Geometric Generalizations of the Power of Two Choices

A well-known paradigm for load balancing in distributed systems is the``power of two choices,''whereby an item is stored at the less loaded of two (or more) random alternative servers. We investigate the power of two choices in natural settings for distributed computing where items and servers reside in a geometric space and each item is associated with the server that is its nearest neighbor. This is in fact the backdrop for distributed hash tables such as Chord, where the geometric space is determined by clockwise distance on a one-dimensional ring. Theoretically, we consider the following load balancing problem. Suppose that servers are initially hashed uniformly at random to points in the space. Sequentially, each item then considers d candidate insertion points also chosen uniformly at random from the space,and selects the insertion point whose associated server has the least load. For the one-dimensional ring, and for Euclidean distance on the two-dimensional torus, we demonstrate that when n data items are hashed to n servers,the maximum load at any server is log log n / log d + O(1) with high probability. While our results match the well-known bounds in the standard setting in which each server is selected equiprobably, our applications do not have this feature, since the sizes of the nearest-neighbor regions around servers are non-uniform. Therefore, the novelty in our methods lies in developing appropriate tail bounds on the distribution of nearest-neighbor region sizes and in adapting previous arguments to this more general setting. In addition, we provide simulation results demonstrating the load balance that results as the system size scales into the millions.

Affective and Experiential Influences on English Skills of Heritage Spanish Speakers

Gemstone Team GABS (Grammar Acquisition in Bilingual Students)

Predicting the relationship between reliability and geometric parameters of cu column bumped flip-chips

Cu column bumping is a novel flip chip packaging technique that allows Cu columns to be bonded directly with the dies. It has eliminated the under-bump-metallurgy (UBM) fonnation step of the traditional flip chip manufacturing process. This bumping technique has the potential benefits of simplifying the flip chip manufacturing process, increasing productivity and the UO counts. In this paper, a study of reliability of Cu column bumped flip chips will be presented. Computer modelling methods have been used to predict the shape of solder joints and the response of flip chips to cyclic thermal-mechanical loading. The accumulated plastic strain energy at the corner solder joints has been used as an indicator of the solder joint reliability. Models with a wide range of design parameters have been compared for their reliability. The design parameters that have been investigated are the copper column height and radius, PCB pad radius, solder volume and Cu column wetting height. The relative importance ranking of these parameters has been obtained. The Lead-free solder material 96.5Sn3.5Ag has been used in this modelling work.

Putting down routes: an examination of local government cultural policy shaping the development of heritage trails

This paper explores the significance of trails within local government cultural strategies by presenting the results of an audit of 1000 trails, content analysis of local cultural strategies and a series of interviews with local government cultural officers. It highlights the growing sophistication of trails as flexible and multi-faceted products promising an array of social, environmental, cultural and economic benefits. However, key issues emerge as challenges for local government cultural officers. These include the need for a realistic assessment of the relative importance of competing rationales, the design of methodologies to enable evidence-based policy making and more effective engagement with commercial organisations.

Fact, fiction and nostalgia: an assessment of heritage interpretation at living museums

This paper aims to explore and discuss the role of nostalgia (a concept that is inherently grounded within a psychological framework) in heritage interpretation from both provider and consumer perspectives. Whilst many cultural practitioners recognise the relationship between sentimentality and authenticity, particularly within a folk-heritage context, few have sought to examine the effect this has on the visitor experience. This paper questions visitors’ ability to objectively assess objects and experiences at heritage sites, and the role of practitioners in presenting often blurred views of social history that may sometimes negate historical fact. Drawing on case study research at two UK living museums, Blists Hill Victorian Town in Shropshire, England, and the Big Pit: National Coal Museum in Wales, notions of reminiscence, authenticity, myth and intangibility are considered within the framework of the interpretive experience. Findings suggest that the visitor experience is inherently subjective, highly individual and that the concept of intangibility is integral to an understanding of the nostalgia-authenticity debate.

Molecular documentation of polyembryony and the micro-spatial dispersion of clonal sibships in the nine-banded armadillo, Dasypus novemcinctus.

A battery of allelic markers at highly polymorphic microsatellite loci was developed and employed to confirm genetically the clonal nature of sibships in nine-banded armadillos. This phenomenon of consistent polyembryony, otherwise nearly unknown among the vertebrates, then was capitalized upon to describe the micro-spatial distributions of numerous clonal sibships in a natural population of armadillos. Adult clonemates were significantly more dispersed than were juvenile sibs, suggesting limited opportunities for altruistic behavioral interactions among mature individuals. These results, and considerations of armadillo natural history, suggest that evolutionary explanations for polyembryony in this species may not reside in the kinds of ecological and kin selection theories relevant to some of the polyembryonic invertebrates. Rather, polyembryony in armadillos may be associated evolutionarily with other reproductive peculiarities of the species, including delayed uterine implantation of a single egg.

Modeling the geometric characteristics of five-dimensionally woven composites

An analytical modeling approach for the prediction of the geometric characteristics of five-dimensional (5D) woven composites has been formulated. The model is driven by readily available data including the weaving parameters and constituent material properties. The new model calculates the individual proportions of fiber in each direction, areal density, overall fiber volume fraction, and laminate thickness. This information is useful for the engineer in the design and manufacture of 5D woven composites. In addition the present model outputs the mathematical definition of the 5D woven composite unit cell, which could be implemented as the geometric input for a downstream analytical model that is capable of predicting the elastic stiffness of 5D woven composites. Input parameters have been sourced from existing published work and the subsequent predictions made by the model are compared with the available experimental data on 5D woven composites.

A geometric analysis of the effects of noise on Berry phase

In this work we describe the effect of classical and quantum noise on the Berry phase. It is not a topical review article but rather an overview of our work in this field aiming at giving a simple pictorial intuition of our results.

Dialogic Evidence: Documentation of Ephemeral Events

Performance and documentation have long been characterised as oppositional practices, separated by competing voices which argue the virtues of disappearance and reproducibility. In response to this state of affairs, the recently completed Dialogic Evidence project was designed to explore the possibility (and the limits) of a productive co-existence between performance and documentation practices. In this paper I reflect on this project’s processes and outcomes, particular highlighting the potential of social web technologies as a collaborative means to archive, discuss and remember live performance.

Optimizing geometric accuracy of four dimensional CT scans acquired using the wall and couch mounted Varian Real-Time Position Management camera systems

Objective:

The aim of this study was to identify sources of anatomical misrepresentation due to the location of camera mounting, tumour motion velocity and image processing artefacts in order to optimise the 4DCT scan protocol and improve geometrical-temporal accuracy.

A phantom with an imaging insert was driven with a sinusoidal superior-inferior motion of varying amplitude and period for 4DCT scanning. The length of a high density cube within the insert was measured using treatment planning software to determine the accuracy of its spatial representation. Scan parameters were varied including the tube rotation period and the cine time between reconstructed images. A CT image quality phantom was used to measure various image quality signatures under the scan parameters tested.

No significant difference in spatial accuracy was found for 4DCT scans carried out using the wall mounted or couch mounted camera for sinusoidal target motion. Greater spatial accuracy was found for 4DCT scans carried out using a tube rotation speed of 0.5s rather than 1.0s. The reduction in image quality when using a faster rotation speed was not enough to require an increase in patient dose.

4DCT accuracy may be increased by optimising scan parameters, including choosing faster tube rotation speeds. Peak misidentification in the recorded breathing trace leads to spatial artefacts and this risk can be reduced by using a couch mounted infrared camera.

This study explicitly shows that 4DCT scan accuracy is improved by scanning with a faster CT tube rotation speed.

The optimized geometric structure of the (0001) surface of α-Fe 2O3

A tridimensional model of α-Fe₂O₃ and models of (0001) and (1102) surfaces on it were built. Then the structural optimization of the (0001) surface was presented which explored the influence of the system scale and the terminal surface configuration. Four different models including two different system scale structures (MODEL□ and MODEL□) and two different terminal structures (MODEL□ and MODEL□) were analyzed in this paper. It was concluded that the boundary effect was more important in a smaller system in the structure optimization. And the Fe-terminated was more stable than the O-terminated structure which was agreed with the experiences, this structural model can be used in further work including the monatomic adsorption/desorption and the chemical reactions on this surface.