1,547 research outputs found
Recognition of Authority in Virtual Organisations
No full textA Virtual Organisation (VO) is a temporary alliance of autonomous, diverse, and geographically dispersed organisations, where the participants pool resources, information and knowledge in order to meet common objectives. This requires dynamic security policy management. We propose an authorisation policy management model called recognition of authority (ROA) which allows dynamically trusted authorities to adjust the authorisation policies for VO resources. The model supports dynamic delegation of authority, and the expansion and contraction of organizations in a VO, so that the underlying authorisation system is able to use existing user credentials issued by participating organisations to evaluate the users access rights to VO resources
Unifying Access and Resource Usage Control over Standard Client-Server Interactions
No full textWe propose a novel framework for integrated access and resource usage control over standard clientserver interactions. Historically, access control has been developed without considering resource usage. Resource control has thus developed as an ad hoc server-centric set of mechanisms (e.g., file system quota, network bandwidth quote, etc.). We believe that resource usage control is strongly related to access control and so should be implemented using a unified, global enforcement framework. We introduce such a framework, where services have resource usage constraints and principals have resource usage histories. To access and use a service, a principal must have the appropriate access and sufficient resource usage rights when considering its usage history. Our framework is able to enforce global stateful policies, yet do not require changes to existing message-passing applications. We have built a prototype and used it to specify and enforce an example policy that includes role-based control and delegation. We applied our system to control access and resource usage for three different services, network, DNS, and SMB file systems, to demonstrate its effectiveness and wide applicability.Technical report DCS-TR-67
The Impact Of The Development Of ICT In Several Hungarian Economic Sectors
No full textAs the author could not find a reassuring mathematical and
statistical method in the literature for studying the effect of
information communication technology on enterprises, the author
suggested a new research and analysis method that he also used to study the Hungarian economic sectors. The question of what
factors have an effect on their net income is vital for enterprises. At first, the author studied some potential indicators related to economic sectors, then those indicators were compared to the net income of the surveyed enterprises. The resulting data showed that the growing penetration of electronic marketplaces contributed to the change of the net income of enterprises to the greatest extent.
Furthermore, among all the potential indicators, it was the only indicator directly influencing the net income of enterprises.
With the help of the compound indicator and the financial data
of the studied economic sectors, the author made an attempt to find a connection between the development level of ICT and
profitability. Profitability and productivity are influenced by a lot of other factors as well. As the effect of the other factors could not be measured, the results – shown in a coordinate system - are not full but informative.
The highest increment of specific Gross Value Added was
produced by the fields of ‘Manufacturing’, ‘Electricity, gas and water supply’, ‘Transport, storage and communication’ and
‘Financial intermediation’. With the exception of ‘Electricity, gas and water supply’, the other economic sectors belong to the group of underdeveloped branches (below 50 percent).
On the other hand, ‘Construction’, ‘Health and social work’ and
‘Hotels and restaurants’ can be seen as laggards, so they got into the lower left part of the coordinate system.
‘Agriculture, hunting and forestry’ can also be classified as a
laggard economic sector, but as the effect of the compound
indicator on the increment of Gross Value Added was less
significant, it can be found in the upper left part of the coordinate system. Drawing a trend line on the points, it can be made clear that it shows a positive gradient, that is, the higher the usage of ICT devices, the higher improvement can be detected in the specific Gross Value Added
Network coded MIMO aided cooperative communications in the ambulance-and-emergency area
No full textIn this contribution, a novel network coding (NC) aided multi-input multi-output (MIMO) scheme is proposed for providing reliable transmission from an ambulance assisting in an emergency situation by cooperating with relaying devices at an emergency scene. Our system is constituted by an Irregular Convolutional Coded Unity Rate Coded Space Time Trellis Coded M-ary Phase Shift Keying (IrCC-URC-STTC-MPSK) scheme invoked for exploiting the benefits of MIMO systems. The system is designed with the aid of Extrinsic Information Transfer (EXIT) charts for approaching the corresponding channel capacity in fast fading environments. The proposed scheme exhibits substantial benefits over conventional MIMO systems in hostile wireless channels
A trust framework for peer-to-peer interaction in ad hoc networks
No full textPhDAs a wider public is increasingly adopting mobile devices with diverse applications,
the idea of who to trust while on the move becomes a crucial one. The need to find
dependable partners to interact is further exacerbated in situations where one finds
oneself out of the range of backbone structures such as wireless base stations or
cellular networks. One solution is to generate self-started networks, a variant of
which is the ad hoc network that promotes peer-to-peer networking. The work in
this thesis is aimed at defining a framework for such an ad hoc network that provides
ways for participants to distinguish and collaborate with their most trustworthy
neighbours.
In this framework, entities create the ability to generate trust information by directly
observing the behaviour of their peers. Such trust information is also shared in order
to assist those entities in situations where prior interactions with their target peers
may not have existed.
The key novelty points of the framework focus on aggregating the trust evaluation
process around the most trustworthy nodes thereby creating a hierarchy of nodes that
are distinguished by the class, defined by cluster heads, to which they belong.
Furthermore, the impact of such a framework in generating additional overheads for
the network is minimised through the use of clusters. By design, the framework also
houses a rule-based mechanism to thwart misbehaving behaviour or non-cooperation.
Key performance indicators are also defined within this work that allow a framework
to be quickly analysed through snapshot data, a concept analogous to those used
within financial circles when assessing companies. This is also a novel point that
may provide the basis for directly comparing models with different underlying
technologies.
The end result is a trust framework that fully meets the basic requirements for a
sustainable model of trust that can be developed onto an ad hoc network and that
provides enhancements in efficiency (using clustering) and trust performance
Annamocalamus kontumensis H. N. Nguyen, N., spec. nova
No full text<i>Annamocalamus kontumensis</i> H. N. Nguyen, N.-H. Xia & V. T. Tran, spec. nova (Fig. 1, 2). <p> <b>Typus: Vietnam, Kon Tum Province:</b> Ngoc Linh Mountain, Ngoc Linh village, c. 1200 m, 23.II.1995, fl. & fr., <i>Averyanov & al. VH020</i> (holo-: P [P00451097]).</p> <p> <i>Rhizomatis sympodialibus, rhizomemate brevi collo, culmi erectus, vaginis auriculis conspicuis, dorso dense adpresseque atro-strigosis, laminis triangularis, erectus, basis producens, deciduus, inflorrescentilis iterauctantilus, pseudospiculae ad convivia in foliis nodorum distal ramis florentibus, glumis 3, flosculis hermaphroditus 1, lodicula 3, stylus longis, stigmatibus 3, brevis, frutus carnosus.</i></p> <p> <i>Densely tufted</i> with rhizomes short necked, pachymorph. <i>Culms</i> erect, 4-8 m tall; internodes 60-80 cm long and 3- 4.5 cm in diameter, when young densely covered with appressed white hairs, becoming rough when old due to silica; culms walls 2-3 mm thick; nodes slight swollen. <i>Branches</i> a cluster of slender subequal branches, none dominant, these branching further. <i>Culm</i> sheaths persistent, greenish brown, rough, when young covered with densely appressed purplebrown bristle on the abaxial surface; 20-25 cm long and 12- 16 cm wide at the base; apex 8-10 cm wide, margins dense purple-brown hairs; blade tardily deciduous, triangular, erected, base black-brown when young and produced upwards into rounded, 10-15 × 6-8 cm, abaxial dense white powder, margins dense cilia, adaxilly dense hairs at the base; one auricle standing, 2-2.5 × 0.4-0.6 cm, other one margin curved downwards, 1.5-2 × 0.4-0.5 cm, adaxilly dense purple-brown bristle, ca. 0.9 cm long; ligule ca. 0.3 cm long with dense paleciliate, ca. 0.3 cm long. <i>Leaf</i> blades oblong-obovate, base broadly cuneate, 30-34 × 3.5-4 cm, veins in 13-14 pairs, margins and adaxilly surface dense white cilia; leaf sheaths dense white cilia, auricles ca. 0.3 ×c a. 0.2 cm with slender bristles, 5-8 mm long; ligule low rim, ca. 1mm; petiole 4-5 × 2-3 mm. <i>Pseudospikelets</i> in groups at the distal nodes on leafless flowering branches, ca. 8 mm long; 1 fertile floret, glumes 3, upper most obovate, 4-5 × 2-3 mm, apex acute, mucronate, mucro ca. 1 mm long, veins in 5, margins short white-hispid, abaxial surface sparse white cilia; lemma oblong-lanceolate, 5-6 × 3-4 mm, veins in 9-11, apex acute, mucronate, mucro 1.5- 2 mm long, convolute and covering most of the palea, margins dense white cilia; palea oblong-lanceolate, 7-8 × 2.5-3 mm, veins in 9-11, strongly involutes, sparse white cilia, apex bifid ca. 1 mm long, with a narrow groove on the back (at the base rachilla is joined); lodicules 3, obovate-shaped, 0.7-1 × ca. 0.5 mm margins long cilia; stamens 6, filaments free, 4-5 × 0.4-0.5 mm; style long; stigmas 3, plumose; ovary glabrous, short stalked. <i>Pericarp</i> thick, apple shaped, fleshy, globose, top horizontal or slightly truncated in the middle, 12-15 × 12- 15 mm.</p> <p> <i>Distribution and habitat.</i> – The new species grows in the degraded natural forest in valleys and mountain gorges, but is common along river or valleys, between 500 to 1200 m in the western highland of Vietnam.</p> <p> <i>Phenology. – Annamocalamus kontumensis</i> flowered in December 1946 <i>(Poilane 35696)</i> and January 1995 <i>(Averyanov & al.VH020).</i> New shoots seems to develop between June to August.</p> <p> <i>Local uses.</i> – This species is of considerable importance to the local people. Its culms are used for making handicrafts, household tools.</p> <p> <i>Etymology.</i> – The specific epithet refers to the type locality, Kon Tum Province, Vietnam.</p> <p> <i>Paratypi.</i> – <b>VIETNAM. Kon Tum Province:</b> Dak To District, Lo Xo Pass, 15°13’338’’N 107°44’052’’E, 1071 m, 28.VIII.2005, st., <i>H. N. Nguyen</i>, V. T. <i>Tran</i> 2820050540 (FSIV); Dak To and Dak Blan District, 1.IX.1946, fl. & fr., <i>Poilane 35696</i> (P).</p>Published as part of <i>Tran, Van Tien, Nguyen, Hoang Nghia & Xia, Nian-He, 2013, Annamocalamus H. N. Nguyen, N. - H. Xia & V. T. Tran, a new genus of bamboo (Poaceae) from Vietnam, pp. 159-165 in Candollea 68 (1)</i> on page 161, DOI: 10.15553/c2013v681a23, <a href="http://zenodo.org/record/5747054">http://zenodo.org/record/5747054</a>
MANETs: Internet Connectivity and Transport Protocols
No full textA Mobile Ad hoc Network (MANET) is a collection of mobile nodes connected together over a wireless medium, which self-organize into an autonomous multi-hop wireless network. This kind of networks allows people and devices to seamlessly internetwork in areas with no pre-existing communication infrastructure, e.g., disaster recovery environments. Ad hoc networking is not a new concept, having been around in various forms for over 20 years. However, in the past only tactical networks followed the ad hoc networking paradigm. Recently, the introduction of new technologies such as IEEE 802.11, are moved the application field of MANETs to a more commercial field. These evolutions have been generating a renewed and growing interest in the research and development of MANETs.
It is widely recognized that a prerequisite for the commercial penetration of the ad hoc networking technologies is the integration with existing wired/wireless infrastructure-based networks to provide an easy and transparent access to the Internet and its services. However, most of the existing solutions for enabling the interconnection between MANETs and the Internet are based on complex and inefficient mechanisms, as Mobile-IP and IP tunnelling. This thesis describes an alternative approach to build multi-hop and heterogeneous proactive ad hoc networks, which can be used as flexible and low-cost extensions of traditional wired LANs. The proposed architecture provides transparent global Internet connectivity and address autocofiguration capabilities to mobile nodes without requiring configuration changes in the pre-existing wired LAN, and relying on basic layer-2 functionalities. This thesis also includes an experimental evaluation of the proposed architecture and a comparison between this architecture with a well-known alternative NAT-based solution. The experimental outcomes confirm that the proposed technique ensures higher per-connection throughputs than the NAT-based solution.
This thesis also examines the problems encountered by TCP over multi-hop ad hoc networks. Research on efficient transport protocols for ad hoc networks is one of the most active topics in the MANET community. Such a great interest is basically motivated by numerous observations showing that, in general, TCP is not able to efficiently deal with the unstable and very dynamic environment provided by multi-hop ad hoc networks. This is because some assumptions, in TCP design, are clearly inspired by the characteristics of wired networks dominant at the time when it was conceived. More specifically, TCP implicitly assumes that packet loss is almost always due to congestion phenomena causing buffer overflows at intermediate routers. Furthermore, it also assumes that nodes are static (i.e., they do not change their position over time). Unfortunately, these assumptions do not hold in MANETs, since in this kind of networks packet losses due to interference and link-layer contentions are largely predominant, and nodes may be mobile. The typical approach to solve these problems is patching TCP to fix its inefficiencies while preserving compatibility with the original protocol. This thesis explores a different approach. Specifically, this thesis presents a new transport protocol (TPA) designed from scratch, and address TCP interoperability at a late design stage. In this way, TPA can include all desired features in a neat and coherent way. This thesis also includes an experimental, as well as, a simulative evaluation of TPA, and a comparison between TCP and TPA performance (in terms of throughput, number of unnecessary transmissions and fairness). The presented analysis considers several of possible configurations of the protocols parameters, different routing protocols, and various networking scenarios. In all the cases taken into consideration TPA significantly outperforms TCP
Text-based content search and retrieval in ad hoc P2P communities
No full textWe consider the problem of content search and retrieval in peer-to-peer (P2P) communities. P2P computing is a potentially powerful model for information sharing between ad hoc groups of users because of its low cost of entry and natural model for resource scaling with community size. As P2P communities grow in size, however, locating information distributed across the large number of peers becomes problematic. We present a distributed text-based content search and retrieval algorithm to address this problem. Our algorithm is based on a state-of-the-art text-based document ranking algorithm: the vector-space model, instantiated with the TFxIDF ranking rule. A naive application of TFxIDF would require each peer in a community to collect an inverted index of the entire community. This is costly both in terms of bandwidth and storage. Instead, we show how TFxIDF can be approximated given compact summaries of peers’ local inverted indexes. We make three contributions: (a) we show how the TFxIDF rule can be adapted to use the index summaries, (b) we provide a heuristic for adaptively determining the set of peers that should be contacted for a query, and (c) we show that our algorithm tracks TFxIDF’s performance very closely, regardless of how documents are distributed throughout the community. Furthermore, our algorithm preserves the main flavor of TFxIDF by retrieving close to the same set of documents for any given query.Technical report DCS-TR-48
High diagnostic yield of tuberculosis from screening urine samples from HIV-infected patients with advanced immunodeficiency using the Xpert MTB/RIF assay.
No full text: ABSTRACT:: We determined the diagnostic yield of the Xpert MTB/RIF assay for tuberculosis (TB) when testing small volumes of urine from ambulatory HIV-infected patients prior to starting antiretroviral therapy (ART) in South Africa. Compared to a gold standard of sputum culture, the sensitivity of urine Xpert among those with CD4 cell counts of <50, 50-100 and >100 cells/?L were 44.4%, 25.0% and 2.7% (P=0.001), respectively. Urine Xpert testing provides a means of rapid TB diagnosis in patients with advanced immunodeficiency and poor prognosis. These data are indicative of high rates of TB dissemination and renal involvement in this clinical population
How Should Tobacco Be Taxed in EU-Accession Countries?
No full textTen Central and Eastern European countries, as well as Cyprus and Malta, have applied for membership of the European Union. Membership involves, among others, alignment of the taxes on tobacco products. Within the acquis communautaire, accession countries can choose between a predominantly specific and a predominantly ad valorem excise regime. The choice affectsrevenue, tobacco consumption control, and EU competition. Thispaper examines the arguments and concludes that a predominantlyspecific regime seems to be the preferred choice.
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