Performance Analysis of Industrial Communications Devices and their Associated Protocols

How much faster is PROFIBUS than Modbus? What are the performance characteristics of one over the other? Many of the common communications devices and protocols used for industrial systems do not have quantitative measurements or comparisons published in the public domain. These protocols are commonly used in real-time control systems and process control systems using Programmable Logic Controllers (PLCs) as part of the collection of information from remote devices. Many of these devices can vary from proximity sensors and limit switches to bar code scanners and other PLCs. One of the most important attributes that these systems require is called determinism. The definition for determinism from the Merriam-Webster dictionary [1] is: 1 a: a theory or doctrine that acts of the will, occurrences in nature, or social or psychological phenomena are causally determined by preceding events or natural laws b : a belief in predestination 2 : the quality or state of being determined For many engineers, this means that the equipment they design will have predicable responses and results from the PLCs and other types of controllers used for industrial equipment and systems. System engineers and developers of industrial and military equipment generally do not, but should, perform this type of analysis for their equipment. Most of the common comparisons are only based on the bandwidth of the transport media, such as 10 Megabit Ethernet or 100 Megabit Ethernet. These comparisons do not take the protocols or the volume of data into consideration. Most system engineers and developers select devices and protocols based on simply the raw bandwidth of the media, rather than taking the overhead of the protocols and hardware latencies into consideration..

Review article: silicon carbide. Structure, properties and processing Artigo revisão: carbeto de silício, estrtutura, propriedades e processamento

In view of considerable interest in the development of liquid phase sintered structural and high-temperature ceramics on the base of silicon carbide, a comprehensive review of the data on structure, properties and the known methods of processing of silicon carbide seems timely. The most striking feature of silicon carbide is its polytypism, i.e. formation of a great number of different structural modifications without any change in composition. Although this feature of silicon carbide was extensively studied, no systematic up to date analysis was done. However, polytypism and the tendency of the polytypes to undergo structural transformations at working temperatures may lead to uncontrollable modification of the materials properties, and therefore needs to be fully understood. Furthermore, the recently developed liquid phase sintering technique for silicon carbide densification is of an undoubtful interest and the overview of the results achieved until present time may provide some guidelines for the ceramists.<br>Em vista do considerável interesse no desenvolvimento de cerâmicas estruturais e para aplicações em alta temperatura, é oportuna uma revisão quanto a estrutura, propriedades e métodos conhecidos de processamento de cerâmicas a base de carbeto de silício sinterizados via fase líquida. A característica mais interessante do carbeto de silício é o seu politipismo, isto é, a formação de um grande número modificações estruturais para uma mesma composição. Embora este fenômeno venha sendo extensivamente estudado, não se tem até o momento, uma análise sistemática do mesmo, o que seria de extrema importância, uma vez que o politipismo e a tendência à transformação estrutural destes politipos em temperaturas típicas de trabalho podem levar a incontroláveis modificações nas propriedades do material. Além disso, os recentes avanços obtidos na densificação do carbeto de silício através da técnica de sinterização na presença de fase líquida justificam uma avaliação dos resultados obtidos até o momento, que podem proporcionar alguma orientação aos profissionais da área