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1.
  • Lozano, Rafael, et al. (författare)
  • Measuring progress from 1990 to 2017 and projecting attainment to 2030 of the health-related Sustainable Development Goals for 195 countries and territories: a systematic analysis for the Global Burden of Disease Study 2017
  • 2018
  • Ingår i: The Lancet. - : Elsevier. - 1474-547X .- 0140-6736. ; 392:10159, s. 2091-2138
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Efforts to establish the 2015 baseline and monitor early implementation of the UN Sustainable Development Goals (SDGs) highlight both great potential for and threats to improving health by 2030. To fully deliver on the SDG aim of “leaving no one behind”, it is increasingly important to examine the health-related SDGs beyond national-level estimates. As part of the Global Burden of Diseases, Injuries, and Risk Factors Study 2017 (GBD 2017), we measured progress on 41 of 52 health-related SDG indicators and estimated the health-related SDG index for 195 countries and territories for the period 1990–2017, projected indicators to 2030, and analysed global attainment. Methods: We measured progress on 41 health-related SDG indicators from 1990 to 2017, an increase of four indicators since GBD 2016 (new indicators were health worker density, sexual violence by non-intimate partners, population census status, and prevalence of physical and sexual violence [reported separately]). We also improved the measurement of several previously reported indicators. We constructed national-level estimates and, for a subset of health-related SDGs, examined indicator-level differences by sex and Socio-demographic Index (SDI) quintile. We also did subnational assessments of performance for selected countries. To construct the health-related SDG index, we transformed the value for each indicator on a scale of 0–100, with 0 as the 2·5th percentile and 100 as the 97·5th percentile of 1000 draws calculated from 1990 to 2030, and took the geometric mean of the scaled indicators by target. To generate projections through 2030, we used a forecasting framework that drew estimates from the broader GBD study and used weighted averages of indicator-specific and country-specific annualised rates of change from 1990 to 2017 to inform future estimates. We assessed attainment of indicators with defined targets in two ways: first, using mean values projected for 2030, and then using the probability of attainment in 2030 calculated from 1000 draws. We also did a global attainment analysis of the feasibility of attaining SDG targets on the basis of past trends. Using 2015 global averages of indicators with defined SDG targets, we calculated the global annualised rates of change required from 2015 to 2030 to meet these targets, and then identified in what percentiles the required global annualised rates of change fell in the distribution of country-level rates of change from 1990 to 2015. We took the mean of these global percentile values across indicators and applied the past rate of change at this mean global percentile to all health-related SDG indicators, irrespective of target definition, to estimate the equivalent 2030 global average value and percentage change from 2015 to 2030 for each indicator. Findings: The global median health-related SDG index in 2017 was 59·4 (IQR 35·4–67·3), ranging from a low of 11·6 (95% uncertainty interval 9·6–14·0) to a high of 84·9 (83·1–86·7). SDG index values in countries assessed at the subnational level varied substantially, particularly in China and India, although scores in Japan and the UK were more homogeneous. Indicators also varied by SDI quintile and sex, with males having worse outcomes than females for non-communicable disease (NCD) mortality, alcohol use, and smoking, among others. Most countries were projected to have a higher health-related SDG index in 2030 than in 2017, while country-level probabilities of attainment by 2030 varied widely by indicator. Under-5 mortality, neonatal mortality, maternal mortality ratio, and malaria indicators had the most countries with at least 95% probability of target attainment. Other indicators, including NCD mortality and suicide mortality, had no countries projected to meet corresponding SDG targets on the basis of projected mean values for 2030 but showed some probability of attainment by 2030. For some indicators, including child malnutrition, several infectious diseases, and most violence measures, the annualised rates of change required to meet SDG targets far exceeded the pace of progress achieved by any country in the recent past. We found that applying the mean global annualised rate of change to indicators without defined targets would equate to about 19% and 22% reductions in global smoking and alcohol consumption, respectively; a 47% decline in adolescent birth rates; and a more than 85% increase in health worker density per 1000 population by 2030. Interpretation: The GBD study offers a unique, robust platform for monitoring the health-related SDGs across demographic and geographic dimensions. Our findings underscore the importance of increased collection and analysis of disaggregated data and highlight where more deliberate design or targeting of interventions could accelerate progress in attaining the SDGs. Current projections show that many health-related SDG indicators, NCDs, NCD-related risks, and violence-related indicators will require a concerted shift away from what might have driven past gains—curative interventions in the case of NCDs—towards multisectoral, prevention-oriented policy action and investments to achieve SDG aims. Notably, several targets, if they are to be met by 2030, demand a pace of progress that no country has achieved in the recent past. The future is fundamentally uncertain, and no model can fully predict what breakthroughs or events might alter the course of the SDGs. What is clear is that our actions—or inaction—today will ultimately dictate how close the world, collectively, can get to leaving no one behind by 2030.
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2.
  • Murray, Christopher J. L., et al. (författare)
  • Population and fertility by age and sex for 195 countries and territories, 1950–2017: a systematic analysis for the Global Burden of Disease Study 2017
  • 2018
  • Ingår i: The Lancet. - 1474-547X .- 0140-6736. ; 392:10159, s. 1995-2051
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Population estimates underpin demographic and epidemiological research and are used to track progress on numerous international indicators of health and development. To date, internationally available estimates of population and fertility, although useful, have not been produced with transparent and replicable methods and do not use standardised estimates of mortality. We present single-calendar year and single-year of age estimates of fertility and population by sex with standardised and replicable methods. Methods: We estimated population in 195 locations by single year of age and single calendar year from 1950 to 2017 with standardised and replicable methods. We based the estimates on the demographic balancing equation, with inputs of fertility, mortality, population, and migration data. Fertility data came from 7817 location-years of vital registration data, 429 surveys reporting complete birth histories, and 977 surveys and censuses reporting summary birth histories. We estimated age-specific fertility rates (ASFRs; the annual number of livebirths to women of a specified age group per 1000 women in that age group) by use of spatiotemporal Gaussian process regression and used the ASFRs to estimate total fertility rates (TFRs; the average number of children a woman would bear if she survived through the end of the reproductive age span [age 10–54 years] and experienced at each age a particular set of ASFRs observed in the year of interest). Because of sparse data, fertility at ages 10–14 years and 50–54 years was estimated from data on fertility in women aged 15–19 years and 45–49 years, through use of linear regression. Age-specific mortality data came from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2017 estimates. Data on population came from 1257 censuses and 761 population registry location-years and were adjusted for underenumeration and age misreporting with standard demographic methods. Migration was estimated with the GBD Bayesian demographic balancing model, after incorporating information about refugee migration into the model prior. Final population estimates used the cohort-component method of population projection, with inputs of fertility, mortality, and migration data. Population uncertainty was estimated by use of out-of-sample predictive validity testing. With these data, we estimated the trends in population by age and sex and in fertility by age between 1950 and 2017 in 195 countries and territories. Findings: From 1950 to 2017, TFRs decreased by 49·4% (95% uncertainty interval [UI] 46·4–52·0). The TFR decreased from 4·7 livebirths (4·5–4·9) to 2·4 livebirths (2·2–2·5), and the ASFR of mothers aged 10–19 years decreased from 37 livebirths (34–40) to 22 livebirths (19–24) per 1000 women. Despite reductions in the TFR, the global population has been increasing by an average of 83·8 million people per year since 1985. The global population increased by 197·2% (193·3–200·8) since 1950, from 2·6 billion (2·5–2·6) to 7·6 billion (7·4–7·9) people in 2017; much of this increase was in the proportion of the global population in south Asia and sub-Saharan Africa. The global annual rate of population growth increased between 1950 and 1964, when it peaked at 2·0%; this rate then remained nearly constant until 1970 and then decreased to 1·1% in 2017. Population growth rates in the southeast Asia, east Asia, and Oceania GBD super-region decreased from 2·5% in 1963 to 0·7% in 2017, whereas in sub-Saharan Africa, population growth rates were almost at the highest reported levels ever in 2017, when they were at 2·7%. The global average age increased from 26·6 years in 1950 to 32·1 years in 2017, and the proportion of the population that is of working age (age 15–64 years) increased from 59·9% to 65·3%. At the national level, the TFR decreased in all countries and territories between 1950 and 2017; in 2017, TFRs ranged from a low of 1·0 livebirths (95% UI 0·9–1·2) in Cyprus to a high of 7·1 livebirths (6·8–7·4) in Niger. The TFR under age 25 years (TFU25; number of livebirths expected by age 25 years for a hypothetical woman who survived the age group and was exposed to current ASFRs) in 2017 ranged from 0·08 livebirths (0·07–0·09) in South Korea to 2·4 livebirths (2·2–2·6) in Niger, and the TFR over age 30 years (TFO30; number of livebirths expected for a hypothetical woman ageing from 30 to 54 years who survived the age group and was exposed to current ASFRs) ranged from a low of 0·3 livebirths (0·3–0·4) in Puerto Rico to a high of 3·1 livebirths (3·0–3·2) in Niger. TFO30 was higher than TFU25 in 145 countries and territories in 2017. 33 countries had a negative population growth rate from 2010 to 2017, most of which were located in central, eastern, and western Europe, whereas population growth rates of more than 2·0% were seen in 33 of 46 countries in sub-Saharan Africa. In 2017, less than 65% of the national population was of working age in 12 of 34 high-income countries, and less than 50% of the national population was of working age in Mali, Chad, and Niger. Interpretation: Population trends create demographic dividends and headwinds (ie, economic benefits and detriments) that affect national economies and determine national planning needs. Although TFRs are decreasing, the global population continues to grow as mortality declines, with diverse patterns at the national level and across age groups. To our knowledge, this is the first study to provide transparent and replicable estimates of population and fertility, which can be used to inform decision making and to monitor progress. Funding: Bill & Melinda Gates Foundation.
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3.
  • Stanaway, Jeffrey D., et al. (författare)
  • Global, regional, and national comparative risk assessment of 84 behavioural, environmental and occupational, and metabolic risks or clusters of risks for 195 countries and territories, 1990-2017: A systematic analysis for the Global Burden of Disease Study 2017
  • 2018
  • Ingår i: The Lancet. - 1474-547X .- 0140-6736. ; 392:10159, s. 1923-1994
  • Tidskriftsartikel (refereegranskat)abstract
    • Background The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2017 comparative risk assessment (CRA) is a comprehensive approach to risk factor quantification that offers a useful tool for synthesising evidence on risks and risk-outcome associations. With each annual GBD study, we update the GBD CRA to incorporate improved methods, new risks and risk-outcome pairs, and new data on risk exposure levels and risk- outcome associations. Methods We used the CRA framework developed for previous iterations of GBD to estimate levels and trends in exposure, attributable deaths, and attributable disability-adjusted life-years (DALYs), by age group, sex, year, and location for 84 behavioural, environmental and occupational, and metabolic risks or groups of risks from 1990 to 2017. This study included 476 risk-outcome pairs that met the GBD study criteria for convincing or probable evidence of causation. We extracted relative risk and exposure estimates from 46 749 randomised controlled trials, cohort studies, household surveys, census data, satellite data, and other sources. We used statistical models to pool data, adjust for bias, and incorporate covariates. Using the counterfactual scenario of theoretical minimum risk exposure level (TMREL), we estimated the portion of deaths and DALYs that could be attributed to a given risk. We explored the relationship between development and risk exposure by modelling the relationship between the Socio-demographic Index (SDI) and risk-weighted exposure prevalence and estimated expected levels of exposure and risk-attributable burden by SDI. Finally, we explored temporal changes in risk-attributable DALYs by decomposing those changes into six main component drivers of change as follows: (1) population growth; (2) changes in population age structures; (3) changes in exposure to environmental and occupational risks; (4) changes in exposure to behavioural risks; (5) changes in exposure to metabolic risks; and (6) changes due to all other factors, approximated as the risk-deleted death and DALY rates, where the risk-deleted rate is the rate that would be observed had we reduced the exposure levels to the TMREL for all risk factors included in GBD 2017.
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6.
  • Feigin, Valery L., et al. (författare)
  • Global, regional, and national burden of neurological disorders, 1990–2016 : a systematic analysis for the Global Burden of Disease Study 2016
  • 2019
  • Ingår i: Lancet Neurology. - : Elsevier. - 1474-4422 .- 1474-4465. ; 18:5, s. 459-480
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Neurological disorders are increasingly recognised as major causes of death and disability worldwide. The aim of this analysis from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2016 is to provide the most comprehensive and up-to-date estimates of the global, regional, and national burden from neurological disorders.Methods: We estimated prevalence, incidence, deaths, and disability-adjusted life-years (DALYs; the sum of years of life lost [YLLs] and years lived with disability [YLDs]) by age and sex for 15 neurological disorder categories (tetanus, meningitis, encephalitis, stroke, brain and other CNS cancers, traumatic brain injury, spinal cord injury, Alzheimer's disease and other dementias, Parkinson's disease, multiple sclerosis, motor neuron diseases, idiopathic epilepsy, migraine, tension-type headache, and a residual category for other less common neurological disorders) in 195 countries from 1990 to 2016. DisMod-MR 2.1, a Bayesian meta-regression tool, was the main method of estimation of prevalence and incidence, and the Cause of Death Ensemble model (CODEm) was used for mortality estimation. We quantified the contribution of 84 risks and combinations of risk to the disease estimates for the 15 neurological disorder categories using the GBD comparative risk assessment approach.Findings: Globally, in 2016, neurological disorders were the leading cause of DALYs (276 million [95% UI 247–308]) and second leading cause of deaths (9·0 million [8·8–9·4]). The absolute number of deaths and DALYs from all neurological disorders combined increased (deaths by 39% [34–44] and DALYs by 15% [9–21]) whereas their age-standardised rates decreased (deaths by 28% [26–30] and DALYs by 27% [24–31]) between 1990 and 2016. The only neurological disorders that had a decrease in rates and absolute numbers of deaths and DALYs were tetanus, meningitis, and encephalitis. The four largest contributors of neurological DALYs were stroke (42·2% [38·6–46·1]), migraine (16·3% [11·7–20·8]), Alzheimer's and other dementias (10·4% [9·0–12·1]), and meningitis (7·9% [6·6–10·4]). For the combined neurological disorders, age-standardised DALY rates were significantly higher in males than in females (male-to-female ratio 1·12 [1·05–1·20]), but migraine, multiple sclerosis, and tension-type headache were more common and caused more burden in females, with male-to-female ratios of less than 0·7. The 84 risks quantified in GBD explain less than 10% of neurological disorder DALY burdens, except stroke, for which 88·8% (86·5–90·9) of DALYs are attributable to risk factors, and to a lesser extent Alzheimer's disease and other dementias (22·3% [11·8–35·1] of DALYs are risk attributable) and idiopathic epilepsy (14·1% [10·8–17·5] of DALYs are risk attributable).Interpretation: Globally, the burden of neurological disorders, as measured by the absolute number of DALYs, continues to increase. As populations are growing and ageing, and the prevalence of major disabling neurological disorders steeply increases with age, governments will face increasing demand for treatment, rehabilitation, and support services for neurological disorders. The scarcity of established modifiable risks for most of the neurological burden demonstrates that new knowledge is required to develop effective prevention and treatment strategies.Funding: Bill & Melinda Gates Foundation.
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8.
  • Akbari, Saeed, et al. (författare)
  • Large-Scale Robot-Based Polymer and Composite Additive Manufacturing : Failure Modes and Thermal Simulation
  • 2022
  • Ingår i: Polymers. - : MDPI. - 2073-4360. ; 14:9
  • Tidskriftsartikel (refereegranskat)abstract
    • Additive manufacturing (AM) of large-scale polymer and composite parts using robotic arms integrated with extruders has received significant attention in recent years. Despite the contributions of great technical progress and material development towards optimizing this manufacturing method, different failure modes observed in the final printed products have hindered its application in producing large engineering structures used in aerospace and automotive industries. We report failure modes in a variety of printed polymer and composite parts, including fuel tanks and car bumpers. Delamination and warpage observed in these parts originate mostly from thermal gradients and residual stresses accumulated during material deposition and cooling. Because printing large structures requires expensive resources, process simulation to recognize the possible failure modes can significantly lower the manufacturing cost. In this regard, accurate prediction of temperature distribution using thermal simulations is the first step. Finite element analysis (FEA) was used for process simulation of large-scale robotic AM. The important steps of the simulation are presented, and the challenges related to the modeling are recognized and discussed in detail. The numerical results showed reasonable agreement with the temperature data measured by an infrared camera. While in small-scale extrusion AM, the cooling time to the glassy state is less than 1 s, in large-scale AM, the cooling time is around two orders of magnitudes longer. © 2022 by the authors
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9.
  • Alishah, Rasoul Shalchi, et al. (författare)
  • Analysis and Design of a New Extendable Sepic Converter with High Voltage Gain and Reduced Components for Photovoltaic Applications
  • 2019
  • Ingår i: 2019 10th International Power Electronics, Drive Systems and Technologies Conference (PEDSTC). - : IEEE. - 9781538692547 ; , s. 492-497
  • Konferensbidrag (refereegranskat)abstract
    • This paper presents a high step-up DC-DC converter which is appropriate for Photovoltaic systems. This topology has been combined from an extended switched-capacitor and a common SEPIC converter. Low components and high-voltage-gain are the main benefits of the introduced topology. Low rate current ripple, easy control and continuous input current are other advantages of the presented structure. Integrating the switched-capacitor with the SEPIC converter leads to increase the output voltage with variable conversion ratio which can be used for a wide range of loads. The switched-capacitor converter provides a constant dc output voltage while the SEPIC converter extracts maximum power of PV panels because it operates under control of duty cycle. Continuous input current is highly suitable for PV applications. The operating principles and steady-state analysis of the suggested topology are discussed in detail. In order to assess the effectiveness of the presented topology, it has been simulated on PSCAD/EMTDC software.
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10.
  • Ataei, Mohammad A., et al. (författare)
  • Fuzzy analytical hierarchy process approach for ranking the sawability of carbonate rock
  • 2012
  • Ingår i: International Journal of Rock Mechanics And Mining Sciences. - : Elsevier BV. - 1365-1609 .- 1873-4545. ; 50, s. 83-93
  • Tidskriftsartikel (refereegranskat)abstract
    • A new classification system is presented to evaluate and ranking the sawability of carbonate rock. The sawability of carbonate rock is classified into five categories: excellent, good, fair, poor and very poor. The sawability is assumed to depend on the uniaxial compressive strength, Young's modulus, Mohs hardness, and a new abrasivity index. The FAHP approach is used to determine the weights of the above-mentioned parameters by decision makers. Moreover, in this paper, a new classification system was developed to modify Schimazek's F-abrasiveness factor. In this new abrasivity classification, each parameter has a different importance coefficient. The new abrasivity index of carbonate rocks can be obtained from this new abrasivity classification system. The calculated sawability index of developed classification is applied for Iranian carbonate rocks to evaluation the energy consumption in rock sawing process. A variety of two groups of carbonate rocks (seven types) were saw using a fully instrumented laboratory sawing rig at different feed rates, peripheral speeds, and depth of cut. Then, a new statistical model was obtained using multiple regression method based on operating parameters and rock sawability index
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11.
  • Baudoin, Eric, et al. (författare)
  • Effect of partial premixing on stabilization and local extinction of turbulent methane/air flames
  • 2013
  • Ingår i: Flow, Turbulence and Combustion. - : Springer Science and Business Media LLC. - 1573-1987 .- 1386-6184. ; 90:2, s. 269-284
  • Tidskriftsartikel (refereegranskat)abstract
    • Abstract in UndeterminedThe stabilization characteristics and local extinction structures of partially premixed methane/air flames were studied using simultaneous OH-PLIF/PIV techniques, and large eddy simulations employing a two-scalar flamelet model. Partial premixing was made in a mixing chamber comprised of two concentric tubes, where the degree of partial premixing of fuel and air was controlled by varying the mixing length of the chamber. At the exit of the mixing chamber a cone was mounted to stabilize the flames at high turbulence intensities. The stability regime of flames was determined for different degree of partial premixing and Reynolds numbers. It was found that in general partially premixed flames at low Reynolds numbers become more stable when the level of partial premixing of air to the fuel stream decreases. At high Reynolds numbers, for the presently studied burner configuration there is an optimal partial premixing level of air to the fuel stream at which the flame is most stable. OH-PLIF images revealed that for the stable flames not very close to the blowout regime, significant local extinction holes appear already. By increasing premixing air to fuel stream successively, local extinction holes grow in size leading to eventual flame blowout. Local flame extinction was found to frequently attain to locations where locally high velocity flows impinging to the flame. The local flame extinction poses a future challenge for model simulations and the present flames provide a possible test case for such study.
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12.
  • Baudoin, Eric, et al. (författare)
  • Effect of partial premixing on stabilization and local extinction of turbulent methane/air flames
  • 2011
  • Ingår i: Proceedings of the 17th Mediterranean Combustion symposium, MCS 7. - 9788888104126
  • Konferensbidrag (refereegranskat)abstract
    • The stabilization characteristics and local extinction structures of partially premixed methane/air flames were studied using simultaneous OH-PLIF/PIV techniques, and large eddy simulations employing a two-scalar flamelet model. Partial premixing was made in a mixing chamber comprised of two concentric tubes, where the degree of partial premixing of fuel and air was controlled by varying the mixing length of the chamber. At the exit of the mixing chamber a cone was mounted to stabilize the flames at high turbulence intensities. The stability regime of flames was determined for different degree of partial premixing and Reynolds numbers. It was found that in general partially premixed flames at low Reynolds numbers become more stable when the level of partial premixing of air to the fuel stream decreases. At high Reynolds numbers, for the presently studied burner configuration there is an optimal partial premixing level of air to the fuel stream at which the flame is most stable. OH-PLIF images revealed that for the stable flames not very close to the blowout regime,significant local extinction holes appear already. By increasing premixing air to fuel stream successively, local extinction holes grow in size leading to eventual flame blowout. Local flame extinction was found to frequently attain to locations where locally high velocity flows impinging to the flame. The local flame extinction poses a future challenge for model simulations and the present flames provide a possible test case for such study.
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13.
  • Boostani, Sareh, et al. (författare)
  • Development and characterization of medium and high internal phase novel multiple Pickering emulsions stabilized by hordein nanoparticles
  • 2022
  • Ingår i: Food Chemistry. - : Elsevier BV. - 0308-8146. ; 372
  • Tidskriftsartikel (refereegranskat)abstract
    • Medium and high internal phase W1/O/W2 multiple Pickering emulsions (MPEs) were fabricated by physically-modified hordein nanoparticles. A triphasic system was developed at dispersed phase volume fraction (Φ) of 0.5 with an overrun value of ∼40%. No overrun was detected in high internal phase MPEs (Φ 0.8). Optical and confocal laser scanning microscopy confirmed the formation of MPEs. Monomodal droplet size distribution with a mean diameter of 32.90 and 21.48 μm was observed for MPEs at Φ 0.5 and Φ 0.8, respectively. Static multiple light scattering confirmed that creaming was the main mechanism behind the instability of MPEs. Both MPEs revealed pseudo-plastic behavior and predominant storage modulus (G′) over the applied frequency range. The encapsulation efficiency of vitamin B12 in MPEs was 98.3% and remained relatively constant during 28 d. These results suggested the excellent potential of hordein nanoparticles as appropriate candidate for designing multi-structural colloidal systems using plant proteins.
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14.
  • Boostani, Sareh, et al. (författare)
  • The influence of emulsion parameters on physical stability and rheological properties of Pickering emulsions stabilized by hordein nanoparticles
  • 2020
  • Ingår i: Food Hydrocolloids. - : Elsevier BV. - 0268-005X. ; 101
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, the effect of pH (3–8), ionic strength (I, 0.01–1 M), protein particle concentration (C, 0.5%–2%), and dispersed phase volume fraction (Φ, 0.25–0.8) on the efficacy of hordein-based colloidal nanoparticles in the stabilization of Pickering structures was investigated. Colloidal particles were synthesized via anti-solvent method. Depending on pH and I, the average size and zeta-potential of hordein particles ranged from 425 to around 4000 nm, and +27.5 to −15.63 mV, respectively. The intense aggregation of particles at pH close to isoelectric point and also at high I led to poor formation and stability of Pickering emulsions. The overrun value was influenced by various emulsion parameters. At pH 3, triphasic (with the overrun value of 75%) and high internal phase (HIP) emulsions with an average droplet size of 15.6–86.7 μm were formed at Φ 0.25 and 0.8, respectively. At Φ 0.5 and 0.8, an elastic gel-like behavior (i.e., storage modulus (G′) > loss modulus (G″)) was observed over the applied frequency range. At Φ 0.25, a predominant viscous character (G">G′) was observed at low frequencies; while, at higher frequencies, G′ exceeded G″ due to the foam collapse. The morphology was studied by optical microscopy and confocal laser scanning microscopy (CLSM). Monitoring the physical stability using static multiple light scattering (MLS) revealed three destabilization profiles of foam-like, emulsion-foam and gel-like structures. The results of this study might help in designing triphasic Pickering systems (using plant-based proteins) and developing solid-like structured vegetable oils from the gel-like HIP emulsions.
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15.
  • Claesson, Åsa, et al. (författare)
  • lntegrated Optical Fiber Sensors in Additive Manufactured Metal Components for Smart Manufacturing Applications
  • 2019
  • Ingår i: Smart Systems Integration; 13th International Conference and Exhibition on Integration Issues of Miniaturized Systems.
  • Konferensbidrag (refereegranskat)abstract
    • This work combines fiber optic sensors with additive manufacturing to enable integration of temperature and strain sensors in metal components. In this paper, we present a fiber optic sensor network integrated in press hardening tools to monitor the contact between the tool and the metal sheet during forming operation. The tools are manufactured through metal powder bed fusion using laser melting processes (PBF-SLM), after which the tools are prepared for sensor integration. A demonstrator press hardening tool with integrated fiber optic sensors was heated using an electric heat foil and the sensor measurements was compared to a thermal simulation model. The sensor technology is based on Fiber Bragg Gratings (FBGs), integrated at several positions along the optical fiber. FBGs are in-fiber sensors that are multiplexed. lt is possible to place hundreds of FBG sensors along one single fiber, thus allowing for quasidistributed sensing of temperature or strain. The optical fiber itself can be less than 100 micrometer in diameter, allowing for sensing at several points in a minimally invasive way, when integrated in a tool or component.
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16.
  • Fahlkrans, Johan, 1980-, et al. (författare)
  • Influence of tempering on contact fatigue
  • 2011
  • Ingår i: International Journal of Microstructure and Materials Properties. - 1741-8410 .- 1741-8429. ; 6:6, s. 465-478
  • Tidskriftsartikel (refereegranskat)abstract
    • Most components are tempered after heat treatment operations such as case hardening or induction hardening. The common opinion is that the martensitic structure after heat treatment is too brittle and tempering is necessary to increase toughness.Tempering is an additional operation which leads to increased costs by energy, handling, and investments. Eliminating tempering from the heat treatment process leads to increased productivity, energy savings, and lowered environmental impact.Two carburised steels, Ovako 253A (?EN 22NiCrMo12-5F mod. A) and EN 20NiCrMo2 (SAE 8620, SS2506), were tested for contact fatigue resistance in a roller to roller rig. The tested samples were characterised with respect to amount of fatigue damage, residual stress, amount of retained austenite and hardness. The objective was to determine if tempering is always necessary after a heat treatment operation.The contact fatigue tests show that tempering results in lower contact fatigue resistance. Further, fatigue cracks were found to have initiated in different ways between tempered and untempered steel.
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17.
  • Feás, Xesús, et al. (författare)
  • Application of dummy molecularly imprinted solid-phase extraction in the analysis of cyproheptadine in bovine urine.
  • 2009
  • Ingår i: Journal of Separation Science. - : Wiley. - 1615-9314 .- 1615-9306. ; 32:10, s. 1740-1747
  • Tidskriftsartikel (refereegranskat)abstract
    • Due to the difficulty of monitoring trace levels of cyproheptadine (CYP) residues in complicated biological matrices, specific adsorption materials for the preconcentration and clean-up of CYP are indispensable. In this work, CYP was extracted from urine using dummy molecularly imprinted SPE (DMISPE) to avoid leakage of the imprinting molecules during the desorption phase. For synthesis of DMISPE, azatadine (AZA) was employed as the dummy template, methacrylic acid (MAA) as the monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linker, 2,2'-azobis(2-methylpropionitrile) (AIBN) as the initiator, and dichloromethane as the porogen solvent. An LC-MS/MS method was used to analyze CYP. Two MRM (multiple reaction monitoring) transitions for each analyte were monitored using diphenylpyraline hydrochloride (DPP.HCl), which was used as an internal standard. The advantages of DMISPE include obtaining less complex chromatograms and reducing ion suppression in ESI. The process efficiencies for DMISPE and SPE were 80% and 12%, respectively. In addition, the demonstrated reusability of the DMISPE cartridges is an advantage compared with single-use SPE cartridges or immunoaffinity materials.
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18.
  • Feás, Xesús, et al. (författare)
  • Development and validation of LC-MS/MS method for the determination of cyproheptadine in several pharmaceutical syrup formulations.
  • 2009
  • Ingår i: Journal of Pharmaceutical and Biomedical Analysis. - : Elsevier BV. - 0731-7085. ; 50, s. 1044-1049
  • Tidskriftsartikel (refereegranskat)abstract
    • A rapid and sensitive liquid chromatographic-tandem mass spectrometric (LC-MS/MS) method was developed and validated for the qualitative and quantitative assay of cyproheptadine (CP) in pharmaceutical samples. Diphenylpyraline hydrochloride (DPP) was used as an internal standard (IS). Two multiple reaction-monitoring (MRM) transitions for each analyte were observed: 288.1/96.1 and 288.1/191.2 for CP and 282.1/167.2 and 282.1/116.3 for DPP. The retention time of the drug was 7.29min. The analytical method was successfully validated for linearity (1-100ng/ml), intra-day precision, inter-day precision, and accuracy. The limit of detection (LOD) and limit of quantification (LOQ) were 0.86 and 0.98ng/ml, respectively. The proposed method was applied to analyse the cyproheptadine content from seven different syrup formulations.
  •  
19.
  • Feas, Xesus, et al. (författare)
  • Molecularly imprinted polyallylamine hydrogels: another reassessment
  • 2010
  • Ingår i: Polymer International. - : Wiley. - 0959-8103. ; 59:1, s. 11-15
  • Tidskriftsartikel (refereegranskat)abstract
    • Researchers in the scientific community actively discuss the fact that polymer hydrogels synthesized by crosslinking polly(allylamine hydrochloride) (PAH) with epichlorohydrin (EPI) in the presence of D-glucose-6-phosphate monobarium salt do not show or show imprinting on the molecular level. In the work reported here, a polymer hydrogel was synthesized in the presence of flumequine (FQ) by crosslinking PAH with EPI in an aqueous system. The extent of FQ binding was assessed using liquid chromatography coupled with laser-induced fluorescence detection. A hydrogel-imprinting system was found to display FQ selectivity in binding assays (75.1 and 41.9%) compared with hydrogel formed in the absence of a template (41.6 and 20.4%). High-magnification scanning electron microscopy (SEM) images show that both of the hydrogels are highly ordered, exhibiting a 'honeycomb' pattern distribution. For the effect of the template molecule in the polymer structure (i.e. the imprinting effect in hydrogel morphology), appreciable differences were observed for images obtained. The non-imprinted polymer had a uniform, smoothly shaped surface. By contrast, the hydrogel molecular imprinting polymer surface was more globular. This difference was likely caused by the structure of the target molecule. Binding experiment results correlate with surface morphology, as analysed using SEM, and indicate that imprinted hydrogels have recognizable cavities with an affinity for used FQ from the imprint. (C) 2009 Society of Chemical Industry
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20.
  • Flys, Olena, et al. (författare)
  • Heat transfer and flow performance in additively manufactured cooling channels with varying surface topography
  • 2020
  • Ingår i: Seimitsu Kogaku Kaishi/Journal of the Japan Society for Precision Engineering. - : Japan Society for Precision Engineering. - 0912-0289 .- 1882-675X. ; 86:1, s. 71-79
  • Tidskriftsartikel (refereegranskat)abstract
    • The flexibility in respect of design and manufacturing freedom that additive manufacturing (AM) offer are key driving factors for many industrial scctors. For example, designing and manufacturing unique internal conformal cooling/heating channels with enhanced functionalities for various applications like tools and heat cxchangcrs. However, for the majority of the metal AM-processes in the as-build condition, AM is associated with high surface roughness, which has a measurable impact e.g on the heat transfer and flow properties. Hence, proper characterization of the fluid flow and heat transfer is vital to understand how the AM surfaces should be optimized for maximum output. The current study considers the cffcct of surface roughness and channels dimensions on the pressure drop and heat transfer. An experimental investigation was made of cooling channels produced by Powdcr-Bcd-Fusion using Lascr-Bcam-Mclting (PBF-LBM) additive manufacturing technique. Cooling channels with as-build surfaces was compared to post-processed cooling channels such as extrude honing and drilled channels, respectively. Results showed the lowest pressure drop for extrude honed channels compare to drilled and as-build channels, while heat transfer showed the same trend for as-build and extrude honed channels. The complexity of surface topography of as-build channels need to be described by parameters suitable for the detection of fluid interaction. Combination of different parameters remains to be investigated.
  •  
21.
  • Ghajarnia, Navid, et al. (författare)
  • Evaluating the Evolution of ECMWF Precipitation Products Using Observational Data for Iran : From ERA40 to ERA5
  • 2022
  • Ingår i: Earth and Space Science. - : American Geophysical Union (AGU). - 2333-5084. ; 9:10
  • Tidskriftsartikel (refereegranskat)abstract
    • European Center for Medium-Range Weather Forecasts Reanalysis (ERA), one of the most widely used precipitation products, has evolved from ERA-40 to ERA-20CM, ERA-20C, ERA-Interim, and ERA5. Studies evaluating the performance of individual ERA products cannot adequately assess the evolution of the products. We compared the performance of all ERA precipitation products at daily, monthly, and annual data (1980-2018) using more than 2100 Iran precipitation gauges. Results indicated that ERA-40 performed worst, followed by ERA-20CM, which showed only minor improvements over ERA-40. ERA-20C considerably outperformed its predecessors, benefiting from the assimilation of observational data. Although several previous studies have reported full superiority of ERA5 over ERA-Interim, our results revealed several shortcomings in ERA5 compared with the ERA-Interim estimates. Both ERA-Interim and ERA5 performed best overall, with ERA-Interim showing better statistical and categorical skill scores, and ERA5 performing better in estimating extreme precipitations. These results suggest that the accuracy of ERA precipitation products has improved from ERA-40 to ERA-Interim, but not consistently from ERA-Interim to ERA5. This study employed a grid-grid comparison approach by first creating a gridded reference data set through the spatial aggregation of point source observations, however, the results from a point-grid approach showed no change in the overall ranking of products (despite the slight changes in the error index values). These findings are useful for model development at a global scale and for hydrological applications in Iran.
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22.
  • Griswold, Max G., et al. (författare)
  • Alcohol use and burden for 195 countries and territories, 1990-2016 : a systematic analysis for the Global Burden of Disease Study 2016
  • 2018
  • Ingår i: The Lancet. - : Elsevier. - 0140-6736 .- 1474-547X. ; 392:10152, s. 1015-1035
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Alcohol use is a leading risk factor for death and disability, but its overall association with health remains complex given the possible protective effects of moderate alcohol consumption on some conditions. With our comprehensive approach to health accounting within the Global Burden of Diseases, Injuries, and Risk Factors Study 2016, we generated improved estimates of alcohol use and alcohol-attributable deaths and disability-adjusted life-years (DALYs) for 195 locations from 1990 to 2016, for both sexes and for 5-year age groups between the ages of 15 years and 95 years and older.Methods: Using 694 data sources of individual and population-level alcohol consumption, along with 592 prospective and retrospective studies on the risk of alcohol use, we produced estimates of the prevalence of current drinking, abstention, the distribution of alcohol consumption among current drinkers in standard drinks daily (defined as 10 g of pure ethyl alcohol), and alcohol-attributable deaths and DALYs. We made several methodological improvements compared with previous estimates: first, we adjusted alcohol sales estimates to take into account tourist and unrecorded consumption; second, we did a new meta-analysis of relative risks for 23 health outcomes associated with alcohol use; and third, we developed a new method to quantify the level of alcohol consumption that minimises the overall risk to individual health.Findings: Globally, alcohol use was the seventh leading risk factor for both deaths and DALYs in 2016, accounting for 2.2% (95% uncertainty interval [UI] 1.5-3.0) of age-standardised female deaths and 6.8% (5.8-8.0) of age-standardised male deaths. Among the population aged 15-49 years, alcohol use was the leading risk factor globally in 2016, with 3.8% (95% UI 3.2-4-3) of female deaths and 12.2% (10.8-13-6) of male deaths attributable to alcohol use. For the population aged 15-49 years, female attributable DALYs were 2.3% (95% UI 2.0-2.6) and male attributable DALYs were 8.9% (7.8-9.9). The three leading causes of attributable deaths in this age group were tuberculosis (1.4% [95% UI 1. 0-1. 7] of total deaths), road injuries (1.2% [0.7-1.9]), and self-harm (1.1% [0.6-1.5]). For populations aged 50 years and older, cancers accounted for a large proportion of total alcohol-attributable deaths in 2016, constituting 27.1% (95% UI 21.2-33.3) of total alcohol-attributable female deaths and 18.9% (15.3-22.6) of male deaths. The level of alcohol consumption that minimised harm across health outcomes was zero (95% UI 0.0-0.8) standard drinks per week.Interpretation: Alcohol use is a leading risk factor for global disease burden and causes substantial health loss. We found that the risk of all-cause mortality, and of cancers specifically, rises with increasing levels of consumption, and the level of consumption that minimises health loss is zero. These results suggest that alcohol control policies might need to be revised worldwide, refocusing on efforts to lower overall population-level consumption.
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23.
  • Götelid, Sareh, et al. (författare)
  • Effect of post-processing on microstructure and mechanical properties of Alloy 718 fabricated using powder bed fusion additive manufacturing processes
  • 2021
  • Ingår i: Rapid prototyping journal. - : Emerald Group Holdings Ltd.. - 1355-2546 .- 1758-7670. ; 27:9, s. 1617-1632
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose: This study aims to investigate additive manufacturing of nickel-based superalloy IN718 made by powder bed fusion processes: powder bed fusion laser beam (PBF-LB) and powder bed fusion electron beam (PBF-EB). Design/methodology/approach: This work has focused on the influence of building methods and post-fabrication processes on the final part properties, including microstructure, surface quality, residual stresses and mechanical properties. Findings: PBF-LB produced a much smoother surface. Blasting and shot peening (SP) reduced the roughness even more but did not affect the PBF-EB surface finish as much. As-printed PBF-EB parts have low residual stresses in all directions, whereas it was much higher for PBF-LB. However, heat treatment removed the stresses and SP created compressive stresses for samples from both PBF processes. The standard Arcam process parameter for PBF-EB for IN718 is not fully optimized, which leads to porosity and inferior mechanical properties. However, impact toughness after hot isostatic pressing was surprisingly high. Originality/value: The two processes gave different results and also responses to post-treatments, which could be of advantage or disadvantage for different applications. Suggestions for improving the properties of parts produced by each method are presented.
  •  
24.
  • Hanifi, Ardeshir, Docent, 1963-, et al. (författare)
  • Effects of freestream turbulence on crossflow instabiltiy
  • 2015
  • Ingår i: Proceedings - 15th European Turbulence Conference, ETC 2015. - : TU Delft.
  • Konferensbidrag (refereegranskat)abstract
    • Direct numerical simulations (DNS) have been performed in order to investigate the interaction of freestream turbulence and crossflow generated instability on a swept wing. The experiments by [3] and [1] are selected as the reference cases. In those experiments the authors explore the interaction between different freestream turbulence characteristics and different roughness element characteristics. In the current study, isotropic homogenous freestream turbulence are generated following experimental parameters and then fed as the inflow boundary condition for DNS of flow over the wing. A spanwise array of roughness elements corresponding to the most unstable stationary modes are used to generate the crossflow vortices. The effects of the freestream turbulence on the crossflow instability and transition to turbulence are later studied. 
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25.
  • Haupt, J. Philip, et al. (författare)
  • Optimizing Jastrow factors for the transcorrelated method
  • 2023
  • Ingår i: Journal of Chemical Physics. - 1089-7690 .- 0021-9606. ; 158:22
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate the optimization of flexible tailored real-space Jastrow factors for use in the transcorrelated (TC) method in combination with highly accurate quantum chemistry methods, such as initiator full configuration interaction quantum Monte Carlo (FCIQMC). Jastrow factors obtained by minimizing the variance of the TC reference energy are found to yield better, more consistent results than those obtained by minimizing the variational energy. We compute all-electron atomization energies for the challenging first-row molecules C2, CN, N2, and O2 and find that the TC method yields chemically accurate results using only the cc-pVTZ basis set, roughly matching the accuracy of non-TC calculations with the much larger cc-pV5Z basis set. We also investigate an approximation in which pure three-body excitations are neglected from the TC-FCIQMC dynamics, saving storage and computational costs, and show that it affects relative energies negligibly. Our results demonstrate that the combination of tailored real-space Jastrow factors with the multi-configurational TC-FCIQMC method provides a route to obtaining chemical accuracy using modest basis sets, obviating the need for basis-set extrapolation and composite techniques.
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26.
  • Holmberg, Jonas, 1976-, et al. (författare)
  • Machining of additively manufactured alloy 718 in as-built and heat-treated condition: surface integrity and cutting tool wear
  • 2024
  • Ingår i: The International Journal of Advanced Manufacturing Technology. - : Springer Nature. - 0268-3768 .- 1433-3015. ; 130:3-4, s. 1823-1842
  • Tidskriftsartikel (refereegranskat)abstract
    • Additive manufacturing (AM) using powder bed fusion is becoming a mature technology that offers great possibilities and design freedom for manufacturing of near net shape components. However, for many gas turbine and aerospace applications, machining is still required, which motivates further research on the machinability and work piece integrity of additive-manufactured superalloys. In this work, turning tests have been performed on components made with both Powder Bed Fusion for Laser Beam (PBF-LB) and Electron Beam (PBF-EB) in as-built and heat-treated conditions. The two AM processes and the respective heat-treatments have generated different microstructural features that have a great impact on both the tool wear and the work piece surface integrity. The results show that the PBF-EB components have relatively lower geometrical accuracy, a rough surface topography, a coarse microstructure with hard precipitates and low residual stresses after printing. Turning of the PBF-EB material results in high cutting tool wear, which induces moderate tensile surface stresses that are balanced by deep compressive stresses and a superficial deformed surface that is greater for the heat-treated material. In comparison, the PBF-LB components have a higher geometrical accuracy, a relatively smooth topography and a fine microstructure, but with high tensile stresses after printing. Machining of PBF-LB material resulted in higher tool wear for the heat-treated material, increase of 49%, and significantly higher tensile surface stresses followed by shallower compressive stresses below the surface compared to the PBF-EB materials, but with no superficially deformed surface. It is further observed an 87% higher tool wear for PBF-EB in as-built condition and 43% in the heat-treated condition compared to the PBF-LB material. These results show that the selection of cutting tools and cutting settings are critical, which requires the development of suitable machining parameters that are designed for the microstructure of the material.
  •  
27.
  • Holmberg, Jonas, 1976-, et al. (författare)
  • Round Robin Study on Residual Stresses Using X-Ray Diffraction for Shot-Peened Tool Steel Specimens
  • 2018
  • Ingår i: Residual Stresses 2018, Ecrs-10. - Millersville, PA, USA : MATERIALS RESEARCH FORUM LLC. - 9781945291883 ; , s. 51-56
  • Konferensbidrag (refereegranskat)abstract
    • Residual stress measurements using x-ray diffraction is a well established method used within the industrial and academic community to verify the performance of different processes for metallic materials. The measurement gives an absolute value of the stress state which can be used to design and optimize the process route to induce beneficial compressive residual stresses and avoid detrimental tensile stresses. Investigating the uncertainty and accuracy of the measurement system, operator and the material is therefore of high relevance both from an industrial and scientific point of view. Round robin testing is an important way to quantify the uncertainties that could affect the quality of the measured results and hence how a process is optimized and tuned. Such an investigation allows the operator to understand and reduce variations. Current round robin test includes results from five different laboratories using comparable equipments located in Sweden, Finland, Germany and United States. This work focuses on five shot-peened tool steel specimens produced with identical process settings. Additionally, an investigation of the repeatability of the system, influence of the operator, variations within the specimen, and the long time stability of the specimens has been measured.
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28.
  • Hosseini-Hashemi, Sh., et al. (författare)
  • Accurate free vibration analysis of thick laminated circular plates with attached rigid core
  • 2012
  • Ingår i: Journal of Sound and Vibration. - : Elsevier BV. - 0022-460X .- 1095-8568. ; 331:25, s. 5581-5596
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper deals with the free vibration behavior of laminated transversely isotropic circular plates with axisymmetric rigid core attached at the center. The governing equations of motion are obtained based on Mindlin's first-order shear deformation plate theory. Two possible categories of vibration modes related to up-down translation of the core and wobbly rotation of the core about a diameter are studied. Accurate natural frequencies hitherto not reported in the literature are presented for a wide range of thickness-to-radius ratio, inner-to-outer radius ratio, mass and moment of inertia ratios of the core and various boundary conditions at the outer edge of the plate. Numerical results are compared with those of a three-dimensional finite element method (3-D FEM) to demonstrate the high accuracy and reliability of the current analysis.
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29.
  • Hosseini-Hashemi, Sh., et al. (författare)
  • Free vibration analysis of functionally graded elliptical plates
  • 2012
  • Ingår i: International journal of Maritime Technology. - 2345-6000. ; 8:15, s. 43-60
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper deals with a free vibration analysis of functionally graded elliptical plates with different classical boundary conditions on the basis of polynomial-Ritz method and classical plate theory. The proposed admissible function is capable to obtain accurate natural frequencies of various classical boundary conditions namely, clamped, free and simply supported edges. The mechanical properties of the FG plate are assumed to vary continuously through the thickness of the plate and obey a power law distribution of the volume fraction of the constituents. The convergency of applied polynomial-Ritz method is investigated. In order to verify the accuracy of the present solution, a comprehensive comparison study is performed with the available results in the literature for homogeneous elliptical plate and FG circular plate. Also, the numerical results of the present solution for FG elliptical plate are compared with those of the finite element method (FEM). Finally, the effects of the plate geometry and inhomogeneity on the natural frequencies are investigated and some vibrational mode shapes related to symmetric-symmetric, symmetric-antisymmetric, antisymmetric- symmetric and antisymmetric- antisymmetric states are presented.
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30.
  • Hosseini, Seyed, et al. (författare)
  • A descriptive phenomenological model for white layer formation in hard turning of AISI 52100 bearing steel
  • 2021
  • Ingår i: CIRP - Journal of Manufacturing Science and Technology. - : Elsevier Ltd. - 1755-5817 .- 1878-0016. ; 32, s. 299-310
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper investigates the characteristics and the formation of white layers and dark layers induced by hard turning of through-hardened AISI 52,100 steel. The investigation showed that different types of white layers exist e.g., formed predominantly through excessive thermal or mechanical energy loading. The thermally induced white layer is formed when the cutting temperature is above the critical austenitisation temperature for the material. The nano-sized microstructure is initiated through dynamic recovery, which transitions to dynamic recrystallisation when the temperature rises above the onset temperature for dynamic recrystallisation. The corresponding white layer is characterised by a higher retained austenite content compared to the unaffected material, and the presence of a dark layer beneath the white layer. The white layer and the adjacent dark layer are found to be ∼12% harder and 14% softer, respectively, compared to the unaffected material. On the other hand, the mechanically induced white layer is formed through severe plastic deformation, where the formation is controlled by dynamic recovery and results in an elongated and broken-down substructure. Neither austenite nor an adjacent dark layer could be found for such white layers. The mechanically induced white layer is ∼26% harder than the unaffected material. For both types of white layer, (Fe, Cr)3C carbides are found in the microstructure. The investigation shows that the heating rate, cooling rate, pressure, and duration of contact between the cutting tool and workpiece surface should also be considered to understand the underlying formation mechanisms. The characteristics of the examined white layers and the cutting conditions are summarised in a descriptive phenomenological model in order to create a systematic approach for the definition of the different types of white layers. 
  •  
31.
  • Hosseini, Seyed, 1981, et al. (författare)
  • A Methodology for Temperature Correction When Using Two-Color Pyrometers : Compensation for Surface Topography and Material
  • 2014
  • Ingår i: Experimental mechanics. - : Springer Science and Business Media LLC. - 0014-4851 .- 1741-2765. ; 54:3, s. 369-377
  • Tidskriftsartikel (refereegranskat)abstract
    • In this investigation, the applicability of the two-color pyrometer technique for temperature measurements in dry hard turning of AISI 52100 steel was studied, where both machined surfaces as well as cutting tools were considered. The impacts of differing hard turned surface topography on the two-color pyrometer readings was studied by conducting temperature measurements on reference samples created using cutting tools with different degrees of tool flank wear. In order to conduct measurements in a controlled environment, a specially designed furnace was developed in which the samples were heated step-wise up to 1,000 °C in a protective atmosphere. At each testing temperature, the temperatures measured by the two-color pyrometer were compared with temperatures recorded by thermocouples. For all materials and surfaces as studied here, the two-color pyrometer generally recorded significantly lower temperatures than the thermocouples; for the hard turned surfaces, depending on the surface topography, the temperatures were as much as 20 % lower and for the CBN cutting tools, 13 % lower. To be able to use the two-color pyrometer technique for temperature measurements in hard turning of AISI 52100 steel, a linear approximation function was determined resulting in three unique equations, one for each of the studied materials and surfaces. By using the developed approximation function, the measured cutting temperatures can be adjusted to compensate for differing materials or surface topographies for comparable machining conditions. Even though the proposed equations are unique for the hard turning conditions as studied here, the proposed methodology can be applied to determine the temperature compensation required for other surface topographies, as well as other materials. © 2013 Society for Experimental Mechanics.
  •  
32.
  •  
33.
  • Hosseini, Seyed, 1981, et al. (författare)
  • Atomic-scale investigation of carbon atom migration in surface induced white layers in high-carbon medium chromium (AISI 52100) bearing steel
  • 2017
  • Ingår i: Acta Materialia. - : Elsevier BV. - 1359-6454 .- 1873-2453. ; 130, s. 155-163
  • Tidskriftsartikel (refereegranskat)abstract
    • The microstructure and chemical composition of white layers (WLs) formed during hard turning of AISI 52100 steel were studied using atom probe tomography (APT) and transmission electron microscopy (TEM). APT analyses revealed a major difference in the re-distribution of the carbon (C) atoms between WLs formed above and below the Ac1 temperature, i.e. T-WL and M-WL, respectively. In T-WL, the C-atoms segregate to grain boundaries (GBs) forming interconnected or isolated C-rich clusters, ∼5 nm, with a concentration of 9.8 ± 0.3 at.%C. Apart from the GB segregation, in M-WLs, large C-rich regions were found with 24.8 ± 0.4 at.%C. Owing to the chemical composition (stoichiometry) and element partitioning of such regions, they were assigned as θ-carbides (cementite). The APT results reveal that the original θ-carbides remain un-dissolved in the M-WLs, but might be plastically deformed due to the excessive strain that exists in hard machining process. The obtained results are in good agreement with the temperatures that are reached during formation of M-WLs. The isolated nano-sized C-clusters were assigned as off-stoichiometric carbides whereas the interconnected C-rich clusters were attributed to Cottrell atmospheres, evident by the linear shape of the C-enrichment as observed in the APT reconstructions. The C-contents in the nano-sized martensitic and ferritic grains were estimated to 0.50 ± 0.06 at.%C and ∼0.46 ± 0.02 at.%C, respectively. The C-content in the ferritic grains, beyond the C-solubility limit in ferrite (
  •  
34.
  • Hosseini, Seyed, 1981, et al. (författare)
  • Characterization of the Surface Integrity induced by Hard Turning of Bainitic and Martensitic AISI 52100 Steel
  • 2012
  • Ingår i: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 1:1, s. 494 - 499
  • Konferensbidrag (refereegranskat)abstract
    • Depending on the process parameters and the tool condition, hard turned surfaces can consist of a “white” and a “dark” etching layer having other mechanical properties compared to the bulk material. X-ray diffraction measurements revealed that tensileresidual stresses accompanied with higher volume fraction of retained austenite are present in the thermally induced white layer. While compressive residual stresses and decreased retained austenite content was found in the plastically created white layer. The surface temperature was estimated to be ~1200 C during white layer formation by hard turning.
  •  
35.
  • Hosseini, Seyed, 1981 (författare)
  • Characterization of White Layers induced by Hard Turning of AISI 52100 Steel
  • 2013
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Hard turning is a machining process applied to metallic materials with hardness above 45 HRC. The process offers high production flexibility and sustainable manufacturing since it allows performing both rough and finishing machining of complex geometries in one single setup. With respect to surface integrity, hard turning can generate beneficial compressive residual stresses and good surface quality with small dimensional variation. However, deterioration of the cutting tool generates tensile residual stresses and also alters the surface microstructure, i.e. leads to formation of white layers. Since the mechanisms for white layer formation are not yet fully understood, there is limited understanding of whether there exists different types of white layers possessing different mechanical properties. Therefore, additional processing steps are often added to remove the white layers and to generate compressive residual stresses. By hard turning at different cutting speeds, 30 m/min to 260 m/min, and different tool conditions, it was possible to generate surface integrities with and without white layers on AISI 52100 steel. After hard turning with fresh cutting tools, only discontinuous and thin white layers were detected, while in case of turning with cutting tools with excessive flank wear, white layers up to 3 μm in thickness were observed. White layers formed at 30 m/min are characterized by reduced retained austenite content, deformed M3C carbides and compressive or low tensile residual stresses. In contrast, when white layers created at higher cutting speeds e.g. 260 m/min, significantly increased retained austenite contents, un-affected M3C carbides and high tensile residual stresses were measured. Temperature measurements with a novel two-color pyrometer at the cutting edge revealed large differences in cutting temperature for the studied cutting conditions, i.e. cutting temperatures higher than 900°C were measured at a cutting speed of 260 m/min, while during machining at 30 m/min, temperatures of about 550°C were measured. Microstructural characterization by use of transmission electron microscopy showed that the white layers consist of nanocrystalline and sub-microsrystalline grains ranging from 10 to 200 nm in diameter. The results show that there are different types of white layers, which are predominantly thermally or mechanically induced. Hence, depending on the formation mechanisms, different mechanical properties can be obtained.
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36.
  • Hosseini, Seyed, et al. (författare)
  • Comparison of machining performance of stainless steel 316L produced by selective laser melting and electron beam melting
  • 2022
  • Ingår i: Procedia CIRP. - : Elsevier B.V.. - 2212-8271. ; , s. 72-77
  • Konferensbidrag (refereegranskat)abstract
    • Powder bed fusion processes based additively manufactured SS 316L components fall short of surface integrity requirements needed for optimal functional performance. Hence, machining is required to achieve dimensional accuracy and to enhance surface integrity characteristics. This research is focused on comparing the material removal performance of 316L produced by PBF-LB (laser) and PBF-EB (electron beam) in terms of tool wear and surface integrity. The results showed comparable surface topography and residual stress profiles. While the hardness profiles revealed work hardening at the surface where PBF-LB specimens being more susceptible to work hardening. The investigation also revealed differences in the progress of the tool wear when machining specimens produced with either PBF-LB or PBF-EB. .
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37.
  • Hosseini, Seyed, 1981, et al. (författare)
  • Cutting temperatures during hard turning : Measurements and effects on white layer formation in AISI 52100
  • 2014
  • Ingår i: Journal of Materials Processing Technology. - : Elsevier BV. - 0924-0136 .- 1873-4774. ; 214:6, s. 1293-1300
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper concerns the temperature evolution during white layer formation induced by hard turning of martensitic and bainitic hardened AISI 52100 steel, as well as the effects of cutting temperatures and surface cooling rates on the microstructure and properties of the induced white layers. The cutting temperatures were measured using a high speed two-colour pyrometer, equipped with an optical fibre allowing for temperature measurements at the cutting edge. Depending on the machining conditions, white layers were shown to have formed both above and well below the parent austenitic transformation temperature, Ac1, of about 750 C. Thus at least two different mechanisms, phase transformation above the Ac1 (thermally) and severe plastic deformation below the Ac1 (mechanically), have been active during white layer formation. In the case of the predominantly thermally induced white layers, the cutting temperatures were above 900 C, while for the predominantly mechanically induced white layers the cutting temperatures were approximately 550 C. The surface cooling rates during hard turning were shown to be as high as 104-105 C/s for cutting speeds between 30 and 260 m/min independent of whether the studied microstructure was martensitic or bainitic. Adding the results from the cutting temperature measurements to previous results on the retained austenite contents and residual stresses of the white layers, it can be summarised that thermally induced white layers contain significantly higher amounts of retained austenite compared to the unaffected material and display high tensile residual stresses. On the contrary, in the case of white layers formed mainly due to severe plastic deformation, no retained austenite could be measured and the surface and subsurface residual stresses were compressive. © 2014 Elsevier B.V.
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38.
  • Hosseini, Seyed, 1981, et al. (författare)
  • Determination of Stresses and Retained Austenite in Carbon Steels by X-rays - A Round Robin Study
  • 2011
  • Ingår i: Experimental Mechanics. - : Springer Science and Business Media LLC. - 1741-2765 .- 0014-4851. ; 51:1, s. 59-69
  • Tidskriftsartikel (refereegranskat)abstract
    • Residual stresses and retained austenite are twoimportant process-related parameters which need to becontrolled and monitored carefully during production andheat treatment of products. X-ray diffraction techniques arenormally used in this context, and the purpose of thepresent study was to investigate the reproducibility andaccuracy of these methods for medium and high carbonsteels. The work was carried out as a round robin studyincluding nine different laboratories in Sweden and Finland.Stress measurements were carried out on three specimens etched to three different depths, 0 μm, 230 μm and 515 μm. Retained austenite measurements were carried out on three specimens containing approximately 11, 17 and 30 vol.-% of this phase. The stress measurements showed good reproducibility with standard deviations of typically 4% on flat and smooth surfaces and not more than about 8% on etched surfaces. Estimations revealed that specimen misalignment and improper X-ray spot location were the main sources behind the variation in the stress recordings. The determination of retained austenite showed a standard deviation of typically 15% between the different contributors. However, by using identical evaluation methodsfor all raw data, the data spread could be narrowed by afactor of 3 to 4 despite the fact that different experimental settings were used in the individual laboratories.
  •  
39.
  • Hosseini, Seyed, 1981, et al. (författare)
  • Dissolution of iron-chromium carbides during white layer formation induced by hard turning of AISI 52100 steel
  • 2014
  • Ingår i: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 14, s. 107-112
  • Konferensbidrag (refereegranskat)abstract
    • The (Fe, Cr)3C carbide morphology in the surface region of hard turned bainitic AISI 52100 steel was investigated using both experimental techniques and simulations, where microstructural analysis was correlated with analytical studies of the carbide dissolution kinetics using DICTRA1. The experimental results showed that for both predominantly thermally and mechanically induced white layers no significant carbide dissolution took place down to a depth of 20 μm below the machined surfaces. This was confirmed by the analytical results from DICTRA, which showed that no significant carbide dissolution should take place during hard turning given the short contact times. Within the hard turned surfaces up to ∼12% of the carbides were elongated, indicating plastic deformation of the carbides during machining.
  •  
40.
  • Hosseini, Seyed, 1981, et al. (författare)
  • Formation mechanisms of white layers induced by hard turning of AISI 52100 steel
  • 2015
  • Ingår i: Acta Materialia. - : Elsevier BV. - 1359-6454. ; 89, s. 258-267
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper concerns the formation mechanisms of white layers (WLs) induced by machining of through-hardened (martensitic and bainitic) AISI 52100 steel. The microstructures of different types of WLs were investigated using transmission electron microscopy; those that had been predominantly mechanically induced (M-WL) and those that had been predominantly thermally induced (T-WL). Independent of the process parameters and the starting microstructure, the WLs consisted of a randomly oriented nano- and submicron-sized microstructure with an average grain size in the order of several tens of nanometres. The M-WLs were characterised as bcc-(α) ferrite and orthorhombic-(θ) cementite where the initial martensite/bainite platelets had been reoriented along the shear direction and broken-down into elongated sub-grains through dynamic recovery. The T-WLs were shown to consist of fcc-(γ) austenite, bcc-(α) martensite, and orthorhombic-(θ) cementite. Here the elongated sub-structure was found to coexist with equiaxed grains, meaning that the formation was initiated by dynamic recovery, which advanced to dynamic recrystallisation at the increased temperatures caused by the higher cutting speeds. Although times and temperatures are considered to be insufficient to dissolve the secondary carbides, carbide refinement was observed independently on the type of WL. The carbide refinement was controlled by (i) deformation and fragmentation of the carbides via dislocation movement along the {1 1 0} and {1 0 0}, (ii) precipitation of nano-sized carbides and (iii) diffusion-based carbide refinement by carbon depletion via dislocations in the nano-sized grains and grain boundaries, which act as high diffusivity paths.
  •  
41.
  • Hosseini, Seyed Hamid (författare)
  • Physicochemical studies of oxide zinc mineral flotation
  • 2008
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • At the present, zinc is produced mostly from zinc sulphide ores because the sulphides are easy to separate from the gangue and to concentrate by conventional flotation techniques but in the case of oxide zinc ores, the recovery of zinc is not enough high. The objective of the present study is to investigate the influence of different cationic, anionic and mixed collectors on the flotation of smithsonite mineral and an oxide zinc ore at various concentrations and pH values. The present thesis consists of three studies parts. First, characterization of smithsonite mineral and oxide zinc ore from the Angooran ore deposit, Iran, second, physicochemical studies on smithsonite sample include zeta- potential, contact angle, microflotation tests and adsorption studies using diffuse reflectance FTIR (DRIFT) and X-ray photoelectron spectroscopy (XPS) techniques in the presence of cationic, anionic and mixed collectors (cationic/anionic) and third, flotation behavior of oxide zinc ore from the Angooran ore in the presence of cationic, anionic and mixed collectors. According to the characterization studies of samples, the size fraction of - 125 +75 µm is selected as the liberation degree and the result of heavy liquid tests (HLS) confirms it. The results of XPS and EDX on ore samples in different size fractions showed no significant variations in zinc percentage on bulk and surface of samples. The smithsonite flotation results in the presence of dodecylamine after sulphidization using sodium sulphide show a maximum recovery (94 %) at around pH 11.5. These results are in agreement with obtained zeta-potential and contact angle measurements. Among the used anionic collectors i.e. oleic acid, hexylmercaptan, KAX alone and KAX in the presence of sodium sulphide and copper sulphate, oleic acid indicates a maximum flotation recovery (93 %) at around pH 10. Regarding the mixed collector flotation, the recovery increases with the increasing KAX concentration i.e. the flotation recovery is enhanced to 97 %. Also the recoveries and contact angles are much higher when KAX and DDA alone are used. The spectroscopic data is compared to flotation, zeta potential and contact angle results. The qualitative and quantitative evaluation of the adsorbed layer which causes the surface hydrophobicity or hydrophilicity, are performed using spectroscopic methods (FTIR and XPS). The DRIFT and XPS spectra confirm the adsorption of dodecylamine, oleic acid, hexylmercaptan, KAX and mixed collector (KAX+DDA) on the smithsonite surface. These results are in consistence with obtained zeta-potential, contact angle and also microflotation results. The studies on oxide zinc ore indicate a maximum bench scale flotation recovery of 84.5% with zinc grade 24.5% in the presence of dodecylamine at pH 11.5. There are no significant variations in recovery between cationic and anionic and mixed collectors, however, amine and mixed collector flotation are more selective than anionic collectors. The recoveries with mixed collectors show that increasing KAX, the flotation recovery enhances.
  •  
42.
  • Hosseini, Seyed Morteza, et al. (författare)
  • 6D attractors and black hole microstates
  • 2018
  • Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; :12
  • Tidskriftsartikel (refereegranskat)
  •  
43.
  • Hosseini, Seyed Mehrdad, 1977, et al. (författare)
  • Adaptive forward collision warning algorithm for automotive applications
  • 2016
  • Ingår i: American Control Conference. - 0743-1619. - 9781467386821 ; 2016-July, s. 5982-5987
  • Konferensbidrag (refereegranskat)abstract
    • This paper proposes an adaptive collision warning algorithm (CWA) that supports the driver by issuing early warnings for collision avoidance without noticeably increasing the risk of false alarms in real traffic. This algorithm can also detect when an emergency intervention is necessary. Compared to existing CWAs, the proposed solution in this paper triggers alarms by solving a linear convex program using traffic data, road’s constraints and bicycle model dynamics, and by incorporating an adaptive (speed-dependent) warning threshold. A collision threat is detected by determining feasible steering trajectories without altering the vehicle’s longitudinal velocity.
  •  
44.
  •  
45.
  • Hosseini, Seyed M., et al. (författare)
  • Direct numerical simulation of the flow around a wing section at moderate Reynolds number
  • 2016
  • Ingår i: International Journal of Heat and Fluid Flow. - : Elsevier. - 0142-727X .- 1879-2278. ; 61, s. 117-128
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • Abstract A three-dimensional direct numerical simulation has been performed to study the turbulent flow around the asymmetric NACA4412 wing section at a moderate chord Reynolds number of R e c = 400 , 000 , with an angle of attack of A o A = 5 ∘ . The mesh was optimized to properly resolve all relevant scales in the flow, and comprises around 3.2 billion grid points. The incompressible spectral-element Navier–Stokes solver Nek5000 was used to carry out the simulation. An unsteady volume force is used to trip the flow to turbulence on both sides of the wing at 10% of the chord. Full turbulence statistics are computed in addition to collection of time history data in selected regions. The Reynolds numbers on the suction side reach ReÏ„ ≃ 373 and R e Ξ = 2 , 800 with the pressure-gradient parameter ranging from β ≈ 0.0 to β ≈ 85. Similarly, on the pressure side, the Reynolds numbers reach ReÏ„ ≈ 346 and R e Ξ = 818 while β changes from β ≈ 0.0 to β ≈ − 0.25 . The effect of adverse pressure gradients on the mean flow is consistent with previous observations, namely a steeper incipient log law, a more prominent wake region and a lower friction. The turbulence kinetic energy profiles show a progressively larger inner peak for increasing pressure gradient, as well as the emergence and development of an outer peak with stronger APGs. The present simulation shows the potential of high-order (spectral) methods in simulating complex external flows at moderately high Reynolds numbers.
  •  
46.
  • Hosseini, Seyed M., et al. (författare)
  • Direct numerical simulation of the flow around a wing section at moderate Reynolds numbers
  • 2015
  • Ingår i: Proceedings - 15th European Turbulence Conference, ETC 2015. - : TU Delft.
  • Konferensbidrag (refereegranskat)abstract
    • A three dimensional direct numerical simulation has been performed to study the flow around the asymmetric NACA-4412 wing at a moderate chord Reynolds number (Rec = 400, 000) with an angle of attack of 5◦. The flow case under investigation poses numerous challenges for a numerical method due to the wide range of scales and complicated flow physics induced by the geometry. The mesh is optimized and well resolved to account for such varying scales in the flow. An unsteady volume force is used to trip the flow to turbulence on both sides of the wing at 10% chord. Full turbulent statistics are computed on the fly to further investigate the complicated flow features around the wing. The present simulation shows the potential of high-order methods in simulating complex external flows at moderately high Reynolds numbers. 
  •  
47.
  • Hosseini, Seyed Mohammad, et al. (författare)
  • Effect of Freestream Turbulence on Roughness-induced Crossflow Instability
  • 2015
  • Ingår i: Procedia IUTAM. - : Elsevier. - 2210-9838. ; , s. 303-310
  • Konferensbidrag (refereegranskat)abstract
    • The effect of freestream turbulence on generation of crossflow disturbances over swept wings is investigated through direct nu- merical simulations. The set up follows the experiments performed by Downs et al. (2012). In these experiments the authors use ASU(67)-0315 wing geometry which promotes growth of crossflow disturbances. Distributed roughness elements are locally placed near the leading edge with a given spanwise wavenumber to excite the corresponding stationary crossflow vortices. In present study, we partially reproduce the isotropic homogenous freestream turbulence through direct numerical simulations using freestream spectrum data from the experiments. The generated freestream fields are then applied as the inflow boundary condition for direct numerical simulation of the wing. The distributed roughness elements are modelled through wing surface deformation and placed near the leading edge to trigger the stationary crossflow disturbances. The effects of the generated freestream turbulence on the initial amplitudes and growth of the boundary layer perturbations are then studied.
  •  
48.
  • Hosseini, Seyed Mohammd, 1985-, et al. (författare)
  • Effect of freestream turbulence on roughness-induced crossflow instability
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • The effect of freestream turbulence on generation and breakdown of crossflow disturbances over a swept wing is investigated through direct numerical simu- lations. The setup of simulations follows the experiments performed by Downs et al. which were conducted at a very low freestream turbulence level. The stationary cross flow vortices are generated by a row of uniformly distributed roughness elements. Here, the isotropic freestream turbulence are numerically generated through separate simulations. The generated freestream fields are then added to the inflow boundary condition for simulation of flow over the swept wing. Different levels of freestream turbulence and roughness heights are considered. It was observed that low freestream turbulence level could play a major role in triggering transition of the flow dominated by stationary cross- flow vortices. Similar to the observations in the experiment, increasing the turbulence level moved the transition location further upstream. Moreover, it was found that slight increment in the height of critically spaced roughness elements had an stabilizing effect and delayed transition to turbulence. The ob- servations made in the present study may explain the counter-intuitive results of the recent flight experiment by Saric et al. (2015), where transition occurred further downstream on the wing model with painted surface compared to the model with polished surface. 
  •  
49.
  • Hosseini, Seyed M., et al. (författare)
  • Effect of freestream turbulence on roughness-induced crossflow instability
  • 2013
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • The effect of freestream turbulence on generation of crossflow disturbances over swept wings is investigated through direct numerical simulations.  The set up follows  the  experiments  performed  by Downs  et  al.  in their  TAMU  experi- ment.  In this experiment the authors use ASU(67)-0315 wing geometry which promotes  growth  of crossflow  disturbances.   Distributed  roughness  elements are locally placed near the leading edge with a span-wise wavenumber, to ex- cite the corresponding crossflow vortices.  The response of boundary layer to external disturbances such as roughness heights, span-wise wavenumbers, Rey- nolds numbers and freestream turbulence characteristics are studied.  It must be noted that the experiments were conducted at a very low level of freestream turbulence  intensity  (T u).   In this  study,  we fully  reproduce the  freestream isotropic homogenous turbulence through a DNS code using detailed freestream spectrum data provided by the experiment. The generated freestream fields are then applied as the inflow boundary condition for direct numerical simulation of the wing. The geometrical set up is the same as the experiment along with application of distributed roughness elements near the leading edge to precipi- tate stationary crossflow disturbances.  The effects of the generated freestream turbulence are then studied on the initial amplitudes and growth of the bound- ary layer perturbations.  It appears that the freestream turbulence damps out the dominant stationary crossflow vortices. 
  •  
50.
  • Hosseini, Seyed Mohammad, et al. (författare)
  • Effect of Scaling of Blade Row Sectors on the Prediction of Aerodynamic Forcing in a Highly-Loaded Transonic Turbine Stage
  • 2012
  • Ingår i: Proceedings of the ASME Turbo Expo 2011, Vol 6, Parts A And B. - New York : American Society of Mechanical Engineers. - 9780791854662 ; , s. 1297-1307
  • Konferensbidrag (refereegranskat)abstract
    • The viability of a scaling technique in prediction of forced response of the stator and rotor blades in a turbine stage has been examined. Accordingly the so called parameter, generalized force, is defined which describes the excitation of a modeshape due to the unsteady flow forces at a certain frequency. The capability of this method to accurately predict the generalized forces serves as the viability criterion. The scaling technique modifies the geometry to obtain an integer stator, rotor blade count ratio in an annulus section while maintaining steady aerodynamic similarity. A non-scaled configuration is set up to serve as the reference case. Further configurations with different scaling ratios are also generated for accuracy comparison. Unsteady forces are calculated through 3D Navier-Stokes simulations by VolSol, which is based on an explicit, time-marching. A general purpose finite element model of blades is also provided to enable modal analysis with the harmonic forces. The generalized forces of stator and rotor blades revealed high sensitivity towards modification of stator blades while acceptable accuracy was obtained by moderate modifications of the rotor blades for first harmonic forces. Moreover the influence of variable blade's structural characteristics proved to be remarkable.
  •  
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