Investigating the potential of using acoustic frequency on the degradation of linear alkylbenzen sulfonates from aqueous solution

The effectiveness of using acoustical (sonochemical) reactor for degradation of linear alkylbenzen sulfonate (LAS) from aqueous solution was investigated. LASs are anionic surfactants,found in relatively high amounts in domestic and industrial wastewaters. In this study,experiments on LAS solution were performed using methylene blue active substances (MBAS) method. The effectiveness of acoustical processor reactor for LAS degradation is evaluated with emphasis on the effect of treatment time and initial LAS concentration. Experiments were performed at initial concentrations of 0.2,0.5,0.8 and 1.0 mg/L,acoustic fre-quency of 130 kHz,applied power of 500 W and temperature of 18 °C～20 °C. At the conditions involved,LAS degradation was found to increase with increasing sonochemical time. In addition,as the concentration increased,the LAS degradation rate de-creased in the acoustical processor reactor.     

High school students’ difficulties in understanding osmosis

Preconceptions and misconceptions of 500 secondary students in years 9‐12 regarding osmosis were studied through the use of five different kinds of instruments: prior learning inventory, self‐report knowledge inventory, true/false test, definitions and clinical interviews. Some of the major findings were: (1) The most frequent explanation offered to osmosis is ‘a desire or drive towards equalizing concentrations’. (2) Hardly any student uses the concept ‘water concentration’. (3) Most students fail to realize that in dynamic equilibrium water molecules keep moving. (4) Students have special difficulty in understanding osmotic relations in plants. (5) Many students have difficulty in grasping solute‐solvent and concentration‐quantity relations. (6) Students often perform laboratory experiments without really understanding the underlying principles. Practical and theoretical implications are discussed.     

Situational and personal influence on attitude change following ethnic contact

The study undertook to examine the validity in Israel of several conclusions reached by investigators in the United States on the effect of intergroup contact on change in ethnic attitudes, as well as to extend contact research to topics which heretofore have received only scant attention. There were 100 subjects: 12-year-old Israeli girls of different ethnic background, participating in a summer camp. Results indicated that (1) as a result of contact, a positive change in attitude of the high status towards the low-status group occurred with regard to people and activities both related and not related to the contact situation, (2) only subjects without previous ethnic contact showed changes, (3) enjoyment of the contact situation was related to attitude change, while (4) authoritarianism was not related to attitude change.     

Threshold of Withdrawal from Schoolwork among Children of Divorced Parents

Abstract The principal aim of the present study was to examine whether there is a difference of withdrawal threshold between children of divorced parents and children from intact families as regards schoolwork. Three different school‐type tests, designed to be long and frustrating, were administered to two groups of children. One group consisted of 31 children of divorced parents (15 boys and 16 girls); the second consisted of children from intact families and was of equal size and had a matching number of children of both sexes. There were three dependent variables: level of achievement, level of determination and the time spent on the test. The main results show that children of divorced parents have lower levels of achievement and lower withdrawal thresholds than do children from intact families. These findings are presented in the context of a consideration both of the children's experience and interpretation of their parents’ divorce and of the generalisability of the concept of withdrawal threshold.     

Experiencing equivalence but organizing order

The notion of equivalence relation is arguably one of the most fundamental ideas of mathematics. Accordingly, it plays an important role in teaching mathematics at all levels, whether explicitly or implicitly. Our success in introducing this notion for its own sake or as a means to teach other mathematical concepts, however, depends largely on our own conceptions of it. This paper considers various conceptions of equivalence, in history, in mathematics today, and in mathematics education. It reveals critical differences in the notion of equivalence at different points in history and a meaning for equivalence proposed by mathematicians and mathematics educators that is at variance with the ways that learners may think. These differences call into question the most popular view of the subject: that the mathematical notion of equivalence relation is the result of spelling out our experience of equivalence. Moreover, the findings of this study suggest that the standard definition of an equivalence relation is ill-chosen from a pedagogical point of view but well-crafted from a mathematical point of view.     

An integrated group decision-making process for supplier selection and order allocation using multi-attribute utility theory and linear programming

Supplier selection is a complex multi-criteria problem including both quantitative and qualitative factors. In order to select the best suppliers it is necessary to make a trade-off between these factors, some of which may be in conflict and may also be uncertain. In this problem if suppliers have capacity or other different constraints, two problems will exist: which suppliers are best and how much should be purchased from each selected supplier.In this paper an integrated approach of multi-attribute utility theory (MAUT) and linear programming (LP) is proposed for rating and choosing the best suppliers and defining the optimum order quantities among selected ones in order to maximize total additive utility. A numerical example is proposed to illustrate an application of the proposed method.     

Robust simultaneous fault detection and control for a class of nonlinear stochastic switched delay systems under asynchronous switching

This paper concerns the simultaneous fault detection and control (SFDC) problem for a class of nonlinear stochastic switched systems with time-varying state delay and parameter uncertainties. The switching signal of detector/controller unit (DCU) is assumed to be with switching delay, which results in the asynchronous switching between the subsystems and DCU. By constructing a switching strategy depending on the state and switching delays, new sufficient conditions expressed by a set of linear matrix inequalities (LMIs) is derived to design DCU gains. This problem is formulated as an H_∞ optimization problem and both mean square exponential stability and fault detection of augmented system are considered. A numerical example is finally exploited to verify the effectiveness and potential of the achieved scheme.     

Finite-time fractional-order adaptive intelligent backstepping sliding mode control of uncertain fractional-order chaotic systems

This paper precedes chaos control of fractional-order chaotic systems in presence of uncertainty and external disturbances. Based on some basic properties on fractional calculus and the stability theorems, we present a hybrid adaptive intelligent backstepping-sliding mode controller (FAIBSMC) for the finite-time control of such systems. The FAIBSMC is proposed based on the concept of active control technique. The asymptotic stability of the controller is shown based on Lyapunov theorem and the finite time reaching to the sliding surfaces is also proved. Illustrative and comparative examples and simulation results are given to confirm the effectiveness of the proposed procedure, which consent well with the analytical results.     

Group status and attitude change in desegregated classrooms

One thousand thirty-three ninth-grade students from Western and Middle-Eastern ethnic background in 30 classrooms responded to a questionnaire assessing ethnic attitudes. The questionnaire was administered at the beginning and again at the end of these students' first year in ethnically desegregated classrooms. No marked changes in ethnic attitudes were noted as a function of the students' individual academic or social status in the classroom, but there were noteworthy changes associated with the relative status in the classroom occupied by the students' ethnic groups. Positive attitude change among Western (majority) students occurred when both ethnic groups in the classroom were of equal status, and when the MiddleEastern (minority) group was of superior academic status to the Western group. Positive change among the Middle-Eastern group occurred when it occupied superior status in the classroom.