Discontinuous collocation methods and gravitational self-force applications

Numerical simulations of extereme mass ratio inspirals, the mostimportant sources for the LISA detector, face several computational challenges. We present a new approach to evolving partial differential equations occurring in black hole perturbation theory and calculations of the self-force acting on point particles orbiting supermassive black holes. Such equations are distributionally sourced, and standard numerical methods, such as finite-difference or spectral methods, face difficulties associated with approximating discontinuous functions. However, in the self-force problem we typically have access to full a-priori information about the local structure of the discontinuity at the particle. Using this information, we show that high-order accuracy can be recovered by adding to the Lagrange interpolation formula a linear combination of certain jump amplitudes. We construct discontinuous spatial and temporal discretizations by operating on the corrected Lagrange formula. In a method-of-lines framework, this provides a simple and efficient method of solving time-dependent partial differential equations, without loss of accuracy near moving singularities or discontinuities. This method is well-suited for the problem of time-domain reconstruction of the metric perturbation via the Teukolsky or Regge-Wheeler-Zerilli formalisms. Parallel implementations on modern CPU and GPU architectures are discussed.Comment: 29 pages, 5 figure

A crack-opening-dependent numerical model for self-healing cementitious materials

A new damage-healing model for self-healing cementitious materials is described. The model is formulated using results from a discrete ligament model and guided by the findings of a linked experimental study. Healing is simulated using the interaction of curing fronts propagating from opposing crack faces within a body of healing-agent. This approach accounts for the dependency of the healing response on the crack opening displacement (COD) and its rate. The new damage-healing cohesive-zone model is applied to an element with an embedded strong-discontinuity within a coupled finite-element code, which simulates healing-agent transport and mechanical behaviour. The model is validated using data from tests with different CODs and COD rates. The validations show that the coupled model represents the mechanical and flow behaviour of an autonomic self-healing system with good accuracy for a range of cracking configurations and load paths. Previous ar

Advancements in bacteria based self-healing concrete and the promise of modelling

In the last two decades self-healing of concrete through microbial based carbonate precipitation has emerged as a promising technology for making concrete structures more resilient and sustainable. Currently, progress in the field is achieved mainly through physical experiments, but their duration and cost are barriers to innovation and keep the number of large scale applications still very limited. Modelling and simulation of the phenomena underlying microbial based healing of concrete may provide a key to complement the experimental efforts, but their development is still in its infancy. In this review, we briefly present the field, introduce some key aspects emerged from the experiments, present the main ongoing developments in modelling and simulation of mineral and microbial systems, and discuss how their synergy may be accomplished to speed up progress in the near future

Health and Wealth

We present a hierarchical multimedia archive that can serve complex multimedia requests from tertiary storage. Requests can consist of multiple request units of streamed and non-streamed data. The request units can have arbitrary synchronization patterns. Our scheduler Promote-IT promotes data from tertiary to secondary storage with real-time guarantees. Promote-IT uses an on-line heuristic algorithm to compute feasible schedules and a separate ASAP dispatcher to increase the efficiency of the resource usage. The heuristic algorithm runs in polynomial time. Schedules are optimized to give short response times to incoming requests. Three major problems complicate this scheduling problem. First, the fragments of requested real-time data and their synchronization are unpredictable. Second, the medium switching times in tertiary storage are high, and the number of drives and robots is low compared to the number of removable media. Third, the shared resources in the tertiary storage system create resource contention problems

Reasons for Living and Suicide Ideation in Young Adults from Divorced and Non-Divorced Homes

The purpose of this study was to examine reasons for living in young adults (17 to 24) from divorced and non-divorced homes. Participants included 281 individuals (128 men, 153 women). Eighty-nine subjects were reared in divorced homes. The Reasons for Living Inventory, a Suicide Ideation Questionnaire, and a demographic questionnaire with items to assess age, gender, parental marital status, and various questions related to being reared in a divorced home were administered to all participants. Results of the study revealed a main effect for suicide ideation status on the total score of the RFL, with non-ideators reporting significantly higher reasons for living than ideators. No main effects were found for gender or parent marital status. Thus, the adaptive cognitive characteristics which are measured by the RFL were no different in young adults who were reared in divorced homes when compared to those reared in non-divorced homes