Sharif Digital Repository

Electrophosphating is the novel method for accelerating the low temperature phosphating bath. This method can be performed as cathodic and anodic treatments. Both of them influence the coating deposition mechanism and therefore coating properties. In this study Zn–Ni electrophosphate coating was applied on galvanized steel using cathodic and anodic electrochemical methods. Microstructure, composition and corrosion resistance of coating were characterized by using a scanning electron microscopy, X-ray diffraction method and potentiodynamic polarization test respectively. The results of this study indicated that, by using cathodic method, compact phosphate coating with high corrosion... 

Electrophosphating is the novel method for accelerating the low temperature phosphating bath. This method can be performed as cathodic and anodic treatments. Both of them influence the coating deposition mechanism and therefore coating properties. In this study Zn-Ni electrophosphate coating was applied on galvanized steel using cathodic and anodic electrochemical methods. Microstructure, composition and corrosion resistance of coating were characterized by using a scanning electron microscopy, X-ray diffraction method and potentiodynamic polarization test respectively. The results of this study indicated that, by using cathodic method, compact phosphate coating with high corrosion... 

Purpose: The purpose of our study is to examine the functioning of internal capital markets (ICMs) within business groups in Iran. We document how the ultimate owner's economic interests in affiliated firms influence their investment and dividend policies. Design/methodology/approach: Using hand-collected data on the ownership structures of Iranian firms, we first identify group-affiliated firms using Almeida et al.’s (2011) method. Having identified business groups, we test a number of hypotheses concerning the dynamics of the ICMs and the implications of the ultimate owner’s incentives for affiliated firms’ behavior. Findings: We first demonstrate that investments of group-affiliated firms... 

Joining of dissimilar light metals by friction stir welding (FSW) is of interest to reduce weight and fuel consumption in the transport sector. Such coupled metals may need protective surface treatments, e.g. against wear or corrosion, for some applications. In this work, the formation of plasma electrolytic oxidation (PEO) coatings in a silicate-based electrolyte for corrosion protection of FSW AZ31B magnesium alloy-titanium joints has been studied. The joints, if unprotected, may be susceptible to severe galvanic corrosion in chloride-containing environments. The coatings were characterized by scanning electron microscopy, energy-dispersive spectroscopy and X-ray diffraction. Mg2SiO4 and... 

In the present study, dual layers mixed matrix membranes (MMMs) were prepared by incorporating aminated-Fe3O4 nanoparticles into the chitosan/polyvinyl alcohol nanofibers over the polyethersulfone (PES) membrane for the removal of Cr(VI) and Pb(II) ions in batch adsorption and membrane processes. The synthesized aminated-Fe3O4 nanoparticles were characterized using XRD, FESEM and FTIR analysis. The morphology and roughness of membranes were determined using SEM, TEM and AFM analysis. The effect of adsorption operating parameters such as pH (2–7), contact time (0–60 min), initial concentration of metal ions (20–1000 mgL−1) and temperature (30–50 °C) on the Cr(VI) and Pb(II) ions sorption was... 

The matching basis in field extentions is in-troduced by S. Eliahou and C. Lecouvey in [2]. In this paper we define the minimal and maximal linear matching property for field extensions and prove that if K is not algebraically closed, then K has minimal linear matching property. In this paper we will prove that algebraic number fields have maximal linear matching property. We also give a shorter proof of a result established in [6] on the fundamental theorem of algebra  

Designing an efficient and secure electronic voting (e-voting) protocol without the presence of trusted authorities, known as decentralized voting protocols, is one of the most interesting and challenging problems in cryptography. In these protocols the outcome of the protocol is computed by voters collaborating with each other. We provide a rigorous proof of security of a decentralized e-voting protocol proposed by Khader et al. in the Universal Composability (UC) Framework. This protocol is the state-of-the-art decentralized e-voting protocol in terms of efficiency and security, whose security has only been justified against a set of desired properties required in e-voting protocols. For... 

Recent years witnessed a steep rise in data generation and, consequently, the widespread adoption of software solutions able to support data-intensive applications. Many companies currently engage in data-intensive processes, however, fully embracing a data-driven paradigm is still cumbersome, and establishing a production-ready and fine-tuned deployment is time-consuming. This situation calls for innovative models and techniques to streamline the process of deployment configuration for Big Data applications. Moreover, many companies are using Cloud deployed clusters, which represent a cost-effective alternative to installation on premises. Accurate and fast prediction of the execution time... 

We have studied the thermally activated flux creep in the newly fabricated superconductors Y3Ba5Cu8O18+δ and Gd3Ba5Cu8O18+δ with transition temperature above 100 K. The thermally activated flux creep model explains the electron share in the magnetoresistivity of the samples in the vicinity of transition temperature T c . The activation energy U in a magnetic field below 15 kOe has been calculated by the corrected thermally activated flux creep model; and the pinning energy is exponentially related to the magnetic field  

In search of finding the dominant mechanism in high temperature superconductivity phenomena, the Y3Ba5Cu8O18 compound was synthesized through the standard solid-state reaction technique. Characteristic XRD experiment was performed on the samples and was analyzed by the MAUD software refinement program. The analysis results indicate a 358 phase structure with the initial nominal stoichiometry. The electrical resistivity and its behavior under different magnetic field were measured. The electrical resistivity indicates the transition temperature Tc onset = 102 K with transition width ΔTc = 2.4 K. This is the first observation of such a high transition temperature in the Y-based compound.... 

In this study, plasma electrolytic oxidation (PEO) of Ti-Mg couple metal fabricated by friction stir welding (FSW) in silicate base solution has been addressed and effect of silicate concentration in the electrolyte on coating properties was studied. Microstructure, composition and corrosion resistance of coating were characterized using scanning electron microscopy(SEM), X-ray diffraction (XRD) and potentiodynamic polarization methods. Ti-Mg couple were successfully coated simultaneously in silicate electrolyte and results of this study indicated that silicate concentration has a considerable impact on microstructure and corrosion resistance of the coating. In 5 g l-1 sodium silicate... 

The era of personal resources being sufficient for enterprise big data computations has passed. As computations are executed in the cloud, small policy changes of cloud operators may cause considerable changes in operational costs. Carefully choosing the amount of resources for a given application is thus of great importance. This, however, requires a priori knowledge of the application's performance under different configurations. Creating a performance prediction model needs to account for the heterogeneity of resources and the diversity in application workflows. Previous approaches for heterogeneous environments consider a black-box representation of the application which results in... 

Companies depend on mining data to grow their business more than ever. To achieve optimal performance of Big Data analytics workloads, a careful configuration of the cluster and the employed software framework is required. The lack of flexible and accurate performance models, however, render this a challenging task. This paper fills this gap by presenting accurate performance prediction models based on Stochastic Activity Networks (SANs). In contrast to existing work, the presented models consider multiple work queues, a critical feature to achieve high accuracy in realistic usage scenarios. We first introduce a monolithic analytical model for a multi-queue YARN cluster running DAG-based Big... 

Companies depend on mining data to grow their business more than ever. To achieve optimal performance of Big Data analytics workloads, a careful configuration of the cluster and the employed software framework is required. The lack of flexible and accurate performance models, however, render this a challenging task. This article fills this gap by presenting accurate performance prediction models based on Stochastic Activity Networks (SANs). In contrast to existing work, the presented models consider multiple work queues, a critical feature to achieve high accuracy in realistic usage scenarios. We first introduce a monolithic analytical model for a multi-queue YARN cluster running DAG-based...