Power electronics options for large wind farm integration : VSC-based HVDC transmission

This paper describes the use of voltage source converter based HVDC transmission (VSC transmission) system for grid integration of large wind farms over long distance. The wind farms can be based on either doubly-fed induction generator (DFIG) or fixed speed induction generator (FSIG). The paper describes the operation principles and control strategies of the proposed system. Automatic power balancing during network AC fault is achieved without communication between the two converters. PSCAD/EMTDC simulations are presented to demonstrate the robust performance and to validate the proposed system during various operating conditions such as variations of generation and AC fault conditions. The proposed VSC transmission system has technical and economic advantages over a conventional AC connection for integrating large wind farms over long distanc

Integrating security and usability into the requirements and design process

According to Ross Anderson, 'Many systems fail because their designers protect the wrong things or protect the right things in the wrong way'. Surveys also show that security incidents in industry are rising, which highlights the difficulty of designing good security. Some recent approaches have targeted security from the technological perspective, others from the human–computer interaction angle, offering better User Interfaces (UIs) for improved usability of security mechanisms. However, usability issues also extend beyond the user interface and should be considered during system requirements and design. In this paper, we describe Appropriate and Effective Guidance for Information Security (AEGIS), a methodology for the development of secure and usable systems. AEGIS defines a development process and a UML meta-model of the definition and the reasoning over the system's assets. AEGIS has been applied to case studies in the area of Grid computing and we report on one of these

Do you knowdis? A user study of a knowledge discovery tool for organizations

Organisations today have no reliable way of ensuring that all employees are aware of information that may be relevant to their work. In this paper we report on a 2-year project in which we have iteratively designed, developed and tested a knowledge discovery system (KnowDis) for organizations. Early stages of our study revealed that, employees do not know what is available on the corporate intranet, or files and messages they have stored. KnowDis proactively fetches relevant information and displays it in an unobtrusive form; this increases employee awareness without disrupting their tasks. We discuss and characterize knowledge workers' email usage behavior. Our main study with 28 users of KnowDis-enhanced email showed it can improve the user experience and performance on information retrieval tasks for knowledge workers

Investigating loan applicants' perceptions of alternative data items and the effect of incentives on disclosure

Lenders use information about loan applicants to predict whether a person is a good or bad credit risk; however borrowers express reservations about disclosing their personal information. In this paper we describe the design of a study in which we try to identify which data items have bigger privacy costs for individuals and whether it is possible to adjust lenders' data collection procedures in order to improve the privacy of the borrowers while maintaining or improving the accuracy of risk assessment methods. We aim to explore whether consumers could be equitably encouraged to give different information than they do presently, by offering incentives for disclosures. These incentives are: an uncertain long term financial gain; a certain short term financial gain. We also explore an inequitable manipulation using peer pressure. The advantages and disadvantages of this methodological approach are also discussed

Accounting for Taste: Using profile similarity to improve recommender systems

Recommender systems have been developed to address the abundance of choice we face in taste domains (films, music, restaurants) when shopping or going out. However, consumers currently struggle to evaluate the appropriateness of recommendations offered. With collaborative filtering, recommendations are based on people's ratings of items. In this paper, we propose that the usefulness of recommender systems can be improved by including more information about recommenders. We conducted a laboratory online experiment with 100 participants simulating a movie recommender system to determine how familiarity of the recommender, profile similarity between decision-maker and recommender, and rating overlap with a particular recommender influence the choices of decision-makers in such a context. While familiarity in this experiment did not affect the participants' choices, profile similarity and rating overlap had a significant influence. These results help us understand the decision-making processes in an online context and form the basis for user-centered social recommender system design

Recent Observations of the Distribution of Woodchucks (Marmota monax) in Arkansas

During the last couple of decades, the distribution of the woodchuck (Marmota monax) appeared to be expanding southward in Arkansas (Tumlison et al. 2001). An increase in the frequency of new sightings led us to re-evaluate the present status of this species of squirrel in the state. The woodchuck is not easily confused with other mammals, therefore we sought records of sightings to update information about its distribution. Recent range expansion had been documented in southwestern Arkansas, so we placed notices in stores and advertised in local newspapers in that region to intensively seek new records of sightings from the public. Results of that effort, coupled with information gathered from a statewide survey of personnel of the Arkansas Game and Fish Commission, indicated that woodchucks are most common in the western Interior Highlands, and that the species apparently continues to expand its range southward in Arkansas