Combined Integer and Floating Point Multiplication Architecture(CIFM) for FPGAs and Its Reversible Logic Implementation

In this paper, the authors propose the idea of a combined integer and floating point multiplier(CIFM) for FPGAs. The authors propose the replacement of existing 18x18 dedicated multipliers in FPGAs with dedicated 24x24 multipliers designed with small 4x4 bit multipliers. It is also proposed that for every dedicated 24x24 bit multiplier block designed with 4x4 bit multipliers, four redundant 4x4 multiplier should be provided to enforce the feature of self repairability (to recover from the faults). In the proposed CIFM reconfigurability at run time is also provided resulting in low power. The major source of motivation for providing the dedicated 24x24 bit multiplier stems from the fact that single precision floating point multiplier requires 24x24 bit integer multiplier for mantissa multiplication. A reconfigurable, self-repairable 24x24 bit multiplier (implemented with 4x4 bit multiply modules) will ideally suit this purpose, making FPGAs more suitable for integer as well floating point operations. A dedicated 4x4 bit multiplier is also proposed in this paper. Moreover, in the recent years, reversible logic has emerged as a promising technology having its applications in low power CMOS, quantum computing, nanotechnology, and optical computing. It is not possible to realize quantum computing without reversible logic. Thus, this paper also paper provides the reversible logic implementation of the proposed CIFM. The reversible CIFM designed and proposed here will form the basis of the completely reversible FPGAs.Comment: Published in the proceedings of the The 49th IEEE International Midwest Symposium on Circuits and Systems (MWSCAS 2006), Puerto Rico, August 2006. Nominated for the Student Paper Award(12 papers are nominated for Student paper Award among all submissions

Estimation of Mean Time between Failures in Two Unit Parallel Repairable System

Mean time between failures is a method for estimating the reliability parameters of any repairable system. MTBF is also helpful in performing decision analysis in parallel and series systems and subsystems. The MTBF is the reciprocal of the failure rate when each component which fails is replaced immediately with another having the identical failure rate. There are situations when the assumption of a constant failure rate is not realistic and in many of these situations one assumes instead that the failure rate function increases or decreases smoothly with time i.e. there are no discontinuity or turning points. In this paper, we have tried to estimate MTBF taking real failure rate in case of two unit parallel repairable system and study its consistency with either the initial or the last stage of the failure rate curve

A complex multi-state k-out-of-n: G system with preventive maintenance and loss of units

In this study, a multi-state k-out-of-n: G system subject to multiple events is modeled through a Markovian Arrival Process with marked arrivals. The system is composed initially of n units and is active when at least k units are operational. Each unit is multi-state, each of which is classified as minor or major according to the level of degradation presented. Each operational unit may undergo internal repairable or non-repairable failures, external shocks and/or random inspections. An external shock can provoke extreme failure, while cumulative external damage can deteriorate internal performance. This situation can produce repairable and non-repairable failures. When a repairable failure occurs the unit is sent to a repair facility for corrective repair. If the failure is non-repairable, the unit is removed. When the system has insufficient units with which to operate, it is restarted. Preventive maintenance is employed in response to random inspection. The system is modeled in an algorithmic and computational form. Several interesting measures of performance are considered. Costs and rewards are included in the system. All measures are obtained for transient and stationary regimes. A numerical example is analyzed to determine whether preventive maintenance is profitable, financially and in terms of performance.Junta de Andalucía (Spain) FQM-307Ministerio de Economía y Competitividad (España) MTM2017-88708-PEuropean Regional Development Fund (ERDF

Concurrent Importance and Sensitivity Analysis Applied to Multiple Fault Trees

Complex industrial systems may present different potentially dangerous failure states (Top-events). The analysis of system failure states via Fault-tree technique allows determining the failure frequency of potential accidents and the importance measures of components' failure modes. The combination of Importance and Sensitivity Analysis (ISA) constitutes a very powerful tool to improve the design of critical systems or to prove that the design satisfies safety requirements. The present reports describes a novel approach to implement Importance and Sensitivity analysis applied to Fault-trees, which consists of the concurrent analysis of all relevant system's Fault-trees to identify the weakest parts of the system which require further design improvement. This approach aims at overcoming the limitations of the current methods in application for ISA in which Top-events are sequentially analysed. In addition the proposed method extends the ISA application also to 'over-reliable' system functions (if any) on which the reliability/maintainability characteristics of the involved components can be relaxed with consequent cost saving. The result is a uniformly protected system satisfying the predefined design goals.JRC.G.7-Traceability and vulnerability assessmen

TIDAL STREAM DEVICES: RELIABILITY PREDICTION MODELS DURING THEIR CONCEPTUAL & DEVELOPMENT PHASES

Tidal Stream Devices (TSDs) are relatively new renewable energy converters. To date only a few prototypes, primarily horizontal-axis turbine designs, are operational; therefore, little reliability data has accumulated. Pressure to develop reliable sources of renewable electric power is encouraging investors to consider the technology for development. There are a variety of engineering solutions under consideration, including floating tethered, submerged tethered, ducted sea-bed bottom-mounted and sea-bed pile-mounted turbines, but in the absence of in-service reliability data it is difficult to critically evaluate comparative technologies. Developing reliability models for TSDs could reduce long-term risks and costs for investors and developers, encouraging more feasible and economically viable options. This research develops robust reliability models for comparison, defining TSD reliability block diagrams (RBD) in a rigorous way, using surrogate reliability data from similarly-rated wind turbines (WTs) and other relevant marine and electrical industries. The purpose of the research is not to derive individual TSD failure rates but to provide a means of comparison of the relative reliabilities of various devices. Analysis of TSD sub-assemblies from the major types of TSDs used today is performed to identify criticality, to improve controllability and maintainability. The models show that TSDs can be expected to have lower reliability than WTs of comparable size and that failure rates increase with complexity. The models also demonstrate that controls and drive train sub-assemblies, such as the gearbox, generator and converter, are critical to device reliability. The proposed developed models provide clear identification of required changes to the proposed TSD system designs, to raise availability, including duplication of critical systems, use of components developed for harsh environments and migration of equipment onshore, wherever practicable

Estimation of Reliability Parameters of a Complex Repairable System

In this paper estimation of reliability parameters of a complex repairable system is considered and semi-markov process is used in analyzing various reliability parameters such as Transition Probabilities, Mean sojourn times, MTSF, Availability and Busy period of repairman in repairing the failed units. In the past, Arora et-al[2] has done reliability analysis of two unit standby redundant system with constrained repair time. Gupta et-al [6] has worked on a compound redundant system involving human failure. Rander et-al [2] has evaluated the cost analysis of two dissimilar cold standby systems with preventive maintenance and replacement of standby units. A pioneer work in this field was done by Gopalan [1] and Osaki [3] by performing analysis of warm standby system and parallel system with bivariate exponential life respectively. Earlier, Pathak et al [7&8] studied reliability parameters of a main unit with its supporting units and also compared the results with two different distributions. In this paper, Chapman-Kolmogorov equations are used to develop recursive relations. Also the involvement of preventive maintenance in the model increases the reliability of the functioning units. In the end a particular case is also taken for discussion