Efficient management of backtracking in and-parallelism

A backtracking algorithm for AND-Parallelism and its implementation at the Abstract Machine level are presented: first, a class of AND-Parallelism models based on goal independence is defined, and a generalized version of Restricted AND-Parallelism (RAP) introduced as characteristic of this class. A simple and efficient backtracking algorithm for R A P is then discussed. An implementation scheme is presented for this algorithm which offers minimum overhead, while retaining the performance and storage economy of sequent ial implementations and taking advantage of goal independence to avoid unnecessary backtracking ("restricted intelligent backtracking"). Finally, the implementation of backtracking in sequential and AND-Parallcl systems is explained through a number of examples

An abstract machine for restricted and-parallel execution of logic programs

Although the sequential execution speed of logic programs has been greatly improved by the concepts introduced in the Warren Abstract Machine (WAM), parallel execution represents the only way to increase this speed beyond the natural limits of sequential systems. However, most proposed parallel logic programming execution models lack the performance optimizations and storage efficiency of sequential systems. This paper presents a parallel abstract machine which is an extension of the WAM and is thus capable of supporting ANDParallelism without giving up the optimizations present in sequential implementations. A suitable instruction set, which can be used as a target by a variety of logic programming languages, is also included. Special instructions are provided to support a generalized version of "Restricted AND-Parallelism" (RAP), a technique which reduces the overhead traditionally associated with the run-time management of variable binding conflicts to a series of simple run-time checks, which select one out of a series of compiled execution graphs

Dynamic modelling of meat plant energy systems : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology at Massey University

The objective of this study was to develop dynamic mathematical models of the major energy use and recovery operations within the New Zealand meat industry. Ordinary differential equation based models were developed for the five most common rendering systems, for hot water use, generation and storage, and for the refrigeration system. These cover about 90% of process heat use and about two-thirds of electricity demand. Each model was constructed so that ultimately it could be linked to the others to develop an integrated energy supply and demand model. Strong linkages to product flow were developed for the rendering models, but those for hot water and refrigeration are less developed, although there is no technological impediment. In developing the models for rendering it was assumed that cookers and dryers are perfectly mixed vessels and that time delays in materials transport are negligible. Model predictions could be improved by removing these assumptions, but taking into account the possible extent of data uncertainties, the present accuracy may be adequate for the overall meat plant energy model. A major consequence of the development of a hot water demand model was that areas of low efficiency were identified. By attention to equipment designs for hand tool sterilisers and cleanup systems substantial heat savings are possible. Although not tested, both the model for heat recovery and the model for hot water storage and supply are expected to be accurate as few major assumptions were required in their development. The main novel feature of the refrigeration model is that it treats the refrigeration applications in abstract terms rather than performing a room by room analysis. As a consequence data demands are lower than for refrigeration models which use a room-based approach, and the actual data needed are more easily obtainable. In spite of the lower data requirements good accuracy was demonstrated. The models developed will have major benefits to the NZ meat industry, initially as stand-alone entities, but later as an integrated package to help in reducing energy use

Creating proactive interference in immediate recall: building a dog from a dart, a mop and a fig

[Abstract]: Phonemic codes are accorded a privileged role in most current models of immediate serial recall, although their effects are apparent in short-term proactive interference (PI) effects as well. The current research looks at how assumptions concerning distributed representation and distributed storage involving both semantic and phonemic codes might be operationalized to produce PI in a short-term cued recall task. The four experiments reported here attempted to generate the phonemic characteristics of a non-rhyming, interfering foil from unrelated filler items in the same list. PI was observed when a rhyme of the foil was studied or when the three phonemes of the foil were distributed across three studied filler items. The results suggest that items in short-term memory are stored in terms of feature bundles and that all items are simultaneously available at retrieval

Storage of spatially specific threshold elevation

Abstract. The decay of several visual aftereffects may be prolonged by interposing a period of light-free or pattern-free viewing between adaptation and testing. We demonstrate that this storage phenomenon can be observed using the threshold elevation aftereffect that follows inspection of a high-contrast grating pattern. Control experiments comparing thresholds for vertical and horizontal gratings after adaptation to a vertical grating reveal that the stored aftereffect, like its unstored counterpart, is pattern-selective. Storage is equally pronounced with stimuli that are detected by pattern-analyzing or movement-analyzing visual channels. Unlike other aftereffects, the threshold-elevation aftereffect requires that the storage period be light-free; no storage is seen if a blank field is inspected between adaptation and testing. The results are discussed with respect to the nature of visual aftereffects, and possible cognitive or physiological models of storage.

Using Big Data Technologies with Earth Science Data in HDF5: HDF5 Scalable Solutions

HDF5 (Hierarchical Data Format 5) is open-source, high-performance software that consists of an abstract data model, library, and fileformat used for storing and managing extremely large and/or complex data collections. NASA Earth Observing System (EOS) Data and Information Systems use HDF5 as an archival format to store remote sensing data from EOS satellites. HDF5 is also used to store other types of Geoscience and Strophysical data, e.g., seismic data and data from Low-Frequency Array (LOFAR) radio telescopes. Data stored in HDF5 has reached tens of petabytes and is growing at an accelerated rate.With the growing amout of HDF5 Earth Science data to analyze and process, scientists need to adopt big data technologies including new storage paradigms such as cloud and object storage. To run models and perform data analysis they also need to utilizied efficient and diverse ways to access data, from high-performance computing's (HPC) Message Passing Interface (MPI) I/O and deep memory hierarchies (DMH) to non-HPC frameworks such as Apache Hadoop, Spark, and Drill. The HDF Group continually works to enable usage of big data technologies in HDF software

Comparative quasi-static mechanical characterization of fresh and stored porcine trachea specimens

Abstract: Tissues of the upper airways of critically ill patients are particularly vulnerable to mechanical damage associated with the use of ventilators. Ventilation is known to disrupt the structural integrity of respiratory tissues and their function. This damage contributes to the vulnerability of these tissues to infection. We are currently developing tissue models of damage and infection to the upper airways. As part of our studies, we have compared how tissue storage conditions affect mechanical properties of excised respiratory tissues using a quasi-static platform. Data presented here show considerable differences in mechanical responses of stored specimens compared to freshly excised specimens. These data indicate that implementation of storage and maintenance procedures that minimize rapid degradation of tissue structure are essential for retaining the material properties in our tissue trauma models

Vapor nucleation paths in lyophobic nanopores

Abstract.: In recent years, technologies revolving around the use of lyophobic nanopores gained considerable attention in both fundamental and applied research. Owing to the enormous internal surface area, heterogeneous lyophobic systems (HLS), constituted by a nanoporous lyophobic material and a non-wetting liquid, are promising candidates for the efficient storage or dissipation of mechanical energy. These diverse applications both rely on the forced intrusion and extrusion of the non-wetting liquid inside the pores; the behavior of HLS for storage or dissipation depends on the hysteresis between these two processes, which, in turn, are determined by the microscopic details of the system. It is easy to understand that molecular simulations provide an unmatched tool for understanding phenomena at these scales. In this contribution we use advanced atomistic simulation techniques in order to study the nucleation of vapor bubbles inside lyophobic mesopores. The use of the string method in collective variables allows us to overcome the computational challenges associated with the activated nature of the phenomenon, rendering a detailed picture of nucleation in confinement. In particular, this rare event method efficiently searches for the most probable nucleation path(s) in otherwise intractable, high-dimensional free-energy landscapes. Results reveal the existence of several independent nucleation paths associated with different free-energy barriers. In particular, there is a family of asymmetric transition paths, in which a bubble forms at one of the walls; the other family involves the formation of axisymmetric bubbles with an annulus shape. The computed free-energy profiles reveal that the asymmetric path is significantly more probable than the symmetric one, while the exact position where the asymmetric bubble forms is less relevant for the free energetics of the process. A comparison of the atomistic results with continuum models is also presented, showing how, for simple liquids in mesoporous materials of characteristic size of ca. 4nm, the nanoscale effects reported for smaller pores have a minor role. The atomistic estimates for the nucleation free-energy barrier are in qualitative accord with those that can be obtained using a macroscopic, capillary-based nucleation theory. Graphical abstract: [Figure not available: see fulltext.]