Prognostic trend model of passenger transport performance of the Croatian maritime traffic system

This research analyses the dynamics and the modelling trend of the development of passenger transport performance of the Croatian maritime traffic system. Passenger transport performance represents a transport value which is, regarding its characteristic, a qualitative transport demand indicator in public passenger traffic, and expressed by the realized passenger transport operation in public maritime passenger traffic. Adequate mathematical statistic analysis of passenger transport performance has been performed at the level of maritime traffic system, forming in turn a mathematical prognostic trend model of the development dynamics of this traffic value. The prognostic trend model of the passenger transport performance is presented by a respective equation, with the calculation of the related determination coefficient as a measure of quality which determines the level of statistical significance of the description of the given data using the model equation. The law of development of the studied transport value during the considered time period is described by the computer calculated obtained model equation. During research, the scientific methods of mathematical statistics, modelling methods, and computer software «Microsoft Excel» have been used

Prognostic trend model of passenger transport performance of the Croatian maritime traffic system

This research analyses the dynamics and the modelling trend of the development of passenger transport performance of the Croatian maritime traffic system. Passenger transport performance represents a transport value which is, regarding its characteristic, a qualitative transport demand indicator in public passenger traffic, and expressed by the realized passenger transport operation in public maritime passenger traffic. Adequate mathematical statistic analysis of passenger transport performance has been performed at the level of maritime traffic system, forming in turn a mathematical prognostic trend model of the development dynamics of this traffic value. The prognostic trend model of the passenger transport performance is presented by a respective equation, with the calculation of the related determination coefficient as a measure of quality which determines the level of statistical significance of the description of the given data using the model equation. The law of development of the studied transport value during the considered time period is described by the computer calculated obtained model equation. During research, the scientific methods of mathematical statistics, modelling methods, and computer software «Microsoft Excel» have been used

Simulation of Aero Engine Pre- and Post-Stall Transient Behaviour

The commercial and operational attractiveness of improving the specific thrust, whilst minimising the weight, of an aero gas turbine engine, has inevitably led to the compressor operating as near to stall as is considered safe. However, it is acknowledged that under extreme circumstances a compressor will stall, and so effecting a quick recovery is important with respect to safety and mechanical integrity. Because of these ever increasing demands made on the performance of civil and military aero engines alike, it has become increasingly clear that a means of simulating pre- and post-stall transient behaviour is now a computer modelling requirement of the major engine manufacturers. Computer modelling is essential because a thorough experimental evaluation of the pre- and post-stall transient behaviour of an engine during a development programme, is prohibitively expensive. Further, such à capability will find applications in the stability assessment and fault diagnosis of existing production engines. Conventional transient performance computer codes operated within the aerospace industry, are limited to the simulation of engine performance during acceleration and deceleration. Performance prediction is good because the transient is predominately governed by spool inertia. However, account is not taken of the temporary accumulation of fluid mass, momentum and energy of flow disturbances as they pass through the engine; these effects become increasingly significant beyond frequencies of approximately 5 Hz. These codes are therefore incapable of predicting engine response, and in particular compressor stability, during high frequency flow transients such as a reheat mislight. Further, the simulation of any subsequent post-stall flow transients which typically occur at frequencies up to 40 Hz, is similarly not possible. This thesis marks the introduction of a high frequency modelling capability into just such a performance code, the Rolls-Royce Aero Engine Performance system, RRAP; and the extension of this capability to the simulation of whole engine performance during post-stall events. The high frequency response of an engine working fluid was achieved by splitting the engine into component volumes and solving time dependent equations conserving mass, momentum and energy across each. An extended version of the equations was used to predict radial flow, and hence further the modelling capability to multi-spool engines. The development of post-stall methods required extension of present compressor performance calculations as well as the introduction of post-stall performance characteristics. In addition, a whole new combustor model was developed to operate during low or reverse flow conditions commensurate with post-stall events. Together these modelling methods successfully simulated surge, cyclic surge and the 'descent' into rotating-stall. The simulations agreed favourably with test results. Development of these methods using the RRAP system has ensured that the work marked the beginning of a truely generic pre- and post-stall engine modelling capability; and that the ultimate objective of creating a computer model sufficiently reliable and accurate so that it may be used in engine design and development, is one step nearer.Ph

The development of a computer model to optimize the performance of a 50kWp photovoltaic system

A computer model has been developed to optimize the performance of a 50kWp photovoltaic system which supplies electrical energy to a dairy farm at Fota Island in Cork Harbour. Optimization of the system involves maximising the efficiency and increasing the performance and reliability of each hardware unit. The model accepts horizontal insolation, ambient temperature, wind speed, wind direction and load demand as inputs. An optimization program uses the computer model to simulate the optimum operating conditions. From this analysis, criteria are established which are used to improve the photovoltaic system operation. This thesis describes the model concepts, the model implementation and the model verification procedures used during development. It also describes the techniques which are used during system optimization. The software, which is written in FORTRAN, is structured in modular units to provide logical and efficient programming. These modular units may also be used in the modelling and optimization of other photovoltaic systems

The advantages and cost effectiveness of database improvement methods

Relational databases have proved inadequate for supporting new classes of applications, and as a consequence, a number of new approaches have been taken (Blaha 1998), (Harrington 2000). The most salient alternatives are denormalisation and conversion to an object-oriented database (Douglas 1997). Denormalisation can provide better performance but has deficiencies with respect to data modelling. Object-oriented databases can provide increased performance efficiency but without the deficiencies in data modelling (Blaha 2000). Although there have been various benchmark tests reported, none of these tests have compared normalised, object oriented and de-normalised databases. This research shows that a non-normalised database for data containing type code complexity would be normalised in the process of conversion to an objectoriented database. This helps to correct badly organised data and so gives the performance benefits of de-normalisation while improving data modelling. The costs of conversion from relational databases to object oriented databases were also examined. Costs were based on published benchmark tests, a benchmark carried out during this study and case studies. The benchmark tests were based on an engineering database benchmark. Engineering problems such as computer-aided design and manufacturing have much to gain from conversion to object-oriented databases. Costs were calculated for coding and development, and also for operation. It was found that conversion to an object-oriented database was not usually cost effective as many of the performance benefits could be achieved by the far cheaper process of de-normalisation, or by using the performance improving facilities provided by many relational database systems such as indexing or partitioning or by simply upgrading the system hardware. It is concluded therefore that while object oriented databases are a better alternative for databases built from scratch, the conversion of a legacy relational database to an object oriented database is not necessarily cost effective

A unified model of the electrical power network

Traditionally, the different infrastructure layers, technologies and management activities associated with the design, control and protection operation of the Electrical Power Systems have been supported by numerous independent models of the real world network. As a result of increasing competition in this sector, however, the integration of technologies in the network and the coordination of complex management processes have become of vital importance for all electrical power companies. The aim of the research outlined in this paper is to develop a single network model which will unify the generation, transmission and distribution infrastructure layers and the various alternative implementation technologies. This 'unified model' approach can support ,for example, network fault, reliability and performance analysis. This paper introduces the basic network structures, describes an object-oriented modelling approach and outlines possible applications of the unified model

Quality-aware model-driven service engineering

Service engineering and service-oriented architecture as an integration and platform technology is a recent approach to software systems integration. Quality aspects ranging from interoperability to maintainability to performance are of central importance for the integration of heterogeneous, distributed service-based systems. Architecture models can substantially influence quality attributes of the implemented software systems. Besides the benefits of explicit architectures on maintainability and reuse, architectural constraints such as styles, reference architectures and architectural patterns can influence observable software properties such as performance. Empirical performance evaluation is a process of measuring and evaluating the performance of implemented software. We present an approach for addressing the quality of services and service-based systems at the model-level in the context of model-driven service engineering. The focus on architecture-level models is a consequence of the black-box character of services

Modelling the integration of BP and IT using business process simulation

Information Technology (IT) and Business Process (BP) communities argues that the use of IT to support business processes can bring a number of benefits to the organisation. Most of these benefits, however, can only be seen after the implementation of such technology. Moreover, there are many cases where the benefits brought by the implementation of IT do not fulfil the organisation’s expectations. One reason of this may happen is because research in BP and IS domains show little indication of which modelling methods, techniques or tools can help organisations to foresee the benefits of the integration of IT with BP. This paper describes the insights gained during a UK funded research project, namely ASSESS-IT, which used simulation techniques to address this problem. Considering IT as a two layered system, namely Information Systems (IS) and Computer Networks (CN), ASSESS-IT aimed to depict the benefits that new IT may bring to the BP. This paper uses the outcomes derived from ASSESS-IT to suggest that, in some cases; the relationship between BP and IT could be better understood by looking at the relationship between BP and IS alone. It then proposes an alternative simulation framework, namely ISBPS, that provides the means to develop simulation models that portray quantifiable metrics of the integration of BP and IS, offering in this way an alternative mechanism that can help BP and IS analyst to foresee the benefits that the insertion of a given IS design may bring to the organisational processes

Compositional Performance Modelling with the TIPPtool

Stochastic process algebras have been proposed as compositional specification formalisms for performance models. In this paper, we describe a tool which aims at realising all beneficial aspects of compositional performance modelling, the TIPPtool. It incorporates methods for compositional specification as well as solution, based on state-of-the-art techniques, and wrapped in a user-friendly graphical front end. Apart from highlighting the general benefits of the tool, we also discuss some lessons learned during development and application of the TIPPtool. A non-trivial model of a real life communication system serves as a case study to illustrate benefits and limitations