Evaluation of an unusual superheated steam pipe failure

An examination has been made of a steam generator outlet pipe that failed locally after some 100,000 h of operation. Failure took place by cracking along preferentially formed lines (or planes) of graphite nodules. Grain boundary decohesion and void formation ahead of the crack tips were very local in nature, voids being formed very close to the propagating cracks only. The graphitization is concluded to have occurred locally because of inhomogeneity in carbon content.     

Influence of silica and black rice husk ash fillers on the diffusivity and solubility of gases in silicone rubbers

The preparation of elastomeric compositions based on poly(methylvinyl siloxane) using silica and rice husk ash as fillers is reported. Permeation of oxygen, nitrogen, carbon dioxide and methane across the compositions was measured in the temperature interval 30-60° C under upstream pressures lying in the range 15-76 cm Hg. Permeation and diffusion coefficients were independent on the upstream pressure but both parameters were thermal activated processes described by the Arrhenius equation. It was found that the activation energy associated with the diffusion process is larger in the filled than in the unfilled rubbers. The results also showed that the fillers enhance gas solubility in polysiloxane compounds in such a way that in most situations the sorption process is exothermic. The analysis of the solubility and diffusivity of gases in the rubbers suggests very good adherence matrix-fillers that hinder micro-Brownian motions thus impeding the normal development of non-permanent holes through which the diffusive particles can easily jump. Neither the proportion nor the nature of the fillers alters the permselectivity characteristics of polysiloxane based compounds.     

Differentiation in the fertility of Inceptisols as related to land use in the upper Solimões river region, western Amazon

The Upper Solimões river region, western Amazon, is the homeland of indigenous populations and contains small-scale agricultural systems that are important for biodiversity conservation. Although traditional slash-and-burn agriculture is being practiced over many years, deforestation there is relatively small compared to other Amazon regions. Pastures are restricted to the vicinity of cities and do not spread to the small communities along the river. Inceptisols are the main soil order (>90%) in the area and have unique attributes including high Al content and high cation exchange capacity (CEC) due to the enrichment of the clay fraction with 2:1 secondary aluminosilicates. Despite its importance, few studies have focussed on this soil order when considering land use effects on the fertility of Amazon soils. Thus, the objective of this study was to evaluate changes in soil fertility of representative land use systems (LUSs) in the Upper Solimões region, namely: primary rainforest, old secondary forest, young secondary forest, agroforestry, pasture and agriculture. LUSs were significantly differentiated by the chemical attributes of their topsoil (0-20 cm). Secondary forests presented soil chemical attributes more similar to primary rainforest areas, while pastures exhibited the highest dissimilarity from all the other LUSs. As a whole, soil chemical changes among Inceptisols dominated LUSs showed patterns that were distinct from those reported from other Amazon soils like Oxisols and Ultisols. This is probably related to the presence of high-activity clays enriched in exchangeable aluminum that heavily influenced the soil chemical reactions over the expected importance of organic matter found in most studies conducted over Oxisol and Ultisol.     

Immune response and protection in mice inoculated with Leishmania amazonensis clones expressing different degrees of virulence

The induction of protective immunity to Leishmania amazonensis was investigated by injection of parasite clones of low and medium virulence into susceptible mice. To this end, L. amazonensis were cloned by limiting dilution and the clones' virulence was evaluated by the course of infection in susceptible mice. Clones originally derived from the spleen showed virulence variations in comparison with that of the parental population (PP) of parasites. Two low-virulence clones (SP 5 and SP 20) and one medium-virulence clone (SP 11), representative of the spectrum of derived clones, were compared with virulent parasites and with an avirulent strain (Josefa) as to their ability to induce T-cell immune responses and to protect BALB/c mice from infection with the virulent L. amazonensis PP. Clone SP 20 and clone SP 11 induced partial protection when injected by the intravenous and intradermal route, respectively. The avirulent Josefa strain induced neither T-cell responses nor protection. Low-virulence L. amazonensis clones can therefore be additional tools in vaccine investigation.     

Metallography in life assessment of power plants

This report discusses the application of metallographic techniques in evaluating power plant components for integrity, continued service, and estimation of remaining safe life. Some of the pitfalls that may arise and the limitations to the methods of evaluation are discussed, and several specific cases are presented where metallography has been used to evaluate failures and to provide recommendations concerning future safe operation.     

Inhibitory effect of oxygen on hydrogen‐induced fracture of A333 pipe steel

The effect of oxygen contained in hydrogen gas environment as an impurity on hydrogen environment embrittlement (HEE) of A333 pipe steel was studied through the fracture toughness tests in hydrogen gases. The oxygen contents in the hydrogen gases were 100, 10, and 0.1 vppm. A significant reduction in the J‐Δa curve was observed in the hydrogen with 0.1‐vppm oxygen. Under given loading conditions, the embrittling effect of hydrogen was completely inhibited by 100 vppm of oxygen. In the case of the hydrogen with 10‐vppm oxygen, initially the embrittling effect of hydrogen was fully inhibited, and then subsequently appeared. It was confirmed that 1‐vppm oxygen reduced the embrittling effect of hydrogen. The results can be explained by the predictive model of HEE proposed by Somerday et al.     

Electromagnetic Spectrum Contribution in Astronomy,Health, Atmospheric,Geology and Environment Applications

International Journal of Wireless Information Networks - Spectrum technologies are shaping the way our world connects, communicates, and functions. Radio nodes connect through a nearly ubiquitous...     

A Low-Voltage Wide-Swing Programmable-Gain Current Amplifier

A CMOS low-voltage, wide-swing continuous-time current amplifier is presented. Exhibiting an open-loop architecture, the circuit is composed of transresistance and transconductance stages built upon triode-operating transistors. In addition to an extended dynamic range, the current gain can be programmed within good accuracy by a rapport involving only transistor geometries and tuning biases. Low temperature-drift on gain setting is then expected. In accordance with a 0.35 μm n-well CMOS fabrication process and a single 1.1 V-supply, a balanced current-amplifier is designed for a programmable gain-range of 6–34 dB and optimized with respect to dynamic range. Simulated results from PSPICE and Bsim3v3 models indicate, for a 100 μA _pp -output current, a THD of 0.96 and 1.87% at 1 KHz and 100 KHz, respectively. Input noise is 120 pA√Hz @10 Hz, with S/N = 63.2 dB @1%-THD. At maximum gain, total quiescent consumption is 334 μW. Measurements from a prototyped amplifier reveal a gain-interval of 4.8–33.1 dB and a maximum current swing of 120 μA _pp . The current-amplifier bandwidth is above 1 MHz.