| 1. |
- Mishra, A, et al.
(författare)
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Diminishing benefits of urban living for children and adolescents' growth and development
- 2023
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 615:7954, s. 874-883
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Tidskriftsartikel (refereegranskat)abstract
- Optimal growth and development in childhood and adolescence is crucial for lifelong health and well-being1–6. Here we used data from 2,325 population-based studies, with measurements of height and weight from 71 million participants, to report the height and body-mass index (BMI) of children and adolescents aged 5–19 years on the basis of rural and urban place of residence in 200 countries and territories from 1990 to 2020. In 1990, children and adolescents residing in cities were taller than their rural counterparts in all but a few high-income countries. By 2020, the urban height advantage became smaller in most countries, and in many high-income western countries it reversed into a small urban-based disadvantage. The exception was for boys in most countries in sub-Saharan Africa and in some countries in Oceania, south Asia and the region of central Asia, Middle East and north Africa. In these countries, successive cohorts of boys from rural places either did not gain height or possibly became shorter, and hence fell further behind their urban peers. The difference between the age-standardized mean BMI of children in urban and rural areas was <1.1 kg m–2 in the vast majority of countries. Within this small range, BMI increased slightly more in cities than in rural areas, except in south Asia, sub-Saharan Africa and some countries in central and eastern Europe. Our results show that in much of the world, the growth and developmental advantages of living in cities have diminished in the twenty-first century, whereas in much of sub-Saharan Africa they have amplified.
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| 2. |
- Bell, S., et al.
(författare)
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METefnet : Developments in metrology for moisture in materials
- 2015
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Ingår i: 17th International Congress of Metrology, CIM 2015. - Les Ulis, France : EDP Sciences.
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Konferensbidrag (refereegranskat)abstract
- Bien que les mesures de teneur en eau soient largement utilisées dans l'industrie, les considérations métrologiques quant à cette mesure ne sont pas complètement abouties de sorte à fournir des mesures fiables et traçables au SI. Afin de remédier à ceci, le projet de recherche conjoint, Joint Research Project SIB64 “METefnet – Metrology for moisture in materials”, est actuellement en cours, et contribue au programme européen de recherche en métrologie European Metrology Research Programme. Le projet METefnet a pour objectifs de développer et d'améliorer l'approche métrologique de ce sujet. Ceci inclus notamment: le travail sur de nouvelles méthodes de référence pour évaluer la fraction massique en eau, l'amélioration des mesures mettant en œuvre la méthode primaire de type titration Karl Fischer, le développement de nouveaux matériaux de référence certifiés présentant une très bonne stabilité et permettant une traçabilité au SI, le développement de nouveaux étalons de transfert, la réalisation d'études visant à quantifier et réduire les effets liés à la prise d'échantillon, son transport et sa manipulation, le développement d'une nouvelle méthode pour étalonner les instruments mesurant l'humidité de surface, et l'amélioration des méthodes d'estimation d'incertitudes de ces mesures. Ce travail, réalisé dans le domaine de la métrologie de l'humidité au sein des matériaux, couvre à la fois le mesurande décrit comme étant spécifiquement la teneur en eau, seule, dans les matériaux, mais également un mesurande plus large pouvant inclure l'eau ainsi que d'autres liquides ou composés organiques volatiles; ceci afin de bien mettre en exergue la différence qui peut être observée entre ces deux mesurandes. Le projet global a pour objectif de soutenir une action de dissémination et de traçabilité au système SI des mesures de teneur en eau dans les matériaux avec une exactitude optimale et de développer une infrastructure métrologique cohérente pour ce type de mesures. Le travail technique ainsi que les dernières avancées vous sont ainsi présentées.
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| 3. |
- Pervaiz, S., et al.
(författare)
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An experimental analysis of energy consumption in milling strategies
- 2012
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Ingår i: 2012 International Conference on Computer Systems and Industrial Informatics, ICCSII 2012. - : IEEE. - 9781467351577 ; , s. 6454527-
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Konferensbidrag (refereegranskat)abstract
- Pocket milling operation is one of the widely used milling operations. CAM packages offer different tool path strategies to execute a machining operation. In the presented work zigzag, constant overlap spiral, parallel spiral and oneway tool path strategies were compared in terms of power and energy consumption for pocket milling of Al 6061 aluminum alloy. All pocketing operations were conducted using 8 mm diameter High Speed Steel (HSS) end milling cutters. Energy utilization was analysed for all tool path strategies. This work aims to develop better understanding towards sustainability concept in core machining phase.
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| 4. |
- Pervaiz, Salman, et al.
(författare)
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An experimental investigation on effect of minimum quantity cooling lubrication (MQCL) in machining titanium alloy (Ti6Al4V)
- 2016
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Ingår i: The International Journal of Advanced Manufacturing Technology. - : Springer London. - 0268-3768 .- 1433-3015. ; 87:5-8, s. 1371-1386
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Tidskriftsartikel (refereegranskat)abstract
- During the machining operation, elevated temperatures are achieved at the cutting interface due to the presence of high plastic deformation and friction in between the tool and chip contacting area. Efficient heat dissipation from the cutting interface is required to achieve better machining performance. Elevated temperature in the cutting area results in lower tool life as it facilitates different types of wear mechanisms. Metal working fluids (MWFs) are employed to reduce heat and friction in the cutting zone, simultaneously to help in the flushing of waste particles. The MWFs are based on either water or petroleum oil and include several additives which make them non-biodegradable and toxic in nature. The minimum quantity lubrication (MQL) method offers a feasible substitute to the MWF-based conventional flood cooling method. In this study, a vegetable oil-based MQL system was mixed with sub-zero temperature air to design a new minimum quantity cooling lubrication (MQCL) system. The study investigates the machinability of Ti6Al4V using an MQCL system under various oil flow rates and compared its machining performance with both dry cutting and conventional flood cooling. For further evaluation, the study investigated surface roughness, flank wear, and associated wear mechanisms. It was found that in the MQCL system (60–70 ml/h), oil supply rates provided reliable machining performance at higher feed levels.
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| 5. |
- Pervaiz, Salman, et al.
(författare)
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Experimental and numerical investigation of Ti6A14V alloy machinability using TiAIN coated tools
- 2014
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Ingår i: Transactions of the North American Manufacturing Research Institution of SME. - : Society of Manufacturing Engineers. ; , s. 104-113
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Konferensbidrag (refereegranskat)abstract
- Titanium alloys exhibit extraordinary characteristics such as excellent strength-to-weight ratio, superior corrosive and erosive resistance and capability to operate at high operating temperatures. These alloys show poor machinability rating due their low thermal conductivity and high chemical reactivity. This study investigates the machinability of Ti6A14V using TiAIN coated tools by analyzing cutting forces and cutting temperatures. The simulated cutting force data was used to predict the total energy utilized by the process. Cutting tool temperatures during the machining operation were measured by an Infrared (IR) camera with cutting forces experiments. Finite element simulations can offer a cost effective solution when evaluating the machining performance of difficult to cut materials such as Titanium alloys. The study incorporated modified Johnson-Cook constitutive equation and friction model to develop the finite element simulations of the machining process. The finite element simulated results of forces and tool temperature presented good agreement with the experimental results. Copyright
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| 6. |
- Pervaiz, S., et al.
(författare)
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Performance evaluation of TiAlN- PVD coated inserts for machining Ti-6Al-4V under different cooling strategies
- 2013
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Ingår i: Advanced Materials Research III. - : Trans Tech Publications Inc.. - 9783037856765 ; , s. 68-75
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Konferensbidrag (refereegranskat)abstract
- Titanium alloys are labeled as difficult to materials because of their low machinability rating. This paper presents an experimental study of machining Ti-6Al-4V under turning operation. All machining tests were conducted under dry, mist and flood cooling approaches by using a TiAlN coated carbide cutting inserts. All cutting experiments were conducted using high and low levels of cutting speeds and feed rates. The study compared surface finish of machined surface and flank wear at cutting edge under dry, mist and flood cooling approaches. Scanning electron microscopy was utilized to investigate the flank wear at cutting edge under various cooling approaches and cutting conditions. Investigation revealed that TiAlN coated carbides performed comparatively better at higher cutting speed.
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| 7. |
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