From Uncertainty Data to Robust Policies for Temporal Logic Planning

We consider the problem of synthesizing robust disturbance feedback policies for systems performing complex tasks. We formulate the tasks as linear temporal logic specifications and encode them into an optimization framework via mixed-integer constraints. Both the system dynamics and the specifications are known but affected by uncertainty. The distribution of the uncertainty is unknown, however realizations can be obtained. We introduce a data-driven approach where the constraints are fulfilled for a set of realizations and provide probabilistic generalization guarantees as a function of the number of considered realizations. We use separate chance constraints for the satisfaction of the specification and operational constraints. This allows us to quantify their violation probabilities independently. We compute disturbance feedback policies as solutions of mixed-integer linear or quadratic optimization problems. By using feedback we can exploit information of past realizations and provide feasibility for a wider range of situations compared to static input sequences. We demonstrate the proposed method on two robust motion-planning case studies for autonomous driving

Critical exponents of a three dimensional O(4) spin model

By Monte Carlo simulation we study the critical exponents governing the transition of the three-dimensional classical O(4) Heisenberg model, which is considered to be in the same universality class as the finite-temperature QCD with massless two flavors. We use the single cluster algorithm and the histogram reweighting technique to obtain observables at the critical temperature. After estimating an accurate value of the inverse critical temperature \Kc=0.9360(1), we make non-perturbative estimates for various critical exponents by finite-size scaling analysis. They are in excellent agreement with those obtained with the $4-\epsilon$ expansion method with errors reduced to about halves of them.Comment: 25 pages with 8 PS figures, LaTeX, UTHEP-28

A Swendsen-Wang update algorithm for the Symanzik improved sigma model

We study a generalization of Swendsen-Wang algorithm suited for Potts models with next-next-neighborhood interactions. Using the embedding technique proposed by Wolff we test it on the Symanzik improved bidimensional non-linear $\sigma$ model. For some long range observables we find a little slowing down exponent ($z \simeq 0.3$) that we interpret as an effect of the partial frustration of the induced spin model.Comment: Self extracting archive fil

Transition from van-der-Waals to H Bonds dominated Interaction in n-Propanol physisorbed on Graphite

Multilayer sorption isotherms of 1-propanol on graphite have been measured by means of high-resolution ellipsometry within the liquid regime of the adsorbed film for temperatures ranging from 180 to 260 K. In the first three monolayers the molecules are oriented parallel to the substrate and the growth is roughly consistent with the Frenkel-Halsey-Hill-model (FHH) that is obeyed in van-der-Waals systems on strong substrates. The condensation of the fourth and higher layers is delayed with respect to the FHH-model. The fourth layer is actually a bilayer. Furthermore there is indication of a wetting transition. The results are interpreted in terms of hydrogen-bridge bonding within and between the layers.Comment: 4 pages, 3 figure

Surgical dural tears: Prevalence and updated management protocol based on 1359 lumbar vertebra interventions

SummaryIntroductionThe dural tear is a dreaded complication of lumbar surgery.HypothesisOur management protocol has made it possible to deal with this problem effectively.Materials and methodsRetrospective review of 1359 patients operated between 2000 and 2010. In the event of dural tear, a therapeutic protocol was applied: suturing the dural wound if possible. A collagen patch lined with a layer of fibrin glue protected the suture. If the suture was considered tight, a non-aspirating drain was set up for 48h. In the other cases, no drain was set up. All the patients were left supine for 48h and they received intravenous antibiotics for the same duration. We analyzed the number and the type of breaches, the possibility of suturing, clinical symptoms (headache), and delayed complications (dural fistula or meningoceles).ResultsThe 1359 procedures included 23 dural tear complications (1.7%). The tears were often small in size and reparable. There were no late complications detected: no symptomatic fistula or meningocele. None of the patients had a second surgery.DiscussionThis protocol provided effective management of dural tears in lumbar surgery, with no application problems. We suggest a number of improvements: the use of the Valsalva maneuver to test the suturing, a stand-up test for the patient, and a systematic late MRI to detect meningoceles. There is no reason to change the other points in the protocol: suturing, controlled drainage for watertight wounds, no drainage for the non-watertight wounds, antibiotics, and supine bed rest position 48h.Level of evidenceLevel IV. Retrospective study

On the question of universality in \RPn and \On Lattice Sigma Models

We argue that there is no essential violation of universality in the continuum limit of mixed \RPn and \On lattice sigma models in 2 dimensions, contrary to opposite claims in the literature.Comment: 16 pages (latex) + 3 figures (Postscript), uuencode

Theoretical Analysis of Acceptance Rates in Multigrid Monte Carlo

We analyze the kinematics of multigrid Monte Carlo algorithms by investigating acceptance rates for nonlocal Metropolis updates. With the help of a simple criterion we can decide whether or not a multigrid algorithm will have a chance to overcome critial slowing down for a given model. Our method is introduced in the context of spin models. A multigrid Monte Carlo procedure for nonabelian lattice gauge theory is described, and its kinematics is analyzed in detail.Comment: 7 pages, no figures, (talk at LATTICE 92 in Amsterdam