Andaman Postseismic Deformation Observations: Still Slipping after All These Years?

More than six years after the great (M-w 9.2) Sumatra-Andaman earthquake, postevent processes responsible for relaxation of the coseismic stress change remain controversial. Modeling of Andaman Islands Global Positioning System (GPS) displacements indicated early near-field motions were dominated by slip down-dip of the rupture, but various researchers ascribe elements of relaxation to dominantly poroelastic, dominantly viscoelastic, and dominantly fault slip processes, depending primarily on their measurement sampling and modeling tools used. After subtracting a pre-2004 interseismic velocity, significant transient motion during the 2008.5-2010.5 epoch confirms that postseismic relaxation processes continue in Andaman. Modeling three-component velocities as viscoelastic flow yields a weighted root-mean-square (wrms) misfit that always exceeds the wrms of the measured signal (26.3 mm/yr). The best-fitting models are those that yield negligible deformation, indicating the model parameters have no real physical meaning. GPS velocities are well fit (wrms 4.0 mm/yr) by combining a viscoelastic flow model that best fits the horizontal velocities with similar to 50 cm/yr thrust slip down-dip of the coseismic rupture. Both deep slip and flow respond to stress changes, and each can significantly change stress in the realm of the other; it therefore is reasonable to expect that both transient deep slip and viscoelastic flow will influence surface deformation long after a great earthquake.

Intelligent Approach for Fault Diagnosis in Power Transmission Systems Using Support Vector Machines

This paper presents an approach for identifying the faulted line section and fault location on transmission systems using support vector machines (SVMs) for diagnosis/post-fault analysis purpose. Power system disturbances are often caused by faults on transmission lines. When fault occurs on a transmission system, the protective relay detects the fault and initiates the tripping operation, which isolates the affected part from the rest of the power system. Based on the fault section identified, rapid and corrective restoration procedures can thus be taken to minimize the power interruption and limit the impact of outage on the system. The approach is particularly important for post-fault diagnosis of any mal-operation of relays following a disturbance in the neighboring line connected to the same substation. This may help in improving the fault monitoring/diagnosis process, thus assuring secure operation of the power systems. In this paper we compare SVMs with radial basis function neural networks (RBFNN) in data sets corresponding to different faults on a transmission system. Classification and regression accuracy is reported for both strategies. Studies on a practical 24-Bus equivalent EHV transmission system of the Indian Southern region is presented for indicating the improved generalization with the large margin classifiers in enhancing the efficacy of the chosen model.

Switching and fault transient analysis of 765 kV transmission systems

The analysis of electromagnetic transients arising in EHV/UHV power networks gives necessary information about the possible stresses on the different network components, which will determine their proper design, limits of operation as well as their pertinent protection strategies. This paper describes the transient analysis of 765 kV EHV transmission system which is a typical expansion in Indian power grid system. Considering various conditions, switching transient and fault transient studies are carried out. A FORTRAN version of EMTP is developed, to study a practical example, then a comparison with the results available in the literature is made.

Self Repair in Circuits-Automating Open Fault Repair in Integrated Circuits Using Field-Induced Aggregation of Carbon Nanotubes

This paper presents studies on the use of carbon nanotubes dispersed in an insulating fluid to serve as an automaton for healing open-circuit interconnect faults in integrated circuits. The physics behind the repair mechanism is the electric-field-induced diffusion limited aggregation. On the occurrence of an open fault, the repair is automatically triggered due to the presence of an electric field across the gap. We perform studies on the repair time as a function of the electric field and dispersion concentrations with the above application in mind.

AdFT: An Adaptive Framework for Fault Tolerance on Large Scale Systems using Application Malleability

Exascale systems of the future are predicted to have mean time between failures (MTBF) of less than one hour. Malleable applications, where the number of processors on which the applications execute can be changed during executions, can make use of their malleability to better tolerate high failure rates. We present AdFT, an adaptive fault tolerance framework for long running malleable applications to maximize application performance in the presence of failures. AdFT framework includes cost models for evaluating the benefits of various fault tolerance actions including checkpointing, live-migration and rescheduling, and runtime decisions for dynamically selecting the fault tolerance actions at different points of application execution to maximize performance. Simulations with real and synthetic failure traces show that our approach outperforms existing fault tolerance mechanisms for malleable applications yielding up to 23% improvement in application performance, and is effective even for petascale systems and beyond.

On the Influence of Neighboring Conducting Objects on the Induced Currents in Simple Down Conductors Due to Nearby Lightning Strike

A lightning strike in the neighborhood can induce significant currents in tall down conductors. Though the magnitude of induced current in this case is much smaller than that encountered during a direct strike, the probability of occurrence and the frequency content is higher. In view of this, appropriate knowledge on the characteristics of such induced currents is relevant for the scrutiny of the recorded currents and in the evaluation of interference to the electrical and electronic system in the vicinity. Previously, a study was carried out on characteristics of induced currents assuming ideal conditions, that there were no influencing objects in the vicinity of the down conductor and channel. However, some influencing conducting bodies will always be present, such as trees, electricity and communication towers, buildings, and other elevated objects that can affect the induced currents in a down conductor. The present work is carried out to understand the influence of nearby conducting objects on the characteristics of induced currents due to a strike to ground in the vicinity of a tall down conductor. For the study, an electromagnetic model is employed to model the down conductor, channel, and neighboring conducting objects, and Numerical Electromagnetic Code-2 is used for numerical field computations. Neighboring objects of different heights, of different shapes, and at different locations are considered. It is found that the neighboring objects have significant influence on the magnitude and nature of induced currents in a down conductor when the height of the nearby conducting object is comparable to that of the down conductor.

A THREE-WHEELED MOBILE ROBOT FOR TRAVERSING UNEVEN TERRAIN WITHOUT SLIP: SIMULATION AND EXPERIMENTS

A wheeled mobile robot (WMR) can move on uneven terrains without slip if the wheels are allowed to tilt laterally. This paper deals with the analysis, design and experimentations with a WMR where the wheels can tilt laterally. The wheels of such a WMR must be equipped with two degrees of freedom suspension mechanism. A prototype three-wheeled mobile robot is fabricated with a two degree-of-freedom suspension mechanism. Simulations show that the three-wheeled mobile robot can traverse uneven terrains with very little slip and experiments with the prototype on a representative uneven terrain confirm that the slip is significantly reduced.

Sustainability of apparent slip in micro-channel flows

In the present work, we experimentally study the flow of water over textured hydrophobic surfaces in a micro-channel. Shear stress measurements are done along with direct visualization of trapped air pockets on the hydrophobic surface. The trapped air pockets on such surfaces are known to be responsible for apparent slip at these surfaces and hence in significant drag reduction. In typical circumstances, the apparent slip reduces over time as seen, for example, from our shear stress measurements. This implies that the drag reduction will not be sustained. We have performed extensive visualizations of the trapped air pockets while varying flow parameters like the flow rate and the pressure. We present here direct visualizations that show that under some conditions, the air pockets can grow with time. The variation of the air pocket size with time is found to change qualitatively and quantitatively as the flow rate is varied. These measured changes in the air pocket size with time have a direct bearing on the sustainability of apparent slip in micro-channel flows.

Effect of fault resistance and grid short circuit MVA on impedance seen by distance relays on lines fed from wind turbine generating units (WTGU)

This paper deals with line protection challenges experienced in system having substantial wind generation penetration. Two types of WTGU: Doubly Fed (DFIG) and Squirrel Cage (SCIG) Induction Generators are simulated and connected to grid with single circuit transmission line. The paper summarizes analytical investigations carried out on the impedance seen by distance relays by varying fault resistances and grid short circuit MVA, for the protection of such transmission lines during faults. The results are also compared with systems having conventional synchronous machine connected to the grid.

Factors influencing stick-slip motion: effect of hardness, crystal structure and surface texture

In the present investigation, efforts were made to study the different frictional responses of materials with varying crystal structure and hardness during sliding against a relatively harder material of different surface textures and roughness. In the experiments, pins were made of pure metals and alloys with significantly different hardness values. Pure metals were selected based on different class of crystal structures, such as face centered cubic (FCC), body centered cubic (BCC), body centered tetragonal (BCT) and hexagonal close packed (HCP) structures. The surface textures with varying roughness were generated on the counterpart plate which was made of H-11 die steel. The experiments were conducted under dry and lubricated conditions using an inclined pin-on-plate sliding tester for various normal loads at ambient environment. In the experiments, it was found that the coefficient of friction is controlled by the surface texture of the harder mating surfaces. Further, two kinds of frictional response, namely steady-state and stick-slip, were observed during sliding. More specifically, stead-state frictional response was observed for the FCC metals, alloys and materials with higher hardness. Stick-slip frictional response was observed for the metals which have limited number of slip systems such as BCT and HCP. In addition, the stick-slip frictional response was dependent on the normal load, lubrication, hardness and surface texture of the counterpart material. However, for a given kind of surface texture, the roughness of the surface affects neither the average coefficient of friction nor the amplitude of stick-slip oscillation significantly.

Identification of fault location in power distribution system with distributed generation using support vector machines

This paper presents a multi-class support vector machine (SVMs) approach for locating and diagnosing faults in electric power distribution feeders with the penetration of Distributed Generations (DGs). The proposed approach is based on the three phase voltage and current measurements which are available at all the sources i.e. substation and at the connection points of DG. To illustrate the proposed methodology, a practical distribution feeder emanating from 132/11kV-grid substation in India with loads and suitable number of DGs at different locations is considered. To show the effectiveness of the proposed methodology, practical situations in distribution systems (DS) such as all types of faults with a wide range of varying fault locations, source short circuit (SSC) levels and fault impedances are considered for studies. The proposed fault location scheme is capable of accurately identify the fault type, location of faulted feeder section and the fault impedance. The results demonstrate the feasibility of applying the proposed method in practical in smart grid distribution automation (DA) for fault diagnosis.

EFFECT OF OFF-STOICHIOMETRY AND TERNARY ADDITIONS ON PLANAR FAULT ENERGIES IN Ni3Al

First principles calculations were done to evaluate the lattice parameter, cohesive energy and stacking fault energies of ordered gamma' (Ll(2)) precipitates in superalloys as a function of composition. It was found that addition of Ti and Ta lead to an increase in lattice parameter and decrease in cohesive energy, while Ni antisites had the opposite effect. Ta and Ti addition to stoichiometric Ni3Al resulted in an initial increase in the energies of APB((111)), CSF(111), APB((001)) and SISF(111). However, at higher concentrations, the fault energies decreased. Addition of Ni antisites decreased the energy of all four faults monotonically. A model based on nearest neighbor bonding was used for Ni-3(Al, Ta), Ni-3(Al, Ti) and Ni-3(Al, Ni) pseudo-binary systems and extended to pseudo- ternary Ni-3(Al, Ta, Ni) and Ni-3(Al, Ti, Ni) systems. Recipes were developed for predicting lattice parameters, cohesive energies and fault energies in pseudo- ternary systems on the basis of coefficients derived from simpler pseudobinary systems. The model predictions were found to be in good agreement with first principles calculations for lattice parameters, cohesive energies, and energies of APB((111)) and CSF(111).