Tribological Performance of Advanced Polymeric Coatings Under Extreme Operating Conditions

Polymers and their composites have favorable tribological performance such as low coefficient of friction (COF) and good corrosion resistance, when working as bearing materials. The present work is studying the tribological performance of thin (~ 10s of microns) high-bearing polymeric coatings under extreme working conditions, including high temperature, cryogenic temperature, high contact pressure, high chamber pressure, starved lubrication, and abrasive wear. This work is an important contribution in proving the concept of application of thin polymeric coatings in environments such as dry sliding bearing, valve sealing surfaces, hydrodynamic bearings and drilling application under different extreme working conditions. Three groups of polymers, namely Polytetrafluoroethylene (PTFE)-based, Polyether ether ketone (PEEK)-based, and Aromatic Thermosetting coPolyesters(ATSP)-based coatings were extensively studied. Out of the three groups of polymers, ATSP-based coating showed the most desirable tribological performance: ‘zero wear’ at different temperature from -160°C to 260°C with dry sliding, extremely low wear coefficient (4.15×10⁻⁸ mm³/Nm) under starved lubrication condition, stable coefficient of friction (COF) and low wear rate under sand abrasive condition, and extreme low COF for oil and gas drilling application. Traditionally, the friction force between two solids is attributed to adhesion and deformation effects; where the adhesion force involves the shearing between the real contact surfaces and deformation is due to the hard material‘s asperities plowing on the softer material. This work proposes a phenomenological model of friction for viscoelastic materials by using the viscosity and elasticity parameters acquired by nano-indentation measurements at elevated temperatures. Substituting the viscosity and elastic modulus terms, the model showed reasonable COF for the coatings up to temperatures that were lower than the glass transition temperature

Tai Ji Quan: An overview of its history, health benefits, and cultural value

AbstractTai Ji Quan is considered to be a part of traditional Chinese Wushu (a martial art) and comprises various styles that have evolved historically from the Chen, Yang, Wǔ, Wú, and Sun families (schools). Recent simplification of the original classic styles has made Tai Ji Quan easier to adopt in practice. Thus, the traditional legacy of using Tai Ji Quan for self-defense, mindful nurturing of well-being, and fitness enhancement has been expanded to more contemporary applications that focus on promoting physical and mental health, enhancing general well-being, preventing chronic diseases, and being an effective clinical intervention for diverse medical conditions. As the impact of Tai Ji Quan on physical performance and health continues to grow, there is a need to better understand its historical impact and current status. This paper provides an overview of the evolution of Tai Ji Quan in China, its functional utility, and the scientific evidence of its health benefits, as well as how it has been a vehicle for enhancing cultural understanding and exchanging between East and West

Which method is best for the induction of labour?: A systematic review, network meta-analysis and cost-effectiveness analysis

Background: More than 150,000 pregnant women in England and Wales have their labour induced each year. Multiple pharmacological, mechanical and complementary methods are available to induce labour. Objective: To assess the relative effectiveness, safety and cost-effectiveness of labour induction methods and, data permitting, effects in different clinical subgroups. Methods: We carried out a systematic review using Cochrane methods. The Cochrane Pregnancy and Childbirth Group’s Trials Register was searched (March 2014). This contains over 22,000 reports of controlled trials (published from 1923 onwards) retrieved from weekly searches of OVID MEDLINE (1966 to current); Cochrane Central Register of Controlled Trials (The Cochrane Library); EMBASE (1982 to current); Cumulative Index to Nursing and Allied Health Literature (1984 to current); ClinicalTrials.gov; the World Health Organization International Clinical Trials Registry Portal; and hand-searching of relevant conference proceedings and journals. We included randomised controlled trials examining interventions to induce labour compared with placebo, no treatment or other interventions in women eligible for third-trimester induction. We included outcomes relating to efficacy, safety and acceptability to women. In addition, for the economic analysis we searched the Database of Abstracts of Reviews of Effects, and Economic Evaluations Databases, NHS Economic Evaluation Database and the Health Technology Assessment database. We carried out a network meta-analysis (NMA) using all of the available evidence, both direct and indirect, to produce estimates of the relative effects of each treatment compared with others in a network. We developed a de novo decision tree model to estimate the cost-effectiveness of various methods. The costs included were the intervention and other hospital costs incurred (price year 2012–13). We reviewed the literature to identify preference-based utilities for the health-related outcomes in the model. We calculated incremental cost-effectiveness ratios, expected costs, utilities and net benefit. We represent uncertainty in the optimal intervention using cost-effectiveness acceptability curves. Results: We identified 1190 studies; 611 were eligible for inclusion. The interventions most likely to achieve vaginal delivery (VD) within 24 hours were intravenous oxytocin with amniotomy [posterior rank 2; 95% credible intervals (CrIs) 1 to 9] and higher-dose (≥ 50 μg) vaginal misoprostol (rank 3; 95% CrI 1 to 6). Compared with placebo, several treatments reduced the odds of caesarean section, but we observed considerable uncertainty in treatment rankings. For uterine hyperstimulation, double-balloon catheter had the highest probability of being among the best three treatments, whereas vaginal misoprostol (≥ 50 μg) was most likely to increase the odds of excessive uterine activity. For other safety outcomes there were insufficient data or there was too much uncertainty to identify which treatments performed ‘best’. Few studies collected information on women’s views. Owing to incomplete reporting of the VD within 24 hours outcome, the cost-effectiveness analysis could compare only 20 interventions. The analysis suggested that most interventions have similar utility and differ mainly in cost. With a caveat of considerable uncertainty, titrated (low-dose) misoprostol solution and buccal/sublingual misoprostol had the highest likelihood of being cost-effective. Limitations: There was considerable uncertainty in findings and there were insufficient data for some planned subgroup analyses. Conclusions: Overall, misoprostol and oxytocin with amniotomy (for women with favourable cervix) is more successful than other agents in achieving VD within 24 hours. The ranking according to safety of different methods was less clear. The cost-effectiveness analysis suggested that titrated (low-dose) oral misoprostol solution resulted in the highest utility, whereas buccal/sublingual misoprostol had the lowest cost. There was a high degree of uncertainty as to the most cost-effective intervention

Tai chi illustrated/ Qiu

vii, 231 hal. ; ill, : 26 cm

Tai chi illustrated/ Qiu

vii, 231hal. ; ill, : 26 cm

Health benefits of traditional Chinese sports and physical activity for older adults: A systematic review of evidence

Background: Traditional Chinese sports and physical activities (PAs) have a long history and are practiced by millions of Chinese. However, relatively few systematic reviews of the scientific evidence for their health benefits, especially for older Chinese adults, have been undertaken. Evidence acquisition: Between January and March 2016, a systematic search was conducted using the CNKI and PubMed databases to identify studies published between 2000 and 2015. Studies were selected for review if they were designed specifically to evaluate the health benefits of traditional Chinese sports and PAs in adults aged 50 years and older in the Mainland of China. The studies included observational, uncontrolled, and randomized and controlled designs. Papers published without an English title or abstract were excluded. Evidence synthesis: The initial search identified a total of 229 studies. After removing duplicates and studies that did not meet the inclusion/exclusion criteria, 95 studies were selected for review. Special attention was given to studies of the most commonly practiced activities: Tai Ji Quan, Qigong, and Yangko exercises. A positive association between these types of exercise and health benefits was noted for healthy older adults and those with chronic diseases. Evidence on other types of activities was less clear due to the limited number of studies conducted. Conclusion: There is promising evidence that traditional Chinese sports and PAs provide many health benefits for older Chinese adults. While additional scientifically rigorous research is warranted, promoting these traditional and culturally-based sports and PAs as forms of behavioral medicine in primary and secondary prevention of diseases among the aging Chinese population will help fulfill an urgent public health need

Wear Performance of Metal Materials Fabricated by Powder Bed Fusion: A Literature Review

Powder Bed Fusion (PBF) is an additive manufacturing technology used to produce metal-based materials. PBF materials have a unique microstructure as a result from repeated and sharp heating/cooling cycles. Many researches have been carried out on relations between processing parameters of the PBF technology, obtained microstructures and mechanical properties. However, there are few studies on the tribological properties of PBF materials at various contact conditions. This article describes previous and recent studies related to the friction performance. This is a critical aspect if PBF materials are applied to friction pair components. This paper discusses wear rates and wear mechanisms of PBF materials under dry friction, boundary lubrication and micro-motion conditions. PBF materials have higher hardness due to fine grains. PBF materials have a higher wear resistance than traditional materials due to their solid solution strengthening. In addition, hard particles on the surface of PBF components can effectively reduce wear. The reasonable combination of process parameters can effectively improve the density of parts and thus further improve the wear resistance. This review paper summarized the wear behavior of PBF materials, the wear mechanism of metal materials from dry friction to different lubrication conditions, and the wear behavior under fretting wear. This will help to control the processing parameters and material powder composition of parts, so as to achieve the required material properties of parts and further improve the wear performance

Anti-overturning safety performance investigation for single column pier bridge

Under eccentric load, a single column pier bridge often overturns. In order to study the anti overturning performance of a single column pier bridge, taking the accident bridge in Wuxi as an example, a finite element model is established based on ABAQUS. According to the model simulation results, the relationship between the ultimate rotational load and overturning load of the accident bridge is obtained, and the ratio of the latter to the former is 1.75. Based on the model, the stress state, displacement state, and support state of the accident bridge under dead load, highway class I vehicle load, and accident vehicle load are obtained. Whether the strength and stability of the accident bridge under each load meet the service requirements is analyzed. In order to explore the differences among China, United States, and Japan specifications, the lateral stability of accident bridges is checked. It is found that the safety of the United States and Japan specifications is conservative, but the utilization rate of bridge traffic capacity is low. The safety of China specifications is slightly lower, but it can maximize the bridge’s traffic capacity and judge the ultimate overturning state of the bridge more accurately. The research results can provide technical references for the design and application of a single-column pier bridge

Upgrading of the bench drilling machine's manual feeding to automatic feeding system

Conference Name:3rd international Conference on Manufacturing Science and Engineering, ICMSE 2012. Conference Address: Xiamen, China. Time:March 27, 2012 - March 29, 2012.Fujian University of Technology; Xiamen University; Fuzhou University; Huaqiao University; University of WollongongBench drilling machine is compact and flexible. But in the mass production, as the feeding of the machine is rely on manual work, the workers are easily to be exhausted and the manual production is not effective. This thesis gives a brief introduction of process of designing the automatic feeding device which is based on PLC for the Z512-drilling machine. The thesis demonstrates the device's construction and control logic. This device can save works' labor, time, easily to be produced and has a valuable application. 漏 (2012) Trans Tech Publications, Switzerland