With the popularity of Web services technology, the amount of the Web services resources is on the increase. It is well-known that the semantic Web technologies can bring the Web services into effect better, so the academia and enterprises give more and more attentions to the semantic Web technologies. But the semantic Web technologies have to face some difficulties below: the abilities of semantic description is inadequate so that the Web services resources do not have enough the semantic information, and it is hard to support the running of diversified system software and application software. In order to solve these problems, this article introduces a framework of semantic software, proposes a model named RDF4S (recourse description framework for service). It's describe Web service through adding semantics annotation based on ontology. Compared with other description model, the main advantage consists in its flexibility caused by RDF4S.
As for turbine rotor, the simple stress on-line monitoring models of rotors temperature and thermal stress based on Greens function method are obtained. Using perturbation method, the models can deal with nonlinear problems resulting from temperature dependent properties. The working medium temperature change curve and the temperature rising rate curve during the period of startup or shutdown at shortest time for unit can be obtained to reduce fatigue wastage by analyzing the startup or shutdown process of a unit plant with the Pontryagin Maximum Principle of optimal control theory. The temperature rising rate curve thus obtained can be used not only as a guide for operation, but also as a programmable control signal for the startup and shutdown process of generating units, which will improve the economy of a power plant.
Nowadays, numbers of supercritical steam turbines made in domestic with 600MW capacity have been put into operation in China. The safety of these units will have great impact on the safety and stability of the network. The features of these units, such as constructions, governing modes and system arrangements receive much more attentions. This paper analyzes the characteristics of oil system of supercritical 600MW steam turbine made in domestic from following aspects: lube oil system and EH oil supply system etc.
Analysis and simulation of fluid–thermal–structure coupling play an essential role in hypersonic flight vehicle design. In this study, the spectral proper orthogonal decomposition (SPOD) method is employed to establish the reduced-order model (ROM) for a hypersonic panel with a thermal protection system. First, the subsystem of the aerothermoelastic (AETI) system is modeled. Specifically, the aerodynamic heating is calculated with Eckert’s reference enthalpy method. The heat transfer is carried out with the finite difference method, and the aeroelastic equation is built by integrating the von Kármán plate theory and the third-order piston theory. Additionally, the two-way coupling between aerothermal and aeroelastic subsystems is used to construct the AETI system. Second, the optimal snapshots with the resultant local SPOD modes (SPOMs) are evaluated in terms of accuracy. Third, the global SPOMs for variable flight parameters are promoted to develop the robustness of the proposed SPOD/ROM. The findings indicate that taking the transient chaotic response as snapshots can produce global SPOMs. SPOD/ROM for the present AETI system improves the efficiency by 10–50 times compared to the classic Galerkin method. Moreover, the global SPOMs to variable Mach number and flight altitude are essentially the natural modes of the AETI panel, and thus are dependent on the temperature of the fluttering panel, which is our new finding in the present study. Overall, the current research will provide methods for accurately and efficiently predicting thermal loads, flutter boundary, and dynamic response for hypersonic flight vehicles.
In this work, an efficient nonlinear state-space reduced-order model (ROM) is introduced. The nonlinear state-space ROM consists of both linear terms and nonlinear terms, the former of which is obtained based on Volterra series theory and eigensystem realization algorithm method, whereas the latter is determined by an output error-minimization procedure. Two approaches are proposed to determine the training signal for identification of the nonlinear terms. Aeroelastic analysis of a weakened wall-mounted AGARD 445.6 wing is conducted and it is demonstrated that 1) the nonlinear state-space ROM can get more accurate unsteady aeroelastic response than traditional linear Volterra-based ROM with computational fluid dynamics coupling with computational structural dynamic as a reference method for comparison; 2) the nonlinear state-space ROM performs well in range of subsonic, transonic, and supersonic; and 3) the nonlinear state-space ROM can better characterize the nonlinear aeroelastic system than traditional linear Volterra-based ROM without the need of identifying second-order Volterra kernels, which thus can be easily applied to solve engineering problems for its concise form.
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