Assessment of classical database models for representing solids

Solid modeling is being explored as a method of representing three dimensional parts for mechanical design and manufacturing. This work analyzes the data storage requirements of the Boundary Representation and Constructive Solid Geometry methods of representing solid models. The ability of the database models (Hierarchical, Network, and Relational) to support solid modeling needs is evaluated. The goal is to determine the database model(s) best suited to store and manage the graphical data for solid model representat ions . Background information about mechanical engineering, graphics, and database models is presented. Entity-Relationship diagrams are used to define data requ irements

Information structures and database support for solid modeling

The question we are going to investigate is how to map solid representations to DB structures and how to process this information efficiently. Starting from analytical representations based on analytical methods we discuss the use of constructive solid geometry and boundary representation models with various refinements. Furthermore, additional submodels (organizational, technological, physical) are considered in order to obtain an overall product model. This model representing all important aspects of a complex design object may serve to derive special object representations needed by existing engineering tools or by mathematical methods (e.g. finite elements). Today's DBMS are unable to meet the increasing requirements of engineering applications that would prefer to use a DBMS. To alter this situation, a new generation of DBMS architectures tailored to the demands of such enhanced applications have to be developed. As a consequence, the flexibility and expressiveness of data models as well as the handling of application objects must be greatly improved before interactive design work can be supported. We outline our data model concepts and architectural decisions to provide effective data management support. Our DBMS architecture consists of a neutral kernel part running on a server machine and an application layer tailored to solid modeling tasks which together with the application, i.e. the solid modeler is allocated to the workstation

A spatial decision support system for designing solid waste collection routes in rural counties

Because of the increasing need to develop optimized routes for solid waste collection in rural counties, there has been a lot of research on exploring arc routing problems and their efficient solutions. The complex nature of solving arc routing problems lends itself to a GIS-based spatial decision support system. Such a system could combine user knowledge of a problem with heuristic algorithms to obtain arc routing solutions. This thesis presents SWRoute, which is such a system. Developing SWRoute requires three major steps: building a suitable geographic data base, determining and implementing the necessary heuristic algorithmic techniques, and setting up a GIS framework that allows users to manipulate the data inputs and the algorithm outputs. Taken together, these three components form a spatial decision support system for designing solid waste collection routes. The area of study is Hamblen County in East Tennessee. A database of roads in the county was developed using TIGER and other map sources. The demands for solid waste collection were obtained from the Hamblen County solid waste region. SWRoute also uses two modeling algorithms. The first is a heuristic algorithm for generating solutions to the rural arc routing problem. The second algorithm is used to develop lower bounds on candidate solutions. The lower bounds help determine the quality of the heuristic solutions. The SWRoute interface has tools which allow the user to partition a base road network into subnetworks and create a seed node set. The GIS interface is also useful for generating and reporting routes. With the aid of these tools, the user can study and manipulate solutions generated from the algorithms. The results derived from the Hamblen County example indicate how a GIS-based spatial decision support system can help solve complex problems facing rural U.S. counties

Kernel arquitecture for CAD/CAM in shipbuilding enviroments

The capabilities of complex software products such as CAD/CAM systems are strongly supported by basic information technologies related with data management, visualization, communication, geometry modeling and others related with the development process. These basic information technologies are involved in a continuous evolution process, but over recent years this evolution has been dramatic. The main reason for this has been that new hardware capabilities (including graphic cards) are available at very low cost, but also a contributing factor has been the evolution of the prices of basic software. To take advantage of these new features, the existing CAD/CAM systems must undergo a complete and drastic redesign. This process is complicated but strategic for the future evolution of a system. There are several examples in the market of how a bad decision has lead to a cul-de-sac (both technically and commercially). This paper describes what the authors consider are the basic architectural components of a kernel for a CAD/CAM system oriented to shipbuilding. The proposed solution is a combination of in-house developed frameworks together with commercial products that are accepted as standard components. The proportion of in-house frameworks within this combination of products is a key factor, especially when considering CAD/CAM systems oriented to shipbuilding. General-purpose CAD/CAM systems are mainly oriented to the mechanical CAD market. For this reason several basic products exist devoted to geometry modelling in this context. But these basic products are not well suited to deal with the very specific geometry modelling requirements of a CAD/CAM system oriented to shipbuilding. The complexity of the ship model, the different model requirements through its short and changing life cycle and the many different disciplines involved in the process are reasons for this inadequacy. Apart from these basic frameworks, specific shipbuilding frameworks are also required. This second layer is built over the basic technology components mentioned above. This paper describes in detail the technological frameworks which have been used to develop the latest FORAN version.Postprint (published version

The role of primitive part modelling within an integrative simulation environment

The component-based modeling approach to the simulation of HVAC systems has been in used for many years. The approach not only supports plant simulation but also allows the integration of the building and plant domains. Frequently, however, the plant models do not match exactly the types being used in a given project and where they do, may not be able to provide the required information. To address such limitations research has been undertaken into alternative approaches. The aim of such research is to provide a modeling approach that is widely applicable and offers efficient code management and data sharing. Primitive Part (PP) modeling is one such effort, which employs generic, process-based elements to attain modeling flexibility. Recent efforts have been on the development of data structure and graphics that facilitates PP auto-connection via computer interface. This paper describes the approach using an example application and its suggested role within an integrative simulation environment

Review of research in feature-based design

Research in feature-based design is reviewed. Feature-based design is regarded as a key factor towards CAD/CAPP integration from a process planning point of view. From a design point of view, feature-based design offers possibilities for supporting the design process better than current CAD systems do. The evolution of feature definitions is briefly discussed. Features and their role in the design process and as representatives of design-objects and design-object knowledge are discussed. The main research issues related to feature-based design are outlined. These are: feature representation, features and tolerances, feature validation, multiple viewpoints towards features, features and standardization, and features and languages. An overview of some academic feature-based design systems is provided. Future research issues in feature-based design are outlined. The conclusion is that feature-based design is still in its infancy, and that more research is needed for a better support of the design process and better integration with manufacturing, although major advances have already been made

IAC level "O" program development

The current status of the IAC development activity is summarized. The listed prototype software and documentation was delivered, and details were planned for development of the level 1 operational system. The planned end product IAC is required to support LSST design analysis and performance evaluation, with emphasis on the coupling of required technical disciplines. The long term IAC effectively provides two distinct features: a specific set of analysis modules (thermal, structural, controls, antenna radiation performance and instrument optical performance) that will function together with the IAC supporting software in an integrated and user friendly manner; and a general framework whereby new analysis modules can readily be incorporated into IAC or be allowed to communicate with it

Integration of geometric modeling and advanced finite element preprocessing

The structure to a geometry based finite element preprocessing system is presented. The key features of the system are the use of geometric operators to support all geometric calculations required for analysis model generation, and the use of a hierarchic boundary based data structure for the major data sets within the system. The approach presented can support the finite element modeling procedures used today as well as the fully automated procedures under development

Parameters influencing calcium phosphate precipitation in granular sludge sequencing batch reactor

Parameters influencing calcium phosphate precipitation in Calcium phosphate precipitation inside microbial granules cultivated in a granular sequenced batch reactor (GSBR) has been demonstrated to contribute to phosphorus removal during wastewater treatment. Whereas hydroxyapatite (HAP) is proven to accumulate in the granule, the main calcium phosphate precursors that form prior to HAP are here investigated. A separate batch reactor was used to distinguish reactions involving biological phosphate removal from physicochemical reactions involving phosphateprecipitation in order to establish the kinetics and stoichiometry of calcium phosphate formation. Experiments and simulations with PHREEQC and AQUASIM software support the assumption that amorphous calciumphosphate (ACP) is the intermediary in HAP crystallization. The results provide the kinetic rate constants and thermodynamic constants of ACP. The formation of bioliths inside biological aggregates as well as the main parameters that drive their formations are discussed here. Finally, the influence of pH and calcium and phosphate concentrations in the influent was also assessed, in order to determine the contribution of precipitation in the different operating conditions