Graph Symmetry Detection and Canonical Labeling: Differences and Synergies

Symmetries of combinatorial objects are known to complicate search algorithms, but such obstacles can often be removed by detecting symmetries early and discarding symmetric subproblems. Canonical labeling of combinatorial objects facilitates easy equivalence checking through quick matching. All existing canonical labeling software also finds symmetries, but the fastest symmetry-finding software does not perform canonical labeling. In this work, we contrast the two problems and dissect typical algorithms to identify their similarities and differences. We then develop a novel approach to canonical labeling where symmetries are found first and then used to speed up the canonical labeling algorithms. Empirical results show that this approach outperforms state-of-the-art canonical labelers.Comment: 15 pages, 10 figures, 1 table, Turing-10

Symmetry in Finite Combinatorial Objects: Scalable Methods and Applications.

Symmetries of combinatorial objects are known to complicate search algorithms, but such obstacles can often be removed by detecting symmetries early and discarding symmetric subproblems. Canonical labeling of combinatorial objects facilitates easy equivalence checking through quick matching. All existing canonical-labeling software also finds symmetries, but the fastest symmetry-finding software does not perform canonical labeling. In this thesis, we describe highly scalable symmetry-detection algorithms for two widely-used combinatorial objects: graphs and Boolean functions. Our algorithms are based on a decision tree that combines elements of group-theoretic computation with branching and backtracking search. Moreover, we contrast the search for graph symmetries and a canonical labeling to dissect typical algorithms and identify their similarities and differences. We develop a novel approach to graph canonical labeling where symmetries are found first and then used to speed up the canonical-labeling routines. Empirical results are given for graphs with millions of vertices and Boolean functions with hundreds of I/Os, where our algorithms can often find all symmetry group generators or a canonical labeling in seconds.PHDComputer Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/100003/1/hadik_1.pd

In Vitro Comparison of the Effectiveness of Chlorhexidine and Two Calcium Hydroxide Formulations on Enterococcus Faecalis

INTRODUCTION: The aim of this in vitro study was to compare the effectiveness of three intracanal medicaments in disinfecting the root canal and dentin of experimentally infected human teeth with Enterococcus faecalis (EF). MATERIALS AND METHODS: One hundred extracted human single-rooted teeth were used. After root canal preparation, teeth were mounted in epoxy resin. Following sterilization, the teeth were infected for 28 days with EF. Then root canals were filled with one of three different disinfectants: viscous 2% Chlorhexidine (CHX), calcium hydroxide paste (CH) or a mixture of CH and CHX (n=30 in each group). Antimicrobial assessments were performed at 1, 3 and 7 days (n=10 in each time period). Microbial samples were obtained from root canals before and after the experiment. Also dentin samples were examined. The data was analyzed using Two- Way ANOVA test. RESULTS: The findings showed that there was no difference between experimental groups at different time periods. The mixture of CH/CHX in 7 days was able to eliminate EF completely from root canal system. The most elimination of EF was from dentinal tubules. CONCLUSION: According to the results of this in vitro study, viscous 2% CHX, mixture of CH with distilled water and 2% CHX are all effective disinfectants

The virtues of conflict

Modern shared memory multiprocessors permit reordering of memory operations for performance reasons. These reorderings are often a source of subtle bugs in programs written for such architectures. Traditional approaches to verify weak memory programs often rely on interleaving semantics, which is prone to state space explosion, and thus severely limits the scalability of the analysis. In recent times, there has been a renewed interest in modelling dynamic executions of weak memory programs using partial orders. However, such an approach typically requires ad-hoc mechanisms to correctly capture the data and control-flow choices/conflicts present in real-world programs. In this work, we propose a novel, conflict-aware, composable, truly concurrent semantics for programs written using C/C++ for modern weak memory architectures. We exploit our symbolic semantics based on general event structures to build an efficient decision procedure that detects assertion violations in bounded multi-threaded programs. Using a large, representative set of benchmarks, we show that our conflict-aware semantics outperforms the state-of-the-art partial-order based approaches

EFFECT OF EXCLOSURE ON RUNOFF, SEDIMENT CONCENTRATION AND SOIL LOSS IN EROSION PLOTS

Nowadays watershed and rangeland management projects play the important rolein water resources and soil management worldwide. Although watershed andrangeland management projects have the considerable importance as approaches torural areas development and natural resources management, more studies havebeen focused on their effects on sediment and their effects on soil erosion haverarely been considered. The present study was conducted in two treated and controlsub-watersheds with exclosure treatment and under grazing respectively, inKhamsan representative watershed with an area of 4337.27 ha in south ofKurdistan Province, Iran. Three plots were installed in each western, northern andeastern slopes for the runoff volume and coefficient, sediment concentration andsoil loss measurement. The exclosure treatment was operated for installed plots intreated sub-watershed from 2007. Then, all the data of runoff volume andcoefficient, sediment concentration and soil loss from USLE standard plots in bothcontrol and treated sub-watersheds for 52 events over the years 2009 to 2014 werecompared and evaluated. Therefore, in order to the number of plots and subwatersheds,18 USLE standard plot data were finally recorded and analysed foreach storm event. The results showed the significant (p≤0.05) decreasing effect ofexclosure treatment on runoff volume, sediment concentration and soil loss at plotscale. Finally, decreasing rates of 15.68, 6.13, 16.67, 24.37 and 21.43% due toexclosure respectively for runoff volume and coefficient, sediment concentration,soil loss and sediment yield were obtained. The variables of runoff volume, soilloss and sediment yield had statistically significant differences (p≤0.05) in treatedand control sub-watersheds. The sediment concentration variable had p value of0.058 and therefore the effect of exclosure treatment on sediment concentrationwas also significant (p≤0.06)