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The trend towards smaller transistor technologies and lower operating voltages stresses the hardware and makes transistors more susceptible to transient errors. In future systems, performance and power gains will come at the cost of unreliable areas on the chip. For this reason, there is an increased need for low-overhead highly-reliable error detection methodologies. In the last years, several techniques have been proposed. The majority of them are based on redundancy which can be implemented at several levels (e.g., hardware, instruction, thread, process, etc). In instruction-level error detection approaches, the compiler replicates the instructions of the program and inserts checks wherever they are needed. The checks evaluate code correctness and decide whether or not an error has occurred. This type of error detection is more flexible than the hardware alternatives. It allows the programmer to choose the protected area of the program and it can be applied without any hardware modifications. On the other hand, the replicated instructions and the checks cause a large slowdown making software techniques less appealing. In this thesis, we propose two techniques that aim at reducing the error detection overhead of compiler-based approaches and improving system’s performance without sacrificing the fault-coverage. The first technique, DRIFT, achieves this by decoupling the execution of the code (original and replicated) from the checks. The checks are compare and jump instructions. The latter ones tend to make the code sequential and prohibit the compiler from performing aggressive instruction scheduling optimizations. We call this phenomenon basic-block fragmentation. DRIFT reduces the impact of basic-block fragmentation by breaking the synchronized execute-check-confirm-execute cycle. In this way, DRIFT generates a scheduler-friendly code with more instruction-level parallelism (ILP). As a result, it reduces the performance overhead down to 1.29× (on average) and outperforms the state-of-the-art by up to 29.7% retaining the same fault-coverage. Next, CASTED focuses on reducing the impact of error detection overhead on single-chip scalable architectures that are composed of tightly-coupled cores. The proposed compiler methodology adaptively distributes the error detection overhead to the available resources across multiple cores, fully exploiting the abundant ILP of these architectures. CASTED adapts to a wide range of architecture configurations (issue-width, inter-core communication). The results show that CASTED matches the performance of, and often outperforms, sometimes by as mush as 21.2%, the best fixed state-of-the-art approach while maintaining the same fault coverage.

Automated fault diagnosis in induction machines is a difficult task and normally requires background information of electrical machines. Here a different methodology to the condition monitoring problem is devised. The approach is based entirely on Digital Signal Processing (DSP) and Statistical Pattern Recognition (PR). Description of machine conditions is extracted from empirical data. The main tasks that must be carried out by a PR-based condition monitoring system are: condition identification, knowledge reinforcement and knowledge creation for previously unseen conditions. The DSP operations are employed to quickly isolate sensor faults and to remove noise using data acquired from a single channel. DSP transformations may seem promising in making the monitoring system portable. Most importantly, they can compensate for operational changes in the machine. These changes affect the supply line currents and the primary signal quantities to be measured, i.e. the current and the axial leakage flux. The data which is input to the statistical monitoring system may be transformed, in the form of features, or remain unaltered. The system exploits the statistical properties of the feature vectors. The particular features, namely the LAR coefficients, convey short-term, high-resolution spectral information. For a long record, the feature vector sequence may provide information about changes in the record spectral characteristics, with time. Many induction machine processes are stationary and they can be properly be dealt with by a simple statistical classifier, e.g. a Gaussian model. For nonstationary processes, the system may employ a more comprehensive tool, namely the Hidden Markov Model. which may track the changing behaviour of the process in question. Initially a limited number of machine conditions are available to the process engineer. By identifying their boundaries, new faulty conditions could be signalled for and adopted into the database.

The prefailure detection of faults in operating plant can effect major rewards in both safety and economy. A successful on-condition maintenance philosophy would pay great dividends particularly in the offshore oil industry where -until recently, only token methods have been employed. Many techniques are available for monitoring mechanical plant and several of these are considered in general terms. Industrial methods are subsequently evaluated on reciprocating compressor and rolling element bearing faults. Bearing fault analysis is considered in two stages. Initially, a series of vibration based techniques are evaluated on a large relatively noise free rotating machine. The techniques of greatest worth carrier spectra, autospectra, time signature analysis and statistical assessments - are then applied to bearings in the hostile environment of a reciprocating machine. It is shown that while discrete faults often produce predictable periodic vibrational patterns, a monitoring system aimed solely at such vibrational phenomena cannot be relied upon. To this end, a diagnostic system must encompass a series of techniques, including carrier spectrum, time signature and statistical analyses. A series of valve and piston faults in reciprocating machines are also studied. By using a number of monitoring techniques, a catalogue of fault characteristics is constructed, and the methods of greatest worth are high-lighted. It is noted that due to the complexities of a reciprocating machine, fault characteristics vary with load, and this must be borne in mind when interpreting the various parameter displays. No single technique can provide a complete cover for all compressor faults, and it is shown that those of greatest worth are acoustic emission, combined pressure and vibration plots, temperature and performance analysis. An indication of compressor temperature and internal cylinder pressure can greatly ease the detection and diagnostic process, and for the latter, bolt load determinations may be a valuable aid.

The work, of which this thesis is a record, is concerned with the development of a microprocessor-based signal analyser for machine condition monitoring. Until recently, the technology did not exist to produce such an instrument in a 'semi-portable' form. The work proceeds with a revision of condition monitoring and digital techniques which may be implemented on such an instrument. These techniques can be used to detect such faults as: bearing wear; out of balance; shaft misalignment; damaged gears and electrically induced vibration. The greater part of this work involves: firstly, establishing a suitable hardware architecture for the instrument and, secondly, implementing the digital signal processing algorithms required. Such a system, capable of implementing both time and spectral techniques, has been developed to laboratory prototype level. The system consists of a high-speed, multi-channel data acquisition unit and both 8-bit and 16-bit microprocessor systems. The microprocessors execute the operating system and signal processing software. The aim, to produce a simple to use and flexible instrument, was sustained throughout the design phase. The result is an instrument which should offer multi-functional protection of plant.

The Clark fault is one of the primary dextral faults in the San Jacinto fault zone system, southern California. Previous mapping of the Clark fault at its southern termination in the San Felipe Hills reveals it as a broad right lateral shear zone that ends north of the crossing, northeast-striking, left-lateral Extra fault. We investigate the relationship between the dextral Clark fault and the sinistral Extra fault to determine whether the Clark fault continues to the southeast. We present new structural, geophysical and geomorphic data that show that the Extra fault is a ~7 km wide, coordinated fault array comprised of four to six left-lateral fault zones. Active strands of the Clark fault zone persists through the Extra fault array to the Superstition Hills fault in the subsurface and rotate overlying sinistral faults in a clockwise sense. New detailed structural mapping between the San Felipe and Superstition Hills confirms that there is no continuous trace of the Clark fault zone at the surface but the fault zone has uplifted an elongate region ~950 km. sq. of latest Miocene to Pleistocene basin-fill in the field area and far outside of it. Detailed maps and cross sections of relocated microearthquakes show two earthquake swarms, one in 2007 and another in 2008 that project toward the San Felipe Hills, Tarantula Wash and Powerline strands of the dextral Clark fault zone in the San Felipe Hills, or possibly toward the parts of the Coyote Creek fault zone. We interpret two earthquake swarms as activating the San Jacinto fault zone beneath the Extra fault array. These data coupled with deformation patterns in published InSAR data sets suggest the presence of possible dextral faults at seismogenic depths that are not evident on the surface. We present field, geophysical and structural data that demonstrate dominantly left-lateral motion across the Extra fault array with complex motion on secondary strands in damage zones. Slickenlines measured within three fault zones in the Extra fault array reveal primarily strike-slip motion on the principal fault strands. Doubly-plunging anticlines between right-stepping en echelon strands of the Extra fault zone are consistent with contraction between steps of left-lateral faults and are inconsistent with steps in dominantly normal faults. Of the 21 published focal mechanisms for earthquakes in and near the field area, all record strike-slip and only two have a significant component of extension. Although the San Sebastian Marsh area is dominated by northeast-striking leftlateral faults at the surface, the Clark fault is evident at depth beneath the field area, in rotated faults, in microseismic alignments, and deformation in the Sebastian uplift. Based on these data the Clark fault zone appears to be continuous at depth to the Superstition Hills fault, as Fialko (2006) hypothesized with more limited data sets.

The demands of future computing, as well as the challenges of nanometer-era VLSI design, will require new design techniques and design styles that are simultaneously high performance, energy-efficient, and robust to noise and process variation. One of the emerging problems concerns the communication mechanisms between the increasing number of blocks, or cores, that can be integrated onto a single chip. The bus-based systems and point-to-point interconnection strategies in use today cannot be easily scaled to accommodate the large numbers of cores projected in the near future. Network-on-chip (NoC) interconnect infrastructures are one of the key technologies that will enable the emergence of many-core processors and systems-on-chip with increased computing power and energy efficiency. This dissertation is focused on testing, yield improvement and fault-tolerance of such NoC infrastructures. A fast, efficient test method is developed for NoCs, that exploits their inherent parallelism to reduce the test time by transporting test data on multiple paths and testing multiple NoC components concurrently. The improvement of test time varies, depending on the NoC architecture and test transport protocol, from 2X to 34X, compared to current NoC test methods. This test mechanism is used subsequently to perform detection of NoC link permanent faults, which are then repaired by an on-chip mechanism that replaces the faulty signal lines with fault-free ones, thereby increasing the yield, while maintaining the same wire delay characteristics. The solution described in this dissertation improves significantly the achievable yield of NoC inter-switch channels – from 4% improvement for an 8-bit wide channel, to a 71% improvement for a 128-bit wide channel. The direct benefit is an improved fault-tolerance and increased yield and long-term reliability of NoC based multicore systems.

Spot cores from Phase 1 drilling of the main borehole at the San Andreas Fault Observatory at Depth (SAFOD) were mapped to characterize the mesoscale structure and infer paleostress at depth. Cores were oriented by comparing mapped structures with image logs of the borehole. The upper core (1476-1484 m measured depth, MD) is a medium-grained, weakly foliated, hornblende-biotite granodiorite containing leucocratic phenocrysts and lenses. Principal structures are sub-vertical veins, shallow dipping shears, and natural fractures of unknown kinematics. The features are compatible with horizontal extension and right-lateral, normal, oblique-slip on faults striking approximately parallel to the SAF. The lower core (3055.6-3067.2 m MD) has massivebedded, pebble conglomerates and coarse to fine grained arkosic sandstones grade into siltstones. Principal structure features are conjugate shears and two minor faults. The fracture fabric is consistent with strike-slip faulting and a maximum principal compressive paleostress at ~80° to the SAF plane. This paleostress is essentially parallel to the current in situ stress measured in the main borehole and to paleostresses inferred from fracture fabrics in exhumed faults of the San Andreas system to the south. The similarity between the current state of stress and paleostress states supports the suggestion that the maximum principal compressive stress direction is, on average, at high angles to the SAF and that the fault has been weak over geologic time.

We address two problems dealing with fault-tolerant communication in networks. The first one is designing a distributed storage protocol tolerant to Byzantine failure of servers. The protocol implements a multi-writer multi-reader register which satisfies a weaker consistency condition called MWReg. Most of the earlier work gives multiwriter implementations by simulating m copies of a single-writer protocol where m is the number of writers. Our solution gives a direct multi-writer implementation and thus has bounded message and time complexity independent of the number of writers. We have simulated the complete protocol to test its performance and also proved its correctness theoretically. The second problem we address is of providing a reliable communication link between two nodes in a network. We present a capacity reservation algorithm in the case for upper bounds on edge capacities and costs associated with using per unit capacity on any edge. We give a flow based approximation algorithm with cost at most four times optimal. To conclude, we design a distributed storage protocol and a capacity reservation algorithm which are tolerant to network failures.

This research deals with the comparison of fault signatures in induction motors. The primary objective is to study and analyze the similarities in the electrical and mechanical fault signatures, and to determine the suitability of the former for effective motor fault detection. Currently, vibration analysis is the dominant means for mechanical fault detection for use in condition-based maintenance. The use of electrical signatures for mechanical fault detection in electric motors is becoming of interest. Due to its cost-effective nature and ease of use, electrical sensors are preinstalled at the motor switchgear by manufacturers. However in order to achieve this for mechanical faults, a systematic comparison between the vibration signatures and electric current signatures must be performed to study the effectiveness of such an approach. The behavior of vibration signatures as measured through tri-ax accelerometers installed at both in-board and out-board sides, and the three phase motor current signatures as compared to their corresponding healthy baselines is analyzed through a sequence of signal processing algorithms. The procedure is carried out for different types of mechanical faults including broken rotor bars, air-gap eccentricity, mechanical imbalance and deteriorating bearings staged on motors of different make and power rating. A comparison is then made between the two fault indicators derived from mechanical and electrical measurements, respectively.