A study on material modeling to predict spring-back in V-bending of AZ31 magnesium alloy sheet at various temperatures

AZ31 magnesium alloy sheets are usually performed at high temperatures of 200–250°C due to their unusual hexagonal close-packed structure and low ductility at room temperature. In this study, to predict V-bending/unbending spring-back of AZ31 magnesium alloy sheets subjected to high temperatures, a modified kinematic/isotropic hardening model considering the unusual plastic behavior of the magnesium alloy sheets, which follow the modified Johnson–Cook (JC) model, was used by way of a user-material subroutine, using an explicit finite element code. The simulation results from the modified hardening model at room temperature are compared with measurements of tension/compression and compression/tension tests. The modified JC model was then applied to predict tension/compression and compression/tension curves at high temperatures. Finally, an actual V-bending/unbending process for an AZ31 magnesium alloy sheet at high temperatures was performed to verify the spring-back angle, and this angle was then compared with spring-back angle predictions of the FE simulation. The proposed hardening model showed good agreement between simulation results and corresponding experiments.     

Novel Characterization of Constipation Phenotypes in ICR Mice Orally Administrated with Polystyrene Microplastics

Indirect evidence has determined the possibility that microplastics (MP) induce constipation, although direct scientific proof for constipation induction in animals remains unclear. To investigate whether oral administration of polystyrene (PS)-MP causes constipation, an alteration in the constipation parameters and mechanisms was analyzed in ICR mice, treated with 0.5 μm PS-MP for 2 weeks. Significant alterations in water consumption, stool weight, stool water contents, and stool morphology were detected in MP treated ICR mice, as compared to Vehicle treated group. Also, the gastrointestinal (GI) motility and intestinal length were decreased, while the histopathological structure and cytological structure of the mid colon were remarkably altered in treated mice. Mice exposed to MP also showed a significant decrease in the GI hormone concentration, muscarinic acetylcholine receptors (mAChRs) expression, and their downstream signaling pathway. Subsequent to MP treatment, concentrations of chloride ion and expressions of its channel (CFTR and CIC-2) were decreased, whereas expressions of aquaporin (AQP)3 and 8 for water transportation were downregulated by activation of the mitogen-activated protein kinase (MAPK)/nuclear factor (NF)-κB signaling pathway. These results are the first to suggest that oral administration of PS-MP induces chronic constipation through the dysregulation of GI motility, mucin secretion, and chloride ion and water transportation in the mid colon.     

Microscopic study for the behavior of grain boundary using molecular dynamics

In this study, MD simulations have been performed to observe the behavior of a grain boundary in an a-Fe plate under 2-dimensional loading. In MD simulation, the acceleration of every molecule can be achieved from the potential energy and the force interacting between each molecule, and the integration of the motion equation by using the Verlet method gives the displacement of each molecule. Initially, four α-Fe rectangular plates which have different misorientation angles of grain boundary were modeled by using the Johnson potential and Morse potential. We compared the potential energy of the grain boundary system with that of the perfect structure model, which does not have a grain boundary inside. Also, we could obtain the width of the grain boundary by investigating the local potential energy distribution. The tensile loading for each grain boundary model at room temperature was applied and the behavior of the grain boundary was studied. From this study it was clarified that when the Johnson potential is used, the obvious fracture mechanism occurs along the grain boundary. With the Morse potential, the diffusion of the grain boundary appears instead of the grain boundary fracture.     

Does growth rate in oral reading fluency matter in predicting reading comprehension achievement?

In this study, we examined the relationship of growth trajectories of oral reading fluency, vocabulary, phonological awareness, letter-naming fluency, and nonsense word reading fluency from 1st grade to 3rd grade with reading comprehension in 1st, 2nd, and 3rd grades. Data from 12,536 children who were followed from kindergarten to 3rd grade longitudinally were used. These children were administered Dynamic Indicators of Basic Early Literacy Skills subtests, Peabody Picture Vocabulary Test—Third Edition, and reading comprehension (Stanford Achievement Test, 10th ed.) tasks multiple times in each year. Students' initial status and rate of growth in each predictor within each grade were estimated using individual growth modeling. These estimates were then used as predictors in dominance regression analyses to examine relative contributions that the predictors made to the outcome: reading comprehension. Among the 1st-grade predictors, individual differences in growth rate in oral reading fluency in 1st grade, followed by vocabulary skills and the autoregressive effect of reading comprehension, made the most contribution to reading comprehension in 3rd grade. Among the 2nd- and 3rd-grade predictors, children's initial status in oral reading fluency had the strongest relationships with their reading comprehension skills in 3rd grade. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Molecular differences of low methoxy pectins induced by pectin methyl esterase I: Effects on texture,release and perception of aroma in gel systems

Six types of low methoxy pectins (two commercial and four modified pectins treated with pectin methyl esterase from Valencia orange) with different degrees of esterification (DE), molecular weights (MW), and degrees of amidation were prepared. Pectin gels containing five aroma compounds were produced and their texture properties, release of aromas, and sensory flavour intensities were investigated. Regarding the gels made with lower MW pectins (<2.1 × 10⁵), only headspace concentration of isoamyl acetate was increased, according to the de-esterification of the pectins. In the pectin gels of higher MW (>3.7 × 10⁵), however, significantly higher concentrations of aromas in the headspace were shown in the gel with DE value of 6 than the gel with DE value of 40. Perceived flavour intensity was highest in the pectin gel with higher DE (∼40) and lower MW. The sensory texture analysis indicated that the pectin methyl esterase-modified pectin gels had increased hardness, coarseness of mass, springiness, and chewiness. The perceived flavour intensities of the gels showed strong negative correlations with firmness.     

Comparison of umami-taste active components in the pileus and stipe of pine-mushrooms (Tricholoma matsutake Sing.) of different grades

Umami-taste active components in pine-mushrooms (Tricholoma matsutake Sing.) were compared according to different grades (first, second, third, and fourth) and parts (pileus and stipe). The contents of umami-taste active free amino acids, such as aspartic acid and glutamic acid, decreased in the order of second grade > third grade > fourth grade > first grade. Also, the contents of umami-taste active 5′-nucleotides were highest and lowest in pine-mushrooms of second and first grades, respectively. All the contents of umami-taste active amino acids and 5′-nucleotides were higher in the pileus than in the stipe, irrespective of pine-mushroom grades. Equivalent umami concentration values of pine-mushrooms ranged from 13.26 (in the stipe of first grade) to 204.26 g (in the pileus of second grade) per 100 g. All the quantitative data obtained in this study are highly consistent with our previously data on umami sensory intensities of pine-mushrooms.     

Process design of multi-stage cold forging with small size for ESC solenoid valve parts

Journal of Mechanical Science and Technology - ESC’s solenoid valves independently brake each wheel, allowing the vehicle to maintain braking and directional stability. The most important...     

Study on volatile compounds formed from the thermal interaction of hydrolyzed vegetable proteins with reducing sugars

Food Science and Biotechnology - Hydrolyzed vegetable proteins (HVPs) are widely used food flavorings. This study investigated the volatiles formed in thermally reacted model systems containing...