A Partially Reflecting Random Walk on Spheres Algorithm for Electrical Impedance Tomography

In this work, we develop a probabilistic estimator for the voltage-to-current map arising in electrical impedance tomography. This novel so-called partially reflecting random walk on spheres estimator enables Monte Carlo methods to compute the voltage-to-current map in an embarrassingly parallel manner, which is an important issue with regard to the corresponding inverse problem. Our method uses the well-known random walk on spheres algorithm inside subdomains where the diffusion coefficient is constant and employs replacement techniques motivated by finite difference discretization to deal with both mixed boundary conditions and interface transmission conditions. We analyze the global bias and the variance of the new estimator both theoretically and experimentally. In a second step, the variance is considerably reduced via a novel control variate conditional sampling technique

Socio-economic impacts of alternative GIN control practices. Project deliverable 11 (WP4)

This report is a deliverable (WP4) from the EU-funded PrOPara project. The PrOPara project aspires to i) assess existing knowledge from research, development and benchmarking studies on alternatives to parasite control on organic ruminant farms, ii) collecting novel data on disease prevalence, risk assessment analysis and parasite control measures, through monitoring (farm surveys and stakeholder participation studies), iii) performing cost-benefit analysis on alternative parasite control measures and iv) developing and delivering technical innovation to facilitate implementation of sustainable parasite control strategies. A combined approach of modelling and focus groups for feedback was employed to assess the economic impacts of alternative GIN control strategies in South West France and North East Scotland. This two step method allowed results from the survey and farm modelling to be used during workshops, which also addressed social factors explaining the uptake and acceptance of GIN practices to control parasites. An existing excel based farm model was adapted in order to estimate the economic impacts of a range of alternative GIN practices. The model was adapted using data from a typical farm for organic goat system in France (Occitanie and Auvergne-Rhône-Alpes Regions) and two organic sheep systems (lowland and upland) in Scotland. A structured workshop approach was utilised to address both the social and economic factors related to adoption of alternative GIN practices by farmers. To this purpose, we adapted the Structured Decision Making (SDM) approach commonly used for decisions taking (Gregory and Keeney 1994, Conroy, Barker et al. 2008, Ogden and Innes 2009, Gregory 2012, Johnson, Eaton et al. 2015, Fatorić and Seekamp 2017). Overall, the modelling and farmer feedback showed that control of GIN needs to be farm specific, to suit the individual characteristics of both the farm but also the beliefs of the farmer. The extension of withdrawal periods combined with resistance issues in France have led to the adoption of TST by some farmers, but others are less convinced of its efficiency. The farmers in Scotland seem to have adopted multiple strategies such as use of arable land and mixed grazing to keep GIN levels from severely affecting their profits. However, the diversity of opinions and calls by the French farmers in particular for more trials, shows there is still further work to understand this problem and develop more effective, sustainable solutions

PrOPara project workshop Focus Group Manual: Step-wise Approach (Project deliverable 10.(WP4))

This handbook is a deliverable (WP4) from the EU-funded PrOPara project. The PrOPara project aspires to i) assess existing knowledge from research, development and benchmarking studies on alternatives to parasite control on organic ruminant farms, ii) collecting novel data on disease prevalence, risk assessment analysis and parasite control measures, through monitoring (farm surveys and stakeholder participation studies), iii) performing cost-benefit analysis on alternative parasite control measures and iv) developing and delivering technical innovation to facilitate implementation of sustainable parasite control strategies. This handbook serves as a baseline to conduct workshops with stakeholders in France and Scotland. It provides the organisers with a structured approach on 8 steps. The implementation of this approach will allow identification of main alternative GIN practices according to stakeholders’ views, as well as analysing economic impacts and reasons for adopting them or not

On Disjoint hypercubes in Fibonacci cubes

The {\em Fibonacci cube} of dimension $n$, denoted as $\Gamma\_n$, is the subgraph of $n$-cube $Q\_n$ induced by vertices with no consecutive 1's. We study the maximum number of disjoint subgraphs in $\Gamma\_n$ isomorphic to $Q\_k$, and denote this number by $q\_k(n)$. We prove several recursive results for $q\_k(n)$, in particular we prove that $q\_{k}(n) = q\_{k-1}(n-2) + q\_{k}(n-3)$. We also prove a closed formula in which $q\_k(n)$ is given in terms of Fibonacci numbers, and finally we give the generating function for the sequence $\{q\_{k}(n)\}\_{n=0}^{ \infty}$

Investigating Performance and Usage of Input Methods for Soft Keyboard Hotkeys

Touch-based devices, despite their mainstream availability, do not support a unified and efficient command selection mechanism, available on every platform and application. We advocate that hotkeys, conventionally used as a shortcut mechanism on desktop computers, could be generalized as a command selection mechanism for touch-based devices, even for keyboard-less applications. In this paper, we investigate the performance and usage of soft keyboard shortcuts or hotkeys (abbreviated SoftCuts) through two studies comparing different input methods across sitting, standing and walking conditions. Our results suggest that SoftCuts not only are appreciated by participants but also support rapid command selection with different devices and hand configurations. We also did not find evidence that walking deters their performance when using the Once input method.Comment: 17+2 pages, published at Mobile HCI 202

A New Game Invariant of Graphs: the Game Distinguishing Number

The distinguishing number of a graph $G$ is a symmetry related graph invariant whose study started two decades ago. The distinguishing number $D(G)$ is the least integer $d$ such that $G$ has a $d$-distinguishing coloring. A distinguishing $d$-coloring is a coloring $c:V(G)\rightarrow\{1,...,d\}$ invariant only under the trivial automorphism. In this paper, we introduce a game variant of the distinguishing number. The distinguishing game is a game with two players, the Gentle and the Rascal, with antagonist goals. This game is played on a graph $G$ with a set of $d\in\mathbb N^*$ colors. Alternately, the two players choose a vertex of $G$ and color it with one of the $d$ colors. The game ends when all the vertices have been colored. Then the Gentle wins if the coloring is distinguishing and the Rascal wins otherwise. This game leads to define two new invariants for a graph $G$, which are the minimum numbers of colors needed to ensure that the Gentle has a winning strategy, depending on who starts. These invariants could be infinite, thus we start by giving sufficient conditions to have infinite game distinguishing numbers. We also show that for graphs with cyclic automorphisms group of prime odd order, both game invariants are finite. After that, we define a class of graphs, the involutive graphs, for which the game distinguishing number can be quadratically bounded above by the classical distinguishing number. The definition of this class is closely related to imprimitive actions whose blocks have size $2$. Then, we apply results on involutive graphs to compute the exact value of these invariants for hypercubes and even cycles. Finally, we study odd cycles, for which we are able to compute the exact value when their order is not prime. In the prime order case, we give an upper bound of $3$

Optimal accessing and non-accessing structures for graph protocols

An accessing set in a graph is a subset B of vertices such that there exists D subset of B, such that each vertex of V\B has an even number of neighbors in D. In this paper, we introduce new bounds on the minimal size kappa'(G) of an accessing set, and on the maximal size kappa(G) of a non-accessing set of a graph G. We show strong connections with perfect codes and give explicitly kappa(G) and kappa'(G) for several families of graphs. Finally, we show that the corresponding decision problems are NP-Complete

Complexity of Manipulating Sequential Allocation

Sequential allocation is a simple allocation mechanism in which agents are given pre-specified turns and each agents gets the most preferred item that is still available. It has long been known that sequential allocation is not strategyproof. Bouveret and Lang (2014) presented a polynomial-time algorithm to compute a best response of an agent with respect to additively separable utilities and claimed that (1) their algorithm correctly finds a best response, and (2) each best response results in the same allocation for the manipulator. We show that both claims are false via an example. We then show that in fact the problem of computing a best response is NP-complete. On the other hand, the insights and results of Bouveret and Lang (2014) for the case of two agents still hold