Sharif Digital Repository

Conventional lateral resisting systems can provide sufficient strength and ductility for design based earthquakes, although the considerable residual deformation remaining in the plasticized regions undermines the resiliency of the structures. In order to resolve this problem, various self-centering systems have been proposed and tested in recent years, most of which are specified for new buildings and are not simply suitable for retrofitting applications. Moreover, the available self-centering systems are costly and complex to assemble, which can be considered as a serious barrier for practical application. To address these drawbacks, an innovative Core-Less Self-Centering (CLSC) brace is... 

Now days titanium dioxide is used in different applications because of its good electrical properties, optical stability and cost savings. According to their different nanoscale TiO2 structures, it has been determined that 1D structures such as nanorods, nanotubes and nanowires has better properties than the other structures, including enhancing electron transport and create an offered directional way of transporting of the electrons. However, the grain boundaries in polycrystalline TiO2 nanowires or nanotubes cause electron scattering or trapping, which limit their application in optoelectronics. From these TiO2 structures, TiO2 nanorods have special importance because of less defects... 

OFDM is a multicarrier modulation scheme with high bandwidth efficiency and robustness to multipath environment used in high data rate transmission. However, a drawback of this system is the large Peak-to-Average-Power Ratio (PAR) of the transmit signal which makes its straightforward implementation quite costly. PAR in an OFDM based system can be reduced significantly by PTS method for which data recovery requires side information (SI) about the phases used at transmitter. Sending SI, not only reduces the rate, but also increases BER, for any error in SI detection can damage a large amount of transmitted information. By introducing a new phase set, we propose a PTS based method for MPSK... 

A new and fast method for the preparation of aminals is reported from the reaction of aromatic aldehydes and secondary amines in the presence of potassium carbonate in high yields. The aminal can be converted to the corresponding iminum salt in reaction with acetyl chloride very easily and in very short time with high yield. Addition of trialkylphosphite, as one possible nucleophile, to the prepared iminium salt produces the α-amino phosphonate in very high yield  

Obtaining a deep knowledge about the bubbly flow systems, which are widely applied in various chemical and industrial processes, is crucial for scholars and engineers to achieve more accurate equipment design and processes control. This paper is dedicated to experimentally investigate the distinctly and concurrently effects of fumed silica nanoparticles (NPs) and hexane vapor molecules as impurities in continuous and discrete phases, respectively, on the terminal velocity and drag coefficient of a single rising bubble in aqueous solutions. The obtained experimental data were compared to the calculated data by derived correlations in literatures. As a result, none of those can predict the... 

In this paper, the behavior of a fractional order Van der Pol-like oscillator is investigated using a describing function method. A parametric function for the boundary between oscillatory and nonoscillatory regions of this system is extracted. The analytical results are evaluated by numerical simulations which demonstrate sufficient reliability of the proposed analyzing method  

Stress sensitivity is a phenomenon that affects reservoir rock properties, such as permeability and therefore changes the well pressure transient behavior. This paper aims to study these behaviors in stress sensitive reservoirs and evaluate the pressure loss in such reservoirs during the process of hydrocarbon production. A power model is used to correlate the changes in permeability with pore pressure. A novel semi-implicit three-dimensional finite element method has been employed to numerically solve the flow problem. The numerical results have been validated by analytical results obtained in a non-sensitive reservoir. Pressure drawdown test for different scenarios has been studied. The... 

The cooperative relay cognitive interference channel (RCIC) is a four-node network with two source nodes (primary source and cognitive source) and two destination nodes, in which sources try to communicate at certain rates with their corresponding destinations simultaneously through a common medium and each destination can act as a relay to assist the other one. For the partially cooperative RCIC (PC-RCIC), in which only one of the destinations (corresponding to the cognitive source) acts as a relay, we derive an achievable rate region based on using rate splitting and superposition coding at the cognitive source, and using decode-and-forward scheme at the relay. For the degraded PC-RCIC, we... 

This study presents experimental and analytical fatigue frameworks for the dynamic fatigue life prediction of nonlinear mechanical systems under hyperchaotic oscillations. Fatigue in aluminium notched beams under hyperchaotic/chaotic vibrations is studied using a time-based analytical model. The fatigue lives obtained by the analytical model provided satisfactory correlations with those acquired by the dynamic fatigue experiments conducted on cracked aluminium beams. The model is then used to study the fatigue under Duffing chaotic, Duffing hyperchaotic, and periodic dynamic forcing. Results indicate that the classic linear cumulative damage rule delivers inaccurate high cycle fatigue (HCF)... 

This paper is devoted to the analysis of fractional order Van der Pol system studied in the literature. Based on the existing theorems on the stability of incommensurate fractional order systems, we determine parametric range for which a fractional order Van der Pol system with a specific order can perform as an undamped oscillator. Numerical simulations are presented to support the given analytical results. These results also illuminate a main difference between oscillations in a fractional order Van der Pol oscillator and its integer order counterpart. We show that contrary to integer order case, trajectories in a fractional Van der Pol oscillator do not converge to a unique cycle. © 2009... 

In this letter, we surpass the jamming effect and also estimate the jamming channel state information by using Kalman filtering (KF) approach. Furthermore, we design a closed-form beamforming weight for maximizing the achievable rate subject to the condition that the total relays power transmission would be below a predefined threshold level, which is formulated as a Quadratically Constrained Quadratic Program (QCQP). Simulation results show efficient performance of the proposed method for different destruction powers of jammer by achieving the Cramer Rao Lower Bound (CRLB). IEEE  

Strong Designated Verifier Signature (SDVS) provides authentication for the signer and the verifier such that the signer is assured that what s/he has signed, is only verified by the designated verifier. Currently, the security of most of the SDVS schemes is based on hard problems in the number theory. As it is proved that all kinds of cryptosystems which are based on the number theory will not tolerate quantum attacks, here, an SDVS scheme based on hard problems in coding theory is presented. We have proved that the suggested scheme is unforgeable under a chosen message attack in Random Oracle Model. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd  

In this letter, we surpass the jamming effect and also estimate the jamming channel state information by using the Kalman filtering approach. Furthermore, we design a closed-form beamforming weight for maximizing the achievable rate subject to the condition that the total relays power transmission would be below a predefined threshold level, which is formulated as a quadratically constrained quadratic program. Simulation results show the efficient performance of the proposed method for different destruction powers of the jammer by achieving the Cramér-Rao lower bound. © 1997-2012 IEEE  

In a cloud storage service, public auditing mechanisms allow a third party to verify integrity of the outsourced data on behalf of data users without the need to retrieve data from the cloud server. Recently, Shen et al. proposed a new lightweight and privacy preserving cloud data auditing scheme which employs a third party medium to perform time-consuming operations on behalf of users. The authors have claimed that the scheme meets the security requirements of public auditing mechanisms. In this paper, we show that Shen et al.'s scheme is insecure by proposing two attacks on the scheme. In the first attack, an outside adversary can modify some messages in transmission to the cloud server... 

Cloud storage has significantly reduced data management costs for data owners. However, loss of physical control over the data after outsourcing, triggers some security concerns such as data integrity. Provable Data Possession (PDP) protocols, enable data owners to audit the integrity of their outsourced data without the need to retrieve the file from cloud server. However, most existing PDP schemes require resource-constrained users to perform costly operations for generating metadata on file blocks. In online/offline PDP mechanisms introduced most recently, the user’s computation is divided into online/offline phases, where the costly operations are allowed to be carried out in the offline... 

Data sharing is considered as a favorite service provided by cloud storage servers in which the stored data is shared among a group of users. However, auditing such shared data is a big security issue for cloud users. In this paper, we propose an ID-Based public shared data integrity auditing scheme, in which all the group users are able to update, delete or insert new blocks into the shared data. Besides, the cloud server can revoke a misbehaving user with a minimum overhead. The scheme is secure against an untrusted cloud server and also preserves data privacy against the public verifier. Furthermore, overhead analysis shows the efficiency of proposed scheme in comparison to the existing... 

Cloud storage auditing is considered as a significant service used to verify the integrity of data stored in public cloud. However, most existing auditing protocols suffer form complex certificate management/verification since they rely on expensive Public Key Infrastructure (PKI). On the other hand, most cloud users have constrained computational resources. The few existing ID-based storage auditing protocols in the literature, require resource-constrained users to perform costly operations for generating metadata on file blocks. In this paper, we propose a storage auditing protocol which benefits from ID-based structure and lightweight user computations, simultaneously. Our construction... 

Open-pore titanium scaffolds were fabricated by sintering of compressed mixtures of TiH1.924 and urea. Spherical and irregular shaped space holders were used to investigate the effect of pore shape on cellular behavior. After removal of the space holder, the shape of the spacers was replicated to the pores. Average diameter of the pores was in the range of 300-600 lm. SEM images showed that titanium hydride resulted in higher surface roughness and larger micro porosities than pure titanium. In vitro evaluationswere carried out by using MTT assay, measuring alkaline phosphatase activity and alizarin red staining in flow perfusion bioreactor for cell culture. Observations revealed excellent...