EFFECTS OF ROTATIONAL SPEED,FEED RATE AND TOOL TYPE ON TEMPERATURES AND CUTTING FORCES WHEN DRILLING BOVINE CORTICAL BONE

Surgical procedures that affect the human body's bone structure, often entail cutting, drilling or screwing operations of bone. The post-operative success of these procedures is largely dependent on the degree of damage introduced by the process. In this article, the influence of the rotational velocity, feed per tooth and two drill bit type on workpiece temperatures and cutting forces when drilling bovine cortical bone has been studied. The purpose is to find the optimum cutting conditions that will generate the lower temperatures and cutting forces. The measurement of temperatures has been carried out with an infrared thermography camera, and a piezoelectric dynamometer has been employed to obtain forces. A model has been developed from which heat flow into the drilled bone can be estimated from specific cutting force and the fraction of total heat generated that flows into the bone. This fraction has been shown to depend on the Peclet number for the process, proportional to the drill rotation speed, the feed per cutting edge and the diameter of the drill. By means of the model, some contradictions in the literature as to the effect on bone heating of increasing rotation speeds and feeds per cutting edge have been resolved.     

MRT letter: Extended depth from focus reconstruction method for stretch zone measurement in 15-5PH steel

The stretch zone width (SZW) data for 15‐5PH steel CTOD specimens fractured at ?150°C to + 23°C temperature were measured based on focused images and 3D maps obtained by extended depth‐of‐field reconstruction from light microscopy (LM) image stacks. This LM‐based method, with a larger lateral resolution, seems to be as effective for quantitative analysis of SZW as scanning electron microscopy (SEM) or confocal scanning laser microscopy (CSLM), permitting to clearly identify stretch zone boundaries. Despite the worst sharpness of focused images, a robust linear correlation was established to fracture toughness (K_C) and SZW data for the 15‐5PH steel tested specimens, measured at their center region. The method is an alternative to evaluate the boundaries of stretched zones, at a lower cost of implementation and training, since topographic data from elevation maps can be associated with reconstructed image, which summarizes the original contrast and brightness information. Finally, the extended depth‐of‐field method is presented here as a valuable tool for failure analysis, as a cheaper alternative to investigate rough surfaces or fracture, compared to scanning electron or confocal light microscopes. Microsc. Res. Tech. 75:1155–1158, 2012. © 2012 Wiley Periodicals, Inc.     

Experimental characterization of a 6.7 GHz coaxial Bragg reflector

A coaxial line periodically loaded by circular disks on the inner conductor is designed and constructed to act as Bragg reflector in the 4.0-9.5 GHz frequency range. This is achieved by placing 10 disks (0.35 cm thick and 6.22 cm in diameter) equally spaced by the periodic distance of 1.8 cm on a coaxial waveguide with inner and outer diameters of 6.90 and 4.22 cm. Experiments on a periodic structure made from stainless steel demonstrate a band gap of 5.6 GHz centered at the 6.7 GHz design frequency in close agreement with 3D microwave computer simulations.     

Radon and radon daughter evaluation in a natural radioactivity survey indoors

An indoor survey in order to estimate the population exposure in five towns of an Italian Region is presented. A particular methodology for the campaign was planned and is being applied. Gamma spectrometry of building materials, exposure rate measurements indoors and outdoors and radon concentration measurements indoors were taken with different techniques. A correlation was found between mean gamma exposure rate and mean radon concentration in the houses investigated. An evaluation of mean effective dose equivalents for the inhabitants of the five towns is reported.     

Real-time camera motion tracking in planar view scenarios

We propose a novel method for real-time camera motion tracking in planar view scenarios. This method relies on the geometry of a tripod, an initial estimation of camera pose for the first video frame and a primitive tracking procedure. This process uses lines and circles as primitives, which are extracted applying classification and regression tree. We have applied the proposed method to high-definition videos of soccer matches. Experimental results prove that our proposal can be applied to processing high-definition video in real time. We validate the procedure by inserting virtual content in the video sequence.     

Service life estimation of cement-rendered facades

Factorial methods are cost-effective, quick and easy-to-implement methodologies for service life estimation of buildings and their parts. They also stand as the underlying principle of the International Standard Organisation ISO-15686 for service life planning. However, few guidelines exist on how to relate real-life deterioration phenomena to quantified durability values for use within factorial methods. This paper describes a methodology to quantify the ‘reference service life’ and its modifying durability factors for cement-rendered facades based on fieldwork data of 150 cases located in Portugal. The methodology proposed relies on regression analysis of the overall degradation level of the cases assessed. The results obtained are used as a reference set of data for the statistical benchmarking of five different scenarios for the quantification of modifying durability factors of cement-rendered facades. Although the values obtained relate to a specific building element and material, on the one hand, and reflect the Portuguese construction context, on the other hand, the proposed methodology may be applied to other materials and elements in different building and environmental contexts, thus providing a guideline for the quantification of durability factors for use within the factor method.

Les méthodes des facteurs sont rentables, rapides et faciles à mettre en ?uvre lorsque l'on veut estimer la durée de vie des bâtiments et de leurs parties. Elles sont également le principe sous-jacent de la norme ISO-15686 concernant la planification pour une durée de vie déterminée. Toutefois, il existe quelques directives sur la façon de rapporter les phénomènes de détérioration de la vie réelle à des valeurs de durabilité quantifiées à utiliser avec les méthodes des facteurs. Cet article décrit une méthode de quantification de la durée de vie déterminée de référence et ses facteurs modificateurs de durabilité pour des façades réalisées avec un enduit de ciment, sur la base de données obtenues sur le terrain et concernant 150 cas situés au Portugal. La méthodologie proposée repose sur l'analyse de régression du niveau global de dégradation des cas évalués. Les résultats sont utilisés comme ensemble de références de données pour la comparaison statistique de cinq scénarios différents pour la quantification des facteurs modificateurs de durabilité de façades à enduit de ciment. Bien que les valeurs obtenues se rapportent à un élément de construction et à des matériaux spécifiques d'une part et que d'autre part elles traduisent le contexte de la construction au Portugal, la méthodologie proposée peut être appliquée à d'autres matériaux et éléments dans des contextes de bâtiments et d'environnements différents, ce qui constitue une directive pour la quantification des facteurs de durabilité à utiliser avec la méthode des facteurs.

Mots clés: facteurs de durabilitéfaçades;méthode des facteurs facteurs modificateurs;durée de vie déterminée;enduit     

The Use of Elevation Map Histograms for Topographic Heterogeneity Analysis

Surface defects are extremely important in mechanical characterization of several different materials. Therefore, the analysis of surface finishing is essential for a further simulation of surface mechanical properties in a customized project in materials science and technology. One of the methods commonly employed for such purpose is the statistical mapping of different sample surface regions using the depth from focus technique. The analysis is usually performed directly from the elevation maps which are obtained from the digital image processing. In this paper, the possibility of quantifying the surface heterogeneity of Silicon Carbide porous ceramics by elevation map histograms is presented. The advantage of this technique is that it allows the qualitative or quantitative verification of all surface image fields that cannot be done by using the Surface Plot plugin of image J? platform commonly used in digital image processing.     

Quadrotors Formation Control

In this paper, the impact of the medium access protocols on the average consensus problem over wireless networks for a group of quadrotors is established. The stabilization of each helicopter is guaranteed using a simple and bounded nonlinear control strategy. We study the case of a group of quadrotors communicating over a wireless network considering both directed and undirected graphs of information flow. It turns out that the media access control (MAC) protocols have a direct impact in both convergence time and average consensus solution, i.e., the solution of the average consensus is no longer the average of the initial conditions. It will be shown that the solution for the average consensus problem over a wireless network depends directly on the MAC algorithm. Simulations are provided to demonstrate the theoretical results. In addition, to validate the control strategy some experimental tests have been carried out to control the yaw angle of two quadrotors.