The paper explores the possibility to create a general data management system based on doubly connected circular lists. This system would be very useful for the rapid development of the computer based models in engineering. The basic element of the list must have a general structure because it is the basic ‘building block’ in the concept development. Several solutions were studies, two of them being finally considered for extensive tests. The first solution is based on the ‘union’ data type which is simple and robust, but it has a series of inconveniencies. The second solution includes the declaration of a pointer to a random location in memory, at that address being found a given data type. The declaration is general, but the handling of a given data type requires particular declarations and functions. This latest solution is the most general one and it may be used to develop software for the most common data types, which will be useful for the rapid development of the upper level of complexity software applications. So far, the testing of the solutions and of their variants is still in progress in order to have a more accurate insight.
A thorough analysis reveals that the approximation theory has various applications in the computer aided engineering. The early ideas about approximation and spline functions were related to the graphical aspects in the general design of a motor vehicle1. Since then, the ideas evolved together with the tremendous progress of the computer science which offered software platforms with advanced numerical methods’ solvers. Beside the original computer instruments we developed, a far better idea is to gather ‘la crème de la crème’, the best of the best software concepts and solutions in a unique strategy of development. This meta-level of understanding and integration is useful for the rapid development of computer based hybrid models to be used in complex research problems. We consequently selected GNU OCTAVE as a scientific programming platform which might provide the solutions (in various forms) of the interpolation problems using spline functions. The initial solution4 was constantly upgraded with respect to the context of the case studies to be solved. After 98 interpolation problems solved over 5 years, new important facilities were added to the initial software solution. The main directions are: generalization of the program which should not include case studies dedicated sequences (no hard coded sequences), several and more reliable links to upper level applications and new facilities used to control the aspect of the graphical output because the visual control may evaluate the output data in a more effective way than the mathematical/technical conditions. The upgraded version of the software may be considered a milestone in the progress of the ‘general modeling original platform development’ concept9.
The paper is an exploratory research regarding the identification of some of the basic ideas used to conceive solutions of general-defined problems. In this way, there is firstly presented the set of ideas used to choose the type of model to be developed. The general problem solver and the related problems are also presented in the paper. In this case there is used a greedy approach which may lead to large run time values of the according software. To significantly decrease the computer time used to solve such a problem, there is also presented a method used to minimize the search space of the candidate solutions, in this case being used an intelligent solver, that is more effective than the greedy method. Two examples of models based on the previously presented general directions are also given. The first example presents an algorithm used to solve an equilibrium problem in ship strength problems. The second example is in electronic engineering. The ideas presented in the paper are important to identify the concepts employed to design modeling strategies and also for the development of the original software instruments structured as reusable libraries.
The paper presents an original computer based analytical model of a half-bridge belonging to a circular settling tank. The primary unknown is computed using the force method, the coefficients of the canonical equation being calculated using either the discretization of the bending moment diagram in trapezoids, or using the relations specific to the polygons. A second algorithm based on the method of initial parameters is also presented. Analyzing the new solution we came to the conclusion that most of the computer code developed for other model may be reused. The results are useful to evaluate the behavior of the structure and to compare with the results of the finite element models.
Automatic data processing and visualization in the finite elements analysis of the structural problems is a long run concern in mechanical engineering. The paper presents the ‘common database’ concept according to which the same information may be accessed from an analytical model, as well as from a numerical one. In this way, input data expressed as comma-separated-value (CSV) files are loaded into the Femap/Nastran environment using original API codes, being automatically generated: the geometry of the model, the loads and the constraints. The original API computer codes are general, being possible to generate the input data of any model. In the next stages, the user may create the discretization of the model, set the boundary conditions and perform a given analysis. If additional accuracy is needed, the analyst may delete the previous discretizations and using the same information automatically loaded, other discretizations and analyses may be done. Moreover, if new more accurate information regarding the loads or constraints is acquired, they may be modelled and then implemented in the data generating program which creates the ‘common database’. This means that new more accurate models may be easily generated. Other facility consists of the opportunity to control the CSV input files, several loading scenarios being possible to be generated in Femap/Nastran. In this way, using original intelligent API instruments the analyst is focused to accurately model the phenomena and on creative aspects, the repetitive and time-consuming activities being performed by the original computer-based instruments. Using this data processing technique we apply to the best Asimov’s principle ‘minimum change required / maximum desired response’.
Proc. SPIE. 10010, Advanced Topics in Optoelectronics, Microelectronics, and Nanotechnologies VIII
KEYWORDS: Mathematical modeling, General applications engineering, Data modeling, Data storage, Computer simulations, Calculus, Data acquisition, Data processing, Analytical research, Instrument modeling
Experimental data processing is an issue that must be solved in almost all the domains of science. In engineering we usually have a large amount of data and we try to extract the useful signal which is relevant for the phenomenon under investigation. The criteria used to consider some points more relevant then some others may take into consideration various conditions which may be either phenomenon dependent, or general. The paper presents some of the ideas and tests regarding the identification of the best set of criteria used to filter the initial set of points in order to extract a subset which best fits the approximated function. If the function has regions where it is either constant, or it has a slow variation, fewer discretization points may be used. This means to create a simpler solution to process the experimental data, keeping the accuracy in some fair good limits.
This paper presents new approaches regarding the use of Product Lifecycle Management concept to achieve knowledge integration of the academic disciplines in the maritime education context. The philosophy of the educational system is now changing faster worldwide and it is in a continuous developing process. There is a demand to develop modern educational facilities for CAD/CAE/CAM training of the future maritime engineers, which offers collaborative environments between the academic disciplines and the teachers. It is well known that the students must understand the importance of the connectivity between the academic disciplines and the computer aided methods to interface them. Thus, besides the basic knowledge and competences acquired from the CAD courses, students learn how to increase the design productivity, to create a parametric design, the original instruments of automatic design, 3D printing methods, how to interface the CAD/CAE/CAM applications. As an example, the Strength of Materials discipline briefly presents alternate computer aided methods to compute the geometrical characteristics of the cross sections using the CAD geometry, creation the free body diagrams and presentation the deflected shapes of various educational models, including the rotational effect when the forces are not applied in the shear center, using the results of the FEM applications. During the computer aided engineering academic disciplines, after the students design and analyze a virtual 3D model they can convert it into a physical object using 3D printing method. Constanta Maritime University offers a full understanding of the concept of Product Lifecycle Management, collaborative creation, management and dissemination.
The paper presents an original analytical model of the hydrodynamic loads applied on the half-bridge of a circular settling tank. The calculus domain is defined using analytical geometry and the calculus of the local dynamic pressure is based on the radius from the center of the settling tank to the current area, i.e. the relative velocity of the fluid and the depth where the current area is located, i.e. the density of the fluid. Calculus of the local drag forces uses the discrete frontal cross sectional areas of the submerged structure in contact with the fluid. In the last stage is performed the reduction of the local drag forces in the appropriate points belonging to the main beam. This class of loads is producing the flexure of the main beam in a horizontal plane and additional twisting moments along this structure. Taking into account the hydrodynamic loads, the results of the theoretical models, i.e. the analytical model and the finite element model, may have an increased accuracy.
Optical methods in experimental mechanics are important because their results are accurate and they may be used for both full field interpretation and analysis of the local rapid variation of the stresses produced by the stress concentrators. Researchers conceived several graphical, analytical and numerical methods for the experimental data reduction. The paper presents an original computer method employed to compute the analytic functions of the isostatics, using the pattern of isoclinics of a photoelastic model or coating. The resulting software instrument may be included in hybrid models consisting of analytical, numerical and experimental studies. The computer-based integration of the results of these studies offers a higher level of understanding of the phenomena. A thorough examination of the sources of inaccuracy of this computer based numerical method was done and the conclusions were tested using the original computer code which implements the algorithm.
Research and design engineers usually use three sources of information: analytic models, numerical models and experimental studies. Analytic and numerical models are theoretical models which must be calibrated and verified regarding the accuracy of their results using the data acquired from experimental studies. If these models are deeply integrated from the beginning, the overview result is a hybrid model. From this standpoint, the paper presents the underlying concepts and studies employed to create a hybrid model of a weighting device. The paper presents the analytic background of the problem to be solved, the numerical model and the dimensioning of the experimental device. The study is still in progress, the following stages being the manufacturing of the device and calibration of the weighting platform.