A composite pseudospectral method for solving multi-delay optimal control problems involving piecewise constant delay functions     

Sayyed Mohammad Hoseini 《Journal of The Franklin Institute》2018,355(16):7895-7923

An adaptive numerical method for solving multi-delay optimal control problems with piecewise constant delay functions is introduced. The proposed method is based on composite pseudospectral method using the well-known Legendre–Gauss–Lobatto points. In this approach, the main problem converts to a mathematical optimization problem whose solution is much more easier than the original one. The necessary conditions of optimality associated to nonlinear piecewise constant delay systems are derived. The method is easy to implement and provides very accurate results.  相似文献   

Probabilistic fuzzy logic controller for uncertain nonlinear systems     

Omar Shaheen  Ahmad M. El-Nagar  Mohammad El-Bardini  Nabila M. El-Rabaie 《Journal of The Franklin Institute》2018,355(3):1088-1106

This paper proposes a probabilistic fuzzy proportional - integral (PFPI) controller for controlling uncertain nonlinear systems. Firstly, the probabilistic fuzzy logic system (PFLS) improves the capability of the ordinary fuzzy logic system (FLS) to overcome various uncertainties in the controlled dynamical systems by integrating the probability method into the fuzzy logic system. Moreover, the input/output relationship for the proposed PFPI controller is derived. The resulting structure is equivalent to nonlinear PI controller and the equivalent gains for the proposed PFPI controller are a nonlinear function of input variables. These gains are changed as the input variables changed. The sufficient conditions for the proposed PFPI controller, which achieve the bounded-input bounded-output (BIBO) stability are obtained based on the small gain theorem. Finally, the obtained results indicate that the PFPI controller is able to reduce the effect of the system uncertainties compared with the fuzzy PI (FPI) controller.  相似文献   

Nonlinear model-predictive control with disturbance rejection property using adaptive neural networks     

Bahareh Vatankhah  Mohammad Farrokhi 《Journal of The Franklin Institute》2017,354(13):5201-5220

In this paper, a method is proposed to reject disturbances in the model predictive control (MPC) strategy. In addition, uncertainties in the system parameters (i.e., internal disturbances) are considered as well. To achieve these goals, adaptive neural networks are designed as the predictor model and as the nonlinear disturbance observer, respectively. The disturbances are rejected via the optimization problem of the MPC. Stability of the closed-loop system is studied based on the Input-to-State Stability method. The proposed method is applied to the pH neutralization process and CSTR system and its effectiveness in optimal rejection of the disturbances and satisfying the system constrains is compared with the feed-forward control method.  相似文献   

The Shaffer–Gee perspective: Can epistemic games serve education?     

Mohammad Ali Salmani Nodoushan 《Teaching and Teacher Education》2009

This paper addresses the issue of how games can reshape education by describing current educational practices. It argues that there are conservative camps that emphasize structure and development of basic literacy and numeracy skills in education as well as liberal camps that emphasize immersion, and notices that both camps fail to train students able to address the crisis of innovation. A post-progressive pedagogy that integrates both structure and immersion to address this innovation crisis is described in the paper. It is also emphasized that epistemic games can serve as excellent tools at the hand of this post-progressive pedagogy.  相似文献   

Isolation and purification of rat islet cells by flow cytometry     

Azim Akbarzadeh  Dariush Norouzian  Ali Farhangi  Mohammad Reza Mehrabi  Shirin Jamshidi  Davood Zare  Morvarid Shafiei 《Indian journal of clinical biochemistry : IJCB》2008,23(1):57-61

Flow cytometry has been employed as a method to study homogeneity of isolated islet subpopulations. After collagenase digestion of rat pancreas and elutriation of tissue fragments, islets were isolated and dissociated, and cells were analyzed and sorted according to their low forward angle light scattering properties by using automated flow cytometry. A standardized procedure was developed for the preparation of rat islet cell grafts for purification of islet cells. In this process, after collagenase digestion of pancreas, islets were isolated, dissociated, identification by dithizone method and then with enzymatic procedure by DNase and trypsin, the islet cells changed into single cells and beta cells were identified by immunofluorescence method and then assayed by flow cytometry. Methods have been developed for the preparation of suspension of viable rat pancreatic islet cells and their analysis and sorting in the fluorescence activated cell sorter (FACC IV, Becton Dickinson, Sunnyvale, Ca). Flow cytometry of these cells indicated that there were 91% of beta cells in cell suspension. Most of the exocrine particles were lost during digestion. Purified endocrine islet cell grafts were prepared by pure beta-cells, without endocrine non-beta cells. The purified aggregates were devoid of endocrine non-beta cells and damaged cells.  相似文献   

Improving teacher prediction of children at risk for reading failure     

Jane M. Flynn  Mohammad Hossein Rahbar 《Psychology in the schools》1998,35(2):163-172

Whether screening tests or teacher ratings best predict children at risk for reading failure continues to be an area of disagreement in the early identification literature. Our early studies confirmed low positive identification rates (30%) when kindergarten teachers were asked to predict future reading achievement using a traditional rating scale, while a project-developed, theory-based screening battery correctly identified 81% of poor readers. Construction of a teacher rating scale of current skill levels on research-validated precursors to reading improved prediction in the current study, although results were still inferior to the screening test (64% and 80% valid positives, respectively). Combining test results and teacher ratings resulted in 88% identification of those who failed in first, second, or third grade, suggesting that both teacher ratings and screening tests should be used to identify the largest number of those who will later fail in reading. © 1998 John Wiley & Sons, Inc.  相似文献   

A commentary on “determining the level of inquiry in teachers' questions”     

Mohammad N. Siddiqi  Hans O. Anderson  George T. Ladd 《科学教学研究杂志》1973,10(2):179-181

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Chip morphology predictions while machining hardened tool steel using finite element and smoothed particles hydrodynamics methods     

Usama Umer  Jaber Abu Qudeiri  Mohammad Ashfaq  Abdulrahman AL-Ahmari 《浙江大学学报(A卷英文版)》2016,17(11):873-885

Chip morphology predictions in metal cutting have always been challenging because of the complexity of the various multiphysical phenomena that occur across the tool-chip interface. An accurate prediction of chip morphology is a key factor in the assessment of a particular machining operation with regard to both tool performance and workpiece quality. Although finite element (FE) models are being developed over the last two decades, their capabilities in modeling correct material flow around the tool tip with shear localization are very limited. FE models with an arbitrary Lagrangian Eulerian (ALE) approach are able to simulate correct material flow around the tool tip. However, these models are unable to predict any shear localization based on material flow criteria. On the other hand, FE models with a Lagrangian formulation can simulate shear localization in the chip segments; they need to make use of a mesh-based chip separation criterion that significantly affects material flow around the tool tip. In this study a mesh-free method viz. smoothed particles hydrodynamics (SPH) is implemented to simulate shear localization in the chip while machining hardened steel. Unlike other SPH models developed by some researchers, this model is based on a renormalized formulation that can consider frictional stresses along the tool-chip interface giving a realistic chip shape and material flow. SPH models with different cutting parameters are compared with the traditional FE models and it has been found that the SPH models are good for predicting shear localized chips and do not need any geometric or mesh-based chip separation criteria.  相似文献   

A comparative study of conventional and supercritical fluid extraction methods for the recovery of secondary metabolites from <Emphasis Type="Italic">Syzygium campanulatum</Emphasis> Korth     

Abdul Hakeem Memon  Mohammad Shahrul Ridzuan Hamil  Madeeha Laghari  Fahim Rithwan  Salman Zhari  Mohammed Ali Ahmed Saeed  Zhari Ismail  Amin Malik Shah Abdul Majid 《Journal of Zhejiang University. Science. B》2016,17(9):683-691

Syzygium campanulatum Korth is a plant, which is a rich source of secondary metabolites (especially flavanones, chalcone, and triterpenoids). In our present study, three conventional solvent extraction (CSE) techniques and supercritical fluid extraction (SFE) techniques were performed to achieve a maximum recovery of two flavanones, chalcone, and two triterpenoids from S. campanulatum leaves. Furthermore, a Box-Behnken design was constructed for the SFE technique using pressure, temperature, and particle size as independent variables, and yields of crude extract, individual and total secondary metabolites as the dependent variables. In the CSE procedure, twenty extracts were produced using ten different solvents and three techniques (maceration, soxhletion, and reflux). An enriched extract of five secondary metabolites was collected using n-hexane:methanol (1:1) soxhletion. Using food-grade ethanol as a modifier, the SFE methods produced a higher recovery (25.5%?84.9%) of selected secondary metabolites as compared to the CSE techniques (0.92%?66.00%).  相似文献   

Phytoremediation of heavy metal polluted soils and water：Progresses and perspectives   总被引：4，自引：0，他引：4  

Lone MI  He ZL  Stoffella PJ  Yang XE 《Journal of Zhejiang University. Science. B》2008,9(3):210-220

Environmental pollution affects the quality of pedosphere, hydrosphere, atmosphere, lithosphere and biosphere. Great efforts have been made in the last two decades to reduce pollution sources and remedy the polluted soil and water resources. Phytoremediation, being more cost-effective and fewer side effects than physical and chemical approaches, has gained increasing popularity in both academic and practical circles. More than 400 plant species have been identified to have potential for soil and water remediation. Among them, Thlaspi, Brassica, Sedum alfredii H., and Arabidopsis species have been mostly studied. It is also expected that recent advances in biotechnology will play a promising role in the development of new hyperaccumulators by transferring metal hyperaccumulating genes from low biomass wild species to the higher biomass producing cultivated species in the times to come. This paper attempted to provide a brief review on recent progresses in research and practical applications of phytoremediation for soil and water resources. Project supported by the Higher Education Commission, Government of Pakistan for the faculty training under the R & D Project “Strengthening Department of Soil Science and Soil and Water Conservation” at the University of Florida, USA, a grant from the St. Lucie River Water Initiative (SFWMD contract No. OT060162), USA, in part, and the Program for Changjiang Scholars and Innovative Research Team in University (No.IRT0536), China  相似文献