University of Architecture, Civil Engineering and Geodesy

About: University of Architecture, Civil Engineering and Geodesy is a education organization based out in Sofia, Bulgaria. It is known for research contribution in the topics: Finite element method & Beam (structure). The organization has 3808 authors who have published 3822 publications receiving 30736 citations. The organization is also known as: Sofia Polytechnic.

Multi-agent cooperation by reinforcement learning with teammate modeling and reward allotment

Abstract: How to coordinate the behavior of different agents through learning is a challenging problem within multi-agent domains. This paper addressed a kind of reinforcement learning algorithm to learn coordinated actions of a group of cooperative agents. This algorithm combines advantages of teammate modeling and reward allotment mechanism in a multi-agent Q-learning framework. The effectiveness of the proposed algorithm is demonstrated using the hunting game.

Influence of different curing temperatures on mechanical properties of alkali activated silica fume and fly ash based geopolymer

Abstract: Alkali activated silica fume and fly ash based geopolymer (ASFG) were prepared through vibromoulding process, the optimum mix amount of silica fume and influence of different curing temperatures of room temperature (RT), 60, 80 and 210°C on the mechanical properties of ASFG were evaluated respectively. Results of mechanical properties shown silica fume could reinforce and toughen alkali activated fly ash based geopolymer, and the optimum additive amount of silica fume was 10 wt-% as the starting materials in various curing systems. The results of mercury intrusion porosimetry and scanning electron microscope showed that the smaller pore volume of ASFG decreased with increasing curing temperatures and formed amorphous porous network structure due to accelerated geopolymerisation; the weight loss decreased gradually and temperatures of weight loss improved with increasing curing temperatures derived from the increased content of bound water through the results of thermogravimetric analysis.

Minimizing local drag by shaping a flanged slotted hood along the boundaries of vortex zones occurring at inlet

Abstract: Effective trapping of dust and gas emissions in civil and industrial buildings relies on energy-consuming local exhaust ventilation systems. Electricity consumption can be reduced by shaping exhaust hoods after boundaries of vortex zones that occur in these systems. This paper purports to determine how can the local drag coefficient (LDC) of a slotted hood be affected by shaping its inlet edges along the boundaries of vortex zones identified with different flange inclination angles and lengths. We show that flange length and tilt angle determine the efficiency of LDC reduction. The greatest decline in LDC, as high as 98%, is observed when a slotted hood perpendicular to its walls is shaped along vortex zone boundaries determined using the discrete vortex method. In contrast, when vortex zones determined by computational fluid dynamics (CFD) methods are used for shaping, the vortex cascade effect appears: shaping after the first vortex zone brings about a secondary vortex zone, shaping after the secondary zone results in another one etc. The efficiency of existing slotted hoods can be improved with ad-hoc inserts or duct walls shaped along the identified vortex zone boundaries. This improvement was confirmed experimentally for a flangeless hood.

Metabolism and mechanism of toxicity of selenium-containing supplements used for optimizing human selenium status

Abstract: The work presents a review devoted to the metabolism and the mechanism of toxicity of seleniumcontaining supplements: elemental selenium, sodium selenite, diacetophenonyl selenide, selenopyrane, ebselen, dimethyl dipyrasolyl selenide and selenium-containing amino acids used for correction of selenium deficiency. Elemental selenium penetrating through cell walls, but not through transport channels demonstrates poorly predicted and difficultly regulated bioavailability. Sodium selenate is known to be the most toxic form of selenium in food. The metabolism of xenobiotic diacetophenonyl selenide resembles that of sodium selenide. The xenobiotic reacts with thiols, for instance, with the reduced form of glutathione leading to the formation of hydrogen selenide. Ebselen is not considered to be a well bioavailable form of selenium and thus possesses low toxicity. Xenobiotic selenopyrane eliminates selenium only in processes of xenobiotic liver exchange, and in our investigations - partially in acid-catalyzed hydrolysis. The metabolism of xenobiotic dimethyl dipyrasolyl selenide having low toxicity is poorly investigated. The toxicity of high doses of selenomethionine is determined by the possibility of incorporation in proteins and vitally important enzymes with dramatic changes of protein quaternary structure. The toxicity of high doses of methylselenocysteine seems to be caused by the lack of an exchange pool in the body and quick regeneration of hydrogen selenide from methylselenol which is formed as a result of enzymatic destruction of this amino acid. Also the issue of the most prospect selenium donor is discussed. The physiological compatibility, the low toxicity, the presence of an exchangeable pool in the organism, the antioxidantal properties and the simplicity of production indicate selenocystine as an optimal selenium donor.