The design and building of new alternative fuel plants is an increasing necessity to replace old technology and non-renewable fossil fuels. To optimize the performance of these plants and to obtain an economically fea...The design and building of new alternative fuel plants is an increasing necessity to replace old technology and non-renewable fossil fuels. To optimize the performance of these plants and to obtain an economically feasible production of these types of fuels, it is necessary to have a total control of each variable involved in the process of production and how these factors affect the yield of fuel production. In this paper it is proposed a model of a digester to generate gas using a Vensim software designed to generate simulations in dynamic state. This simulation was developed using differential equations to model the behavior at each stage of the process and auxiliary conditions to complement the mathematical description of the model. The main factors in the biogas production are the retention time and the methanogen mortality ratio. For retention time lower than 10 h the process loses effectiveness due to bacterial growth is not completed efficiently, but a high retention time involves a bigger reactor and the yield of production decreases considerably for retention time higher than 40 h. The best yields were obtained for a mortality ratio in methanogen and acidogenic bacteria lower than 0.2 and a retention time of 30 h with a final production of 3.33 L by each kilogram of biomass.展开更多
In the present paper, the results from research on the influence of criteria （factors） such as depreciation method, materiality threshold, and inflation rate on the selection of depreciation policy are shown. The re...In the present paper, the results from research on the influence of criteria （factors） such as depreciation method, materiality threshold, and inflation rate on the selection of depreciation policy are shown. The research has been carried out with the help of specifically devised simulation models. The simulation is realized in accounting for the unevenness of money in time and the profitability of the company, the tax rates for corporate tax, and the inflation rate. The models have been devised after analyzing methodology issues, related to depreciation policy and investigating current practices in its implementation in specific agricultural companies in present-day Bulgaria. It has been determined that there is a clear-cut relation between the profitability of the companies and the materiality threshold and depreciation method chosen. The main conclusion is that when the companies develop their depreciation policy, at ceteris paribus they should select higher materiality thresholds and diminishing balance depreciation methods due to the inequality of money in time, the acceleration of obsolescence, and the inflation processes.展开更多
文摘The design and building of new alternative fuel plants is an increasing necessity to replace old technology and non-renewable fossil fuels. To optimize the performance of these plants and to obtain an economically feasible production of these types of fuels, it is necessary to have a total control of each variable involved in the process of production and how these factors affect the yield of fuel production. In this paper it is proposed a model of a digester to generate gas using a Vensim software designed to generate simulations in dynamic state. This simulation was developed using differential equations to model the behavior at each stage of the process and auxiliary conditions to complement the mathematical description of the model. The main factors in the biogas production are the retention time and the methanogen mortality ratio. For retention time lower than 10 h the process loses effectiveness due to bacterial growth is not completed efficiently, but a high retention time involves a bigger reactor and the yield of production decreases considerably for retention time higher than 40 h. The best yields were obtained for a mortality ratio in methanogen and acidogenic bacteria lower than 0.2 and a retention time of 30 h with a final production of 3.33 L by each kilogram of biomass.
文摘In the present paper, the results from research on the influence of criteria （factors） such as depreciation method, materiality threshold, and inflation rate on the selection of depreciation policy are shown. The research has been carried out with the help of specifically devised simulation models. The simulation is realized in accounting for the unevenness of money in time and the profitability of the company, the tax rates for corporate tax, and the inflation rate. The models have been devised after analyzing methodology issues, related to depreciation policy and investigating current practices in its implementation in specific agricultural companies in present-day Bulgaria. It has been determined that there is a clear-cut relation between the profitability of the companies and the materiality threshold and depreciation method chosen. The main conclusion is that when the companies develop their depreciation policy, at ceteris paribus they should select higher materiality thresholds and diminishing balance depreciation methods due to the inequality of money in time, the acceleration of obsolescence, and the inflation processes.
