Modeling and simulation of substation fault diagnosis based on Petri nets
In order to improve the efficiency of the substation fault diagnosis with multiple protections, the proposed method describes protection grades by varied weight of the transition vector in the Petri net models. According to relays and circuit breakers, special markings are produced in the diagnosis results that enhance the identifying capability of error information. The process of fault diagnosis is accomplished by algebra matrix calculation. A simulation on actual substation fault diagnosis process indicates that the improved method has fast calculation speed and high veracity
Power system monitoring using Petri net embeddings
A failure in a power transmission line causes a number of circuit breakers to activate in an effort to isolate the failure and prevent it from corrupting the rest of the power system. Based on information from these physically distributed protective devices, a central controller needs to quickly locate and identify the failure. The task becomes challenging due to the complexity of modern power transmission networks and due to the possibility of sensor failures or incorrect operation of protective devices. A solution to this problem is investigated using Petri net models. Our approach allows concurrent/incremental processing of the information that arrives at the controller and only requires simple calculations (linear checks) during execution time. Most reasoning is implicitly performed at design time, which gives our method an important edge for real-time monitoring. These same techniques can potentially handle multiple failures or perform hierarchical and/or distributed monitoring.
Cross talk between redox signalling and metabolic activity of osteoblasts and fibroblasts in the presence of hydroxyapatite-based biomaterials influences bone regeneration
Regeneration of bone tissue defects that result from metabolic disorders, including periodontal diseases, can be supported by biomaterials based on hydroxyapatite. Despite of good biocompatibility of biomaterials they can cause oxidative stress and inflammatory processes as a result of mechanical interaction with surrounding tissues. Because osteoblasts are responsible for bone regeneration process in which gingival fibroblasts may also participate, the aim of the work was to investigate the influence of hydroxyapatite-based biomaterials (allogeneic and xenogeneic) and biomaterials combined with enamel matrix derivative (Emdogain) on osteoblast and fibroblast redox balance in the context of osteoblast proliferation and differentiation.
The results showed that examined substitutes were not cytotoxic in vitro, but affected redox balance of osteoblasts and fibroblasts (ROS level increase and GSH level decrease) which led to oxidative stress (MDA and protein carbonyl groups level increase) resulting in an increase of the Nrf2 and NFκB expression. The consequence of these changes was partial inhibition of proliferation and osteoblast differentiation. Emdogain alone and combined with biomaterials decreased ROS generation and increased GSH level in both osteoblasts and fibroblasts leading to reduction of transcription factors expression especially proinflammatory NFκB, which promoted osteoblast differentiation and mineralization process.