39,095 research outputs found
On a Mathematical Method for Discovering Relations Between Physical Quantities: a Photonics Case Study
Better than words: expressing feelings with foods in Mass Observation wartime diaries
This paper, based on the examination of selected wartime diaries from the Mass Observation Archive, tackles the expression of intimate feelings through food practices. Exploring personal testimonies, it presents how, during a time of scarcity and shortage, food becomes a precious accessory to express personal feelings and a supportive medium to demonstrate love or friendship to friends or loved ones, whomever and wherever they could be.
The result of this exploration, supported by various studies and reports on wartime emotions and human behaviours, shows how personal feelings were expressed by something better than words: valuable food. It also demonstrates to what extent the smallest emotional boundary can become vital when facing hard times through some examples of quite peculiar behaviours reported by the diarists.
From the gift of a piece of cheese to the sacrifice of the meat ration, this paper suggests that food practices can become a valuable indicator of personal feelings such as love and friendship, but also loneliness and anxiety
Compiling and securing cryptographic protocols
Protocol narrations are widely used in security as semi-formal notations to
specify conversations between roles. We define a translation from a protocol
narration to the sequences of operations to be performed by each role. Unlike
previous works, we reduce this compilation process to well-known decision
problems in formal protocol analysis. This allows one to define a natural
notion of prudent translation and to reuse many known results from the
literature in order to cover more crypto-primitives. In particular this work is
the first one to show how to compile protocols parameterised by the properties
of the available operations.Comment: A short version was submitted to IP
Finitary Deduction Systems
Cryptographic protocols are the cornerstone of security in distributed
systems. The formal analysis of their properties is accordingly one of the
focus points of the security community, and is usually split among two groups.
In the first group, one focuses on trace-based security properties such as
confidentiality and authentication, and provides decision procedures for the
existence of attacks for an on-line attackers. In the second group, one focuses
on equivalence properties such as privacy and guessing attacks, and provides
decision procedures for the existence of attacks for an offline attacker. In
all cases the attacker is modeled by a deduction system in which his possible
actions are expressed. We present in this paper a notion of finitary deduction
systems that aims at relating both approaches. We prove that for such deduction
systems, deciding equivalence properties for on-line attackers can be reduced
to deciding reachability properties in the same setting.Comment: 30 pages. Work begun while in the CASSIS Project, INRIA Nancy Grand
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Supernova Shock Breakout Through a Wind
The breakout of a supernova shock wave through the progenitor star's outer
envelope is expected to appear as an X-ray flash. However, if the supernova
explodes inside an optically-thick wind, the breakout flash is delayed. We
present a simple model for estimating the conditions at shock breakout in a
wind based on the general observable quantities in the X-ray flash lightcurve:
the total energy E_X, and the diffusion time after the peak, t_diff. We base
the derivation on the self-similar solution for the forward-reverse shock
structure expected for an ejecta plowing through a pre-existing wind at large
distances from the progenitor's surface. We find simple quantitative relations
for the shock radius and velocity at breakout. By relating the ejecta density
profile to the pre-explosion structure of the progenitor, the model can also be
extended to constrain the combination of explosion energy and ejecta mass. For
the observed case of XRO08109/SN2008D, our model provides reasonable
constraints on the breakout radius, explosion energy, and ejecta mass, and
predicts a high shock velocity which naturally accounts for the observed
non-thermal spectrum.Comment: Accepted for publication in MNRAS (v3: minor changes in the
discussion of XRO08109/SN2008D, conclusions unchanged
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