87 research outputs found
Approximating the stability number and the chromatic number of a graph via semidefinite programming
No full textWhatever Happened to … Scandalous Criminal Allegations: the Miazga Case
No full textAuthor has retained copyright of article. Article was deposited after permission was granted by CPLEA 02/3/201
SUR L'ÉCOLOGIE DE LA LARVE D'ANKYLOSTOMA DUODENALE DANS UNE RÉGION ENDÉMIQUE DE LA VALLÉE DU FLEUVE SAVA (JUGOSLAVIA)
No full textThe Right to Refuse Dangerous Work
No full textAuthor has retained copyright of article. Article was deposited after permission was granted by CPLEA 03/04/2015Most jobs have some element of danger in them. At a minimal level, the danger associated with our employment
does not go much beyond the regular hazards of being alive, such as getting to and from work every day, the
stress of working with difficult people, or the infinitesimally small chance of having a meteor or airplane crash
through our building. There is interest in the growing field of occupational disease, where certain occupations
may be exposed to contaminants or conditions that cumulatively and slowly manifest themselves in the workers
over time. Examples include firefighters inhaling toxins, professional drivers and diesel fumes, office workers and
repetitive strains, and soldiers who later suffer post-traumatic stress syndrome. In this article we address acute,
serious, imminent dangers encountered in performing one’s job at work.Ye
Localization of users in multiuser MB OFDM UWB systems based on TDOA principle
No full textIn this paper, we analyze localization capabilities of multi-band OFDM UWB systems. TDOA (time difference of arrival) method is used for localization. M temporally synchronized sensors are localizing transmitter of unknown location. Space-temporal signal model in AWGN channel and in IEEE 802.15.3a channel model is derived analytically.We investigate the influence of correlation of channels between transmitter and each of sensors in sensor array on localization accuracy. The results are verified through simulation of hypothetical measurement setup where sensor array have circular geometry and the transmitter is placed within the array circle
The operator for the Chromatic Number of a Graph
No full textWe investigate hierarchies of semidefinite approximations for the chromatic number of a graph . We introduce an operator mapping any graph parameter , nested between the stability number and \chi\left( {\ol G} \right), to a new graph parameter , nested between \alpha (\ol G) and ; is polynomial time computable if is. As an application, there is no polynomial time computable graph parameter nested between the fractional chromatic number and unless P=NP. Moreover, based on Motzkin-Straus formulation for , we give (quadratically constrained) quadratic and copositive programming formulations for . Under some mild assumption, but, while remains below , can reach (e.g., for ). We also define new polynomial time computable lower bounds for , improving the classic Lov\'{a}sz theta number (and its strengthenings obtained by adding nonnegativity and triangle inequalities); experimental results on Hamming graphs, Kneser graphs and DIMACS benchmark graphs will be given in the follow-up paper
Semidefinite bounds for the stability number of a graph via sums of squares of polynomials
No full textComputing semidefinite programming lower bounds for the (fractional) chromatic number via block-diagonalization
No full textRecently we investigated in "The operator for the Chromatic Number of a Graph" hierarchies of semidefinite approximations for the chromatic number of a graph . In particular, we introduced two hierarchies of lower bounds, the `'-hierarchy converging to the fractional chromatic number, and the `'-hierarchy converging to the chromatic number of a graph. In both hierarchies the first order bounds are related to the Lov\' asz theta number, while the second order bounds would already be too costly to compute for large graphs. As an alternative, relaxations of the second order bounds are proposed. We present here our experimental results with these relaxed bounds for Hamming graphs, Kneser graphs and DIMACS benchmark graphs. Symmetry reduction plays a crucial role as it permits to compute the bounds using more compact semidefinite programs. In particular, for Hamming and Kneser graphs, we use the explicit block-diagonalization of the Terwilliger algebra given by Schrijver. Our numerical results indicate that the new bounds can be much stronger than the Lov\' asz theta number. For some of the DIMACS instances we improve the best known lower bounds significantly
Semidefinite Bounds for the Stability Number of a Graph via Sums of Squares of Polynomials
No full text
- …
