1,903 research outputs found
Complexity of Bradley-Manna-Sipma Lexicographic Ranking Functions
In this paper we turn the spotlight on a class of lexicographic ranking
functions introduced by Bradley, Manna and Sipma in a seminal CAV 2005 paper,
and establish for the first time the complexity of some problems involving the
inference of such functions for linear-constraint loops (without precondition).
We show that finding such a function, if one exists, can be done in polynomial
time in a way which is sound and complete when the variables range over the
rationals (or reals). We show that when variables range over the integers, the
problem is harder -- deciding the existence of a ranking function is
coNP-complete. Next, we study the problem of minimizing the number of
components in the ranking function (a.k.a. the dimension). This number is
interesting in contexts like computing iteration bounds and loop
parallelization. Surprisingly, and unlike the situation for some other classes
of lexicographic ranking functions, we find that even deciding whether a
two-component ranking function exists is harder than the unrestricted problem:
NP-complete over the rationals and -complete over the integers.Comment: Technical report for a corresponding CAV'15 pape
A Supervisory Control Algorithm Based on Property-Directed Reachability
We present an algorithm for synthesising a controller (supervisor) for a
discrete event system (DES) based on the property-directed reachability (PDR)
model checking algorithm. The discrete event systems framework is useful in
both software, automation and manufacturing, as problems from those domains can
be modelled as discrete supervisory control problems. As a formal framework,
DES is also similar to domains for which the field of formal methods for
computer science has developed techniques and tools. In this paper, we attempt
to marry the two by adapting PDR to the problem of controller synthesis. The
resulting algorithm takes as input a transition system with forbidden states
and uncontrollable transitions, and synthesises a safe and
minimally-restrictive controller, correct-by-design. We also present an
implementation along with experimental results, showing that the algorithm has
potential as a part of the solution to the greater effort of formal supervisory
controller synthesis and verification.Comment: 16 pages; presented at Haifa Verification Conference 2017, the final
publication is available at Springer via
https://doi.org/10.1007/978-3-319-70389-3_
Defining the content and delivery of an intervention to Change AdhereNce to treatment in BonchiEctasis (CAN-BE): a qualitative approach incorporating the Theoretical Domains Framework, behavioural change techniques and stakeholder expert panels
BACKGROUND: Low patient adherence to treatment is associated with poorer health outcomes in bronchiectasis. We sought to use the Theoretical Domains Framework (TDF) (a framework derived from 33 psychological theories) and behavioural change techniques (BCTs) to define the content of an intervention to change patients' adherence in bronchiectasis (Stage 1 and 2) and stakeholder expert panels to define its delivery (Stage 3). METHODS: We conducted semi-structured interviews with patients with bronchiectasis about barriers and motivators to adherence to treatment and focus groups or interviews with bronchiectasis healthcare professionals (HCPs) about their ability to change patients' adherence to treatment. We coded these data to the 12 domain TDF to identify relevant domains for patients and HCPs (Stage 1). Three researchers independently mapped relevant domains for patients and HCPs to a list of 35 BCTs to identify two lists (patient and HCP) of potential BCTs for inclusion (Stage 2). We presented these lists to three expert panels (two with patients and one with HCPs/academics from across the UK). We asked panels who the intervention should target, who should deliver it, at what intensity, in what format and setting, and using which outcome measures (Stage 3). RESULTS: Eight TDF domains were perceived to influence patients' and HCPs' behaviours: Knowledge, Skills, Beliefs about capability, Beliefs about consequences, Motivation, Social influences, Behavioural regulation and Nature of behaviours (Stage 1). Twelve BCTs common to patients and HCPs were included in the intervention: Monitoring, Self-monitoring, Feedback, Action planning, Problem solving, Persuasive communication, Goal/target specified:behaviour/outcome, Information regarding behaviour/outcome, Role play, Social support and Cognitive restructuring (Stage 2). Participants thought that an individualised combination of these BCTs should be delivered to all patients, by a member of staff, over several one-to-one and/or group visits in secondary care. Efficacy should be measured using pulmonary exacerbations, hospital admissions and quality of life (Stage 3). CONCLUSIONS: Twelve BCTs form the intervention content. An individualised selection from these 12 BCTs will be delivered to all patients over several face-to-face visits in secondary care. Future research should focus on developing physical materials to aid delivery of the intervention prior to feasibility and pilot testing. If effective, this intervention may improve adherence and health outcomes for those with bronchiectasis in the future
On Multiphase-Linear Ranking Functions
Multiphase ranking functions () were proposed as a means
to prove the termination of a loop in which the computation progresses through
a number of "phases", and the progress of each phase is described by a
different linear ranking function. Our work provides new insights regarding
such functions for loops described by a conjunction of linear constraints
(single-path loops). We provide a complete polynomial-time solution to the
problem of existence and of synthesis of of bounded depth
(number of phases), when variables range over rational or real numbers; a
complete solution for the (harder) case that variables are integer, with a
matching lower-bound proof, showing that the problem is coNP-complete; and a
new theorem which bounds the number of iterations for loops with
. Surprisingly, the bound is linear, even when the
variables involved change in non-linear way. We also consider a type of
lexicographic ranking functions, , more expressive than types
of lexicographic functions for which complete solutions have been given so far.
We prove that for the above type of loops, lexicographic functions can be
reduced to , and thus the questions of complexity of
detection and synthesis, and of resulting iteration bounds, are also answered
for this class.Comment: typos correcte
A triazole containing co-polymer for use as an electron transport material in multilayer LEDs
We report investigations into a poly(1,20-(10,13-didecyl)distyrylbenzene-co-1,2-[p-ethylphenyl)]triazole) (TRIDSB) electron transport material and its incorporation into single and multilayer LEDs. Multilayer devices have been investigated with poly(p-phenylenevinylene) (PPV) and poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene) as hole transport layers (HTLs). The incorporation of the polymer into an ITO/PPV/TRIDSB/Al LED facilitates electron injection into the hole transporting emissive layer and results in a ten fold increase in the external quantum efficiency for electroluminescence (EL) of the PPV layer from 0.008% to 0.08-0.1%. In an ITO/I-MEHPPV/TRIDSB/Al device the corresponding increase in the quantum efficiency for EL from the I-MEHPPV is fifty fold, from 0.002% to between 0.06-0.11%. The polymer has been shown to be thermally stable with no glass transition temperature or melting point detected within the range 25-250 degrees C
Ilinva: Using Abduction to Generate Loop Invariants
International audienceWe describe a system to prove properties of programs. The key feature of this approach is a method to automatically synthesize in-ductive invariants of the loops contained in the program. The method is generic, i.e., it applies to a large set of programming languages and application domains; and lazy, in the sense that it only generates invariants that allow one to derive the required properties. It relies on an existing system called GPiD for abductive reasoning modulo theories [14], and on the platform for program verification Why3 [16]. Experiments show evidence of the practical relevance of our approach
Changes of some Health Indicators in Patients with Type 2 Diabetes: A Prospective Study in three Community Pharmacies in Sharjah, United Arab Emirates
Aim: The study aimed to examine changes in some health indicators in people with type 2 diabetes mellitus, namely: reported self-care activity, health related quality of life, and patient opinion of the services provided by three community pharmacies in Sharjah, UAE. Method: A group of patients was followed over 24 months. Patients under investigation received reminders packages during the first three months of the study. No reminders were sent after 3 months after the study was underway. Repeated measures ANOVA were used to test differences between means over different periods. Results: All patients included in this study were found to have poor diet and exercise behavior at baseline. Three months into the study, more than 27% of the patients had acceptable diet, exercise, foot care and self-testing behavior. However, evaluation at six months and 24-months show that mean scores had almost returned to baseline levels. There were significant differences between the mean values of initial (baseline data) and final (at the end of the study) scores for general health (5.86, p = 0.001), vitality (5.25, p < 0.001), and role physical scales (3.81, p = 0.02). There was a significant (p < 0.001) 25% increase in the patients' perception of the ability of the pharmacist to assist in decreasing blood glucose level. Conclusion: Ongoing reminder packages are needed for continued progress in self-care activities and for achieving lasting changes in the behavior. Implementation of such a strategy through community pharmacies could help to improve patients' views of the quality of services received from these pharmacies and patient's quality of life, which should improve patient's drug therapy and reduce complications of diabetes
Treatment adherence and health outcomes in patients with bronchiectasis
BACKGROUND: We aimed to determine adherence to inhaled antibiotics, other respiratory medicines and airway clearance and to determine the association between adherence to these treatments and health outcomes (pulmonary exacerbations, lung function and Quality of Life Questionnaire-Bronchiectasis [QOL-B]) in bronchiectasis after 12 months. METHODS: Patients with bronchiectasis prescribed inhaled antibiotics for Pseudomonas aeruginosa infection were recruited into a one-year study. Participants were categorised as "adherent" to medication (medication possession ratio ≥80% using prescription data) or airway clearance (score ≥80% in the Modified Self-Reported Medication-Taking Scale). Pulmonary exacerbations were defined as treatment with a new course of oral or intravenous antibiotics over the one-year study. Spirometry and QOL-B were completed at baseline and 12 months. Associations between adherence to treatment and pulmonary exacerbations, lung function and QOL-B were determined by regression analyses. RESULTS: Seventy-five participants were recruited. Thirty-five (53%), 39 (53%) and 31 (41%) participants were adherent to inhaled antibiotics, other respiratory medicines, and airway clearance, respectively. Twelve (16%) participants were adherent to all treatments. Participants who were adherent to inhaled antibiotics had significantly fewer exacerbations compared to non-adherent participants (2.6 vs 4, p = 0.00) and adherence to inhaled antibiotics was independently associated with having fewer pulmonary exacerbations (regression co-efficient = -0.51, 95% CI [-0.81,-0.21], p < 0.001). Adherence to airway clearance was associated with lower QOL-B Treatment Burden (regression co-efficient = -15.46, 95% CI [-26.54, -4.37], p < 0.01) and Respiratory Symptoms domain scores (regression co-efficient = -10.77, 95% CI [-21.45; -0.09], p < 0.05). There were no associations between adherence to other respiratory medicines and any of the outcomes tested. Adherence to treatment was not associated with FEV1 % predicted. CONCLUSIONS: Treatment adherence is low in bronchiectasis and affects important health outcomes including pulmonary exacerbations. Adherence should be measured as part of bronchiectasis management and future research should evaluate bronchiectasis-specific adherence strategies
Validity-Guided Synthesis of Reactive Systems from Assume-Guarantee Contracts
Automated synthesis of reactive systems from specifications has been a topic
of research for decades. Recently, a variety of approaches have been proposed
to extend synthesis of reactive systems from proposi- tional specifications
towards specifications over rich theories. We propose a novel, completely
automated approach to program synthesis which reduces the problem to deciding
the validity of a set of forall-exists formulas. In spirit of IC3 / PDR, our
problem space is recursively refined by blocking out regions of unsafe states,
aiming to discover a fixpoint that describes safe reactions. If such a fixpoint
is found, we construct a witness that is directly translated into an
implementation. We implemented the algorithm on top of the JKind model checker,
and exercised it against contracts written using the Lustre specification
language. Experimental results show how the new algorithm outperforms JKinds
already existing synthesis procedure based on k-induction and addresses
soundness issues in the k-inductive approach with respect to unrealizable
results.Comment: 18 pages, 5 figures, 2 table
Decision Procedure for Entailment of Symbolic Heaps with Arrays
This paper gives a decision procedure for the validity of en- tailment of
symbolic heaps in separation logic with Presburger arithmetic and arrays. The
correctness of the decision procedure is proved under the condition that sizes
of arrays in the succedent are not existentially bound. This condition is
independent of the condition proposed by the CADE-2017 paper by Brotherston et
al, namely, one of them does not imply the other. For improving efficiency of
the decision procedure, some techniques are also presented. The main idea of
the decision procedure is a novel translation of an entailment of symbolic
heaps into a formula in Presburger arithmetic, and to combine it with an
external SMT solver. This paper also gives experimental results by an
implementation, which shows that the decision procedure works efficiently
enough to use
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