2,689 research outputs found
A Dynamic Profile Questions Approach to Mitigate Impersonation in Online Examinations
© The Author(s) 2018 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.Online examinations are an integral component of many online learning environments, which face many security challenges. Collusion is seen as a major security threat to such examinations, when a student invites a third party to impersonate or abet in a test. This work aims to strengthen the authentication of students via the use of dynamic profile questions. The study reported in this paper involved 31 online participants from five countries over a five-week period. The results of usability and security analysis are reported. The dynamic profile questions were more usable than both the text-based and image-based questions (p < 0.01). An impersonation abuse scenario was simulated using email and mobile phone. The impersonation attack via email was not successful, however, students were able to share answers to dynamic profile questions with a third party impersonator in real time, which resulted in 93% correct answers. The sharing of information via phone took place in real time during an online test and the response time of an impersonator was significantly different (p < 0.01) than a student. The study also revealed that a response time factor may be implemented to identify and report impersonation attacks.Peer reviewe
Stock Market Boom and the Productivity Gains of the 1990s
Together with a sense of entering a New Economy, the US experienced in the second half of the 1990s an economic expansion, a stock market boom, a financing boom for new firms and productivity gains. In this paper, we propose an interpretation of these events within a general equilibrium model with financial frictions and decreasing returns to scale in production. We show that the mere prospect of high future productivity growth can generate sizable gains in current productivity, as well as the other above mentioned events.
The superconductor-insulator transition in 2D dirty boson systems
Universal properties of the zero temperature superconductor-insulator
transition in two-dimensional amorphous films are studied by extensive Monte
Carlo simulations of bosons in a disordered medium. We report results for both
short-range and long-range Coulomb interactions for several different points in
parameter space. In all cases we observe a transition from a superconducting
phase to an insulating Bose glass phase. {}From finite-size scaling of our
Monte Carlo data we determine the universal conductivity and the
critical exponents at the transition. The result for bosons with long-range Coulomb interaction is roughly consistent
with experiments reported so far. We also find for bosons with short-range interactions.Comment: Revtex 3.0, 54 pages, 17 figures included, UBCTP-93-01
A survey on the use of relevance feedback for information access systems
Users of online search engines often find it difficult to express their need for information in the form of a query. However, if the user can identify examples of the kind of documents they require then they can employ a technique known as relevance feedback. Relevance feedback covers a range of techniques intended to improve a user's query and facilitate retrieval of information relevant to a user's information need. In this paper we survey relevance feedback techniques. We study both automatic techniques, in which the system modifies the user's query, and interactive techniques, in which the user has control over query modification. We also consider specific interfaces to relevance feedback systems and characteristics of searchers that can affect the use and success of relevance feedback systems
Generalizing Consistency and other Constraint Properties to Quantified Constraints
Quantified constraints and Quantified Boolean Formulae are typically much
more difficult to reason with than classical constraints, because quantifier
alternation makes the usual notion of solution inappropriate. As a consequence,
basic properties of Constraint Satisfaction Problems (CSP), such as consistency
or substitutability, are not completely understood in the quantified case.
These properties are important because they are the basis of most of the
reasoning methods used to solve classical (existentially quantified)
constraints, and one would like to benefit from similar reasoning methods in
the resolution of quantified constraints. In this paper, we show that most of
the properties that are used by solvers for CSP can be generalized to
quantified CSP. This requires a re-thinking of a number of basic concepts; in
particular, we propose a notion of outcome that generalizes the classical
notion of solution and on which all definitions are based. We propose a
systematic study of the relations which hold between these properties, as well
as complexity results regarding the decision of these properties. Finally, and
since these problems are typically intractable, we generalize the approach used
in CSP and propose weaker, easier to check notions based on locality, which
allow to detect these properties incompletely but in polynomial time
The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations
We discuss the theoretical bases that underpin the automation of the
computations of tree-level and next-to-leading order cross sections, of their
matching to parton shower simulations, and of the merging of matched samples
that differ by light-parton multiplicities. We present a computer program,
MadGraph5_aMC@NLO, capable of handling all these computations -- parton-level
fixed order, shower-matched, merged -- in a unified framework whose defining
features are flexibility, high level of parallelisation, and human intervention
limited to input physics quantities. We demonstrate the potential of the
program by presenting selected phenomenological applications relevant to the
LHC and to a 1-TeV collider. While next-to-leading order results are
restricted to QCD corrections to SM processes in the first public version, we
show that from the user viewpoint no changes have to be expected in the case of
corrections due to any given renormalisable Lagrangian, and that the
implementation of these are well under way.Comment: 158 pages, 27 figures; a few references have been adde
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