1300 °C proved by XRD, Raman spectroscopy, and HR-TEM. Moreover, the presence of micro/meso-porosities was assessed by BET and TEM, indicating the capability of SiOC to serve... 

The hybrid-polymer nanocomposite poly(styrene-methyl methacrylate- acrylic acid) /nanoclay was synthesized by miniemulsion polymerization for novel use as a drilling fluid additive. Three low-solid-drilling fluids (bentonite-based; natural polymer-based; nanoclay-based) were formulated using the hybrid nanocomposite as an additive and their rheological performance compared. The polymer/clay hybrid nanoparticles significantly improve rheological and filtration properties of the drilling fluids and they remain stable at high pressure, high temperature and harsh salinity conditions. The fluids’ filtration properties improve as the concentration of the polymer/nanoclay-hybrid-nanoparticles... 

This study describes spectrometric monitored kinetic processes to determine the size of citrate-capped Au nanoparticles (Au NPs) based on aggregation induced by L-cysteine (L-Cys) as a molecular linker. The Au NPs association process is thoroughly dependent on pH, concentration and size of nanoparticles. Size dependency of aggregation inspirits to determine the average diameters of Au NPs. For this aim the procedure is achieved in aqueous medium at pH 7 (phosphate buffer), and multivariate data including kinetic spectra of Au NPs are collected during aggregation process. Subsequently partial least squares (PLS) modeling is carried out analyzing the obtained data. The model is built on the... 

Let G be a non-abelian group and Z(G) be the center of G. Associate a graph ΓG (called noncommuting graph of G) with G as follows: Take G{set minus}Z(G) as the vertices of ΓG, and join two distinct vertices x and y, whenever xy ≠ yx. Here, we prove that "the commutativity pattern of a finite non-abelian p-group determine its order among the class of groups"; this means that if P is a finite non-abelian p-group such that ΓP ≅ ΓH for some group H, then {pipe}P{pipe} = {pipe}H{pipe}  

Differential transfer matrix method is extended to analyze nonuniform nonlinear distributed feedback structures. The input-intensity dependence of the reflectivity and transmissivity of inhomogeneous nonlinear dielectric slabs is investigated for TE polarized and TM polarized incident waves  

In the bone tissue engineering field (BTE), it is of significant importance to develop bioactive multifunctional scaffolds with enhanced osteoconductivity, osteoinductivity, and antibacterial properties required for lost bone tissue regeneration. In this work, a bioactive glass-ceramic scaffold was manufactured via a novel polymer-derived ceramics (PDC) manufacturing method. To gain antibacterial properties, the silver ions were incorporated in controlled amount along with other precursors in the PDC processing stage. Microstructural and structural properties of the fabricated silicate-phosphate glass-ceramic scaffold were evaluated by scanning electron microscopy (SEM) equipped with energy... 

In the bone tissue engineering field (BTE), it is of significant importance to develop bioactive multifunctional scaffolds with enhanced osteoconductivity, osteoinductivity, and antibacterial properties required for lost bone tissue regeneration. In this work, a bioactive glass-ceramic scaffold was manufactured via a novel polymer-derived ceramics (PDC) manufacturing method. To gain antibacterial properties, the silver ions were incorporated in controlled amount along with other precursors in the PDC processing stage. Microstructural and structural properties of the fabricated silicate-phosphate glass-ceramic scaffold were evaluated by scanning electron microscopy (SEM) equipped with energy... 

We have recently introduced a high-level extension for stochastic activity networks (SANs) called coloured stochastic activity networks (CSANs). CSANs have several distinguishing properties, which make them quite appropriate for modeling and evaluation of software performance and dependability. CSANs have introduced a construct called coloured place for data manipulation. A coloured place holds a list of tokens of a userdefined token type. CSAN models can be evaluated by state space analysis techniques or discrete-event simulation. However, their state spaces will become very large, even for a small CSAN model. For efficient evaluation of these models by state space analysis methods, we will... 

Stochastic activity networks (SANs) are a stochastic generalization of Petri nets. SAN models have been used to evaluate a wide range of systems and are supported by several modeling tools. We have introduced object stochastic activity networks (OSANs) to overcome some restrictions of these models. OSANs integrate the concepts of object-orientation into SAN models. Elements of OSANs and their submodels are defined as classes. OSANs are more appropriate that most other objectoriented or high-level extensions of Petri nets for application on software systems. In this paper, we will present the definitions, behavior and an example of OSAN models. The objectorientation of OSANs and the...