Boundary and internal conditions for adjoint fluid-flow problems

The ever-increasing robustness and reliability of flow-simulation methods have consolidated CFD as a major tool in virtually all branches of fluid mechanics. Traditionally, those methods have played a crucial role in the analysis of flow physics. In more recent years, though, the subject has broadened considerably, with the development of optimization and inverse design applications. Since then, the search for efficient ways to evaluate flow-sensitivity gradients has received the attention of numerous researchers. In this scenario, the adjoint method has emerged as, quite possibly, the most powerful tool for the job, which heightens the need for a clear understanding of its conceptual basis. Yet, some of its underlying aspects are still subject to debate in the literature, despite all the research that has been carried out on the method. Such is the case with the adjoint boundary and internal conditions, in particular. The present work aims to shed more light on that topic, with emphasis on the need for an internal shock condition. By following the path of previous authors, the quasi-1D Euler problem is used as a vehicle to explore those concepts. The results clearly indicate that the behavior of the adjoint solution through a shock wave ultimately depends upon the nature of the objective functional.

Reaction-diffusion systems coupled at the boundary and the Morse-Smale property

We study an one-dimensional nonlinear reaction-diffusion system coupled on the boundary. Such system comes from modeling problems of temperature distribution on two bars of same length, jointed together, with different diffusion coefficients. We prove the transversality property of unstable and stable manifolds assuming all equilibrium points are hyperbolic. To this end, we write the system as an equation with noncontinuous diffusion coefficient. We then study the nonincreasing property of the number of zeros of a linearized nonautonomous equation as well as the Sturm-Liouville properties of the solutions of a linear elliptic problem. (C) 2008 Elsevier Inc. All rights reserved.

Estimation of genetic variance for macro- and micro-environmental sensitivity using double hierarchical generalized linear models

Background: Genetic variation for environmental sensitivity indicates that animals are genetically different in their response to environmental factors. Environmental factors are either identifiable (e.g. temperature) and called macro-environmental or unknown and called micro-environmental. The objectives of this study were to develop a statistical method to estimate genetic parameters for macro- and micro-environmental sensitivities simultaneously, to investigate bias and precision of resulting estimates of genetic parameters and to develop and evaluate use of Akaike’s information criterion using h-likelihood to select the best fitting model. Methods: We assumed that genetic variation in macro- and micro-environmental sensitivities is expressed as genetic variance in the slope of a linear reaction norm and environmental variance, respectively. A reaction norm model to estimate genetic variance for macro-environmental sensitivity was combined with a structural model for residual variance to estimate genetic variance for micro-environmental sensitivity using a double hierarchical generalized linear model in ASReml. Akaike’s information criterion was constructed as model selection criterion using approximated h-likelihood. Populations of sires with large half-sib offspring groups were simulated to investigate bias and precision of estimated genetic parameters. Results: Designs with 100 sires, each with at least 100 offspring, are required to have standard deviations of estimated variances lower than 50% of the true value. When the number of offspring increased, standard deviations of estimates across replicates decreased substantially, especially for genetic variances of macro- and micro-environmental sensitivities. Standard deviations of estimated genetic correlations across replicates were quite large (between 0.1 and 0.4), especially when sires had few offspring. Practically, no bias was observed for estimates of any of the parameters. Using Akaike’s information criterion the true genetic model was selected as the best statistical model in at least 90% of 100 replicates when the number of offspring per sire was 100. Application of the model to lactation milk yield in dairy cattle showed that genetic variance for micro- and macro-environmental sensitivities existed. Conclusion: The algorithm and model selection criterion presented here can contribute to better understand genetic control of macro- and micro-environmental sensitivities. Designs or datasets should have at least 100 sires each with 100 offspring.

Exempt treatment of financial intermediation services under a value-added tax: an assessment of alternatives

Most countries with a value-added tax (VAT) exempt financial intermediation services from the tax. While exemption is generally perceived to be undesirable, it is also widely regarded as unavoidable because of technical difficulties in applying VAT to these services. This article reviews the standard rationale for exempt treatment and then considers the relative merits of two recent challenges raised in the tax literature. The first challenge involves the application of cash flow taxation to financial intermediation services in a manner that is consistent with an invoice/credit VAT (which is the dominant form). The second challenge proposes a comprehensive system of zero-rating of financial intermediation services, which is supported by a characterization of the household consumption of such services as non-taxable. The author argues that each of these alternatives to an exemption system suffers from both theoretical and practical implementation difficulties that make maintenance of exempt treatment the preferred approach, at least in the short term. There is, however, a simpler alternative to these fundamental reform options, involving modification of just one aspect of an exemption system to relieve some of its more problematic aspects. Many of the interpretative problems and associated inefficiencies that plague an exemption system arise from the need to distinguish between taxable and exempt financial services. The author argues that these difficulties can be eliminated, to a large extent, by basing the distinction on the form of prices. In support of this approach, he points out that it is consistent with the underlying reasons for the application of exempt treatment. The author considers a number of other possible modifications, but these are either rejected outright or viewed with a healthy skepticism. For example, the author is critical of the apparent rationale for the application of cash flow taxation to property and casualty insurers. He also rejects proposals that accept some looseness in the formulaic allocation by financial intermediaries of the costs of business inputs between exempt and taxable services for input credit purposes. In his view, an explicit reliance on pricing structures to draw the boundary between exempt and taxable services is preferable to the provision of relief for blocked input tax credits of financial intermediaries. Finally, the author is skeptical of the case for a policy response intended to address the tax bias under an exemption system for financial intermediaries to insource supplies.

Dynamic output feedback sliding-mode control using pole placement and linear functional observers

This paper presents a methodological approach to design dynamic output feedback sliding-mode control for a class of uncertain dynamical systems. The control action consists of the equivalent control and robust control components. The design of the equivalent control and the sliding function are based on the pole-placement technique. Linear functional observers are developed to implement the sliding function and the equivalent control. Stability of the resulting system under the proposed control scheme is guaranteed. A numerical example is given to demonstrate its efficacy.

Identifying the predictors of employee health and satisfaction in an NPM environment : testing a comprehensive and non-linear demand-control-support model

The Demand-Control-Support (DCS) model is investigated in the context of police officers working within an organization that has relatively widespread uptake of New Public Management (NPM) practices. A survey of 479 police officers from two geographic regions was undertaken and the results indicate that the DCS offers a simple, yet powerful, framework for identifying the conditions to be managed in an NPM-oriented environment. Job control and work-based support predict all four target variables, strengthening the view that decision-making latitude and support from supervisors and colleagues represent critical resources for promoting the well-being, satisfaction and commitment of public sector employees.

Social control, self-control and psychosocial problems in adolescent males

‘Psychosocial problems’ are psychological problems that are regarded as resulting from the interaction between the adaptive capacities of individuals and the demands of their physical and social environments. Many different factors have been theoretically proposed, and empirically established, as predictors of a range of psychosocial problems in adolescents. However, a problem exists in that this literature appears to lack an integrative framework that has validity across the range of problems that are observed. The purpose of the current research is to propose and test a model that draws together three clusters of factors that are useful in predicting the incidence of adolescent psychosocial problems. These are family structural background factors, family functioning variables and control beliefs. Data were collected from 155 adolescent males aged between 12 and 19 by a single concurrent and retrospective self-report questionnaire. This included data about the respondent (age, involvements with mental health or juvenile justice agencies) and family structural background factors (days per week worked by mother/father, occupational status for mother/father, residential mobility, number of persons in the family home). The questionnaire also incorporated the Parental Bonding Instrument (Parker, Tupling & Brown, 1979) to quantify the levels of perceived parental care and overprotection, and an adaptation of the Parental Discipline Style Scale (Shaw & Scott, 1991), to assess punitive, love withdrawing and inductive discipline practices. In addition, the (Low) Self-control Scale (Grasmick, Tittle, Bursick & Arneklev, 1993) and the Locus of Control of Behaviour Scale (Craig, Franklin, & Andrews, 1984) were used to collect data concerning adolescents’ perceived behavioural self-control and locus of control. Finally, selected sub-scales of the Child Behavior Checklist Youth Self-Report (Achenbach, 1991b) were used to collect data on the incidence of social withdrawal, somatisation, anxiety and depression, aggression and delinquency among the respondents, and in aggregated form, the incidence of ‘total problems’ and internalising and externalising behaviours. Results indicated family structural background factors, family functioning variables and control beliefs possess limited predicted validity and that the usefulness of the proposed model varies between specific psychosocial problems. Family functioning variables were generally stronger predictors than family structural background factors, particularly for internalising behaviours. Of these, levels of parental care and overprotection were generally the strongest predictors. Perceived self-control and locus of control were also generally strong predictors, but were particularly powerful with respect to externalising behaviours. The strength of predictive relationships was observed to vary between specific internalising and externalising behaviours, suggesting that individual difference variables not assessed in the current research were differentially influential. Finally, the parental and individual characteristics that predicted maximal levels of adjustment (defined in terms of minimal levels of internalising and externalising behaviours) were explored and the correlates of various parenting style typologies (Parker et al., 1979) were investigated. These results strongly confirmed the importance of family functioning and control beliefs with respect to the prediction of internalising, externalising and well-adjusted behaviours. In all analyses, substantial proportions of the variance in the incidence of problem behaviours remain unexplained. The findings are examined in relation to previous research focused on (familial) social control and (individual) self-control with respect to psychosocial problems in adolescents. In addition, methodological considerations are discussed and the implications of the findings for clinical and community interventions to address problem behaviours, and for further study, are explored.

Accounting problems and issues in cases of municipal boundary changes

Analyses the methodologies and accounting treatments used for the transfer of assets, liabilities, revenues and expenses resulting from municipal restructuring in Victoria during the early 1990s. It was found that most municipalities adopted simple or pragmatic methods, whereby fixed assets and associated liabilities were allocated physically avoiding the need for financial valuations.

A new design of sliding mode control systems

A new sliding mode control technique for a class of SISO dynamic systems is presented in this chapter. It is seen that the stability status of the closed-loop system is first checked, based on the approximation of the most recent information of the first-order derivative of the Lyapunov function of the closed-loop system, an intelligent sliding mode controller can then be designed with the following intelligent features: (i) If the closed-loop system is stable, the correction term in the controller will continuously adjust control signal to drive the closed-loop trajectory to reach the sliding mode surface in a finite time and the desired closed-loop dynamics with the zero-error convergence can then be achieved on the sliding mode surface. (ii) If, however, the closed-loop system is unstable, the correction term is capable of modifying the control signal to continuously reduce the value of the derivative of the Lyapunov function from the positive to the negative and then drives the closed-loop trajectory to reach the sliding mode surface and ensures that the desired closed-loop dynamics can be obtained on the sliding mode surface. The main advantages of this new sliding mode control technique over the conventional one are that no chattering occurs in the sliding mode control system because of the recursive learning control structure; the system uncertainties are embedded in the Lipschitz-like condition and thus, no priori information on the upper and/or the lower bounds of the unknown system parameters and uncertain system dynamics is required for the controller design; the zero-error convergence can be achieved after the closed-loop dynamics reaches the sliding mode surface and remains on it. The performance for controlling a third-order linear system is evaluated in the simulation section to show the effectiveness and efficiency of the new sliding mode control technique.

Integrated modelling of cost-effective siting and operation of flow-control infrastructure for river ecosystem conservation

Wetland and floodplain ecosystems along many regulated rivers are highly stressed, primarily due to a lack of environmental flows of appropriate magnitude, frequency, duration, and timing to support ecological functions. In the absence of increased environmental flows, the ecological health of river ecosystems can be enhanced by the operation of existing and new flow-control infrastructure (weirs and regulators) to return more natural environmental flow regimes to specific areas. However, determining the optimal investment and operation strategies over time is a complex task due to several factors including the multiple environmental values attached to wetlands, spatial and temporal heterogeneity and dependencies, nonlinearity, and time-dependent decisions. This makes for a very large number of decision variables over a long planning horizon. The focus of this paper is the development of a nonlinear integer programming model that accommodates these complexities. The mathematical objective aims to return the natural flow regime of key components of river ecosystems in terms of flood timing, flood duration, and interflood period. We applied a 2-stage recursive heuristic using tabu search to solve the model and tested it on the entire South Australian River Murray floodplain. We conclude that modern meta-heuristics can be used to solve the very complex nonlinear problems with spatial and temporal dependencies typical of environmental flow allocation in regulated river ecosystems. The model has been used to inform the investment in, and operation of, flow-control infrastructure in the South Australian River Murray.