5,088 research outputs found
Buy, sell, or hold? A sense-making account of factors influencing trading decisions
We investigated the effects of news valence, the direction of trends in graphically presented price series, and the culture and personality of traders in a financial trading task. Participants were given 12 virtual shares of financial assets and asked to use price graphs and news items to maximize their returns by buying, selling, or holding each one. In making their decisions, they were influenced by properties of both news items and price series but they relied more on the former. Western participants had lower trading latencies and lower return dispersions than Eastern participants. Those with greater openness to experience had lower trading latencies. Participants bought more shares when they forecast that prices would rise but failed to sell more when they forecast that they would fall. These findings are all consistent with the view that people trading assets try to make sense of information by incorporating it within a coherent narrative
Non-Universal Fractional Quantum Hall States in a Quantum wire
The ground state as well as low-lying excitations in a 2D electron system in
strong magnetic fields and a parabolic potential is investigated by the
variational Monte Calro method. Trial wave functions analogous to the Laughlin
state are used with the power-law exponent as the variational parameter. Finite
size scaling of the excitation energy shows that the correlation function at
long distance is characterized by anon-universal exponent in sharp contrast to
the standard Laughlin state.The Laughlin-type state becomes unstable depending
on strength of the confining potential.Comment: 10 pages, REVTE
Geographic Variation in the Effects of Heat Exposure on Maximum Sprint Speed and Hsp70 Abundance in Populations of the Western Fence Lizard, Scelopolus occidentalis
We examined whether western fence lizards Sceloporus occidentalis
occurring in thermally divergent environments display differential
responses to high temperature in locomotor performance
and heat-shock protein (Hsp) expression. We measured
maximum sprint speed in S. occidentalis from four populations
at paired latitudes and elevations before and after exposure to
an experimental heat treatment and then quantified hind-limb
muscle Hsp70 expression. Lizards collected from northern or
high-elevation collection sites suffered a greater reduction in
sprint speed after heat exposure than lizards collected from
southern or low-elevation sites. In addition, lizards from northern
collection sites also exhibited an increase in Hsp70 expression
after heat exposure, whereas there was no effect of
heat exposure on Hsp70 expression in lizards from southern
collection sites. Across all groups, there was a negative relationship
between Hsp70 expression and sprint speed after thermal
stress. This result is significant because (a) it suggests that
an increase in Hsp70 alone cannot compensate for the immediate
negative effects of high-temperature exposure on sprint
speed and (b) it demonstrates a novel correlation between an
emergent property at the intersection of several physiological
systems (locomotion) and a cellular response (Hsp70 expression).
Ultimately, geographic variation in the effects of heat on
sprint speed may translate into differential fitness and population
viability during future increases in global air temperatures
Geographic Variation in the Effects of Heat Exposure on Maximum Sprint Speed and Hsp70 Abundance in Populations of the Western Fence Lizard, Scelopolus occidentalis
We examined whether western fence lizards Sceloporus occidentalis
occurring in thermally divergent environments display differential
responses to high temperature in locomotor performance
and heat-shock protein (Hsp) expression. We measured
maximum sprint speed in S. occidentalis from four populations
at paired latitudes and elevations before and after exposure to
an experimental heat treatment and then quantified hind-limb
muscle Hsp70 expression. Lizards collected from northern or
high-elevation collection sites suffered a greater reduction in
sprint speed after heat exposure than lizards collected from
southern or low-elevation sites. In addition, lizards from northern
collection sites also exhibited an increase in Hsp70 expression
after heat exposure, whereas there was no effect of
heat exposure on Hsp70 expression in lizards from southern
collection sites. Across all groups, there was a negative relationship
between Hsp70 expression and sprint speed after thermal
stress. This result is significant because (a) it suggests that
an increase in Hsp70 alone cannot compensate for the immediate
negative effects of high-temperature exposure on sprint
speed and (b) it demonstrates a novel correlation between an
emergent property at the intersection of several physiological
systems (locomotion) and a cellular response (Hsp70 expression).
Ultimately, geographic variation in the effects of heat on
sprint speed may translate into differential fitness and population
viability during future increases in global air temperatures
Automatic Abstraction in SMT-Based Unbounded Software Model Checking
Software model checkers based on under-approximations and SMT solvers are
very successful at verifying safety (i.e. reachability) properties. They
combine two key ideas -- (a) "concreteness": a counterexample in an
under-approximation is a counterexample in the original program as well, and
(b) "generalization": a proof of safety of an under-approximation, produced by
an SMT solver, are generalizable to proofs of safety of the original program.
In this paper, we present a combination of "automatic abstraction" with the
under-approximation-driven framework. We explore two iterative approaches for
obtaining and refining abstractions -- "proof based" and "counterexample based"
-- and show how they can be combined into a unified algorithm. To the best of
our knowledge, this is the first application of Proof-Based Abstraction,
primarily used to verify hardware, to Software Verification. We have
implemented a prototype of the framework using Z3, and evaluate it on many
benchmarks from the Software Verification Competition. We show experimentally
that our combination is quite effective on hard instances.Comment: Extended version of a paper in the proceedings of CAV 201
Towards improved forecasting for offshore wind turbine O&M transfers
Failure to adequately account for marine conditions can incur uncertainty in operation and maintenance costs for offshore renewable installations. Winter months with high potential for electricity generation coincide with the conditions where access for maintenance is most challenging. Advancing towards a demonstration of a strategic maintenance approach will assist in both reducing direct costs and associated initial project finance, while informing this with a better understanding of the impact of marine conditions could improve crew transfer vessel logistics and planning. This paper presents historical weather data close to East Anglia One Wind Farm for use in the development of vessel access models. The research provides a forecasting methodology for predicting wave directions at a site close to the wind farm. Improved ability to predict wave direction could improve existing and future modelling of the impact of marine conditions on the speed and fuel usage of vessels. Potential also exists for directional information to be utilised in scheduling transfer operations
Wind and wave directional transit time model for offshore wind operation and maintenance
Uncertainty in operation and maintenance costs of offshore renewable installations can be incurred through failure to properly account for marine conditions. One such area, vessel utilisation scheduling, requires accurate forecasts of wind and wave conditions to minimise charter costs as well as plant downtime. Additionally, fuel usage and auxiliary costs will increase with longer transfer times. Exploiting auxiliary offshore measurement data and its relation to accessibility constraints could reduce idle charter periods by allowing operatives to better anticipate prevailing site conditions. Existing models omit the effect of direction on operations and fail to account for the complex relations between dependent environmental variables which can impact on operations such as crew transfers, lifting and jacking operations. In this paper, a methodology for improving the forecasting of offshore conditions through incorporating distributed meteorological and marine observations at multiple timescales is presented. Advancing towards a demonstration of a strategic maintenance approach of this kind will assist in both reducing direct costs and associated initial project finance. The developed model will be beneficial to developers and operators as better forecasting of when conditions are suitable for maintenance could reduce costs, lost earnings and improve mobilisation of vessels and technicians
Using Flow Specifications of Parameterized Cache Coherence Protocols for Verifying Deadlock Freedom
We consider the problem of verifying deadlock freedom for symmetric cache
coherence protocols. In particular, we focus on a specific form of deadlock
which is useful for the cache coherence protocol domain and consistent with the
internal definition of deadlock in the Murphi model checker: we refer to this
deadlock as a system- wide deadlock (s-deadlock). In s-deadlock, the entire
system gets blocked and is unable to make any transition. Cache coherence
protocols consist of N symmetric cache agents, where N is an unbounded
parameter; thus the verification of s-deadlock freedom is naturally a
parameterized verification problem. Parametrized verification techniques work
by using sound abstractions to reduce the unbounded model to a bounded model.
Efficient abstractions which work well for industrial scale protocols typically
bound the model by replacing the state of most of the agents by an abstract
environment, while keeping just one or two agents as is. However, leveraging
such efficient abstractions becomes a challenge for s-deadlock: a violation of
s-deadlock is a state in which the transitions of all of the unbounded number
of agents cannot occur and so a simple abstraction like the one above will not
preserve this violation. In this work we address this challenge by presenting a
technique which leverages high-level information about the protocols, in the
form of message sequence dia- grams referred to as flows, for constructing
invariants that are collectively stronger than s-deadlock. Efficient
abstractions can be constructed to verify these invariants. We successfully
verify the German and Flash protocols using our technique
A simple abstraction of arrays and maps by program translation
We present an approach for the static analysis of programs handling arrays,
with a Galois connection between the semantics of the array program and
semantics of purely scalar operations. The simplest way to implement it is by
automatic, syntactic transformation of the array program into a scalar program
followed analysis of the scalar program with any static analysis technique
(abstract interpretation, acceleration, predicate abstraction,.. .). The
scalars invariants thus obtained are translated back onto the original program
as universally quantified array invariants. We illustrate our approach on a
variety of examples, leading to the " Dutch flag " algorithm
An implementation of Deflate in Coq
The widely-used compression format "Deflate" is defined in RFC 1951 and is
based on prefix-free codings and backreferences. There are unclear points about
the way these codings are specified, and several sources for confusion in the
standard. We tried to fix this problem by giving a rigorous mathematical
specification, which we formalized in Coq. We produced a verified
implementation in Coq which achieves competitive performance on inputs of
several megabytes. In this paper we present the several parts of our
implementation: a fully verified implementation of canonical prefix-free
codings, which can be used in other compression formats as well, and an elegant
formalism for specifying sophisticated formats, which we used to implement both
a compression and decompression algorithm in Coq which we formally prove
inverse to each other -- the first time this has been achieved to our
knowledge. The compatibility to other Deflate implementations can be shown
empirically. We furthermore discuss some of the difficulties, specifically
regarding memory and runtime requirements, and our approaches to overcome them
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