Two loop detection mechanisms: a comparison

In order to compare two loop detection mechanisms we describe two calculi for theorem proving in intuitionistic propositional logic. We call them both MJ Hist, and distinguish between them by description as `Swiss' or `Scottish'. These calculi combine in different ways the ideas on focused proof search of Herbelin and Dyckhoff & Pinto with the work of Heuerding emphet al on loop detection. The Scottish calculus detects loops earlier than the Swiss calculus but at the expense of modest extra storage in the history. A comparison of the two approaches is then given, both on a theoretic and on an implementational level

Cut-elimination for the modal Grzegorczyk logic via non-well-founded proofs

We present a sequent calculus for the modal Grzegorczyk logic Grz allowing non-well-founded proofs and obtain the cut-elimination theorem for it by constructing a continuous cut-elimination mapping acting on these proofs.Comment: WOLLIC'17, 12 pages, 1 appendi

Proof search in constructive logics

We present an overview of some sequent calculi organised not for "theorem-proving" but for proof search, where the proofs themselves (and the avoidance of known proofs on backtracking) are objects of interest. The main calculus discussed is that of Herbelin [1994] for intuitionistic logic, which extends methods used in hereditary Harrop logic programming; we give a brief discussion of similar calculi for other logics. We also point out to some related work on permutations in intuitionistic Gentzen sequent calculi that clarifies the relationship between such calculi and natural deduction.Centro de Matemática da Universidade do Minho (CMAT).União Europeia (UE) - Programa ESPRIT - BRA 7232 Gentzen

Cut-elimination and a permutation-free sequent calculus for intuitionistic logic

We describe a sequent calculus, based on work of Herbelin's, of which the cut-free derivations are in 1-1 correspondence with normal natural deduction proofs of intuitionistic logic. We present a simple proof of Herbelin's strong cut-elimination theorem for the calculus, using the recursive path oredering theorem of Dershowitz.Junta Nacional de Investigação Científica e Tecnológica (JNICT).União Europeia (UE) - Programa ESPRIT - grant BRA 7232 GENTZEN

Loop-free construction of counter-models for intuitionistic propositional logic

We present a non-looping method to construct Kripke trees refuting the non-theorems of intuitionistic propositional logic, using a contraction-free sequent calculus.União Europeia (UE) - project ESPRIT BRA 7232 GENTZEN.Junta Nacional de Investigação Científica e Tecnológica (JNICT)

О контактной прочности эвольвентных зубчатых передач

Приведены результаты численного моделирования контактного взаимодействия зубьев эвольвентной прямозубой зубчатой передачи при перекосах осей зубчатых колес. Показано отсутствие дополнительного (помимо известного герцевского) влияния приведенного радиуса кривизны контактирующих поверхностей на нагрузочную способность контакта, что опровергает данные, содержащиеся в некоторых литературных источниках. Установлено, что расчет контактной прочности эвольвентных передач по стандартной методике дает заниженные показатели по напряжениям и завышенные по нагрузочной способности в сравнении с результатами, полученными на расчетной модели.The computer simulation results for contact interaction of the spur involute gearing teeth at skewness of axes of the gear wheels are present. The absence of additional influence (besides known Hertz one) of the reduced principal curvature radius for contacting surfaces on the load-carrying capacity of the contact is shown. That disproves data of some references. It is stated that a calculation of contact strength of the involute gearing, based on the standard method, leads to decreased results on stresses and to increased results on load-carrying capacity by comparing with the data obtained in the numerical model

<i>“We’re Seeking Relevance”</i>: Qualitative Perspectives on the Impact of Learning Analytics on Teaching and Learning

Whilst a significant body of learning analytics research tends to focus on impact from the perspective of usability or improved learning outcomes, this paper proposes an approach based on Affordance Theory to describe awareness and intention as a bridge between usability and impact. 10 educators at 3 European institutions participated in detailed interviews on the affordances they perceive in using learning analytics to support practice in education. Evidence illuminates connections between an educator’s epistemic beliefs about learning and the purpose of education, their perception of threats or resources in delivering a successful learning experience, and the types of data they would consider as evidence in recognising or regulating learning. This evidence can support the learning analytics community in considering the proximity to the student, the role of the educator, and their personal belief structure in developing robust analytics tools that educators may be more likely to use

A change in the study evaluation paradigm reveals that larynx preservation compromises survival in T4 laryngeal cancer patients

Background: Larynx preservation (LP) is recommended for up to low-volume T4 laryngeal cancer as an evidence-based treatment option that does not compromise survival. However, a reevaluation of the current literature raises questions regarding whether there is indeed reliable evidence to support larynx preservation for T4 tumor patients. Methods: In an observational cohort study of 810 laryngeal cancer patients, we evaluated the outcomes of all T4 tumor patients treated with primary chemo-radiotherapy (CRT) or primary radiotherapy alone (RT) compared with upfront total laryngectomy followed by adjuvant (chemo)radiotherapy (TL + a[C]RT). Additionally, we reevaluated the studies that form the evidence base for the recommendation of LP for patients with up to T4 tumors (Pfister et al., J Clin Oncol 24:3693–704, 2006). Results: The evaluation of all 288 stage III and IV patients together did not show a significant difference in overall survival (OS) between CRT-LP and TL + a(C)RT (hazard ratio (HR) 1.23; 95% confidence interval (CI): 0.82–1.86; p = 0.31) using a multivariate proportional hazard model. However, a subgroup analysis of T4 tumor patients alone (N = 107; 13.9%) revealed significantly worse OS after CRT compared with TL + a(C)RT (HR 2.0; 95% CI: 1.04–3.7; p = 0.0369). A reevaluation of the subgroup of T4 patients in the 5 LP studies that led to the ASCO clinical practice guidelines revealed that only 21–45 T4 patients had differential data on survival outcome. These data, however, showed a markedly worse outcome for T4 patients after LP. Conclusions: T4 laryngeal cancer patients who reject TL as a treatment option should be informed that their chance of organ preservation with primary conservative treatment is likely to result in a significantly worse outcome in terms of OS. Significant loss of survival in T4 patients after LP is also confirmed in recent literature

Call-by-Value Lambda-calculus and LJQ

Accepté pour publication dans J. Logic Comput. ; 24 pagesLJQ is a focused sequent calculus for intuitionistic logic, with a simple restriction on the first premiss of the usual left introduction rule for implication. In a previous paper we discussed its history (going back to about 1950, or beyond) and presented its basic theory and some applications; here we discuss in detail its relation to call-by-value reduction in lambda calculus, establishing a connection between LJQ and the CBV calculus Lambda_C of Moggi. In particular, we present an equational correspondence between these two calculi forming a bijection between the two sets of normal terms, and allowing reductions in each to be simulated by reductions in the other

From Display to Labelled Proofs for Tense Logics

We introduce an effective translation from proofs in the display calculus to proofs in the labelled calculus in the context of tense logics. We identify the labelled calculus proofs in the image of this translation as those built from labelled sequents whose underlying directed graph possesses certain properties. For the basic normal tense logic Kt, the image is shown to be the set of all proofs in the labelled calculus G3Kt