bluuebunny/crossref_metadata_2025 huggingface dataset:
Energy conversion in small water plants with variable speed PM generator
Authors: Sobczyk Tadeusz , Mazgaj Witold , Szular Zbigniew , Węgiel Tomasz
Published: June 2011

Energy conversion in small water plants with variable speed PM generator

The Small Hydro Power Plants allow to increase the energy amount from renewable sources, especially from small rivers in mountainous areas. This paper presents a new concept of a energy conversion system for application in a Small Hydropower Plant (SHP) which is based on a permanent magnet generator (PM generator) with a propeller turbine integrated with the generator rotor. The PM generator can work at a variable speed and therefore energy produced by the PM generator has to be converted by means of a power electronic unit to fit to the three-phase power grid parameters. For this concept, dimensions and parameters of the PM generator were specially designed on account of integration with water turbine. The paper precisely describes elements of energy conversion system and also presents the results of numerical tests for chosen working conditions. An original algorithm of control strategy for power electronic unit was used to adjust generated energy to the required parameters of the three-phase grid.
Drive optimisation of a pulsatile Total Artificial Heart
Authors: Pohlmann André , Lessmann Marc , Finocchiaro Thomas , Fritschi Andreas , Steinseifer Ulrich , Schmitz-rode Thomas , Hameyer Kay
Published: June 2011

Drive optimisation of a pulsatile Total Artificial Heart

Total Artificial Hearts (TAHs) are required for the therapy of terminal heart diseases as heart transplants are only a limited option due to the available number of donor hearts. For implantation TAHs have to meet constraints regarding its dimensions, weight, perfusions and electrical losses. An innovative linear driven TAH is presented, which meets all constraints except weight. Therefore the geometry of the linear drive is optimised to reduce its weights while simultaneously limiting the electrical losses as much as possible. In order to calculate the losses, this paper introduced a combined calculation chain consisting of FEM simulations and analytical equations. Based on this chain the linear drive is optmised by the method of parameter variations. The results yield a hierachic order of parameters which are most suitable for the weight reduction of the drive for low losses. By this the weight of the linear drive is reduced by 25%. As the allowable loss limit is not exceeded yet, room for further weight reduction achieved by an optimisation of the axial geomtry parameters is given.
Metainformation infrastructure for geospatial information
Authors: Kliment T.
Published: June 2011

Metainformation infrastructure for geospatial information

The Infrastructure for Geospatial Information consists of an information component, where the bearers of geoinformation are geospatial data, and a metainformation component. The bearers of metainformation are metadata, which describe these geospatial data. Metadata serve as a tool for discovery, retrieve and evaluation of geospatial data within the Infrastructure of Geospatial Information. In order to acquire metadata from a metadata producer to a metadata consumer, the implementation of various tools - components of Metainformation Infrastructure for Geospatial Information is required. This paper describes the main principles and components of Metainformation infrastructure and the possibility of using open source tools for their implementation in practice.
Asymptotic Behaviour of Variation of Pure Polarized TERP Structure
Authors: Mochizuki Takuro
Published: June 2011

The purpose of this paper is twofold. One is to give a survey of our study on reductions of harmonic bundles, and the other is to explain a simple application in the study of TERP structures. In particular, we investigate the asymptotic behaviour of the "new supersymmetric index" for variation of pure polarized TERP structure.
Gelfand–Zetlin basis, Whittaker Vectors and a Bosonic Formula for the ${\mathfrak{sl}}_{n+1}$ Principal Subspace
Authors: Feigin Boris , Jimbo Michio , Miwa Tetsuji
Published: June 2011

We derive a bosonic formula for the character of the principal space in the level

k

vacuum module for

\widehat{\mathfrak{sl}}_{n+1}

, starting from a known fermionic formula for it. In our previous work, the latter was written as a sum consisting of Shapovalov scalar products of the Whittaker vectors for

U_{v^{\pm1}}(\mathfrak{gl}_{n+1})

. In this paper we compute these scalar products in the bosonic form, using the decomposition of the Whittaker vectors in the Gelfand–Zetlin basis. We show further that the bosonic formula obtained in this way is the quasi-classical decomposition of the fermionic formula.
Jean Cavaillès on the Effectiveness of Symbolic Thought
Authors: Khalfa Jean
Published: June 2011

The philosopher of Mathematics Jean Cavaillès (1903–1944) plays an important role in Claude Imbert's thought. His published work had a significant impact after the war. It is largely a reflection on debates on the foundation of mathematics and on two opposed models of axiomatics, foundationalist and constructionist. The philosophy he announced (cut short by his death during World War II) was to be a study of the generativity of conceptual structures, as opposed to a phenomenology of knowledge. He derived from his reflection on invention in mathematics a great scepticism on the ideas of the separateness and unity of consciousness and a criticism of the teleologies inherent in philosophies of consciousness. In that, his work, according to Claude Imbert, made possible the reflections on structures and symbolisms which were to dominate the French context in the following decades.
Barium Oxalates Combined with Oxo-Anions and Organic Cations: Syntheses and Structures of Ba2(C2O4)(H2PO3)2 and C2H10N2·Ba(H2O)2(HC2O4)4
Authors: Iveson Samuel J. , Johnston Chloe B. , Harrison William T.A.
Published: June 2011

The syntheses and single-crystal structures of Ba2(C2O4)(H2PO3)2 (1) and C2H10N2·Ba(H2O)2(HC2O4)4 (2) are described. Compound 1 is a three-dimensional mixed-anion framework containing BaO9 coordination polyhedra, which approximate to monocapped square anti-prisms: the connectivity of the BaO9 units via edges and triangular faces leads to a sheet structure. The oxalate ion in 1 is substantially twisted about its C–C bond [dihedral angle between the CO2 groups = 33.8 (3)°]. Compound 2 is a molecular salt containing ethylenediammonium dications and [Ba(HC2O4)4(H2O)2]2– dianions, which are linked by O–HLO and N–HLO hydrogen bonds. The BaO10 coordination polyhedron can be described as a distorted pentagonal anti-prism. Crystal data: 1 (C2H4Ba2O10P2), Mr = 524.68, monoclinic, C2/c (No. 15), Z = 4, a = 12.3829 (3) Å, b = 7.9124 (2) Å, c = 11.0858 (3) Å, b = 114.788 (2)°, V = 986.10 (4) Å3, R(F) = 0.016, wR(F2) = 0.040. 2 (C10H18BaN2O10), Mr = 591.60, monoclinic, C2/m (No. 12), Z = 2, a = 12.7393 (7) Å, b = 13.0111 (7) Å, c = 5.6050 (3) Å, b = 104.208 (4)°, V = 900.62 (8) Å3, R(F) = 0.027, wR(F2) = 0.054.
Sulfotyrosine Recognition as Marker for Druggable Sites in the Extracellular Space
Authors: Ziarek Joshua J. , Heroux Maxime S. , Veldkamp Christopher T. , Peterson Francis C. , Volkman Brian F.
Published: June 2011

Chemokine signaling is a well-known agent of autoimmune disease, HIV infection, and cancer. Drug discovery efforts for these signaling molecules have focused on developing inhibitors targeting their associated G protein-coupled receptors. Recently, we used a structure-based approach directed at the sulfotyrosine-binding pocket of the chemokine CXCL12, and thereby demonstrated that small molecule inhibitors acting upon the chemokine ligand form an alternative therapeutic avenue. Although the 50 members of the chemokine family share varying degrees of sequence homology (some as little as 20%), all members retain the canonical chemokine fold. Here we show that an equivalent sulfotyrosine-binding pocket appears to be conserved across the chemokine superfamily. We monitored sulfotyrosine binding to four representative chemokines by NMR. The results suggest that most chemokines harbor a sulfotyrosine recognition site analogous to the cleft on CXCL12 that binds sulfotyrosine 21 of the receptor CXCR4. Rational drug discovery efforts targeting these sites may be useful in the development of specific as well as broad-spectrum chemokine inhibitors.
Effects of Onion (Allium cepa L.) Extract Administration on Intestinal α-Glucosidases Activities and Spikes in Postprandial Blood Glucose Levels in SD Rats Model
Authors: Kim Sun-Ho , Jo Sung-Hoon , Kwon Young-In , Hwang Jae-Kwan
Published: June 2011

Diets high in calories and sweetened foods with disaccharides frequently lead to exaggerated postprandial spikes in blood glucose. This state induces immediate oxidant stress and free radicals which trigger oxidative stress-linked diabetic complications. One of the therapeutic approaches for decreasing postprandial hyperglycemia is to retard absorption of glucose by the inhibition of carbohydrate hydrolyzing enzymes,α-amylase and α-glucosidases, in the digestive organs. Therefore, the inhibitory activity of Korean onion (Allium cepa L.) extract against rat intestinal α-glucosidases, such as sucrase, maltase, and porcine pancreatic α-amylase were investigated in vitro and in vivo. The content of quercetin in ethyl alcohol extract of onion skin (EOS) was 6.04 g/100 g dried weight of onion skin. The in vitro half-maximal inhibitory concentrations (IC50) of EOS and quercetin, a major phenolic in onion, on rat intestinal sucrase were 0.40 and 0.11 mg/mL, respectively. The postprandial blood glucose lowering effects of EOS and quercetin were compared to a known type 2 diabetes drug (Acarbose), a strong α-glucosidase inhibitor in the Sprague-Dawley (SD) rat model. In rats fed on sucrose, EOS significantly reduced the blood glucose spike after sucrose loading. The area under the blood glucose-time curve (AUClast) in EOS-treated SD rats (0.5 g-EOS/kg) was significantly lower than in untreated SD rats (259.6 ± 5.1 vs. 283.1 ± 19.2 h·mg/dL). The AUClast in quercetin-treated SD rats (0.5 g-quercetin/kg) was similar to in EOS-treated group (256.1 ± 3.2 vs. 259.6 ± 5.1 h·mg/dL). Results from this study indicates that although quercetin does have blood glucose lowering potential via α-glucosidase inhibition, there are other bioactive compounds present in onion skin. Furthermore, the effects of two weeks administration of EOS in a high carbohydrate-dietary mixture (Pico 5053) on sucrase and maltase activities in intestine were evaluated in SD rat model. Compared to the upper and middle parts of intestine, the activities of sucrase in the lower parts of intestine remained significantly higher after two weeks of EOS treatment. These results indicate that EOS may improve exaggerated postprandial spikes in blood glucose and glucose homeostasis since it inhibits intestinal sucrase and thus delays carbohydrate absorption, although clinical trials are needed.
Design and Synthesis of a Dual Linker for Solid Phase Synthesis of Oleanolic Acid Derivatives
Authors: Wang Shaorong , Fang Weishuo
Published: June 2011

A hydrophilic amino-terminated poly(ethylene glycol)-type dual linker for solid phase synthesis of oleanolic acid derivatives using trityl chloride resin was designed and synthesized for the first time. Model reactions in both liquid and solid phase were performed to show the feasibility of its selective cleavage at two different sites. The biological assay results indicated that the long and flexible alkyl ether functionality in the linker is less likely to be critical for the binding event. Following the successful solid-phase synthesis of model compounds, the potential of this dual linker in reaction monitoring and target identification is deemed worthy of further study.
Energy-Efficient Algorithm for Sensor Networks with Non-Uniform Maximum Transmission Range
Authors: Yu Yimin , Song Chao , Liu Ming , Gong Haigang
Published: June 2011

In wireless sensor networks (WSNs), the energy hole problem is a key factor affecting the network lifetime. In a circular multi-hop sensor network (modeled as concentric coronas), the optimal transmission ranges of all coronas can effectively improve network lifetime. In this paper, we investigate WSNs with non-uniform maximum transmission ranges, where sensor nodes deployed in different regions may differ in their maximum transmission range. Then, we propose an Energy-efficient algorithm for Non-uniform Maximum Transmission range (ENMT), which can search approximate optimal transmission ranges of all coronas in order to prolong network lifetime. Furthermore, the simulation results indicate that ENMT performs better than other algorithms.
Diversité des carrières d'auteur de l'audiovisuel et du spectacle vivant. Les auteurs de la SACD, 1997-2008
Authors: Gouyon Marie
Published: June 2011

R éSUMé En 2008, la Société des auteurs et compositeurs dramatiques (SACD) a versé 136 millions d’euros de droits à 17 700 auteurs et compositeurs dramatiques. Entre 1997 et 2008, les répertoires gérés par la SACD ont beaucoup évolué, en particulier celui de l’audiovisuel, du fait des mutations technologiques intervenues depuis la fin des années 1990 dans ce secteur : apparition puis généralisation de la télévision numérique terrestre (TNT), développement des chaînes thématiques, etc. Les auteurs se distinguent nettement les uns des autres selon le répertoire (audiovisuel ou spectacle vivant) auquel ils participent, leur durée et leur volume de production, leur niveau de contributions aux diffusions et aux représentations, ainsi par les montants de droits perçus. La population des auteurs et compositeurs dramatiques reste âgée et très masculine, bien que les femmes y soient de plus en plus nombreuses.
Factors affecting farmers' networking decisions
Authors: Pascucci Stefano
Published: June 2011

This paper analyses farmers' decisions to carry out transactions by using three different types of networks: input supply cooperatives, processing and/or marketing cooperatives, and producers associations. We use arguments from economic sociology and new institutional economics to define the main factors affecting farmers' networking decisions, namely relational, asset and location specificity. We applied a multivariate probit (MVP) model to a sample of 15,368 Italian farmers recorded in the 2006 FADN database in order to analyse the simultaneousness of networking decisions and the main driving factors involved. Our results show that farmers are more likely to join different network types simultaneously.
Language and Text-to-Speech Technologies for Highly Accessible Language & Culture Learning
Authors: Gelan Anouk
Published: June 2011

This contribution presents the results of the â??Speech technology integrated learning modules for Intercultural Dialogue
An Experience of Educational Innovation for the Collaborative Learning in Software Engineering
Authors: Yelmo Juan C , Fernandez-Corugedo Juan
Published: June 2011

This paper describes the experience in collaborative learning based educational innovation for the Software Engineering Subject at the Telecommunications Engineering School of the Universidad Politécnica de Madrid. We describe the context of evolution of the Software Engineering related subjects in the Masterâ??s degree in Telecommunications Engineering (specialization in Telematics) for their adaptation to the educational and organizational postulates of the European Space for Higher Education. In this context, we describe a pilot project for the adaptation of the Software Engineering Lab course, which includes the development and validation of a software engineering tool environment and a web platform for collaborative work.
An Electrochemical Impedance Study of AISI 321 Stainless Steel in 0.5 M H2SO4
Authors: Fattah-Alhosseini A. , Mosavi M. , Allahdadi A.
Published: June 2011

The electrochemical behavior of passive films formed on AISI 321 has been examined using electrochemical impedance spectroscopy. AISI 321 is characterized by high interfacial impedance, thereby illustrating its high corrosion resistance. Results showed that the interfacial impedance and the polarization resistance initially increase with applied potential, within the low potential. However, at a sufficiently high potential ( V), the interfacial impedance and the polarization resistance decrease with increasing potential. The impedance data were adequately represented by an equivalent electrical circuit model based on point defect model, which described the behavior of the passive film on stainless steel more satisfactorily than the proposed models.
MMP-Activated Fluorescence Imaging Detects Early Joint Inflammation in Collagen-Antibody-Induced Arthritis in CC-Chemokine Receptor-2-Null Mice,In-Vivo
Authors: Ibarra Jessica M. , Jimenez Fabio , Martinez Hernan G. , Clark Kassandra , Ahuja Seema S.
Published: June 2011

The Standard measures of experimental arthritis fail to detect, visualize, and quantify early inflammation and disease activity. Here, we describe the use of an injectable MMP-activated fluorescence agent forin vivoquantification of acute inflammation produced by collagen-antibody-induced arthritis (CAIA) in CC chemokine receptor-2 (Ccr2−/−) null mice. AlthoughCcr2−/−DBA1/J mice were highly susceptible to and rapidly developed CAIA, the standard clinical assessment of fore or hind paw thicknesses was unable to detect significant acute inflammatory changes (days 3–10). Remarkably, noninvasive,in situ, MMP-activatable fluorescent imaging ofCcr2−/−DBA1/J mice with CAIA displayed acute joint pathology in advance of clinically measurable acute inflammation (days 5, 7, and 10). These results were confirmed by the histology of ankle joints, which showed significant inflammation, bone loss, and synovial hyperplasia, compared to control mice at postimmunization day 5. The MMP-mediated fluorescence technique holds tremendous implications for quantifiable examination of arthritis disease activity of acute joint inflammation.
Effect of Growth Regulators on In Vitro Morphogenic Response of Boscia senegalensis (Pers.) Lam. Poir. Using Mature Zygotic Embryos Explants
Authors: Daffalla Hussien H. , Abdellatef Eltayb , Elhadi Elsadig A. , Khalafalla Mutasim M.
Published: June 2011

The percent study describes the in vitro responses of mature zygotic embryos of Boscia senegalensis to different concentrations (0.0–5.0 mg/L) of 6-benzyladnine (BA), Thidiazuron (TDZ), α-Naphthalene acetic acid (NAA), and 2, 4-Dichlorophenoxyacetic acid (2, 4-D) supplemented on Murashige and Skoog medium (MS). The plant growth regulators (PGRs) were considerably affected the morphogenetic responses. BA produced adventitious shoots through two ways: direct organogenesis and auxiliary shoot formation. Both 2, 4-D and TDZ tend to produce callus, whereas NAA improve the development of embryos to seedlings. Maximum number of shoots/explant (14.8 ± 0.6) was obtained on MS medium supplemented with 3.0 mg/L BA. 67.0% of excised shoots were rooted either on 1/2 MS medium augmented with or without 0.25 mg/L IBA. The highest number of roots (1.2 ± 0.4) and root length (0.5 ± 0.2 cm) was produced on 0.25 mg/L IBA-containing medium. Regenerated plants were successfully acclimatized and transferred to the green house with 70% survival rate. All the plants appeared morphologically uniform with normal growth pattern. A rapid (30 days), efficient and without subculturing protocol for in vitro regeneration of B. senegalensis was developed.
In VitroImmune Competence of Buffaloes (Bubalus bubalis) of Different Production Potential: Effect of Heat Stress and Cortisol
Authors: Mukherjee Joydip , Pandita Sujata , Huozha Ruokuobeinuo , Ashutosh Manju
Published: June 2011

Twelve healthy lactating Murrah buffaloes of similar parity (3rd) between 90 and 120 days of lactation, selected from the herd of National Dairy Research Institute (Karnal, India) and maintained at managemental practices as followed at the Institute they were included in this experiment. The animals were divided into two groups based on their production level in previous lactation. The average milk production level of group 1 and II was 9.3 and 6 lit/day, respectively. Blood was collected from these buffaloes on three occasions 10 days apart. The lymphocytes were separated and cultured in RPMI 1640 medium with PHA-P for 24 h at 37°C in a humidified CO2incubator (95% air and 5%  CO2). The lymphocyte responsiveness was also evaluated in response to thein vivoheat stress andin vitrocortisol. Mitogen-induced stimulation index was not affected by production level (). Stimulation index was significantly reduced () in both the groups when cortisol was added at 2.0 ng level in the culture. However, in heat-stressed buffaloes stimulation index did not vary despite increasing levels of cortisol, thus indicating that lymphocyte may become cortisol resistant during periods of acute heat stress. The results showed that lymphocyte proliferation response can be effectively used to study buffalo cell-mediated immunityin vitro.
Fluorescent Analysis of the Cell‐Selective Alzheimer′s Disease Aβ Peptide Surface Membrane Binding: Influence of Membrane Components
Authors: Simakova Olga , Arispe Nelson J.
Published: June 2011

We performed a fluorescent analysis of the binding of Aβ to the surface membrane of different types of cells lines such as PC12, GT1‐7, and ex vivo neurons. Analyses were performed on sorted cells with membrane bound Aβ Competitive binding between Aβ phosphatidyl serine‐ (PtdSer‐) specific binder annexin V and an anti‐PtdSer antibody provided compelling data confirming the involvement of PtdSer as one of the surface membrane signal molecules for Aβ. We found that populations of cells that exhibited high surface membrane binding affinity for Aβ also show higher membrane cholesterol levels compared to cells that did not bind Aβ. This direct relationship was upheld in cholesterol‐enriched or cholesterol‐depleted cell membranes. We conclude that the initial process for the cell‐selective binding by Aβ, to later conversion of elemental Aβ units into larger structures such as fibrils or to the potentially toxic ion channel aggregates, is highly influenced by the membrane content of PtdSer and cholesterol in the cell surface membrane.
First Variation Formula in Wasserstein Spaces over Compact Alexandrov Spaces
Authors: Gigli Nicola , Ohta Shin-Ichi
Published: June 2011

We extend results proved by the second author (Amer. J. Math., 2009) for nonnegatively curved Alexandrov spaces to general compact Alexandrov spaces X with curvature bounded below. The gradient flow of a geodesically convex functional on the quadratic Wasserstein space ((X),W2) satisfies the evolution variational inequality. Moreover, the gradient flow enjoys uniqueness and contractivity. These results are obtained by proving a first variation formula for the Wasserstein distance.
On Zindler Curves in Normed Planes
Authors: Martini Horst , Wu Senlin
Published: June 2011

We extend the notion of Zindler curve from the Euclidean plane to normed planes. A characterization of Zindler curves for general normed planes is given, and the relation between Zindler curves and curves of constant area-halving distances in such planes is discussed.
Sharp Inequalities for Differentially Subordinate Harmonic Functions and Martingales
Authors: Osękowski Adam
Published: June 2011

We determine the best constants Cp,∞ and C1,p, 1 < p < ∞, for which the following holds. If u, v are orthogonal harmonic functions on a Euclidean domain such that v is differentially subordinate to u, then

In particular, the inequalities are still sharp for the conjugate harmonic functions on the unit disc of ℝ2. Sharp probabilistic versions of these estimates are also studied. As an application, we establish a sharp version of the classical logarithmic inequality of Zygmund.
Evaluation of Highly Alloyed Stainless Materials for CO2/H2S Environments
Authors: Asphahani A. I.
Published: June 2011

Martensitic, autstenitic, ferritic-austenitic, and high-nickel stainless steels and high-iron, nickel-base alloys are tested for their resistance to localized corrosive attack and to stress corrosion cracking in media containing chloride, saturated with CO2/H2S gas. Several testing environments are used in order to simulate service applications in deep H2S wells, deep CO2 wells, and enhanced recovery by CO2 injection. The alloys' performances are compared at different strength levels (0, 20, and 50% cold work), and the effects of temperature and CO2/H2S content are examined. The overall resistance of each class of alloys is outlined. Furthermore, within the same class of alloys, the differences are described with respect to localized corrosion and to stress corrosion cracking resistance.
Breakdown of Oxide Films on Steel Exposed to Chloride Solutions
Authors: Townsend H. E. , Cleary H. J. , Allegra L.
Published: June 2011

Breakdown of the thin air-formed oxide film is the first step in the corrosion of steel exposed to aqueous chloride environments. We studied oxide-film breakdown by observing changes, with time, of appearance, weight loss, and corrosion potential while varying the three components of the system: environment, substrate, and film. Environment was varied by changes in chloride and hydrogen peroxide concentrations. Low carbon steel, stainless steel, aluminum, and titanium substrates were studied. Various types of crystalline oxide film were applied to steel substrates by RF sputtering. The results of this work demonstrated that the chemical and electronic properties of the oxide film on steel are inconsequential in determining whether film-breakdown will occur. We interpret these results in terms of a film-breakdown mechanism in which substrate dissolution begins at film defects and spreads, thus causing removal of the film by undercutting. According to this model, the ability of the substrate to spontaneously reform a stable oxide and repair the film determines resistance to film-breakdown.
An Auger Electron Spectroscopic Study of Phosphorus Segregation in the Grain Boundaries of Nickel Base Alloy 600
Authors: Guttmann M. , Dumoulin Ph. , Tan-Tai Nguyen , Fontaine P.
Published: June 2011

The grain boundary composition of nickel base alloy 600 has been studied by means of Auger electron spectroscopy. After being cathodically charged with hydrogen in a water saturated salt bath at 200 C, all the specimens could be intergranularly fractured in the Auger chamber. Phosphorus was the only element found to segregate at the grain boundaries of the two materials studied in all conditions of heat treatment considered; sulfur appeared essentially as a contaminant, which built up on the surfaces after fracture. The segregation of P was shown to be of the equilibrium (McLean) type, whereas Si did not segregate appreciably to the grain boundaries. The results, discussed in connection with published corrosion and stress corrosion data, explain the influence of P and the virtual absence of influence of Si on the sensitivity of alloy 600 to intergranular corrosion in HNO3 + Cr6+ solutions. They also indicate that the segregation of P is not the cause of intergranular stress corrosion cracking of this alloy in pure water and caustic environment, and that hydrogen embrittlement is very unlikely to be the mechanism of this phenomenon.
Dependence of Corrosion Fatigue Crack Initiation Mechanisms on the Corrosion Behavior of Two Stainless Chromium Steels
Authors: Mueller Matthias P.
Published: June 2011

Corrosion fatigue experiments have been carried out in a 0.5N and 4N sodium chloride solution with pH of 6.5 at 80 C. The solution has been air saturated. Two different chromium steels were examined, a tempered martensitic steel with 12% chromium and a pure ferritic steel with 18% chromium and 2% molybdenum. The results of this investigation showed that the corrosion fatigue crack initiation mechanisms are directly related to the type of corrosion attack. Under pitting corrosion conditions, a pronounced decrease in fatigue limit has been measured. Under passive corrosion conditions, a corrosion fatigue limit exists, which could be related to the thickness of the passive surface film and the surface slip characteristics of the alloy. It has been shown that under passive corrosion conditions, the corrosion fatigue limit cannot be lower than the cyclic yield strength of the material. Nonmetallic inclusions were found to play an important role in corrosion fatigue crack initiation. In the 12% chromium steel, sulfide inclusions acted as pit initiation sites. Chemically inert niobiumcarbonitrides in the 18% chromium steel induced local corrosion attack, but only under corrosion fatigue conditions in the 4N sodium chloride solution.
Hydrogen Embrittlement Behavior of the Amorphous Alloy Fe32Ni36Cr14P12B6
Authors: Tong H. S. , Macur J. E.
Published: June 2011

Room temperature hydrogen embrittlement behavior of the amorphous alloy Fe32Ni36Cr14P12B6 was studied under various conditions. Hydrogen charging was performed in a 1N H2SO4 solution at a current density of 10 mA/cm2 and hydrogen embrittlement susceptibility was determined using the constant extension rate technique at an extension rate of 5.0×10−4 cm/S. The fracture stress decreased significantly on the hydrogenized specimen. However, recovery of this fracture stress was observed as a function of degassing time at room temperature. The fracture morphology of the specimens with/without hydrogen charging was also studied.
Evaluation of Corrosion Behavior of Coated Metals with AC Impedance Measurements
Authors: Mansfeld F. , Kendig M. W. , Tsai S.
Published: June 2011

AC impedance measurements have been performed in 0.5 N NaCl for coated steel and aluminum alloys which had been subjected to different surface treatment procedures. These procedures included phosphating for steel and exposure to a conversion coating for the Al alloys. A polybutadiene coating of 8 ± 2 μm thichness was applied by spin coating. The AC impedance measurements made it possible to follow the penetration of electrolyte into the coating and to detect the initiation of corrosion at the metal/coating interface. A general model has been used to analyze the impedance data in terms of reactions occurring during the interaction of the coated metals with the environment. Based on this analysis the different pretreatment procedures have been ranked in terms of their efficiency in providing corrosion protection by the organic coating. A comparison between impedance results and visual observation over several days of the corroded and the delaminated areas under the coating confirm that AC impedance data can be used to characterize organic coating/metal systems.
Permeation of Hydrogen, Trapping, and Damage in Spheroidized AISI 1090 Steel
Authors: Xie S. X. , Hirth J. P.
Published: June 2011

Spheroidized AISI 1090 steel was electrolytically charged with hydrogen from a 1 normal sulfuric acid solution containing a recombination poison. Permeation, trapping and damage effects were studied as a function of cold work, charging current density, and time. Irreversible damage, manifested as void formation, was found to occur at a critical charging current density which decreased with increasing cold work. Voids formed when the hydrogen fugacity was sufficient to cause void growth by plastic deformation. Effects of microstructure were found to be similar to those in prior work using gas phase permeation techniques.
Erosive Wear of Advanced Ceramics in Coal-Slurry Streams
Authors: Shetty D. K. , Wright I. G. , Clauer A. H. , Peterson J. H. , Merz W. E.
Published: June 2011

Erosive wear of advanced ceramics and cemented carbides was evaluated in a coal-slurry jet test that simulates the conditions in letdown valves in liquefaction plants. The results indicate that some ceramics, notably those based on SiC, possess superior wear resistance as compared to the cemented carbides. The paper discusses the influence of the microstructures and the physical properties of the target materials on their relative susceptibility to erosive wear.
A Study of Zircaloy-2 Corrosion in High Temperature Water Using Ion Beam Methods
Authors: Woolsey I. S. , Morris J. R.
Published: June 2011

Corrosion experiments have been carried out on Zircaloy-2 specimens in water at 355 C to study the transport of oxygen and hydrogen (as deuterium) in growing corrosion films. The transport behavior was studied by using O18 and deuterium labelled water, and analyzing the corrosion films for these isotopes by the use of ion beam induced nuclear reactions. Analysis for O18 was performed by means of the O18 (p,α)N15 reaction, using incident 850 and 950 keV protons. The analyses for deuterium were made using the D(He3,d)p reaction employing incident 850 and 1300 keV He3 ions, and detecting the scattered α-particles. The composition of the corrosion films was also examined in 2.9 MeV and 3.9 MeV α-particle backscattering experiments. From these studies, it was concluded that the corrosion of Zircaloy-2 in high temperature water occurs predominantly by oxygen diffusion through the corrosion film via grain boundary or similar short circuit diffusion paths, to form fresh oxide at the oxide metal interface. The diffusivity of oxygen through the pre-breakaway films decreased with time as a result of a decrease in the available easy diffusion paths as the oxide aged. This was interpreted as the primary cause of the subparabolic kinetics normally observed prior to the rate transition during high temperature aqueous corrosion of Zircaloy-2. There was also evidence that increasing grain size deeper within thick pre-breakaway films contributes to the decrease in oxygen diffusivity. The oxygen transport behavior in post-breakaway corrosion films indicates that the rate transition results from the generation of new diffusion pathways in previously protective oxide. Unexpectedly high concentrations of deuterium were observed in the corrosion films. These were about 4.5% atomic at the oxide surface, falling to 1 % atomic at depths between 1 and 1.5 μm. The deuterium was also found to be highly mobile within the oxide, much more so than oxygen.
Effect of Steam Impurities on Corrosion Fatigue Crack Growth Rates of a Turbine Disc Steel
Authors: Rungta R. , Begley J. A. , Staehle R. W.
Published: June 2011

Corrosion fatigue crack growth studies have been conducted on a Ni-Cr-Mo-V turbine disc steel in saturated sodium chloride and sodium sulfate environments at 100C. The results show that crack growth rate is accelerated in both the environments at open circuit potential, compared to the rate in air environment. Crack growth rate is further accelerated in both environments with the application of a large cathodic potential. Anodic potential has no effect on crack growth rate relative to that at open circiut potential. Cracking occurred transgranularly around the open circuit potential and intergranularly under severe cathodic charging conditions. The amount of intergranular cracking increased with decreasing frequency in the Cl− environment and occurred predominantly at low ΔK levels. It is suggested that the material cracks by two mechanisms: hydrogen embrittlement at very cathodic potentials, and film rupture and anodic dissolution at relatively noble potentials around the open circuit potential. Finally, comparison of the results with those for concentrated sodium hydroxide (100 C) and double distilled water (97 C) shows that although sodium hydroxide (which is another impurity present in the steam) is the most aggressive specie, distilled water inhances cracking as well. It is recommended that further work be done in high purity water.
Oxide Scale Formation on Iron-Chromium Alloys in Elevated Temperature Air Environments
Authors: Fabis P. , Heidersbach R. , Brown C. , Rockett T.
Published: June 2011

Oxide scales formed on metals at elevated temperatures may be different, both chemically and structurally, from the scales on the metal once it has cooled to room temperature. This paper discusses Raman spectroscopy instrumentation for the in-situ identification of scales formed on metal surfaces exposed to gaseous environments. The results of an experimental program to characterize scales formed on two commercial iron-chromium alloys, AISI 446 and 502, in air and oxygen environments are also presented.
The Performance of Zirconium Alloys in Sulfide Solutions
Authors: Yau Te-Lin
Published: June 2011

Zirconium Grades R 60702, R 60704, and R 60705 were investigated for deep sour gas well applications. Test methods include autoclave, constant strain, sustained load, and constant strain rate techniques. Test results indicate that these alloys have excellent resistance to general corrosion and to stress corrosion cracking in sulfide environments. No cracking was detected in all grades of zirconium in 5% NaCl + 0.5% CH3COOH + saturated H2S at room and boiling temperatures. Hydrogen sulfide seems to play a neutral role in the corrosion reactions of zirconium because of zirconium's low affinity for sulfur.
Comparison of Several Accelerated Laboratory Tests for the Determination of Localized Corrosion Resistance of High-Performance Alloys
Authors: Manning P. E.
Published: June 2011

Results of immersion pitting, immersion crevice, and slow scan potentiodynamic pitting tests are compared to assess the relevance of particular types of accelerated laboratory tests for localized corrosion. The alloys examined include 317 L, 20-type alloys, duplex stainless steels, and nickel-base alloys. The solutions utilized are acid chloride-type with and without ferric ions [Fe2(SO4)3] as an oxidizing species. The acids examined include sulfuric, hydrochloric, and mixtures of these two acids. The best accelerated test for rating localized corrosion resistance of alloys is the immersion pitting temperature test. Results from this test procedure best simulate and correlate with the service performance of alloys.
Stress Corrosion Cracking Characterization of 3.5 NiCrMoV Low Pressure Turbine Rotor Steels in NaOH and NaCl Solutions
Authors: Lyle Fred F.
Published: June 2011

This paper describes a research program conducted to determine susceptibility of steels used in low pressure (LP) turbine rotors of power plants to stress corrosion cracking (SCC) in LP turbine environments. Slow strain rate SCC tests were conducted on samples from two 3.5 NiCrMoV rotor forgings over a temperature range of 38 to 204 C (100 to 400 F). Environments employed included pure NaOH solutions, 3.5% NaCl, pure water, and mixtures of NaOH and NaCl, Na2S, Na2SO4, or CuO. Supplementary electrochemical data also were generated. Test results indicate that the minimum NaOH concentration required to produce detectable SCC decreases with increasing temperature. Addition of small amounts of NaCl reduced the concentration of NaOH necessary to produce SCC at 157 C (315 F). Pure 3.5% NaCl induced SCC at 121 C (250 F). SCC was not detected in either steel in tests in pure water at 157 C (315 F).
The Anodic Dissolution of a Ni-Base Superalloy
Authors: Cavanaugh M. A. , Kargol J. A. , Nickerson J. , Fiore N. F.
Published: June 2011

A single phase nickel base superalloy, HASTELLOY Alloy C-276, was anodically polarized in 0.5 N NaCl at 70 C, and the concentrations of metal-ion complexes in solution were determined. Relative dissolution rates of alloying elements were obtained and selectivity coefficients were calculated. The corrosion products that formed at high anodic potentials were identified as FeCl2+, Ni2+, HCrO4−, and MoO42−. The pH was observed to decrease and the chloride ion concentration to increase in the electrolyte when diffusion of corrosion products out from an occluded region at the alloy surface was restricted. The increased hydrogen ion concentration in the occluded region was explained by the formation of molybdate and chromate ions as corrosion products. The high corrosion resistance of Alloy C-276 in chloride may be related to the formation of corrosion-inhibiting molybdate ion.
Electrochemical Behavior of Steel in Salt Contaminated Concrete: Part 1
Authors: Dehghanian Changiz , Locke Carl E.
Published: June 2011

Corrosion of steel in concrete is a problem because of the presence of chloride ions at the metal-concrete interface. The chloride ion is introduced as a contaminant in the mix or from the sources such as deicing salt or seawater. The electrochemistry of steel in this system is not well defined. This paper presents the polarization curves for steel in Type I and V portland cement with various salt contents. The degree of corrosiveness of steel in these two portland cement concretes was evaluated. Laboratory-dry and water-saturated concrete samples were used to determine the electrochemical behavior of steel at the presence of chloride ions in these conditions. The anodic polarization curves indicated that the steel passivates in the concrete sample of Type I portland cement with the salt content up to 0.1 %, but the passivity of steel was maintained up to 0.5% in Type V portland cement. (The samples had been exposed to distilled water for 90 days after removal from a water cabinet). The anodic polarization curves indicated no passivity for the samples exposed to the dry condition of the laboratory.
An Electrochemical Investigation of Localized Corrosion on Titanium in Chloride Environments
Authors: Mckay P. , Mitton D. B.
Published: June 2011

Electrochemical methods have been used to study the crevice and pitting corrosion behavior of unalloyed titanium in chloride solutions at elevated temperatures (maximum 150 C). The investigation was focused primarily on crevice corrosion. The techniques which were used included simultaneous measurement of the corrosion potential-time behavior of plain and creviced specimens, controlled anodic polarization of creviced specimens (both potentiostatic and potentiodynamic methods), and the measurement of the current and the potential of galvanic cells formed between creviced specimens and large uncreviced areas of titanium. The data obtained under both controlled and freely corroding conditions were interpreted using an electrochemical mechanism of crevice corrosion on titanium in chloride solutions. The degree of anodic polarization in the crevice, produced either potentiostatically or naturally by galvanic coupling, was shown to have a major effect on the kinetics of crevice corrosion initiation and propagation. The distribution of the cathodic reaction between reduction of O2 on the external surface and H+ reduction in the crevice was evaluated. The concept of a critical crevice pH for initiation of crevice corrosion was used to explain the differences between these results and those of other published studies for the critical temperatures and chloride concentrations necessary for initiation of crevice corrosion on unalloyed titanium.
Passivation of Titanium by Molybdate Ion
Authors: Glass Robert S.
Published: June 2011

The passivating effect of molybdate ion on the corrosion of titanium in deaerated, boiling 1N H2SO4 has been explored. In this medium, in the absence of molybdate ion, titanium rapidly corrodes. An immediate passivation process for Ti is observed when Mo+6 at a concentration as low as 3 mM is added to an H2SO4 solution in which Ti is actively corroding. The open circuit potential attained for Ti in molybdate solution is shown to be controlled by redox processes. Through a combination of surface analytical and electrochemical data, it is shown that upon immersion of Ti in acidic molybdate solution, the native TiO2 oxide is replaced by a salt film containing Mo. This film is adherent when a passivated electrode is transferred to a molybdate-free solution, and it provides a corrosion resistant barrier.
The Effect of Thermal Treatments on Stress Corrosion Cracking of Alloy-800 in a Caustic Environment
Authors: Pathania R. S. , Cleland R. D.
Published: June 2011

Stress corrosion cracking (SCC) tests under controlled potentials were conducted on plastically stressed C-rings of Alloy-800 to evaluate the effect of thermal treatments (at 500 to 850 C) on SCC of Alloy-800 steam generator tubing. The tests were conducted in a caustic solution at 300 C; such alkaline environments may sometimes form in crevices in nuclear steam generators. The results are presented in the form of a time-temperature-SCC diagram.

Thermal treatments generally inhibited the SCC of Alloy-800, and the improvement was substantial in a few cases. Application of anodic potential and increasing stress generally accelerated SCC.
Stress Corrosion Cracking Susceptibility of AISI 316 NG and 316 Stainless Steel in an Impurity Environment
Authors: Maiya P. S. , Shack W. J.
Published: June 2011

The relative stress corrosion cracking (SCC) susceptibility of heat-treated AISI 316 nuclear grade (NG) and 316 stainless steel (SS) has been investigated by means of constant extension rate tensile (CERT) tests over a range of strain rates from 10−5 to 10−7 s−1 in simulated boiling water reactor (BWR) environments that contain SO42− as an impurity. It is observed that although AISI 316 NG SS is extremely resistant to intergranular SCC (IGSCC) even when subjected to severe heat treatments, it can become susceptible to transgranular SCC (TGSCC) in the presence of impurities. Sensitized AISI 316 SS, however, is susceptible to IGSCC even in high-purity water containing 0.2 ppm O2, and the addition of an impurity aggravates the IGSCC susceptibility. The SCC results obtained for both materials are discussed in terms of a phenomenological model that incorporates a slip-dissolution mechanism and elastic-plastic fracture mechanics. The results for both IGSCC and TGSCC are demonstrated to be consistent with the slip-dissolution model of Ford.
Pitting Corrosion of Inconel 600 in High-Temperature Water Containing CuCl2
Authors: Park J. R. , Szklarska-Smialowska Z.
Published: June 2011

Pitting corrosion of Inconel 600 was studied in aqueous sodium and cupric chloride solutions at 60 and 280 C. The pit nucleation potential, Enp, was evaluated in two different concentrations of sodium chloride. Enp decreased with increasing concentrations of the chloride ion and with temperature. On specimen surfaces exposed to cupric chloride solutions, pitting occurred at open circuit potentials nearly equal to or higher than the Enp determined by anodic polarization in 0.01 M NaCl solution. The number and size of the pits increased with increasing concentrations of cupric chloride and dissolved oxygen. On specimens partly covered with polytetrafluorethylene (PTFE) tape (i.e., in the presence of artificial crevices), pitting occurred more easily at low concentrations of CuCl2 (≤ 20 ppm CuCl2 in deaerated solutions at 280 C). Tubes covered with oxide films that formed during the operation of model boilers exhibited greater pitting resistance than tubes with clean surfaces at 280 C, but less resistance at 60 C. Corrosion products contained in the pits were enriched in chromium with small amounts of copper, sulfur, and chlorine. The composition of corrosion products covering the pits was similar to that in the pits, but with the additional enrichment of iron. Presumably, sulfur present in Inconel 600 as an impurity was significant in the pitting process. The probable mechanism of the processes leading to pitting of Inconel 600 tubing in high-temperature water is discussed.
Corrosion Behavior of 18-8 Stainless Steels in Hot Concentrated Caustic Soda Solutions under Heat-Transfer Conditions
Authors: Yasuda M. , Tokunaga S. , Taga T. , Hine F.
Published: June 2011

The corrosion behavior of AISI 304 and 316 stainless steels (SSs) in hot concentrated caustic soda solutions was investigated under heat-transfer conditions. The corrosion potential of the specimens was located in the active region; thus, the alloys were attacked in the form of general corrosion, depending on the heat-transfer conditions. AISI 316 was more susceptible than AISI 304. Such corrosion behavior is attributed to the failure of the passive film on the heated surface, caused by concentration of caustic solution next to the metal surface and erosion by gas bubbles. A molybdenum-free alloy, AISI 305J1, was tested under the same conditions as AISI 316 to clarify the detrimental effect of Mo on austenitic SS corrosion in hot concentrated NaOH. Intergranular corrosion was occasionally found when the potential was located in the passive region, depending on test conditions and heat treatment of the specimens.