Abstract
We describe the architecture of QuAKE (Quantum Advanced Key Exchanger), an experimental setup for quantum key distribution (QKD) over a free-space quantum channel based on the B92 protocol [1]. The system consists of a transmitter (Alice) and a receiver (Bob) that are connected through a free-space quantum channel over a distance of approximately 50 m, and are each driven by a field-programmable gate array (FPGA). The raw key shared by Alice and Bob is processed in four subsequent steps (i.e., sifting, channel estimation, key reconciliation and privacy amplification) which are implemented in Matlab. Finally, public discussion is implemented with the user datagram protocol (UDP) transport protocol running over the Internet protocol (IP) network protocol, while 802.11g underlies the physical layer transmission. © 2011 ACM.

Abstract
Image data from Earth Observation Satellites (EDS) were used to analyse mountain landscape changes in Northeast Portugal. Three Landsat images, from April 30th 1979, March 14th 1989 and May 29th 2002 were used. A supervised classification was performed for each image based on the radiometric information and the Normalised Difference Vegetation Index (NDVI). Eleven classes were selected considering the main land cover types in the region. The classification results showed high overall accuracy (above 92.5%) and kappa coefficient (above 0.91). Broadly, the range of dates of the Landsat images used allowed for the differentiation between classes. Nevertheless, some problems occurred in differentiating between classes of forest and shrub vegetation due to similar characteristics and vegetation conditions in some periods of the year, and also due to the effects of topographic shadows associated to mountain areas. Meadows and annual crops were the classes having greater changes from 1979 to 2002: meadows area increased 60% while annual crops decreased 43.5%. The increase in meadows area was likely due to policies supporting agroenvironmental conservation and autochthon bovine livestock production. Differently, the decrease in annual crops was likely due to the loss of economical competitiveness of main annual crops and to the rural population decrease and ageing, which favoured the replacement of arable lands by permanent meadows. These results may help developing policies and measures for sustainable management of traditional mountain rural landscapes.

Abstract

Abstract
This paper is on the short-term hydro scheduling (STHS) problem, particularly concerning a head-dependent cascaded hydro system. A mixed-integer quadratic programming approach is proposed for the STHS problem, considering not only head-dependency, but also discontinuous operating regions and discharge ramping constraints. Moreover, market uncertainty is introduced in the model via price scenarios, and risk-aversion is considered by limiting the volatility of the expected profit. Numerical results, based on one of the main Portuguese cascaded hydro systems, illustrate the proficiency of the proposed approach. Finally, conclusions are duly drawn. © 2011 IEEE.

Abstract
Spreadsheets are widely used and studies show that most of the existing ones contain non-trivial errors. To improve end-users productivity, recent research proposes the use of a model-driven engineering approach to spreadsheets. In this paper we conduct the first empirical study to assess the effectiveness and efficiency of this approach. A set of spreadsheet end users worked with two different model-based spreadsheets. We present and analyze here the results achieved. © 2011 Springer-Verlag.

Abstract