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1.
Passas Nikos Loukas Nikos Merakos Lazaros 《International Journal of Wireless Information Networks》1997,4(1):55-62
Future generation wireless personalcommunication networks (PCN) are expected to providemultimedia capable wireless extensions of fixedATM/B-ISDN. This paper presents a scheduling techniquefor PCN based on TDMA and the leaky bucket regulator, thewell known bandwidth enforcement mechanism for fixedATM. The main objective of the proposed technique is toensure fair and efficient treatment of various types oftraffic on the air interface, includingconstant-bit-rate (CBR) voice and variable-bit-rate(VBR) video. Two alternative priority mechanisms areintroduced and their performance is evaluated. Theperformance comparison of the alternatives reveals aninteresting tradeoff between fairness and quality ofservice (QoS). 相似文献
2.
Vasileios A. Baousis Miltiadis Kyriakakos Stathes Hadjiefthymiades Lazaros Merakos 《Journal of Network and Systems Management》2009,17(4):371-396
The Virtual Home Environment is very important in contemporary mobile telecommunications infrastructure as it caters for the
ubiquitous provision of services irrespective of network, location and user device. The universality of systems like Universal
Mobile Telecommunications System and wi-fi increases the need for the rapid introduction of efficient VHE schemes. In this
paper, we study the adoption of Mobile Agents for handling the VHE functionality. Mobile agents are nicely harmonized with
the broader idea of VHE as they allow the autonomous execution of tasks by components that roam from node to node and network
to network. We present the detailed modeling of a VHE provisioning architecture and investigate its suitability for different
use cases and technical options (e.g., end user devices). The adoption of mobile agents for the ubiquitous provision of telecommunication
services is quite promising in terms of efficiency. Through a series of experiments we quantify the performance benefits stemming
from the adoption of mobile agents in contrast to conventional service provisioning schemes. 相似文献
3.
Alexander Paar Jürgen Reuter John Soldatos Kostas Stamatis Lazaros Polymenakos 《Applied Intelligence》2009,30(1):37-46
Recently, several standards have emerged for ontology markup languages that can be used to formalize all kinds of knowledge.
However, there are no widely accepted standards yet that define APIs to manage ontological data. Processing ontological information
still suffers from the heterogeneity imposed by the plethora of available ontology management systems. Moreover, ubiquitous
computing environments usually comprise software components written in a variety of different programming languages, which
makes it particularly difficult to establish a common ontology management API with programming language agnostic semantics.
We implemented an ontological Knowledge Base Server, which can expose the functionality of arbitrary off-the-shelf ontology
management systems via a formally specified and well defined API. A case study was carried out in order to demonstrate the
feasibility of our approach to use a formally specified ontology management API to implement a registry for ubiquitous computing
systems. 相似文献
4.
Ilias Bougoudis Konstantinos Demertzis Lazaros Iliadis 《Neural computing & applications》2016,27(5):1191-1206
The analysis of air quality and the continuous monitoring of air pollution levels are important subjects of the environmental science and research. This problem actually has real impact in the human health and quality of life. The determination of the conditions which favor high concentration of pollutants and most of all the timely forecast of such cases is really crucial, as it facilitates the imposition of specific protection and prevention actions by civil protection. This research paper discusses an innovative threefold intelligent hybrid system of combined machine learning algorithms HISYCOL (henceforth). First, it deals with the correlation of the conditions under which high pollutants concentrations emerge. On the other hand, it proposes and presents an ensemble system using combination of machine learning algorithms capable of forecasting the values of air pollutants. What is really important and gives this modeling effort a hybrid nature is the fact that it uses clustered datasets. Moreover, this approach improves the accuracy of existing forecasting models by using unsupervised machine learning to cluster the data vectors and trace hidden knowledge. Finally, it employs a Mamdani fuzzy inference system for each air pollutant in order to forecast even more effectively its concentrations. 相似文献
5.
Jonas Feldheim Almuth F. Kessler Julia J. Feldheim Ellina Schulz David Wend Lazaros Lazaridis Christoph Kleinschnitz Martin Glas Ralf-Ingo Ernestus Sebastian Brandner Camelia M. Monoranu Mario Lhr Carsten Hagemann 《International journal of molecular sciences》2022,23(9)
Glioblastoma leads to a fatal course within two years in more than two thirds of patients. An essential cornerstone of therapy is chemotherapy with temozolomide (TMZ). The effect of TMZ is counteracted by the cellular repair enzyme O6-methylguanine-DNA methyltransferase (MGMT). The MGMT promoter methylation, the main regulator of MGMT expression, can change from primary tumor to recurrence, and TMZ may play a significant role in this process. To identify the potential mechanisms involved, three primary stem-like cell lines (one astrocytoma with the mutation of the isocitrate dehydrogenase (IDH), CNS WHO grade 4 (HGA)), and two glioblastoma (IDH-wildtype, CNS WHO grade 4) were treated with TMZ. The MGMT promoter methylation, migration, proliferation, and TMZ-response of the tumor cells were examined at different time points. The strong effects of TMZ treatment on the MGMT methylated cells were observed. Furthermore, TMZ led to a loss of the MGMT promoter hypermethylation and induced migratory rather than proliferative behavior. Cells with the unmethylated MGMT promoter showed more aggressive behavior after treatment, while HGA cells reacted heterogenously. Our study provides further evidence to consider the potential adverse effects of TMZ chemotherapy and a rationale for investigating potential relationships between TMZ treatment and change in the MGMT promoter methylation during relapse. 相似文献
6.
Lazaros Tzounis Titus Gärtner Marco Liebscher Petra Pötschke Manfred Stamm Brigitte Voit Gert Heinrich 《Polymer》2014
The thermoelectric properties of melt-processed nanocomposites consisting of a polycarbonate (PC) thermoplastic matrix filled with commercially available carboxyl (–COOH) functionalized multi-walled carbon nanotubes (MWCNTs) were evaluated. MWCNTs carrying carboxylic acid moieties (MWCNT-COOH) were used due the p-doping that the carboxyl groups facilitate, via electron withdrawing from the electron-rich π-conjugated system. Preliminary thermogravimetric analysis (TGA) of MWCNT-COOH revealed that the melt-mixing was limited at low temperatures due to thermal decomposition of the MWCNT functional groups. Therefore, PC was mixed with 2.5 wt% MWCNT-COOH (PC/MWCNT-COOH) at 240 °C and 270 °C. In order to reduce the polymer melt viscosity, a cyclic butylene terephthalate (CBT) oligomer was utilized as an additive, improving additionally the electrical conductivity of the nanocomposites. The melt rheological characterization of neat PC and PC/CBT blends demonstrated a significant decrease of the complex viscosity by the addition of CBT (10 wt%). Optical and transmission electron microscopy (OM, TEM) depicted an improved MWCNT dispersion in the PC/CBT polymer blend. The electrical conductivity was remarkably higher for the PC/MWCNT-COOH/CBT composites compared to the PC/MWCNT-COOH ones. Namely, the PC/MWCNT-COOH/CBT processed at 270 °C exhibited the best values with electrical conductivity; σ = 0.05 S/m, Seebeck coefficient; S = 13.55 μV/K, power factor; PF = 7.60 × 10−6μW/m K−2, and thermoelectric figure of merit; ZT = 7.94 × 10−9. The PC/MWCNT-COOH/CBT nanocomposites could be ideal candidates for large-scale thermal energy harvesting, even though the presently obtained ZT values are still too low for commercial applications. 相似文献
7.
In this work, a mixed integer linear programming (MILP) model is proposed for the multi-class data classification problem using a hyper-box representation. The latter representation is particularly suitable for capturing disjoint data regions. The objective function used is the minimisation of the total number of misclassified data samples. In order to improve the training and testing accuracy of our approach, an iterative solution procedure is developed to assign potential multiple boxes to each single class. Finally, the applicability of the proposed approach is demonstrated through a number of illustrative examples. According to the computational results obtained, the proposed optimisation-based approach is competitive in terms of prediction accuracy when compared with various standard classifiers. 相似文献
8.
Christos Baloukas Author Vitae Jose L. Risco-Martin Author Vitae Christophe Poucet Author Vitae Lazaros Papadopoulos Author Vitae Juan Lanchares Author Vitae 《Journal of Systems and Software》2009,82(4):590-602
Modern multimedia application exhibit high resource utilization. In order to efficiently run this kind of applications in embedded systems, the dynamic memory subsystem needs to be optimized. A key role in this optimization is played by the dynamic data structures that reside in every real-life application. This paper presents a novel and automated way to optimize dynamic data structures. The search space is pruned using genetic algorithms that converge to the best multilayered data structure implementation for the targeted applications. 相似文献
9.
Electricity storage systems (ESS) for bulk energy storage are principally used for load levelling purposes or for relieving the intermittency of renewables. Another use is electricity arbitrage through the rule of ‘buy low, sell high’. This operation tracks the market‐clearing price (MCP) profiles and produces profit by exploiting the differences between peak and off‐peak prices. The profits made in this way depend on technology characteristics and the market competition level. We investigate the influence of demand‐side management (DSM) on ESS profitability when the only income is from provision of electricity arbitrage services, by optimizing the time allocation of the charge and discharge operations. Two scenarios of DSM in the market have been selected for two management periods (MP): 1 day and 3 days. The longer MP is examined in order to investigate the potential for higher economic value when energy transfer to the next day is permitted. The key finding is that a very small load shifting from peaks to off‐peaks, due to DSM, significantly affects the ESS profit. The significant profit losses the ESS showed are a result of the high capital costs and the small difference of the peak and off‐peak electricity prices in the Greek market. Therefore, under the assumptions we have made for this research, any attempt to use ESS in ‘buy low, sell high’ operation is not profitable. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
10.
Theodoros Koutroumanidis Lazaros Iliadis Georgios K. Sylaios 《Environmental Modelling & Software》2006,21(12):1711-1721
Forecasting, using historic time-series data, has become an important tool for fisheries management. ARIMA modeling, Modeling for Optimal Forecasting techniques and Decision Support Systems based on fuzzy mathematics may be used to predict the general trend of a given fish landings time-series with increased reliability and accuracy. The present paper applies these three modeling methods to forecast anchovy fish catches landed in a given port (Thessaloniki, Greece) during 1979–2000 and hake and bonito total fish catches during 1982–2000. The paper attempts to assess the model's accuracy by comparing model results to the actual monthly fish catches of the year 2000. According to the measures of forecasting accuracy established, the best forecasting performance for anchovy was shown by the DSS model (MAPE = 28.06%, RMSE = 76.56, U-statistic = 0.67 and R2 = 0.69). The optimal forecasting technique of genetic modeling improved significantly the forecasting values obtained by the selected ARIMA model. Similarly, the DSS model showed a noteworthy forecasting efficiency for the prediction of hake landings, during the year 2000 (MAPE = 2.88%, RMSE = 13.75, U-statistic = 0.19 and R2 = 0.98), as compared to the other two modeling techniques. Optimal forecasting produced by combined modeling scored better than application of the simple ARIMA model. Overall, DSS results showed that the Fuzzy Expected Intervals methodology could be used as a very reliable tool for short-term predictions of fishery landings. 相似文献