On the minimum and maximum selective graph coloring problems in some graph classes

Given a graph together with a partition of its vertex set, the minimum selective coloring problem consists of selecting one vertex per partition set such that the chromatic number of the subgraph induced by the selected vertices is minimum. The contribution of this paper is twofold. First, we investigate the complexity status of the minimum selective coloring problem in some specific graph classes motivated by some models described in Demange et al. (2015). Second, we introduce a new problem that corresponds to the worst situation in the minimum selective coloring; the maximum selective coloring problem aims to select one vertex per partition set such that the chromatic number of the subgraph induced by the selected vertices is maximum. We motivat

Bridging gap between standard and differential polynomial approximation: The case of bin-packing

AbstractThe purpose of this paper is mainly to prove the following theorem: for every polynomial time algorithm running in time T(n) and guaranteeing standard-approximation ratio ϱ for bin-packing, there exists an algorithm running in time O(nT(n)) and achieving differential-approximation ratio 2 − ϱ for BP. This theorem has two main impacts. The first one is “operational”, deriving a polynomial time differential-approximation schema for bin-packing. The second one is structural, establishing a kind of reduction (to our knowledge not existing until now) between standard approximation and differential one

Le gisement tungstifère de Leucamp (Cantal, France) : contrôle géologiques et minéralisations

Le gisement de Leucamp (district de la Châtaigneraie : Cantal, France) est constitué de filons de quartz à wolframite associés spatialement à un granite carbonifère et encaissés dans des schistes épimétamorphiques d'âge inconnu. La structure complexe du champ filonien peut s'expliquer par la réouverture et le remplissage simultanés, sans doute sous l'action des fluides, de toutes les structures planaires crées par la tectonique souple polyphasée antérieure à la mise en place du granite. Les filons sont ultérieurement hachés par des failles normales, elles-même scellées par différentes venues éruptives. Le remplissage des filons minéralisés peut être décomposé en une venue à tourmaline suivie, après fracturation, par une venue de quartz; après une nouvelle fracturation, le remplissage se termine par la minéralisation principale (pyrite et wolframite associées à des minéraux mineurs de Bi, As, Zn et Au). La minéralisation princale est remaniée dans les veines tardive

Coreness of Cooperative Games with Truncated Submodular Profit Functions

Coreness represents solution concepts related to core in cooperative games, which captures the stability of players. Motivated by the scale effect in social networks, economics and other scenario, we study the coreness of cooperative game with truncated submodular profit functions. Specifically, the profit function $f(\cdot)$ is defined by a truncation of a submodular function $\sigma(\cdot)$: $f(\cdot)=\sigma(\cdot)$ if $\sigma(\cdot)\geq\eta$ and $f(\cdot)=0$ otherwise, where $\eta$ is a given threshold. In this paper, we study the core and three core-related concepts of truncated submodular profit cooperative game. We first prove that whether core is empty can be decided in polynomial time and an allocation in core also can be found in polynomial time when core is not empty. When core is empty, we show hardness results and approximation algorithms for computing other core-related concepts including relative least-core value, absolute least-core value and least average dissatisfaction value

Advanced Ceramic Wafer Seals Demonstrated at 2000 deg. F

Durable, high-temperature sliding seals are required in advanced hypersonic engines and around movable control surfaces on future vehicles. These seals must operate at temperatures of 2000 to 2500 F, limit hot gas flow, remain resilient for multiple cycles, and resist scrubbing damage against rough surfaces. Current seal designs do not meet these demanding requirements, so the NASA Glenn Research Center is developing advanced seals and preload devices to overcome these shortfalls. An advanced ceramic wafer seal design and two silicon nitride compression spring designs were evaluated in a series of compression, scrub, and flow tests

Classificação estrutural e tectónica dos granitóides neoproterozóicos do cinturão Paraíba do Sul no Estado do Rio de Janeiro

The granitoids of the Neoproterozoic in the Paraíba do Sul belt in the State of Rio de Janeiro are classified according to their ages related to the recognized tectonic phases, their location in the different tectonic domains, the crustal level of emplacement, petrografic compositions and the tectonic environment. Three groups of granites are distinguished: Syn-F2, Syn-F3 and Syn-F4. The compositionally expanded syn-F2 granitoids, (e.g. tonalite/granodiorite/granite), with age about the 620 Ma., are comparable to the Cordilleran I-Type magmatism, emplaced at level of the crust from amphibolite/granulite facies, and their origin is related to a subduction zone below of the Paraíba of Sul belt, from SE to NW. The other syn-F2 are migmatitic S-type granitoids, linked to a continental collision event with age about the 600 Ma. The syn-F3 and syn-F4 groups are compositionally restricted (e.g. monzogranite and syenogranite dominantly) (-490 - 560 Ma), and their magmatism is considered to be Caledonian I-Type.Os granitóides Neoproterozóicos do cinturão Paraíba do Sul no Estado do Rio de Janeiro são classificados, neste trabalho, em função das fases tectónicas regionais, dos domínios estruturais de ocorrência, do nível crustal de colocação, do tipo composicional, do caráter tectónico e de seu posicionamento temporal com base nos dados geocronológicos disponíveis, muitos deles ainda inéditos. São distinguidos três grupos de granitóides: sin-F2, sin-F3 e sin-F4. Os sin-F2 dividem-se em dois subgrupos. Um deles, predominante, de composição expandida (tonalito/granodioríto/granito), com idade ao redor de 620 Ma, comparável aos granitos tipo-I Cordilheirano, é colocado em nível crustal de fácies anfibolito a granulite. A origem deste magmatismo é relacionada a uma zona de subducção, com mergulho de SE para NW, por debaixo do cinturão Paraíba do Sul. O outro subgrupo, subordinado, é constituído por granitóides migmatíticos do tipo-S, atribuídos a um evento colisional com idade ao redor de 600 Ma. Os granitóides sin-F3 e sin-F4, de composição não expandida (com predomínio de sieno e monzogranitos), são considerados como magmatismo tipo-I Caledoniano, de caráter tardia pós-colisional, com idade entre 490 e 560 Ma

Improved Seals for High Temperature Airframe Applications

Current thermal barrier seals, such as those used on the Space Shuttle, are insufficient to fully meet the demands of future hypersonic vehicles and reentry spacecraft. Previous investigations have demonstrated limited usage temperatures, as evidenced by a decreased ability to maintain sealing effectiveness at high temperatures (i.e., inadequate resiliency). In order to improve resiliency at elevated temperatures, Rene 41 (Allvac) was substituted for Inconel X-750 (Special Metals Corp.) as the spring tube material in the existing seal design. A seal construction incorporating the Rene 41 spring tube was fabricated and tested against the baseline Inconel X-750 spring tube seal. Although resiliency improvements were not as dramatic as in previous tests with the spring tubes alone, seals incorporating the Rene 41 spring tube exhibited an average 20 percent resiliency enhancement up to 1750 F when compared to seals containing the Inconel spring tube. In addition, the seals with the Rene 41 spring tubes showed less reduction in resiliency as temperatures increased above 1200 F. Results also indicated the Saffil (Saffil Ltd.) insulation in the core of the seal contributed more to resiliency than previously thought. Leakage data did not demonstrate an improvement with the seal containing the Rene 41 spring tube. However, based upon resiliency results, one could reasonably expect the Rene 41 version of the seal to track gap openings over a wider range. Therefore it would exhibit lower leakage than the Inconel X-750 version as the seal gap opens during a typical mission