Constraint-based System Research Articles

Magnetohydrodynamic thermal convection in constraint-based recto-triangular cavities with CuO-water nanofluid and differential bottom-top heating

The current research explores the thermal convection of magnetohydrodynamic flow in modified and constraint-based recto-triangular thermal systems (upper part rectangular and lower part triangular) filled with copper-oxide water nanofluid. The external uniform magnetic field is applied horizontally, while the magnetic field angle γ is varied systematically. The volume/area of thermal system cavities is maintained the same while their bottom triangular portions are adjusted considering various vertex angles (Θ) of 90–270°. The cooling and heating arrangements are provided for the same lengths using the top wall and the central portion of the bottom wall, respectively. The finite element method is used to discretize and solve the dimensionless governing transport equations. The thermal and flow analyses are conducted on the backdrop of constraint-based thermal systems for varying pertinent parameters like the Rayleigh number (Ra = 103–105), Hartmann number (Ha = 0–70), magnetic field angle (γ = 0–90°) and vertex angle (Θ = 90–270°). It is revealed that the flow structure becomes more complex and asymmetric in nature at high Ra and Ha. Furthermore, the average Nu is an increasing function of Ra and Θ, whereas it is a decreasing function of Ha. The entropy plots are also generated to study the entropy generation due to magnetohydrodynamic, viscous dissipation, and thermal effects that together constitute the total entropy of the system. The constraint-based system analysis could be very helpful for the design and identification of the most efficient system for the utilized same working fluid (volume).

Using a constraint-based expert model to provide step-level feedback for user-inputted mathematics equations

Studies across a variety of educational fields have shown the efficacy of feedback on student performance and learning. Web-based homework is a common feature of secondary and collegiate mathematics courses to provide such feedback. While web-based homework provides often instantaneous feedback to students as they complete assignments, the feedback is limited to the correctness of the final answer or to a limited number of pre-programmed common mistakes. Intelligent Tutoring Systems have the ability to provide step-by-step feedback and guidance tailored to individual students, however authoring content for such systems is generally considered a huge barrier to their wider use. This paper presents an alternative system, called SANYMS (Show and Name Your Math Steps), which combines the wide-scale usability of web-based homework with a Constraint-Based Intelligent Tutoring System Expert Model based on the open-source computer algebra system Maxima. With the integration of Maxima, SANYMS can provide step-by-step feedback to students constructing their own solutions to a wide variety of algebraic equations of their choice without the need for extensive content authoring inherent in many Intelligent Tutoring Systems.

An Optimality Analysis and Treatment of Phonological Disorders in the Speech of Jordanian Children: A Case Study

This paper presents a case study of a Jordanian child with phonological speech disorders. It seeks to investigate functional phonological disorders and their treatment among Jordanian children within an Optimality Theoretic (OT) perspective. It aims to provide treatment for children’s speech errors within a constraint-based system. The analysis of the data identifies seven error patterns in the child’s productions, namely: fronting, lateralization, stopping, devoicing, de-emphasization, syllable deletion and cluster reduction. Furthermore, OT is employed at the end of the study as a guideline to select the priority of treatment goals by demoting responsible markedness constraints below faithfulness constraints.

Formalizing Visualization Design Knowledge as Constraints: Actionable and Extensible Models in Draco.

There exists a gap between visualization design guidelines and their application in visualization tools. While empirical studies can provide design guidance, we lack a formal framework for representing design knowledge, integrating results across studies, and applying this knowledge in automated design tools that promote effective encodings and facilitate visual exploration. We propose modeling visualization design knowledge as a collection of constraints, in conjunction with a method to learn weights for soft constraints from experimental data. Using constraints, we can take theoretical design knowledge and express it in a concrete, extensible, and testable form: the resulting models can recommend visualization designs and can easily be augmented with additional constraints or updated weights. We implement our approach in Draco, a constraint-based system based on Answer Set Programming (ASP). We demonstrate how to construct increasingly sophisticated automated visualization design systems, including systems based on weights learned directly from the results of graphical perception experiments.

An Optimality Analysis and Treatment of Phonological Disorders in the Speech of Jordanian Children: A Case Study

This paper presents a case study of a Jordanian child with phonological speech disorders. It seeks to investigate functional phonological disorders and their treatment among Jordanian children within an Optimality Theoretic (OT) perspective. It aims to provide treatment for children’s speech errors within a constraint-based system. The analysis of the data identifies seven error patterns in the child’s productions, namely: fronting, lateralization, stopping, devoicing, de-emphasization, syllable deletion and cluster reduction. Furthermore, OT is employed at the end of the study as a guideline to select the priority of treatment goals by demoting responsible markedness constraints below faithfulness constraints.

A constraint-based job recommender system integrating FoDRA

We present a framework for a constraint-based recommender system that matches available job positions with job seekers. Our framework utilises the four dimensions recommendation algorithm (FoDRA) in which a job attribute (e.g., age of candidate) can be modelled in four classes: exact value (E), a range with lower limit (L), a range with upper limit (U) and a range with both lower and upper limit (LU). FoDRA allows us to better formulate the job seeking and recruiting domain in a computational form. We describe both the system architecture in a high-level and the algorithm formulation of the job seeking and recruiting domain required by FoDRA. Our framework is validated through comparative experiments with real data obtained from the website of Kaggle.

Stochastic model predictive control for economic/environmental operation management of microgrids: An experimental case study

Microgrids are subsystems of the distribution grid which comprises generation capacities, storage devices and flexible loads, operating as a single controllable system either connected or isolated from the utility grid. In this work, microgrid management system is developed in a stochastic framework. It is seen as a constraint-based system that employs forecasts and stochastic techniques to manage microgrid operations. Uncertainties due to fluctuating demand and generation from renewable energy sources are taken into account and a two-stage stochastic programming approach is applied to efficiently optimize microgrid operations while satisfying a time-varying request and operation constraints. At the first stage, before the realizations of the random variables are known, a decision on the microgrid operations has to be made. At the second stage, after random variables outcomes become known, correction actions must be taken, which have a cost. The proposed approach aims at minimizing the expected cost of correction actions. Mathematically, the stochastic optimization problem is stated as a mixed-integer linear programming problem, which is solved in an efficient way by using commercial solvers. The stochastic problem is incorporated in a model predictive control scheme to further compensate the uncertainty through the feedback mechanism. A case study of a microgrid is employed to assess the performance of the on-line optimization-based control strategy and the simulation results are discussed. The method is applied to an experimental microgrid: experimental results show the feasibility and the effectiveness of the proposed approach.

Integrating 4D modeling and discrete event simulation for phasing evaluation of elevated urban highway reconstruction projects

Elevated urban highway reconstruction projects have complex geometry and limited space available, which may lead to spatiotemporal clashes. In addition, maintaining an acceptable flow of traffic without compromising safety in highway construction zones is another major issue for planners. This paper proposes a new method for generating and assessing reconstruction phasing plans and calculating the probability of stochastic spatiotemporal clashes associated with the optimal feasible phasing plan. A phasing plan assessment approach using a constraint-based system and 4D modeling is presented to define the feasible sequences in which the segments can be constructed or demolished. The result of this step is an optimal feasible phasing plan that meets a set of predefined constraints and creates no spatiotemporal clashes. This plan is then examined to calculate the probability of potential stochastic spatiotemporal clashes, which may happen when the variability of construction and demolition durations is considered, and to recommend the starting date of operations to minimize the probability of these clashes. The feasibility of the proposed method is explored through a case study.

A two-stage stochastic programming approach to employee scheduling in retail outlets with uncertain demand

This paper describes an employee scheduling system for retail outlets; it is a constraint-based system that exploits forecasts and stochastic techniques to generate schedules meeting the demand for sales personnel. Uncertain scenarios due to fluctuating demand are taken into account to develop a stochastic operational optimization of staffing levels. Mathematically, the problem is stated as a mixed-integer linear programming problem. Simulations with store data belonging to a major Swiss retailer show the effective performance of the proposed approach. The schedule quality is assessed through comparison with a deterministic scheduling package, which has been used at several outlets in Switzerland.

The Deployment of a Constraint-Based Dental School Timetabling System

We describe a constraint-based timetabling system that was developed for the dental school based at Cork University Hospital in Ireland. This system has been deployed since 2010. Dental school timetabling differs from other university course scheduling in that certain clinic sessions can be used by multiple courses at the same time, provided a limit on room capacity is satisfied. Starting from a constraint programming solution using a web interface, we have moved to a mixed integer programming-based solver to deal with multiple objective functions, along with a dedicated Java application, which provides a rich user interface. Solutions for the years 2010, 2011 and 2012 have been used in the dental school, replacing a manual timetabling process, which could no longer cope with increasing student numbers and resulting resource bottlenecks. The use of the automated system allowed the dental school to increase student numbers to the maximum possible given the available resources. It also provides the school with a valuable “what-if” analysis tool.

A Constraint Based Decision Support System for Deadlocks Resolution in Collaborative New Product Design

In this paper we are considering that the product modelling step of a new product design process can be represented as a CSP (Constraint Satisfaction Problem). CSP modelling and resolution has proved its efficiency within the framework of single-designer design. We propose to extend the functions of CSP to the context of multi-designers. We have recently defined CoCSP as Cooperative Constraint Satisfaction Problem including the actors of the design problem. We present the operating principles of a new algorithm to solve the deadlocks appearing between constraints in a new product modelling process. Our reasoning is based on a model described in the form of a CoCSP. At each step, the algorithm generates the sets of consistent decisions, maximizing their cardinality. The algorithm forms the core of a prototype for an unsupervised, generic constraint-based collaborative decision support system. The work is illustrated by the example of a car engine collaborative modelling process.

A CSP approach for the network of product lifecycle constraints consistency in a collaborative design context

In this paper, we are considering that the design process can be modelled in the form of a constraint satisfaction problem (CSP). CSP modelling or resolution has proved its efficiency within the framework of single-designer design. We propose to extend the functions of CSP to the context of multi-concept design of the same artefact. We define CoCSP as cooperative constraint satisfaction problem including the actors of the design problem. We are presenting the operating principles of an algorithm for the real-time management of design decisions, based on a model described in the form of a CoCSP for the integration of supply-chain constraints. This algorithm enables the number of design decisions rejected at a given moment in design to be kept to a minimum. The algorithm forms the core of a prototype for an unsupervised, generic constraint-based collaborative design system. Our aim is to produce a platform centred on the notion of constraints that will enable a product design problem to be modelled and solved by integrating supply-chain constraints as far upstream as possible.

Constraint-Based Multi-Completion Procedures for Term Rewriting Systems

In equational theorem proving, convergent term rewriting systems play a crucial role. In order to compute convergent term rewriting systems, the standard completion procedure (KB) was proposed by Knuth and Bendix and has been improved in various ways. The multi-completion system MKB developed by Kurihara and Kondo accepts as input a set of reduction orders in addition to equations and efficiently simulates parallel processes each of which executes the KB procedure with one of the given orderings. Wehrman and Stump also developed a new variant of completion procedure, constraint-based completion, in which reduction orders need not be given by using automated modern termination checkers. As a result, the constraint-based procedures simulate the execution of parallel KB processes in a sequential way, but naive search algorithms sometimes cause serious inefficiency when the number of the potential reduction orders is large. In this paper, we present a new procedure, called a constraint-based multi-completion procedure MKBcs, by augmenting the constraint-based completion with the framework of the multi-completion for suppressing the combinatorial explosion by sharing inferences among the processes. The existing constraint-based system Slothrop, which basically employs the best-first search, is more efficient when its built-in heuristics for process selection are appropriate, but when they are not, our system is more efficient. Therefore, both systems have their role to play.

The Visualization of Computer-Assisted Music Analysis Information in PWGL

We describe our recent developments in dealing with computer-assisted music analysis. Our focus is on a syntax that extends the pattern-matching part of our constraint-based system, called PWGLConstraints. This syntax is also the basis of our scripting language, which in turn is used to analyse scores. Our system allows reference to various high-level entities in a score, resulting in compact analysis rules that use only a minimal set of primitives. These rules can also be used to add information to the musical score when a visualization of the results is needed. Furthermore, the compiler can be extended to support new score-accessor keywords through the application of special compiler methods. Several examples are given to explain and demonstrate the syntax and visualization of the analysis data.

A constraint-based system for product design and manufacturing

Constraint-based modeling is one of the most modern methods of product design. This paper illustrates a collaborative design and manufacture procedures based on a new approach under the constraint-based solver for product design. Such a method can be used for the collaborative computer-aided design/manufacture systems. A developing model will be constructed from conceptual design to tool-paths generation, and a case study of how to make a playing doll house was presented to verify this system. The solver generates geometric models automatically and hierarchically when sufficient constraint relationships between geometric objects are given. By examining this developing model, all different operations can be integrated tightly and quickly from different locations and sub-systems. Also, benefits such as reduction in designing time, prototype-testing time and engineering personnel requirements, as well as mistake-free operation and simplification of manufacturing are attainable.

Emergent property of consistent updated geographical database

Geographic Information Systems (GIS) will be expected in the future to evolve as to integrate social simulations or ecological processes inside complex systems of active and interactive entities. In a more practical aspect, GIS has now to evolve to manage updating. We will explain how the updating processes can be described as an evolution processes for GIS and make them transform from complicated systems to complex systems. This evolution processus is decomposed through an influence table which corresponds to elementary canonical operations. In addition to these updating elementary operations, we verify, during the processus, the maintenancy of the whole Geographical Database (GDB) using a constraint-based system. Our goal is to make the updating satisfying the global consistent property which emerges from the computation over the whole evolutive system. In this paper, we will give the whole processus description which leads to obtain this emergent property of consistence from a dynamic propagation processus which allows to obtain the global consistence from a local satisfaction property.

A framework for supporting multidisciplinary engineering design exploration and life-cycle design using underconstrained problem solving

The problem investigated in this research is that engineering design decision making can be complicated and made difficult by highly coupled design parameters and the vast number of design parameters. This complication often hinders the full exploration of a design solution space in order to generate optimal design solution. These hindrances result in inferior or unfit design solutions generated for a given design problem due to a lack of understanding of both the problem and the solution space. This research introduces a computational framework of a new algebraic constraint-based design approach aimed at providing a deeper understanding of the design problem and enabling the designers to gain insights to the dynamic solution space and the problem. This will enable designers to make informed decisions based on the insights derived from parameter relationships extracted. This paper also describes an enhanced understanding of an engineering design process as a constraint centered design. It argues that with more effort and appreciation of the benefits derived from this constraint-based design approach, engineering design can be advanced significantly by first generating a more quantitative product design specification and then using these quantitative statements as the basis for constraint-based rigorous design. The approach has been investigated in the context of whole product life-cycle design and multidisciplinary design, aiming to derive a generic constraint-based design approach that can cope with life-cycle design and different engineering disciplines. A prototype system has been implemented based on a constraint-based system architecture. The paper gives details of the constraint-based design process through illustrating a worked real design example. The successful application of the approach in two highly coupled engineering design problems and the evaluation undertaken by a group of experienced designers show that the approach does provide the designers with insights for better exploration, enabled by the algebraic constraint solver. The approach thus provides a significant step towards fuller scale constraint-based scientific design.

AUTOMATIC MODEL CREATION FOR KINEMATIC ANALYSIS AND OPTIMIZATION OF ENGINEERING SYSTEMS

The successful adaptation and optimization of existing designs play an important role in the design of high speed machinery. Adaptation and extension of existing design principles to achieve some new functional or performance requirement is imperative for the development of the next generation of machines. In addition to this, continual improvement and optimization of existing designs are necessary to sustain a product's commercial success. Where complex mechanical systems are considered such design activities usually require the application of advanced simulation packages or intelligent CAD systems. The widespread utilization of such techniques, for all but the largest enterprises, is severely frustrated by the considerable level of resources required in order to retain a single, proficient user. These resources include extensive initial training as well as ongoing courses, the purchase of commercial licenses and more often than not, the considerable time and effort necessary for the creation and development of complex computer based models. As a consequence, many SMEs demand reliable, efficient and economical methods to generate simulation models for analysis and investigation. One method for delivering this is to provide an approach for the automatic creation of simulation models from data describing an existing design. Such an approach can reduce costs and resources as well as expedite the model building process. This paper presents a method for automatically generating a representative CAD model of a mechanical system. It supports the transformation of digital images into kinematic models for simulation and analysis. The method integrates motion analysis techniques, a parametric description of mechanical systems and a constraint-based CAD system.

Aggregating constraint satisfaction degrees expressed by possibilistic truth values

In information systems, one often has to deal with constraints in order to compel the semantics and integrity of the stored information or to express some querying criteria. Hereby, different constraints can be of different importance. A method to aggregate the information about the satisfaction of a finite number of constraints for a given data instance is presented. Central to the proposed method is the use of extended possibilistic truth values (to express the degree of satisfaction of a constraint) and the use of residual implicators and residual coimplicators (to model the impact and relevance of a constraint). The proposed method can be applied to any constraint-based system. A database application is discussed and illustrated.

Building assembly detailing using constraint-based modeling

Constraint-based geometric modeling entails specifying geometric constraints to control the locations of the components in an assembly. Consequently, any future modifications of the components are governed by these constraints. In this paper, a set of constraint-based assembly operations for generating 3D details of building assemblies are presented. The operations constrain the locations and orientations of the components in a building assembly through a series of constructive steps and therefore allow for easier modification. These operations are used in a modeling system that extends the idea of constraint-based modeling to detailing architectural building assemblies. The system utilizes the constraint-based assembly operations, which employ traditional geometric constraints integrated with a set of constructive assembly operations. The constraint-based assembly operations allow for a more systematic generation of the assembly details, which can save repetitive work and reduce mistakes resulting from copying and pasting old details. Also, the technique allows the assemblies to be studied and analyzed. To illustrate this idea, a prototype 3D constraint-based system for assembling three-dimensional architectural details was developed. With the proposed system, the details of building assemblies do not need to be reinvented for every project. Examples of the proposed approach are provided and its limitations and benefits are discussed.