2,208 research outputs found
Preparation for an investigation of the thermal radiation characteristics and thermal conductivity of lunar material Final report, 1968
Vacuum system and chamber design, and thermal radiation and conductivity measurement techniques for lunar material investigation
How active is your real estate fund manager?
Using a holdings-based measure of active management termed the ‘Segment Active Share’, the paper documents that commercial real estate portfolios that are more active – i.e., have segment weights which are least like those of the index – have outperformed. Employing proprietary IPD data for 256 U.K. real estate funds over 2002-2011, we find that funds with high Segment Active Share on average outperformed the real estate market by 1.9% per year. These funds do not seem to take increased risk and their outperformance cannot be explained by fund size alone, though on average they are smaller funds.This paper was sponsored by Aberdeen Asset Management PLC and was independently written by the authors.This is the accepted manuscript of a paper published in the Journal of Alternative Investments (Cremers M, Lizieri C, Journal of Alternative Investments, 2015, 18, 22-36, doi:10.3905/jai.2015.18.1.022). The final version is available at http://dx.doi.org/10.3905/jai.2015.18.1.02
Iterative graph cuts for image segmentation with a nonlinear statistical shape prior
Shape-based regularization has proven to be a useful method for delineating
objects within noisy images where one has prior knowledge of the shape of the
targeted object. When a collection of possible shapes is available, the
specification of a shape prior using kernel density estimation is a natural
technique. Unfortunately, energy functionals arising from kernel density
estimation are of a form that makes them impossible to directly minimize using
efficient optimization algorithms such as graph cuts. Our main contribution is
to show how one may recast the energy functional into a form that is
minimizable iteratively and efficiently using graph cuts.Comment: Revision submitted to JMIV (02/24/13
Formal Analysis of V2X Revocation Protocols
Research on vehicular networking (V2X) security has produced a range of
security mechanisms and protocols tailored for this domain, addressing both
security and privacy. Typically, the security analysis of these proposals has
largely been informal. However, formal analysis can be used to expose flaws and
ultimately provide a higher level of assurance in the protocols.
This paper focusses on the formal analysis of a particular element of
security mechanisms for V2X found in many proposals: the revocation of
malicious or misbehaving vehicles from the V2X system by invalidating their
credentials. This revocation needs to be performed in an unlinkable way for
vehicle privacy even in the context of vehicles regularly changing their
pseudonyms. The REWIRE scheme by Forster et al. and its subschemes BASIC and
RTOKEN aim to solve this challenge by means of cryptographic solutions and
trusted hardware.
Formal analysis using the TAMARIN prover identifies two flaws with some of
the functional correctness and authentication properties in these schemes. We
then propose Obscure Token (OTOKEN), an extension of REWIRE to enable
revocation in a privacy preserving manner. Our approach addresses the
functional and authentication properties by introducing an additional key-pair,
which offers a stronger and verifiable guarantee of successful revocation of
vehicles without resolving the long-term identity. Moreover OTOKEN is the first
V2X revocation protocol to be co-designed with a formal model.Comment: 16 pages, 4 figure
Non-collaborative Attackers and How and Where to Defend Flawed Security Protocols (Extended Version)
Security protocols are often found to be flawed after their deployment. We
present an approach that aims at the neutralization or mitigation of the
attacks to flawed protocols: it avoids the complete dismissal of the interested
protocol and allows honest agents to continue to use it until a corrected
version is released. Our approach is based on the knowledge of the network
topology, which we model as a graph, and on the consequent possibility of
creating an interference to an ongoing attack of a Dolev-Yao attacker, by means
of non-collaboration actuated by ad-hoc benign attackers that play the role of
network guardians. Such guardians, positioned in strategical points of the
network, have the task of monitoring the messages in transit and discovering at
runtime, through particular types of inference, whether an attack is ongoing,
interrupting the run of the protocol in the positive case. We study not only
how but also where we can attempt to defend flawed security protocols: we
investigate the different network topologies that make security protocol
defense feasible and illustrate our approach by means of concrete examples.Comment: 29 page
The European Federation of Organisations for Medical Physics Policy Statement No. 6.1: Recommended Guidelines on National Registration Schemes for Medical Physicists
This EFOMP Policy Statement is an update of Policy Statement No. 6 first published in 1994. The present version takes into account the European Union Parliament and Council Directive 2013/55/EU that amends Directive 2005/36/EU on the recognition of professional qualifications and the European Union Council Directive 2013/59/EURATOM laying down the basic safety standards for protection against the dangers arising from exposure to ionising radiation. The European Commission Radiation Protection Report No. 174, Guidelines on Medical Physics Expert and the EFOMP Policy Statement No. 12.1, Recommendations on Medical Physics Education and Training in Europe 2014, are also taken into consideration. The EFOMP National Member Organisations are encouraged to update their Medical Physics registration schemes where these exist or to develop registration schemes taking into account the present version of this EFOMP Policy Statement (Policy Statement No. 6.1"Recommended Guidelines on National Registration Schemes for Medical Physicists")
HDSDF: Hybrid Directional and Signed Distance Functions for Fast Inverse Rendering
Implicit neural representations of 3D shapes form strong priors that areuseful for various applications, such as single and multiple view 3Dreconstruction. A downside of existing neural representations is that theyrequire multiple network evaluations for rendering, which leads to highcomputational costs. This limitation forms a bottleneck particularly in thecontext of inverse problems, such as image-based 3D reconstruction. To addressthis issue, in this paper (i) we propose a novel hybrid 3D objectrepresentation based on a signed distance function (SDF) that we augment with adirectional distance function (DDF), so that we can predict distances to theobject surface from any point on a sphere enclosing the object. Moreover, (ii)using the proposed hybrid representation we address the multi-view consistencyproblem common in existing DDF representations. We evaluate our novel hybridrepresentation on the task of single-view depth reconstruction and show thatour method is several times faster compared to competing methods, while at thesame time achieving better reconstruction accuracy.<br
In vivo "real-time" monitoring of glucose in the brain with an amperometric enzyme-based biosensor based on gold coated tungsten (W-Au) microelectrodes
Biosensors based on Pt or Pt/Ir based needle-type microelectrodes have been successfully employed for continuous in vivo real-time brain biomonitoring of biomarkers such as glutamate and glucose. However, when implanted, these biosensors often bend, thereby damaging its surface and degrading its bioanalytical properties. In addition, downscaling of Pt and Pt/Ir needle-type biosensors, to improve the spatial resolution and decrease tissue damage, is technically challenging. In that sense, we investigated whether the use of a material with low malleability, tungsten (W), coated with a highly conductive material, gold (Au) could be as an alternative for conventional needle-type based biosensors. Therefore, we developed implantable needle-type (50 tim 0) gold coated tungsten (W-Au) amperometric microbiosensors. First, we evaluated electrochemically, the ability of W-Au microelectrodes (50 tim 0) to continuously monitor changes in H2O2. After, we functionalized, using a layer-by-layer assembly, the surface of W-Au microelectrodes. First with permselective membrane(s) (Nafion and Nafion-PPD) and after with an enzymatic hydrogel, containing an enzyme selective for glucose (glucose oxidase). Both the enzyme loading and the applied potential were optimized and the performance of functionalized W-Au microelectrodes and fully assembled biosensors was evaluated electrochemically. Additionally, the surface of bare and functionalized microelectrodes was also characterized by imaging techniques (scanning electron microscopy). In vivo experiments revealed that, W-Au based glucose biosensors, were able to accurately monitor, in real-time, changes in brain glucose in response to relevant pharmacological challenges. (C) 2018 Elsevier B.V. All rights reserved
The European Federation of Organisations for Medical Physics Policy Statement No. 10.1: Recommended Guidelines on National Schemes for Continuing Professional Development of Medical Physicists
Continuing Professional Development (CPD) is vital to the medical physics profession if it is to embrace the pace of change occurring in medical practice. As CPD is the planned acquisition of knowledge, experience and skills required for professional practice throughout one's working life it promotes excellence and protects the profession and public against incompetence. Furthermore, CPD is a recommended prerequisite of registration schemes (Caruana et al. 2014 [1]; [2]) and is implied in the Council Directive 2013/59/EURATOM (EU BSS) [3] and the International Basic Safety Standards (BSS) [4]. It is to be noted that currently not all national registration schemes require CPD to maintain the registration status necessary to practise medical physics. Such schemes should consider adopting CPD as a prerequisite for renewing registration after a set period of time. This EFOMP Policy Statement, which is an amalgamation and an update of the EFOMP Policy Statements No. 8 and No. 10, presents guidelines for the establishment of national schemes for CPD and activities that should be considered for CPD
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