1,032 research outputs found
Post-spinel transformations and equation of state in ZnGa2O4: Determination at high-pressure by in situ x-ray diffraction
Room temperature angle-dispersive x-ray diffraction measurements on spinel
ZnGa2O4 up to 56 GPa show evidence of two structural phase transformations. At
31.2 GPa, ZnGa2O4 undergoes a transition from the cubic spinel structure to a
tetragonal spinel structure similar to that of ZnMn2O4. At 55 GPa, a second
transition to the orthorhombic marokite structure (CaMn2O4-type) takes place.
The equation of state of cubic spinel ZnGa2O4 is determined: V0 = 580.1(9) A3,
B0 = 233(8) GPa, B0'= 8.3(4), and B0''= -0.1145 GPa-1 (implied value); showing
that ZnGa2O4 is one of the less compressible spinels studied to date. For the
tetragonal structure an equation of state is also determined: V0 = 257.8(9) A3,
B0 = 257(11) GPa, B0'= 7.5(6), and B0''= -0.0764 GPa-1 (implied value). The
reported structural sequence coincides with that found in NiMn2O4 and MgMn2O4.Comment: 20 pages, 4 figures, 2 Table
Network-wide Configuration Synthesis
Computer networks are hard to manage. Given a set of high-level requirements
(e.g., reachability, security), operators have to manually figure out the
individual configuration of potentially hundreds of devices running complex
distributed protocols so that they, collectively, compute a compatible
forwarding state. Not surprisingly, operators often make mistakes which lead to
downtimes. To address this problem, we present a novel synthesis approach that
automatically computes correct network configurations that comply with the
operator's requirements. We capture the behavior of existing routers along with
the distributed protocols they run in stratified Datalog. Our key insight is to
reduce the problem of finding correct input configurations to the task of
synthesizing inputs for a stratified Datalog program. To solve this synthesis
task, we introduce a new algorithm that synthesizes inputs for stratified
Datalog programs. This algorithm is applicable beyond the domain of networks.
We leverage our synthesis algorithm to construct the first network-wide
configuration synthesis system, called SyNET, that support multiple interacting
routing protocols (OSPF and BGP) and static routes. We show that our system is
practical and can infer correct input configurations, in a reasonable amount
time, for networks of realistic size (> 50 routers) that forward packets for
multiple traffic classes.Comment: 24 Pages, short version published in CAV 201
Towards a large-area RPWELL detector: design optimization and performance
We present a new design and assembly procedure of a large-area gas-avalanche
Resistive-Plate WELL (RPWELL) detector. A prototype
was tested in muon beam at CERN-SPS, presenting improved
performances compared to previous ones: MIP detection efficiency over 96\% with
3\% uniformity across the entire detector area, a charge gain of
with a uniformity of 22\%, and discharge
probability below with a few single hotspots attributed to
production imperfections. These results pave the way towards further up-scaling
detectors of this kind
Eliciting Risk Preferences using Choice Lists
We study the effect of embedding pairwise choices between lotteries
within a choice list on measured risk attitude. Using an experiment with online
workers, we find that subjects choose the risky lottery rather than a sure payment
significantly more often when responding to a choice list. This behavior can be rationalized
by the interaction between non-expected utility and the random incentive
system, as suggested by Karni and Safra (1987)
From Social Data Mining to Forecasting Socio-Economic Crisis
Socio-economic data mining has a great potential in terms of gaining a better
understanding of problems that our economy and society are facing, such as
financial instability, shortages of resources, or conflicts. Without
large-scale data mining, progress in these areas seems hard or impossible.
Therefore, a suitable, distributed data mining infrastructure and research
centers should be built in Europe. It also appears appropriate to build a
network of Crisis Observatories. They can be imagined as laboratories devoted
to the gathering and processing of enormous volumes of data on both natural
systems such as the Earth and its ecosystem, as well as on human
techno-socio-economic systems, so as to gain early warnings of impending
events. Reality mining provides the chance to adapt more quickly and more
accurately to changing situations. Further opportunities arise by individually
customized services, which however should be provided in a privacy-respecting
way. This requires the development of novel ICT (such as a self- organizing
Web), but most likely new legal regulations and suitable institutions as well.
As long as such regulations are lacking on a world-wide scale, it is in the
public interest that scientists explore what can be done with the huge data
available. Big data do have the potential to change or even threaten democratic
societies. The same applies to sudden and large-scale failures of ICT systems.
Therefore, dealing with data must be done with a large degree of responsibility
and care. Self-interests of individuals, companies or institutions have limits,
where the public interest is affected, and public interest is not a sufficient
justification to violate human rights of individuals. Privacy is a high good,
as confidentiality is, and damaging it would have serious side effects for
society.Comment: 65 pages, 1 figure, Visioneer White Paper, see
http://www.visioneer.ethz.c
GUN: An Efficient Execution Strategy for Querying the Web of Data
International audienceLocal-As-View (LAV) mediators provide a uniform interface to a federation of heterogeneous data sources, attempting to execute queries against the federation. LAV mediators rely on query rewriters to translate mediator queries into equivalent queries on the federated data sources. The query rewriting problem in LAV mediators has shown to be NP-complete, and there may be an exponential number of rewritings, making unfeasible the execution or even generation of all the rewritings for some queries. The complexity of this problem can be particularly impacted when queries and data sources are described using SPARQL conjunctive queries, for which millions of rewritings could be generated. We aim at providing an efficient solution to the problem of executing LAV SPARQL query rewritings while the gathered answer is as complete as possible. We formulate the Result-Maximal k-Execution problem (ReMakE) as the problem of maximizing the query results obtained from the execution of only k rewritings. Additionally, a novel query execution strategy called GUN is proposed to solve the ReMakE problem. Our experimental evaluation demonstrates that GUN outperforms traditional techniques in terms of answer completeness and execution time
Efficient semi-static secure broadcast encryption scheme
In this paper, we propose a semi-static secure broadcast encryption scheme with constant-sized private keys and ciphertexts. Our result improves the semi-static secure broadcast encryption scheme introduced by Gentry and Waters. Specifically, we reduce the private key and ciphertext size by half. By applying the generic transformation proposed by Gentry and Waters, our scheme also achieves adaptive security. Finally, we present an improved implementation idea which can reduce the ciphertext size in the aforementioned generic transformation
Electronic structure and vibrational entropies of fcc Au-Fe alloys
Phonon density of states (DOS) curves were measured on alloys of face-centered-cubic (fcc) Au-Fe using nuclear resonant inelastic x-ray scattering (NRIXS) and inelastic neutron scattering (INS). The NRIXS and INS results were combined to obtain the total phonon DOS and the partial phonon DOS curves of Au and Fe atoms from which vibrational entropies were calculated. The main effect on the vibrational entropy of alloying comes from a stiffening of the Au partial phonon DOS with Fe concentration. Force constants were calculated from first principles for several compositions and show a local stiffening of Au-Au bonds close to Fe atoms. The calculated phonon DOS curves reproduce the experimental trend. The stiffening is attributed to two main effects comparable in magnitude: (i) an increase in electron density in the free-electron-like states and (ii) stronger sd hybridization
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