New method for assessing the performance of agricultural biogas plants

Around 5000 agricultural biogas plants were operating in Germany by the end of 2009. There is a recognized need for their assessment, comparison and performance improvement. Prerequisites for their reliable assessment include: 1) detailed and reliable performance data, 2) defined criteria for the assessment, and 3) comprehensive method. The limitations of existing assessment methods have been reviewed. The new method developed for assessing the overall performance of biogas plants is focused on four assessment aspects: biogas production, biogas utilization, environmental impact and socio-economic efficiency. Each assessment aspect was determined by two performance criteria. The method is based on fuzzy set theory and fuzzy mathematics, which enables use of imprecise and uncertain data. Incorporation of enough expertise from the field of biogas technology was enabled in this method as well. Pre-assessment of future biogas plants in their planning phase is possible, contributing to their effective development. The reliability of the method was tested using data from ten monitored biogas plants. The assessment of the ten biogas plants showed that biogas utilization is the aspect with the largest potential for performance improvement, by increasing the external heat utilization. The method developed is adjustable to accommodate new developments related to biogas technology and biogas plants in any geographical region. Future research should be focused on definition and inclusion of more assessment criteria and on developing the methods that are capable to handle compensation between individual criteria.     

Large-scale concept ontology for multimedia

As increasingly powerful techniques emerge for machine tagging multimedia content, it becomes ever more important to standardize the underlying vocabularies. Doing so provides interoperability and lets the multimedia community focus ongoing research on a well-defined set of semantics. This paper describes a collaborative effort of multimedia researchers, library scientists, and end users to develop a large standardized taxonomy for describing broadcast news video. The large-scale concept ontology for multimedia (LSCOM) is the first of its kind designed to simultaneously optimize utility to facilitate end-user access, cover a large semantic space, make automated extraction feasible, and increase observability in diverse broadcast news video data sets.     

The analysis of the renewable energy production sector in Serbia

Producing energy from renewable sources in Serbia is in its initial phase, and therefore this paper points towards the basic assumptions, potentials and institutional framework for the development of this activity in Serbia. Until recently, production and consumption of energy in Serbia was a social category, but the shift towards market economy together with the fact that Serbia has adopted Kyoto protocol, production of energy from renewable sources became a competitive and obligatory activity. Research shows that the current potentials for producing energy from renewable sources in Serbia are favorable. Besides this, the paper provides an overview of the existing institutional structure in the energy sector in Serbia, but also the short overview of the adequate legal acts. Researches that were done so far have proven that energy potentials of Serbia are insufficiently known and therefore authors will give an overview of the foreign investments in this sector and reveal the possibilities for further investing. Considering the existing know-how base and potentials for the production of equipment, geothermal energy and energy coming from biomass have been identified as priority renewable sources of energy. Producing energy from other renewable sources is also possible, but would require substantial foreign investments. As a final conclusion, the paper states that completely unused potentials for production of energy from renewable sources, together with adequately set institutional framework, would create great possibilities for foreign investments.     

Exact collision detection for a virtual manufacturing simulator

Collision detection is a critical aspect of Virtual Reality (VR)-based simulation of manufacturing processes. Despite the significant progress that has been made in developing efficient, exact collision detection algorithms for convex objects, limited and slow progress has been reported in developing collision detection algorithms for general, nonconvex objects. To narrow this gap we introduce the concept of virtual objects which extends the applicability of exact collision detection algorithms to nonconvex objects. The outcome of our methodology is the fast creation of convex objects for a class of frequently encountered nonconvex manufacturing objects that can be used in any existing collision detection approach. The collision detection technique described in this paper is best suited for interactive simulation and animation applications where a high accuracy of object contact modeling is required. Examples include virtual assembly; mobile robot simulation; robotic painting; robotic welding; and coordinate measuring processes.     

Aging Induces Tissue-Specific Changes in Cholesterol Metabolism in Rat Brain and Liver

Disturbance of cholesterol homeostasis in the brain is coupled to age-related brain dysfunction. In the present work, we studied the relationship between aging and cholesterol metabolism in two brain regions, the cortex and hippocampus, as well as in the sera and liver of 6-, 12-, 18- and 24-month-old male Wistar rats. Using gas chromatography-mass spectrometry, we undertook a comparative analysis of the concentrations of cholesterol, its precursors and metabolites, as well as dietary-derived phytosterols. During aging, the concentrations of the three cholesterol precursors examined (lanosterol, lathosterol and desmosterol) were unchanged in the cortex, except for desmosterol which decreased (44 %) in 18-month-old rats. In the hippocampus, aging was associated with a significant reduction in lanosterol and lathosterol concentrations at 24 months (28 and 25 %, respectively), as well as by a significant decrease of desmosterol concentration at 18 and 24 months (36 and 51 %, respectively). In contrast, in the liver we detected age-induced increases in lanosterol and lathosterol concentrations, and no change in desmosterol concentration. The amounts of these sterols were lower than in the brain regions. In the cortex and hippocampus, desmosterol was the predominant cholesterol precursor. In the liver, lathosterol was the most abundant precursor. This ratio remained stable during aging. The most striking effect of aging observed in our study was a significant decrease in desmosterol concentration in the hippocampus which could reflect age-related reduced synaptic plasticity, thus representing one of the detrimental effects of advanced age.     

Simple voltage-to-frequency convertor with increased frequency range

Conventional free-running multivibrators are frequently used as voltage-to-frequency convertors, although the fmax/fmin ratio of this circuit is rather small. A free-running multivibrator with complementary transistors has advantages concerning this ratio as well as regards some other convertor parameters.     

High-frequency phase detector

A phase detector of high sensitivity and stability is described. This detector is designed for 30 Mc/s operation. Both the reference voltage and the control of the phase of the signal voltage are obtained by means of very simple transistorised circuits.