Sprachübertragung über alternative Netze

The importance of multimedia can not be foreseen. However the combined transport of speech and broadband data will rapidly develop. Voice/data integration is the technology of the future and will more and more substitute the traditional way of information transport. The paper introduces UTA as the alternative to the incumbant operator und describes UTAs network infrastructure, SDH-backbone and broadband multiservice network. Three methods of voice/data integration are presented:

1. voice over ATM
2. voice over Frame Relay
3. voice over IP.

     

Multi-Timescale Modeling and Dynamic Stability Analysis for Sustainable Microgrids: State-of-the-Art and Perspectives

The increasing trend for integrating renewable energy sources into the grid to achieve a cleaner energy system is one of the main reasons for the development of sustainable microgrid (MG) technologies. As typical power-electronized power systems, MGs make extensive use of power electronics converters, which are highly controllable and flexible but lead to a profound impact on the dynamic performance of the whole system. Compared with traditional large-capacity power systems, MGs are less resistant to perturbations, and various dynamic variables are coupled with each other on multiple timescales, resulting in a more complex system in-stability mechanism. To meet the technical and economic challenges, such as active and reactive power-sharing, volt-age, and frequency deviations, and imbalances between power supply and demand, the concept of hierarchical control has been introduced into MGs, allowing systems to control and manage the high capacity of renewable energy sources and loads. However, as the capacity and scale of the MG system increase, along with a multi-timescale control loop design, the multi-timescale interactions in the system may become more significant, posing a serious threat to its safe and stable operation. To investigate the multi-timescale behaviors and instability mechanisms under dynamic inter-actions for AC MGs, existing coordinated control strategies are discussed, and the dynamic stability of the system is defined and classified in this paper. Then, the modeling and assessment methods for the stability analysis of multi-timescale systems are also summarized. Finally, an outlook and discussion of future research directions for AC MGs are also presented.     

Modelling and Coordinated Control of Grid Connected Photovoltaic, Wind Turbine Driven PMSG, and Energy Storage Device for a Hybrid DC/AC Microgrid

In a DC/AC microgrid system, the issues of DC bus voltage regulation and power sharing have been the subject of a significant amount of research. Integration of renewable energy into the grid involves multiple converters and these are vulnerable to perturbations caused by transient events. To enhance the flexibility and controllability of the grid connected converter (GCC), this paper proposes a common DC bus voltage maintenance and power sharing control strategy of a GCC for a DC/AC microgrid. A maximum power point tracking algorithm is employed to enhance the power delivered by the wind turbine and photovoltaic module. The proposed control strategy consists of primary and secondary aspects. In the primary layer control, the DC bus voltage is regulated by the GCC. In the secondary layer, the DC bus voltage is maintained by the energy storage device. This ensures reliable power for local loads during grid failures, while power injection to the grid is controlled by an energy management algorithm followed by reference generation of inductor current in the GCC. The proposed control strategy operates in different modes of DC voltage regulation, power injection to the grid and a hybrid operating mode. It provides wide flexible control and ensures the reliable operation of the microgrid. The proposed and conventional techniques are compared for a 15.8 kW DC/AC microgrid system using the MATLAB/Simulink environment. The simulation results demonstrate the transient behaviour of the system in different operating conditions. The proposed control technique is twice as fast in its transient response and produces less oscillation than the conventional system.     

A Consortium Blockchain-Enabled Double Auction Mechanism for Peer-to-Peer Energy Trading among Prosumers

This paper investigates a double auction-based peer-to-peer (P2P) energy trading market for a community of renewable prosumers with private information on reservation price and quantity of energy to be traded. A novel competition padding auction (CPA) mechanism for P2P energy trading is proposed to address the budget deficit problem while holding the advantages of the widely-used Vickrey-Clarke-Groves mechanism. To illustrate the theoretical properties of the CPA mechanism, the sufficient conditions are identified for a truth-telling equilibrium with a budget surplus to exist, while further proving its asymptotical economic efficiency. In addition, the CPA mechanism is implemented through consortium blockchain smart contracts to create safer, faster, and larger P2P energy trading markets. The proposed mechanism is embedded into blockchain consensus protocols for high consensus efficiency, and the budget surplus of the CPA mechanism motivates the prosumers to manage the blockchain. Case studies are carried out to show the effectiveness of the proposed method.     

Übersetzung von Datenflußgraphen in optimierte Assemblerprogramme für Signalprozessoren

The synthesis of efficient programs for digital signal processors with non-homogeneous register sets is still a challenge of compiler design. In this paper, we introduce the concept of a data flow graph compiler for digital signal processors. In a first step, the data flow graph is decomposed into constrained expression trees and represented by trellis trees, which allows to apply a straight-line code generation algorithm whose complexity depends just linearly on the size of the graph. Registers are assigned by taking into account the constraints of multi-function instructions. The execution time of the resulting assembly code is minimized by exploiting instruction level parallelism and memory layout optimizations.     

Sicherheitstechnologien für E-Commerce 2000

Recently Internet and Intranet have been the topics which mainly influenced the development of modern communication technologies. Today electronic commerce (e-commerce) is becoming the main keyword for the further development of communication technology. Business transactions and trading throughout woldwide connected communication networks are gaining more and more economic importance. The more the public gets in contact with these new technologies the more technicians are forced to make them feel secure and safe with these terms and methods.     

电磁辐射对人体健康的影响

本文引用现代科技威果，阐述了电磁辐射对人体健康可能产生的各类影响。     

Einsatz neuer Medien — Noch größere Datenflut oder übersichtliches Informationsmanagement

The growth of human knowledge, global availability of news and heterogeneous forms of communication makes it increasingly difficult for people to find the right information for certain needs. Some general aspects of new media and their fundamental problems and possibilities are analysed and trends are presented.