Dynamic disturbance rejection controllers for neutral time delay systems with application to a central heating system

In the present paper the problem of disturbance rejection of single input-single output neutral time delay systems with multiple measurable disturbances is solved via dynamic controllers. In particular, the general form of the controller matrices is presented, while the necessary and sufficient conditions for the controller to be realizable are offered. The proposed technique is applied to a test case neutral time delay central heating system. In particular, the nonlinear model of the plant and its linearized approximation are presented. Based on the linearized model, a two-stage controller is designed in order to regulate the room temperature and the boiler effluent temperature. The performance of the closed loop system is investigated through computational experiments.     

Dielectric spectroscopy and gas chromatography methods applied on high-voltage transformer oils

This paper points out the advantages offered by the temperature dependent dielectric spectroscopy in frequency domain, as an additional diagnostic technique for insulation testing of power transformers for life-time prediction. Complex permittivity measurements have been carried out as a function of operating frequency and oil temperature for a wide selection of high voltage transformers and the gaseous byproduct concentrations were also monitored. The work correlates dielectrometry data to the gas chromatography ones.     

Analytical average throughput and delay estimations for LTE uplink cell edge users

Estimating average throughput and packet transmission delay for worst case scenario (cell edge users) is crucial for LTE cell planners in order to preserve strict QoS for delay sensitive applications. Cell planning techniques emphasize mostly on cell range (coverage) and throughput predictions but not on delay. Cell edge users mostly suffer from throughput reduction due to bad coverage and consequently unexpected uplink transmission delays. To estimate cell edge throughput a common practice on international literature is the use of simulation results. However simulations are never accurate since MAC scheduler is a vendor specific software implementation and not 3GPP explicitly specified. This paper skips simulations and proposes an IP transmission delay and average throughput analytical estimation using mathematical modeling based on probability delay analysis, thus offering to cell planners a useful tool for analytical estimation of uplink average IP transmission.     

The Greek School Network: A Paradigm of Successful Educational Services Based on the Dynamics of Open-Source Technology

The Greek school network (GSN) is a closed nationwide educational network that offers advanced telematic and networking services to all primary/secondary education schools and administration offices in Greece. The primary objective of GSN is the provisioning of a network infrastructure for the interconnection of school PC laboratories so that modern educational methods and pedagogical models can be applied to the school community. GSN has scaled in size, has reached maturity, and is currently delivering a wide range of network and telematic services to its users. The emerging power of open-source software provides a sound technological basis for building cutting-edge services, capable of meeting internal administrative and monitoring needs, and modern pedagogical requirements for tools and services. The current paper presents an overview of GSN and an evaluation of its services based on the opinions of its users, and on service utilization and traffic measurement statistics. The paper reaches the conclusion that open-source solutions provide a sound technological platform that can cover, to a great extent, the needs for advanced educational services of the school community.     

Performance evaluation of transport protocols in cloud data center networks

Photonic Network Communications - In recent years, cloud data centers have received increased attention by the research community, due to their key function of hosting a big number of cloud...     

Social media prediction: a literature review

Multimedia Tools and Applications - Social Media Prediction (SMP) is an emerging powerful tool attracting the attention of researchers and practitioners alike. Despite its many merits, SMP has also...     

A Case for Chip Multiprocessors Based on the Data-Driven Multithreading Model

Current high-end microprocessors achieve high performance as a result of adding more features and therefore increasing complexity. This paper makes the case for a Chip-Multiprocessor based on the Data-Driven Multithreading (DDM-CMP) execution model in order to overcome the limitations of current design trends. Data-Driven Multithreading (DDM) is a multithreading model that effectively hides the communication delay and synchronization overheads. DDM-CMP avoids the complexity of other designs by combining simple commodity microprocessors with a small hardware overhead for thread scheduling and an interconnection network. Preliminary experimental results show that a DDM-CMP chip of the same hardware budget as a high-end commercial microprocessor, clocked at the same frequency, achieves a speedup of up to 18.5 with a 78–81% power consumption of the commercial chip. Overall, the estimated results for the proposed DDM-CMP architecture show a significant benefit in terms of both speedup and power consumption making it an attractive architecture for future processors.