Corrosion products which occupy much greater volume accumulate, and generate expansive pressures on the surrounding concrete. The pressure builds up and eventually leads to the cover cracking of the structures. The cracking accelerates further corrosion and leads to the loss of the bond strength and the load carrying capacity. Corrosion cracking would reveal the reducing of the residual service life of the corrosion-affected structures. In this paper, an analytical model is proposed to predict the critical corrosion penetration at cover cracking in RC structures based on the crack process. An attempt has been made to develop the model by considering material properties of the surrounding concrete and expansive corrosion products. The problem is established as a boundary-value problem and the governing equations are expressed in terms of the radial displacement. The analytical predictions of the proposed model have also been in agreement with the available experimental data.
This paper proposes a new application of dynamic particle swarm optimization (PSO) algorithm for parameter identification of vector controlled asynchronous propulsion motor (APM) in electric propulsion ship. The dynamic PSO modifies the inertia weight, learning coefficients and two independent random sequences which affect the convergence capability and solution quality, in order to improve the performance of the standard PSO algorithm. The standard PSO and dynamic PSO algorithms use measurements of the mt-axis currents, voltages of APM as the inputs to parameter identification system. The experimental results obtained compare the identified parameters with the actual parameters. There is also a comparison of the solution quality between standard PSO and dynamic PSO algorithms. The results demonstrate that the dynamic PSO algorithm is better than standard PSO algorithm for APM parameter identification. Dynamic PSO algorithm can improve the performance of ship propulsion motor under abrupt load variation.
In processing food wastes, odorous gases are generated, which significantly affect the workers and occupants in the plant. This study applies gas chromatography-mass spectrometry and chemical methods to analyze qualitatively and quantitatively the characteristics of odorous gases in the workshop, in order to find the composition and pollution level of odorous gases emitted from municipal food waste. The research results showed that the common compositions in the food waste gases were dimethylacetamide, naphthalene, methylnaphthalene, phenol and limonene, which the tested probability is 100%. Based on the comparison of odor concentration and threshold at four sampling sites, it can be concluded that ethyl thioether, trimethylamine, ethylbenzene and citric acid were major gases that belonged the standard threshold. Both odor intensity and activity of trimethylamine and ethyl thioetherwere highest, which odor intensity were 70.58 and 1.79, as well as odor activity were 2.25 and 1.79, separately. Therefore, the compounds attributed to the odor gases in food waste weretrimethylamine and ethyl thioether.
With the constant emerging of novel Internet applications, weak real-time application has gradually become the mainstream of today's Internet business. According to the characteristics and requirements of weak real-time business, this paper conducts modeling analysis on disk scheduling of weak real-time I/O requests, and gets a multi-objective optimization model of this problem, and further puts forward a heuristic weak real-time business disk scheduling strategy WRT-DSS. Experiments show that the WRT-DSS strategy can take both quality of service and throughput performance of disk storage system into consideration. According to the demand of practical scenario, WRT-DSS can make an appropriate tradeoff on the system real-time and throughput performance via the flexible adjustment of the weighting coefficients.
In the fields of using green energy such as PV system and Wind power system, the step-up DC-DC converter, witch is used to convert the power, is now attracting more and more attention. The response characteristics and stability of one are key points for the performance of the whole system. However, it is complex to analyze the dynamic characteristics and control design. In this paper, the dynamic model of full-bridge DC-DC converter is presented, and transfer functions of the converter are derived by using state-space averaging method. And then the improved PI controller is designed. Finally, a laboratory prototype circuit with input voltage 220V, output voltage 600V is implemented and results are shown to confirm the validity of the designed switching device.
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