Meso-scale modelling of deformation, damage and failure in dual phase steels

Advanced high strength steels (AHSS), such as dual phase (DP) and transformation induced plasticity (TRIP) steels, o er high ductility, formability, and strength, as well as high strength-to-weight ratio and improved crash resistance. Dual phase steels belong to a family of high strength grades which consist of martensite, responsible for strengthening, distributed in a ductile ferrite matrix which accommodates the deformation throughout the forming process. It has been shown that the predominant damage mechanism and failure in DP steels depends on the ferrite and martensite grain sizes and their morphology, and can range from a mixture of brittle and ductile rupture to completely ductile rupture in a quasi-static uniaxial tension test. In this study, a hybrid nite element cellular automata model, initially proposed by Anton Shterenlikht (2003), was developed to evaluate the forming behaviour and predict the onset of instability and damage evolution in a dual phase steel. In this model, the nite element constitutive model is used to represent macro-level strain gradients and a damage variable, and two di erent cell arrays are designed to represent the ductile and brittle fracture modes in meso-scale. In the FE part of the model, a modi ed Rousselier ductile damage model is developed to account for nucleation, growth and coalescence of voids. Also, several rate-dependent hardening models were developed and evaluated to describe the work hardening ow curve of DP600. Based on statistical analysis and simulation results, a modi ed Johnson-Cook (JC) model and a multiplicative combination of the Voce-modi ed JC functions were found to be the most accurate hardening models. The developed models were then implemented in a user-de ned material subroutine (VUMAT) for ABAQUS/Explicit nite element simulation software to simulate uniaxial tension tests at strain rates ranging from 0.001s-1to 1000s-1, Marciniak tests, and electrohydraulic free-forming (EHFF). The modi ed Rousselier model could successfully predict the dynamic behaviour, the onset of instability and damage progress in DP600 tensile test specimens. Also, the forming limit curve (FLC) as well as the nal damage geometry in DP600 Marciniak specimens was successfully predicted and compared with experiments. A hybrid FE+CA model was utilized to predict the major fracture mode of DP600 and DP780 sheet specimens under di erent deformation conditions. This hybrid model is able to predict quasi-cleavage fracture in ultra- ne and coarse-grained DP600 and DP780 at low and high strain rates. The numerical results showed the capabilities of the proposed model to predict that higher martensite volume fraction, greater ferrite grain sizes and higher strain rates promote the brittle fracture mechanism whereas ner grain sizes and higher temperature alter the dominant fracture mechanism to ductile mode

Guest editorial: Special section on quality control by artificial vision

published_or_final_versio

The effects of soccer-specific intermittent exercise on salivary IgA responses

Exercise has been demonstrated to influence susceptibility to upper respiratory tract infections (URTI) because various aspects of immune function including mucosal immunity are temporarily changed after exercise. Lower concentrations of salivary 19A (s-IgA) as a predominant immunoglobulin and component of saliva or a chronic deficiency in s-IgA have been associated with an increased frequency of URTI episodes. Previous studies of aerobic exercise have incorporated the performance of running or cycling. Responses of s-19A to intermittent exercise patterns as they occur in soccer remain to be resolved. A laboratory based soccerspecific intermittent exercise protocol was used within this thesis to mimic the physiological stress associated with soccer, characterised by highintensity activity as noted during soccer play. The aims of this thesis were to determine the s-IgA responses to a bout or repeated bouts of soccerspecific intermittent exercise and investigate the effects of carbohydrate ingestion on s-IgA when such exercise is performed in increased ambient temperature. Laboratory based soccer-specific intermittent exercise and continuous exercise at the same moderate exercise intensity evoked insufficient stimulation of the hypothalamic-pituitary-adrenal axis to modify s-IgA responses. Changes in s-19A and cortisol did not differ between exercise types during or immediately following exercise, or 6 h, 24 h and 48 h afterwards. Physiological responses to intermittent exercise also conforming to the activity pattern of soccer match-play were similar to those for continuous exercise at the same average work-rate, despite the higher perceived exertion during intermittent exercise. Two bouts of soccer-specific intermittent exercise 48 h apart that were designed to provide a repeatable physiological stress comparable to strenuous soccer training induced s-19A responses that were similar following both bouts of exercise. Performing the second bout of exercise did not significantly suppress s-IgA concentration after 48 h recovery although a small progressive reduction in s-19A was observed. Performance of a second soccer-specific exercise bout in one day with a 2.25 h rest in between bouts elicited an increase in heart rate and perceived exertion, compared with a single session at the same time of day, but did not appear to suppress s-IgA outcomes. There was also no difference between responses of s-IgA concentration and secretion rate or salivary cortisol at the different times of day. Soccer can be played under hot environmental conditions and it is thought that addition of carbohydrate to fluids may prevent adverse changes in mucosal immune responses. Carbohydrate supplementation before and at regular intervals whilst performing soccer-specific intermittent exercise at 30°C, did not influence s-IgA responses or salivary cortisol when compared to placebo. In view of the failure of these experimental interventions to discern effects on s-IgA responses, a meta-analysis of the literature was conducted. The meta-analysis revealed an overall elevation in s-IgA concentration post acute exercise and following chronic exercise. In contrast, in term of s-IgA secretion rate, an overall significant decline after both acute and chronic exercise was a consistent finding. In conclusion, one exercise bout or repeated soccer-specific intermittent exercise in the present experiments did not induce compromises in s-IgA responses. There was no adverse effect upon s-IgA responses to intermittent exercise performance under conditions of heat stress with or without carbohydrate treatment. Although, 32 percent of studies included in the meta-analysis have indicated similar results, the disparity with overall findings may arise from differences in the exercise protocols used and/or bias for s-IgA changes in published studies

A combined continuous and interval aerobic training improves metabolic syndrome risk factors in men.

Individuals with metabolic syndrome have significantly higher risk for cardiovascular disease, Type 2 diabetes leading to premature death mortality. Metabolic syndrome has a complex aetiology, thus it may require a combined and multi-targeted aerobic exercise regimen to improve risk factors associated with the metabolic syndrome. Therefore, the aim of this study was to evaluate the effect of combined continuous and interval aerobic training on patients with metabolic syndrome. Thirty adult male with metabolic syndrome (54±8 years) were randomly divided into two groups: Test Training Group (TTG; n=15) or Control Group (CG; n=15). Subjects in TTG group performed combined continuous and interval aerobic training using a motorised treadmill three times per week for 16 weeks. Subjects in CG group were advised to continue with their normal activities of life. Twenty-two men completed the study (11 men in each group). At the end of the study, in TTG group, there were significant (for all, P<0.05) reductions in total body weight (-3.2%), and waist circumference (-3.43 cm), blood pressure (BP; up to -12.7 mmHg), plasma insulin, glucose and triacylglycerides levels. Moreover, there were significant (for all, P<0.05) increases in VO2max (-15.3%) and isometric strength of thigh muscle (28.1%) and HDL in TTG group. None of the above indices were changed in CG group at the end of 16 week study period. Our study suggests that adoption of a 16 week combined continuous and interval aerobic training regimen in men with metabolic syndrome could significantly reduce cardiovascular risk factors in these patients

On-line optical measurement and monitoring of yarn density in woven fabrics

This paper describes a vision-based system that monitors the yarn density of woven fabrics on-line. The system is described in terms of its two principal modules, namely, the image acquisition and the image analysis subsystems. The image acquisition subsystem is implemented with standard components on a low-cost personal computer platform. These components consist of a line-scan camera, a DSP-based image acquisition and processing card, and a host personal computer. The image acquisition process is controlled by a software module that runs on the DSP board and accumulates a 2-D image suitable for the density measurement algorithm. The image analysis sub-system, which also runs on the DSP board, implements a novel, yet straightforward, algorithm that utilizes the discrete Fourier transform for monitoring the yarn density of the fabrics from the acquired images. In this algorithm, the Fourier spectrum of the images is covered by contiguous, concentric annular regions that have a prespecified width. The spectrum values within each annular region are summed, normalized, and subsequently used to produce a 1-D signature. Simple statistics of the obtained signatures are the basis for characterizing the fabric in terms of its yarn density. The described system is tested on seven fabrics with common properties but varying yarn densities and has shown to be accurate within 2 yarns per inch in either direction. It is also shown that the obtained accuracy, which is primarily a function of the image resolution, can be greatly improved

Acute exercise and appetite-regulating hormones in overweight and obese individuals: A meta-analysis

In lean individuals, acute aerobic exercise is reported to transiently suppress sensations of appetite, suppress blood-concentrations of acylated ghrelin (AG) and increase glucagon-like peptide-1 (GLP-1) and peptide-YY (PYY). Findings in overweight/obese individuals have yet to be synthesised. In this systematic review and meta-analysis, we quantified the effects acute exercise has on AG, total PYY and GLP-1 in overweight/obese individuals. The potential for body mass index (BMI) to act as a moderator for AG was also explored. Six published studies (73 participants, 78% male, mean BMI: 30.6 kg.m-2) met the inclusion criteria. Standardised mean differences (SMD) and standard errors were extracted for AG, total PYY and GLP-1 concentrations in control and exercise trials and synthesised using a random effects meta-analysis model. BMI was the predictor in a meta-regression for AG. Exercise moderately suppressed AG area-under-the-curve concentrations (pooled SMD -0.34, 95%CI: -0.53 to -0.15). The magnitude of this reduction was greater for higher mean BMIs (pooled meta-regression slope: -0.04 SMD/kg.m-2 (95%CI: -0.07 to 0.00)). Trivial SMDs were obtained for total PYY (0.10, 95%CI: -0.13 to 0.31) and GLP-1 (-0.03, 95%CI: -0.18 to 0.13). This indicates that exercise in overweight/obese individuals moderately alters AG in a direction that could be associated with decreased hunger and energy intake. (PROSPERO registration: CRD42014006265)

A marked interannual variability of haze linked to particulate sources and meteorological conditions in Tehran (Iran), 1990-2020

This research assessed for the first time the spatio-temporal changes of haze pollution (NHAZEs) and its relationship with levels of gaseous pollutants and meteorological conditions over Tehran metropolis (Iran) for 1990-2020. The results showed a significant decreasing trend of NHAZEs annually and in winter, along with a significant increasing trend in the horizontal visibility. However, a marked interannual variability linked to changes in PM2.5 concentrations and the influence of meteorological conditions was detected, which explained 65% and 30% of the NHAZEs variances, respectively. We found that the increasing trend of wind speed annually and in winter is the principal driver behind the decrease in NHAZEs and the increase in visibility; as winds control the movement and dispersion of air pollution. In relation to gaseous pollutants, a case study showed that the highest concentrations of PM2.5 and NHAZEs were recorded under high levels of SO2, CO, and NO2, and low levels of O3, which mainly occurred under stable anticyclonic circulations. Spatially, the NHAZEs mostly affected the western, southwestern, central, and some parts of the northern of Tehran metropolis, because of the location of industries, traffic, and lack of green areas

A novel approach to computer-aided diagnosis of mammographic images

This is a work-in-progress report of a research endeavor that deals with the design and development of a novel approach to computer-aided diagnosis (CAD) of mammographic images. With the initial emphasis being on the analysis of microcalcifications, the proposed approach defines a synergistic paradigm that utilizes new methodologies together with previously developed techniques. The new paradigm is intended to promote a higher degree of accuracy in CAD of mammograms with an increased overall throughput. The process of accomplishing these goals is initiated by the fractal encoding of the input image, which gives rise to the generation of focus-of-attention regions (FARs), that is, regions that contain anomalies. The primary thrust of this work is to demonstrate that by considering FARs, rather than the entire input image, the performances of the ensuing processes (i.e., segmentation, feature extraction, and classification) are enhanced in terms of accuracy and speed. After presenting the proposed approach to CAD of mammographic images, the paper describes the generation of FARs. Furthermore, an experimental study is included that demonstrates the impact of this front-end procedure on the process of microcalcification segmentation. Specifically, the experimentation reveals a dramatic decrease (increase) in the amount of input data (throughput), as well as a reduction in the number of false detections

Acute Exercise and Appetite-Regulating Hormones in Overweight and Obese Individuals: A Meta-Analysis.

In lean individuals, acute aerobic exercise is reported to transiently suppress sensations of appetite, suppress blood concentrations of acylated ghrelin (AG), and increase glucagon-like peptide-1 (GLP-1) and peptide-YY (PYY). Findings in overweight/obese individuals have yet to be synthesised. In this systematic review and meta-analysis, we quantified the effects that acute exercise has on AG and total PYY and GLP-1 in overweight/obese individuals. The potential for body mass index (BMI) to act as a moderator for AG was also explored. Six published studies (73 participants, 78% male, mean BMI: 30.6 kg·m-2) met the inclusion criteria. Standardised mean differences (SMDs) and standard errors were extracted for AG and total PYY and GLP-1 concentrations in control and exercise trials and synthesised using a random effects meta-analysis model. BMI was the predictor in metaregression for AG. Exercise moderately suppressed AG area-under-the-curve concentrations (pooled SMD: -0.34, 95% CI: -0.53 to -0.15). The magnitude of this reduction was greater for higher mean BMIs (pooled metaregression slope: -0.04 SMD/kg·m-2 (95% CI: -0.07 to 0.00)). Trivial SMDs were obtained for total PYY (0.10, 95% CI: -0.13 to 0.31) and GLP-1 (-0.03, 95% CI: -0.18 to 0.13). This indicates that exercise in overweight/obese individuals moderately alters AG in a direction that could be associated with decreased hunger and energy intake. This trial is registered with PROSPERO: CRD42014006265