Understanding the effect of seams on the aerodynamics of an association football

The aerodynamic properties of an association football were measured using a wind tunnel arrangement. A third scale model of a generic football (with seams) was used in addition to a 'mini-football'. As the wind speed was increased, the drag coefficient decreased from 0.5 to 0.2, suggesting a transition from laminar to turbulent behaviour in the boundary layer. For spinning footballs, the Magnus effect was observed and it was found that reverse Magnus effects were possible at low Reynolds numbers. Measurements on spinning smooth spheres found that laminar behaviour led to a high drag coefficient for a large range of Reynolds numbers, and Magnus effects were inconsistent, but generally showed reverse Magnus behaviour at high Reynolds number and spin parameter. Trajectory simulations of free kicks demonstrated that a football that is struck in the centre will follow a near straight trajectory, dipping slightly before reaching the goal, whereas a football that is struck off centre will bend before reaching the goal, but will have a significantly longer flight time. The curving kick simulation was repeated for a smooth ball, which resulted in a longer flight time, due to increased drag, and the ball curving in the opposite direction, due to reverse Magnus effects. The presence of seams was found to encourage turbulent behaviour, resulting in reduced drag and more predictable Magnus behaviour for a conventional football, compared with a smooth ball. © IMechE 2005

Compressive Pattern Matching on Multispectral Data

We introduce a new constrained minimization problem that performs template and pattern detection on a multispectral image in a compressive sensing context. We use an original minimization problem from Guo and Osher that uses $L_1$ minimization techniques to perform template detection in a multispectral image. We first adapt this minimization problem to work with compressive sensing data. Then we extend it to perform pattern detection using a formal transform called the spectralization along a pattern. That extension brings out the problem of measurement reconstruction. We introduce shifted measurements that allow us to reconstruct all the measurement with a small overhead and we give an optimality constraint for simple patterns. We present numerical results showing the performances of the original minimization problem and the compressed ones with different measurement rates and applied on remotely sensed data.Comment: Published in IEEE Transactions on Geoscience and Remote Sensin

Allied Health Professions in the Health-sector Job Structure

This article reviews the characteristics of allied health professions in the U.S., Massachusetts, and Boston health sectors. These occupations are considered in the broader context of the multitiered job structure of the health sector and their gender and ethnic composition. The discussion includes surveys of vacancy rates and wage levels for selected allied health professions in Massachusetts hospitals. The article concludes with a more detailed, albeit national, picture of these occupations in the hospital sector per se, their demographic composition, and earnings level

Investigations into soccer aerodynamics via trajectory analysis and dust experiments

We present a summary of our investigations into the aerodynamics of soccer balls (association footballs). Using a ball launcher and high-speed cameras, we are able to determine drag and lift coefficients using trajectory analysis. Advantages of this approach over wind tunnels include studying balls in flight without a support rod, which may influence aerodynamic studies in wind tunnels, and the ability to determine lift coefficients in regions inaccessible by many wind tunnels. We have found lift coefficients for spin parameters between 0 and 1 and Reynolds numbers between 130,000 and 300,000. Launching a ball into a dust cloud allows for the study of boundary-layer separation, again without the need of a support rod, which is needed for wind-tunnel studies. We have found boundary-layer separation angles in and around the drag crisis. Anomalous behavior is seen just past the drag crisis. © 2012 Published by Elsevier Ltd

Synthesis of control implementation for discrete manufacturing systems

International audienceThe paper presents the concepts and steps required to synthesize a correct control implementation for discrete manufacturing systems, starting from Grafcet speci-® cations. A formal framework implementing the synthesis steps is also presented and illustrated with an example of a drilling system

Work Hours in Retail: Room for Improvement

With full-time jobs, hourly wages are appropriate primary indicators of job quality. However, in sectors where full-time schedules do not dominate, total hours matter for job quality and worker outcomes. We explored hour levels and trends in retail trade and its largest subsector, grocery stores. Retail is known for part-time and short shifts. With a comparison of retail hours in three countries—the United States, Canada, and Mexico—we contribute insights into aspects of the U.S. policy and regulatory systems that could be altered in order to improve retail jobs

Grafcet: Behavioural Issues and Control Synthesis

International audienceThis paper discusses the difficulties encountered in identifying the correct behaviour of Grafcet specifications in view of synthesising a correct control execution model. Formal algorithms for the synthesis of supervisory controllers related to Grafcet are also proposed. These algorithms consider the constraints induced by the behaviour of the controlled plant so as to identify the required correct behaviour of Grafcet during control execution. The resulting control execution is deadlock-free, and represents the minimal possible restriction of the behaviour of a given Grafcet, subject to a number of specified constraints

Validation of a multiplex reverse transcription and pre-amplification method using TaqMan(®) MicroRNA assays.

Since the discovery of microRNAs (miRNAs), different approaches have been developed to label, amplify and quantify miRNAs. The TaqMan(®) technology, provided by Applied Biosystems (ABIs), uses a stem-loop reverse transcription primer system to reverse transcribe the RNA and amplify the cDNA. This method is widely used to identify global differences between the expression of 100s of miRNAs across comparative samples. This technique also allows the quantification of the expression of targeted miRNAs to validate observations determined by whole-genome screening or to analyze few specific miRNAs on a large number of samples. Here, we describe the validation of a method published by ABIs on their web site allowing to reverse transcribe and pre-amplify multiple miRNAs and snoRNAs simultaneously. The validation of this protocol was performed on human muscle and plasma samples. Fast and cost efficient, this method achieves an easy and convenient way to screen a relatively large number of miRNAs in parallel

The influence of surface characteristics on the tribological interactions at the shoe-surface interface in tennis

During dynamic tennis specific movements, such as accelerating and side stepping, the traction provided by a shoe-surface combination plays an important role in the injury risk and performance of the player. Acrylic hard court tennis surfaces have been reported to have increased injury occurrence due to an increased traction coefficient. There is a requirement for an improved scientific understanding of the tribological interactions at the shoe surface interface and the effects footwear and surface parameters have on the friction mechanism developed. Often mechanical test methods used for the testing and categorisation of playing surfaces do not tend to simulate loads occurring during participation on the surface, and thus are unlikely to predict human response to the surface. A new traction testing device, discussed in this paper, has been developed to mechanically measure the traction force between the shoe and the surface under appropriate loading conditions. Acrylic Harcourt tennis surfaces generally have a rough surface topography, due to a sand and acrylic paint mixed top coating, and have a deformable under layer to provide impact attenuation. Surface micro-roughness has been found to influence the friction mechanisms presents during viscoelastic contacts, as found in footwear-surface interactions. This paper aims to further understand the influence of micro-roughness on tennis surfaces. The micro-roughness and traction of a controlled set of acrylic hard court tennis surfaces have been measured. The influence of roughness on tennis surfaces traction is discussed