Investigations of the Failure in Boilers Economizer Tubes Used in Power Plants

In this study, failure of a high pressure economizer tube of a boiler used in gas-Mazut combined cycle power plants was studied. Failure analysis of the tube was accomplished by taking into account visual inspection, thickness measurement, and hardness testing as well as microstructural observations using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and x-ray diffraction (XRD). Optical microscopy images indicate that there is no phase transformation during service, and ferrite-pearlite remained. The results of XRD also revealed Iron sulfate (FeSO₄) and Iron hydroxide sulfate (FeOH(SO₄)) phases formed on the steel surface. A considerable amount of Sulfur was also detected on the outer surface of the tube by EDS analysis. Dew-point corrosion was found to be the principal reason for the failure of the examined tube while it has been left out-of-service.     

Non-invasive monitoring of water content and textural changes in clay-rocks using spectral induced polarization: A laboratory investigation

Seven well-characterized clay-rocks have been taken from three test sites to perform spectral induced polarization (SIP) measurements during desiccation of these samples. These test sites include (1) the Tournemire site (IRSN) located in south of France, (2) The Bure test site (ANDRA) located in west of France, and (3) the Super-Sauze earthflow located in south western of France. We dried the samples at ambient temperature followed by heating between 65 °C and 105 °C. The quadrature conductivity, at very low-frequency, was able to discriminate between the loss of free water from the macropores and the loss of water in the micropores associated with textural changes. The calcite and quartz grain size distributions had a significant effect on the low-frequency spectrum. The inversion of our SIP data demonstrated that the generalized Cole–Cole model is an appropriate empirical and practical model for monitoring changes in water content of clay-rocks.     

Putting labs online with Web services

This paper describes an online experiment system that is based on Web services designed to support interoperable, machine-to-machine interaction over a network, and can also integrate heterogeneous resources. A service-oriented architecture was devised for online experiment systems, enabled by Web service protocols, and a methodology for wrapping the operations of the instruments into Web services. Although these methods aren't suitable for time-critical missions or applications that need real-time control, they do work for controlling standard commercial instruments over low-speed or unreliable communication networks. Using this framework, an online experiment system for students can be created that incorporates a great variety of instruments and that users can access without installing special software.     

Study on novel poly (vinyl pyrrolidone) doped MWCNTs/polyrhodanine nanocomposites: Synthesis,characterization, and thermal performance

In this paper, poly (vinyl pyrrolidone) (PVP) doped multiwall carbon nanotubes (MWCNTs/polyrhodanine), were synthesized through one-step chemical oxidative polymerization of rhodanine monomers on the surface-modified carbon nanotubes. Characterization of MWCNTs/polyrhodanine was conducted by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transforms infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and EDX spectrum analyses in which the results confirmed the successful formation of MWCNTs/polyrhodanine. In addition, to investigate the thermal properties of samples, thermogravimetric analysis (TGA) was employed, and results exhibited significant improvement in the nanocomposite thermal stability due to the addition of MWCNTs with reinforcement effect in polymer matrix.     

Modelling Energy Dissipation Over Stepped-gabion Weirs by Artificial Intelligence

The hydraulics of energy dissipation over stepped-gabion weirs is investigated by carrying out a series of laboratory experiments, building models to explain the experimental data, and testing their robustness by using the data reported by other researchers. The experiments comprise: six different stepped-gabion weirs tested in a horizontal laboratory flume, a wide range of discharge values, two weir slopes (V:H): 1:1 and 1:2, and gabion filling material gravel size (porosity equal to 38 %, 40 % and 42 %). These experimental setups were selected to ensure the development of both the nappe and skimming flow regimes within the measured dataset. The models developed for computing energy dissipation over stepped-gabion weirs comprise: multiple regression equations based on dimensional analysis theory, Artificial Neural Network (ANN) and Gene Expression Programming (GEP). The analysis shows that the measured data capture both flow regimes and the transition in between them and above all, and by using all of the data, it may be possible to identify the range of each regime. Energy dissipation modelled by the ANN formulation is successful and may be recommended for reliable estimates but those by GEP and regression analysis can still serve for rough-and-ready estimates in engineering applications.     

Magnetic Fe3O4@ polydopamine biopolymer: Synthesis,characterization and fabrication of promising nanocomposite

In this work, Functional Fe₃O₄@ polydopamine nanocomposite (Fe₃O₄@PDA) with magnetic response and special surface area were successfully assembled utilizing the strong coordination interactions between these two versatile materials. The morphology and size, crystal structure, specific saturation magnetization, chemical structure, and thermal properties were characterized by transmission electron microscopy (TEM), X‐ray diffraction (XRD), vibration magnetometer (VSM), point of zero charge (pH_pzc), Fourier infrared (FT‐IR) and thermogravimetric analysis (TGA). The self‐polymerization of dopamine could be completed within 3 days, and Fe₃O₄ nanoparticles were embedded into PDA polymer. TGA results showed that PDA content of nanocomposite can be up to 51.7 wt% and also showed a significant decrease in the decomposition temperature of PDA from 530 to 270°C in the presence of the Fe₃O₄ nanoparticles. Through TGA analysis the coating thickness was estimated to be about 0.86 nm that it is well coincident with the measured values using TEM images and XRD analysis. At room temperature by vibrating sample magnetometer (VSM), Fe₃O₄ and Fe₃O₄@PDA exhibit superparamagnetic behavior with a saturation moment of 57.87 and 44.7 emu/g, respectively. Furthermore, PZC value reduced for Fe₃O₄@PDA compared with Fe₃O₄ nanoparticles and fell from 6.7 to 3.04. J. VINYL ADDIT. TECHNOL., 25:41–47, 2019. © 2018 Society of Plastics Engineers     

AN INTERACTIVE SEARCH ASSISTANT ARCHITECTURE BASED ON INTRINSIC QUERY STREAM CHARACTERISTICS

Search engine query log mining has evolved over time to more like data stream mining due to the endless and continuous sequence of queries known as query stream. In this paper, we propose an online frequent sequence discovery (OFSD) algorithm to extract frequent phrases from within query streams, based on a new frequency rate metric, which is suitable for query stream mining. OFSD is an online, single pass, and real-time frequent sequence miner appropriate for data streams. The frequent phrases extracted by the OFSD algorithm are used to guide novice Web search engine users to complete their search queries more efficiently. YourEye, our online phrase recommender is then introduced. The advantages of YourEye compared with Google Suggest, a service powered by Google for phrase suggestion, is also described. Various characteristics of two specific Web search engine query logs are analyzed and then the query logs are used to evaluate YourEye. The experimental results confirm the significant benefit of monitoring frequent phrases within the queries instead of the whole queries because none-separable items. The number of the monitored elements substantially decreases, which results in smaller memory consumption as well as better performance. Re-ranking the retrieved pages based on past users clicks for each frequent phrase extracted by OFSD is also introduced. The preliminary results show the advantages of the proposed method compared to the similar work reported in Smyth et al.     

Nonlinear analysis, design, and implementation of a VCO in S frequency band

A VCO in S frequency band is designed by using nonlinear technique based on large signal model of semiconductor devices. The nonlinear circuit of the VCO is analyzed by a novel analytical approach of harmonic balance method as an autonomous circuit, and with fulfilling the stability condition of the network, the output specifications are determined. This proposed nonlinear approach for determining of the frequency and amplitude stability is also based on harmonic balance method. The results of the analysis are compared with those of measurements. The comparison shows good agreement between results of this analytical approach and the measurements. Zahra Ghanian was born in Tehran, Iran, in 1975. She received the B.Sc. degree in electrical engineering from Sharif University of Technology, Tehran, Iran, in 1998, and the M.Sc. degree from the Amirkabir University of Technology, Tehran, Iran, in 2001. Since 2000, she has been involved in several research and engineering projects at the Amirkabir University of Technology, Iran Telecommunications Research Center (ITRC) and Niroo Research Institute (NRI). Her main areas of interest are design, simulation and analysis of circuits for Microwave, Millimeter wave and Wireless applications. Abdolali Abdipour was born in Iran in 1966. He obtained his B.Sc. in Electrical Engineering from Tehran University, Tehran, Iran in 1989, and the M.Sc. in Electronics from Limoges University, Limoges, France in 1992. Then he achieved his PhD degree in Electronic Engineering from Paris XI University, Paris, France in March 1996. His research areas include wireless communication systems (RF Technology and Transceivers), RF/Microwave/mm-wave circuit and system design, E & M modeling of active devices and circuits, high frequency electronics (signal and noise), nonlinear modeling and analysis of microwave devices and circuits. He has published over 80 papers in the refereed journals and international conferences. He authored two books “Noise in Electronic Communication: Modeling, Analysis and measurement” and “Transmission Lines” (in Persian). He is currently an associate professor of Electrical Engineering Department at Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran. Ayaz Ghorbani received PG diploma, m. Phiel and PhD degrees from the university of Bradford U.K. in 1984, 1985 and 1987 respectively in the area of electrical and communication engineering. From 1987 up to now he has been teaching various courses in the department of electrical engineering at university of Amirkabir (Tehran poly technique) Tehran, Iran. In 1987 he was awarded John Robertshaw Travel Award to visit a number of research establishments in the United States of America from Bradford University, and in 1990 he was also awarded U.R.S.I. Young Scientists Award at general assembly of the URSI, Prague, Czech Republic. In 2004 he was in Bradford University for one year as a research visitor where he obtained post doctorate degree. Dr. Ghorbani is author and coauthor of more than seventy papers in conferences as well as scientific journals.     

Effect of specimen orientation and heat treatment on electroless Ni-PTFE-MoS<Subscript>2</Subscript> composite coatings

In this study, the effects of simultaneous co-deposition of polytetrafluoroethylene (PTFE) and MoS₂ particles on tribological properties of electroless nickel (EN) coating were studied. The influences of specimen orientation and heat treatment on EN-PTFE-MoS₂ composite coatings were also investigated. Scanning electron microscopy was used to study the morphology of coatings and the distributions of the lubricant particles in the deposits. Chemical analyses of coatings were done by electron dispersive spectrometry. The phases of the coatings were identified by X-ray diffraction utilizing CuKα radiation. Wear and friction properties of the coatings were also determined by pin-on-disk wear tester. The wear investigations showed that the EN-PTFE-MoS₂ composite coating performs better than EN-PTFE and EN-MoS₂ coatings in terms of friction coefficient and wear resistance. PTFE and MoS₂ contents of the EN-PTFE-MoS₂ coating were increased by changing the specimen orientation from vertical to horizontal configuration, which leads to enhancement in tribological properties of the coating. After heat treatment, the wear rate of EN matrix composite coating decreased with corresponding change in phase structure.     

The Tunable Porous Structure of Gelatin–Bioglass Nanocomposite Scaffolds for Bone Tissue Engineering Applications: Physicochemical,Mechanical, and In Vitro Properties

Unidirectional freeze‐casting method is used to fabricate gelatin–bioglass nanoparticles (BGNPs) scaffolds. Transmission electron microscopy (TEM) images show that sol–gel prepared BGNPs are distributed throughout the scaffold with diameters of less than 10 nm. Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetric are used to evaluate the physicochemical properties of BGNPs. Scanning electron microscopy (SEM) micrographs present an oriented porous structure and a homogeneous distribution of BGNPs in the gelatin matrix. The lamellar‐type structure indicates an improvement of mechanical strength and absorption capacity of the scaffolds. Increasing the concentration of BGNPs from 0 to 50 wt% have no noticeable effect on pore orientation, but decreases porosity and pore size distribution. Increase in BGNPs content improves the compressive strength. The absorption and biodegradation rate reduces with augmentation in BGNPs concentration. Bioactivity is evaluated through apatite formation after immersion of the nanocomposites in simulated body fluid and is verified by SEM–energy‐dispersive X‐ray spectroscopy (EDS), an element map analysis, X‐ray powder diffractometer, and FTIR spectrum. SEM images and methyl thiazolyl tetrazolium assay confirm the biocompatibility of scaffolds and the supportive behavior of nanocomposites in cellular spreading. The results show that gelatin–(30 wt%)bioglass nanocomposites have incipient physicochemical and biological properties.