Approximation Algorithms for the Asymmetric Traveling Salesman Problem : Describing two recent methods

The paper provides a description of the two recent approximation algorithms for the Asymmetric Traveling Salesman Problem, giving the intuitive description of the works of Feige-Singh[1] and Asadpour et.al\ [2].\newline [1] improves the previous $O(\log n)$ approximation algorithm, by improving the constant from 0.84 to 0.66 and modifying the work of Kaplan et. al\ [3] and also shows an efficient reduction from ATSPP to ATSP. Combining both the results, they finally establish an approximation ratio of $\left(\frac{4}{3}+\epsilon \right)\log n$ for ATSPP,\ considering a small $\epsilon>0$,\ improving the work of Chekuri and Pal.[4]\newline Asadpour et.al, in their seminal work\ [2], gives an $O\left(\frac{\log n}{\log \log n}\right)$ randomized algorithm for the ATSP, by symmetrizing and modifying the solution of the Held-Karp relaxation problem and then proving an exponential family distribution for probabilistically constructing a maximum entropy spanning tree from a spanning tree polytope and then finally defining the thin-ness property and transforming a thin spanning tree into an Eulerian walk.\ The optimization methods used in\ [2] are quite elegant and the approximation ratio could further be improved, by manipulating the thin-ness of the cuts.Comment: 12 page

Dielectric and conductivity relaxation in mixtures of glycerol with LiCl

We report a thorough dielectric characterization of the alpha relaxation of glass forming glycerol with varying additions of LiCl. Nine salt concentrations from 0.1 - 20 mol% are investigated in a frequency range of 20 Hz - 3 GHz and analyzed in the dielectric loss and modulus representation. Information on the dc conductivity, the dielectric relaxation time (from the loss) and the conductivity relaxation time (from the modulus) is provided. Overall, with increasing ion concentration, a transition from reorientationally to translationally dominated behavior is observed and the translational ion dynamics and the dipolar reorientational dynamics become successively coupled. This gives rise to the prospect that by adding ions to dipolar glass formers, dielectric spectroscopy may directly couple to the translational degrees of freedom determining the glass transition, even in frequency regimes where usually strong decoupling is observed.Comment: 8 pages, 7 figure

March 2003

A long standing goal in image-based modeling and rendering is to capture a scene from camera images and construct a su#cient model to allow photo-realistic rendering of new views. With the confluence of computer graphics and vision, the combination of research on recovering geometric structure from un-calibrated cameras with modeling and rendering has yielded numerous new methods. Yet, many challenging issues remain to be addressed before a su#ciently general and robust system could be built to e.g. allow an average user to model their home and garden from cam-corder video

Has the Historian’s craft gone digital? Some observations from France

Since the end of the 1980s the historiographical context has changed considerably. Over the course of the last ten years, we have reached the “digital age” and computers as well as resources available via the Internet have become indispensable tools for all researchers. Be it for the stage of documentation or for actual writing, we are now living and working in a context where historians can no longer completely refuse all IT tools. As long as there are no solid, durable, large-scale training efforts to equip all historians with the skills to use the new and old IT tools, their potential is necessarily limited. While there have been studies on “researchers” in general and also on political scientists in particular, there has, to our knowledge, been no scientific study which would allow us to reach conclusions on the use of IT tools and digital resources by French historians. It is thus difficult to reach conclusions on a larger scale and we have decided to base our analysis on our own experience in order to consider what could be the transformations of the historian’s craft in the digital age. We will thus proceed first to a series of conclusions based on our activities in mediation (teaching and blogging), before proposing a typology of the principal evolutions. We will conclude with a certain number of propositions as far as training of historians is concerned