150,653 research outputs found

    A study of the research done on the gifted child from 1952 to the present day.

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    Thesis (Ed.M.)--Boston Universit

    Why We Cannot (Yet) Ensure the Cybersecurity of Safety-Critical Systems

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    There is a growing threat to the cyber-security of safety-critical systems. The introduction of Commercial Off The Shelf (COTS) software, including Linux, specialist VOIP applications and Satellite Based Augmentation Systems across the aviation, maritime, rail and power-generation infrastructures has created common, vulnerabilities. In consequence, more people now possess the technical skills required to identify and exploit vulnerabilities in safety-critical systems. Arguably for the first time there is the potential for cross-modal attacks leading to future ‘cyber storms’. This situation is compounded by the failure of public-private partnerships to establish the cyber-security of safety critical applications. The fiscal crisis has prevented governments from attracting and retaining competent regulators at the intersection of safety and cyber-security. In particular, we argue that superficial similarities between safety and security have led to security policies that cannot be implemented in safety-critical systems. Existing office-based security standards, such as the ISO27k series, cannot easily be integrated with standards such as IEC61508 or ISO26262. Hybrid standards such as IEC 62443 lack credible validation. There is an urgent need to move beyond high-level policies and address the more detailed engineering challenges that threaten the cyber-security of safety-critical systems. In particular, we consider the ways in which cyber-security concerns undermine traditional forms of safety engineering, for example by invalidating conventional forms of risk assessment. We also summarise the ways in which safety concerns frustrate the deployment of conventional mechanisms for cyber-security, including intrusion detection systems

    The origin of order in random matrices with symmetries

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    From Noether's theorem we know symmetries lead to conservation laws. What is left to nature is the ordering of conserved quantities; for example, the quantum numbers of the ground state. In physical systems the ground state is generally associated with `low' quantum numbers and symmetric, low-dimensional irreps, but there is no \textit{a priori} reason to expect this. By constructing random matrices with nontrivial point-group symmetries, I find the ground state is always dominated by extremal low-dimensional irreps. Going further, I suggest this explains the dominance of J=0 g.s. even for random two-body interactions.Comment: 5 figures; contribution to "Beauty in Physics" conference in honor of Francesco Iachello, May 2012, Cocoyoc, Mexic

    Tracing the evolution of nuclear forces under the similarity renormalization group

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    I examine the evolution of nuclear forces under the similarity renormalization group (SRG) using traces of the many-body configuration-space Hamiltonian. While SRG is often said to "soften" the nuclear interaction, I provide numerical examples which paint a complementary point of view: the primary effect of SRG, using the kinetic energy as the generator of the evolution, is to shift downward the diagonal matrix elements in the model space, while the off-diagonal elements undergo significantly smaller changes. By employing traces, I argue that this is a very natural outcome as one diagonalizes a matrix, and helps one to understand the success of SRG.Comment: 6 pages, 3 figures, 1 tabl
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