Sharif Digital Repository

The B3LYP/6-311++G (d,p) density functional approach was used to study the gas-phase metal affinities of Guanosine (ribonucleoside) for the Li +, Na +, K +, Mg 2+, Ca 2+, Zn 2+, and Cu + cations. In this study we determine coordination geometries, binding strength, absolute metal ion affinities, and free energies for the most stable products. We have also compared the results for Guanosine, with our previously reported results for 20-Deoxyguanosine. Based on the results, it is obvious that MIA is strongly dependent on the charge-to-size ratio of the cation. Guanosine interacts more strongly with Zn 2+ than do with Mg 2+, Ca 2+, and Cu? and therefore stronger interactions lead to higher MIA.... 

In this work, magnetite nanoparticles (mean particle size about 20 nm) were synthesized via coprecipitation method. In order to investigate the kinetics of nanoparticle formation, variation in the amount of reactants within the process was measured using pH-meter and atomic absorption spectroscopy (AAS) instruments. Results show that nanoparticle formation behavior can be described by Avrami equations. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were performed to study the chemical and morphological characterization of nanoparticles. Some simplifying assumptions were employed for estimating the nucleation and growth rate of magnetite nanoparticles  

A low-power high-speed two-stage dynamic comparator is presented. In this circuit, PMOS transistors are used at the input of the first and second stages of the comparator. At the evaluation phase, the second stage is activated after the first stage with a predetermined delay to achieve a controllable pre-amplifier gain. Also, the first stage is turned off after the delay to reduce overall power consumption. Simulation results in 0.18 μτη CMOS technology, prove that the proposed circuit reduces the power consumption by a factor of two and reduces comparison time as large as 210ps in the same budget of offset voltage compared to the conventional circuit. Moreover, the offset voltage and power... 

This paper presents a modified astrocyte model that allows a convenient digital implementation. This model is aimed at reproducing relevant biological astrocyte behaviors, which provide appropriate feedback control in regulating neuronal activities in the central nervous system. Accordingly, we investigate the feasibility of a digital implementation for a single astrocyte and a biological neuronal network model constructed by connecting two limit-cycle Hopf oscillators to an implementation of the proposed astrocyte model using oscillator-astrocyte interactions with weak coupling. Hardware synthesis, physical implementation on field-programmable gate array, and theoretical analysis confirm... 

Public key management scheme in mobile ad hoc networks (MANETs) is an inevitable solution to achieve different security services such as integrity, confidentiality, authentication and non reputation. Probabilistic asymmetric key pre-distribution (PAKP) is a self-organized and fully distributed approach. It resolves most of MANET's challenging concerns such as storage constraint, limited physical security and dynamic topology. In such a model, secure path between two nodes is composed of one or more random successive direct secure links where intermediate nodes can read, drop or modify packets. This way, intelligent selection of intermediate nodes on a secure path is vital to ensure security... 

The purpose of the paper presented here is to deal with the well-known linear generalized predictive control (LGPC) scheme based on multiple models strategy for a tubular heat exchanger system. In this control strategy, the operating environments of the system are first represented by multiple explicit linear models. Then the best model of the system is precisely identified by a novel intelligent decision mechanism (IDM), where is organized in association with the fuzzy adaptive Kalman filter and recursive weight generator approaches. As soon as the best model of the system is identified, the corresponding predictive control action is instantly implemented on the system. In order to... 

Liquefaction is one of the most serious geotechnical hazards that may cause irreparable and financial damages. Based on in-situ testing results, several methods have been developed to evaluate the liquefaction potential. Due to continuous and repeated records, the piezocone (CPTu) has gained wide acceptance among other in-situ tests in geotechnical practice. In this paper, a new approach is proposed for liquefaction potential evaluation based on CPTu results. The new approach is verified by ten CPTu soundings (case histories) derived from different sites. By analyzing the liquefied sites, an area on the soil classification charts was introduced in this paper, showing the soil types which are... 

Laminated composite beams with non-uniform thickness are being used as primary structural elements in a wide range of advanced engineering applications. Tapered composite structures, formed by terminating some of the plies, create geometry and material discontinuities that act as sources for delamination initiation and propagation. Any small damage or delamination in these structures can progress rapidly without any visible external signs. Due to this reason early detection of damage in these systems during their service life is receiving increasing attention. The presence of a crack in a component or structure leads to changes in its global dynamic characteristics results in decreases in... 

This paper deals with the problem of vibration based health monitoring (VHM) in multi-stable asymmetrical laminated composite structures. Multi-stable asymmetrical laminates can be snapped between two or more geometries. The ability of snapping between two or more geometries in multistable composite structures makes them vulnerable to delaminate. Because of these reason early detection of damage in these systems during their service life is receiving increasing attention. In the present work, an efficient and accurate finite element model (FEM) based on layer-wise theory by considering the electro-mechanical coupling effect has been developed to investigate the actuation and /or sensing... 

Evaluating architectures and choosing the correct one is a critical issue in software engineering domain, in accordance with extremely extension of architecturedriven designs. In the first years of defining architecture styles, some special quality attributes were introduced as their basic attributes. After a moment, by utilizing them in practice, some results were obtained confirming some of attributes; some others meanwhile were not witnessed. As software architecture construction process is dependent on and addressed by both usage conditions and quality attributes, in this paper a framework has been proposed to provide an environment and a platform that can cover evaluation of... 

Purpose: An abdominal aortic aneurysm (AAA) is known as a cardiovascular disease involving localized deformation (swelling or enlargement) of aorta occurring between the renal and iliac arteries. AAA would jeopardize patients’ lives due to its rupturing risk, so prompt recognition and diagnosis of this disorder is vital. Although computed tomography angiography (CTA) is the preferred imaging modality used by radiologist for diagnosing AAA, computed tomography (CT) images can be used too. In the recent decade, there has been several methods suggested by experts in order to find a precise automated way to diagnose AAA without human intervention base on CT and CTA images. Despite great... 

The paper revisits the performance evaluation of caching in a Named Data Networking (NDN) router where the content store (CS) is supplemented by a pending interest table (PIT) which aggregates requests for a given content that arrive within the download delay. We extend prior work on caching with non-zero download delay by proposing a novel mathematical framework that is applicable to general traffic models and alternative cache insertion policies. Specifically we consider the impact of time locality in demand due to finite content lifetimes and we evaluate the use of an LRU filter to improve CS hit rate performance. The analysis is used to demonstrate that the impact of the PIT on upstream... 

While the cost of the access network could be considerably reduced by the use of caching, this is not currently happening because content providers (CPs), who alone have the detailed demand data required for optimal content placement, have no natural incentive to use them to minimize access network operator (ANO) expenditure. We argue that ANOs should therefore provide such an incentive in the form of direct subsidies paid to the CPs in proportion to the realized savings. We apply coalition game theory to design the required subsidy framework and propose a distributed algorithm, based on Lagrangian decomposition, allowing ANOs and CPs to collectively realize the optimal memory for bandwidth... 

The paper revisits the performance evaluation of caching in a Named Data Networking (NDN) router where the content store (CS) is supplemented by a pending interest table (PIT). The PIT aggregates requests for a given content that arrive within the download delay and thus brings an additional reduction in upstream bandwidth usage beyond that due to CS hits. We extend prior work on caching with non-zero download delay (non-ZDD) by proposing a novel mathematical framework that is more easily applicable to general traffic models and by considering alternative cache insertion policies. Specifically we evaluate the use of an LRU filter to improve CS hit rate performance in this non-ZDD context. We... 

We study queues with impatient customers and Processor Sharing (PS) discipline as well as other variants of PS discipline, namely, Discriminatory Processor Sharing (DPS) and Generalized Processor Sharing (GPS) disciplines, where customers have deadlines until the end of service (DES). Customers arrive according to a state-dependent Poisson process and have general impatience. Customers have exponential service times with state-dependent service rates. Analytical methods based on simple Markov chains are given for the performance analysis of such queues. The principal measures of performance are the steady-state probability of missing deadline and the steady-state probability of blocking.... 

Energy is one of the most important social and economic infrastructures and human life is strongly depends on it. In recent years, the occurrence of natural disasters such as drought as a high-impact low-probability event is undeniable. So, energy planning in the disruption situation is necessary in order to anticipate and maintain the performance of the energy system in optimal condition. This paper focuses on developing a hybrid long-term framework for evaluating the energy system resilience based on sustainability concept against drought. The model bridges the gap between long-term energy system planning in macro level and short-term switching operations or micro level modeling approach... 

Due to the extreme use of method engineering and increasing attention to construct methods customized for a specific project, domain, organization or a generic method compatible with the team characteristics and needs, existence of suitable and formalized frameworks and guidelines is one of the challenges method engineers are encountered. In this area, considering method construction as the goal of method engineering brings to the mind the software development process in which the product is a method adapting the method users' needs. This paper, with a new approach of applying software architecture in method engineering and making use of architecture styles, tries to take advantage of... 

Energy is one of the most important social and economic infrastructures and human life is strongly depends on it. In recent years, the occurrence of natural disasters such as drought as a high-impact low-probability event is undeniable. So, energy planning in the disruption situation is necessary in order to anticipate and maintain the performance of the energy system in optimal condition. This paper focuses on developing a hybrid long-term framework for evaluating the energy system resilience based on sustainability concept against drought. The model bridges the gap between long-term energy system planning in macro level and short-term switching operations or micro level modeling approach... 

We study queues with impatient customers and Processor Sharing (PS) discipline as well as other variants of PS discipline, namely, Discriminatory Processor Sharing (DPS) and Generalized Processor Sharing (GPS) disciplines, where customers have deadlines until the end of service (DES). Customers arrive according to a state-dependent Poisson process and have general impatience. Customers have exponential service times with state-dependent service rates. Analytical methods based on simple Markov chains are given for the performance analysis of such queues. The principal measures of performance are the steady-state probability of missing deadline and the steady-state probability of blocking.... 

In this paper, the elastic solution to the problem of an isotropic bi-material full-space reinforced by a perfectly bonded thin film across the media interface and subjected to arbitrary asymmetric interfacial loading is addressed. To not include any simplifications, the thin film is first considered as a layer having a finite thickness, and with the aid of Fourier expansion of Muki's potential functions in Hankel transformed space, the formulation of the problem is obtained for a tri-material full-space. Then, knowing that the flexural stiffness of the thin film is negligible, its thickness and shear modulus are assumed to tend to zero and infinity, respectively, such that its in-plane...