4,026 research outputs found
The effects of recreational activities on aquatic avifauna
Bibliography: pages 83-86.The Rietvlei wetland system, 10 km north of Cape Town, South Africa, supports 158 species of birds (Winterbottom,1960), and is the principal wetland for breeding waterbird numbers in the south-western Cape Province. It is an important collection, pairing and distribution centre prior to the breeding season. Emerging mudflats during evaporation in late summer are a major gathering point for waders before migratory departure. Increasing human pressure on open spaces is threatening this natural habitat of aquatic birds. For future waterbird conservation it is necessary to ascertain the impact of recreation and human disturbance in this area. Recreational activities on the northern of two dredged lakes in the northwestern corner of Rietvlei are therefore examined to investigate possible causal relationships between recreational activity and the numbers and behaviour of aquatic avifauna. Counts of waterbirds were carried out in the presence of people involved with various forms of recreational activity. These observations were made between February and May 1983. As a null hypothesis it is proposed that recreational activities on this lake and wetland system do not have a significant effect upon water birds in the area. The method used to test this hypothesis is based on statistical analysis by computer, with disturbance measured by means of correlation coefficients between recreational activities and bird numbers. The major findings (Chapter 5) and subsequent recommendations (Chapter 6) for waterbird conservation on the Rietvlei dredged lakes are presented, and proposals for further research in this field are suggested
Design of the CMS-CASTOR subdetector readout system by reusing existing designs
CASTOR is a cylindrical calorimeter with a length of 1.5m and a diameter of 60cm located at 14.3 meters from the CMS interaction point and covering the range in pseudorapidity corresponding to 5.1 < | eta | < 6.6. The CASTOR project was approved in the middle of 2007. Given the limited resources and time, developing a readout system from scratch was excluded. Here the final implementations of the readout chain, the considerations for the different choices as well as the performance of the installed equipment are discussed
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The Structural Integrity of Composite Materials and Long-Life Implementation of Composite Structures
Funder: University of CambridgeAbstract: Empirical or semi-empirical design methodologies at the macroscopic scale (structural level) can be supported and justified only by a fundamental understanding at the lower (microscopic) size scale through the physical model. Today structural integrity (SI) is thought as the optimisation of microstructure by controlling processing coupled with intelligent manufacturing of the material: to maximise mechanical performance and ensure reliability of the large scale structure; and to avoid calamity and misfortune. SI analysis provides quantitative input to the formulation of an appropriately balanced response to the problem. This article demonstrates that at the heart of the matter are those mechanisms of crack nucleation and growth that affect the structural integrity of the material: microscopic cracking events that are usually too small to observe and viewed only by microscopy
Optimizing egalitarian performance in the side-effects model of colocation for data center resource management
In data centers, up to dozens of tasks are colocated on a single physical
machine. Machines are used more efficiently, but tasks' performance
deteriorates, as colocated tasks compete for shared resources. As tasks are
heterogeneous, the resulting performance dependencies are complex. In our
previous work [18] we proposed a new combinatorial optimization model that uses
two parameters of a task - its size and its type - to characterize how a task
influences the performance of other tasks allocated to the same machine.
In this paper, we study the egalitarian optimization goal: maximizing the
worst-off performance. This problem generalizes the classic makespan
minimization on multiple processors (P||Cmax). We prove that
polynomially-solvable variants of multiprocessor scheduling are NP-hard and
hard to approximate when the number of types is not constant. For a constant
number of types, we propose a PTAS, a fast approximation algorithm, and a
series of heuristics. We simulate the algorithms on instances derived from a
trace of one of Google clusters. Algorithms aware of jobs' types lead to better
performance compared with algorithms solving P||Cmax.
The notion of type enables us to model degeneration of performance caused by
using standard combinatorial optimization methods. Types add a layer of
additional complexity. However, our results - approximation algorithms and good
average-case performance - show that types can be handled efficiently.Comment: Author's version of a paper published in Euro-Par 2017 Proceedings,
extends the published paper with addtional results and proof
The SoLid anti-neutrino detector's readout system
The SoLid collaboration have developed an intelligent readout system to
reduce their 3200 silicon photomultiplier detector's data rate by a factor of
10000 whilst maintaining high efficiency for storing data from anti-neutrino
interactions. The system employs an FPGA-level waveform characterisation to
trigger on neutron signals. Following a trigger, data from a space time region
of interest around the neutron will be read out using the IPbus protocol. In
these proceedings the design of the readout system is explained and results
showing the performance of a prototype version of the system are presented
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