Embeddability behaviour of some Pb-free engine bearing materials in the presence of abrasive particles in engine oil

One of the tribological requirements on engine bearing material is its ability to safely embed contaminant particles onto its surface and minimise damage to both the bearing and crankshaft surfaces. In this work, a journal bearing test rig that operates under constant load has been employed to investigate the embeddability behaviour of selected multi-layered Pb-free engine bearing materials at three different rotational speeds using engine oil contaminated with SiC particles. Experimental results have shown that third-body abrasive wear is influenced by the lubricant film thickness. There was also difference in embeddability of the different materials. Bismuth-based overlay and MoS₂ containing polyamide-imide-based overlay-coated materials show higher wear compared to tin-based overlay and a polyamide-imide-based composite overlay-coated material. Steel counter surfaces sliding against bismuth-based overlay and MoS₂ containing polyamide-imide-based overlay exhibited higher wear than those sliding against tin-based overlay and polyamide-imide-based composite overlay.     

Design and realization of a 1.55-μm patterned vertical cavitysurface emitting laser with lattice-mismatched mirror layers

It is possible to grow defect-free strained layers on patterned substrates (mesas or grooves) up to thicknesses far exceeding the critical thickness. Defect nucleation and propagation are inhibited in such growth. We have exploited this property to propose a novel InP-based 1.55-μm vertical cavity surface emitting lasers (VCSEL's). Careful photoluminescence and transmission electron microscopy (TEM) studies have confirmed that there are no propagating defects in the GaAs/Al_xGa_1-xAs distributed Bragg reflector (DBR) grown on the patterned InP-based heterostructures, specifically in the multiquantum-well (MQW) region. Lasers were designed with InP/InGaAsP bottom mirrors, InAlAs-oxide current confinement and short-stack GaAs/Al _xO_y top DBR mirrors. An optimal reflectivity and a maximum wall plug efficiency are determined analytically for this structure. In addition, a theoretical analysis of the modulation response of this device is performed using a rate equation model. Both analyzes show the potential of such a device for implementation in practical designs where high power and modulation bandwidth are required. Lasers with 8-40 μm diameter have been fabricated and characterized. A threshold current of 5 mA is observed at 15°C for an 8 μm diameter device; and up to 60 μW of light output is recorded     

Low Complexity Radio Mobile Speed Estimation Using Count of Received Envelop Peaks and Troughs

Wireless Personal Communications - Future high densification wireless networks come with high handoff rates, which require knowledge of mobile speed. Mobile speed estimation is crucial for...     

Hormone replacement therapy and endometrial cancer risk: a meta-analysis

OBJECTIVE: To assess the association of unopposed estrogen or estrogen plus progestin and the risk of developing endometrial cancer or dying of that disease. DATA SOURCES: A literature search of English-language studies was performed using MEDLINE, a review of bibliographies, and consultations with experts. METHODS OF STUDY SELECTION: We identified 30 studies with adequate controls and risk estimates. DATA EXTRACTION AND SYNTHESIS: Risk estimates were extracted by two authors and summarized using meta-analytic methods. The summary relative risk (RR) was 2.3 for estrogen users compared to nonusers (95% confidence interval [CI] 2.1-2.5), with a much higher RR associated with prolonged duration of use (RR 9.5 for 10 or more years). The summary RR of endometrial cancer remained elevated 5 or more years after discontinuation of unopposed estrogen therapy (RR 2.3). Interrupting estrogen for 5-7 days per month was not associated with lower risk than daily use. Users of unopposed conjugated estrogen had a greater increase in RR of developing endometrial cancer than users of synthetic estrogens. The risk for endometrial cancer death was elevated among unopposed estrogen users (RR 2.7, 95% CI 0.9-8.0). Among estrogen plus progestin users, cohort studies showed a decreased risk of endometrial cancer (RR 0.4), whereas case-control studies showed a small increase (RR 1.8). CONCLUSIONS: Endometrial cancer risk increases substantially with long duration of unopposed estrogen use, and this increased risk persists for several years after discontinuation of estrogen. Although not statistically significant, the risk of death from endometrial cancer among unopposed estrogen users is increased, similar to the increased risk of developing the disease. Data regarding risk for endometrial cancer among estrogen plus progestin users are limited and conflicting.