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Databases form the common component of many software systems, including mission critical transaction processing systems and multi-tier Internet applications. There is a large body of research in the performance of database management system components, while studies of overall database system performance have been limited. Moreover, performance models specifically targeted at the database design have not been extensively studied. This thesis attempts to address this concern by proposing a performance evaluation method for database designs based on queueing network models. The method is targeted at designs of large databases in which I/O is the dominant cost factor. The database design queueing network performance model is suitable in providing what if comparisons of database designs before database system implementation. A formal specification that captures the essential database design features while keeping the performance model sufficiently simple is presented. Furthermore, the simplicity of the modelling algorithms permits the direct mapping between database design entities and queueing network models. This affords for a more applicable performance model that provides relevant feedback to database designers and can be straightforwardly integrated into early database design development phases. The accuracy of the modelling technique is validated by modelling an open source implementation of the TPC-C benchmark. The contribution of this thesis is considered to be significant in that the majority of performance evaluation models for database systems target capacity planning or overall system properties, with limited work in detailed database transaction processing and behaviour. In addition, this work is deemed to be an improvement over previous methodologies in that the transaction is modelled at a finer granularity, and that the database design queueing network model provides for the explicit representation of active database rules and referential integrity constraints.

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Thesis (M.B.A.)--University of Hong Kong, 1983.

No description available.

Increased availability of natural gas has boosted research and development efforts to further increase gas turbine performance. Performance has been increased remarkably and unit cost reduced due to achievements gained in improving thermodynamic cycles and cooling technologies. However, increased complexity in power industry regulations and fluctuations in fuel price have indicated that all the aforementioned improvements in gas turbine performance could not cope with the increased competition in the gas turbine industrial market. Innovation within the aero-derivative concept has enabled further significant improvement in the performance of industrial gas turbines. It allows a more beneficial approach than developing new designs of industrial gas turbines owing to reduced designing time and cost. Objectives in this project focus on developing a methodology of design and assessing aeroderivative gas turbine engines derived from a 130-seat aircraft engine. Developed methodology includes techno-economic and environmental assessment, conducted through further developments of models based on Techno-economic and Environmental Risk Assessment (TERA) philosophy, to be applied in further industrial applications. Tools used in this investigation include a significant literature research on the development of aero-derivative gas turbine technologies, including thermodynamic cycles and its land-based applications. Turbomatch is a homebased code developed in Cranfield University, used in calculating design point and predicting off-design performance of parent aero-engine and the aeroderivative engines developed. Excel and FORTRAN code are also used in calculating engine’s design parameters, and creating a model of life estimation Creep. Moreover, FORTRAN code is used for building emission and economic models for power generation and combined heat and power applications. Finally, MATLAP code is used in creating a small model for generating performance TXT files, and running marine integrated models platform. All models needed to develop the methodology have been created, and calculations of an engine’s performance and assessment were conducted based on this developed methodology. Sensible results are generated from the investigated methodology and they show acceptable designs of aero-derivative engines on different thermodynamic cycles. Based on the acceptable level of technology and material thermal barriers, all design and off-design performance limitations of new developed aero-derivative engines have been determined for a wide range of ambient conditions. Techno-economic and environmental assessment performed through implementing the developed aero-derivative engines on power generation and marine applications under different operating scenarios. Results of operating the engines on power generation and marine applications have been investigated and compared. It is observed that engines respond differently when operating under different environmental profiles, depending on the number of units engaged and their thermodynamic cycle as well as mechanical configurations. Also, the selected specific gas turbine engine can be the best economical choice for operating on determined scenario, while it cannot be when operating in different scenarios. Assessment of developed engines on the investigated application shows how the lowest specific cost (small engine size) can constitute important criteria in engine selection.

The performance of financial institutions is significantly influenced by the actions of loan officers. The process by which lending decisions are made is therefore of critical interest to management, shareholders, and regulators alike. Indeed, the drain on bank capital that has often accompanied credit quality problems in the past has encouraged the search for new approaches towards the management of lending and related activities. / This thesis seeks to examine whether existing governance and incentive techniques found in banks are sufficiently comprehensive in guiding loan decision-making. In the context of lending to the corporate sector, the study investigates the endogenous and exogenous influences surrounding the lending role, and assesses the implications for how loan officers are monitored, evaluated, and motivated to act in a financial institution’s best interests. / By first developing an expanded model that conceptualizes the loan offer function, and then grounding this framework within a business cycle context, the study demonstrates the potential for governance and reward systems, that are constant through time, to have variable outcomes/effects. Support for this hypothesis is provided based on publicly available financial market information and other material gathered from private sources. A proposal is then advanced for the development of a management information system that identifies changes in credit standards being applied, thereby enabling banks to benchmark and influence loan officer performance in the context of cyclically changing attitudes to risk and the effects on negotiating power.

The performance of financial institutions is significantly influenced by the actions of loan officers. The process by which lending decisions are made is therefore of critical interest to management, shareholders, and regulators alike. Indeed, the drain on bank capital that has often accompanied credit quality problems in the past has encouraged the search for new approaches towards the management of lending and related activities. / This thesis seeks to examine whether existing governance and incentive techniques found in banks are sufficiently comprehensive in guiding loan decision-making. In the context of lending to the corporate sector, the study investigates the endogenous and exogenous influences surrounding the lending role, and assesses the implications for how loan officers are monitored, evaluated, and motivated to act in a financial institution’s best interests. / By first developing an expanded model that conceptualizes the loan offer function, and then grounding this framework within a business cycle context, the study demonstrates the potential for governance and reward systems, that are constant through time, to have variable outcomes/effects. Support for this hypothesis is provided based on publicly available financial market information and other material gathered from private sources. A proposal is then advanced for the development of a management information system that identifies changes in credit standards being applied, thereby enabling banks to benchmark and influence loan officer performance in the context of cyclically changing attitudes to risk and the effects on negotiating power.

Le secteur du bâtiment est en évolution et se doit de répondre aux problématiques environnementales actuelles aussi bien dans la construction neuve que dans la réhabilitation. La simulation thermique offre le moyen de répondre à cette problématique, mais se limite à une estimation des performances spécifiques aux paramètres qui ont été définis. Ce travail de thèse propose une méthodologie basée sur les puissances de calcul actuelles pour évaluer le comportement du bâtiment sur différentes plages de variation des entrées. Ces variations permettront, en fonction des propriétés qui leur sont attribuées, de rechercher des solutions de réhabilitation ou d'évaluer l'incertitude sur les sorties du modèle thermique. Afin de réaliser cela, des méthodes d'analyse de sensibilité performantes sont utilisées à travers un outil d'analyse spécifiquement développé pour le logiciel de simulation EnergyPlus. Cet outil permet une évaluation quasi automatique du modèle énergétique de bâtiment via : des techniques d'échantillonnage éprouvées LHS et LP-Tau, des techniques d'analyse performante pour un nombre de simulations réduit RBD-FAST et RBD-SOBOL, une gestion avancée des entrées et sorties permettant une évaluation détaillée du bâtiment, quelle que soit sa géométrie. Les techniques d'analyse de sensibilité sont employées pour proposer une vision précise des principales relations présentes au sein du modèle. Pour répondre à la contrainte du coût de calcul, la recherche de solution est réalisée à travers un méta-modèle issu d'une décomposition en polynôme de chaos. Une interface graphique utilise cette approximation du modèle complexe du bâtiment pour proposer de façon instantanée une vision claire du comportement de chaque entrée sur les sorties, ainsi que leurs tendances et les plages de variation idéales afin de choisir des solutions. Il est possible de coupler la recherche de solution à l'analyse d'incertitude afin de proposer des solutions robustes et identifier les principales raisons d'un écart entre simulation et réalité. La méthodologie des travaux de thèse encourage à l'optimisation de la compréhension du modèle plus qu'à la recherche d'une solution particulière.L'objectif de la démarche est de fournir des outils d'analyse afin d'aider l'expert dans la recherche de solution et ainsi de mettre en place des représentations graphiques qui facilitent la compréhension du système bâtiment, pour un gain en transparence et l'intégration de nombreuses contraintes de projet. / The building sector is evolving and has to meet the current environmental issues in both new construction and rehabilitation. The thermal simulation provides the mean to address this problem, but the estimated performance is limited to a specific set of parameters that have been defined. This thesis proposes a methodology based on the increased computing power to assess the building behaviour on different ranges of the inputs variation. Depending on the properties allocated to them, the changes of the variations will allow to seek solutions to restore or to assess the uncertainty in the outputs of the thermal model. To achieve this, effective sensitivity analysis methods are used across an analysis tool specifically developed for the simulation software EnergyPlus. This tool allows an almost automatic evaluation of the energy model building thanks to the proven sampling techniques such as LHS and LP-Tau; the efficient analysis techniques like RBD-FAST and RBD-SOBOL in order to reduce the number of simulations; an advanced management of the inputs and the outputs for a detailed assessment of the building regardless of its geometry. The sensitivity analysis techniques are used to provide an accurate picture of these key relationships within the model. To meet the constraints of the computational cost, the search for a solution is achieved through a metamodel from a Polynomial Chaos Expansion PCE. A GUI uses the approximation of the complex model of the building to provide instantly a clear vision of the behaviour of each entry on the outputs, their trends and their ideal ranges of variation to choose solutions. It is possible to couple the search for a solution to the uncertainty analysis to provide robust solutions and identify the main reason for the gap between simulation and reality. The methodology of the PhD work promotes the optimization of the model understanding more than looking for a specific solution. The purpose of the approach is to provide analytical tools to assist the expert in the search for a solution and so, develop graphical representations that facilitate the understanding of the building system for a gain in transparency and integration of many design constraints.

Current thinking on the best propulsion system for a next-generation supersonic cruising (Mach 2 to Mach 4) aircraft is a mixed-flow turbofan engine with afterburner. This study investigates the performance increase of a turbofan engine through the use of isothermal combustion inside the high-pressure turbine (High-Pressure Turburner, HPTB) as an alternative form of thrust augmentation. A cycle analysis computer program is developed for accurate prediction of the engine performance and a supersonic transport cruising at Mach 2 at 60,000 ft is used to demonstrate the merit of using a turburner. When assuming no increase in turbine cooling flow is needed, the engine with HPTB could provide either 7.7% increase in cruise range or a 41% reduction in engine mass flow when compared to a traditional turbofan engine providing the sane thrust. If the required cooling flow in the turbine is almost doubled, the new engine with HPTB could still provide a 4.6% increase in range or 33% reduction in engine mass flow. In fact, the results also show that the degradation of engine performance because of increased cooling flow in a turburner is less than half of the degradation of engine performance because of increased cooling flow in a regular turbine. Therefore, a turbofan engine with HPTB will still easily out-perform a traditional turbofan when even more cooling than currently assumed is introduced. Closer examination of the simulation results in off-design regimes also shows that the new engine not only satisfies the thrust and efficiency requirement at the design cruise point, but also provides enough thrust and comparable or better efficiency in all other flight regimes such as transonic acceleration and take-off. Another finding is that the off-design bypass ratio of the new engine increases slower than a regular turbofan as the aircraft flies higher and faster. This behavior enables the new engine to maintain higher thrust over a larger flight envelope, crucial in developing faster air-breathing aircraft for the future. As a result, an engine with HPTB provides significant benefit both at the design point and in the off-design regimes, allowing smaller and more efficient engines for supersonic aircraft to be realized. / Ph. D.