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121.
Alexandros G. Fragkiadakis Vasilios A. Siris Nikolaos E. Petroulakis Apostolos P. Traganitis 《Wireless Communications and Mobile Computing》2015,15(2):276-294
We present intrusion detection algorithms to detect physical layer jamming attacks in wireless networks. We compare the performance of local algorithms on the basis of the signal‐to‐interference‐plus‐noise ratio (SINR) executing independently at several monitors, with a collaborative detection algorithm that fuses the outputs provided by these algorithms. The local algorithms fall into two categories: simple threshold that raise an alarm if the output of the SINR‐based metrics we consider deviates from a predefined detection threshold and cumulative sum (cusum) algorithms that raise an alarm if the aggregated output exceeds the predefined threshold. For collaborative detection, we use the Dempster–Shafer theory of evidence algorithm. We collect SINR traces from a real IEEE 802.11 network, and with the use of a new evaluation method, we evaluate both the local and the Dempster–Shafer algorithms in terms of the detection probability, false alarm rate, and their robustness to different detection threshold values, under different attack intensities. The evaluation shows that the cusums achieve higher performance than the simple threshold algorithms under all attack intensities. The Dempster–Shafer algorithm when combined with the simple algorithms, it can increase their performance by more than 80%, but for the cusum algorithms it does not substantially improve their already high performance.Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
122.
Christos Bouras Chryssi Chantzi Vaggelis Kapoulas Alexandros Panagopoulos Ioanna Sampraku Afrodite Sevasti 《International Journal of Communication Systems》2003,16(2):151-169
In our days, efficient management of the available network resources becomes a critical issue, both from a functional point of view (so that users can be provided with the bandwidth they need), and an economical point of view (so that carriers can satisfactorily and efficiently serve as many customers as possible and at the same time increase their revenue). In this paper we consider a bandwidth control scheme (i.e. managed bandwidth service) for an ATM network infrastructure which is applied to the Greek research and technology network (GRNET). We present some methods that we have tested (in a simulation setting) in order to increase the efficiency of the system and the utilization of the available bandwidth. More specifically, we consider a bandwidth‐resizing algorithm for virtual paths, in order to keep the allocated bandwidth very close to the bandwidth actually used. This leads to an increased number of accepted requests and better network utilization. We, also, use the simulation results in order to get an estimation of the effective bandwidth for VBR paths that can be used in call admission. Finally, we consider a semi‐offline scheme where requests are gathered and considered for acceptance in regular intervals. Simulation results show an increase in the utilization of resources. As a further improvement, we allow connections to be allocated a little before or after the time initially requested. This leads to further improvement in network utilization. All the improvement schemes were tested with the ATM‐TN simulator and the results look promising. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
123.
Nikos Passas Sarantis Paskalis Alexandros Kaloxylos Faouzi Bader Renato Narcisi Evangelos Tsontsis Adil S. Jahan Hamid Aghvami Mirtín O'Droma Ivan Ganchev 《Wireless Communications and Mobile Computing》2006,6(4):523-540
‘Always Best Connected’ (ABC) is considered one of the main requirements for next generation networks. The ABC concept allows a person to have access to applications using the devices and network technologies that best suits his or her needs or profile at any time. Clearly, this requires the combination of a set of existing and new technologies, at all levels of the protocol stack, into one integrated system. In this paper, a considerable set of the technologies, that are expected to play a key role towards the ABC vision, are presented. Starting from a reference architecture, the paper describes the required enhancements at certain levels of a traditional protocol stack, as well as technologies for mobility and end‐to‐end Quality of Service (QoS) support. The paper concludes with a case study that reveals the advantages of the ABC concept. This article replaces a previously published version (Wireless Communications and Mobile Computing; 5 (2): 175‐191. [DOI: 10.1002/wcm.207]). Retraction notice DOI: 10.1002/wcm.426 . Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
124.
Anna Tampoukou Alexandros Koutsouris Angeliki T. Paraskevopoulou 《Landscape Research》2013,38(5):610-620
The potential of Botanic Gardens (BGs) to contribute to environmental education is well documented. To what degree this potential is met concerning school students’ environmental education is to be considered. In Greece, Environmental Education Centres (EECs) develop Environmental Education Programmes (EEPs) for schools to implement. A questionnaire survey addressing teachers employed at the EECs in Greece investigated the use of BGs as a means of environmental education and identified their most important features in supporting school EEPs. Findings indicated that the majority of EEC teachers (90.6%) have not developed EEPs involving the use of BGs, although BGs were ranked as most suitable amongst other green spaces for conducting such programmes, particularly for primary school students. Teachers identified the need for BGs to be designed accordingly and provide the necessary infrastructure to be educationally effective that included facilitating teaching (e.g. open spaces, areas to congregate, easy access paths and indoor facilities) and plant-orientated elements as well as plant management displays. A strategy by BGs to promote their role in environmental education and a multidisciplinary design approach would maximise student benefit. 相似文献
125.
Water Resources Management - In regulated industries it is important to identify appropriate performance benchmarks to incentivize companies’ performance. This study applies a stochastic... 相似文献
126.
127.
Evgeny Senokos;Heather Au;Enis Oğuzhan Eren;Tim Horner;Zihan Song;Nadezda V. Tarakina;Elif Begüm Yılmaz;Alexandros Vasileiadis;Hannes Zschiesche;Markus Antonietti;Paolo Giusto; 《Small (Weinheim an der Bergstrasse, Germany)》2024,20(51):2407300
Nanoconfinement is a promising strategy in chemistry enabling increased reaction rates, enhanced selectivity, and stabilized reactive species. Sulfur's abundance and highly reversible two-electron transfer mechanism have fueled research on sulfur-based electrochemical energy storage. However, the formation of soluble polysulfides, poor reaction kinetics, and low sulfur utilization are current bottlenecks for broader practical application. Herein, a novel strategy is proposed to confine sulfur species in a nanostructured hybrid sulfur-carbon material. A microporous sulfur-rich carbon is produced from sustainable natural precursors via inverse vulcanization and condensation. The material exhibits a unique structure with sulfur anchored to the conductive carbon matrix and physically confined in ultra-micropores. The structure promotes Na+ ion transport through micropores and electron transport through the carbon matrix, while effectively immobilizing sulfur species in the nanoconfined environment, fostering a quasi-solid-state redox reaction with sodium. This translates to ≈99% utilization of the 2e− reduction of sulfur and the highest reported capacity for a room temperature Na−S electrochemical system, with high rate capability, coulombic efficiency, and long-term stability. This study offers an innovative approach toward understanding the key physicochemical properties of sulfurcarbon nanohybrid materials, enabling the development of high-performance cathode materials for room-temperature Na-S batteries with efficient sulfur utilization. 相似文献
128.
ABSTRACTEstimating productivity change and its determinants is of great importance when measuring the performance of a firm. A true random effect cost model was employed to measure the cost efficiency of water companies in England and Wales from 1993 to 2016. Subsequently, total factor productivity change was estimated and decomposed into cost-efficiency change, technical change, scale efficiency change, output effect and residual price effect. The results indicate that the English and Welsh water industry increased its productivity over the period examined at a rate of about 2.1%, and it was influenced primarily by technical change. The price reviews appear to have a positive impact on the productivity of water-only companies during the whole period examined. In the case of water and sewerage companies, the 1994 and 1999 price reviews had a positive impact on productivity, whereas the last two price reviews had an adverse impact. 相似文献
129.
130.
Iason Psilopatis Alexandros Pergaris Kleio Vrettou Gerasimos Tsourouflis Stamatios Theocharis 《International journal of molecular sciences》2022,23(6)
Gynecological cancers represent some of the most common types of malignancy worldwide. Erythropoietin-producing hepatocellular receptors (EPHs) comprise the largest subfamily of receptor tyrosine kinases, binding membrane-bound proteins called ephrins. EPHs/ephrins exhibit widespread expression in different cell types, playing an important role in carcinogenesis. The aim of the current review was to examine the dysregulation of the EPH/ephrin system in gynecological cancer, clarifying its role in ovarian, endometrial, and cervical carcinogenesis. In order to identify relevant studies, a literature review was conducted using the MEDLINE and LIVIVO databases. The search terms ephrin, ephrin receptor, ovarian cancer, endometrial cancer, and cervical cancer were employed and we were able to identify 57 studies focused on gynecological cancer and published between 2001 and 2021. All researched ephrins seemed to be upregulated in gynecological cancer, whereas EPHs showed either significant overexpression or extensive loss of expression in gynecological tumors, depending on the particular receptor. EPHA2, the most extensively studied EPH in ovarian cancer, exhibited overexpression both in ovarian carcinoma cell lines and patient tissue samples, while EPHB4 was found to be upregulated in endometrial cancer in a series of studies. EPHs/ephrins were shown to exert their role in different stages of gynecological cancer and to influence various clinicopathological parameters. The analysis of patients’ gynecological cancer tissue samples, most importantly, revealed the significant role of the EPH/ephrin system in the development and progression of gynecological cancer, as well as overall patient survival. In conclusion, the EPH/ephrin system represents a large family of biomolecules with promising applications in the fields of diagnosis, prognosis, disease monitoring, and treatment of gynecological cancer, with an established important clinical impact. 相似文献