Modeling of Deformation Behavior and Dynamic Strain Ageing in ECAP

AbstractEqual channel angular pressing (ECAP) is a substantial process for producing ultra-fine grains in bulk metallic materials by means of severe plastic deformation. In this study, microstructure evolution through dynamic ageing characteristics associated with the application of ECAP to Al6061 alloy at high temperature was investigated. The behavior of the material under ECAP, including the dislocation density and cell size evolution as well as precipitation development, was modelled using dislocation density-based model. Followed by ECAP, microstructural observations were undertaken using EBSD. The experimental investigations showed that after two pass of ECAP, a large amount of subgrains with low angle grain boundaries appears in the original coarse grains. The simulated cell size was in good agreement with the experiment, particularly with the observed rapid decrease of the cell size during the second pass slowing down from the forth pass onwards

A new method of termination for heavy-duty synthetic rope fibres

Termination of heavy-duty synthetic fibre ropes has long been an issue of concern in marine environments. Recent serious rope accidents and new requirements for lighter ropes with better performance in mooring lines have encouraged industry to look for new methods for increasing line performance using existing ropes. One way of increasing rope performance is to use efficient methods for rope termination. This is why the main objective of this study has been to investigate a new method for rope termination. Rope failure usually happens inside or very close to termination due to high stress concentration areas. The new method, "The Vaseghi Stress Relief Socket", has been proposed to improve the high stress concentration areas inside sockets and move failure points along the rope. The new method has increasedthe tensile performance of existing ropes up to 13%. It should also be addedthat the ropes in this study are mainly used in marine environmentsfor mooring oil platforms. Considering the results of the tensile and cycling tests, The Vaseghi Stress Relief Socket, proved a great potential for replacement of existing methods of termination e.g. the splice. It should also be noted that the reproduction of the socket termination is more consistent than that of other methods of termination. Tensile properties of ropes using `The Vaseghi Stress Relief Socket' were initially a matter of concern, for rope termination is the most important feature of ropes.In fact, if there is a termination failure in tensile tests, the rope will not be considered efficient for mooring purpose even though its other performancesare excellent. Load cycling was the second property that was considered. Acoustic Emission monitoring was performed to find out the relation between the load-extension behaviour of the rope using The Vaseghi stress Relief socket and the AE signals. Finally, the finite element modelling of socket helped to investigate the stress concentration areas in the socket to optimise the amount of the reinforcing material and identify the weak point areas in the socket, which could lead to further research studies for new designs

Hygrothermal Performance Assessment of Wall Systems With Various Concrete and Insulation Configurations

The moisture performance of building envelope assemblies has always been a major concern of designers. Building envelope is constantly exposed to moisture loads such as exterior and interior humidity, rain, groundwater, snow and construction moisture. Therefore, it is critical to control the moisture migration mechanism within building envelope walls. Moisture accumulation occurs when the wetting potential of building envelope exceeds its drying potential due to applying inappropriate construction materials or configuration designs. Moisture accumulation in mid-rise and high-rise concrete buildings has negative impacts on microbial growth, occupants’ comfort, energy consumption, freeze thaw and compressive and tensile strength of concrete which lead to spent of millions of dollars on the repair in North America every year. Therefore, evaluation and prediction of moisture performance of building envelope components are important design factors that should be considered to minimize the risk of moisture accumulation in concrete buildings. In this paper, the hygrothermal performance of a number of concrete wall systems with various configuration of concrete and insulation are studied. The performance of these systems in wet and cold climates of Vancouver and Winnipeg are evaluated using a hygrothermal model. The water content of concrete layers and moisture fluxes at the interior and exterior surface layers are analysed and the overall performance of the systems as related to moisture storage and drying behaviour are determined. The results indicate that assemblies with thermal insulation placed on the exterior side of concrete have the highest hygrothermal performance while assemblies with concrete layer sandwiched between two wythes of thermal insulations have the poorest hygrothermal performance

Educational intervention in fostering L2 learner autonomy

There is not enough conceptual work done on autonomy relating it to other individual difference variables. Some researchers have investigated the characteristics of L2 English learners in terms of motivation and learning strategy constructs, but they did not include variables associated with learners' perceived L2 learning competence/anxiety. Some other researchers investigated the characteristics of L2 English learners in terms of strategy use and confidence constructs, but did not include motivational constructs. Motivational, affective, and strategy use have been hypothesized to be important in fostering L2 learner autonomy (Benson, 2011), but conceptual work linking these constructs to L2 learner autonomy is needed. The present study aims to identify the links among L2 learner motivation, confidence/anxiety, and strategy use with L2 English learners with varying degrees of L2 learner autonomy, measured with the Self-Determination Theory-based motivational continuum. The results will help to illuminate how autonomy is related to other variables and thereby provide a clearer understanding of L2 English learner autonomy. The second purpose is to investigate which of the above-mentioned constructs can be changed through a specific educational intervention. This is important given that positive changes in such variables are hypothesized to result in more positive educational outcomes. The study also aims to investigate how the participants perceive a set of learner autonomy fostering activities that aims at transferring learning responsibility from teacher to learner

Molecular barriers to direct cardiac reprogramming

Abstract Myocardial infarction afflicts close to three quarters of a million Americans annually, resulting in reduced heart function, arrhythmia, and frequently death. Cardiomyocyte death reduces the heart’s pump capacity while the deposition of a non-conductive scar incurs the risk of arrhythmia. Direct cardiac reprogramming emerged as a novel technology to simultaneously reduce scar tissue and generate new cardiomyocytes to restore cardiac function. This technology converts endogenous cardiac fibroblasts directly into induced cardiomyocyte-like cells using a variety of cocktails including transcription factors, microRNAs, and small molecules. Although promising, direct cardiac reprogramming is still in its fledging phase, and numerous barriers have to be overcome prior to its clinical application. This review discusses current findings to optimize reprogramming efficiency, including reprogramming factor cocktails and stoichiometry, epigenetic barriers to cell fate reprogramming, incomplete conversion and residual fibroblast identity, requisite growth factors, and environmental cues. Finally, we address the current challenges and future directions for the field

The effect of rope termination on the performance of polyester mooring ropes for marine applications

© 2019 Elsevier Ltd. All rights reserved. This manuscript is made available under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International licence (CC BY-NC-ND 4.0). For further details please see: https://creativecommons.org/licenses/by-nc-nd/4.0/Termination of heavy-duty polyester mooring ropes has long been an issue of concern in the marine renewable energy applications. In this study, experimental investigations were conducted on two different rope materials to investigate and compare the performance of filament, yarn, strand, sub-rope, 44 mm rope and 120 mm rope. The experiment setup consisted of 5 kN Instron Machine for testing filament, yarn and strand, 500 kN Denison Machine for sub-rope, 1500 kN and 30 MN tensile equipment for testing 44 mm and 120 mm ropes respectively. At constant test conditions, extensive experiments were carried out to examine the effects of various termination configuration on rope performance. The terminations used included Parafil socket (Viking 7 socket), splice and another novel termination called Stress Relief Socket. The results show that the use of stress relief socket has led to increased tensile performance of existing ropes by up to 13% for Akzo ropes. Considering the results of the tensile tests, the Stress Relief Socket has proved to have a significant advantage for replacement of existing methods of termination e.g. the splice. It should also be noted that the reproduction of the socket termination is more consistent than that of other methods of termination. The experimental outcomes can instruct future optimal mooring system design and marine renewable energy performances.Peer reviewe

Kalman tracking of linear predictor and harmonic noise models for noisy speech enhancement

This paper presents a speech enhancement method based on the tracking and denoising of the formants of a linear prediction (LP) model of the spectral envelope of speech and the parameters of a harmonic noise model (HNM) of its excitation. The main advantages of tracking and denoising the prominent energy contours of speech are the efficient use of the spectral and temporal structures of successive speech frames and a mitigation of processing artefact known as the ‘musical noise’ or ‘musical tones’.The formant-tracking linear prediction (FTLP) model estimation consists of three stages: (a) speech pre-cleaning based on a spectral amplitude estimation, (b) formant-tracking across successive speech frames using the Viterbi method, and (c) Kalman filtering of the formant trajectories across successive speech frames.The HNM parameters for the excitation signal comprise; voiced/unvoiced decision, the fundamental frequency, the harmonics’ amplitudes and the variance of the noise component of excitation. A frequency-domain pitch extraction method is proposed that searches for the peak signal to noise ratios (SNRs) at the harmonics. For each speech frame several pitch candidates are calculated. An estimate of the pitch trajectory across successive frames is obtained using a Viterbi decoder. The trajectories of the noisy excitation harmonics across successive speech frames are modeled and denoised using Kalman filters.The proposed method is used to deconstruct noisy speech, de-noise its model parameters and then reconstitute speech from its cleaned parts. Experimental evaluations show the performance gains of the formant tracking, pitch extraction and noise reduction stages

Overexpression of molecular chaperons GRP78 and GRP94 in CD44hi/CD24lo breast cancer stem cells

Introduction: Breast cancer stem cell with CD44hi/CD24lo phonotype is described having stem cell properties and represented as the main driving factor in breast cancer initiation, growth, metastasis and low response to anti-cancer agents. Glucoseregulated proteins (GRPs) are heat shock protein family chaperons that are charged with regulation of protein machinery and modulation of endoplasmic reticulum homeostasis whose important roles in stem cell development and invasion of various cancers have been demonstrated. Here, we investigated the expression levels of GRP78 and GRP94 in CD44hi/CD24lo phenotype breast cancer stem cells (BCSCs). Methods: MCF7, T-47D and MDA-MB-231 breast cancer cell lines were used. CD44hi/CD24lo phenotype cell population were analyzed and sorted by fluorescence-activated cell sorting (FACS). Transcriptional and translational expression of GRP78 and GRP94 were investigated by western blotting and quantitative real time PCR. Results: Results showed different proportion of CD44hi/CD24lo phenotype cell population in their original bulk cells. The ranking of the cell lines in terms of CD44hi/CD24lo phenotype cell population was as MCF7<T-47D<MDA-MB-231. Our results also indicated that CD44hi/CD24lo phenotype cells exhibited higher mRNA and protein expression level of GRP78 and GRP94 compared to their original bulk cells. Conclusion: Our results show a relationship between overexpression of GRP78 and GRP94 and exhibiting CD44hi/CD24lo phenotype in breast cancer cells. We conclude that upregulation of GRPs may be an important factor in the emergence of CD44hi/CD24lo phenotype BCSCs features. � 2016 The Author(s)