Callaghan Innovation

I give for the first time explicit formulas for the coefficients needed for the fourth-order Edgeworth expansions of a multivariate standard estimate. I call these the Edgeworth coefficients. They are Bell polynomials in the cumulant coefficients. Standard estimates include most estimates of interest, including smooth functions of sample means and other empirical estimates. I also give applications to ellipsoidal and hyperrectangular sets.

Vanadium is a “critical metal” that is predominantly produced from steelmaking slags using a salt-roast leach process that emits corrosive byproduct gases and a contaminated liquid discharge. Here, we describe a clean vanadium extraction method using the environmentally benign lixiviant–carbonated water. This method was found to be highly selective for dissolution of vanadium, manganese, and calcium over iron. By simply using saturated aqueous CO2 solutions produced in a domestic SodaStream, we have extracted vanadium from air-roasted slags with up to 50% efficiency. A modified Parr reactor was then used to achieve higher CO2 saturation pressures, resulting in vanadium extraction efficiencies up to 77%. Vanadium-bearing solids were precipitated from the leachate solutions and further processed to produce both vanadium metal and a V–Mn alloy. Our results demonstrate that carbonated water leaching represents a promising alternative green chemistry route to vanadium extraction from steel slags.

A good approximation for the distribution of an estimate, is vital for statistical inference. Here we give Edgeworth expansions for the conditional density and the conditional distribution of any multivariate standard estimate.

This paper investigates how numerical modelling can be used to explore thermoacoustic machines and compares the accuracy of the performance predictions for different simulation software. The software used includes one designed for modelling Stirling machines called ‘Sage’ and for modelling thermoacoustic machines called ‘DeltaEC.’ To compare their results, a model of both a thermoacoustic Stirling engine and refrigerator were developed from existing models in published papers, which contained experimental data to validate the numerical models. Overall, it was found that although both can accurately model thermoacoustic machines, they present different optimal conditions, and Sage’s solving method makes it more complex to model the standing wave.

Electrification has been proposed as a route to decarbonizing air travel. Conventional electric motors are too heavy to achieve the power densities required for aviation so superconducting motors for aircraft are being developed. Superconductors however, work at cryogenic temperatures, which indispensably require a reliable and efficient cooling mechanism with a cryocooler. The Robinson Research Institute is developing a 3 MW superconducting motor using an HTS (High Temperature Superconductor) rotor operating at 50 K and MgB2 running at near 20 K for the stator. The motor is intended to run at a shaft speed of 4500-6000 rpm to directly drive a ducted fan. A key challenge is the removal of heat from a cryogenic spinning rotor to a stationary refrigerator so it can be rejected at ambient temperatures. Previous motors have utilized externally pumped or thermos-syphoned cryogens to cool the rotor, which require complex rotary seals. The aircraft application demands a compact and low weight solution. This paper presents a novel cooling design where a stationary cryocooler’s cold heat exchanger penetrates the rotor, and the relative motion of the two creates a pumping motion for cold helium gas to transfer heat from the rotor to the cryocooler. The sealing is low pressure and at ambient temperature and pressure with a temperature gradient in the helium adjacent to the cryocooler regenerator. Design and CFD modelling of the concept are presented showing the system can generate sufficient cold helium flow to transfer heat from the rotor to the cryocooler with a small temperature difference, resulting in a compact, efficient, and low-weight rotor cooling method.

This article presents a control strategy to carry out multiobject manipulation on a novel <underline xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</u> oft r <underline xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</u> botic <underline xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ta</u> ble (SoTa), which is a new form of the planar distributed manipulator. Manipulating multiple delicate objects simultaneously is an attractive feature of SoTa. The challenge here is to coordinate multiple objects in a confined planar space while avoiding interference with each other. The SoTa system adopts a manipulation strategy that includes a planning and a tracking stage for the purpose of sorting objects. The planning stage consists of two phases: 1) discrete path planning to find a path for each object on a grid map with respect to time; 2) trajectory generation to optimize and produce workable trajectories for SoTa. In the discrete path planning phase, a hierarchical searching method based on the time-varying potential field is proposed. Constraints of the SoTa system are modeled and incorporated into the path searching process. In the trajectory generation phase, a piecewise B-spline method is adopted to generate trajectories based on previously found discrete paths. Next, in the tracking stage, the objects are led to their goals along the trajectories ensuring safety and SoTa's capability. The performances of the proposed algorithm were simulated, analyzed, and compared with the conflict-based search method, which is optimal for multiagent path finding. A multiobject manipulation experiment of three objects on a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$4\times 4$</tex-math></inline-formula> grid was conducted on the SoTa. The results demonstrated the effectiveness of the proposed control strategy in executing multiobject manipulations for sorting tasks on the SoTa.

This work studied hydrogen adsorption by a two-dimensional silicon carbide using a combined molecular dynamics and density functional theory approach. The geometrical properties of partially and fully hydrogenated structures were investigated, considering the effect of zero-point energy. The preferred hydrogen atom location is on top of silicon atoms. The hydrogen interaction energies were obtained for the first time as the attractive force. For fully hydrogenated 2D SiC, the chair-like conformer is the most stable configuration, and the next is the boat-like conformer, while the table-like structure is not stable. The coverage and arrangement of the adsorbed hydrogen atoms significantly influence the values of the direct/indirect bandgaps of the considered systems, increasing the bandgap to 4.07, 3.64, and 4.41 eV for chair-like, table-like, and boat-like, respectively. Their dynamical stability was investigated by phonon dispersion calculations. The obtained results can serve as a guide for the application of hydrogenated two-dimensional silicon carbide in optoelectronic applications in manufacturing innovation.

Despite the extensive research within the cryonics field dating back to the early twentieth century, very little is known regarding its paired legal and ethical complications. Resulting of society's expansive fundamental ways, the community within modern times has expanded tenfold and scientific research such as cryonics has too. This study analyzes the vast legal implications that came from the increasingly popular yet prolonged use of cryonics within everyday life. Through imperative law, this study analyzes the ethical standards of the rising practice of cryonics by referencing past court cases ranging from American and global policies, laws, and amendments. An analysis of such documents yields a common justifiable explanation for cryonics' justified legal position and its inadvertent ethical protections. This study is part of a growing body of research reflecting American and foreign perspectives on the rising practice of cryonics within modern society. In analyzing a large source of legal policy within American and foreign affairs, this study will contribute to further analysis and research on cryonics.