Friction stir welding of duplex stainless steels

Duplex stainless steels are successful in a variety of applications such as the food industry, petrochemicals and plants for desalination of seawater, where high corrosion resistance and high mechanical strength are required. However, the beneficial microstructure may change during fusion welding steps, and it can compromise the performance of these materials. Friction stir welding is a solid-state process avoiding typical problems concerning solidification such as solidification cracks, liquation and segregation of alloying elements. Superduplex stainless steels can avoid unbalanced proportions of ferrite and austenite, formation of secondary deleterious phases and grain growth of ferrite in the heat-affected zone. Consolidated friction stir welded joints with full penetration 6 mm thick were obtained for UNS S32101 and S32205 duplex and S32750 and S32760 superduplex stainless steels. The friction stir welds were submitted to tensile tests indicating an improvement of strength in welded joints, showing increased yield and tensile strength for all studied cases. Regarding the microstructural characterization, an outstanding grain refinement was observed in the welded joint, achieving grain sizes as small as 1 μm. This refinement was associated with the combination of microstructural restoration mechanisms in the dual-phase microstructure promoted by severe deformation associated with a high temperature during the welding process.     

Evaluation of susceptibility of hydrogen-induced cracking in micro-alloyed armour steel welds using a geometry-modified implant test

Susceptibility to hydrogen-induced cracking (HIC) was evaluated in steel welds for quenched and tempered armouring steel of 4.5 mm thickness. The welds were produced using the shielded metal arc welding process with low heat support and AWS E11018M 2.4 mm consumable. The susceptibility to HIC was evaluated by means of an implant test with modified geometry in welded joints with and without preheating being applied, using consumables in ideal stock conditions and exposed to the atmosphere. It was found that the consumable stock conditions were more relevant than preheating in regard to susceptibility to HIC.     

Effects of the model selected for the power curve on the site effectiveness and the capacity factor of a pitch regulated wind turbine

The present work is based on the fact that site effectiveness is a relevant value when analysing the suitability of a location for constant-speed wind turbines. An analytical expression is developed to calculate the said effectiveness by means of a potential adjustment model to the ascending segment of the power curve in pitch regulated wind turbines. Upon analysis of the results obtained for maximum effectiveness in a given location, using both the potential model and the quadratic model applied in earlier studies, no significant differences were observed in wind conditions of interest for wind energy applications. Notwithstanding, when the cut-in wind speed was compared, corresponding to the maximum effectiveness values at the same location according to the two models indicated, noticeable differences were observed. It can therefore be deduced that, when selecting this design parameter, a careful study should be made in order to determine which model best fits the power curve of the wind turbine under analysis for a specific location.     

Fuel use and design analysis of improved woodburning cookstoves in the Guatemalan Highlands

This study examined the fuel use and design of an improved woodburning cookstove (plancha), in comparison to traditional cooking over an open woodfire. These cookstoves had been randomly introduced into population households in the Guatemalan Highlands that had previously used open woodfires. This research consisted of: (1) a 12-household Kitchen Performance Test (KPT) over a 4-day period and (2) single-day participant observation in five households. The KPT monitored fuel consumption and the number, age, and gender of people who were cooked for, while the participant observation was used to form a complete understanding of fuel use patterns and to examine the influence of stove condition and cooking behavior. In spite of fairly low variability in the fuel use data (coefficients of variation of about 0.34) the KPT did not show statistically significant differences in fuel use between the two cooking methods. It is possible that increased study power through a larger sample size may have resulted in a statistically significant difference in favor of the plancha, but it is doubtful that the size of the effect would be of any practical significance. Thus, although other studies have shown that the plancha is extremely effective in reducing indoor air pollution in the study area, the KPT did not indicate that it offered any benefits with respect to fuel use. Practical and experimental recommendations for future cookstove efficiency studies are presented, with directions for continued work in this area.     

Equations to predict precipitation onset and bubblepoint pressures of asphaltenic reservoir fluids

A set of algebraic equations to predict upper onset‐of‐precipitation and bubble‐point pressures of asphaltene‐containing reservoir fluids in wide temperature ranges are proposed. In developing the equations, laboratory data of 11 Mexican and 12 more live oils have been analyzed, and a correlation of these data with temperature has been found. A modified least‐squares regression method has been used to develop two versions of the proposed equations. In one version, a single pressure/temperature data point is required to predict the entire onset/bubble‐point curves at any temperature. For oils with no experimental precipitation data available at all, a second version of the proposed expressions employs standard chromatographic data of the reservoir fluid to provide a reasonable prediction. The average absolute deviations in calculated onset and bubble‐point pressures by the proposed equations are 2.53 and 0.45MPa by the one‐point correlations, respectively, and 3.96 and 1.62 MPa by the compositionally‐based correlations, respectively. The developed expressions are simple and can be used to provide reasonable predictions of upper onset and bubble‐point pressures of asphaltenic live oils in cases where laboratory data are scarce. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

On the importance of calculating fresh-basis catalyst composition from spent catalyst analysis

The importance of expressing composition of used catalysts in fresh basis is highlighted in this work. Since catalysts are subject to changes during processing, e.g. coking and metal deposition, their composition varies depending on their state (fresh, spent, regenerated) and to properly determine catalyst life, composition needs to be changed to fresh-basis. Previous works are commented to demonstrate the current confusion existing in the literature when reporting metal content of used catalyst, and a simple approach is developed to change catalyst metal composition to fresh-basis.     

An optimal power flow plus transmission costs solution

This paper is aimed at the solution of the optimal power flow (OPF) problem with embedded security constraints (OPF-SC) by the particle swarm optimizer. The major objective is to minimize the overall operating cost while satisfying the power flow equations, system security, and equipment operating limits. The overall operating cost is composed by the generation cost, transmission cost, and the consumer benefit. A modification of the conventional particle swarm optimizer (PSO) has been used as the optimization tool, which uses reconstruction operators and dynamic penalization for handling constraints. The reconstruction operators allow the increase of the number of particles within the feasible region. The power equations mismatch, loss active power transmission, and voltages are calculated by the Newton–Raphson method. To demonstrate its robustness, the proposed algorithm was tested on systems from the open literature. Several cases have been studied to test and validate the proposed approach.     

SLH电源拓扑及其开环系统的负载适应性—SLH功率变换技术及应用(三)

在 “SLH 连载之一、二”从理论角度阐明开关线性复合(SLH)电源因高阻输出特性而获强鲁棒性的基础上，结合其典型拓扑的实践及效果，揭示了SLH开环系统对负载参数变化和多类负载呈现自适应能力的内在原因，廓清了相关学术概念，为 “连载之一、二”提供了实验依据。     

Immobilization of β-Glucosidase and Its Application for Enhancement of Aroma Precursors in Muscat Wine

Enzyme immobilization is becoming more widely practised in biotechnology because of the advantages that this method brings. In this study, commercial β-glucosidase for aroma released in winemaking was immobilized on diverse supports (alginate–chitin, chitosan–chitin) by using different methods. It was found that the most appropriate matrix was chitosan by adsorption and reticulation. The optimal immobilization conditions were pH 3.5, immobilization time 120 min, and concentration of cross-linker glutaraldehyde 0.25 %. Stability of the immobilized enzymes was assessed, which revealed a number of advantages, such as a lower enzyme dose required for immobilization (367 times lower than the free enzyme dose recommended by the manufacturer), high stability over time, and reusability. In vitro studies of cellobiose and in vivo studies of wine and aroma precursors isolated from grape must yielded similar outcomes with respect to enzyme hydrolysis of free and immobilized proteins.     

Posttraumatic stress disorder patients' readiness to change alcohol and anger problems.

Notes that recovery from combat-related posttraumatic stress disorder (PTSD) is often complicated by unacknowledged problems with alcohol and anger. 102 males combat veterans (aged 42–63 yrs) entering a residential PTSD rehabilitation program completed University of Rhode Island Change Assessment and process-of-change questionnaires based on J. O. Prochaska and C. C. DiClemente's transtheoretical model (TTM; J. O. Prochaska et al, 1992). Separate assessments were made for alcohol abuse and anger control. Four motivational subtypes were identified for both problems. Motivation to change alcohol problems was independent of that for anger. Relative to less-motivated peers highly motivated patients were more like to spontaneously identify alcohol or anger as problems in their life and made greater use of change strategies specified by the TTM. These results support extension of the TTM to anger management and to PTSD management. Treatment implications are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)