Internal Forces in a Reinforced Concrete Box Culvert

In 1996, a reinforced concrete box culvert with approximately 19 meters of embankment fill was instrumented with strain gages and pressure cells to determine the internal forces applied to the culvert. Strain and pressure readings were taken for a period of 3 years during and after the construction of the embankment. From a knowledge of the culvert\u27s dimensions and material properties, the strain readings were converted to forces and bending moments. These forces were then compared to the allowable criteria from the American Association of State Highway and Transportation Officials (AASHTO) Standard Specifications for Highway Bridges. A computer model of the culvert was performed to compare the results of the strain gages and pressure cells to the unit weight of the embankment fill. The computer model was also used to study the changes in internal forces due to different boundary conditions. The results showed that axial forces and bending moments are linearly related to the embankment fill height. The box culvert has adequate capacity according to the design equations from AASHTO. Computer modeling of the culvert showed that the effects of different boundary conditions give slightly different moments in the roof and the wall. Load distributions on the roof show very little change in bending moments and shears, but when the load distribution on the wall increases on the bottom, a significant increase in shear forces is seen

Energy transfer and localization in molecular crystals

With the aim of developing new technologies for the detection and defeat of energetic materials, this collection of work was focused on using simulations to characterize materials at extremes of temperature, pressure and radiation. Each branch of the work here is collected by which material response is potentially used as the detectable signal. Where the chemical response is of interest, this work will explore the possibility of non-statistical chemical reactions in condensed-phase energetic materials via reactive molecular dynamics (MD) simulations. We characterize the response of three unique high energy density molecular crystals to different means of energy input: electric fields of various frequencies (100 − 4000cm−1) and strengths, and direct heating at various rates. It was found that non-equilibrium states can be created for short timescales when the energy input targets specific vibrations through the electric fields, and that equilibration eventually occurs even when the insults remain present. Interestingly, for strong fields these relaxation timescales are comparable to those of the initial chemical decomposition of the molecules. On similar timescales, we have studied the relaxation process of shock compressed molecules. Details of how energy localization, either from these vibrational or mechanical insults, affects the preferred uni- or multi-molecular reactions are discussed. These results provide insight into non-equilibrium or coherent initiation of chemistry in the condensed phase that would be of interest in fields ranging from catalysis to explosives. Without initiating reactions, the thermal response of a material subject to a mechanical stimulus can be used to inform on the chemical characteristics. Here MD simulations are performed to study how energy from an acoustic wave is localized in a composite material of a polymer and molecular crystal. Insight is provided on how the interface between these to materials will affect which component absorbs and localizes this insult energy. Furthermore these results provide an explanation to anomalous experimental results that subject similar composites to acoustic insults. In parallel efforts for the detection and defeat of explosives, we study the scattering of electromagnetic waves in anisotropic energetic materials. Nonlinear light-matter interactions in molecular crystals result in frequency-conversion and polarization changes. Applied electromagnetic fields of moderate intensity can induce these nonlinear effects without triggering chemical decomposition, offering a mechanism for non-ionizing identification of explosives. We use molecular dynamics simulations to compute such two-dimensional THz spectra for planar slabs made of PETN and ammonium nitrate. We discuss third-harmonic generation and polarization-conversion processes in such materials. These observed far-field spectral features of the reflected or transmitted light may serve as an alternative tool for stand-off explosive detection

Responsible Sourcing: A Perspective from Small Apparel Business Owners

The study aims to explore the responsible sourcing issues from small apparel business owners\u27 perspectives, including motives of responsible sourcing, supplier selection criteria, managerial approaches, and barriers to responsible sourcing

LC-MS/MS reveals hordeins are enriched in brewers’ spent grain

Barley is commonly used in malting and brewing, and spent grain is repurposed for other foods. Barley contains gluten proteins called hordeins that cause intestinal damage and disease symptoms if eaten by people with celiac disease and related conditions. While the mashing process in brewing can partially hydrolyze immunogenic epitopes in hordeins, the immunogenic epitope load between the starting malt and spent grain has not been investigated. Herein, we quantified hordeins in commercially available spent grain and from matching malt. Liquid chromatography-mass spectrometry (LC-MS) and sandwich and competitive R5 ELISAs were used for quantification, revealing a higher abundance of gluten proteins in the spent grain product compared with the input malt. Certain hordein subtypes were enriched while others were depleted, and overall protein content was higher in spent grain. This suggests that the mashing process selectively extracts nonprotein components, leaving protein and hordein content elevated in spent grain. The spent grain products tested were not safe for consumers with celiac disease

BERA-TACTYC Early Childhood Research Review 2003-2017

BERA/TACTYC Review of Early Childhood Education and Care in the UK, 2003-2017 has involved a wide range of early childhood specialists, both in the early consultation stages, and in writing the five main sections of the Review. Teams of authors and their reference groups came together from TACTYC – the Association for Professional Development in Early Years, and the BERA Early Childhood Education and Care SIG. Using specific questions to interrogate the literature, each team worked on one of five main themes: Professionalism; Parenting and Family; Play and Pedagogy; Learning, Development and Curriculum, and Assessment and School Readiness. These themes are contextualised within broad policy issues in the UK. The Introduction shows the working methods for the Review, and the Conclusion brings together key messages and suggestions for future research. We hope that the Review will prove useful to a range of early childhood specialists, including students, researchers, practitioners, policy makers and teachers in further and higher education. We intend to create a User Review that will be aimed at practitioners and to engage other stakeholders in current trends and debates. The Review is being launched at a time of change and uncertainty within early childhood education and care, and we hope that the Review will provide a focal point for discussions about future directions in the four UK policy frameworks, the importance of research, and how we use research evidence to inform provision and practice

Nanomechanics Simulation Toolkit - Dislocations Make or Break Materials

The goal of computational material science is to improve existing materials and design new ones through mathematical calculations. In particular, molecular dynamic simulations can allow for visualization of dislocations in a material, along with its resulting behavior when under stress. For example, plastic deformation and strain hardening result from the movement, multiplication and interaction of dislocations within the crystal structure. A simulation tool to study these phenomena was developed for the nanoHUB web resource as a part of the Network for Computational Nanotechnology at Purdue University and targets audiences ranging from undergraduate students to researchers. We created a user-friendly environment to explain the complicated nature of dislocations on a basic level for undergraduate students, while enabling researchers to modify advanced inputs. The output of the tool provides both quantitative graphs and visual animations, essential for anyone trying to understand how dislocations either move or nucleate. In its default state, the tool will access loader files that generate simulations with pre-determined inputs in order to accelerate usage. More advanced users can manipulate parameters, such as simulation run time and dislocation type, to fit their individual needs. The tool can provide a useful framework both as an instructional device in material science courses as well as a simulation framework for researchers. Furthermore, web resources like this provide understandable feedback for modeling and verifying ongoing research projects

Exploiting Structure in the Bottleneck Assignment Problem

An assignment problem arises when there exists a set of tasks that must be allocated to a set of agents. The bottleneck assignment problem (BAP) has the objective of minimising the most costly allocation of a task to an agent. Under certain conditions the structure of the BAP can be exploited such that subgroups of tasks are assigned separately with lower complexity and then merged to form a combined assignment. In particular, we discuss merging the assignments from two separate BAPs and use the solution of the subproblems to bound the solution of the combined problem. We also provide conditions for cases where the solution of the subproblems produces an exact solution to the BAP over the combined problem. We then introduce a particular algorithm for solving the BAP that takes advantage of this insight. The methods are demonstrated in a numerical case study.Comment: Accepted in IFAC World Congress 202