A friction energy approach to quantifying lubrication under fretting sliding

The problem of a proper lubrication under low‐speed small oscillatory movement can be a decisive factor for the reliability of various components. There is a need to characterise the lubricious behaviour of the interface under oil‐bath fretting wear conditions for ball bearing applications. Fast and reliable methods to quantify this behaviour for broad range of mechanical conditions are proposed and validated. Pure sliding reciprocation induces mixed lubrication mode. It was found that transient film profiles depend on the non‐Newtonian response of the oils and the type of motion. Running‐in period has a crucial importance for the tribofilm formation, and is a result of the interplay of the oil‐sliding surfaces interface and is directly connected with the total energy dissipated from the contact region. The stability of structured tribofilm in steady‐state period relies on the balance between the competitive processes: replenishment of the oil to the contact and ejection of the oil pending the oscillatory movement. The phenomenon of starvation was observed when the system was moved away from dynamical equilibrium and the growth of the dissipated energy was spotted. A proposed methodology provides the evaluation of the lubrication properties of the oil in a quantitative way. Copyright © 2010 John Wiley & Sons, Ltd.     

A new tantalum sulfur compound as electrode material for non-aqueous alkali metal batteries

Polycrystalline (PbS)_1.14(TaS₂)₂, a misfit layer sulfide, was used as cathodic material for lithium secondary battery. One molar LiClO₄ in propylene carbonate (PC) was used as electrolyte. The cell could be galvanostatic discharged down to x = 4.6 [Li_x(PbS)_1.14(TaS₂)₂] when the current density was 65 μA cm⁻² and the cell was cycled more than 100 times between 3.5 and 1.5 V at a current density of 260 μA cm⁻². Lattice expansion increased linearly with lithium content and was less than that reported for the Li/TaS₂ system. Chemical diffusion coefficients were determined by a modified version of the galvanostatic intermittent titration technique and they were fairly constant in the composition range 0.2 < x < 1, and an average value of 8.1 × 10⁻¹¹ cm² s⁻¹ was calculated. Sodium intercalation was also accomplished, but the uptake of this ion resulting in a significant lattice expansion compared with that observed for lithium ions. Moreover, a similar dependence of the sodium chemical diffusion coefficient on the composition was observed with an average value of 1.4 × 10⁻¹⁰ cm² s⁻¹, somewhat higher than that of lithium ion. We believe that differences in lattice expansion may be responsible for the differences found in the chemical diffusivity values.     

Spectrocolorimetric and microscopic techniques for the evaluation of plasticized PVC cleaning: a case study applicable to three-dimensional objects at museums

For the validation of a cleaning method in conservation, the examination of the object's surface after the cleaning and the quantification of the cleaning efficiency are significant steps. In this study, several cleaning solutions were tested on a plasticized poly(vinyl chloride) object whose surface was characterized before and after cleaning by optical microscopy and noncontact profilometry. In addition, different methods to quantify the cleaning efficiency based on spectrocolorimetric and microscopic techniques were provided. The results showed that noncontact profilometry supported by optical microscopy and spectrocolorimetry was very useful for the characterization of the plasticized poly(vinyl chloride) surface before and after the cleaning and also for the determination of the cleaners' efficiency.     

The powder metallurgy processing of refractory metals and alloys

Molybdenum and tungsten are refractory metals in the elemental form with the largest production volume in the world. The fabrication of these refractory metals, as well as their alloys and intermetallics, using high-temperature powder metallurgy (PM) is reviewed in this article. The primary focus is on the role of traditional high-temperature PM in producing alloys with tailor-made properties. An insight into the bulk production of molybdenum and tungsten alloys with nano-grains is highlighted. For more information, contact R.E. Aune, Royal Institute of Technology, Department of Materials Science and Engineering, SE-100 44 Stockholm, Sweden;+46-8-790-8363;fax+46-8-790-0939;e-mail aune@mse.kth.se.     

New learning rules for the ASSOM network

The ASSOM is a self-organising neural network with the capability of adapting to linear subspaces. Here we propose two new methods to train the ASSOM network. A nonlinear system of equations is derived for network training. This system can be solved by a gradient-based approach or by the Levenberg–Marquardt method. Each of these two approaches gives a different learning rule. A comparison is carried out among the original Kohonens method and the proposed learning rules. Experimental results are reported, including a convergence speed experiment and a speech processing application, which show that the new learning rules have better performance than the original one.     

Do ResearchGate Scores create ghost academic reputations?

Scientometrics - Technology is a complex system with technologies relating to each other in a space that can be mapped as a network. The technology network’s structure can reveal properties...     

MR imaging of baker cysts—prevalence and relation to internal derangements of the knee

Rationale and objectives: To evaluate the prevalence of popliteal cysts in patients studied with magnetic resonance (MR) imaging. Cyst presence and volume will be related to other internal derangement of the knee.Materials and methods: Three hundred and eighty-two consecutive patients with a MR study of the knee were included. Images were obtained in the three spatial orthogonal planes and evaluated through consensus. Four categories were established for the Baker cyst and synovial fluid (absence, minimum, moderate and massive), and the presence of meniscal, cruciate ligaments and cartilage lesions were recorded. Statistical analysis was carried out with bivariate analysis (χ² of Pearson and Gamma tests).Results: From the 382 patients, 145 had Baker cysts (38.0%). Cyst content was minimum in 99, moderate in 34 and massive in 12. Joint effusion was observed in 269 patients (70.4%), being minimal in 140 patients, moderate in 119 and massive in ten. Meniscal lesions were observed in 195 patients (51%), while 58 patients (15%) had a cruciate ligament lesion. Baker cyst has a statistically significant direct relationship with the presence and quantity of synovial fluid (P=0.002) and with the presence and type of meniscal lesion (P=0.01) but not with cruciate ligaments or cartilage lesions.Conclusions: The prevalence of Baker cysts in MR studies of the knee is high. Its presence and volume are related to the quantity of synovial fluid, and to the presence and severity of meniscal lesions.     

A model for post-occlusive reactive hyperemia as measured with laser-Doppler perfusion monitoring

To facilitate the quantitative analysis of post-occlusive reactive hyperaemia (PORH), measured with laser-Doppler perfusion monitoring (LDPM) on extremities, we present a flow model for the dynamics of the perfusion of the tissue during PORH, based on three parameters: two time constants (tau1 and tau2) and the ratio of the maximum flux and the resting flux. With these three constants quantitative comparisons between experiments will be possible and, therefore, we propose to adopt this approach as future standard. For this reason, we also developed a computer program to perform the fit of the model to measured data.     

Architecture-aware optimization of an HEVC decoder on asymmetric multicore processors

Low-power asymmetric multicore processors (AMPs) have attracted considerable attention due to their appealing performance/power ratio for energy-constrained environments. However, these processors pose a significant programming challenge due to the integration of cores with different performance capabilities, asking for an asymmetry-aware scheduling solution that carefully distributes the workload. The recent HEVC standard, which offers several high-level parallelization strategies, is an important application that can benefit from an implementation tailored for the low-power AMPs present in many current mobile or handheld devices. In this scenario, we present an architecture-aware implementation of an HEVC decoder that embeds a criticality-aware scheduling strategy tuned for a Samsung Exynos 5422 System-on-Chip furnished with an ARM big.LITTLE AMP. The performance and energy efficiency of our solution are further enhanced by exploiting the NEON vector engine available in the ARM big.LITTLE architecture. Our experimental results expose a 1080p real-time HEVC decoding at 24 frames/s and a reduction of energy consumption over 20 %.