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Jing Sun - One of the best experts on this subject based on the ideXlab platform.
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A Modified Model reference adaptive control scheme for improved transient performance
IEEE Transactions on Automatic Control, 1993Co-Authors: Jing SunAbstract:The author proposes a Modified Model reference adaptive control (MRAC) scheme aimed at improving the transient performance of adaptive systems while maintaining the ideal asymptotic properties possessed by standard MRAC. In the Modified scheme, the estimation error, which is generated by the identification scheme, is used directly as a control signal to counteract errors resulting from the certainty equivalence design. It is shown that the Modified scheme provides essentially the same stability and robustness properties as the standard adaptive MRAC approach but with the transient performance substantially improved. Simulation results are presented to illustrate the effectiveness of the proposed scheme. >
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A Modified Model Reference Adaptive Control Scheme for Improved Transient Performance
1991 American Control Conference, 1991Co-Authors: Jing SunAbstract:We propose a Modified Model reference adaptive control scheme aimed at improving the transient performance of adaptive systems while maintaining ideal asymptotic properties possessed by a standard Model reference adaptive control. In the new scheme, the estimation error, which is generated by the identification scheme, is used directly as a control signal to counteract errors resulting from the certainty equivalence design. We show that the Modified scheme has essentially the same stability and robustness properties of a standard adaptive MRAC system but with the transient performance substantially improved. Simulation results have also been presented to illustrate the effectiveness of the proposed scheme.
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Modified Model reference adaptive control with saturated inputs
[1992] Proceedings of the 31st IEEE Conference on Decision and Control, 1Co-Authors: Hong Wang, Jing SunAbstract:Two Modified Model reference adaptive control schemes for the system with input saturation are presented. The properties of the proposed algorithms are studied, and the stability analysis for one of the algorithms is given for type-l systems. The performance improvement of these algorithms is verified by simulation results. >
Guojie Zhang - One of the best experts on this subject based on the ideXlab platform.
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performance evaluation and operation optimization of the steam ejector based on Modified Model
Applied Thermal Engineering, 2019Co-Authors: Guojie Zhang, Xinzhe Zhang, Dingbiao WangAbstract:Abstract Steam ejectors are widely applied in various industries, as they have the ability to improve the low-grade energy. In this work, a Modified Model is proposed and employed to evaluate steam ejector performance and to optimize steam ejector operation. Firstly, the Modified nucleation Model is built. Four Models consisting of different nucleation Models and droplet growth Models are adopted to predict the non-equilibrium condensation. The results show that the Model consisting of the Modified nucleation Model and Young′s droplet growth Model ( ϕ = 0.75 , α = 9 ) presents the best ability to predict pressure distribution and the Wilson point than the other three Models. Secondly, a steam ejector is investigated using the Modified Model and the ideal gas Model, the results show that the Modified Model is more suitable to predict the steam ejector wall pressure distribution than the ideal gas Model, and the steam ejector performance predicted by the Modified shows less error than that predicted by the ideal gas, compared with that obtained by the experiment. The relative error of critical condenser pressure reduces from 4.4% to 1.5%. At last, the steam ejector operation is optimized based on the Modified Model, and the results is analyzed in sufficient detail.
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the relationship between the nucleation process and boundary conditions on non equilibrium condensing flow based on the Modified Model
International Journal of Multiphase Flow, 2019Co-Authors: Guojie Zhang, Xinzhe Zhang, Dingbiao Wang, Fangfang Wang, Zunlong JinAbstract:Abstract The aim of this work is to investigate the relationship between the nucleation process and boundary conditions on non-equilibrium condensing flow based on the Modified Model. Firstly, a Modified Model is developed to predict the non-equilibrium condensation flow. The Modified Model is validated in a nozzle and stator cascade, which shows a greater agreement with the experimental data compared with original Model. Secondly, the influence of inlet steam superheat degree on the nucleation process is investigated. The results show that: 1. The inlet steam superheat degree just plays an important role in the nucleation zone and the location of nucleation beginning. 2. The steam superheat degree has no effect on the minimum supercooling degree required for nucleation, which is about 17 K. It should be related to the property of vapor. Thirdly, the influence of the steam expansion rate on the nucleation process is studied. The results show that with the increment of the vapor expansion rate, the pressure rise becomes obvious, but no matter how the vapor expansion rate change, the minimum supercooling degree required for nucleation keeps constant, which is about 17 K. At last, the non-equilibrium condensation flow is investigated numerically in three-dimensional cascade. The results show that with the span increasing, the expansion rate gradually decreases and the nucleation rate decreases but the nucleation zone increases. Besides, the liquid mass fraction reduces with the span increasing.
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Numerical study of the dehumidification structure optimization based on the Modified Model
Energy Conversion and Management, 2019Co-Authors: Guojie Zhang, Dingbiao Wang, Fangfang Wang, Xiang Qin, Zunlong JinAbstract:Abstract Nowadays, the vast majority of electricity is extracted from the steam turbine, while the non-equilibrium condensation will take place because of the high steam velocity and low superheat temperature in steam low-pressure stage, which will not only reduce the efficiency but endanger the safety of the steam turbine by corroding the blade. The aim of this work is to optimize the novel dehumidification structure to reduce the wetness loss and increase the efficiency of steam turbine. Firstly, the Modified Model is developed to predict the non-equilibrium condensation flow. The Modified Model is validated in stator cascade, which shows a greater agreement with the experimental data compared with original Model, especially the Wilson point and pressure rise caused by the non-equilibrium condensation. Secondly, two novel dehumidification structures are presented on the basis of my previous study, and the dehumidification effect is checked using the Modified Model. With the passage outlet diameter increasing in the PICS, the reduction of the outlet average liquid mass fraction and wetness loss in cascade has the same tendency, and the more the passage outlet diameter, the lower the outlet average liquid mass fraction, the less the wetness loss caused by the non-equilibrium condensation in cascade. Thirdly, compared with the original cascade, the PICS with the φ = 5 ° having the divergence nozzle characteristic and larger outlet diameter presents the best dehumidification effect and succeeds in reducing the average liquid mass fraction and wetness loss to 3% and 3.06 kJ/kg, respectively.
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Effect evaluation of a novel dehumidification structure based on the Modified Model
Energy Conversion and Management, 2018Co-Authors: Guojie Zhang, Sen Zhang, Liang Wang, Zhongning ZhouAbstract:Abstract In the course of energy conversion, steam turbine is one of the most important equipment, but the wet steam at the low-pressure stage will cause losses. The losses caused by condensing flow not only reduce the efficiency of steam turbine but also influence reliability. This paper firstly numerically investigated the Dykas cascade using the Modified Model, and compared with the experimental data. The results showed that the Modified Model had an enormous advantage in predicting the condensing flow. Besides, the advantage was obvious in calculating the pressure distribution of the blade and shock angle emerged in the blade trailing edge. Secondly, a novel dehumidification structure was proposed and the effect was calculated and discussed. The result showed that the novel structure had a positive effect on reducing the nucleation zone and the liquid mass fraction. Besides, the influence of different passage diameters was investigated, the conclusion can be drawn: both the liquid mass fraction of the outlet and the nucleation zone decrease with the increment of the passage diameter. Finally, an improved dehumidification structure which can be easily manufactured was presented and the structure with different φ was calculated. The results showed that when φ = 0 , the dehumidification efficiency was remarkable, and the structure can be easily manufactured. However, the decrement of the liquid mass fraction was inconspicuous with the further increment of φ .
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Numerical study of condensing flow based on the Modified Model
Applied Thermal Engineering, 2017Co-Authors: Guojie Zhang, Sen Zhang, Zhongning Zhou, Liang Wang, Liu CongAbstract:Abstract Condensation phenomenon is very common, whether in the steam turbine or refrigeration cycle. This paper firstly numerically studies the Moses and Stein nozzle focusing on condensing flow. Both the Modified Model and the original Model are calculated, besides the results are compared with experimental data to verify the correctness of the numerical simulation based on the error analysis. The results show that the Modified Model is more accurate than the original Model in predicting the Wilson point position and its thermal parameters. Additionally, the pressure will rise due to the release of latent heat in the condensation process, and the nucleation will only occur when the vapor supercooling reaches a certain level, about 18 K. The nucleation rate will reach its maximum when the vapor supercooling reaches maximum, which is defined as Wilson point. In two-dimensional Dykas cascade, the Modified Model can more accurately predicted the blade surface pressure distribution and flow field characteristic than the original Model. Finally, the Modified Model is applied in three-dimensional steam turbine cascade, and the parameters of flow passage centerline along the spanwise direction are investigated in detail.
Ghorbaniayaz - One of the best experts on this subject based on the ideXlab platform.
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A Modified Model and linearization method for solid state power amplifier
Analog Integrated Circuits and Signal Processing, 2007Co-Authors: Aghasiali Reza, Karkhanehhaleh, GhorbaniayazAbstract:In this paper we present a Modified Model of solid state power amplifiers. Also using the mathematical concept of best approximation in Hilbert spaces, a predistorter structure is suggested to comp...
Ayaz Ghorbani - One of the best experts on this subject based on the ideXlab platform.
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A Modified Model and linearization method for solid state power amplifier
Analog Integrated Circuits and Signal Processing, 2007Co-Authors: Alireza Aghasi, Haleh Karkhaneh, Ayaz GhorbaniAbstract:In this paper we present a Modified Model of solid state power amplifiers. Also using the mathematical concept of best approximation in Hilbert spaces, a predistorter structure is suggested to compensate both AM/AM and AM/PM conversion characteristics of a solid state power amplifier. To verify the effects of this linearization we generally consider it in a QAM signal transmission in an additive white Gaussian noise channel and the results are compared with the ideal linear case. It is shown that the presented method is able to compensate the nonlinearity up to a good extent. The performance of proposed method has been analyzed in frequency domain through spectrum simulations. To prove the validity of presented method we have made similar considerations on continuous spectrum.
Alexander V. Efimov - One of the best experts on this subject based on the ideXlab platform.
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Modified Model of potato virus X coat protein structure
Molekuliarnaia biologiia, 2007Co-Authors: E. N. Dobrov, M. A. Nemykh, E. V. Lukashina, Ludmila A. Baratova, V. A. Drachev, Alexander V. EfimovAbstract:We propose the Modified Model of the structure of coat protein (CP) subunits in filamentous virions of potato virus X (PVX). The Model is similar to the one proposed by us in 2001 for the CP of another helical plant virus (potato virus A) belonging to other (potyvirus) group. In this Model the PVX CP molecule consist of two main domains--a bundle of four alpha-helices located close to the virion long axis and a so-called RNP-fold (or abCd-fold) located near the virion surface. Basing on this Model we suggest possible mechanism of described by J.G. Atabekov and colleagues structural transition ("reModeling") of the PVX virions resulting from their interaction with virus-specific TGB-1 protein.
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Modified Model of the structure of the potato virus X coat protein
Molecular Biology, 2007Co-Authors: E. N. Dobrov, M. A. Nemykh, E. V. Lukashina, Ludmila A. Baratova, V. A. Drachev, Alexander V. EfimovAbstract:A Modified Model was proposed for the tertiary structure of the coat protein (CP) molecules in potato virus X (PVX) virions, similar to the original Model of 2001 describing the structure of CP of potato virus A, a member of another group of filamentous viruses. According to the new Model, CP comprises two main structural domains, namely, a bundle of α-helices, located near the long axis of the virion, and the socalled RNP fold (or abCd fold), located in the vicinity of its surface. The Model made it possible to suggest a possible mechanism of the PVX virion structural rearrangement (reModeling) resulting from translational activation of virions by the TGB1 movement protein according to Atabekov and colleagues.
