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Simple Asynchronous Remote Invocations for Distributed Real-Time Java

More and more, the use of real-time distribution middlewares programmed with high-level languages like Java is becoming of interest for industrial systems because this type of infrastructures reduce development efforts required to both design and maintain complex networked applications. In that way towards having better development tools, this paper deals with the very specific issue of the asynchronism from the particular perspective of Javas distributed technologies. It proposes and evaluates an extension to the Javas remote method invocation (RMI) with additional support for asynchronous remote invocations. Such a mechanism makes the transmission of some messages, typically those that do not require any confirmation from the server, much more efficient than synchronous communications, and consequently they optimize and speed up the performance of many industrial networked applications. In more detail, this paper concerns with the model itself and the set of changes it requires within their middleware programming interfaces and inside communication protocols to accommodate the proposed model. The proposal is supported by empirical evidences from a prototype developed as partial proof-of-concept.

A Simple Data-Muling Protocol

More and more industrial infrastructures consider the use of industrial wireless sensor network (IWSN) technology to perform control activities in industry. The benefits stemmed from IWSNs include flexible access (no wires are required) to elements that may interact with the factory floor. However, this support introduces new challenges: muling the almost permanent connectivity given by wired infrastructures is no longer available in IWSNs. To address this challenge, this paper explores data muling as the ability of transferring data between different elements within an industrial infrastructure. The proposed data-muling protocol uses a dual discovery and update (D&U) strategy. The prototype evaluation carried out on 6LowPan over IEEE 802.15.4 motes provides some insights on the performance that this type of infrastructure may offer within an industrial context. This paper also offers an extensive benchmark that may be used to test bounds and limitations of the proposed D&U protocol on the industrial use-cases.

Concurrency Programming Models in Mobile Real-Time Platforms

To support real-time properties, mobile real-time operating system (RTOS) platforms have added to their classical cyclic executive model more flexible concurrency paradigms based on threads and preemptive priority-based scheduling algorithms. However, in newer mobile RTOS, the concurrency model is also going back to prior cooperative multi-tasking models similar to cyclic executives (based on active objects). This paper presents the concurrency model of a very popular mobile RTOS platform, as Symbian, that contains both concurrency models. This OS has been chosen for its popularity in the market and due to the fact that it includes both concurrency models with real-time support. The traditional AOM (Active Object Model) paradigm is taken in the personal embedded devices community as a means to simplify the interface given to programmers; no usage of synchronization primitives is required. This paper discusses how a combined pattern would take advantage of both worlds: AOM and thread based execution models; it allows using AOM-based programming inside threads in real-time environments.The present invention provides a novel one-piece capstan for a tape cartridge which provides good static dissipative properties and wear resistance. The capstan material of the present invention has a charge decay time of no more than 5 seconds as measured according to Mil B-81705C standard. The capstan material also has a flexural modulus of at least 200,000 psi (1379 MPa). The capstan comprises a hard, dimensionally stable polymer and a static dissipating polymer. The capstan also has an improved structure and geometry which enables the part to be easily molded, reduces drive force requirements with a reduction of material from the prior art design, but with no significant loss of performance properties.

Simple Multiplexing Headers for the JRMP Stream Subprotocol

This article deals with a simple optimization for a level-5 protocol called JRMP (Javas Remote Method Protocol), which is used in a distribution model named Javas RMI (Javas Remote Method Invocation). The main JRMP subprotocol, namely Stream, has been enhanced with a simple and direct multiplexing mechanism that offers the possibility of transferring several parallel request-response interactions without opening new TCP/IP connections. The overhead required to process headers and the advantages stemmed from the approach in terms of response-time are explored on a switched-ethernet benchmark application.