Search

Soccer balls have undergone dramatic changes in their surface structure that can affect their aerodynamics. The properties of the soccer ball surface such as the panel shape, panel orientation, seam characteristics, and surface roughness have a significant impact on its aerodynamics and flight trajectory. In this study, we performed wind-tunnel tests to investigate how the introduction of grooves on the surface of a soccer ball affects the flight stability and aerodynamic forces on the ball. Our results show that for soccer balls without grooves, changing the panel orientation of the ball causes a significant change in the drag coefficient. Soccer balls with grooves exhibited a smaller change in air resistance (Cd) in the supercritical region (20 to 30 m/s, 3.0 &times, 105 &le, Re &le, 4.7 &times, 105), compared to the ungrooved ball where only the panel orientation was changed. Furthermore, at power-shot speeds (25 m/s), the grooved ball exhibited smaller variations in lift force and side force than the ungrooved ball. These results suggest that a long groove structure on the surface of the soccer ball has a significant impact on the air flow around the ball in the supercritical region, and has the effect of keeping the air flow separation line constant.

Inconel 601 is one material of choice for intermediate- to high-temperature protective coatings for spark plugs’ ground electrodes. Production of ground electrodes of spark plugs implies the following operations: the tamping of the copper core in an Inconel 601 cup, cold-forming of the assembly, annealing, welding, and bending of the final spark plug. On the production line, the use of Inconel 601 as a protective coating for ground electrodes leads to possible cracking in the welded area after bending. In the present paper, possible causes of cracking are analyzed. It is clearly shown that a combination of Copper –Inconel interface oxidation, Inconel yielding during the heat treatment, and micro-movements during bending lead to cracks in the welded area of the ground electrode. First, the detrimental effect of gaps, between Copper and Inconel 601, is shown experimentally. Second, a thermo-mechanical analysis combined with SEM (Scanning Electron Microscopy) observations identified the annealing treatment and interface oxidation as the main cause of gaps. Third, bending simulations show the relation between these gaps and cracking. Finally, a new ground electrode design, preventing cracks, is suggested.

An empirical and theoretical investigation was achieved on a cylindrical storage collector. It was suggested in this work for a cylinder to be cut at an inclined cutting plane. The tests were achieved for both summer and winter climate conditions with and without hot water removal. The hourly system performance parameters were investigated systematically for different experiments. These included the average storage temperature, velocity distribution, and temperature distribution. In the cylindrical collector, the ultimate magnitude of the average storage temperature was 25 °C, while the maximum temperature at the tip of the cylindrical collector was 58 °C for a typical spring day. Meanwhile, the rectangular collector can warm up the stored water to a temperature of 23 °C, when the inlet water temperature was 12 °C. The performance of the new solar collector was, in general, similar to the performance of the conventional thermosyphon flat plate solar water heaters. The Fluent program was used to confirm the experimental results. The free convection in the cylindrical collector was investigated based on the method of control volume. From the Fluent data and analysis of the collector, the temperature and velocity distributions throughout the day were obtained. The Fluent program data was well compatible with the experimental results.

International audience; Self-supported transition metal pnictides (MPn) (with M= Ni, Cu and Pn = P, Sb) nanoarchitectured electrodes were prepared by solid state reaction from metallic foam and nanorods. This specific design aims to optimize both MPn/current collector and MPn/electrolyte interfaces of the electrode in the Li ion battery. This new electrode preparation process is based on the Pn solid state reaction with the metallic M nanoarchitectured substrate. Electrochemical tests of the as-obtained self supported electrodes show the improvement in the capacity retention of MPn active material in the Li battery. This simple synthesis process can conceptually provide new opportunities for tailored design of electrode materials.

article i nfo Available online 16 August 2011 Silver oxovanadate powders were produced using a low temperature hydrothermal synthesis method. X-ray diffraction (XRD) and Raman microscopy revealed the formation of the α-Ag3VO4 phase, and differential scanning calorimetry (DSC) indicated that the powders underwent phase changes with the increase of temperature (formation of Ag-deficient phases). Ag3VO4 precipitates were subsequently investigated as potential high temperature solid lubricant (SL) powders that may be burnished onto textured surfaces. Textured coatings were produced by the sputter deposition of vanadium nitride (VN) thin films, followed by the fabrication of a periodic array of micro-scale dimples with reactive ion etching (RIE). The etched patterns acted as reservoirs to replenish the sliding contact with solid lubricants. The effectiveness of this new design of high temperature tribological coating was tested using a pin-on-desk tribotester. A significant decrease in the wear rate and coefficient of friction (CoF) was achieved at high temperatures (750 °C) and was maintained as a result of the storage of the Ag3VO4 phase in the dimples. After wear testing, Raman spectroscopy and XRD were used to identify the phase composition developed as a result of tribotesting. It was found that the burnished powders were more effective in enhancing the tribological properties of textured films compared to burnished/un-burnished monolithic VN coatings.

A new design of micro-evaporators, with 45 channels (View the MathML source100?m deep) and diamond-shaped fins (View the MathML source40?m wide, View the MathML source160?m long, View the MathML source20?m separation), is fabricated by anodic bonding of silicon and glass wafers, in a five masks process. This new design improves stability of the working conditions, and has a localized hot zone in the main part of the device. The measured absorbed heat includes the energy that heats up the coolant (water) from 25 to View the MathML source100?C (roughly 300 J/g) and the latent heat of evaporation (2400 J/g). The latter one is a dominant term, and heat absorption is significantly increased at fin temperatures above the water boiling point.

Edge-lit backlighting has been used extensively for a variety of small and medium-sized liquid crystal displays (LCDs). The shape, density and spatial distribution pattern of the micro-optical elements imprinted on the surface of the flat light-guide panel (LGP) are often "optimized" to improve the overall brightness and luminance uniformity. A similar concept can be used to develop interior convenience lighting panels and exterior tail lamps for automotive applications. However, costly diffusive sheeting and brightness enhancement films are not be considered for these applications because absolute luminance uniformity and the minimization of Moiré fringe effects are not significant factors in assessing quality of automotive lighting. A new design concept that involves micromilling cylindrical micro-optical elements on optically transparent plastic substrates is described in this paper. The variable parameter that controls illumination over the active regions of the panel is the depth of the individual cylindrical micro-optical elements. LightToolsTM is the optical simulation tool used to explore how changing the micro-optical element depth can alter the local and global luminance. Numerical simulation and microfabrication experiments are performed on several (100mmx100mmx6mm) polymethylmethacrylate (PMMA) test samples in order to verify the illumination behavior. © 2012 SPIE., SPIE MOEMS-MEMS, January 24-26, 2012, San Francisco, California, USA, Series: Proceedings of SPIE; no. 8248

This paper presents a framework for re-designing a failed automotive component subjected to cyclic loading. In the automotive industry, some parts fail before completing their design life. These failed components have to be re-designed using modern optimisation tools. In this paper, a failed clutch fork was completely re-designed using topology and the shape optimisation approach. Stress-life fatigue analysis was conducted to correlate the crack location between the failed component and the simulation model. A new design proposal was determined with the topology optimisation approach, and then design optimisation by response surface methodology was effectively used to improve the new clutch fork design. The mass reduction obtained was 24%. A maximum stress reduction of 9% was achieved, and the rigidity was improved up to 37% in comparison to the original clutch fork.