A unified constitutive model for asymmetric tension and compression creep-ageing behaviour of naturally aged Al-Cu-Li alloy

A set of unified constitutive equations is presented that predict the asymmetric tension and compression creep behaviour and recently observed double primary creep of pre-stretched/naturally aged aluminium-cooper-lithium alloy AA2050-T34. The evolution of the primary micro- and macro-variables related to the precipitation hardening and creep deformation of the alloy during creep age forming (CAF) are analysed and modelled. Equations for the yield strength evolution of the alloy, including an initial reversion and subsequent strengthening, are proposed based on a theory of concurrent dissolution, re-nucleation and growth of precipitates during artificial ageing. We present new observations of so-called double primary creep during the CAF process. This phenomenon is then predicted by introducing effects of interacting microstructures, including evolving precipitates, diffusing solutes and dislocations, into the sinh-law creep model. In addition, concepts of threshold creep stress σth and a microstructure-dependant creep variable H, which behave differently under different external stress directions, are proposed and incorporated into the creep model. This enables prediction of the asymmetric tension and compression creep-ageing behaviour of the alloy. Quantitative transmission electron microscopy (TEM) and related small-angle X-ray scattering (SAXS) analysis have been carried out for selected creep-aged samples to assist the development and calibration of the constitutive model. A good agreement has been achieved between the experimental results and the model. The model has the potential to be applied to creep age forming of other heat-treatable aluminium alloys

Host factors do not influence the colonization or infection by fluconazole resistant Candida species in hospitalized patients

Nosocomial yeast infections have significantly increased during the past two decades in industrialized countries, including Taiwan. This has been associated with the emergence of resistance to fluconazole and other antifungal drugs. The medical records of 88 patients, colonized or infected with Candida species, from nine of the 22 hospitals that provided clinical isolates to the Taiwan Surveillance of Antimicrobial Resistance of Yeasts (TSARY) program in 1999 were reviewed. A total of 35 patients contributed fluconazole resistant strains [minimum inhibitory concentrations (MICs) ≧ 64 mg/l], while the remaining 53 patients contributed susceptible ones (MICs ≦ 8 mg/l). Fluconazole resistance was more frequent among isolates of Candida tropicalis (46.5%) than either C. albicans (36.8%) or C. glabrata (30.8%). There was no significant difference in demographic characteristics or underlying diseases among patients contributing strains different in drug susceptibility

Complex event detection using semantic saliency and nearly-isotonic SVM

Copyright © 2015 by the author(s). We aim to detect complex events in long Internet videos that may last for hours. A major challenge in this setting is that only a few shots in a long video are relevant to the event of interest while others are irrelevant or even misleading. Instead of indifferently pooling the shots, we first define a novel notion of semantic saliency that assesses the relevance of each shot with the event of interest. We then prioritize the shots according to their saliency scores since shots that are semantically more salient are expected to contribute more to the final event detector. Next, we propose a new isotonic regularizer that is able to exploit the semantic ordering information. The resulting nearly-isotonic SVM classifier exhibits higher discriminative power. Computationally, we develop an efficient implementation using the proximal gradient algorithm, and we prove new, closed-form proximal steps. We conduct extensive experiments on three real-world video datasets and confirm the effectiveness of the proposed approach

They are Not Equally Reliable: Semantic Event Search Using Differentiated Concept Classifiers

© 2016 IEEE. Complex event detection on unconstrained Internet videos has seen much progress in recent years. However, state-of-the-art performance degrades dramatically when the number of positive training exemplars falls short. Since label acquisition is costly, laborious, and time-consuming, there is a real need to consider the much more challenging semantic event search problem, where no example video is given. In this paper, we present a state-of-the-art event search system without any example videos. Relying on the key observation that events (e.g. dog show) are usually compositions of multiple mid-level concepts (e.g. 'dog,' 'theater,' and 'dog jumping'), we first train a skip-gram model to measure the relevance of each concept with the event of interest. The relevant concept classifiers then cast votes on the test videos but their reliability, due to lack of labeled training videos, has been largely unaddressed. We propose to combine the concept classifiers based on a principled estimate of their accuracy on the unlabeled test videos. A novel warping technique is proposed to improve the performance and an efficient highly-scalable algorithm is provided to quickly solve the resulting optimization. We conduct extensive experiments on the latest TRECVID MEDTest 2014, MEDTest 2013 and CCV datasets, and achieve state-of-the-art performances

Studies on the expansion characteristics of the granular bed present in EGSB bioreactors

In this study, the expansion characteristics of an anaerobic granular bed in EGSB reactors based on terminal settling velocity study of the granules and the Richardson-Zaki equation (1954) have been investigated. The settling velocity study shows that the mean settling velocity of the granules is in accordance with the Allen formula because the settling process falls within the intermediate flow regime range (

Identification of five novel WASP mutations in Chinese families with Wiskott-Aldrich syndrome.

The Wiskott-Aldrich Syndrome (WAS) is an X-linked recessive immunodeficiency caused by mutation in the gene encoding WAS protein (WASP). The disease is characterized by eczema, thrombocytopenia and severe immunodeificency and is associated with extensive clinical heterogeneity. Mutation studies indicated that the mutated genotypes are also highly variable. In this study, we performed PCR-direct sequencing analysis of the WAS gene in six unrelated Chinese families. Five novel mutations identified, included two nonsense mutations (506C-->T, 1388-->T), a small insertion (685-686insCGCA) and two single-base deletions (384delT, 984delC). All of the mutations are predicted to lead to premature translational termination of WASP. Copyright 2002 Wiley-Liss, Inc.postprin

Water compatible resin for separation and recovery of dissolved precious metals

Trace Contaminants in Water: Genesis, Rapid Detection and Sustainable Removal Processes: abstract no. 353fOpen URL - http://apps.aiche.org/proceedings/Abstract.aspx?PaperID=119742The value of precious metals such as gold to be recovered in the industrial effluents within Pearl River Delta area is over HK$20 million per annual. Furthermore, with the expected tightening of environmental legislation and enforcement in the Mainland China, there is a growing need of effluent treatment technology. Traditionally, ion-exchange resin, polymer ultra-filtration and micro-emulsion are applied in the treatment of plating effluents. However, they all have different weaknesses. Many reports have been published for the separation using aqueous biphasic system. Based on this methodology, polystyrene-grafted-polyglycidol (PS-PG), a water-compatible polymer was synthesized. This type of polymer can be used for gold or silver extraction. After extraction, the recovery of metal can be achieved by direct electro-deposition or reverse extraction using sodium cyanide.postprintThe 2008 AIChE Annual Meeting (AIChE 100), Philadelphia, PA., 16-21 November 2008. In Conference Proceedings, 2008, p. 1-

Experimental studies and constitutive modelling of anelastic creep recovery during creep age forming

This paper presents a study of anelastic creep recovery during creep-ageing of an aluminium alloy AA7050-TAF. Uniaxial Creep-Ageing and Recovery Test (CART) was used to characterise the influence of anelastic creep strain on total creep deformation for determining the actual amount of springback in creep age forming (CAF) process. CART was performed on aluminium alloy AA7050-TAF at 174°C between the stress levels of 137.5 to 162.5 MPa. A constitutive model was developed for the prediction of the creep-ageing and recovery response of material in creep age forming. A 'back stress' variable was used to represent the net effect of the internal stresses of the material which causes anelastic creep recovery. Other microstructural variables were introduced to model complex micro-mechanisms and hardening effects including solid solution hardening, dislocation hardening, and age hardening. It has been found that the permanent strain after creep-ageing depends not only on total creep strain but also on anelastic strain. Simulation results from the constitutive model developed in this study show a good agreement with experimental data

Behavior of hybrid FRP-concrete-steel tubular columns : experimental and theoretical studies

2006-2007 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

An innovation approach on the separation of metal

There has been increasing environmental concerns on the metallic pollution in recent decades. The conventional technologies used for metal extraction are ion-exchange resins, polymer ultrafiltration and microemulsion. The whole extraction mechanism can be divided into 4 steps: 1) The binding of dissolved metal to active sites, 2) Separation of the metal load extractant from the lean phase, 3) Reverse extraction of loaded metal for recovery 4) Recycling of extractant for repeated extraction. Each of the conventional methods suffers different drawbacks in different steps of the extraction mechanism….postprintThe 2008 AIChE Annual Meeting (AIChE 100), Philadelphia, PA., 16-21 November 2008. In Proceedings of the 2008 AIChE Annual Meeting, AIChE 10