1,057 research outputs found
Consistency and heterogeneity of individual behavior under uncertainty
By using graphical representations of simple portfolio choice problems,
we generate a very rich data set to study behavior under uncertainty
at the level of the individual subject. We test the data for
consistency with the maximization hypothesis, and we estimate preferences
using a two-parameter utility function based on Faruk Gul
(1991). This specification provides a good interpretation of the data
at the individual level and can account for the highly heterogeneous
behaviors observed in the laboratory. The parameter estimates jointly
describe attitudes toward risk and allow us to characterize the distribution
of risk preferences in the population
A Short Counterexample Property for Safety and Liveness Verification of Fault-tolerant Distributed Algorithms
Distributed algorithms have many mission-critical applications ranging from
embedded systems and replicated databases to cloud computing. Due to
asynchronous communication, process faults, or network failures, these
algorithms are difficult to design and verify. Many algorithms achieve fault
tolerance by using threshold guards that, for instance, ensure that a process
waits until it has received an acknowledgment from a majority of its peers.
Consequently, domain-specific languages for fault-tolerant distributed systems
offer language support for threshold guards.
We introduce an automated method for model checking of safety and liveness of
threshold-guarded distributed algorithms in systems where the number of
processes and the fraction of faulty processes are parameters. Our method is
based on a short counterexample property: if a distributed algorithm violates a
temporal specification (in a fragment of LTL), then there is a counterexample
whose length is bounded and independent of the parameters. We prove this
property by (i) characterizing executions depending on the structure of the
temporal formula, and (ii) using commutativity of transitions to accelerate and
shorten executions. We extended the ByMC toolset (Byzantine Model Checker) with
our technique, and verified liveness and safety of 10 prominent fault-tolerant
distributed algorithms, most of which were out of reach for existing
techniques.Comment: 16 pages, 11 pages appendi
Static Code Verification Through Process Models
In this extended abstract, we combine two techniques for program verification: one is Hoare-style static verification, and the other is model checking of state transition systems. We relate the two techniques semantically through the use of a ghost variable. Actions that are performed by the program can be logged into this variable, building an event structure as its value. We require the event structure to grow incrementally by construction, giving it behavior suitable for model checking. Invariants specify a correspondence between the event structure and the program state. The combined power of model checking and static code verification with separation logic based reasoning, gives a new and intuitive way to do program verification. We describe our idea in a tool-agnostic way: we do not give implementation details, nor do we assume that the static verification tool to which our idea might apply is implemented in a particular way
Environmental Exposures and Invasive Meningococcal Disease: An Evaluation of Effects on Varying Time Scales
Invasive meningococcal disease (IMD) is an important cause of meningitis and bacteremia worldwide. Seasonal variation in IMD incidence has long been recognized, but mechanisms responsible for this phenomenon remain poorly understood. The authors sought to evaluate the effect of environmental factors on IMD risk in Philadelphia, Pennsylvania, a major urban center. Associations between monthly weather patterns and IMD incidence were evaluated using multivariable Poisson regression models controlling for seasonal oscillation. Short-term weather effects were identified using a case-crossover approach. Both study designs control for seasonal factors that might otherwise confound the relation between environment and IMD. Incidence displayed significant wintertime seasonality (for oscillation, Pâ<â0.001), and Poisson regression identified elevated monthly risk with increasing relative humidity (per 1% increase, incidence rate ratio = 1.04, 95% confidence interval: 1.004, 1.08). Case-crossover methods identified an inverse relation between ultraviolet B radiation index 1â4 days prior to onset and disease risk (odds ratio = 0.54, 95% confidence interval: 0.34, 0.85). Extended periods of high humidity and acute changes in ambient ultraviolet B radiation predict IMD occurrence in Philadelphia. The latter effect may be due to decreased pathogen survival or virulence and may explain the wintertime seasonality of IMD in temperate regions of North America
Do natural disasters open a window of opportunity for corruption?
This study explores the link between natural disasters and corruption at the local government. We examine whether a natural disaster affects official households more favorably than non-official households. We find that natural disasters decrease nonofficial household expenditures significantly, however have negligible effect on official household expenditures. Meanwhile, both kinds of households experience similar reduction in incomes, and have much the same disaster coping strategies. Together, the results imply that local officials may receive unobserved monetary compensation â we define as corruption - in the aftermath of natural disasters
Relative value to surgical patients and anesthesia providers of selected anesthesia related outcomes
BACKGROUND: Anesthesia side effects are almost inevitable in most situations. In order to optimize the anesthetic experience from the patient's viewpoint, it makes intuitive sense to attempt to avoid the side effects that the patient fears the most. METHODS: We obtained rankings and quantitative estimates of the relative importance of nine experiences that commonly occur after anesthesia and surgery from 109 patients prior to their surgery and from 30 anesthesiologists. RESULTS: Pain was the most important thing to avoid, and subjects allocated a median of 100 to avoiding it. Next came vomiting (10), urinary retention (2) and pruritus ($2). Avoiding blood transfusion, an awake anesthetic technique or postoperative somnolence was not given value by the group as a whole. Anesthesiologists valued perioperative experiences in the same way as patients. CONCLUSIONS: Our results are comparable with those of previous studies in the area, and suggest that patients can prioritize the perioperative experiences they wish to avoid during their perioperative care. Such data, if obtained in the appropriate fashion, would enable anesthetic techniques to be compared using decision analysis
Non-Zero Sum Games for Reactive Synthesis
In this invited contribution, we summarize new solution concepts useful for
the synthesis of reactive systems that we have introduced in several recent
publications. These solution concepts are developed in the context of non-zero
sum games played on graphs. They are part of the contributions obtained in the
inVEST project funded by the European Research Council.Comment: LATA'16 invited pape
The impact of relative position and returns on sacrifice and reciprocity: an experimental study using individual decisions
We present a comprehensive experimental design that makes it possible to characterize other-regarding preferences and their relationship to the decision makerâs relative position. Participants are faced with a large number of decisions involving variations in the trade-offs between own and otherâs payoffs, as well as in other potentially important factors like the decision makerâs relative position. We find that: (1) choices are responsive to the cost of helping and hurting others; (2) The weight a decision maker places on othersâ monetary payoffs depends on whether the decision maker is in an advantageous or disadvantageous relative position; and (3) We find no evidence of reciprocity of the type linked to menu-dependence. The results of a mixture-model estimation show considerable heterogeneity in subjectsâ motivations and confirm the absence of reciprocal motives. Pure selfish behavior is the most frequently observed behavior. Among the subjects exhibiting social preferences, social-welfare maximization is the most frequent, followed by inequality-aversion and by competitiveness
- âŠ