Effort Constraints Research Articles

The influence of regularization on anechoic performance and robustness of sound zone methods

Recent attention to the problem of controlling multiple loudspeakers to create sound zones has been directed toward practical issues arising from system robustness concerns. In this study, the effects of regularization are analyzed for three representative sound zoning methods. Regularization governs the control effort required to drive the loudspeaker array, via a constraint in each optimization cost function. Simulations show that regularization has a significant effect on the sound zone performance, both under ideal anechoic conditions and when systematic errors are introduced between calculation of the source weights and their application to the system. Results are obtained for speed of sound variations and loudspeaker positioning errors with respect to the source weights calculated. Judicious selection of the regularization parameter is shown to be a primary concern for sound zone system designers—the acoustic contrast can be increased by up to 50 dB with proper regularization in the presence of errors. A frequency-dependent minimum regularization parameter is determined based on the conditioning of the matrix inverse. The regularization parameter can be further increased to improve performance depending on the control effort constraints, expected magnitude of errors, and desired sound field properties of the system.

Sequential contests with synergy and budget constraints

We study a sequential Tullock contest with two stages and two identical prizes. The players compete for one prize in each stage and each player may win either one or two prizes. The players have either decreasing or increasing marginal values for the prizes, which are commonly known, and there is a constraint on the total effort that each player can exert in both stages. We analyze the players’ allocations of efforts along both stages when the budget constraints (effort constraints) are either restrictive, nonrestrictive or partially restrictive. In particular, we show that when the players are either symmetric or asymmetric and the budget constraints are restrictive, independent of the players’ values for the prizes, each player allocates his effort equally along both stages of the contest.

Implementation and Analysis of the Bee Colony Optimization algorithm for Fault based Regression Test Suite Prioritization

Regression Testing is an important maintenance phase testing activity. The importance of this activity lies in the fact that it imparts confidence and accuracy in the modified code, as well as keeps a check on the unmodified parts, if they are affected or not. But there is a severe requirement to reorder the development testing test suite because of the constrained software development budget, time and effort. So techniques have to be developed to prioritize test cases to reduce budget, time and effort constraints effectively. In this paper implementation and analysis of an existing fault based regression test suite has been done. The prioritization algorithm is based on the nature inspired algorithm called Bee Colony Optimization (BCO) algorithm. The algorithm is a two step procedure which maps the food foraging behavior of scout bee and forager bee one after the other to reach to the solution. The analysis of the examples using the code developed indicates that the two step BCO algorithm is able to produce results which are comparable to optimal results.

UNCERTAIN CONTEXT FACTORS IN ERP PROJECT ESTIMATION ARE AN ASSET: INSIGHTS FROM A SEMI-REPLICATION CASE STUDY IN A FINANCIAL SERVICES FIRM

This paper reports on the findings of a case study in a company in the financial services sector in which we replicated the use of a previously published approach to systematically balance the contextual uncertainties in the estimation of Enterprise Resource Planning (ERP) projects. The approach is based on using three techniques, a parametric model, namely COCOMO II, a portfolio management model, and Monte Carlo simulations. We investigated (i) whether the adjustment of uncertain cost drivers in the COCOMO II model increases the chance of project success in a portfolio of ERP projects, (ii) which cost drivers of the COCOMO II model can be adjusted in a way that maximized the chance of portfolio success under time constraints, and (iii) which cost drivers of the COCOMO II model can be adjusted in a way that maximized the chance of portfolio success under effort constraints. We found that 11 COCOMO II cost drivers can be changed so that the change impacts the project outcomes under both time and effort constraints. This result is different from the result in the first case study in which 13 such factors were found.

An Evaluation of the Management Effectiveness of a Stock Re-Building Strategy for a Multi-Species Demersal Trap Fishery in Abu Dhabi, United Arab Emirates

The off-shore demersal trap fishery in the southern Arabian Gulf has been managed by gear regulations and effort constraints which were aimed at rebuilding depleted stocks. In order to evaluate the success of these regulations, a variety of selectivity and other fishery metrics were compared for the key species (Diagramma pictum, Epinephelus coioides and Lethrinus nebulosus) before and after their introduction. With the exception of a minor increase in the mean age at first capture from 1.3 yrs to 1.9 yrs for E. coioides, there were no significant changes in the values or trends in juvenile retention, mean size or the mean sizes and ages at first capture. The comparison of selectivity ogives with data derived independently through an experimental fishing program indicated that the failure of juvenile escape panels to modify the selectivity characteristics of the fishery could not be attributed to a lack of compliance. Furthermore, there were no significant changes in fishing mortality rates, harvest rates, catch, effort, yield per recruit and relative spawner biomass per recruit following the introduction of the management regulations. Age structures were highly truncated and the management measures had failed to increase the relative proportion of older age classes. Stock status indicators suggested that all species were heavily over-exploited with evidence of both growth and recruitment over-fishing. Given the failure of existing regulations to modify gear selectivity, reduce effort and rebuild stocks, the results of the study suggest that management authorities should consider alternative measures including a moratorium on the use of traps in the off-shore demersal fishery of Abu Dhabi.

A customizable pattern‐based software process simulation model: design, calibration and application

AbstractSoftware process analysis and improvement relies heavily on empirical research. Empirical research requires measurement, experimentation, and modeling. However, whatever evidence is gained via empirical research is strongly context dependent. Thus, it is hard to combine results and capitalize upon them for the purpose of improvement in evolving development environments. The process simulation model GENSIM 2.0 addresses these challenges. GENSIM 2.0 is a generic process simulation tool representing V‐model type software development processes. Compared to existing process simulation models in the literature, the novelty of GENSIM 2.0 is twofold. Firstly, its model structure is customizable to organization‐specific processes. This is achieved by using a limited set of generic structures (macro‐patterns). Secondly, its model parameters can be easily calibrated to available empirical data and expert knowledge. This is achieved by making the internal model structures explicit and by providing guidance on how to calibrate model parameters. This article outlines the structure of GENSIM 2.0, gives examples on how to calibrate the model to available empirical data, and demonstrates its usefulness through two application scenarios The first scenario illustrates how GENSIM 2.0 helps in finding effective combinations of verification and validation techniques under given time and effort constraints. The second scenario shows how the simulator supports in finding the best combination of alternative verification techniques. Copyright © 2009 John Wiley & Sons, Ltd.

Comparing the role of the anterior cingulate cortex and 6-hydroxydopamine nucleus accumbens lesions on operant effort-based decision making.

Both the anterior cingulate cortex (ACC) and mesolimbic dopamine, particularly in the nucleus accumbens (NAc), have been implicated in allowing an animal to overcome effort constraints to obtain greater benefits. However, their exact contribution to such decisions has, to date, never been directly compared. To investigate this issue we tested rats on an operant effort-related cost-benefit decision-making task where animals selected between two response alternatives, one of which involved investing effort by lever pressing on a high fixed-ratio (FR) schedule to gain high reward [four food pellets (HR)], whereas the other led to a small amount of food on an FR schedule entailing less energetic cost [two food pellets, low reward (LR)]. All animals initially preferred to put in work to gain the HR. Systemic administration of a D2 antagonist caused a significant switch in choices towards the LR option. Similarly, post-operatively, excitotoxic ACC lesions caused a significant bias away from HR choices compared with sham-lesioned animals. There was no slowing in the speed of lever pressing and no correlation between time to complete the FR requirement and choice performance. Unexpectedly, no such alteration in choice allocation was observed in animals following 6-hydroxydopamine NAc lesions. However, these rats were consistently slower to initiate responding when cued to commence each trial and also showed a reduction in food hoarding on a species-typical foraging task. Taken together, this implies that only ACC lesions, and not 6-hydroxydopamine NAc lesions as performed here, cause a bias away from investing effort for greater reward when choosing between competing options

Going once, going twice, sold! The committee assignment process as an all-pay auction

I analyze the committee assignment process as an all-pay auction and derive equilibrium lobbying strategies of legislators competing for vacant seats on a committee. The model illustrates the relationship between sincere and revealed preferences, which earlier formal models of committee assignment do not explicitly consider. Incorporating seniority, party loyalty, effort constraints, or committee transfers can discourage those who highly value the assignment from competitively lobbying for the seat. I also offer an alternative interpretation of the model’s parameters to consider the pure partisan assignment model, where efforts are contributions to the party’s collective good.

The Effect of Alternative Procedural Explanation Types on Procedural Knowledge Acquisition during Knowledge-Based Systems Use

This study applies Adaptive Character of Thought-Rational (ACT-R), a theory of cognitive skill acquisition, to identify two techniques theorized to provide learners with a simplified and situation-responsive set of production rules to use in a problemsolving context. The two techniques are abstraction (an optimization technique that produces a generalized rule set) and goal structuring (another optimization technique that produces a differentiated rule set). Accordingly, abstraction and goal structuring explanations were provided to users through a knowledge-based system (KBS). Due to cognitive effort constraints on procedural learning, a subset of volunteer participants was extracted for analysis based on an exhibition of attentive learning behavior. Results of the study found that while intermediary stages of development were not detectable, participants receiving goal-structuring explanations exhibited better problem solving performance, and the joint presentation of abstraction explanations led to further problem solving improvements. Abstraction explanations did not lead to improved problem solving, however, when provided in absence of goal-structuring explanations. These findings extend ACT-R to a new venue, increase understanding of ACT-R theory, and provide developers of KBS with more substantive knowledge on optimization of KBS explanation design when knowledge transfer to less expert users is an objective.

Control of manipulators in a constrained workspace by means of linked invariant sets

AbstractWe propose a new technique for controlling manipulators in constrained environments. Based on recent developments on constrained control theory, our approach basically consists in covering the admissible region of the configuration space by partially overlapping convex polyhedra arbitrarily fixed and forming a connected family. Each of these polyhedra, defined in the configuration space, is suitably extended in the state‐space (i.e. configuration‐plus‐velocity space) in order to maintain all the original connections among regions and to be a tracking domain of attraction for the system, i.e. a set of initial states from which a reference signal can be asymptotically approached without constraints violation during the transient. The connection path is not generated a priori, but it is automatically produced on‐line by a hierarchical feedback controller. A high‐level controller selects the confining polyhedron, to which the current state has to be transferred, which is the closest to the one containing the target reference. A low‐level controller solves the problem of locally tracking a suitable crossing point to the desired new region under constraints. The robustness of the scheme as well as the control effort constraints are also taken into account. Copyright © 2004 John Wiley & Sons, Ltd.

Applying effort constraints on adaptive feedforward control using the active set method

Applying effort constraints on adaptive feedforward control using the active set method

Robust feedback control of flow-induced structural radiation of sound

A significant amount of the interior noise of aircraft and automobiles is a result of turbulent boundary layer excitation of the vehicular structure. In this investigation, the feasibility of active robust feedback control of the noise due to this type of excitation is studied. The structural sound radiation system investigated is comprised of a simply supported panel excited by turbulent flow. An analytical model of this system is developed to evaluate the robust feedback control system design strategy. The model consists of a modal description of the excitation of the plate by a turbulent boundary layer, a modal representation of the plate vibrations, and an acoustic model of the sound radiated from the plate. Parametric uncertainties of 1% variation in the natural frequencies and 5% variation in the damping ratio are considered. A frequency domain controller design approach is utilized to develop a robust controller. Performance objectives are specified which include output performance of the sound radiated by the plate and control effort constraints on the force applied to the plate by the controller. Plate acceleration feedback is used in an effort to reduce the sound-pressure level. Approximately 16 and 8 dB of sound-pressure level reduction were achieved at the first and third resonances, respectively.

Effort constraints in adaptive feedforward control

Adaptive algorithms are presented for constrained multichannel feedforward control. They minimize the sum of squared error signals while limiting the value of either the sum of squared control signals (total effort) or the mean square value of each individual control signal (individual efforts). It is shown that the exact least squares solutions for these problems have a simple form, which can be approached with an adaptive algorithm. The properties of the resulting algorithm are illustrated by simulation.

Utilization of Control Effort Constraints in Linear Controller Design

A linear controller design procedure, which accounts for constraints on control effort, is developed by requiring that the control system utilize the maximum energy delivering capability of the final control elements under some specified test conditions (e.g., maximum step reference input). Results using this approach are available from previous studies for low-order single-input single-output controlled systems. This paper presents results for multi-input multi-output systems where the number of inputs is equal to the number of states. Both state variable feedback control for regulation, and integral plus state variable feedback control for tracking are considered and illustrated with an example problem.

Policy Entrepreneurs and Policy Divergence: John R. Commons and William Beveridge

British and American labor-market policies such as workmen's compensation, public employment offices, and unemployment insurance diverged markedly as they evolved after 1900. Most cross-national social policy studies compare such macropolitical variables as spending, culture, wealth, and political competition. This study takes an alternative micropolitical approach in order to detail the links between policy effort, program design, and macropolitical constraints. It compares two leading authorities on labor-market problems after 1900, John R. Commons in the United States and William Beveridge in Britain. Differences between American and British labor-market policy reflect differences between the strategies of Commons and Beveridge rather than their relative influence and effectiveness. These strategies reflect pragmatic adaptations to contrasting political cultures and structures. American federalism exerted effects that limited effort and narrowed the range of feasible policy options in the United States.

Functional analytic analysis of a pursuit problem

Some new results related to pursuit problems considered in Ref. 1 are presented here. The present formulation of the problem is more general than that of Ref. 1 in some respects. It allows one to consider magnitude, effort, and energy constraints on the control action. The concept of interceptibility of the pursued by the pursuer is introduced. Several necessary and sufficient conditions of interception are then developed. Finally, optimal strategies of pursuit are discussed.

On an inverse problem in optimal control

The problem of optimizing linear-stationary control systems subject to quadratic performance indices and bounded control effort constraints is studied. This problem was first proposed by Letov [1]. His solution, however, has been found to be valid only in some special cases [3]. In this paper, necessary and sufficient conditions for the existence of the optimal control laws of the saturation type are developed. It is shown that the weighting factors in the performance index have to be chosen in a particular manner, and the plants have to satisfy certain conditions to yield an optimal saturation type control law. As the weighting on the control effort in the performance index is decreased, the optimal solution approaches a bang-bang type singular control.

On synthesizing optimal controls

A synthesis procedure for a wide class of optimal processes is presented. Linear processes are considered under the following types of optimization criteria and constraints: (1) Under control amplitude constraint, either minimize control effort or minimize time. (2) Under effort constraint, minimize time. (3) Under both amplitude and effort constraints, minimize time. (4) Under no constraint, minimize effort. In each case, the control system is to take the state vector from a given initial state to a given terminal state, or to a given terminal closed convex set. Control effort is understood either in the sense of maximum amplitude or of an integral of a certain function of the control. It is well known that such optimal controls can be given in terms of a solution of the adjoint system of differential equations of the original system. The main difficulty in computing the optimal control lies in finding the initial conditions of the adjoint system. By geometric arguments, a function of the initial condition is developed, and it is shown that this function attains a maximum at the desired value of the initial condition. Furthermore, the gradient of this function is shown to have a simple form, so that the maximum can be directly computed by the method of steepest ascent.

Final value systems with total effort constraints

Final value systems with total effort constraints