From fractions to complete Segal spaces

We show that the Rezk classification diagram of a relative category admitting a homotopical version of the two-sided calculus of fractions is a Segal space up to Reedy-fibrant replacement. This generalizes the result of Rezk and Bergner on the classification diagram of a closed model category, as well as the result of Barwick and Kan on the classification diagram of a partial model category.Comment: 21 pages, LaTeX. Changes in v3: added some expository material, following suggestions by anonymous referee. (N.B. numbering has changed.

Decoloured Bloodmeal Based Bioplastic

Renewable and compostable bioplastics can be produced from biopolymers such as proteins. Animal blood is a by-product from meat processing and is rich in protein. It is dried into low value bloodmeal and is used as animal feed or fertiliser. Previous work has shown that bloodmeal can be converted into a thermoplastic using water, urea, sodium dodecyl sulphate (SDS), sodium sulphite and triethylene glycol (TEG). This material is currently being commercialised as Novatein Thermoplastic Protein (NTP) and studies are working on improving its properties through production of composites and blends. In addition further studies are working on understanding its molecular structure before and after thermoplastic processing by utilising various analytical techniques. A specific area identified for improvement is its colour and smell. NTP is black in colour and has an offensive odour which means its current potential applications are limited to agriculture and waste disposal. Approximately 30 to 40% of plastics are used in short life span applications such as packaging and using bioplastics in these applications would be advantageous because of their compostability. To increase NTP’s possible range of applications to common applications such as packaging and increase its acceptance from consumers, its colour and odour must be removed without compromising its mechanical properties. Oxidative treatment methods for removing colour and odour from red blood cell concentrate (RBCC), modified red blood cell concentrate (mRBCC) and bloodmeal were investigated using hydrogen peroxide, peracetic acid (PAA), sodium hypochlorite, sodium chlorite, sodium chlorate and chlorine dioxide. Treatment effect on protein molecular weight, crystallinity, thermal stability, solubility, product colour and smell were investigated. Treating RBCC and mRBCC required multiple processing steps, had high water contents (67% and 93% respectively), foamed during treatment with peroxides and the protein was prone to hydrolysis. Bloodmeal contained 95% solids and was less sensitive to hydrolysis. The best decolouring and deodorising results were obtained by treating bloodmeal with 5% PAA. Using this novel treatment method, decolouring was completed within five minutes and produced a powder which was 67% white based on the RGB colour scale. Protein molecular weight was unaffected by PAA concentration, with a number average molecular weight ranging between 190-223 kDa for 1-5% PAA treated bloodmeal. However, its crystallinity decreased from 35% to 31-27% when treated with 1-5% PAA. Treating bloodmeal with 1-5% PAA also reduced the protein’s thermal stability, glass transition temperature (225°C down to 50°C) and increased its solubility from 11% to 85% in 1% SDS solution at 100°C. 3-5% PAA treated bloodmeal powder was extruded using different combinations of water, TEG, glycerol, SDS, sodium sulphite, urea, borax, salt and sodium silicate at concentrations up to 60 parts per hundred parts bloodmeal (pphBM). Partially consolidated extrudates and fully consolidated injection moulded samples were obtained using a combination of water, TEG and SDS. 4% PAA treated bloodmeal produced the best extruded and injection moulded samples and was chosen for investigating the effects of water, TEG and SDS concentration on consolidation and specific mechanical energy input (SME) as well as product colour and mechanical properties. Analysis of variance (ANOVA) showed SDS was the most important factor influencing ability to be extruded because it detangled protein chains and allowed them to form new stabilising interactions required for consolidation. The best extruded sample, which was 98% consolidated and 49% white, contained 40 pphBM water, 10 pphBM TEG and 6 pphBM SDS. TEG had the greatest effect on the product’s mechanical properties and colour after injection moulding because of its plasticisation effect. ANOVA showed TEG contributed 30.5% to changes in Young’s modulus, 66.9% to strain, 39.7% to toughness, 0.1% to UTS and 38.1% to colour. However, SDS also contributed 8.1% to changes in Young’s modulus, 13.7% to strain, 15.2% to toughness, 12.5% to UTS, 0.5% to colour. Initial water content contributed 19.7% to Young’s modulus, 1.0% to strain, 0.6% to toughness, 30.0% to UTS and 29.9% to colour. The best injection moulded sample was produced using 50 pphBM water, 20 pphBM TEG and 3 pphBM SDS. This produced a material which was 39% white, which had an almost transparent yellow/orange colour with a tensile strength of 4.62 MPa, Young’s modulus 85.48 MPa, toughness 1.75 MPa and 82.62% strain. The mechanical properties of the product manufactured in this study were comparable to those of NTP, but the product was mostly decoloured, allowing it to be easily pigmented and without an offensive odour

Processing peracetic acid treated bloodmeal into bioplastic

Renewable and biodegradable bioplastics can be produced from biopolymers such as proteins. Animal blood is a by-product from meat processing and is rich in protein. It is dried into low value bloodmeal and is used as animal feed or fertiliser. Previous work has shown that bloodmeal can be converted into a thermoplastic using water, urea, sodium dodecyl sulphate (SDS), sodium sulphite and triethylene glycol (TEG). To increase its range of applications and acceptance from consumers, the colour and odour was removed from bloodmeal using peracetic acid (PAA). The aim of this study was to investigate the bioplastic processing of 3-5% (w/w) PAA treated bloodmeal. 3-5% PAA treated bloodmeal powder was compression moulded using different combinations of water, TEG, glycerol, SDS, sodium sulphite, urea, borax, salt and sodium silicate at concentrations up to 60 parts per hundred bloodmeal (pphBM). Partially consolidated extrudates and fully consolidated compression moulded sheets were obtained using a combination of water, TEG and SDS. 4% PAA treated bloodmeal produced the best compression moulded sheets and extrudates and was chosen for investigating the effects of water, TEG and SDS concentration on consolidation, specific mechanical energy input (SME) and product colour during extrusion. Analysis of variance (ANOVA) showed SDS was the most important factor influencing its ability to be extruded because it detangled protein chains and allowed them to form new stabilising interactions required for consolidation. The best extruded sample, which was 98% consolidated and 49% white, contained 40 pphBM water, 10 pphBM TEG and 6 pphBM SDS

Compositional Set Invariance in Network Systems with Assume-Guarantee Contracts

This paper presents an assume-guarantee reasoning approach to the computation of robust invariant sets for network systems. Parameterized signal temporal logic (pSTL) is used to formally describe the behaviors of the subsystems, which we use as the template for the contract. We show that set invariance can be proved with a valid assume-guarantee contract by reasoning about individual subsystems. If a valid assume-guarantee contract with monotonic pSTL template is known, it can be further refined by value iteration. When such a contract is not known, an epigraph method is proposed to solve for a contract that is valid, ---an approach that has linear complexity for a sparse network. A microgrid example is used to demonstrate the proposed method. The simulation result shows that together with control barrier functions, the states of all the subsystems can be bounded inside the individual robust invariant sets.Comment: Submitted to 2019 American Control Conferenc

UniCal: a Single-Branch Transformer-Based Model for Camera-to-LiDAR Calibration and Validation

We introduce a novel architecture, UniCal, for Camera-to-LiDAR (C2L) extrinsic calibration which leverages self-attention mechanisms through a Transformer-based backbone network to infer the 6-degree of freedom (DoF) relative transformation between the sensors. Unlike previous methods, UniCal performs an early fusion of the input camera and LiDAR data by aggregating camera image channels and LiDAR mappings into a multi-channel unified representation before extracting their features jointly with a single-branch architecture. This single-branch architecture makes UniCal lightweight, which is desirable in applications with restrained resources such as autonomous driving. Through experiments, we show that UniCal achieves state-of-the-art results compared to existing methods. We also show that through transfer learning, weights learned on the calibration task can be applied to a calibration validation task without re-training the backbone

On shocks driven by high-mass planets in radiatively inefficient disks. I. Two-dimensional global disk simulations

Recent observations of gaps and non-axisymmetric features in the dust distributions of transition disks have been interpreted as evidence of embedded massive protoplanets. However, comparing the predictions of planet-disk interaction models to the observed features has shown far from perfect agreement. This may be due to the strong approximations used for the predictions. For example, spiral arm fitting typically uses results that are based on low-mass planets in an isothermal gas. In this work, we describe two-dimensional, global, hydrodynamical simulations of disks with embedded protoplanets, with and without the assumption of local isothermality, for a range of planet-to-star mass ratios 1-10 M_jup for a 1 M_sun star. We use the Pencil Code in polar coordinates for our models. We find that the inner and outer spiral wakes of massive protoplanets (M>5 M_jup) produce significant shock heating that can trigger buoyant instabilities. These drive sustained turbulence throughout the disk when they occur. The strength of this effect depends strongly on the mass of the planet and the thermal relaxation timescale; for a 10 M_jup planet embedded in a thin, purely adiabatic disk, the spirals, gaps, and vortices typically associated with planet-disk interactions are disrupted. We find that the effect is only weakly dependent on the initial radial temperature profile. The spirals that form in disks heated by the effects we have described may fit the spiral structures observed in transition disks better than the spirals predicted by linear isothermal theory.Comment: 10 pages, 8 figures. ApJ, accepte

Compositional Set Invariance in Network Systems with Assume-Guarantee Contracts

This paper presents an assume-guarantee reasoning approach to the computation of robust invariant sets for network systems. Parameterized signal temporal logic (pSTL) is used to formally describe the behaviors of the subsystems, which we use as the template for the contract. We show that set invariance can be proved with a valid assume-guarantee contract by reasoning about individual subsystems. If a valid assume-guarantee contract with monotonic pSTL template is known, it can be further refined by value iteration. When such a contract is not known, an epigraph method is proposed to solve for a contract that is valid, -an approach that has linear complexity for a sparse network. A microgrid example is used to demonstrate the proposed method. The simulation result shows that together with control barrier functions, the states of all the subsystems can be bounded inside the individual robust invariant sets