Modelling anaerobic digestion during temperature and load variations

Experimental results and simulations based on the Anaerobic Digestion Model No.1 (ADM1) with temperature effects on kinetics were used to evaluate rate limiting steps in sludge bed anaerobic digestion (AD) during load and temperature variations. Simulations were carried out in Aquasim. The model is compared to data from a pilot experiment in a 220 liter AD sludge bed reactor treating diary manure for 16 months of various loads; 0–13 kg COD L−1 d−1 and various temperatures; 25°C, 30°C and 35°C. Methane and CO2 production were monitored on-line while soluble and particulate organic carbon, pH and volatile fatty acids were measured on regularly collected inlet and effluent samples. Simulated overall soluble and particulate organic carbon removal, methane and CO2 production, pH and acetate are close to measured values while propionate is underestimated during some transitions. The fit is mainly sensitive to the composition of the feed in terms of relative amounts of lipids, proteins and carbohydrates especially at simultaneously high load and low temperature. During such conditions, the model predicts accumulation of long chained fatty acids (LCFA), suggesting that the degradation of LCFA is the rate-limiting step at low temperatures. This effect is not explained by reduced LCFA solubility at lower temperature. The model predicts that sludge bed AD efficiency on substrates with little or no LCFA is independent of temperature between 25°C and 35°C while LCFA degradation is favoured by higher temperature.The project was supported by the Norwegian Agricultural Agency, Innovation Norway, The Research Council of Norway, Ministry of Education and Research and Telemark University College

Rotating effects on the scalar field in the cosmic string spacetime, in the spacetime with space-like dislocation and in the spacetime with a spiral dislocation

In the interface between general relativity and relativistic quantum mechanics, we analyse rotating effects on the scalar field subject to a hard-wall confining potential. We consider three different scenarios of general relativity given by the cosmic string spacetime, the spacetime with space-like dislocation and the spacetime with a spiral dislocation. Then, by searching for a discrete spectrum of energy, we analyse analogues effects of the Aharonov-Bohm effect for bound states and the Sagnac effect.Comment: 12 pages, no figure. To be published in The European Physical Journal

Coulomb-type interaction under Lorentz symmetry breaking effects

Based on models of confinement of quarks, we analyse a relativistic scalar particle subject to a scalar potential proportional to the inverse of the radial distance and under the effects of the violation of the Lorentz symmetry. We show that the effects of the Lorentz symmetry breaking can induced a harmonic-type potential. Then, we solve the Klein-Gordon equation analytically and discuss the influence of the background of the violation of the Lorentz symmetry on the relativistic energy levels.Comment: 10 pages, no figur

Profitability of the Management Consulting Industry in Norway : An empirical study of factors influencing the profitability of the management consulting industry in Norway

Building on resource-based view (RBV) as a theoretical foundation, the purpose of this thesis is to identify and investigate firm specific factors influencing the profitability of management consulting firms operating in Norway. The investigated variables are firm size, firm age, growth rate, productivity, location and lagged profitability. Consequently, the dependent variable is profitability, measured by ROA. The source of data used in this study is secondary data from the database Proff Forvalt in the period 2014-2021. The regression analysis shows that there is a significant relationship for the variable growth rate, productivity, and lagged profitability on profitability. The results of the regression coefficient indicates that growth rate, productivity and lagged profitability have a positive influence on profitability. The empirical results suggest that productivity is the most significant determinant of profitability. No statistically significant relationship was found for the variable firm size, firm age and location on profitability. The lack of significance can be due to several factors that characterize the management consulting industry. Such as, high employee turnover, high flow of experience and digitalization. The nature of the industry counteracts the potential positive relationship of firm size, firm age and location on profitability. This study provides further empirical evidence in a research area where previous studies have conflicting findings, by investigating an unexplored context. Our study uses theories from the RBV in order to better understand the conflicting findings in this research area.nhhma