2973181
Sharing I/O in Strongly Partitioned Real-Time Systems
Strongly partitioned real-time systems have been adopted to provide an integrated run time environment for applications with varied criticalities. This is achieved by guaranteeing spatial as well as temporal partitioning for the applications. To enable accesses to shared I/O devices in such an environment, this paper provides an effective model that the co-existence of any application does not hinder the execution of IO operations or spatial and temporal requirements of other applications. The model utilizes a microkernel-based approach to regulate the work of drive drivers and thus integrate the device-sharing model with the microkernel.
40618061
Transaction Recovery in Distributed DB/DC Systems: A Progressive Approach
31591898
Scanning the issue - special issue on real-time systems
920212
Resource scheduling in dependable integrated modular avionics
In the recent development of avionics systems, integrated modular avionics (IMA) is advocated for next generation architecture that needs integration of mixed criticality real-time applications. These integrated applications meet their own timing constraints while sharing avionics computer resources. To guarantee timing constraints and dependability of each application, an IMA-based system is equipped with the schemes for spatial and temporal partitioning. We refer the model as SP-RTS (strongly partitioned real-time system), which deals with processor partitions and communication channels as its basic scheduling entities. This paper presents a partition and channel-scheduling algorithm for the SP-RTS. The basic idea of the algorithm is to use a two-level hierarchical schedule that activates partitions (or channels) following a distance-constraints guaranteed cyclic schedule and then dispatches tasks (or messages) according to a fixed priority schedule. To enhance schedulability, we devised heuristic algorithms for deadline decomposition and channel combining. The simulation results show the schedulability analysis of the two-level scheduling algorithm and the beneficial characteristics of the proposed deadline decomposition and channel combining algorithms.
30590203
Efficient State-Saving Architectures for Power-Mode Switching
Time and energy is expended in switching between power modes (e.g., active, hibernate, sleep, etc.). Powering off cache is one major reason for this. When there is a switch in the power-mode involving cache power-off, the system spends time and energy in filling the cache with new data (inherent cache misses). In our technique, before powering off the cache, we save its state in Embedded DRAM and bring it back when the previous power mode is restored. Our experiments have showed that in a majority of cases the cache contents are too valuable to be erased. By saving the contents we can reduce switching speed and energy. We present a heuristic to save the most relevant cache contents so that power and delay overheads are minimized. To measure the area overhead a synthesizable VHDL model was designed.
10753893
Evaluation of Error Recovery Blocks Used for Cooperating Processes
Three alternatives for implementing recovery blocks (RB's) are conceivable for backward error recovery in concurrent processing. These are the asynchronous, synchronous, and the pseudorecovery point implementations. Asynchronous RB's are based on the concept of maximum autonomy in each of concurrent processes. Consequently, establishment of RB's in a process is made independently of others and unbounded rollback propagations become a serious problem. In order to completely avoid unbounded rollback propagations, it is necessary to synchronize the establishment of recovery blocks in all cooperating processes. Process autonomy is sacrificed and processes are forced to wait for commitments from others to establish a recovery line, leading to inefficiency in time utilization. As a compromise between asynchronous and synchronous RB's we propose to insert pseudorecovery points (PRP's) so that unbounded rollback propagations may be avoided while maintaining process autonomy. We developed probabilistic models for analyzing these three methods under standard assumptions in computer performance analysis, i.e., exponential distributions for related random variables. With these models we have estimated 1) the interval between two successive recovery lines for asynchronous RB's, 2) mean loss in computation power for the synchronized method, and 3) additional overhead and rollback distance in case PRP's are used.
6621245
Application of Machine Shop Data Model in Manufacturing Simulation
Simulation technology holds tremendous promise for the manufacturing industry. A machine shop data model has been developed at the National Institute of Standards and Technology (NIST) to represent neutral machine shop data for supporting machine shop manufacturing simulation [1]. This paper discusses the data model and its application in manufacturing simulation. The paper also proposes an application framework that integrates the simulation model, machine shop database, and machine shop XML (Extensible Markup Language) data document. A prototype system is developed to present the application of machine shop data model using the proposed framework.
14475818
Data exchange for machine shop simulation
Manufacturing simulation systems normally provide interfaces for data import and export using proprietary formats. Dependent data interfaces limit simulation applications in the manufacturing industry. This paper describes a mechanism for transferring data between a traditional database and XML files, which represent a machine shop data model developed at the National Institute of Standards and Technology (NIST). The data model is described by XML (eXtensible Markup Language) and UML (Unified Modeling Language). The data transfer mechanism is based on document object model (DOM), XML path language (XPath), and open database connectivity (ODBC) database engines. A prototype implementation is also described in this paper
19081367
Robust technique for estimating the bearings of cyclostationary signals
This paper deals with the problem of direction finding using cyclostationary signals in the presence of cycle frequency error (CFE). By exploiting the signal cyclostationarity, cyclic MUSIC and conjugate cyclic MUSIC presented in Gardner (Cyclostationarity in Communications and Signal Processing, New York, 1994; Proc. IEEE 76 (1988) 845) have been shown to be effective for signal-selective direction finding. However, they suffer from severe performance degradation even if there is a small error in the cycle frequency of the signals of interest. In this paper, we first evaluate the performance of conjugate cyclic MUSIC when CFE exists. An analytical formula is derived to show the behavior of the performance degradation due to CFE. By exploiting the eigenstructure of the conjugate cyclic correlation matrix of the received array data, we develop a technique including a method for estimating the cycle frequency of the SOI and an efficient method in conjunction with a subspace-fitting algorithm to achieve robust direction finding against CFE. Several simulation examples confirming the theoretical analysis and showing the effectiveness of the proposed technique are also presented.
12566781
Web-Based Simulation with Server Application Approach under Distributed Environment
12254873
Process Knowledge and Data Quality Outcomes
What modes and domains of knowledge about data production processes are most critical for producing high-quality data? This study provides an answer to this question. Data are collected via questionnaire and analyzed using linear regression. The results show some similarities and differences in which knowledge variables are significant for various data quality dimensions. Three results are of particular interest to data quality managers and researchers. The first is the complexity and mix of knowledge associated with producing accurate data. The second is the significant results overall for knowledge about the data collection process as compared to data storage and utilization processes. The third is the negative associations of the knowing-why mode of knowledge as compared to the positive associations for knowing-what and knowing-how. Each of these results has managerial implications and generates avenues for further research.