Sharif Digital Repository

In this paper, nano/microstructured-conducting polypyrrole has been prepared on Cu/Au interdigital electrode surfaces by using constant potential amperometry technique. The Fe(II) ions were used as catalyst and X = ClO4 -, pTs-, Cl-, TCA-, DS-, DBS- was implemented as anion dopants. The morphologies of the films were investigated by field emission scanning electron microscope. A remarkable dependence was observed between the type of anion dopant and the morphology of polypyrrole (PPy). The sensing behavior of the PPy-X sensor has been studied toward acetone, methanol, ethanol, 1-propanol, 2-propanol, nitromethane, propylamine, pyridine, and gas mixtures of aliphatic alcohols. The responses... 

Boosting is a general method for improving the accuracy of any given learning algorithm. In this paper, we have proposed the boosting method for face recognition (FR) that improves the linear discriminant analysis (LDA)-based technique. The improvement is achieved by incorporating the regularized LDA (R-LDA) technique into the boosting framework. R-LDA is based on a new regularized Fisher's discriminant criterion, which is particularly robust against the small sample size problem compared to the traditional one used in LDA. The AdaBoost technique is utilized within this framework to generalize a set of simple FR subproblems and their corresponding LDA solutions and combines the results from... 

In this paper, the performance of the class-J mode power amplifier (PA) is studied when an auxiliary network performs active load modulation on the main transistor. Load modulation is realized by injecting an additional class-C like current with conduction angle of $alpha $ to the drain node of the main transistor. The injected current employs a phase shift of $phi $ with respect to the half-sinusoidal current of the main transistor, and its maximum value is tuned with the size of the transistor used in the auxiliary network. Detailed theoretical formulations are presented for the optimal load impedances of the PA at the fundamental and second-harmonic frequencies. Furthermore, the output... 

Naive Bayes (NB) classifier ease of use along with its remarkable performance has led many researchers to extend the scope of its applications to real-world domains by relaxing the conditional independence assumption of features given the information about the class variable. However, fulfilling this objective, most of the generalizations, cut their own way through compromising the model's simplicity, make more complex classifiers with a substantial deviation from the original one. Multi Independent Latent Component Naive Bayes Classifier (MILC-NB) leverages a set of latent variables to preserve the overall structure of naive Bayes classifier while rectifying its major restriction. Each... 

In this paper, two output matching networks (OMNs) are proposed for integrated class-J and class-J-1 mode power amplifiers (PAs). The first MN provides the required load impedances of the class-J mode (i.e., Z(f0) = Ropt + j Ropt and Z(2 f0) = -j (3π/8)Ropt), where as the second MN realizes the optimal impedances of class-J-1 PAs (i.e., Z(f0) = Ropt - j Ropt and Z(2 f0) = j (3π/8)Ropt ). Detailed theoretical analyses are presented for each MN, and the values of matching components (i.e., inductors and capacitors) are obtained in terms of Ropt. Analytical derivations are verified by simulation results, while bandwidth and loss performances of each MN are also characterized. Two... 

We study a capacitated multi-facility location-allocation problem in which the customers have stochastic demands based on Bernoulli distribution function. We consider the capacitated sub-sources of facilities to satisfy demands of customers. In the discrete stochastic problem, the goal is to find optimal locations of facilities among candidate locations and optimal allocations of existing customers to operating facilities so that the total sum of fixed costs of operating facilities, allocation cost of the customers, expected values of servicing and outsourcing costs is minimized. The model is formulated as a mixed-integer nonlinear programming problem. Since finding an optimal solution may... 

Developing a uniform polymer-based composite filament is a critical factor for a successful 3D printing process. In this regard, a novel technique for the fabrication of PLA-graphite filament with the potential to be applied to other PLA-based composite filaments was proposed and compared to the solvent casting method. This modified mixing technique involves partial dissolution of the PLA pellets surface by dichloromethane (DCM), which creates a sticky surface for the strong adhesion of reinforcement powders. The manufactured composite filament by this method exhibited excellent structural features, while the solvent casting method yielded a heterogeneous filament with a non-uniform diameter... 

The inertial microfluidic technique, as a powerful new tool for accurate cell/particle separation based on the hydrodynamic phenomenon, has drawn considerable interest in recent years. Despite numerous microfluidic techniques of particle separation, there are few articles in the literature on separation techniques addressing external outlet geometry to increase the throughput efficiency and purity. In this work, we report on a spiral inertial microfluidic device with high efficiency (>98%). Herein, we demonstrate how changing the outlet geometry can improve the particle separation throughput. We present a complete separation of 4 and 6 μm from 10 μm particles potentially applicable to... 

Naive Bayes (NB) classifier ease of use along with its remarkable performance has led many researchers to extend the scope of its applications to real-world domains by relaxing the conditional independence assumption of features given the information about the class variable. However, fulfilling this objective, most of the generalizations, cut their own way through compromising the model's simplicity, make more complex classifiers with a substantial deviation from the original one. Multi Independent Latent Component Naive Bayes Classifier (MILC-NB) leverages a set of latent variables to preserve the overall structure of naive Bayes classifier while rectifying its major restriction. Each... 

A novel magnetic nanocarrier with long spacer length and high colloidal stability has been prepared for effective delivery of doxorubicin (DOX). First, poly(amidoamine) (PAMAM) dendrimer was grown up onto the surface of superparamagnetic iron oxide nanoparticles to increase the loading amount of amine groups. Then, terminal amine groups were functionalized by polyethylene glycol dimethylester to increase the spacer length. Then anticancer drug DOX was covalently attached onto the system by hydrazone bond to forms a pH-sensitive nanocarrier. This system is designed to combine the advantage of magnetic targeting, high drug loading capacity, and controlled release  

Emerging tools that ease sharing information in online social networks (OSNs) can cause various privacy issues for users. Access control is the main security mechanism in OSNs which is used to tackle such issues. In this paper, a prioritized ontology based access control model for protecting users' information in OSNs is proposed. In the proposed model, description logic (DL) is used for modeling social networks and MKNF+ rules are used for specification of users' access control policies. Using MKNF+, we can have nonmonotonic inference (i.e., closed-world reasoning) in the access control procedure. Conflict among access rules defined by a user in an OSN, is another problem, which is resolved... 

Electrophoretic technique was used to deposit micro- and nano-sized aluminum nitride coatings on stainless steel surfaces by using a well-dispersed stable suspension produced by addition of AlN powder plus a small amount of iodine to ethanol. Parabolic regime governed the deposition. Electrophoretic deposition for 240 s at 100 V resulted in formation of a uniformly dense film on the top, but a porous inhomogeneous layer at the bottom. This was attributed to fast deposition of coarse particles and/or agglomerates at large electric fields. After drying, micro-sized particles led to a uniform crack-free interface while nano-particles resulted in fragmented non-cohesive layers. Weight loss... 

Implementation of new materials in automotive body-in-white requires through knowledge of their metallurgical response to welding process thermal cycle. This two-part paper aims at understanding the physical and mechanical metallurgy of stainless steels, as interesting candidates for automotive application, during resistance spot welding. The second part addresses the phase transformations in the heat affected zone of three types of stainless steels including austenitic, ferritic and duplex steels. Failure modes and mechanical properties of stainless steel resistance spot welds are discussed. The peak load and energy absorption of stainless steel resistance spot welds are compared with... 

This paper addresses the microstructure and mechanical performance of dissimilar resistance spot welds between AISI 430 ferritic stainless steel and drawing quality special killed (DQSK) low-carbon steel. The mechanical properties of the welds are described by peak load, failure energy, and failure mode during the tensile-shear test. Phase transformations in the fusion zone (FZ) and heat-affected zone (HAZ) are analyzed. The main metallurgical features of the weldment are the formation of a dual-phase, ferrite-martensite microstructure in the FZ, grain growth and martensite formation in the HAZ of the ferritic stainless steel side, and martensitic and eutectoid transformations in the HAZ of... 

Abstract In a recent work, Alizadeh et al. (2013) studied a capacitated multi-facility location-allocation problem in which customers had stochastic demands based on the Bernoulli distribution function. Authors considered capacitated sub-sources of facilities to satisfy customer demands. In this discrete stochastic problem, the goal was to find optimal locations of facilities among candidate locations and optimal allocations of existing customers to operating facilities so that the total sum of fixed costs of operating facilities, allocation costs of customers and expected values of servicing and outsourcing costs was minimized. The model was formulated as a mixed-integer nonlinear... 

Cloud computing as a new technology can provide significant advantages in electronic banking services. Adoption of this technology in e-banking services requires consideration of several factors. The main objective of this study is to identify and rank the effective factors on adoption of cloud computing in e-banking. The factors were identified from literature review in four dimension based on TOE and HOT-fit models (technological, human, environmental and organisational factors). As a result of this study, 16 factors were identified in four dimensions. Using fuzzy group decision-making model and pairwise comparison between factors (by a survey of 63 experts, academics and practical persons... 

Accurate knowledge of pure hydrocarbon and natural gas viscosity is essential for reliable reservoir characterization and simulation as well as economic design of natural gas processing and transport units. The most trustable sources of pure hydrocarbon and natural gas viscosity values are laboratory experiments. When there is no available experimental data for the required composition, pressure, and temperature conditions, the use of predictive methods becomes important. In this communication, a novel approach was proposed to develop for prediction of viscosity of pure hydrocarbons as well as gas mixtures containing heavy hydrocarbon components and impurities such as carbon dioxide,... 

Gas pressure reduction stations are essential in energy distribution networks because even a minor failure of these systems causes disruptive consumer problems. This study aims to introduce and implement a new knowledge-based platform that uses the synthesized expert's opinions to improve gas pressure control facilities. Given the record of failure of gas transmission system components and the data's uncertain nature, a new fuzzy expert system is developed that takes advantage of the object-oriented programming paradigm to analyze failure modes and conditions. The artificial intelligent model is designed in C# programming language, and a user-friendly interface is developed for ease of... 

In this paper, we characterize complete partite zero-divisor graphs of posets via the ideals of the posets. In particular, for complete bipartite zero-divisor graphs, we give a characterization based on the prime ideals of the posets  

We have investigated the influence of perovskite morphology on slow and fast charge transport in the perovskite solar cells. Solar cells with different perovskite cuboid sizes (50-300 nm) have been fabricated using various methylammonium iodide concentrations. Both the low-frequency capacitance and hysteresis are maximum for the cell with the largest perovskite grains (300 nm). The low-frequency capacitance is about three orders of magnitude greater than the intermediate frequency capacitance, indicating the great role of ions on the slow responses and hysteresis. The measurement of open-circuit voltage decay indicates that for the large grains of 300 nm up to 70% of Voc remains across the...