Li YuChun, Zhang Fang, Yang ChangZhu and Bai WeiHua
This paper considers the use and application of the “grey system” modelling methodology for the prediction and characterisation of boiler water R‐values in electric power…
Abstract
This paper considers the use and application of the “grey system” modelling methodology for the prediction and characterisation of boiler water R‐values in electric power generating plants. It has been confirmed that the GM (1,1) model can pinpoint precisely the properties of the water chemistry cycle. It is considered that the grey system methodology can strengthen significantly the effectiveness of system diagnosis, thereby enabling the development and application of automated water chemistry management systems in power plants.
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Liang Zhang, Changzhu Wei, Yin Diao and Naigang Cui
This paper aims to investigate the problem of on-line orbit planning and guidance for an advanced upper stage.
Abstract
Purpose
This paper aims to investigate the problem of on-line orbit planning and guidance for an advanced upper stage.
Design/methodology/approach
The double impulse optimal transfer orbit is planned by the Lambert algorithm and the improved particle swarm optimization (IPSO) method, which can reduce the total velocity increment of the transfer orbit. More specially, a simplified formula is developed to obtain the working time of the main engine for two phases of flight based on the theorem of impulse. Subsequently, the true anomalies of the start position and the end position for both two phases are planned by the Newton iterative algorithm and the Kepler equation. Finally, the first phase of flight is guided by a novel iterative guidance (NIG) law based on the true anomaly update with respect to the geometrical relationship. Also, a completely analytical powered explicit guidance (APEG) law is presented to realize orbital injection for the second phase of flight.
Findings
Simulations including Monte Carlo and three typical orbit transfer missions are carried out to demonstrate the efficiency of the proposed scheme.
Originality/value
A novel on-line orbit planning algorithm is developed based on the Lambert problem, IPSO optimization method and Newton iterative algorithm. The NIG and APEG are presented to realize the designed transfer orbit for the first and second phases of flight. Both two guidance laws achieve higher orbit injection accuracies than traditional guidance laws.
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Panxing Huang, Changzhu Wei, Yuanbei Gu and Naigang Cui
The purpose of this paper is to propose a hybrid optimization approach with high level of solving precision and efficiency for endo-atmospheric ascent trajectory planning of…
Abstract
Purpose
The purpose of this paper is to propose a hybrid optimization approach with high level of solving precision and efficiency for endo-atmospheric ascent trajectory planning of launch vehicles.
Design/methodology/approach
Based on the indirect method of optimal control problems, the optimal endo-atmospheric ascent problem with path constraints and final condition constraints is transformed into a Hamiltonian two point boundary value problem (TPBVP). An advanced Gauss pseudo-spectral method is applied to change the Hamiltonian TPBVP into a system of nonlinear algebraic equations, which is solved by a modified Newton method. To guarantee the convergence of the solution, analytical initial guess technology and homotopy technology are also introduced. At last, simulation tests are made.
Findings
The hybrid approach for optimal endo-atmospheric ascent trajectory planning has both fast convergence rate and high solution precision. The simulation results indicate that not only the proposed method is feasible but also it is better than the indirect method, which is a most popular approach for solving the optimal endo-atmospheric ascent problem. Given the same degree of solution accuracy, the new method consumes quite less time on the CPU than that of the indirect method.
Practical implications
The new optimization approach has high level of both solution accuracy and efficiency. It can be used in rapid trajectory designing, on-line trajectory planning and closed-loop guidance of launch vehicles. Also, the proposed Gauss pseudo-spectral method in this paper is a new and efficient method for solving general TPBVPs.
Originality/value
The paper provides a new hybrid optimization method for rapid endo-atmospheric ascent trajectory planning of launch vehicles.
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Jinbo Wang, Naigang Cui and Changzhu Wei
This paper aims to develop a novel trajectory optimization algorithm which is capable of producing high accuracy optimal solution with superior computational efficiency for the…
Abstract
Purpose
This paper aims to develop a novel trajectory optimization algorithm which is capable of producing high accuracy optimal solution with superior computational efficiency for the hypersonic entry problem.
Design/methodology/approach
A two-stage trajectory optimization framework is constructed by combining a convex-optimization-based algorithm and the pseudospectral-nonlinear programming (NLP) method. With a warm-start strategy, the initial-guess-sensitive issue of the general NLP method is significantly alleviated, and an accurate optimal solution can be obtained rapidly. Specifically, a successive convexification algorithm is developed, and it serves as an initial trajectory generator in the first stage. This algorithm is initial-guess-insensitive and efficient. However, approximation error would be brought by the convexification procedure as the hypersonic entry problem is highly nonlinear. Then, the classic pseudospectral-NLP solver is adopted in the second stage to obtain an accurate solution. Provided with high-quality initial guesses, the NLP solver would converge efficiently.
Findings
Numerical experiments show that the overall computation time of the two-stage algorithm is much less than that of the single pseudospectral-NLP algorithm; meanwhile, the solution accuracy is satisfactory.
Practical implications
Due to its high computational efficiency and solution accuracy, the algorithm developed in this paper provides an option for rapid trajectory designing, and it has the potential to evolve into an online algorithm.
Originality/value
The paper provides a novel strategy for rapid hypersonic entry trajectory optimization applications.
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This study aims to assess the enduring lack of citizenship for rural migrants coming to cities to work, and the extent to which there has been any progress in altering their…
Abstract
Purpose
This study aims to assess the enduring lack of citizenship for rural migrants coming to cities to work, and the extent to which there has been any progress in altering their status in past decades.
Design/methodology/approach
This study uses a narrative approach, relying on documentary sources. It takes a chronological approach in evaluating signs of progress but mainly tells a story of long-term continuity in the treatment of outsiders – even though they are from their own country – by urban officials and citizens.
Findings
The main finding is that the management of rural migrants in China’s cities has not fundamentally improved in the 40-plus years since they were released from the communes and permitted to come to cities to work. This is despite various pronouncements of change, most of which mattered little, if at all, in the implementation.
Originality/value
This study applies the concept of “citizenship” to what has been done and, mostly not done, for migrants over the past decades.