Teaching mathematics using the internet

This paper examines teachers\u27 use of the Internet in the teaching and learning of Mathematics. The study draws upon data collected via an online survey and interviews with six teachers. It reports on their beliefs, strategies for use and their perceptions on how it impacts on students and their learning of mathematics. Some comparisons are made between the ways teachers used the Internet.<br /

Astronomy in the Cloud: Using MapReduce for Image Coaddition

In the coming decade, astronomical surveys of the sky will generate tens of terabytes of images and detect hundreds of millions of sources every night. The study of these sources will involve computation challenges such as anomaly detection and classification, and moving object tracking. Since such studies benefit from the highest quality data, methods such as image coaddition (stacking) will be a critical preprocessing step prior to scientific investigation. With a requirement that these images be analyzed on a nightly basis to identify moving sources or transient objects, these data streams present many computational challenges. Given the quantity of data involved, the computational load of these problems can only be addressed by distributing the workload over a large number of nodes. However, the high data throughput demanded by these applications may present scalability challenges for certain storage architectures. One scalable data-processing method that has emerged in recent years is MapReduce, and in this paper we focus on its popular open-source implementation called Hadoop. In the Hadoop framework, the data is partitioned among storage attached directly to worker nodes, and the processing workload is scheduled in parallel on the nodes that contain the required input data. A further motivation for using Hadoop is that it allows us to exploit cloud computing resources, e.g., Amazon's EC2. We report on our experience implementing a scalable image-processing pipeline for the SDSS imaging database using Hadoop. This multi-terabyte imaging dataset provides a good testbed for algorithm development since its scope and structure approximate future surveys. First, we describe MapReduce and how we adapted image coaddition to the MapReduce framework. Then we describe a number of optimizations to our basic approach and report experimental results comparing their performance.Comment: 31 pages, 11 figures, 2 table

Home country effects of offshoring. A critical survey on empirical literature.

The International fragmentation of production processes is of rising importance. One part of this fragmentation involves the relocation of a production process from a home- to a new host country. This literature survey deals with the effects of such relocations on the home country. First of all, we try to conceptualize the terms and definitions most frequently used in this context which are "outsourcing", "offshore outsourcing" and "offshoring". Despite the fact that there is little textual documentation dealing directly with the phenomena of offshoring and offshore outsourcing we try to give an overview of possible empirical literature to which one can regard to. Including FDI literature we try to cover empirical literature which can provide helpful insight on the effects of a relocation to foreign countries on the home country in connection with wages, skill upgrading, prices, profits, taxes and unions. (author's abstract)Series: Discussion Papers SFB International Tax Coordinatio

Crossover Phenomena in the One-Dimensional SU(4) Spin-Orbit Model under Magnetic Fields

We study the one-dimensional SU(4) exchange model under magnetic fields, which is the simplest effective Hamiltonian in order to investigate the quantum fluctuations concerned with the orbital degrees of freedom in coupled spin-orbit systems. The Bethe ansatz approaches and numerical calculations using the density matrix renormalization group method are employed. The main concern of the paper is how the system changes from the SU(4) to the SU(2) symmetric limit as the magnetic field is increased. For this model the conformal field theory predicts an usual behavior: there is a jump of the critical exponents just before the SU(2) limit. For a finite-size system, however, the orbital-orbital correlation functions approach continuously to the SU(2) limit after interesting crossover phenomena. The crossover takes place in the magnetization range of 1/3 $\sim$ 1/2 for the system with 72 sites studied in this paper.Comment: 8 pages, 6 Postscript figures, REVTeX, submitted to Phys. Rev.