The design of electric cranes requires knowledge of not only the dynamic loads acting on the mechanisms and the structure, and the movement of the crane and payload during their various operations, but also the electromagnetic characteristics of the control system. This article puts forward a new comprehensive dynamic model for the whole system of electric cranes, which includes the mechanisms, the steel structure, the induction motors, and their drive systems. A general electric overhead travelling crane controlled by two types of control schemes (of changing the rotor resistance and the closed-loop rotor-flux-oriented vector control) during the operation of its lifting mechanism is studied. Hamilton's principle with a modified Lagrangian, and the theory of induction motors and drive systems are combined to build a dynamic model of electric cranes during lifting operations. This model aims at simulating the dynamic behaviour of the mechanical and structural systems for the transient and steady-state behaviour of the induction motors and their control during the operations of a real crane. It can be seen that the dynamic system of the whole crane is highly non-linear and non-stationary even for only the lifting operation.

Mechanical brakes are essential for electric cranes when emergency braking occurs. This paper presents, for the first-time, a dynamic response analysis of emergency braking events of electrical cranes that has modelled crane components as flexible and rigid bodies. Based on the Hamilton principle, a nonlinear and non-smooth dynamic model is derived from a modified Lagrangian function and the virtual work of non-conservative forces. The dynamic responses of a 32-ton overhead travelling crane during the emergency braking process of its lifting mechanism with two service brakes determined by simulating realistic operations. The numerical results show that the loads acting on components of the crane during the braking process depend on the braking capacity and the action time of the mechanical brakes, as well as the magnitude and the initial position of the payload. When a dual-brake scheme of the lifting mechanism is adopted, the maximum load of the high-speed links and the maximum thermal power of the mechanical brake appear in the emergency braking process when one of the two brakes fails to work. In addition, it is found to be a false belief that the lower the initial speed, the lower the maximum loads acting on components of cranes become during the braking process.

To conduct the reliability test or functional life test for hydraulic components usually takes more time than one can predict and consumes more resource than one can image, especially for those with higher reliability and simpler components. This paper is presented to discuss the theory and method of accelerated testing, which has been widely used in electronics field, and to discuss the factors that affect the functional life of hydraulic components as well as the failure mode. The advantage and disadvantage of accelerating testing will be discussed. The author also intends to point out the importance of failure definition and accelerating model in the accelerated tests. Several accelerating models such as Arrhenius model and Inverse Power model will be discussed. The degradation process of metering edge is taken as the research subject to propose the applicable accelerating model. The possibility of using contaminated hydraulic fluid as an accelerating factor is discussed.

The delivery system of antibiotics plays an important role in increasing the drug efficacy and reducing the risks of off-target toxicities and antibiotic resistance. The pathophysiology of bacterial infections is similar to that of tumor tissues, but only a few delivery systems have been able to target and release antibiotics on demand. Herein, we designed and developed a robust Chitosan-SS-Levofloxacin (CS-SS-LF) micelles for targeted antibiotic delivery, in which disulfide bond can be reduced by hydrogen sulfide (H2S), a typical product of Salmonella, and subsequently released antibiotic to eradicate Salmonella infection. CS-SS-LF micelles showed uniform size and sharp response to H2S. Compared with levofloxacin alone, these micelles possessed a better capacity in disrupting Salmonella biofilms and reducing bacterial burden in organs. The H2S-sensitive CS-SS-LF micelles might enable a new way to address bacterial infections.