Improved closed loop identification of transfer function model for unstable systems

The method of identifying first order plus time delay transfer function model proposed for unstable systems by Ananth and Chidambaram [Closed loop identification to transfer function model for unstable systems, J. Franklin Inst. 336 (1999) 1055-1061] is modified to avoid the stability problems [Cheres, Parameter estimation of an unstable system with a PID controller in a closed loop configuration, J. Franklin Inst., 2005, accepted for publication] of the method. Two modifications are proposed. In the first modification of the method, the under-determined algebraic equations problem is converted into an optimization problem for calculation of the three parameters of the first order plus time delay (FOPTD) model. A simple method is given for the initial guess values of the model parameters. In the second approach, from the definition of Laplace transform of the output response, a third equation is formulated. The resulted three equations, in terms of the three parameters of the transfer function model, are then numerically solved. Simulation results are given for the second order plus time delay transfer function considered by Cheres 2005 [Parameter estimation of an unstable system with a PID controller in a closed loop configuration, J. Franklin Inst., 2005, accepted for publication]. The responses of the identified models with the same PID controllers are compared with that of the actual system. PID controllers are designed based on the identified models. The closed loop responses of the controllers on the original system are evaluated and compared. The present methods give better control performances.     

Urinary enzymes in nephrotic syndrome

Tubular damage is a complication associated with nephrotic syndrome and increased levels of urinary enzymes are of significant value in detection of the same. The aim of our study was to evaluate the use of urinary lysozyme and trehalase as markers of tubular dysfunction in nephrotic syndrome. This study assessed 35 nephrotic syndrome patients and 30 healthy controls matched for age and sex. Urine samples were examined at pretreatment and post treatment (8 weeks) stages for proteinuria, lysozyme and trehalase. At pretreatmant stage there was significant increase in urinary lysozyme and trehalase as compared to controls (p<0.001). A good correlation was observed between degree of proteinuria and urinary lysozyme (p<0.001;r=0.80) and trehalase (p<0.001; r=0.74). At the end of 8 weeks of treatment, the patients showed significant decrease in their urinary lysozyme and trehalase activity (p<0.001) but no correlation with degree of proteinuria was observed. Our results indicate that enzymes like lysozyme and trehalase can be used as markers of tubular dysfunction.     

Comparison of Urinary Total Proteins by Four Different Methods

The total proteins in human urine have been compared by sulfosalicylic acid, sulfosalicylic acid with sodium sulphate and trichloroacetic acid methods with pyrogallol red molybdate method as there are no studies found quantifying imprecision and bias components. Fresh urine of 36 patients was analyzed by four methods. Imprecision and inaccuracy were determined by repeated analysis and method comparison studies using correlation plots, Bland and Altman, and Passing and Bablok regression analyses respectively. The coefficient of variation was 5.07 % for pyrogallol red molybdate; 6.84 % for sulfosalicylic acid; 3.97 % for sulfosalicylic acid with sodium sulphate and 5.93 % for trichloroacetic acid methods. Bland and Altman analysis showed a bias of 5.8, 1.7 and ?5.4 for pyrogallol red molybdate versus sulfosalicylic acid, sulfosalicylic acid with sodium sulphate and trichloroacetic acid methods respectively. Passing and Bablok regression revealed a constant bias for pyrogallol red molybdate versus all turbidimetric methods but a proportional bias only with trichloroacetic acid method. Sulfosalicylic acid with sodium sulphate method is preferred to sulfosalicylic acid and trichloroacetic acid methods.     

Tooley,Dixon and Gomathi on private education in Hyderabad: a reply

Tooley, Dixon and Gomathi maintain that private unrecognised unaided schools in Hyderabad, India, catering for children of the poor, provide a better level of education than do their government counterparts. We examine this contention and argue first that Tooley et al.’s conceptualisation of education and its benefits is flawed and second that the evidence selected and provided to prove the empirical side of the case is one‐sided and unrepresentative. We conclude that their case remains unproven and that flaws in the argument and its evidence provide no substantial case for their contention.     

A computer-based strategy for personalizing verbal problems in teaching mathematics

The purpose of this study was to evaluate a computer-based strategy for personalizing verbal problems used in mathematics instruction. Personalization was achieved through a computer program that incorporated names of familiar people and events, such as the student’s friends and birth date, into print copies of lesson examples. In two control treatments, concrete (nonadaptive) contexts and abstract contexts were employed. Subjects were 54 fifth- and sixthgraders studying a lesson on division of fractions. Results showed the personalized-context treatment to be advantageous relative to one or both control treatments for (a) solving conventional word problems, (b) solving transfer problems, (c) recognizing rule procedures, and (d) developing favorable attitudes toward materials. Theoretical interpretations of these effects are discussed, along with considerations about the practicality and effectiveness of the present application using print materials compared to an earlier one using CAl.     

Personalizing context in teaching mathematical concepts: Teacher-managed and computer-assisted models

The present paper examines a strategy intended to facilitate mathematics learning by adapting the context of instructional material to students’ backgrounds and interests. In four validation studies, the strategy was implemented through teacher management, using college students learning statistical probability rules as subjects. Achievement and attitude outcomes consistently favored treatment groups who received the adaptive contexts over control groups. The culmination of this research is the development of a computer-assisted model to increase the strategy’s practicality and sensitivity to learner differences. The computer model uses stored information about each student to personalize explanations and story examples on a fractions unit.