Search results for "Computer network"

Do South African townships lack entrepreneurial spirit?

2014

It is often assumed that the black population of South Africa lack entrepreneurial spirit and an entrepreneurial culture. A survey conducted in the Walmer Township in Port Elizabeth explored the entrepreneurial spirit and culture in terms of entrepreneurial activities, perceived start-up barriers, entrepreneurship climate, and general cultural factors relating to entrepreneurship. The sample comprised of 309 black adults living in Walmer Township. The results revealed surprisingly high entrepreneurial activity in the form of informal business ventures. Furthermore, the level of entrepreneurial aspirations turned out to be higher than expected. Many of the township inhabitants regard the tow…

Uncertainty in urban flood damage assessment due to urban drainage modelling and depth-damage curve estimation

2010

Due to the increased occurrence of flooding events in urban areas, many procedures for flood damage quantification have been defined in recent decades. The lack of large databases in most cases is overcome by combining the output of urban drainage models and damage curves linking flooding to expected damage. The application of advanced hydraulic models as diagnostic, design and decision-making support tools has become a standard practice in hydraulic research and application. Flooding damage functions are usually evaluated by a priori estimation of potential damage (based on the value of exposed goods) or by interpolating real damage data (recorded during historical flooding events). Hydrau…

Improved GNSS positioning exploiting a vehicular P2P infrastructure

2010

This paper considers the possibility to exploit external altitude measurements to improve the performance of a Kalman based GNSS receiver. The altitude measurements are provided by means of a peer to peer network, that is supposed to be based on the evolution of the 802.11 standard for the vehicular environment, namely the WAVE (802.11p). The performance of such a system are investigated for different characteristics of the aiding measurement and for a different number and disposals of the aiding peers. The aiding measurement is obtained starting from the altitude measurements that the other peers in the network send to the aided user. The experiments highlight the need for a parameter that…

Control and Estimation of Electrified Vehicles

2015

Impact of Transport Costs on International Trade: The Case of Spanish Ceramic Exports

2003

This paper aims to investigate the determinants of maritime and overland transport costs and the role they play in deterring trade across countries. We estimate a transport cost function using data on maritime and overland transport of the ceramic sector (tiles) obtained from interviews held with Spanish logistics operators. We also study the relationship between transport costs and trade and estimate an import demand model for ceramic products. Additionally, we present a discussion on the sensitivity of trade flows and transportation costs to the existence of back-hauling, special conditions for transport and number of reloads.1 The study of modal transport (overland versus maritime) and i…

CVS: Using VLANs to Counteract the Effect of Topology Changes in Quasi-Static Mesh Access Networks

2006

Mesh networks are candidate to play the role of switched Ethernet LANs over extended areas and with a sensibly higher flexibility. Actually, mesh networks can exploit both Ethernet and wireless technologies, e.g. Wi-Fi and/or free-space optical links, to provide a high degree of redundancy in an access network, and to provide users with powerful means to connect with each other. By using such technologies, the mesh topology remains stable for hours, so that the mesh topology can be considered quasi-static. However, large meshes require a heavy overhead in the network control plane as for the management of end-to-end paths, which can change due to mobility of users and due to occasional fail…

Dynamic QoS management for multimedia real-time transmission in industrial environments

2007

The use of multimedia within industrial applications has become commonplace, targetting improved process monitoring and machine vision. In both cases, the multimedia information is commonly distributed and subject to time constraints that must be met across networks while avoiding untolerable interference over typical control flows. This can be achieved with Constant Bit-Rate (CBR) channels, typically supported by real-time protocols. However, the compressors used to reduce the amount of information to transfer generate Variable Bit-Rate (VBR) patterns. Adapting a VBR source to a CBR channel requires specific care in order to avoid wasting channel bandwidth or dropping video frames. This pa…

An evaluation of switched ethernet and linux traffic control for real-time transmission

2008

Switched Ethernet networks are spreading to industrial environments more are more. The current trend is using them at all levels of a factory, replacing this way field-buses and other industrial networks. Switched Ethernet lacks the drawback of the non-deterministic collision resolution of coax cabling. However there are still some sources of indeterminism, mostly due to contention problems in message queues at switches and network interfaces. These problems can be dealt with using traffic control mechanisms for packet prioritisation and scheduling. These features have been largely inaccessible in Ethernet for a long time but, nowadays, they are widely available in industrial switches and a…

Integration of IEC 61850 MMS and IEEE 802.22 for Smart Grid Communication

2017

The reliability of Smart Grid depends on two-way communication between substation and utility. IEC 61850 is an international standard defined to ensure interoperability between Substation Automation System (SAS). IEC 61850 services are mapped on the Manufacturing Message Specification (MMS) especially for meter data management system. MMS is the OSI protocol that run over TCP/IP or OSI networks to support IEC 61850 services. Presently, the MMS uses Ethernet as the layer 2 protocol. However, for long distance communication in remote areas wireless communication is the prefered mode. The Cognitive Radio based IEEE 802.22 is next generation standard for Wireless Regional Area Network (WRAN) th…

Review of IEEE 802.22 and IEC 61850 for real-time communication in Smart Grid

2015

Real time data communication in Smart Grid is a big challenge due to its vastness and complexities. Wireless Regional Area Network (WRAN) - IEEE 802.22 permits opportunistic use of television white space (TVWS) by secondary user, if it is not being utilized by primary user. This standard has the potential to transfer big data of smart grid in real time to control center. The IEC 61850 is the standard for electrical substation automation that uses TCP/IP for data transfer among different ‘intelligent electronic devices’ (IEDs). IEC 61850 consists of different message types which belong to different performance classes that are mapped to different communication protocols. The different perfor…