The prospect of using LES and DES in engineering design, and the research required to get there

In this paper we try to look into the future to divine how large eddy and detached eddy simulations (LES and DES, respectively) will be used in the engineering design process about 20-30 years from now. Some key challenges specific to the engineering design process are identified, and some of the critical outstanding problems and promising research directions are discussed.Comment: accepted for publication in the Royal Society Philosophical Transactions

Likelihood-Based Inference in Multivariate Panel Cointegration Models

This paper presents a general likelihood-based framework for inference in panel-VAR models with cointegrating restrictions. The cointegrating relations are restricted to each cross-section while the rest of the model is unrestricted. The homogenous restriction of common cointegrating space is also considered. Asymptotic distributions of parameter estimates and the test statistics for the cointegrating rank and the homogenous restriction are derived. The distribution for the cointegrating rank is shown to be the convolution of the standard distribution of the trace statistic and the chi$^2$ distribution. The homogenous restriction test statistic is chi$^2$. A Monte Carlo simulation investigates the small sample properties of the two tests. The empirical size of the test for the cointegrating rank is well above the nominal. A Bartlett corrected test statistic is shown to have size very close to the nominal. We give an empirical example for a consumption model including consumption, income and inflation.

Mer än bara blommor

Förutsättningar för biologisk mångfald i urbana, privata trädgårdar kan undersökas på flera sätt. I denna litteraturstudie används två olika perspektiv. Ur ett större perspektiv undersöks bland annat trädgårdens roll i landskapet och vilka faktorer som påverkar förutsättningarna för biologisk mångfald i trädgården. Ur ett snävare perspektiv undersöks dessutom vanligt förekommande trädgårdskomponenter och deras direkta och indirekta effekter på biologisk mångfald. Resultaten visar att privata, urbana trädgårdar och deras komponenter kan vara viktiga för att främja biologisk mångfald, men även att det finns potentiella hinder i form av trädgårdarnas allt minskande genomsnittliga storlek samt föränderligheten i privata trädgårdar. Faktorer som påverkar utformningen och skötseln – och därmed förutsättningarna – i trädgården är bland annat trender och grannskapets påverkan.The basis for evaluating urban, domestic gardens’ effects on biological diversity could be approached from several different perspectives. This particular study highlights two possible approaches. On a larger scale, the role of an individual garden within an entire landscape and factors affecting the conditions for biological diversity in gardens are examined. Furthermore, on a finer scale, the direct and indirect impact of common garden features upon biological diversity is assessed. The results indicate the importance of private urban gardens and their structural characteristics have upon promoting biological diversity whilst simultaneously highlighting problems associated with the continuous downsizing and variability of urban gardens. Factors that affect the conditions for biological diversity could be trends as well as the neighbourhood impact on the design and management of individual gardens

Estimation of dialysis treatment efficiency by means of system identification

When treating patients suffering from renal failure with hemodialysis, an obvious point of interest is the actual blood cleaning efficiency of the dialyzer (artificial kidney). This efficiency is called clearance or dialysance. The method currently used for estimating clearance is based on doing a step-change on the process. Due to the nature of the process, this method is slow and has a relatively large output spread. This master thesis investigates a new method of finding clearance by means of system identification. The dialyzer is modelled as a discrete-time system, and perturbed by use of a pseudo-binary random sequence. The input/output-data is then fed into an optimal Kalman filter for parameter estimation. The gain and offset of the identified system is directly related to the dialyzer clearance of the treatment. The method shows promising results, usually converging to good parameters within 15 minutes, and then tracking changes continuously for the rest of the treatment. It also provides better accuracy, with a considerable reduction in spread compared to the old method. Main obstacles stem from variable time-delays in the system and measurement offsets

Tailoring the self-assembly, interfacial properties and rheological behaviour of sugar-based surfactants

Surfactants are important ingredients in many formulated products used in everyday life. Many of these surfactants originates from fossil-based materials and degrades slowly in aquatic systems. As society strives towards having a smaller environmental footprint, surfactants that are non-toxic, biodegradable and can be synthesized from renewable raw materials need to be developed. To this end sugar-based surfactants, or alkylglycosides, is a promising class of surfactants that have the properties that are sought after. To utilize these surfactants to their full potential more knowledge is required about their behaviour both at interfaces and in solution.In this thesis the behaviour of the alkylglycoside C16G2, and how it is affected by small changes in its molecular structure, has been studied with scattering techniques and rheometry. The anomeric configuration was found to have a large impact as β-C16G2 allowed for a more efficient packing of the headgroup, compared to α-C16G2. This is apparent both at interfaces, where the adsorption was higher for the β anomer, and in solution, where β-C16G2 forms very elongated worm-like micelles while α-C16G2 forms shorter cylindrical micelles. The difference in self-assembly affects the rheological behaviour of these solutions where highly viscous, shear thinning and viscoelastic properties reflects the long micelles of β-C16G2, while solutions of α-C16G2 are Newtonian with low viscosity. The effect of introducing a double bond in the tailgroup of β-C16G2 was also investigated, where a significant decrease in Krafft point was seen, while the formation of worm-like micelles and viscous solutions was still evident

eulerr: Area-Proportional Euler Diagrams with Ellipses

Euler diagrams are common and intuitive visualizations for data involving sets and relationships thereof. Compared to Venn diagrams, Euler diagrams do not require all set relationships to be present and may therefore be area-proportional also with subset or disjoint relationships in the input. Most Euler diagrams use circles, but circles do not always support accurate diagrams. A promising alternative for Euler diagrams is ellipses, which enable accurate diagrams for a wider range of set combinations. Ellipses, however, have not yet been implemented for more than three sets or three-set diagrams where there are disjoint or subset relationships. The aim of this thesis is to present a method and software for elliptical Euler diagrams for any number of sets. In this thesis, we provide and outline an R-based implementation called eulerr. It fits Euler diagrams using numerical optimization and exact-area algorithms through two steps: first, an initial layout is formed using the sets' pairwise relationships; second, this layout is finalized taking all the sets' intersections into account. Finally, we compare eulerr with other software implementations of Euler diagrams and show that the package is overall both more consistent and accurate as well as faster for up to seven sets compared to the other R-packages. eulerr perfectly reproduces samples of circular Euler diagrams as well as three-set diagrams with ellipses, but performs suboptimally with elliptical diagrams of more than three sets. eulerr also outperforms the other software tested in this thesis in fitting Euler diagrams to set configurations that might lack exact solutions provided that we use ellipses; eulerr's circular diagrams, meanwhile, fit better on all accounts save for the diagError metric in the case of three-set diagrams