34 resultados para DYNAMIC PORTFOLIO SELECTION
Resumo:
In this study we analyze how the ion concentrations in forest soil solution are determined by hydrological and biogeochemical processes. A dynamic model ACIDIC was developed, including processes common to dynamic soil acidification models. The model treats up to eight interacting layers and simulates soil hydrology, transpiration, root water and nutrient uptake, cation exchange, dissolution and reactions of Al hydroxides in solution, and the formation of carbonic acid and its dissociation products. It includes also a possibility to a simultaneous use of preferential and matrix flow paths, enabling the throughfall water to enter the deeper soil layers in macropores without first reacting with the upper layers. Three different combinations of routing the throughfall water via macro- and micropores through the soil profile is presented. The large vertical gradient in the observed total charge was simulated succesfully. According to the simulations, gradient is mostly caused by differences in the intensity of water uptake, sulfate adsorption and organic anion retention at the various depths. The temporal variations in Ca and Mg concentrations were simulated fairly well in all soil layers. For H+, Al and K there were much more variation in the observed than in the simulated concentrations. Flow in macropores is a possible explanation for the apparent disequilibrium of the cation exchange for H+ and K, as the solution H+ and K concentrations have great vertical gradients in soil. The amount of exchangeable H+ increased in the O and E horizons and decreased in the Bs1 and Bs2 horizons, the net change in whole soil profile being a decrease. A large part of the decrease of the exchangeable H+ in the illuvial B horizon was caused by sulfate adsorption. The model produces soil water amounts and solution ion concentrations which are comparable to the measured values, and it can be used in both hydrological and chemical studies of soils.
Resumo:
Previous research has been inconclusive regarding the impact of those who invest in entrepreneurs. Consider for a moment how potentially important they are to entrepreneurs. They for example decide who deserves funding, how much time they contribute to their portfolio firms, how they grant entrepreneurs access to their networks, and help entrepreneurs acquire additional funding. In sum, investors potentially have a great impact on the success of entrepreneurs. It is therefore important that we better understand the environment, relationships and context in which parties operate. This thesis contains five articles that explore investors’ and entrepreneurs’ relationships from various viewpoints, in theoretical frameworks, and use a variety of data and research methods. The first article is a literature review that summarises what we know of venture capital, business angel and corporate venture capital funding. The second article studies the entrepreneurs’ investor selection process, its consequences, and identifies key factors that influence the process. Earlier, the common approach has been to concentrate research on the investors’ selection policy, not the entrepreneurs’. The data and conclusions are based on multiple case studies. The article analyses how entrepreneurs can ensure that they get the best possible investor, when it is possible for an entrepreneur to select an investor, and what are the consequences of investor selection. The third article employs power constructs (dependency, power balance/imbalance, power sources) and analyses their applicability in the investor-entrepreneur relationship. Power constructs are extensively studied and utilised in the management and organisation literature. In entrepreneur investor relationships, power aspects are rarely analysed. However, having the ability to “get others to do things they would not otherwise do” is a very common factor in the investor-entrepreneur relationship. Therefore, employing and analysing the applicability of power constructs in this setting is well founded. The article is based on a single case study but suggests that power constructs could be applicable and consequently provide additional insights into the investor-entrepreneur relationship. The fourth article studies the role of advisors in the venture capital investment process and analyses implications for research and practice, particularly from the entrepreneurs’ perspective. The common entrepreneurial finance literature describes the entrepreneur-investor relationship as linear and bilateral. However, it was discovered that advisors may influence the relationship. In this article, the role of advisors, operating procedures and advisors’ impact on different parties is analysed. The fifth article concentrates on investors’ certification effect. The article measures and demonstrates that venture capital investment is likely to increase the credibility (in terms of media attention) of early stage firms, those that most often need additional credibility. Understanding investor certification can affect how entrepreneurs evaluate investment offers and how investors can make their offers appear more lucrative.