On phase transformation models for thermo-mechanically coupled response of Nitinol

Fully coupled thermomechanical models for Nitinol at the grain level are developed in this work to capture the inter-dependence between deformation and temperature under non-isothermal conditions. The martensite transformation equations are solved using a novel algorithm which imposes all relevant constraints on the volume fractions. The numerical implementation of the resulting models within the finite element method is effected by the monolithic solution of the momentum and energy equations. Validation of the models is achieved by means of thin-tube experiments at different strain rates.     

Adaptive multi-dimensional filters

In the present work, adaptive multi-dimensional filtering technique is proposed, which in addition to numerical stabilization, results in significant reduction of computational efforts. A criterion for adaptive filtering is proposed with algorithm provided. A new buffer domain technique based on adaptive filtering is developed and demonstrated for flow past a stationary cylinder for different Reynolds numbers. This technique also allows calculations in a reduced domain, showing another use of adaptive filtering. Rotary oscillation of a circular cylinder at different forcing parameters show excellent match with results in the literature, demonstrating potential benefits of adaptive filtering.     

Out-of-core Data Management for Path Tracing on Hybrid Resources

We present a software system that enables path-traced rendering of complex scenes. The system consists of two primary components: an application layer that implements the basic rendering algorithm, and an out-of-core scheduling and data-management layer designed to assist the application layer in exploiting hybrid computational resources (e.g., CPUs and GPUs) simultaneously. We describe the basic system architecture, discuss design decisions of the system's data-management layer, and outline an efficient implementation of a path tracer application, where GPUs perform functions such as ray tracing, shadow tracing, importance-driven light sampling, and surface shading. The use of GPUs speeds up the runtime of these components by factors ranging from two to twenty, resulting in a substantial overall increase in rendering speed. The path tracer scales well with respect to CPUs, GPUs and memory per node as well as scaling with the number of nodes. The result is a system that can render large complex scenes with strong performance and scalability.     

A miniature PTC thermistor based sensor element fabricated by tape casting technique

Miniature Positive Temperature Coefficient thermistors measuring around 4 mm×4 mm×0.3 mm have been prepared from semiconducting barium titanate by tape casting technique. Their performance as sensor elements for sensing of temperature and related parameters is far superior due to their miniature size and therefore very low thermal mass. These elements have considerably high signal-to-noise ratio and their response is also very fast.     

Locally Restorable Routing of Highly Variable Traffic

Two-phase routing, where traffic is first distributed to intermediate nodes before being routed to the final destination, has been recently proposed for handling widely fluctuating traffic without the need to adapt network routing to changing traffic. Preconfiguring the network in a traffic independent manner using two-phase routing simplifies network operation considerably. In this paper, we extend this routing scheme by providing resiliency against link failures through fast restoration along link backup detours. We view this as important progress towards adding carrier-class reliability to the robustness of the scheme so as to facilitate its future deployment in Internet Service Provider (ISP) networks. On the theoretical side, the main contribution of the paper is the development of linear programming based and fast combinatorial algorithms for two-phase routing with link restoration so as to minimize the maximum utilization of any link in the network, or equivalently, maximize the throughput. The algorithms developed are fully polynomial time approximation schemes (FPTAS)-for any given isin > 0, an FPTAS guarantees a solution that is within a (1 + isin)-factor of the optimum and runs in time polynomial in the input size and 1/isin. To the best of our knowledge, this is the first work in the literature that considers making the scheme resilient to link failures through preprovisioned fast restoration mechanisms. We evaluate the performance of link restoration (in terms of throughput) and compare it with that of unprotected routing. For our experiments, we use actual ISP network topologies collected for the Rocketfuel project and three research network topologies.     

Surface waves in fibre-reinforced anisotropic elastic media

The aim of this paper is to investigate surface waves in anisotropic fibre-reinforced solid elastic media. First, the theory of general surface waves has been derived and applied to study the particular cases of surface waves — Rayleigh, Love and Stoneley types. The wave velocity equations are found to be in agreement with the corresponding classical result when the anisotropic elastic parameters tends to zero. It is important to note that the Rayleigh type of wave velocity in the fibre-reinforced elastic medium increases to a considerable amount in comparison with the Rayleigh wave velocity in isotropic materials.     

Guaranteed Performance Routing of Unpredictable Traffic With Fast Path Restoration

Two-phase routing, where traffic is first distributed to intermediate nodes before being routed to the final destination, has been recently proposed for handling widely fluctuating traffic without the need to adapt network routing to changing traffic. Preconfiguring the network in a traffic-independent manner using two-phase routing simplifies network operation considerably. In this paper, we extend this routing scheme by providing resiliency against link failures through fast path restoration along disjoint end-to-end backup paths. We view this as important progress toward adding carrier-class reliability to the robustness of the scheme so as to facilitate its future deployment in Internet service provider (ISP) networks. On the theoretical side, the main contribution of the paper is the development of linear-programming-based and fast combinatorial algorithms for two-phase routing with fast path restoration so as to minimize the maximum utilization of any link in the network, or equivalently, maximize the throughput. The algorithms developed are fully polynomial time approximation schemes (FPTAS)-for any given epsiv > 0, an FPTAS guarantees a solution that is within a (1+epsiv)-factor of the optimum and runs in time polynomial in the input size and [ 1/(relax epsiv)]. To the best of our knowledge, this is the first work in the literature that considers making the scheme resilient to link failures through preprovisioned fast restoration mechanisms. We evaluate the performance of fast path restoration (in terms of throughput) and compare it to that of unprotected routing. For our experiments, we use actual ISP network topologies collected for the Rocketfuel project and three research network topologies.     

Coping with staffing delays in software project management: anexperimental investigation

A key factor in the management of software projects is the ability of the manager to handle delays in the hiring and assimilation of staff. This study examines how decision makers cope with staffing delays, and how their decisions affect the outcome of software projects. We report the findings of a laboratory experiment in which subjects managed a simulated software project that entailed delays in the hiring and/or assimilation of staff. The performance of the subjects was ascertained in terms of the cost incurred and time taken in completing the project. While decision makers performed poorly in the presence of delays in either hiring or assimilation, subjects who had to deal with delays in the assimilation of staff performed worse than those dealing with hiring delays. Subjects who had to contend with both hiring and assimilation delays performed considerably worse than those who had to cope with just one type of delay. We suggest process explanations for the results, and discuss the implications of the results for managing software projects     

Design and implementation of a novel power factor monitoring unit using discrete wavelet transform

Design and implementation of a novel on-line single-phase power factor measurement technique under non-sinusoidal and time-varying environments are presented. The proposed method expresses true power factor in terms of displacement and distortion power factors under certain significant facts, as defined in IEEE Std. 1459- 2000. The displacement power factor is evaluated using a unique digital signal-processing algorithm, whereas discrete wavelet transform (DWT) based multi-resolution analysis has been proposed for an accurate estimation of distortion power factor. An efficient algorithm to perform DWT in real time, using Texas Instruments TMS320VC5416 digital signal processor, has also been discussed. Illustrative laboratory test results confirm the validity and accurate performance of the proposed method for tracking true power factor under both static and dynamic situations.     

Multiscale finite element modeling of superelasticity in Nitinol polycrystals

An efficient method is proposed for modeling superelastic polycrystalline NiTi by solving a two-scale problem. The RVE size of the fine scale is determined using a statistics-based approach. Both problems are discretized in space using the finite element method and their communication is effected using MPI. Representative simulations illustrate the modeling capabilities of the proposed approach.