On some properties of the Laplacian matrix revealed by the RCM algorithm

In this paper we present some theoretical results about the irreducibility of the Laplacian matrix ordered by the Reverse Cuthill-McKee (RCM) algorithm. We consider undirected graphs with no loops consisting of some connected components. RCM is a well-known scheme for numbering the nodes of a network in such a way that the corresponding adjacency matrix has a narrow bandwidth. Inspired by some properties of the eigenvectors of a Laplacian matrix, we derive some properties based on row sums of a Laplacian matrix that was reordered by the RCM algorithm. One of the theoretical results serves as a basis for writing an easy MATLAB code to detect connected components, by using the function “symrcm” of MATLAB. Some examples illustrate the theoretical results.The research has been supported by Spanish DGI grant MTM2010-18674, Consolider Ingenio CSD2007-00022, PROMETEO 2008/051, OVAMAH TIN2009-13839-C03-01, and PAID-06-11-2084.Pedroche Sánchez, F.; Rebollo Pedruelo, M.; Carrascosa Casamayor, C.; Palomares Chust, A. (2016). On some properties of the Laplacian matrix revealed by the RCM algorithm. Czechoslovak Mathematical Journal. 66(3):603-620. doi:10.1007/s10587-016-0281-yS60362066

Design of controlled rupture structure for safe vector ejection

The design of structures, which have a controlled rupture, is a topic of interest of both civil and military industry and the definition of design guidelines and criteria can be helpful for future configurations. Automotive, aerospace and defence study solutions can be useful to meet the high-performance requirements of lightness and safety, and more the latest studies concerning composite materials and the relative fracture micromechanics can help to achieve these targets. The research activity of this work is focused on the numerical analysis with the aim to design a possible part for new Maritime Firing Tubes. In particular the design of new tailgate configuration was studied considering the correct structure fragmentation to ensure a clear ejection, while reducing the weight of the panels by exploiting the characteristics of the composite material. The goal of this research is the development of a scientific and methodological approach to the study of controlled rupture structure for the design and optimization of launcher tailgate. An innovative concept of hatch composed by just one carbon resin composite laminate is studied and by varying the geometric configuration it is possible to optimize the breaking path and the contact force. The complex geometry of the hatch, the high impulsive load, the energy transferred during the impact between a sort of missile and hatch, and the ways of safely breaking large flaps of panels are elements that have characterized the dimensioning of the composite in order to satisfy the stringent requirements about the ejection event in a missile lifecycle during its own firing. The focus is the evaluation of the material fragmentation behavior and element deletion followed by excessive deformation in controlled fragments closely distributed around one or several specific sizes in presence of high-speed environment

Video tracking for the detection of external load to establish proper parameters in elite soccer players during high intensity training

The video recording and following analysis of games allows sport scientists and coaches to evaluate physical performances of professional soccer players. In particular, can be useful to allows and analyse speed thresholds, accelerations, decelerations and total amount of energy expenditure expressed with metabolic power. It is well known that accelerations are essential to establish sport specific metabolic loads (Di Prampero et al., 2010). Given the obvious importance of a correctly quantifying of metabolic of the various football movements, the aim of this study is to analyse accelerations, decelerations and speed thresholds player by player during matches. Given the obvious importance of a correct metabolic load of the various football movements, the aim of this study wants to analyse accelerations, decelerations and speed thresholds, players by players during matches. The study will also highlight players, into their own field roles, for a better optimization of individual and team project planning

Influence of process parameters on kerf geometry in fine laser cutting of 6061 Al alloy

In the present work, laser cutting of 6061-T6 aluminium alloy sheets, 1 mm in thickness, was investigated using a 150W lamp pumped Nd:YAG laser, characterised by pulse power up to 3 kW. The study was divided in two steps: first, in order to find the maximum cutting speed, defined as the speed beyond which it is not possible to cut the sheet, cutting pre-tests were performed at a fixed average power (150W), changing the pulse duration (i.e. the pulse power and the pulse energy) and the cutting speed; then, in order to assess the influence of the process parameters on kerf geometry and roughness, a second set of tests was carried out, and a full factorial design 32x2 was adopted according to the DoE methodology. In order to determine which of the process parameters affects the kerf geometry and how, ANalysis Of VAriance (ANOVA) was used. Experimental results show the possibility to obtain kerf characterized by narrow width, low perpendicularity, low dross height and low roughness, resulting in a fine cut on a 6061 Al alloy

Influence of process parameters on kerf geometry and surface roughness in Nd:YAG laser cutting of Al 6061T6 alloy sheet

In the present study, fine laser cutting of aluminium alloy 6061-T6 sheets, characterised by light reflection and heat conductivity, by means of a 150-W multimode lamp pumped Nd:YAG laser is investigated through an experimental testing campaign. Design of experiments (DoE) and analysis of variance (ANOVA) are adopted to study the influence of the process parameters on the kerf geometry and surface roughness. The results show that the laser allows cutting 1-mm-thick AA6061-T6 sheets with a cutting speed up to 700 mm/min, obtaining narrow kerfs (smaller than 200 mu m), a fine taper angle (lower than 4A degrees), a low dross height (about 40 mu m) and a roughness average, Ra, around 4 mu m

An investigation on Nd:YAG laser cutting of Al 6061 T6 alloy sheet

In this research work, laser cutting of 6061-T6 aluminium alloy sheets by means of a 150 W multimode pulsed Nd:YAG laser is investigated. Linear scans using the maximum average power and different cutting directions and pulse durations are executed to measure the maximum cutting speeds. Then, cutting tests are performed by varying beam travel direction, pulse duration and cutting speed. The results show that a 150W multimode pulsed Nd:YAG laser allows to cut 1 mm-thick 6061-T6 sheets with cutting speed up to 700 mm/min, obtaining narrow kerfs (< 200 μm) with a good taper angle (< 5°) and low dross height (about 40 μm)

Influence of process parameters on kerf geometry in fine laser cutting of 6061 Al alloy

In the present work, laser cutting of 6061-T6 aluminium alloy sheets, 1 mm in thickness, was investigated using a 150W lamp pumped Nd:YAG laser, characterised by pulse power up to 3 kW. The study was divided in two steps: first, in order to find the maximum cutting speed, defined as the speed beyond which it is not possible to cut the sheet, cutting pre-tests were performed at a fixed average power (150W), changing the pulse duration (i.e. the pulse power and the pulse energy) and the cutting speed; then, in order to assess the influence of the process parameters on kerf geometry and roughness, a second set of tests was carried out, and a full factorial design 3^2x2 was adopted according to the DoE methodology. In order to determine which of the process parameters affects the kerf geometry and how, Analysis Of VAriance (ANOVA) was used. Experimental results show the possibility to obtain kerf characterized by narrow width, low perpendicularity, low dross height and low roughness, resulting in a fine cut on a 6061 Al alloy

Effects of gluten enriched diet on the small intestinal mucosa of normal mice and mice with graft versus host reaction.

This study looked at the effect of extra dietary gluten on the intestinal architecture of both normal mice and those with an ongoing mucosal delayed hypersensitivity reaction. BDF1 normal mice and mice in which a graft v host reaction (GvHR) had been induced, both weaned on gluten free diet, were allocated for three weeks to three different dietary regimens: gluten free, 'normal' (3.6% gluten), and gluten enriched (15.8% gluten). In normal mice receiving the gluten containing diet, shorter villi, deeper crypts, and higher crypt cell production rate were noted when compared with those receiving gluten free diet: these changes were more pronounced in those receiving the gluten enriched diet. GvHR mice showed shorter villi and an increase in both crypt length and crypt cell production rate when compared with normal mice, but the presence of gluten in their diet did not produce additional damage. Both in normal and in GvHR mice receiving gluten containing diet there were no signs of systemic (cell mediated or humoral) or mucosal immune reactions (raised intraepithelial lymphocyte counts or enhanced epithelial Ia expression) to gliadin. In conclusion, increasing the dietary gluten content produces significant changes in the mucosal architecture of normal mice; mice with GvHR enteropathy do not show additional damage resulting from dietary gluten