Study on the Law of Short Fatigue Crack Using Genetic Algorithm-BP Neural Networks
The initiation and propagation of short crack is a complex process of nonlinear dynamics. The material field has been concerning of the law of short crack and put forward a number of models and predictive equations. But most of them have to meet the problems which are unclear physical parameters meaning, narrow range of applications etc. That is the reason why there is not yet widely recognized quantitative model of crack evolution so far. The introduction of genetic algorithm-BP neural networks could solve those problems by avoiding building the explicit model equation and directly extracting the potential rules from the data. In this paper, the short crack for low cycle is studied under complex stress at high temperature. The material adopted in the experiment is Q245R steel. The initiation, propagation and coalescence of short crack are observed. The comparisons between experiment results and neural network simulation results show that genetic algorithm-BP neural networks simulation method can predict the law of short crack with higher prediction accuracy.
System of obstacle avoidance used in deep-seabed vehicle based on BP neural network and genetic algorithm
A real-time obstacle avoidance neural network model was created according to the real working environment of deep-seabed vehicle.An information fusion method of multi-sensor was proposed to deal with the environmental situation collected by sonar sensors used in deep-seabed vehicle,and then the input of BP neural network was realized.Watching vector,steering angle and speed of the vehicle was set as output of BP network.Tutor training signal to achieve real-time obstacle avoidance was developed based on the moving way of both vehicle and man.Then,genetic algorithm was introduced to improve the BP neural network,so the problem of incidental trap in local minima with BP neural network was overcome.The simulation results indicate that the BP neural network improved by genetic algorithm can efficiently reach the expected target,and the problem of incidental trap in local minima is modified to a large extent.The simulation result of movement of the vehicle in the environment with obstacles shown in MATLAB indicates that the method is feasible.
Mode of action of bredinin with guanylic acid on L5178Y mouse leukemia cells.
Moderate concentrations of bredinin (1.2 X 10(-5) M) strongly inhibited growth of L5178Y cells, with the effect being reversed by guanylic acid (GMP). However, at higher concentrations of breeding the inhibition was not reversed completely by GMP added in excess. Bredinin was cytocidal at concentrations above 2 X 10(-5) M, but 5 X 10(-5) M bredinin in the presence of excess GMP, bredinin was cytostatic. Bredinin inhibited nucleic acid synthesis of L5178Y cells, but bredinin itself was not incorporated into the nucleic acid. Inhibition of nucleic acid synthesis was clearly reversed by GMP. Similarly chromosomal aberrations in L5178Y cells caused by bredinin were reversed by GMP. In contrast, the effect of ahigh concentration of bredinin on cell multiplication was not reversed by GMP. The modal volume of L5178Y cells increased during incubation in the presence of bredinin and GMP for 24 hours, 5 X 10(-5) M bredinin with GMP causing a 70% increase in cell volume. This increase in cell volume was mainly due to an increase in the protein content of the cells. The cytostatic effect of bredinin with GMP was reversed completely by adenosine-3',5'-cyclic monophosphate (cyclic AMP). Other cyclic nucleotides and nucleotides were ineffective. The reversing effect of cyclic AMP on cell survival depended upon the concentration of GMP, and was not seen in the absence of GMP. It was concluded that cyclic AMP influences the secondary cytostatic effect of bredinin, and not the primary cytotoxic effect reversed by GMP.