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To accommodate the expected growth of the air transport industry, the Air Traffic Management (ATM) system is required to increase its performance in terms of capacity, efficiency and security whilst maintaining adequate levels of safety and reducing the environmental impact of aircraft operations. In addition, there is a urgent need to allow the different actors in the ATM system the flexibility to accommodate their preferences,so that they can better pursue their respective business objectives. To deal effectively with all these challenges, the current trend is to increase the levels of automation and integration in the system. Different ATM modernisation initiatives pursuit the shift towards a Trajectory Base Operations (TBO) environment, where different ATM users (e.g., Air Navigation Service Providers (ANSP), Airlines Operations Center (AOC), pi- lots, controllers, airport authorities) will exchange trajectory-related information in order to collaboratively make decisions in an e±ficient and fair way. An increasing number of Decision Support Tools (DSTs) are being developed and implemented to enhance both airborne and ground-based automation systems to support the human in TBO. Since these DSTs have to help humans to make decisions in TBO, they must contain the capability to predict trajectories. However, different DSTs will in principle rely on different trajectory predictors (TP), which may produce different, inconsistent trajectories for the same flight. This lack of consistency among predictions is seen as a key issue for the integration of current and future DSTs. Coordination between TPs is the key to ensure coordination between air-ground, ground -ground and air-air DSTs and hence the successful evolution and application of the TBO concept. This thesis proposes a standard method to describe trajectories that can allow different DSTs to express and exchange their views of the predicted trajectory of an aircraft. This method, called the Aircraft Intent Description Language (AIDL), provides the necessary mechanisms to formulate the aircraft intent. The aircraft intent is defined as the unambiguous description of how the aircraft is to be operated within a certain time frame. Since the mathematical formulation of this concept is needed for the computation of a trajectory, each TP has their own format of aircraft intent. However, the uncoordinated research in trajectory prediction has driven to different models of this aircraft intent,which has precluded its use to coordinate trajectory predictions of different TPs. The use of the AIDL as an standard mean to describe trajectories permits an easy construction and manipulation of trajectories between different TPs. The scope of this thesis is limited to an AIDL that describes airborne operations of civil aircraft, in particular turbofan and turbojet aircraft. However, the methodology exposed in this thesis to obtain the AIDL can be easily applied to ground operations and other type of aircraft and air vehicles (e.g., propellers, helicopters) to extend the scope and applicability of the AIDL. The AIDL is characterised by an alphabet and a grammar. The AIDL grammar contains both lexical and syntactical rules. These rules ensure that the aircraft intent contains the necessary and sufficient information that is needed to compute a trajectory. The development of these rules is based on a rigourous mathematical analysis using Differential Algebraic Equations (DAE) theory. The lexical rules in the AIDL's grammar govern the formulation of the words of the language by combining elements from the AIDL's alphabet. This alphabet contains a set of atomic primitives, equivalent to the letters in the English alphabet, called instructions, which capture basic commands and guidance modes at the disposal of the pilot/FMS to direct the operation of the aircraft in the ATM context. Instructions can be seen as minimal indivisible pieces of information describing distinct ways of closing one of the aircraft motion's degrees of freedom. Mathematically, an instruction is characterised by an equation that is to be satisfied simultaneously with the equations of motion during a certain time interval, denoted as the execution interval of the instructions. The words of the AIDL are called operations. An operation represents an elemental aircraft behaviour that determines its motion unambiguously during a specific time interval denoted as the operation interval. An operation is the result of a set of compatible instructions simultaneously active during the corresponding operation interval. The syntactical rules in the AIDL govern the definition of sentences, which are formed by sequences of operations. These rules allow expressing any possible behaviour that can be elicited from an aircraft in the ATM context. While each DST may have a different input format to describe aircraft intent, the AIDL is designed in such a way that these different inputs can be seen as 'dialects' of the AIDL. Thus, the AIDL can be used as a lingua franca by different the DSTs, which would use it as the common standard to communicate aircraft intent with each other. The possible applications of the AIDL in a TBO environment are manifold. For instance, aircraft intent information expressed using the AIDL could be exchanged as part of a negotiation process between airborne and ground-based automation systems. Air-air synchronisation based on aircraft intent could permit the coordinated operation of Unmanned aerial vehicles (UAVs) by means of exchanging their future behaviour expressed as aircraft intent. Ground-ground aircraft intent sharing would enable a common and efficient treatment of aircraft trajectories in such a way that any amendment could be easily shared between different automation tools.

The outsourcing of IT services is a significant and well-established business activity in service management for many companies worldwide. IT outsourcing has gradually increased in recent times but, although much has been written about this phenomenon, there is little in existing literature that studies the IT outsourcing process in its entirety in the German automotive industry. The objective of this research is to develop a new process model for IT outsourcing in the German automotive industry. The research is exploratory in nature and is based on a qualitative case study methodology. An overarching process model based on nine sub-processes is constructed, reflecting the main stages in IT outsourcing operations, and a number of aspects of each sub-process are researched. Through interview analysis that complements a detailed literature review, the main stakeholders and success factors are established, and key steps and activities are identified. A range of different practical applications in each sub-process are also developed. The outcome of this research provides the basis for a range of analytical materials to complement the existing literature, and these also provide the basis for further research and development. The results and associated applications will also of value to practitioners working in this field.

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published_or_final_version / abstract / toc / Electrical and Electronic Engineering / Master / Master of Philosophy

published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

Wingtip vortices are extremely important phenomena in fluid dynamics for their negative effects in many applications. Despite the many studies on this particular flow, the current understanding is still poor in providing a form base for the design of effective tip geometry modifications and vortex control devices. A rectangular wing with squared and rounded wingtips was tested in order to identify the main mechanisms involved in the formation of the vortex on the wing and in its early development in the wake. The complementarity of a number of experimental techniques adopted, such as surface flow visualizations, wall pressure measurements, smoke visualizations and stereoscopic particle image velocimetry (SPIV), gave a richer insight of the physics and the basic mechanisms of the vortex development. Furthermore, a large number of configurations were tested exploring the effects of several parameters such as wing chord, aspect ratio, wingtip geometry, angle of attack and Reynolds number. The development of the vortex along the wing showed the formation of several secondary vortices which interacted with the primary vortex generating low frequency fluctuations. The structure of the flow at this stage was analysed introducing a compact description through characteristic lines of the vortex system defined from the velocity vector field in the vicinity of the wing surface. The high spatial resolution achieved by the SPIV arrangement allowed a deeper understanding of the vortex structure in the early wake and the turbulence production and dissipation within the vortex core. The relaminarization process of the vortex core promoted by centrifugal motion was observed. The relation between vortex meandering, turbulence, secondary vortices and wake sheet was discussed. A comparison of different methods for the averaging of instantaneous planar vector fields was performed showing the effects and importance of the meandering. An axial acceleration of the flow within the vortex was observed and the formation of different axial flow distributions was discussed. A minimum wake-like flow of 0.62 and a maximum jet-like flow of 1.7 times the freestream velocity were measured and a linear relation between a vortex circulation parameter and the axial velocity peak was found.

No description available.

The ability to communicate over a low bit-rate transmission channel has become the order of the day. In the past, transmitted data over a low bit-rate transmission channel, such as a wireless link, has typically been reserved for speech and data. However, there is currently a great deal of interest being shown in the ability to transmit streaming video over such a link. These transmission channels are generally bandwidth limited hence bit-rates need to be low. Video on the other hand requires large amounts of bandwidth for real-time streaming applications. Existing Video Compression standards such as MPEG-l/2 have succeeded in reducing the bandwidth required for transmission by exploiting redundant video information in both the spatial and temporal domains. However such compression systems are geared towards general applications hence they tend not to be suitable for low bit-rate applications. The objective of this work is to implement such a system. Following an investigation in the field of video compression, existing techniques have been adapted and integrated into an application specific low bit-rate video compression system. The implemented system is application specific as it has been designed to track vehicles of reasonable size within an otherwise static scene. Low bit-rate video is achieved by separating a video scene into two areas of interest, namely the background scene and objects that move with reference to this background. Once the background has been compressed and transmitted to the decoder, the only data that is subsequently transmitted is that that has resulted from the segmentation and tracking of vehicles within the scene. This data is normally small in comparison with that of the background scene and therefore by only updating the background periodically, the resulting average output bit-rate is low. The implemented system is divided into two parts, namely a still image encoder and decoder based on a Variable Block-Size Discrete Cosine Transform, and a context-specific encoder and decoder that tracks vehicles in motion within a video scene. The encoder system has been implemented on the Philips TriMedia TM-1300 digital signal processor (DSP). The encoder is able to capture streaming video, compress individual video frames as well as track objects in motion within a video scene. The decoder on the other hand has been implemented on the host PC in which the TriMedia DSP is plugged. A graphic user interface allows a system operator to control the compression system by configuring various compression variables. For demonstration purposes, the host PC displays the decoded video stream as well as calculated rate metrics such as peak signal to noise ratio and resultant bit-rate. The implementation of the compression system is described whilst incorporating application examples and results. Conclusions are drawn and suggestions for further improvement are offered. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2003.

No description available.