Vibration analysis of viscoelastic single-walled carbon nanotubes resting on a viscoelastic foundation

Vibration responses were investigated for a viscoelastic Single-walled carbon nanotube (visco-SWCNT) resting on a viscoelastic foundation. Based on the nonlocal Euler-Bernoulli beam model, velocity-dependent external damping and Kelvin viscoelastic foundation model, the governing equations were derived. The Transfer function method (TFM) was then used to compute the natural frequencies for general boundary conditions and foundations. In particular, the exact analytical expressions of both complex natural frequencies and critical viscoelastic parameters were obtained for the Kelvin-Voigt visco-SWCNTs with full foundations and certain boundary conditions, and several physically intuitive special cases were discussed. Substantial nonlocal effects, the influence of geometric and physical parameters of the SWCNT and the viscoelastic foundation were observed for the natural frequencies of the supported SWCNTs. The study demonstrates the efficiency and robustness of the developed model for the vibration of the visco-SWCNT-viscoelastic foundation coupling system

Effects of Anacetrapib in Patients with Atherosclerotic Vascular Disease

BACKGROUND: Patients with atherosclerotic vascular disease remain at high risk for cardiovascular events despite effective statin-based treatment of low-density lipoprotein (LDL) cholesterol levels. The inhibition of cholesteryl ester transfer protein (CETP) by anacetrapib reduces LDL cholesterol levels and increases high-density lipoprotein (HDL) cholesterol levels. However, trials of other CETP inhibitors have shown neutral or adverse effects on cardiovascular outcomes. METHODS: We conducted a randomized, double-blind, placebo-controlled trial involving 30,449 adults with atherosclerotic vascular disease who were receiving intensive atorvastatin therapy and who had a mean LDL cholesterol level of 61 mg per deciliter (1.58 mmol per liter), a mean non-HDL cholesterol level of 92 mg per deciliter (2.38 mmol per liter), and a mean HDL cholesterol level of 40 mg per deciliter (1.03 mmol per liter). The patients were assigned to receive either 100 mg of anacetrapib once daily (15,225 patients) or matching placebo (15,224 patients). The primary outcome was the first major coronary event, a composite of coronary death, myocardial infarction, or coronary revascularization. RESULTS: During the median follow-up period of 4.1 years, the primary outcome occurred in significantly fewer patients in the anacetrapib group than in the placebo group (1640 of 15,225 patients [10.8%] vs. 1803 of 15,224 patients [11.8%]; rate ratio, 0.91; 95% confidence interval, 0.85 to 0.97; P=0.004). The relative difference in risk was similar across multiple prespecified subgroups. At the trial midpoint, the mean level of HDL cholesterol was higher by 43 mg per deciliter (1.12 mmol per liter) in the anacetrapib group than in the placebo group (a relative difference of 104%), and the mean level of non-HDL cholesterol was lower by 17 mg per deciliter (0.44 mmol per liter), a relative difference of -18%. There were no significant between-group differences in the risk of death, cancer, or other serious adverse events. CONCLUSIONS: Among patients with atherosclerotic vascular disease who were receiving intensive statin therapy, the use of anacetrapib resulted in a lower incidence of major coronary events than the use of placebo. (Funded by Merck and others; Current Controlled Trials number, ISRCTN48678192 ; ClinicalTrials.gov number, NCT01252953 ; and EudraCT number, 2010-023467-18 .)

The evolution of foil bearing technology

This paper presents a state-of-the-art survey on the development of the foil bearing technology. Foil bearings represent a proven technology with many promising features. Nevertheless, there are a number of inherent challenges in their designs, analyses, and performance characteristics that must be taken into consideration for proper functionality and safe operation. To this end, complexities associated with geometrical configurations with the compressible flow, dynamic performance and stability associated with stiffness and damping, frictional characteristics associated with low- and high-speed operations, and thermoelastic instability leading to thermally-induced runaway are discussed in depth with particular attention to their progressive evolutions

Nanolubricants dispersed with graphene and its derivatives: an assessment and review of the tribological performance

Graphene, being a path-breaking discovery of this millennium, has become one of the most researched materials lately. Recently, researchers have been exploring the possibilities of utilizing graphene as a dispersoid in a nanolubricant (a stable colloidal suspension of nanoparticles in conventional lubricant). This state-of-the-art review presents an overview of recent developments that have taken place regarding the tribological performance of different types of nanolubricants dispersed with graphene and its derivatives. The derivatives of graphene include surface functionalized graphene, graphene decorated with nanoparticles and composites of graphene with other nanomaterials. The authors have thoroughly assessed the tribological performance of graphene nanolubricants which exhibit improved tribological performances in comparison to existing lubricants. The most important parameters which affect friction characteristics of interacting solid surfaces under the influence of graphene nanolubricants are concentration of the dispersoid, number of layers of graphene nanosheets, dispersion stability and the lubrication conditions. The effects of different parameters and underlying mechanisms explaining the superior performance of these nanolubricants are thoroughly surveyed in this article. The authors also explored various domains of applications in which graphene nanolubricants, having improved tribological performance, are potential candidates for future applications