Performance Modelling and Optimisation of Multi-hop Networks

A major challenge in the design of large-scale networks is to predict and optimise the total time and energy consumption required to deliver a packet from a source node to a destination node. Examples of such complex networks include wireless ad hoc and sensor networks which need to deal with the effects of node mobility, routing inaccuracies, higher packet loss rates, limited or time-varying effective bandwidth, energy constraints, and the computational limitations of the nodes. They also include more reliable communication environments, such as wired networks, that are susceptible to random failures, security threats and malicious behaviours which compromise their quality of service (QoS) guarantees. In such networks, packets traverse a number of hops that cannot be determined in advance and encounter non-homogeneous network conditions that have been largely ignored in the literature. This thesis examines analytical properties of packet travel in large networks and investigates the implications of some packet coding techniques on both QoS and resource utilisation. Specifically, we use a mixed jump and diffusion model to represent packet traversal through large networks. The model accounts for network non-homogeneity regarding routing and the loss rate that a packet experiences as it passes successive segments of a source to destination route. A mixed analytical-numerical method is developed to compute the average packet travel time and the energy it consumes. The model is able to capture the effects of increased loss rate in areas remote from the source and destination, variable rate of advancement towards destination over the route, as well as of defending against malicious packets within a certain distance from the destination. We then consider sending multiple coded packets that follow independent paths to the destination node so as to mitigate the effects of losses and routing inaccuracies. We study a homogeneous medium and obtain the time-dependent properties of the packet’s travel process, allowing us to compare the merits and limitations of coding, both in terms of delivery times and energy efficiency. Finally, we propose models that can assist in the analysis and optimisation of the performance of inter-flow network coding (NC). We analyse two queueing models for a router that carries out NC, in addition to its standard packet routing function. The approach is extended to the study of multiple hops, which leads to an optimisation problem that characterises the optimal time that packets should be held back in a router, waiting for coding opportunities to arise, so that the total packet end-to-end delay is minimised

The status of the University of Khartoum institutional repository

The paper explored the current status of the University of Khartoum institutional repository (Khartoumspace) and attempted to answer questions pertaining to the contents of the repository and how they are organized, its staff and workflow, and how data is managed within the repository in addition to deposit and access policies adopted, and copyright and support issues. The study adopted a descriptive approach and used the case study method. Data collection tools included a semi-structured interview, document analysis, and observation. The study found that graduate theses and dissertations constitute the largest collection in the repository and that there is a high degree of institutional support for the repository. The paper also revealed that a mandatory deposit policy has been introduced by the University of Khartoum administration to enrich the repository with staff publications, but there is a need for more advocacy and awareness raising programmes targeting the University academic community, and like other institutional repositories in Africa, the Khartoumspace faces a number of challenges that might hinder its development which need to be addressed by the University administration

Regional Integration in Africa: Bridging the North-Sub-Saharan Divide

Regional Integration in Africa Bridging the North-Sub-Saharan Divide came about as a research project conducted by the Africa Institute of South Africa and examines the North African countries\u27 strategies of involvement in the African continent, and their integration initiatives. The book looks at major issues involving Egypt, Libya, Tunisia, Algeria, Morocco and Mauritania. These countries, in most cases, have been treated as separate from sub-Saharan Africa. However, the historical reality and economic and political interests indicate that the North African countries have been and still are closely connected with the rest of the African continent. Egypt, for example, was one of the leading countries in the African unity movement, and, together with Libya, has contributed to the restructuring of the African continental organisation and the establishment of the African Union. The book consists of two parts. The first part includes five chapters written in English, the second part of the book comprises six chapters written in Arabic. © Africa Institute of South Africa 2011

Fast Approximate Time-Delay Estimation in Ultrasound Elastography Using Principal Component Analysis

Time delay estimation (TDE) is a critical and challenging step in all ultrasound elastography methods. A growing number of TDE techniques require an approximate but robust and fast method to initialize solving for TDE. Herein, we present a fast method for calculating an approximate TDE between two radio frequency (RF) frames of ultrasound. Although this approximate TDE can be useful for several algorithms, we focus on GLobal Ultrasound Elastography (GLUE), which currently relies on Dynamic Programming (DP) to provide this approximate TDE. We exploit Principal Component Analysis (PCA) to find the general modes of deformation in quasi-static elastography, and therefore call our method PCA-GLUE. PCA-GLUE is a data-driven approach that learns a set of TDE principal components from a training database in real experiments. In the test phase, TDE is approximated as a weighted sum of these principal components. Our algorithm robustly estimates the weights from sparse feature matches, then passes the resulting displacement field to GLUE as initial estimates to perform a more accurate displacement estimation. PCA-GLUE is more than ten times faster than DP in estimation of the initial displacement field and yields similar results.Comment: Accepted to be Published in 2019, 41th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), Berlin, German

Investigating the Role of Medical Terms Translation in Facilitating Learning Process for Medical Students

This paper aims to answer “To what extent Medical Terms Translation can help in Facilitating Learning Process for Medical Students?” The researcher has adopted the quantitative method as well as the questionnaire as a tool for collecting data relevant to the study to bring to the light the importance of Medical Terms Translation in Facilitating Learning Process for students who study Medical Sciences. The sample of this study comprises (60) students. The marks obtained from the questionnaire were compared. From one hand, the results have revealed that the students encountered difficulties in   understanding the Medical Terms. The result has shown that the questionnaire significance indicates that there is highly difference among students.  Therefore, this indicates that Medical Terms Translation can play great role in Facilitating Learning Process for Students who study Medical Sciences

Investigating the Role of English Language as International Medium for Learning Medical Sciences

This paper aims to answer “To what extent English Language as International Medium can help for Learning Medical Sciences?" The researcher has adopted the quantitative method as well as the questionnaire as a tool for collecting data relevant to the study to bring to the light the importance of English Language as International Medium for Learning Medical Sciences. The sample of this study comprises (60) students. The marks obtained from the questionnaire were compared. From one hand, the results have revealed that the students encountered difficulties in   understanding the Medical Sciences. The result has shown that the questionnaire significance indicates that there is highly difference among students.  Therefore, this indicates that English Language as International Medium can play a great role for Learning Medical Sciences

A New Email Retrieval Ranking Approach

Email Retrieval task has recently taken much attention to help the user retrieve the email(s) related to the submitted query. Up to our knowledge, existing email retrieval ranking approaches sort the retrieved emails based on some heuristic rules, which are either search clues or some predefined user criteria rooted in email fields. Unfortunately, the user usually does not know the effective rule that acquires best ranking related to his query. This paper presents a new email retrieval ranking approach to tackle this problem. It ranks the retrieved emails based on a scoring function that depends on crucial email fields, namely subject, content, and sender. The paper also proposes an architecture to allow every user in a network/group of users to be able, if permissible, to know the most important network senders who are interested in his submitted query words. The experimental evaluation on Enron corpus prove that our approach outperforms known email retrieval ranking approachesComment: 20 page

Realisierungsformen der Sprechereinstellung in der deutschen Wissenschaftskommunikation - Versuch einer Klassifikation

Die Klasse der Sprechereinstellung gilt als eine heterogene Klasse, die sprachlich durch diverse Ausdrucksformen realisiert wird. Trotz der Heterogenität der Realisierungsformen werden dieser Klasse keine Arbeiten zur Differenzierung zwischen den einzelnen Formen gewidmet. Die Sprechereinstellung ist der Modalität zuzuordnen. In der Literatur gibt es jedoch verschiedene semantisch-logische Typologien für die Modalität, nämlich subjektive und objektive Modalität (Helbig/Buscha 1996, S. 131 f.), epistemische und nicht-epistemische Modalität (Duden 2005, S. 562 ff.), logische, psychologische und soziale Modalität (Gabelentz 1891, S. 495 ff.) und kognitive, volitive und emotive Modalität (Bublitz 1978, S. 6 f.) Redder (2009, S. 88 ff.) macht einen Vorschlag zur Unterscheidung zwischen drei handlungstheoretischen Arten der Modalität, die die kommunikative Qualität der Modalität in den Vordergrund rücken. Diese Arten sind Handlungsmodalität, Wirklichkeitsmodalität und Wissensmodalität. In diesem Klassifizierungsversuch sind die Realisierungsformen der Sprechereinstellung unter der Wissensmodalität zu finden. Auf dieser Basis wird in der vorliegenden Arbeit versucht, eine wissensbezogene Klassifikation der variablen Realisierungsformen der Sprechereinstellung aus funktional-pragmatischer Sicht in einer konkreten Textart zu erstellen, nämlich im wissenschaftlichen Text. Parallel zur Klassifizierung lässt sich ebenso die Handlungsqualität der Sprechereinstellung darin ermitteln

Overview of the Principles and Practices of Open Access Publishing

This chapter provides an overview of the principles and practices of open access (OA) publishing. It discusses various aspects of this emerging mode of scholarly publishing, including the definition of Open Access and its different types and models in addition to its growth and impact. The chapter also highlights the implications of open access publishing on copyright issues and how creative commons licenses are used to deal with this issue. The main focus of the chapter is to outline and discuss the different advantages and benefits of open access publishing, refuting a number of myths and misconceptions about OA publishing, and to highlight how authors and researchers can benefit from publishing their intellectual works in an open access channel. The chapter adopts the literature review as a methodology and a tool of data collection