Studies on coatings containing nano-zinc oxide for steel protection

Zinc oxide (ZnO) nanoparticles (NPs) were synthesized using the coprecipitation method. The resulting NPs were characterized by X-ray diffraction, transmission electron microscopy, and Fourier transform infrared spectroscopy. The surface morphology of the coatings has been characterized by scanning electron microscopy (SEM). SEM images show a uniform and homogeneous distribution of ZnO-NPs in polyurethane (PU) coatings while aggregates appear in epoxy coatings. Using tensile stress–strain test, the effect of the addition of ZnO-NPs on the mechanical properties of PU and epoxy coatings was examined. The addition of ZnO-NPs has enhanced the Young's modulus and the tensile strength of PU and epoxy coatings. Through the open-circuit potential and electrochemical impedance spectroscopy measurements, the anticorrosive properties of PU- or epoxy-coated mild steel panels containing ZnO-NPs have been investigated in 0.5 M NaCl solution. Nyquist impedance plots for PU and epoxy coatings in PU- or epoxy-coated mild steel panels containing ZnO-NPs were tested in the absence and presence of ZnO-NPs have different responses. It has been shown that the dispersion of ZnO-NPs significantly improves the anticorrosive performance of PU coatings. A PU coating containing 700 mg/kg ZnO-NPs is recommended to achieve better mechanical properties and corrosion resistance.     

Gate bias stress in hydrogenated and unhydrogenated polysilicon thin film transistors

Polysilicon Thin Film Transistors (TFT's), fabricated at temperature lower than 600°C, are now largely used in many applications, particularly in large area electronics. The reliability of these TFT's under different electrical conditions is then questionable. In this work, Gate bias stress is studied in two types of polysilicon TFT's originated from the same process. One type is unhydrogenated and the other is submitted to a Radio-Frequency hydrogen plasma. As this hydrogenation step is known to improve the TFT's performances but to introduce unstability, the unhydrogenated TFT's are expected to be more stable. The behaviours of the two types of TFT's under the gate bias stress are found however only different. The bias aging of unhydrogenated TFT's fit with the known model of the n-channel c-Si MOSFET's bias stress. The behaviour of the hydrogenated TFT's is explained from the model of defect creation in hydrogenated amorphous silicon.     

Cavity models of planar components grounded by via-holes and their experimental verification

Semianalytical electromagnetic models of grounding via-holes and shorted resonators of different shapes are proposed and experimentally verified. Our models are based on the cavity approach previously used for circular-pad via-holes. For the first time, a model of a square-pad via-hole is developed. By a perturbation approach, an approximate model for slightly rectangular shorted patches is also derived. All our via-hole models are verified experimentally. The influence of the technologically caused eccentricity of the via-hole shape is also modeled and studied by measurements. Additional verification is done by full-wave simulations with Agilent Momentum (2002) and IE3D-10.1. Our models compute the modal resonant frequencies, fields, and equivalent-circuit components of the via-holes. They allow for the study of the frequency limitations of grounding via-holes for high-speed applications, as well as the modes of shorted resonators for printed antennas and filters. The developed models are fast and accurate.     

A co-tree flows formulation for steady state in water distribution networks

This article describes a co-tree flows formulation for steady state simulation in water distribution networks, which reduces the original governing system of equations into a smaller set, expressed in terms of the co-tree chord flows. The formulation is derived from graph theory and matrix partitioning. The reduction in the size of the set of equations does not require any new conditions on the initial solution estimate, unlike the loop flow correction method. The proposed formulation is numerically equivalent to the link flow method. However, it requires, about 5% for the Jacobian memory storage requirements of the link flow method, thereby also drastically reducing the time of execution for solving the resulting nonlinear system, as well. Furthermore, the Jacobian matrix of the new method is symmetrical, which can reduce the memory storage by half. Thus, even for large distribution systems, there is no need for sparse matrix solvers, which trade off the storage memory with time of execution in order to manage the data requirements.     

Struma ovarii. Three malignant cases and one benign case

Four cases of struma ovarii were seen among 308 ovarian tumors removed surgically at the Salah Azaiz Institute, Tunis, Tunisia, between 1980 and 1989. This yields an occurrence rate of 1.3%, which is comparable to previously publishes rates (0.3% to 2%). One of the four tumors was malignant. Malignant transformation of struma ovarii is very rare (5% to 10%). The histologic diagnosis of malignancy is difficult, particularly in well-differentiated follicular forms. The prognosis is relatively favorable even in patients with metastases. Based on their personal experience and on a review of the literature, the authors discuss the diagnosis, management, and outcome of struma ovarii, in particular with malignant transformation.     

Application of the proper orthogonal decomposition to turbulent convective flows in a simulated Czochralski system

The aim of this work is to show the benefit of using various new methods in studying the general aspects of the convective flow in a simulated Czochralski system. We considered the influence of the crystal rotation (Reynolds number from 0 to 3.9 × 10³) and buoyancy (Rayleigh number from 0 to 7.2 × 10⁷). Velocity fields, obtained by an ultrasonic technique, the corresponding 2D Fourier spectra and a correlation function have been used. Steady, quasi-periodic and turbulent states, were recognized. The complex space–time dynamics of the flow were reduced to a binary code of the velocity fields. Thanks to the binary representation, the transition to turbulence in the Czochralski flow was found to occur via spatiotemporal intermittency. The orthogonal decomposition method was applied and the numbers of modes, involved in the dynamics of turbulent flows, calculated. As expected, the increase of the buoyancy effects induces more modes to be involved in the dynamics. The increase of the rotation effects reduces the number of modes and oscillations. The reconstruction coefficients, obtained using the proper orthogonal decomposition method, were found to reflect accurately the actual flow. The various analysis methods used in this paper allowed reaching complementary results and corroborating conclusions.     

Exploiting edge semantics in citation graphs using efficient, vertical ARM

Graphs are increasingly becoming a vital source of information within which a great deal of semantics is embedded. As the size of available graphs increases, our ability to arrive at the embedded semantics grows into a much more complicated task. One form of important hidden semantics is that which is embedded in the edges of directed graphs. Citation graphs serve as a good example in this context. This paper attempts to understand temporal aspects in publication trends through citation graphs, by identifying patterns in the subject matters of scientific publications using an efficient, vertical association rule mining model. Such patterns can (a) indicate subject-matter evolutionary history, (b) highlight subject-matter future extensions, and (c) give insights on the potential effects of current research on future research. We highlight our major differences with previous work in the areas of graph mining, citation mining, and Web-structure mining, propose an efficient vertical data representation model, introduce a new subjective interestingness measure for evaluating patterns with a special focus on those patterns that signify strong associations between properties of cited papers and citing papers, and present an efficient algorithm for the purpose of discovering rules of interest followed by a detailed experimental analysis. Imad Rahal is a newly appointed assistant professor in the Department of Computer Science at the College of Saint Benedict ∣ Saint John's University, Collegeville, MN, and a Ph.D. candidate at North Dakota State University, Fargo, ND. In August 2003, he earned his master's degree in computer science from North Dakota State University. Prior to that, he graduated summa cum laude from the Lebanese American University, Beirut, Lebanon, in February 2001 with a bachelor's degree in computer science. Currently, he is completing the final requirements for his Ph.D. degree in computer science on an NSF ND-EPSCoR doctoral dissertation assistantship with August of 2005 as a projected completion date. He is very active in research, proposal writing, and publications; his research interests are largely in the broad areas of data mining, machine learning, databases, artificial intelligence, and bioinformatics. Dongmei Ren is working for the Database Technology Institute for z/OS, IBM Silicon Valley Lab, San Jose, CA, as a staff software engineer. She holds a Ph.D. degree from North Dakota State University, Fargo, ND, and master's and bachelor's degrees from TianJin University, TianJin, China. She has been a software engineer at DaTang Telecommunications, Beijing, China. Her areas of expertise are outlier analysis, data mining and knowledge discovery, database systems, machine learning, intelligent systems, wireless networks and bioinformatics. She has been awarded the Siemens Scholarship research enhancement for excellent performance in study and research. She is a member of ACM, IEEE. Weihua Wu is a network monitoring & managed services analyst at Hewlett-Packard Co. in Canada. He holds a master's degree from North Dakota State University and a bachelor's degree from Nanjing University, both in computer science. His research areas of interest include data mining, knowledge discovery, data warehousing, information technology, network security, and bioinformatics. He has participated in various projects supported by NSF, DARPA, NASA, USDA, and GSA grants. Anne Denton is an assistant professor in computer science at North Dakota State University. Her research interests are in data mining, knowledge discovery in scientific data, and bioinformatics. Specific interests include data mining of diverse data, in which objects are characterized by a variety of properties such as numerical and categorical attributes, graphs, sequences, time-dependent attributes, and others. She received her Ph.D. in physics from the University of Mainz, Germany, and her M.S. in computer science from North Dakota State University, Fargo, ND. Christopher Besemann received his M.Sc. in computer science from North Dakota State University in Fargo, ND, 2005. Currently, he works in data mining research topics including association mining and relational data mining with recent work in model integration as a research assistant. He is accepted under a fellowship program for Ph.D. study at North Dakota State University. William Perrizo is a professor of computer science at North Dakota State University. He holds a Ph.D. degree from the University of Minnesota, a master's degree from the University of Wisconsin and a bachelor's degree from St. John's University. He has been a research scientist at the IBM Advanced Business Systems Division and the U.S. Air Force Electronic Systems Division. His areas of expertise are data mining, knowledge discovery, database systems, distributed database systems, high speed computer and communications networks, precision agriculture and bioinformatics. He is a member of ISCA, ACM, IEEE, IAAA, and AAAS.     

Electrodeposition and characterization of Cu2O thin films using sodium thiosulfate as an additive for photovoltaic solar cells

Cuprous oxide(Cu_2 O) thin films have been grown by electrodeposition technique onto ITO-coated glass substrates from aqueous copper acetate solutions with addition of sodium thiosulfate at 60 ℃. The effects of sodium thiosulfate on the electrochemical deposition of Cu20 films were investigated by cyclic voltammetry and chronoamperometry techniques. Deposited films were obtained at-0.58 V vs. SCE and characterized by X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR), scanning electron microscopy(SEM), and optical, photoelectrochemical and electrical measurements. X-ray diffraction results indicated that the synthesized Cu20 films had a pure cubic phase with a marked preferential orientation peak along(200) plane and with lattice constants a = b = c = 0.425 nm. FTIR results confirmed the presence of Cu_2 O films at peak 634 cm~(-1) SEM images of Cu_2 O films showed a better compactness and spherical-shaped composition. Optical properties of Cu20 films reveal a high optical transmission(80%) and high absorption coefficient(α 10~4 cm~(-1)) in visiblelight region. The optical energy band gap was found to be 2.103 eV. Photoelectrochemical measurements indicated that Cu20 films had n-type semiconductor conduction, which confirmed by Hall Effect measurements.Electrical properties of Cu20 films showed a low electrical resistivity of 61.30 Ω·cm~(-1), carrier concentration of-4.94 × 10~(15)cm~(-3) and mobility of 20.61 cm~2· V~(-1)·s~(-1).The obtained Cu_2 O thin films with suitable properties are promising semiconductor material for fabrication of photovoltaic solar cells.