Detonation performance of the CL-20-based explosive LX-19

The generation of constitutive detonation performance model components for high explosives (HEs) invariably involves reference to experiment, as reliable first-principles determinations of these models are beyond our current capability. Whatever its form or complexity, the detonation performance model must be able to accurately capture the detonation wave timing and the energy release that it triggers upon arrival. Specifically, the HE products equation-of-state (EOS), which largely determines the detonating HE’s ability to do useful work on its surroundings, is typically inferred from cylinder expansion tests where metal-confined HE cylinders are detonated and the ensuing outer confiner wall-expansion trajectory is recorded. Expensive, iterative comparisons to multimaterial hydrodynamic (or “hydrocode”) simulations of these experiments are then used to constrain the parameters of the chosen EOS form. Here, we report on new detonation performance experiments produced for the highly-ideal, plastic-bonded explosive and CL-20-based LX-19 which are used to produce a new sub-scale detonation performance model for the explosive. This includes new products EOS and a new Detonation Shock Dynamics front propagation law. We also confirm the capability of two new, non-hydrocode-based products EOS generation techniques to accelerate the HE model parameterization process. This latter development is particularly significant for detonation performance modeling of new HE formulations.     

Paired and Unpaired Deep Learning Methods for Physically Accurate Super-Resolution Carbonate Rock Images

Transport in Porous Media - X-ray micro-computed tomography (micro-CT) has been widely leveraged to characterise the pore-scale geometry of subsurface porous rocks. Recent developments in...     

Stock optimization for service differentiated demands with fill rate and waiting time requirements

We develop a computationally efficient optimization procedure to optimize stock and rationing levels for a model consisting of a single product with two priority–demand classes, given by mutually independent, stationary, Poisson demand processes. Each priority class has its own service levels requirements, defined by the class-specific fill rate and expected waiting-time levels. Order lead times are independent and identically distributed random variables. This is the first study in this setting to consider both waiting-time constraints along with fill rate requirements.     

Optimal control of plant virus propagation

Plants are a food source for man and many species. But, plants are subject to diseases, many of which are caused by viruses. Usually, virus propagation is done by a vector. Insect vectors typically have a seasonal behavior, and processes have delays. To combat the vectors, chemical insecticides are commonly used as a control. Unfortunately, these chemicals not only are expensive but also have toxic effects on humans, animals, and the environment. An alternative is to introduce a predator species to prey on the insects and limit the spread of the virus. A combination of insecticide and predators can be used to control the vector population. The question is whether there is an optimal combination. We introduce a mathematical model of ordinary differential equations describing the interaction between plants, vectors, and predators. To determine the optimal amount of predators to introduce and insecticide to use, an objective function giving the total cost to the farmer of the disease is given. We find the controls that minimize the objective function subject to the population variables satisfying the differential equation model and initial conditions together with constraints. There are two main different approaches that can be used to solve the optimal control problem: indirect and direct methods. We use direct methods to solve the problem with and without seasonality and delays. From the practical side, the model can be used to help farmers determine the right balance of insecticide and predators to minimize the total cost.     

The spectroscopic and energy transfer characteristics of the rare earth ions used for silicate glass fibre lasers operating in the shortwave infrared

The continuing growth in the research and development of high power diode‐pumped fibre lasers relates to the exceptional thermal management provided by the extended geometry of the fibre and the small quantum defect associated with the 1 μm emitting Yb³⁺ ion. Lengthening the emission wavelength of diode‐pumped fibre lasers further into the infrared is important for many applications ranging from medicine to defence; however, extending the emission wavelength remains a challenge. This review will examine in detail the spectroscopy and the energy transfer processes that impact Tm³⁺‐doped and Ho³⁺‐doped silicate glasses that are used for fibre lasers in the 1.9 μm to 2.1 μm region of the shortwave infrared spectrum. We will explore a number of important applications that function in the shortwave infrared region that will benefit from using these light sources and I will suggest the reasons for choosing silicate glass over other glasses as the host material for this wavelength range.     

Nanoindentation modeling of a nanodot-patterned surface on a deformable substrate

A numerical model was developed to simulate the nanoindentation of a Ni nanodot-patterned surface (NDPS) on a deformable Si substrate. Each contacting nanodot on the Si substrate was treated individually in this model and the interaction among the nanodots was considered through the elastic deformation of the Si substrate. The load–deformation relationship for the single-asperity contact between the indenter tip and a nanodot was determined using finite element analysis. A nanoindentation experiment on a Ni NDPS was performed to test the developed model. The simulation and experimental results were found to be in good agreement. The experimentally verified model was used to explore the effects of substrate deformation and surface roughness caused by the Ni nanodots on the nanoindentation behavior. It was found that the effect of the substrate and the effect of roughness must be considered. A detailed study of the substrate deformation shows that the interaction among nanodots, through the substrate, can contribute a considerable portion of the total deformation under a nanodot. The yield strength of the nanodot was found to have a significant effect on the contact deformation, while the elastic modulus was found to have little effect.