Cascade design for formation control of nonholonomic systems in chained form     

Jawhar Ghommam  Hasan Mehrjerdi  Maarouf Saad 《Journal of The Franklin Institute》2011,348(6):973-998

This paper presents a constructive method to design a cooperative state and output feedback to steer a group of nonholonomic mobile robots in chained form to form a desired geometric formation shape. The control methodology divides the resulting tracking error dynamics into a cascaded of linear and time-varying subsystems. A basic consensus algorithm is first applied to the linear subsystem which makes the states synchronize exponentially to zero. Once this first linear subsystem has converged, the second cascade can be treated as a linear time-varying subsystem perturbed by a vanishing term from its cascade. A dynamic state and output feedback is constructed to achieve synchronization of the rest of the states. The proof of stability is given using a result from cascade systems. Since time delay appears in many interconnection networks and particularly in cooperative control, its effect on the stability of the closed-loop system is analyzed using Razumikhim theorem. It is shown that the established cooperative controller work well even in the presence of time delay. Numerical simulations are performed on models of car-like mobile robots to show the effectiveness of the proposed cooperative state and output-feedback controllers.  相似文献   

Stable model predictive control for a nonlinear system     

Akbar Rahideh  M. Hasan Shaheed 《Journal of The Franklin Institute》2011,348(8):1983-2004

In this paper, a stable model predictive control approach is proposed for constrained highly nonlinear systems. The technique is a modification of the multistep Newton-type control strategy, which was introduced by Li and Biegler. The proposed control technique is applied on a constrained highly nonlinear aerodynamic test bed, the twin rotor MIMO system (TRMS) to show the efficacy of the control technique. Since the accuracy of the plant model is vital in MPC techniques, the nonlinear state space equations of the system are derived considering all possible effective components. The nonlinear model is adaptively linearized during the prediction horizon. The linearized models of the system are employed to form a linear quadratic objective function subject to a set of inequality constraints due to the system input/output limits. The stability of the control system is guaranteed using the terminal equality constraints technique. The satisfactory performance of the proposed control algorithm on the TRMS validates the effectiveness and the reliability of the approach.  相似文献   

Wellbeing and Policy     

Hasan Bakhshi 《Cultural Trends》2014,23(4):304-307

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Authorship conflict in Bangladesh: an exploratory study     

Hasan Shareef AHMED  Abdullahel HADI  Nuzhat CHOUDHURY 《Learned Publishing》2010,23(4):319-325

This study aimed to explore the causes, types, and consequences of authorship conflicts among the researchers of selected research institutions in Dhaka, Bangladesh; and to suggest ways to reduce conflicts. A sample of 100 researchers was given a semi‐structured questionnaire; 45 subjects responded. The responses were confidential and anonymous. Over two‐thirds of the respondents were aware of authorship conflicts, and one‐third had actually faced conflicts with their co‐authors. Of them, four faced conflicts with their juniors, while 13 faced conflicts with their seniors or supervisors. The primary causes of such conflicts appear to be unethical claims of authorship, violation of authorship order, and deprivation of authorship. In most cases, the victims became frustrated and had to give up, and avoided a direct clash to safeguard their job. Four respondents claimed to have been victimized for raising their voice. Conflict was never resolved in seven cases. To reduce conflicts, respondents suggested that authorship should be decided before the study begins, order of authorship must be determined according to contribution, and a standard code of authorship should be followed strictly. Authorship conflicts arise among researchers mostly due to what they regard as unethical practice of their co‐authors, supervisors, and department heads in the absence of any formal authorship policy in the institutions. A standard code of authorship, sensitization of researchers to the problem through open discussions and advocacy, and formation of a grievance redress committee are suggested to minimize such conflicts. Although the sample size was small, some of the specific recommendations will be appropriate in many other cases.  相似文献   

Using Hands-On and Virtual Laboratories Alone or Together―Which Works Better for Acquiring Knowledge and Skills?     

Kapici  Hasan Ozgur  Akcay  Hakan  de Jong  Ton 《Journal of Science Education and Technology》2019,28(3):231-250

Journal of Science Education and Technology - Although hands-on laboratory experiments are traditionally used in schools, virtual laboratories have entered today’s classrooms, due to their...  相似文献   

Searching for Components of Conceptual Ecology That Mediate Development of Epistemological Beliefs in Science     

Hasan Deniz 《Journal of Science Education and Technology》2011,20(6):743-749

This paper articulates the importance of epistemological beliefs (EBs) and draws a parallel between EBs literature in educational psychology and nature of science (NOS) literature in science education. The paper stresses that EBs in science and NOS ideas have common ground and they can be best improved through explicit-reflective instruction informed by conceptual change theory. The paper concludes that future studies should explore the factors that mediate the development of EBs in science and NOS ideas rather than documenting the changes in students’ and teachers’ EBs in science and NOS ideas after explicit-reflective instruction through pre- and post assessments.  相似文献   

Effectiveness of Computer-Based Chemistry Instruction in Enhancing the Learning of Content and Variable Control Under Guided Versus Unguided Conditions     

Ardac  Dilek  Sezen  Ali Hasan 《Journal of Science Education and Technology》2002,11(1):39-48

Computerized learning environments offer several possibilities that can be used to improve the teaching of content along with the process. Research indicates that students benefit from additional guidance, particularly when computer-based instruction requires active construction of knowledge. This study examines the relative effectiveness of guided versus unguided computer-based instruction with respect to regular instruction in improving content knowledge and process skills among students with low and high chemistry achievement levels. The results indicate that the effectiveness of computer-based instruction increases when learning is supported by teacher-directed guidance. Computer-based instruction (with or without guidance) was observed to be more effective than regular instruction in improving process skills particularly for students with high chemistry achievement. However, although the students who received regular or guided computer-based instruction showed significant gains in content knowledge, students under unguided condition failed to construct the expected content knowledge.  相似文献   

Differentiated Function of School in Socio-Culturally Disadvantaged Context: A Constructivist Grounded Theory Study from Turkey     

Zuhal Zeybekoglu Caliskan  Hasan Simsek  Yasar Kondakci 《The Urban Review》2017,49(3):400-419

This study analyses the functioning of a school as a social system in an atypical context with the purpose of generating propositions to tackle educational problems confronted by socially and economically disadvantaged groups attending these schools. Adopting the constructivist grounded theory, the analysis suggests that there is a kind of “vicious cycle” in the functioning of this atypical school, which adversely affects the school system. Breaking the vicious cycle involves five basic propositions: (1) making school a better place than students’ homes, (2) overcoming the enduring difficulties of working in an atypical school, (3) multiplying learning opportunities, (4) prompting parents to assume more responsibility, (5) locating leadership that makes a difference. These propositions clarify the significance of informal subsystems, school community and the wider environment along with their enabling and blocking effects on a disadvantaged school system. Parallel to other studies on disadvantaged schools, the study highlights the need to refine the orthodox view of the concept of formal education and school, as well as the role of school principal, teachers and parents affiliated with atypical schools.  相似文献   

Improved protocol for plasma microRNA extraction and comparison of commercial kits     

Harshini Sriram  Twinkle Khanka  Shweta Kedia  Priyanka Tyagi  Sitaram Ghogale  Nilesh Deshpande  Gaurav Chatterjee  Sweta Rajpal  Nikhil V Patkar  Papagudi G Subramanian  Sumeet Gujral  Syed Hasan  Prashant R Tembhare 《Biochemia medica : ?asopis Hrvatskoga dru?tva medicinskih biokemi?ara / HDMB》2021,31(3)

IntroductionMicroRNAs are small, non-coding RNA molecules that are becoming popular biomarkers in several diseases. However, their low abundance in serum/plasma poses a challenge in exploiting their potential in clinics. Several commercial kits are available for rapid isolation of microRNA from plasma. However, reports guiding the selection of appropriate kits to study downstream assays are scarce. Hence, we compared four commercial kits to evaluate microRNA-extraction from plasma and provided a modified protocol that further improved the superior kit’s performance.Materials and methodsWe compared four kits (miRNeasy Serum/Plasma, miRNeasy Mini Kit from Qiagen; RNA-isolation, and Absolutely-RNA MicroRNA Kit from Agilent technologies) for quality and quantity of microRNA isolated, extraction efficiency, and cost-effectiveness. Bioanalyzer-based Agilent Small RNA kit was used to evaluate quality and quantity of microRNA. Extraction efficiency was evaluated by detection of four endogenous control microRNA using real-time-PCR. Further, we modified the manufacturer’s protocol for miRNeasy Serum/Plasma kit to improve yield.ResultsmiRNeasy Serum/Plasma kit outperformed the other three kits in microRNA-quality (P < 0.005) and yielded maximum microRNA-quantity. Recovery of endogenous control microRNA i.e. hsa-miR-24-3p, hsa-miR-191-5p, hsa-miR-423-5p and hsa-miR-484 was higher as well. Modification with the inclusion of a double elution step enhanced yield of microRNA extracted with miRNeasy Serum/Plasma kit significantly (P < 0.001).ConclusionWe demonstrated that miRNeasy Serum/Plasma kit outperforms other kits and can be reliably used with a limited plasma quantity. We have provided a modified microRNA-extraction protocol with improved microRNA output for downstream analyses.  相似文献   

Anomaly-based change in higher education: The case of a large, Turkish public university     

Hasan Simsek  Dilkan Aytemiz 《Higher Education》1998,36(2):155-179

This paper analyzes an institutional change in a large, Turkish public university, the Middle East Technical University (METU), by using an anomaly-based change model. The model explains change as an organizational response to anomalies caused by internal and external organizational conditions. The study used a qualitative case study design that included interviews with 51 individuals, and, analysis of institution-specific documents. Anomalies derived from the interview findings compared with a separate set of anomalies, devised from the document study, that are attributed to the strategic change agenda developed by the current president of the institution. The paper argues that human thinking and problem solving as well as organizational cognition and problem solving do proceed through existence and recognition of a problematic situation. So, anomalies are the ID cards of any major change in organizations in that they carry important information about where the organization comes from and where it should proceed to. Implications for the nature and management of change in higher education organizations are discussed.  相似文献