On Words with the Zero Palindromic Defect

We study the set of finite words with zero palindromic defect, i.e., words rich in palindromes. This set is factorial, but not recurrent. We focus on description of pairs of rich words which cannot occur simultaneously as factors of a longer rich word

Inclusive Anti-poaching? Exploring the Potential and Challenges of Community-based Anti-Poaching

As it is acknowledged that the largely (para)militarised approach to anti-poaching has its limitations, alternative approaches to conservation law enforcement are being sought. One alternative, what we call inclusive anti-poaching, focuses on including people from local communities in antipoaching initiatives. Using a case study of a community programme from southern Mozambique, located adjacent to South Africa’s Kruger National Park, we examine the potential of a community ranger initiative to move towards a more inclusive and sustainable approach to anti-poaching and conservation. While highlighting its challenges and potential drawbacks, we argue that including local people in conservation law enforcement efforts can help address poaching and the problematic aspects of current anti-poaching measures. However, to be a genuine and sustainable alternative, community ranger programmes must be part of a broader shift towards developing local wildlife economies that benefit local communities, as opposed to supporting pre-existing antipoaching interventions

Are suprapectineal quadrilateral surface buttressing plates performances superior to traditional fixation? A finite element analysis

Acetabular fractures have a high impact on patient’s quality of life, and because acetabular fractures are high energy injuries, they often co-occur with other pathologies such as damage to cartilage that could increase related morbidity; thus, it appears of primary importance developing reliable treatments for this disease. This work aims at the evaluation of the biomechanical performances of non-conservative treatments of acetabular fractures through a finite element approach. Two pelvic plates models (the standard suprapectineal plate—SPP, and a suprapectineal quadrilateral surface buttressing plate—SQBP) were analyzed when implanted on transverse or T-shaped fractures. The plates geometries were adapted to the specific hemipelvis, mimicking the bending action that the surgeon performs on the plate intraoperatively. Implemented models were tested in a single leg stance condition. The obtained results show that using the SQBP plate in transverse and T-shaped acetabular fractures generates lower bone stress if compared to the SPP plate. Interfragmentary movement analysis shows that the SQBP plate guarantees greater stability in transverse fractures. In conclusion, the SQBP plate seems worthy of further clinical analysis, having resulted as a promising option in the treatment of transverse and T-shaped acetabular fractures, able to reduce bone stress values and to get performances comparable, and in some cases superior, to traditional fixation

Sur le défaut palindromique des mots infinis

Lorsqu'on s'intéresse à l'étude de la structure combinatoire d'un mot infini w, une stratégie classique consiste à calculer sa fonction de complexité, c'est-à-dire à décrire le nombre de mots de longueur n qui apparaissent dans w, pour chaque entier n ≥ 0. Récemment, des chercheurs se sont intéressés à un raffinement de cette notion en introduisant la fonction de complexité palindromique: pour chaque entier n ≥ 0, nous calculons le nombre de palindromes de longueur n apparaissant dans w. Rappelons qu'un palindrome est un mot qui se lit de la même façon de gauche à droite que de droite à gauche (par exemple, "radar" et "ressasser" sont des palindromes de la langue française). La connaissance des palindromes apparaissant dans un mot permet de déduire de nombreuses informations précieuses sur sa structure. Par exemple, un mot admettant une infinité de palindromes préfixes est nécessairement récurrent (tout facteur apparaît une infinité de fois) et son langage est fermé sous l'opération miroir. D'autre part, nous étudions également les occurrences de facteurs antipalindromiques (une généralisation de la notion de palindrome), qui semblent naturellement en interaction avec les palindromes usuels. En particulier, nous décrivons les complexités palindromique et antipalindromique de quelques familles importantes de mots: les mots périodiques, les mots sturmiens, le mot de Thue-Morse et les suites de Rote. Dans un deuxième temps, nous étudions le défaut palindromique des mots finis et infinis. Il s'agit d'une mesure de "richesse" ou de "pauvreté" en palindromes des mots. Nous montrons en particulier que certains mots associés aux suites de Rote, à l'instar des mots sturmiens (Droubay, Justin et Pirillo, 2001), sont aussi pleins, c'est-à-dire qu'ils réalisent la complexité palindromique maximale, et nous établissons aussi des conditions sous lesquelles les mots périodiques sont pleins. Une section supplémentaire est consacrée à l'étude des lacunes du mot de Thue-Morse, qui admet une infinité de palindromes, mais dont le défaut est infini (c'est-à-dire qu'il possède une infinité de lacunes palindromiques). En dernier lieu, nous mentionnons quelques problèmes ouverts dans ce passionnant champ de recherche. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Combinatoire, Mots, Palindromes, Antipalindromes, Complexité, Défaut

Evaluation of building envelope retrofit techniques for reducing energy needs for space cooling.

One of the fastest growing sources of new energy demand is space cooling. According to EU-studies a four-fold growth in air-conditioned space is likely to take place between 1990 and 2020. The energy savings achievable in the end-use space cooling depend on a number of variables related to the building envelope, the plants and to some extent the behaviour of occupants. They are hence complex to evaluate and consequently often underrepresented in energy efficiency programmes and National Plans. This paper is based on some preliminary results of the IEE project KeepCool 2. It discusses in particular: a methodology for bottom-up assessment of the energy savings related to "sustainable summer comfort" solutions; reference base case building typologies are analyzed in 5 European climates, and dynamic simulations are used to calculate the reductions in the energy need for cooling which can be achieved by specific retrofit actions (e.g. additions of effective solar protections, increased thermal insulation, night ventilation, increase of active mass by PCM, low solar absorbance surfaces,...); situations where mechanical cooling can be avoided are evaluated using the Adaptive Comfort model, according to the norm EN 15251. case studies of buildings with good summer comfort and low energy consumption performances, according to the ten steps of the KC2 procedure. the analysis of case studies of "comfort policies" adopted by public and private bodies to ensure summer comfort with low energy consumption (commitments to give priority to heat load reductions instead of introducing mechanical cooling, relaxed dress codes, low thermal insulation chairs, local air velocity increase)

Repetitions in infinite palindrome-rich words

Rich words are characterized by containing the maximum possible number of distinct palindromes. Several characteristic properties of rich words have been studied; yet the analysis of repetitions in rich words still involves some interesting open problems. We address lower bounds on the repetition threshold of infinite rich words over 2 and 3-letter alphabets, and construct a candidate infinite rich word over the alphabet $\Sigma_2=\{0,1\}$ with a small critical exponent of $2+\sqrt{2}/2$. This represents the first progress on an open problem of Vesti from 2017.Comment: 12 page

An Optimal Algorithm for Tiling the Plane with a Translated Polyomino

We give a $O(n)$-time algorithm for determining whether translations of a polyomino with $n$ edges can tile the plane. The algorithm is also a $O(n)$-time algorithm for enumerating all such tilings that are also regular, and we prove that at most $\Theta(n)$ such tilings exist.Comment: In proceedings of ISAAC 201

Generalised Lyndon-Schützenberger Equations

We fully characterise the solutions of the generalised Lyndon-Schützenberger word equations $u_1 \cdots u_\ell = v_1 cdots v_m w_1 \cdots w_n$, where $u_i \in \{u, \theta(u)\}$ for all $1 \leq i \leq \ell$, $v_j \in \{v, \theta(v)\}$ for all $1 \leq j \leq m$, $w_k \in \{w, \theta(w)\}$ for all $1 \leq k ?\leq n$, and $\theta$ is an antimorphic involution. More precisely, we show for which $\ell$, $m$, and $n$ such an equation has only $\theta$-periodic solutions, i.e., $u$, $v$, and $w$ are in $\{t, \theta(t)\}^\ast$ for some word $t$, closing an open problem by Czeizler et al. (2011)