The correct evaluation of reliability for the system or components is very important for high quality and security. The traditional models take stress and strength as the static random variable without considering the effect of strength degradation. The effect of strength degradation on the reliability of a gear was studied in this paper. With the conditional reliability introduced, a reliability calculation model of gear with multiple failure modes is developed by using the stress-strength interference model, without the assumption that there was independent failure mode of gear. The reliability model of a gear under the strength degradation is developed based on the model. And the dependence of gear reliability on the strength degradation is studied. The result shows that the gear reliability decreases with the strength degradation due to fatigue, corrosion, aging and other factors.
Coagulation is the most important and difficult step in water treatment, it influences the whole process. The coagulation condition is based on many factors. Adding coagulants is the key factor. The stability of colloids in water depends on its Zeta potential, the higher potential the colloid has, the more stable the colloid is. The value of streaming current creates by the Zeta potential of colloid indicates the coagulation condition. Using the monitor to on-line test, and output a standard direct current signal, then the PID regulator control the frequency converter to change the dosage, and finally realize the best coagulation condition.The automation system using the theory of streaming current, consisting of the sensor of the streaming current one-factor monitor, the control equipments, the frequency converter and the bumps for adding coagulants. The electrode testes the streaming current at the testing container, the sensor outputs a streaming current signal standing for the colloid condition, then the control equipments contrasts with designed value and makes a judgment, and then outputs a standard signal of 4-20 mA to the PID regulator, controlling the frequency converter to meat the corresponding condition, and adding coagulant into water at suitable dosage. The automation system sketch is showed as follows.
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