Secondary School Students’ Reasoning About Science and Personhood

Science & Education - Scientific advances, particularly in evolutionary biology, genetics, neuroscience and artificial intelligence, present many challenges to religious and popular notions of...     

Targeted cell detection based on microchannel gating

Currently, microbiological techniques such as culture enrichment and various plating techniques are used for detection of pathogens. These expensive and time consuming methods can take several days. Described below is the design, fabrication, and testing of a rapid and inexpensive sensor, involving the use of microelectrodes in a microchannel, which can be used to detect single bacterial cells electrically (label-free format) in real time. As a proof of principle, we have successfully demonstrated real-time detection of target yeast cells by measuring instantaneous changes in ionic impedance. We have also demonstrated the selectivity of our sensors in responding to target cells while remaining irresponsive to nontarget cells. Using this technique, it can be possible to multiplex an array of these sensors onto a chip and probe a complex mixture for various types of bacterial cells.     

On optimal form of arches

This paper considers the problem of optimal shaping of arches subjected to general loading. The investigation comprises the search for the optimum centerline form as well as the optimum area distribution along the arch. As objective function and constraints, the appropriate combinations of arch thrust, material volume, total arc length, and enclosed area are considered.     

Fault tolerant cooperative control for affine multi-agent systems: An optimal control approach

The goal of this paper is to propose an optimal fault tolerant control (FTC) approach for multi-agent systems (MASs). It is assumed that the agents have identical affine dynamics. The underlying communication topology is assumed to be a directed graph. The concepts of both inverse optimality and partial stability are further employed for designing the control law fully developed in the paper. Firstly, the optimal FTC problem for linear MASs is formulated and then it is extended to MASs with affine nonlinear dynamics. To solve the Hamilton-Jacobi-Bellman (HJB) equation, an Off-policy Reinforcement Learning is used to learn the optimal control law for each agent. Finally, a couple of numerical examples are provided to demonstrate the effectiveness of the proposed scheme.     

Optimal trajectory tracking solution: Fractional order viewpoint

In this paper, a generalized trajectory tracking problem for a closed-loop control system is formulated in the optimal control context. A linear time varying plant is considered to track a closed-loop desired trajectory generated by a given mechanism. The theoretical results are obtained based on the Hamilton-Jacobi-Bellman theory in which some generalized semiquadratic value functions are employed as the Lagrangian. In addition, we employ a non-integer order integral of Riemann-Liouville type as the cost functional, so that the trajectory tracking process can be evaluated in an extended optimum manner wherein the fractionality plays the main role. By selecting a suitable fractional order of the integral, a satisfactory optimal control system can be deduced in which least concentration on selecting the weighting matrices is needed. To show the effectiveness of the results, some numerical examples illustrate the potentials.     

Robust finite-time stabilizers for five-degree-of-freedom active magnetic bearing system

In this paper, the robust finite-time stabilization problem for a fully suspended five-degree-of-freedom active magnetic bearing system is addressed in the presence of external disturbances and additive uncertainties. By developing the nonsingular terminal sliding mode control and defining new nonlinear sliding surfaces, three separate classes of stabilizers are proposed to regulate and place the suspended rotor in the desired positions of air gaps within adjustable finite times. The suggested nonlinear sliding surfaces and designed control inputs for each class of stabilizers are two major differences between these stabilizers. It is mathematically proven that five control voltages of this system, designed by each class of the suggested stabilizers, are able to locate the suspended rotor at the centers of air gaps in the adjustable finite time which is summation of two reaching and settling finite times. Moreover, several new inequalities are extracted for determining the reaching and settling finite times related to the three classes of stabilizers. These inequalities reveal the dependencies between optional parameters of the proposed stabilizers and the mentioned finite times. Finally, numerical simulations are provided to illustrate the efficiency and good performance of each class of the designed stabilizers.     

Science Letters: Low-cost fault tolerance in evolvable multiprocessor systems: a graceful degradation approach

The evolvable multiprocessor (EvoMP), as a novel multiprocessor system-on-chip (MPSoC) machine with evolvable task decomposition and scheduling, claims a major feature of low-cost and efficient fault tolerance. Non-centralized control and adaptive distribution of the program among the available processors are two major capabilities of this platform, which remarkably help to achieve an efficient fault tolerance scheme. This letter presents the operational as well as architectural details of this fault tolerance scheme. In this method, when a processor becomes faulty, it will be eliminated of contribution in program execution in remaining run-time. This method also utilizes dynamic rescheduling capability of the system to achieve the maximum possible efficiency after processor reduction. The results confirm the efficiency and remarkable advantages of the proposed approach over common redundancy based techniques in similar systems.     

Unfulfilled promise: radical discourses in South African educational historiography, 1970–2007

This paper examines the discourses and modes of representation embodied in educational historiography from the 1970s to the present and their implications for intellectual identity construction in SA. The paper shows how the theoretical foundations of the liberal and Afrikaner nationalist discourses, which vacillated between race and ethnicity, shifted to social class and gender in radical and neo‐Marxist discursive formations of the 1980s. It highlights how the decline of radical scholarship has resulted in a synthesis of constructivist and postmodernist discourses that privilege nation‐building, identity and cultural diversity after apartheid within a predominantly neo‐liberal paradigm. It argues that the transition to post‐apartheid education came to be thought about within a horizon of possibilities different from the rigid paradigmatic tradition of the short‐lived neo‐Marxist school of the 1970s and 1980s.     

Stresses in sheets with backing

A mathematical model of surface layers such as tilings, plasters and coatings is established in this paper. To solve the field equations analytically, use is made of a pertubation scheme which yields the influence of the “backing” on the elastic behavior of “the sheet”. As an application, an illustrative example is worked out and the results are discussed.     

A culturally-adaptive Iranian version of the Questionnaire on Teacher Interaction to investigate English teachers’ interpersonal behaviour

We investigated Iranian secondary-school English teachers’ interpersonal behaviour with a validated culturally-adaptive Iranian version of the Questionnaire on Teacher Interaction. Data were collected from 971 Iranian secondary-school students (398 students participated in the pilot study and 573 students in the main study) and 55 Iranian secondary-school English teachers (23 teachers participated in the pilot study and 32 in the main study). The construction of the instrument started with an open-ended questionnaire followed by semi-structured interviews to prepare items for the questionnaire. Next, expert judgement, pilot administration of the questionnaire and statistical analyses ensured its reliability and construct validity before final administration of the questionnaire to the main participants followed. The study supported the validity and reliability of the questionnaire and confirmed its usability in the Iranian secondary-school context. Furthermore, the results indicated that the students perceived their English teachers as being Tolerant and Authoritative, showing higher degrees of friendship, leadership and understanding behaviour and relatively low levels of uncertain and dissatisfied behaviour. The results showed a discrepancy between students’ perceptions of actual and ideal teacher interpersonal behaviour. Also students’ perceptions of their actual teachers’ interpersonal behaviour were significantly different from those of the teachers’ self-perceptions. One important implication of this study is that the QTI can be used in secondary-school contexts as a valuable feedback instrument to encourage teachers to reflect on their performance and improve their interpersonal behaviour as a part of their professional development.