The Behavior of Treated Metal Curvature Cup: Improving Friction in Hard on Hard Sliding Contact

AbstractThis research investigated the tribology on the metal curvature surface in lubricated of palm olein to determine pits capability friction in hard on hard sliding contact. The study was performed using a four-ball tribotester with holder cup modified and digital microscope. The sliding friction between untreated and treated curve cup were evaluated. The experiment was conducted of constant parameters as speed; load and time under the American Society for Testing and Materials (ASTM), number D 4172. To evaluate lubricant ability all results of this research were compared to findings regarding mineral oil. For qualitative analysis worn wear on the curvature cup without applying lubricant to the sample. The results showed that, the measured friction was low significantly influenced by the treated curvature surface embedded with pits and palm olein as potential anti-friction bio-lubricant

Tribological behaviour of refined bleached and deodorized palm olein in different loads using a four-ball tribotester

AbstractVegetable oil is one of the bio-oils that have been promoted to replace petroleum-based products due to its eco- friendly characteristics. Palm oil has high productivity rate, and so it could fulfil the demand for a bio-lubricant. In this paper, the influence of the normal load on friction and wear performance were investigated for a RBD palm olein and compared with paraffinic mineral oil using four-ball tribotester. The normal load was varied from 30 kg to 60 kg. All experimental works were conforming to ASTM D 4172. The results exhibited that the RBD palm olein has lower coefficient of friction compared to paraffinic mineral oil. However, the wear scar of ball bearings lubricated with RBD palm olein showed larger diameter compared to paraffinic mineral oil. As a conclusion, RBD palm olein has better performance compared to paraffinic mineral oil in terms of capability to reduce friction

Surface modification of biomaterial embedded with pits using die sinker machine

Surface modification has been applied in many ways to enhance exclusive implant product. Electrical Discharge Machine Die Sinker (EDM DS) is a new approach to machine a macro surface on the biomaterial. In this study, investigations of current properties of EDM DS to obtain a new surface in titanium alloy (Ti-6Al-4V) and stainless steel (E-316-L), which placed pit on the material-sized (25 mm) diameter sample with a radius of 6.3 mm, were conducted. All the samples of concave textured circular pits with a fixed diameter and depth of 0.5 mm were successfully machined. This study revealed that the pits were produced in the concave cup and the lubricant was confined inside the pits, making easier contact between metal ball and metal concave surface. The results also show that the discharge machine is an attractive machining method for surface modification of biomaterial. This paper suggests that concave implant surface embedded with pits will work as a trap for lubricant and wear debris; in addition, it is possible to increase the lifespan of implant structure

Worldwide trends in underweight and obesity from 1990 to 2022: a pooled analysis of 3663 population-representative studies with 222 million children, adolescents, and adults

Background Underweight and obesity are associated with adverse health outcomes throughout the life course. We estimated the individual and combined prevalence of underweight or thinness and obesity, and their changes, from 1990 to 2022 for adults and school-aged children and adolescents in 200 countries and territories. Methods We used data from 3663 population-based studies with 222 million participants that measured height and weight in representative samples of the general population. We used a Bayesian hierarchical model to estimate trends in the prevalence of different BMI categories, separately for adults (age ≥20 years) and school-aged children and adolescents (age 5–19 years), from 1990 to 2022 for 200 countries and territories. For adults, we report the individual and combined prevalence of underweight (BMI <18·5 kg/m2) and obesity (BMI ≥30 kg/m2). For schoolaged children and adolescents, we report thinness (BMI <2 SD below the median of the WHO growth reference) and obesity (BMI >2 SD above the median). Findings From 1990 to 2022, the combined prevalence of underweight and obesity in adults decreased in 11 countries (6%) for women and 17 (9%) for men with a posterior probability of at least 0·80 that the observed changes were true decreases. The combined prevalence increased in 162 countries (81%) for women and 140 countries (70%) for men with a posterior probability of at least 0·80. In 2022, the combined prevalence of underweight and obesity was highest in island nations in the Caribbean and Polynesia and Micronesia, and countries in the Middle East and north Africa. Obesity prevalence was higher than underweight with posterior probability of at least 0·80 in 177 countries (89%) for women and 145 (73%) for men in 2022, whereas the converse was true in 16 countries (8%) for women, and 39 (20%) for men. From 1990 to 2022, the combined prevalence of thinness and obesity decreased among girls in five countries (3%) and among boys in 15 countries (8%) with a posterior probability of at least 0·80, and increased among girls in 140 countries (70%) and boys in 137 countries (69%) with a posterior probability of at least 0·80. The countries with highest combined prevalence of thinness and obesity in school-aged children and adolescents in 2022 were in Polynesia and Micronesia and the Caribbean for both sexes, and Chile and Qatar for boys. Combined prevalence was also high in some countries in south Asia, such as India and Pakistan, where thinness remained prevalent despite having declined. In 2022, obesity in school-aged children and adolescents was more prevalent than thinness with a posterior probability of at least 0·80 among girls in 133 countries (67%) and boys in 125 countries (63%), whereas the converse was true in 35 countries (18%) and 42 countries (21%), respectively. In almost all countries for both adults and school-aged children and adolescents, the increases in double burden were driven by increases in obesity, and decreases in double burden by declining underweight or thinness. Interpretation The combined burden of underweight and obesity has increased in most countries, driven by an increase in obesity, while underweight and thinness remain prevalent in south Asia and parts of Africa. A healthy nutrition transition that enhances access to nutritious foods is needed to address the remaining burden of underweight while curbing and reversing the increase in obesit

Height and body-mass index trajectories of school-aged children and adolescents from 1985 to 2019 in 200 countries and territories: a pooled analysis of 2181 population-based studies with 65 million participants

Summary Background Comparable global data on health and nutrition of school-aged children and adolescents are scarce. We aimed to estimate age trajectories and time trends in mean height and mean body-mass index (BMI), which measures weight gain beyond what is expected from height gain, for school-aged children and adolescents. Methods For this pooled analysis, we used a database of cardiometabolic risk factors collated by the Non-Communicable Disease Risk Factor Collaboration. We applied a Bayesian hierarchical model to estimate trends from 1985 to 2019 in mean height and mean BMI in 1-year age groups for ages 5–19 years. The model allowed for non-linear changes over time in mean height and mean BMI and for non-linear changes with age of children and adolescents, including periods of rapid growth during adolescence. Findings We pooled data from 2181 population-based studies, with measurements of height and weight in 65 million participants in 200 countries and territories. In 2019, we estimated a difference of 20 cm or higher in mean height of 19-year-old adolescents between countries with the tallest populations (the Netherlands, Montenegro, Estonia, and Bosnia and Herzegovina for boys; and the Netherlands, Montenegro, Denmark, and Iceland for girls) and those with the shortest populations (Timor-Leste, Laos, Solomon Islands, and Papua New Guinea for boys; and Guatemala, Bangladesh, Nepal, and Timor-Leste for girls). In the same year, the difference between the highest mean BMI (in Pacific island countries, Kuwait, Bahrain, The Bahamas, Chile, the USA, and New Zealand for both boys and girls and in South Africa for girls) and lowest mean BMI (in India, Bangladesh, Timor-Leste, Ethiopia, and Chad for boys and girls; and in Japan and Romania for girls) was approximately 9–10 kg/m2. In some countries, children aged 5 years started with healthier height or BMI than the global median and, in some cases, as healthy as the best performing countries, but they became progressively less healthy compared with their comparators as they grew older by not growing as tall (eg, boys in Austria and Barbados, and girls in Belgium and Puerto Rico) or gaining too much weight for their height (eg, girls and boys in Kuwait, Bahrain, Fiji, Jamaica, and Mexico; and girls in South Africa and New Zealand). In other countries, growing children overtook the height of their comparators (eg, Latvia, Czech Republic, Morocco, and Iran) or curbed their weight gain (eg, Italy, France, and Croatia) in late childhood and adolescence. When changes in both height and BMI were considered, girls in South Korea, Vietnam, Saudi Arabia, Turkey, and some central Asian countries (eg, Armenia and Azerbaijan), and boys in central and western Europe (eg, Portugal, Denmark, Poland, and Montenegro) had the healthiest changes in anthropometric status over the past 3·5 decades because, compared with children and adolescents in other countries, they had a much larger gain in height than they did in BMI. The unhealthiest changes—gaining too little height, too much weight for their height compared with children in other countries, or both—occurred in many countries in sub-Saharan Africa, New Zealand, and the USA for boys and girls; in Malaysia and some Pacific island nations for boys; and in Mexico for girls. Interpretation The height and BMI trajectories over age and time of school-aged children and adolescents are highly variable across countries, which indicates heterogeneous nutritional quality and lifelong health advantages and risks

Rising rural body-mass index is the main driver of the global obesity epidemic in adults

Body-mass index (BMI) has increased steadily in most countries in parallel with a rise in the proportion of the population who live in cities . This has led to a widely reported view that urbanization is one of the most important drivers of the global rise in obesity . Here we use 2,009\ua0population-based studies, with measurements of height and weight in more than 112\ua0million adults, to report national, regional and global trends in mean\ua0BMI segregated by place of residence (a rural or urban area) from 1985 to 2017. We show that, contrary to the dominant paradigm, more than 55% of the global rise in mean BMI from 1985 to 2017—and more than 80% in\ua0some low- and middle-income regions—was due to increases in BMI in rural areas. This large contribution stems from the fact that, with the exception of women in sub-Saharan Africa, BMI is increasing at the same rate or faster in rural areas than in cities\ua0in low- and middle-income regions. These trends have in turn resulted in a closing—and in some countries reversal—of the gap in BMI between urban and rural areas in low- and middle-income countries, especially for women. In high-income and industrialized countries, we noted a persistently higher rural BMI, especially for women. There is an urgent need for an integrated approach to rural nutrition that enhances financial and physical access to healthy foods, to avoid replacing the rural undernutrition disadvantage in poor countries with a more general malnutrition disadvantage that entails excessive consumption of low-quality calories

Heterogeneous contributions of change in population distribution of body mass index to change in obesity and underweight NCD Risk Factor Collaboration (NCD-RisC)

From 1985 to 2016, the prevalence of underweight decreased, and that of obesity and severe obesity increased, in most regions, with significant variation in the magnitude of these changes across regions. We investigated how much change in mean body mass index (BMI) explains changes in the prevalence of underweight, obesity, and severe obesity in different regions using data from 2896 population-based studies with 187 million participants. Changes in the prevalence of underweight and total obesity, and to a lesser extent severe obesity, are largely driven by shifts in the distribution of BMI, with smaller contributions from changes in the shape of the distribution. In East and Southeast Asia and sub-Saharan Africa, the underweight tail of the BMI distribution was left behind as the distribution shifted. There is a need for policies that address all forms of malnutrition by making healthy foods accessible and affordable, while restricting unhealthy foods through fiscal and regulatory restrictions

Modular Structured Multilevel Inverter with Unified Constant-Frequency Integration Control for Active Power Filters

The increasing use of power electronics based loads in recent years has resulted in the generation of harmonic and reactive currents to the common point of coupling at which the loads are connected to. Besides the commonly used passive filters, active power filters (APFs) are gaining interest lately in canceling the reactive and harmonic currents from the nonlinear loads to ensure that the resulting total current drawn from the main incoming supply is sinusoidal. This paper presents a non- conventional inverter topology known as the Modular Structured Multilevel Inverter (MSMI) as an active power filter. With the MSMI, the harmonic content generated by the APF can be reduced as it can produce more levels of voltage than conventional inverters. Additionally, it can reduce the voltage and current ratings of the power devices used while providing the convenience for future expansion in order to achieve higher power ratings for the APF system. A Unified Constant-Frequency Integration (UCI) control technique is adopted for the MSMI APF which features constant switching frequency operation and simple analog circuitry. To demonstrate the capability of the proposed APF system, simulation results of a single-phase MSMI APF with UCI controller is presented and its performance analyzed

Development of equations through trajectories linearization for an HEPWM inverter

Harmonic elimination pulse width modulation (HEPWM) is an inverter control technique that eliminates specific harmonics of its output voltage by controlling switching signals at certain switching angles. This method offer less losses in the inverter switches since the switching frequency is 40% lower than the typical sinusoidal pulse width modulation (SPWM) technique. However, as the equations to calculate the switching angles based on the HEPWM technique are too complex to be solved online by microprocessors, simpler solutions for the switching angles are required. Simplified solutions through trajectories linearization for the HEPWM technique are proposed in this paper. A set of equations for the HEPWM technique switching angles solutions suitable for microprocessor implementation are derived and then tested for accuracy and performance through simulation using MATLAB/Simulink

Analysis on the performance of a three-phase cascaded H-bridge multilevel inverter

Previous works have pointed out the limitations of conventional inverters especially in high voltage and high power applications. In recent years, multilevel inverters are becoming increasingly popular for high power applications due to its improved harmonic profile and increased power ratings. Works on the aspect of topology, control techniques and applications of multilevel inverters have been reported in literatures. However, there are no concrete findings that actually discuss or evaluate the performance of a three-phase multilevel inverter. This paper presents some analysis on the performance of a 5-level cascaded H-bridge multilevel inverter (CHMI) based on a multi-carrier sinusoidal pulse width modulation (MSPWM) control technique. Performance analysis are made based on the results of a simulation study conducted on the operation of the CHMI using MATLAB/Simulink. The performance parameters chosen in the work include the waveform pattern, harmonic spectrum, fundamental value,and total harmonic distortion (THD) of the three-phase CHMI output voltage. From the results of the simulation study and the analysis conducted, several distinct features of the three-phase 5-level CHMI employing the MSPWM control scheme, in particular the phase disposition (PD) type of the carrier disposition (CD) method from the aspect of line voltage have been identified