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Статті в журналах з теми "Mass specific mass loss rates"
1
Baker, Jason D., Charles W. Fowler, and George A. Antonelis. "Mass change in fasting immature male northern fur seals." Canadian Journal of Zoology 72, no. 2 (February 1, 1994): 326–29. http://dx.doi.org/10.1139/z94-045.
Повний текст джерелаАнотація:
Immature male northern fur seals (Callorhinus ursinus) lost an estimated 20–30% of their body mass while fasting during the breeding season on St. Paul Island, Alaska. This is somewhat less than the mass loss reported for territorial adult male pinnipeds. During fasting, absolute rates of mass change (averaging −0.68 kg∙day−1) were positively correlated with initial mass. Mass-specific rate of change (averaging 2%∙day−1) did not vary with age or initial mass. Although they lose large amounts of mass while fasting, immature male fur seals achieve a net increase in mass during the breeding season by making feeding trips to sea. We postulate that the capability for prolonged fasting in immature males facilitates the development of social and sexual skills that are likely to increase future reproductive success.
2
Bani, Borruso, Matthews Nicholass, Bardelli, Polo, Pioli, Gómez-Brandón, Insam, Dumbrell, and Brusetti. "Site-Specific Microbial Decomposer Communities Do Not Imply Faster Decomposition: Results from a Litter Transplantation Experiment." Microorganisms 7, no. 9 (September 12, 2019): 349. http://dx.doi.org/10.3390/microorganisms7090349.
Повний текст джерелаАнотація:
Microbes drive leaf litter decomposition, and their communities are adapted to the local vegetation providing that litter. However, whether these local microbial communities confer a significant home-field advantage in litter decomposition remains unclear, with contrasting results being published. Here, we focus on a litter transplantation experiment from oak forests (home site) to two away sites without oak in South Tyrol (Italy). We aimed to produce an in-depth analysis of the fungal and bacterial decomposer communities using Illumina sequencing and qPCR, to understand whether local adaptation occurs and whether this was associated with litter mass loss dynamics. Temporal shifts in the decomposer community occurred, reflecting changes in litter chemistry over time. Fungal community composition was site dependent, while bacterial composition did not differ across sites. Total litter mass loss and rates of litter decomposition did not change across sites. Litter quality influenced the microbial community through the availability of different carbon sources. Additively, our results do not support the hypothesis that locally adapted microbial decomposers lead to a greater or faster mass loss. It is likely that high functional redundancy within decomposer communities regulated the decomposition, and thus greater future research attention should be given to trophic guilds rather than taxonomic composition.
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Farías-Barahona, David, Álvaro Ayala, Claudio Bravo, Sebastián Vivero, Thorsten Seehaus, Saurabh Vijay, Marius Schaefer, Franco Buglio, Gino Casassa, and Matthias H. Braun. "60 Years of Glacier Elevation and Mass Changes in the Maipo River Basin, Central Andes of Chile." Remote Sensing 12, no. 10 (May 21, 2020): 1658. http://dx.doi.org/10.3390/rs12101658.
Повний текст джерелаАнотація:
Glaciers in the central Andes of Chile are fundamental freshwater sources for ecosystems and communities. Overall, glaciers in this region have shown continuous recession and down-wasting, but long-term glacier mass balance studies providing precise estimates of these changes are scarce. Here, we present the first long-term (1955–2013/2015), region-specific glacier elevation and mass change estimates for the Maipo River Basin, from which the densely populated metropolitan region of Chile obtains most of its freshwater supply. We calculated glacier elevation and mass changes using historical topographic maps, Shuttle Radar Topography Mission (SRTM), TerraSAR-X add-on for Digital Elevation Measurements (TanDEM-X), and airborne Light Detection and Ranging (LiDAR) digital elevation models. The results indicated a mean regional glacier mass balance of −0.12 ± 0.06 m w.e.a−1, with a total mass loss of 2.43 ± 0.26 Gt for the Maipo River Basin between 1955–2013. The most negative glacier mass balance was the Olivares sub-basin, with a mean value of −0.29 ± 0.07 m w.e.a−1. We observed spatially heterogeneous glacier elevation and mass changes between 1955 and 2000, and more negative values between 2000 and 2013, with an acceleration in ice thinning rates starting in 2010, which coincides with the severe drought. Our results provide key information to improve glaciological and hydrological projections in a region where water resources are under pressure.
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Vanbeveren, Dany. "Close pairs: keys to comprehension of star cluster evolution." Proceedings of the International Astronomical Union 5, S266 (August 2009): 293–303. http://dx.doi.org/10.1017/s1743921309991165.
Повний текст джерелаАнотація:
AbstractIn this review I first summarize why binaries are key objects in the study of stellar populations, to understand the evolution of star clusters and galaxies, and thus to understand the universe. I then focus on four specific topics: (i)the formation (through binaries) and evolution of very massive stars in dense clusters and the importance of stellar-wind mass loss. I discuss preliminary computations of wind mass-loss rates of very massive stars performed with the Munich hydrodynamical code and the influence of these new rates on the possible formation of an intermediate-mass black hole in the cluster MGG 11 in M82;(ii)the evolution of intermediate-mass binaries in a starburst with special emphasis on the variation of the supernova (SN) Ia rate (i.e., on the delayed time distribution of SNe Ia). A comparison with SN Ia rates in elliptical galaxies may provide important clues to SN Ia models as well as to the evolution of SN Ia progenitors;(iii)the evolution of double-neutron-star mergers in a starburst (i.e., the delayed time distribution of these mergers) and what this tells us about the suggestion that these mergers may be important production sites of r-process elements;(iv)the possible effect of massive binaries on the self-enrichment of globular clusters.
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Stone, G. N. "ENDOTHERMY IN THE SOLITARY BEE ANTHOPHORA PLUMIPES: INDEPENDENT MEASURES OF THERMOREGULATORY ABILITY, COSTS OF WARM-UP AND THE ROLE OF BODY SIZE." Journal of Experimental Biology 174, no. 1 (January 1, 1993): 299–320. http://dx.doi.org/10.1242/jeb.174.1.299.
Повний текст джерелаАнотація:
1. This study examines variation in thoracic temperatures, rates of pre-flight warm-up and heat loss in the solitary bee Anthophora plumipes (Hymenoptera; Anthophoridae). 2. Thoracic temperatures were measured both during free flight in the field and during tethered flight in the laboratory, over a range of ambient temperatures. These two techniques give independent measures of thermoregulatory ability. In terms of the gradient of thoracic temperature on ambient temperature, thermoregulation by A. plumipes is more effective before flight than during flight. 3. Warm-up rates and body temperatures correlate positively with body mass, while mass-specific rates of heat loss correlate negatively with body mass. Larger bees are significantly more likely to achieve flight temperatures at low ambient temperatures. 4. Simultaneous measurement of thoracic and abdominal temperatures shows that A. plumipes is capable of regulating heat flow between thorax and abdomen. Accelerated thoracic cooling is only demonstrated at high ambient temperatures. 5. Anthophora plumipes is able to fly at low ambient temperatures by tolerating thoracic temperatures as low as 25 sC, reducing the metabolic expense of endothermic activity. 6. Rates of heat generation and loss are used to calculate the thermal power generated by A. plumipes and the total energetic cost of warm-up under different thermal conditions. The power generated increases with thoracic temperature excess and ambient temperature. The total cost of warm-up correlates negatively with ambient temperature.
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Uttenthaler, S., I. McDonald, K. Bernhard, S. Cristallo, and D. Gobrecht. "Interplay between pulsation, mass loss, and third dredge-up: More about Miras with and without technetium." Astronomy & Astrophysics 622 (February 2019): A120. http://dx.doi.org/10.1051/0004-6361/201833794.
Повний текст джерелаАнотація:
Context. We follow-up on a previous finding that AGB Mira variables containing the third dredge-up indicator technetium (Tc) in their atmosphere form a different sequence of K − [22] colour as a function of pulsation period than Miras without Tc. A near- to mid-infrared colour such as K − [22] is a good probe for the dust mass-loss rate of the stars. Contrary to what might be expected, Tc-poor Miras show redder K − [22] colours (i.e. higher dust mass-loss rates) than Tc-rich Miras at a given period. Aims. Here, the previous sample is extended and the analysis is expanded towards other colours and dust spectra. The most important aim is to investigate if the same two sequences can be revealed in the gas mass-loss rate. Methods. We analysed new optical spectra and expanded the sample by including more stars from the literature. Near- and mid-IR photometry and ISO dust spectra of our stars were investigated where available. Literature data of gas mass-loss rates of Miras and semi-regular variables were collected and analysed. Results. Our results show that Tc-poor Miras are redder than Tc-rich Miras in a broad range of the mid-IR, suggesting that the previous finding based on the K − [22] colour is not due to a specific dust feature in the 22 μm band. We establish a linear relation between K − [22] and the gas mass-loss rate. We also find that the 13 μm feature disappears above K − [22]≃2.17 mag, corresponding to Ṁg ∼ 2.6 × 10−7 M⊙ yr−1. No similar sequences of Tc-poor and Tc-rich Miras in the gas mass-loss rate vs. period diagram are found, most probably owing to limitations in the available data. Conclusions. Different hypotheses to explain the observation of two sequences in the P vs. K − [22] diagram are discussed and tested, but so far, none of them convincingly explains the observations. Nevertheless, we might have found an hitherto unknown but potentially important process influencing mass loss on the TP-AGB.
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Houlihan, D. F., K. Kelly, and P. R. Boyle. "Correlates of Growth and Feeding in Laboratory-Maintained Eledone Cirrhosa (Cephalopoda: Octopoda)." Journal of the Marine Biological Association of the United Kingdom 78, no. 3 (August 1998): 919–32. http://dx.doi.org/10.1017/s0025315400044878.
Повний текст джерелаАнотація:
Octopuses (Eledone cirrhosa (Octopoda: Cephalopoda)) held in an aquarium were subjected to varying conditions of feeding and starvation to evaluate putative indices of feeding and growth. Specific growth rate (%d−1) was linearly related to feeding rate (% of the body mass d−1) in animals with a mean body mass of 250 g at 15°C. Maximum growth rates varied between > 2% d−1 (body weights < 300 g) to < 1% d−1 (body weights ≤ 900 g) but specific growth rates were not related to body weight. Growth rates became negative (weight loss) after one week without food.The digestive gland index (DGI) was significantly correlated with short and long-term feeding and specific growth rates, and with body weight. Muscle RNA concentration was linearly correlated with growth rate during the previous 1–3 weeks but not with feeding rate. RNA:protein ratios were not different between mid-arm and mantle sample sites but arm tip values were significantly higher. RNA:protein ratio was related to body weight only in feeding animals. It is concluded that DGI is an index of feeding rate and that RNA:protein ratio can be used as an index of recent (~ 4 weeks) growth rate.
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Ramdani, Ghania, Nadine Schall, Hema Kalyanaraman, Nisreen Wahwah, Sahar Moheize, Jenna J. Lee, Robert L. Sah, Alexander Pfeifer, Darren E. Casteel, and Renate B. Pilz. "cGMP-dependent protein kinase-2 regulates bone mass and prevents diabetic bone loss." Journal of Endocrinology 238, no. 3 (September 2018): 203–19. http://dx.doi.org/10.1530/joe-18-0286.
Повний текст джерелаАнотація:
NO/cGMP signaling is important for bone remodeling in response to mechanical and hormonal stimuli, but the downstream mediator(s) regulating skeletal homeostasis are incompletely defined. We generated transgenic mice expressing a partly-activated, mutant cGMP-dependent protein kinase type 2 (PKG2R242Q) under control of the osteoblast-specific Col1a1 promoter to characterize the role of PKG2 in post-natal bone formation. Primary osteoblasts from these mice showed a two- to three-fold increase in basal and total PKG2 activity; they proliferated faster and were resistant to apoptosis compared to cells from WT mice. Male Col1a1-Prkg2 R242Q transgenic mice had increased osteoblast numbers, bone formation rates and Wnt/β-catenin-related gene expression in bone and a higher trabecular bone mass compared to their WT littermates. Streptozotocin-induced type 1 diabetes suppressed bone formation and caused rapid bone loss in WT mice, but male transgenic mice were protected from these effects. Surprisingly, we found no significant difference in bone micro-architecture or Wnt/β-catenin-related gene expression between female WT and transgenic mice; female mice of both genotypes showed higher systemic and osteoblastic NO/cGMP generation compared to their male counterparts, and a higher level of endogenous PKG2 activity may be responsible for masking effects of the PKG2R242Q transgene in females. Our data support sexual dimorphism in Wnt/β-catenin signaling and PKG2 regulation of this crucial pathway in bone homeostasis. This work establishes PKG2 as a key regulator of osteoblast proliferation and post-natal bone formation.
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Albright, Thomas P., Denis Mutiibwa, Alexander R. Gerson, Eric Krabbe Smith, William A. Talbot, Jacqueline J. O’Neill, Andrew E. McKechnie, and Blair O. Wolf. "Mapping evaporative water loss in desert passerines reveals an expanding threat of lethal dehydration." Proceedings of the National Academy of Sciences 114, no. 9 (February 13, 2017): 2283–88. http://dx.doi.org/10.1073/pnas.1613625114.
Повний текст джерелаАнотація:
Extreme high environmental temperatures produce a variety of consequences for wildlife, including mass die-offs. Heat waves are increasing in frequency, intensity, and extent, and are projected to increase further under climate change. However, the spatial and temporal dynamics of die-off risk are poorly understood. Here, we examine the effects of heat waves on evaporative water loss (EWL) and survival in five desert passerine birds across the southwestern United States using a combination of physiological data, mechanistically informed models, and hourly geospatial temperature data. We ask how rates of EWL vary with temperature across species; how frequently, over what areas, and how rapidly lethal dehydration occurs; how EWL and die-off risk vary with body mass; and how die-off risk is affected by climate warming. We find that smaller-bodied passerines are subject to higher rates of mass-specific EWL than larger-bodied counterparts and thus encounter potentially lethal conditions much more frequently, over shorter daily intervals, and over larger geographic areas. Warming by 4 °C greatly expands the extent, frequency, and intensity of dehydration risk, and introduces new threats for larger passerine birds, particularly those with limited geographic ranges. Our models reveal that increasing air temperatures and heat wave occurrence will potentially have important impacts on the water balance, daily activity, and geographic distribution of arid-zone birds. Impacts may be exacerbated by chronic effects and interactions with other environmental changes. This work underscores the importance of acute risks of high temperatures, particularly for small-bodied species, and suggests conservation of thermal refugia and water sources.
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Bederman, Ilya R., Nicola Lai, Jeffrey Shuster, Leigh Henderson, Steven Ewart, and Marco E. Cabrera. "Chronic hindlimb suspension unloading markedly decreases turnover rates of skeletal and cardiac muscle proteins and adipose tissue triglycerides." Journal of Applied Physiology 119, no. 1 (July 1, 2015): 16–26. http://dx.doi.org/10.1152/japplphysiol.00004.2014.
Повний текст джерелаАнотація:
We previously showed that a single bolus of “doubly-labeled” water (2H218O) can be used to simultaneously determine energy expenditure and turnover rates (synthesis and degradation) of tissue-specific lipids and proteins by modeling labeling patterns of protein-bound alanine and triglyceride-bound glycerol (Bederman IR, Dufner DA, Alexander JC, Previs SF. Am J Physiol Endocrinol Metab 290: E1048–E1056, 2006). Using this novel method, we quantified changes in the whole body and tissue-specific energy balance in a rat model of simulated “microgravity” induced by hindlimb suspension unloading (HSU). After chronic HSU (3 wk), rats exhibited marked atrophy of skeletal and cardiac muscles and significant decrease in adipose tissue mass. For example, soleus muscle mass progressively decreased 11, 43, and 52%. We found similar energy expenditure between control (90 ± 3 kcal·kg−1·day−1) and hindlimb suspended (81 ± 6 kcal/kg day) animals. By comparing food intake (∼112 kcal·kg−1·day−1) and expenditure, we found that animals maintained positive calorie balance proportional to their body weight. From multicompartmental fitting of 2H-labeling patterns, we found significantly ( P < 0.005) decreased rates of synthesis (percent decrease from control: cardiac, 25.5%; soleus, 70.3%; extensor digitorum longus, 44.9%; gastrocnemius, 52.5%; and adipose tissue, 39.5%) and rates of degradation (muscles: cardiac, 9.7%; soleus, 52.0%; extensor digitorum longus, 27.8%; gastrocnemius, 37.4%; and adipose tissue, 50.2%). Overall, HSU affected growth of young rats by decreasing the turnover rates of proteins in skeletal and cardiac muscles and adipose tissue triglycerides. Specifically, we found that synthesis rates of skeletal and cardiac muscle proteins were affected to a much greater degree compared with the decrease in degradation rates, resulting in large negative balance and significant tissue loss. In contrast, we found a small decrease in adipose tissue triglyceride synthesis paired with a large decrease in degradation, resulting in smaller negative energy balance and loss of fat mass. We conclude that HSU in rats differentially affects turnover of muscle proteins vs. adipose tissue triglycerides.
Дисертації з теми "Mass specific mass loss rates"
1
St-Louis, N., and Anthony F. J. Moffat. "Do clumping corrections increase with decreasing mass-loss rates?" Universität Potsdam, 2007. http://opus.kobv.de/ubp/volltexte/2008/1769/.
Повний текст джерелаАнотація:
We report on new mass-loss rate estimates for O stars in six massive binaries using the amplitude of orbital-phase dependent, linear-polarimetric variability caused by electron scattering off free electrons in the winds. Our estimated mass-loss rates for luminous O stars are independent of clumping. They suggest similar clumping corrections as for WR stars and do not support the recently proposed reduction in mass-loss rates of O stars by one or two orders of magnitude.
2
Smith, Nathan. "Independent signs of lower mass-loss rates for O-type stars." Universität Potsdam, 2007. http://opus.kobv.de/ubp/volltexte/2008/1765/.
Повний текст джерелаАнотація:
I discuss observational evidence – independent of the direct spectral diagnostics of stellar winds themselves – suggesting that mass-loss rates for O stars need to be revised downward by roughly a factor of three or more, in line with recent observed mass-loss rates for clumped winds. These independent constraints include the large observed mass-loss rates in LBV eruptions, the large masses of evolved massive stars like LBVs and WNH stars, WR stars in lower metallicity environments, observed rotation rates of massive stars at different metallicity, supernovae that seem to defy expectations of high mass-loss rates in stellar evolution, and other clues. I pay particular attention to the role of feedback that would result from higher mass-loss rates, driving the star to the Eddington limit too soon, and therefore making higher rates appear highly implausible. Some of these arguments by themselves may have more than one interpretation, but together they paint a consistent picture that steady line-driven winds of O-type stars have lower mass-loss rates and are significantly clumped.
3
Fullerton, A. W., D. L. Massa, and R. K. Prinja. "Revised mass-loss rates for O stars from the Pv resonance line." Universität Potsdam, 2007. http://opus.kobv.de/ubp/volltexte/2008/1764/.
Повний текст джерелаАнотація:
The P v λλ1118, 1128 resonance doublet is an extraordinarily useful diagnostic of O-star winds, because it bypasses the traditional problems associated with determining mass-loss rates from UV resonance lines. We discuss critically the assumptions and uncertainties involved with using P v to diagnose mass-loss rates, and conclude that the large discrepancies between massloss rates determined from P v and the rates determined from “density squared” emission processes pose a significant challenge to the “standard model” of hot-star winds. The disparate measurements can be reconciled if the winds of O-type stars are strongly clumped on small spatial scales, which in turn implies that mass-loss rates based on Hα or radio emission are too large by up to an order of magnitude.
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Hirschi, Raphael. "The impact of reduced mass loss rates on the evolution of massive stars." Universität Potsdam, 2007. http://opus.kobv.de/ubp/volltexte/2008/1761/.
Повний текст джерелаАнотація:
Mass loss is a very important aspect of the life of massive stars. After briefly reviewing its importance, we discuss the impact of the recently proposed downward revision of mass loss rates due to clumping (difficulty to form Wolf-Rayet stars and production of critically rotating stars). Although a small reduction might be allowed, large reduction factors around ten are disfavoured.
We then discuss the possibility of significant mass loss at very low metallicity due to stars reaching break-up velocities and especially due to the metal enrichment of the surface of the star via rotational and convective mixing. This significant mass loss may help the first very massive stars avoid the fate of pair-creation supernova, the chemical signature of which is not observed in extremely metal poor stars. The chemical composition of the very low metallicity winds is very similar to that of the most metal poor star known to date, HE1327-2326 and offer an interesting explanation for the origin of the metals in this star.
We also discuss the importance of mass loss in the context of long and soft gamma-ray bursts and pair-creation supernovae. Finally, we would like to stress that mass loss in cooler parts of the HR-diagram (luminous blue variable and yellow and red supergiant stages) are much more uncertain than in the hot part. More work needs to be done in these areas to better constrain the evolution of the most massive stars.
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Norberg, Samuelsson Lina. "Isoconversional analysis for the prediction of mass-loss rates during pyrolysis of biomass." Doctoral thesis, KTH, Energiprocesser, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-187469.
Повний текст джерелаАнотація:
Biomass is the only renewable carbon source that can compete with fossil energy sources in terms of production of materials, chemicals and fuels. Biomass can be transformed into charcoal, liquid and gas through pyrolysis, i.e. pure thermal decomposition. By changing the pyrolysis conditions either solid, liquid or gaseous fractions can become the main product and pyrolysis is thus a very versatile process. Pyrolysis is also the first step in combustion and gasification, two important thermal processes in our society. The importance of biomass pyrolysis has led to extensive research in this area but due to the complexity of the process there is still no general understanding of how to describe biomass pyrolysis, which is essential in order to optimize thermal processes. The research presented in this thesis thus aims at finding a simple yet accurate way to model the decomposition rate of biomass during pyrolysis. Thermogravimetric analysis, a well known method that is simple to use, was chosen to collect the experimental data used for kinetic evaluation. The reaction kinetics were derived using two different model-free, isoconversional methods, i.e. the non-linear form of the Friedman method and the incremental, integral method ofVyazovkin. By using these two methods and experimental data, complete reactionrate expressions could be derived for commercial cellulose, Norway spruce and seven different samples originating from kraft cooking, the most common process to produce pulp for the paper industry. The derivation of model-free rate expressions have never been performed before for these materials and since the rate expressions are model-free, no assumptions or knowledge about the pyrolysis reactions were required. This is a great advantage compared to the commonly used model-fitting methods that rely on information about these aspects. All therate expressions were successful in predicting mass-loss rates at extrapolated pyrolysis conditions. This is a clear indication of the soundness of the methodologypresented in this thesis.Biomassa är den enda förnybara kolkällan som kan konkurrera med fossila energikällor när det gäller produktion av material, kemikalier och bränslen. Biomassakan omvandlas till biokol, bioolja och gas med hjälp av pyrolys, dvs termisk nedbrytning. Genom att variera de processförhållanden som råder under pyrolysen kan man få antingen fast, flytande eller gasfasiga ämnen som huvudprodukt, något som gör pyrolys väldigt flexibelt. Utöver detta är pyrolys även betydelsefull vid förbränning och förgasning, två viktiga processer i dagens samhälle. Vikten av biomassapyrolys har resulterat i omfattande forskning inom området men pga biomassas komplexa natur råder det ännu ingen enighet gällande hur biomassapyrolys bör modelleras. Detta försvårar utveckling och optimering av termiska processer matade med biomassa. Forskningen som presenteras i denna avhandling fokuserar således på att finna en enkel men noggrann metod för att beskriva hastigheten med vilken biomassa bryts ned under pyrolys. Termogravimetrisk analys, en vanligt förekommande metod som är enkel att använda, valdes för att samla in experimentell data som kan användas för att undersöka hastigheten för termisk nedbrytning, dvs kinetiken. Två olika metoder som på engelska går under benämningen “model-free” och “isoconversional” har använts, nämligen den icke-linjära formen av Friedmans metod och den stegvisa, integrala metoden som utvecklats av Vyazovkin. Genom att använda dessa två metoder och experimentell data kunde kompletta reaktionshastighetsuttryck tas fram för kommersiell cellulosa, gran och sju olika material framställda genom sulfatprocessen, den idag vanligast förekommande pappersmassaprocessen. Pyrolyskinetiken för dessa material har aldrig tidigare analyserats med dessa två metoder och fördelarna med metoderna gjorde det möjligt att bestämma hastighetsuttryck utan någon kunskap om de pågående reaktionerna. Detta är en viktig fördel jämfört med andra metoder som är beroende av sådan information. Alla framtagna reaktionshatighetsuttryck kunde användas för att framgångsrikt förutsäga minskningen av massa vid extrapolerade pyrolysförhållanden. Detta är en tydlig indikation på att metoden använd i denna avhandling fungerar väl.
QC 20160524
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Liermann, A., and Wolf-Rainer Hamann. "Clumping in Galactic WN stars : a comparison of mass loss rates from UV/optical & radio diagnostics." Universität Potsdam, 2007. http://opus.kobv.de/ubp/volltexte/2008/1781/.
Повний текст джерелаАнотація:
The mass loss rates and other parameters for a large sample of Galactic WN stars have been revised by Hamann et al. (2006), using the most up-to date Potsdam Wolf-Rayet (PoWR) model atmospheres. For a sub-sample of these stars exist measurements of their radio free-free emission. After harmonizing the adopted distance and terminal wind velocities, we compare the mass loss rates obtained from the two diagnostics. The differences are discussed as a possible consequence of different clumping contrast in the line-forming and radio-emitting regions.
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Sundqvist, Jon. "Quantitative spectroscopy of stellar atmospheres and clumped hot star winds - new methods and first results for deriving mass-loss rates." Diss., lmu, 2010. http://nbn-resolving.de/urn:nbn:de:bvb:19-126131.
Повний текст джерела
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Pearson, Hoover Patricia. "Rates of bone loss in postmenopausal women, relationship to calcium intake, calcium absorption, serum estrogen, body mass and physical activity." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0034/NQ66231.pdf.
Повний текст джерела
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Alhawat, Musab M. "Bond Performance between Corroded Steel and Recycled Aggregate Concrete Incorporating Nano Silica." Thesis, University of Bradford, 2020. http://hdl.handle.net/10454/18430.
Повний текст джерелаАнотація:
The current research project mainly aims to investigate the corrosion resistance and bond
performance of steel reinforced recycled aggregate concrete incorporating nano-silica under
both normal and corrosive environmental conditions. The experimental part includes testing
of 180 pull-out specimens prepared from 12 different mixtures. The main parameters studied
were the amount of recycled aggregate (RCA) (i.e. 0%, 25%, 50% and 100%), nano silica
(1.5% and 3%), steel embedment length as well as steel bar diameter (12 and 20mm).
Different levels of corrosion were electrochemically induced by applying impressed voltage
technique for 2, 5, 10 and 15 days. The experimental observations mainly focused on the
corrosion level in addition to the ultimate bond, failure modes and slips occurred.
Experimental results showed that the bond performance between un-corroded steel and
recycled aggregate concrete slightly reduced, while a significant degradation was observed
after being exposed to corrosive conditions, in comparison to normal concrete. On the other
hand, the use of nano silica (NS) showed a reasonable bond enhancement with both normal
and RCA concretes under normal conditions. However, much better influence in terms of bond
and corrosion resistance was observed under advancing levels of corrosion exposure,
reflecting the improvement in corrosion resistance. Therefore, NS was superbly effective in
recovering the poor performance in bond for RCA concretes. More efficiency was reported
with RCA concretes compared to the conventional concrete. The bond resistance slightly with
a small amount of corrosion (almost 2% weight loss), then a significant bond degradation
occurs with further corrosion.
The influence of specific surface area and amount of nano silica on the performance of concrete
with different water/binder (w/b) ratios has been also studied, using 63 different mixtures produced
with three different types of colloidal NS having various surface areas and particle sizes. The
results showed that the performance of concrete is heavily influenced by changing the surface area
of nano silica. Amongst the three used types of nano silica, NS with SSA of 250 m2
/g achieved the highest enhancement rate in terms of compressive strength, water absorption and
microstructure analysis, followed by NS with SSA of 500 m2/g, whilst NS with SSA of 51.4
m2
/g was less advantageous for all mixtures. The optimum nano silica ratio in concrete is
affected by its particle size as well as water to binder ratio.
The feasibility of the impact-echo method for identifying the corrosion was evaluated and
compared to the corrosion obtained by mass loss method. The results showed that the impact-echo testing can be effectively used to qualitatively detect the damage caused by corrosion in
reinforced concrete structures. A significant difference in the dominant frequencies response
was observed after exposure to the high and moderate levels of corrosion, whilst no clear
trend was observed at the initial stage of corrosion.
Artificial neural network models were also developed to predict bond strength for corroded/uncorroded steel bars in concrete using the main influencing parameters (i.e., concrete strength, concrete cover, bar diameter, embedment length and corrosion rate). The developed models
were able to predict the bond strength with a high level of accuracy, which was confirmed by
conducting a parametric study.Higher Education Institute in the Libyan Government MONE BROS Company in Leeds (UK) for providing recycled aggregates BASF and Akzonobel Companies for providing nano silica NS, Hanson Ltd, UK, for suppling cement
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Plotz, Roan. "Growth and Fasting Strategies of New Zealand Fur Seal, Arctocephalus forsteri, Pups at Cape Gantheaume, Kangaroo Island." Thesis, 2003. https://vuir.vu.edu.au/39233/.
Повний текст джерелаАнотація:
New Zealand fur seals (Arctocephalus forsteri) show pronounced inter-sexual differences in adult body size, and males will potentially mate with many females. Consequently, selection is thought to act differently upon pups during growth. Little is known about how male and female fur seal pups conserve energy, and use milk for growth especially as they fast for significant periods. There has been a plethora of studies that have viewed pinnipeds as ideal models for the differential investment theory, but the evidence remains equivocal. This study investigated a species that has shown some support for differential investment in the past, in the form of pup growth and maternal attendance behaviour, and looked at the potential that these intersexual differences are due to differential utilisation of maternal resources (different body compositions) and/or differential fasting strategies by pups, which may be determined by fasting mass loss rates. This study hopes to encompass both aspects of differential investment, such as maternal attendance, as well as differential fasting strategies of pups by looking at their fasting mass loss rates. This study found that males were larger and longer throughout the lactation period, yet grew at the same rate as females. There was no detectable intersexual difference in the maternal provisioning provided by mothers, in the form of attendance. There was some evidence that males and females have different fasting strategies, in that females, from a subset of pups exhibited significantly higher mass specific mass loss rates. This finding should be treated with caution however, as sample size was low, and cross sectional samples revealed no significant differences. Furthermore, study of the activity rates of the same pups over the duration of the fast, found no significant intersexual differences in activity rates. These results suggest that further studies are needed that encompass both aspects of differential investment theory, as well as differential utilisation by pups.
Книги з теми "Mass specific mass loss rates"
1
So, Emily. Estimating Fatality Rates for Earthquake Loss Models. Springer, 2016.
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2
So, Emily. Estimating Fatality Rates for Earthquake Loss Models. Springer London, Limited, 2015.
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3
R, Knapp G., and United States. National Aeronautics and Space Administration., eds. Measurement of the sizes of circumstellar dust shells around evolved stars with high mass loss rates. [Washington, DC: National Aeronautics and Space Administration, 1992.
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4
O’Neal, M. Angela. Ringing in the Ears and Pain in the Head. Edited by Angela O’Neal. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780190609917.003.0015.
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The case illustrates the classic clinical features of a low-pressure headache. The pathophysiology results from the loss of cerebrospinal fluid (CSF). This causes sagging of the brain, stretching of the bridging veins, and venodilatation. The clinical history is of a headache that is worse in the upright position and remits when the patient is supine. Due to the connection of the perilymphatic fluid and CSF, postural tinnitus is a frequent symptom. Risk factors for low-pressure headache include those that are patient-specific: female sex, low body mass index, prior history of a low-pressure headache, and an underlying headache disorder. Operator-specific factors that decrease the risk of a postdural puncture headache (PDPH) include greater operator experience and the use of a smaller-gauge, non-cutting lumbar puncture needle. The best treatment for low-pressure headache is a blood patch with resolution in over 90% of low-pressure headaches.
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Aisiku, Imoigele, and Claudia S. Robertson. Epidemiology and pathophysiology of traumatic brain injury. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780199600830.003.0341.
Повний текст джерелаАнотація:
Although medical management of traumatic brain injury (TBI) may have improved in developed countries, TBI is still a major cause of mortality and morbidity. The demographics are skewed towards the younger patient population, and affects males more than females, but in general follow a bimodal distribution with peaks affecting young adults and the elderly. As a result, the loss of functional years is devastating. Pathology due to brain trauma is a complex two-hit phenomenon, frequently divided into ‘primary’ and ‘secondary’ injury. Hypoxia, ischaemia, and inflammation all play a role, and the importance of each component varies between patients and in an individual patient over time. The initial injury may increase intracranial pressure and reduce cerebral perfusion due to the presence of mass lesions or diffuse brain swelling. Further secondary insults, such as hypotension, reduced cerebral perfusion pressure, hypoxia, or fever may exacerbate swelling and inflammation, and further compromise cerebral perfusion. Although there are currently no specific effective treatments for TBI, an improved understanding of the pathophysiology may eventually lead to treatments that will reduce mortality and improve long-term functional outcome.
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Falk, Bareket, and Raffy Dotan. Temperature regulation. Edited by Neil Armstrong and Willem van Mechelen. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780198757672.003.0014.
Повний текст джерелаАнотація:
Under all but the most extreme environmental heat conditions, children control their body temperature (at rest and during exercise) as well as adults. Children, however, use a different thermoregulatory strategy. Compared with adults, children rely more on dry heat dissipation and less on evaporative cooling (sweating). Their larger skin surface-area relative to mass does put children at increasing disadvantage, relative to adults, as ambient temperatures rise above skin temperature. Similarly, they become increasingly disadvantaged upon exposure to decreasing temperatures below the thermo-neutral zone. Like adults, children inadvertently dehydrate while exercising in hot conditions and are often hypohydrated, even before exercise, and their core temperature rises considerably more than adults in response to a given fluid (sweat) loss, which may put them at higher risk for heat-related injury. However, epidemiological data show rates of both heat- and cold-related injuries among children and adolescents as similar or lower than at any other age.
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Smil, Vaclav. Grand Transitions. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780190060664.001.0001.
Повний текст джерелаАнотація:
The modern world was created through the combination and complex interactions of five grand transitions. First, the demographic transition changed the total numbers, dynamics, structure, and residential pattern of populations. The agricultural and dietary transition led to the emergence of highly productive cropping and animal husbandry (subsidized by fossil energies and electricity), a change that eliminated famines, reduced malnutrition, and improved the health of populations but also resulted in enormous food waste and had many environmental consequences. The energy transition brought the world from traditional biomass fuels and human and animal labor to fossil fuel, ever more efficient electricity, lights, and motors, all of which transformed both agricultural and industrial production and enabled mass-scale mobility and instant communication. Economic transition has been marked by relatively high growth rates of total national and global product, by fundamental structural transformation (from farming to industries to services), and by an increasing share of humanity living in affluent societies, enjoying unprecedented quality of life. These transitions have made many intensifying demands on the environment, resulting in ecosystemic degradation, loss of biodiversity, pollution, and eventually change on the planetary level, with global warming being the most worrisome development. This book traces the genesis of these transitions, their interactions and complicated progress as well as their outcomes and impacts, explaining how the modern world was made—and then offers a forward-thinking examination of some key unfolding transitions and appraising their challenges and possible results.
Частини книг з теми "Mass specific mass loss rates"
1
Singh, P. D., W. F. Huebner, D. C. Boice, I. Konno, and E. Scalise. "Mass Loss Rates of Three Comets." In Astrochemistry of Cosmic Phenomena, 447–48. Dordrecht: Springer Netherlands, 1992. http://dx.doi.org/10.1007/978-94-011-2761-5_110.
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Johnston, Kathryn V., Steinn Sigurdsson, and Lars Hernquist. "Measuring Mass Loss Rates from Galactic Satellites." In Impact of Modern Dynamics in Astronomy, 397–98. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-011-4527-5_53.
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Vink, Jorick S. "Mass-Loss Rates of Very Massive Stars." In Very Massive Stars in the Local Universe, 77–111. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-09596-7_4.
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De Freitas Pacheco, J. A. "Mass Loss Rates from B[e] Stars." In B[e] Stars, 221–25. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-015-9014-3_24.
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Grewing, M., L. Bianchi, and M. Gutekunst. "Temperatures, Luminosities and Mass Loss Rates for PN Nuclei." In Planetary and Proto-Planetary Nebulae: From IRAS to ISO, 101–6. Dordrecht: Springer Netherlands, 1987. http://dx.doi.org/10.1007/978-94-009-3891-5_11.
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Perinotto, M. "Mass Loss Rates in Central Stars of Planetary Nebulae." In Planetary Nebulae, 293–300. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-0865-9_105.
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Hutsemékers, D., and J. Surdej. "Improved First Order Moment Method for Determination of Mass-Loss Rates." In Mass Outflows from Stars and Galactic Nuclei, 253–56. Dordrecht: Springer Netherlands, 1988. http://dx.doi.org/10.1007/978-94-009-2941-8_27.
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Waters, L. B. F. M. "The Disc Structure and Mass Loss Rates of Be Stars." In Light on Dark Matter, 83–86. Dordrecht: Springer Netherlands, 1986. http://dx.doi.org/10.1007/978-94-009-4672-9_15.
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Hutsemékers, D., and J. Surdej. "Revisited Mass-Loss Rates of Planetary Nebula Nuclei Observed with IUE." In Planetary Nebulae, 317. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-0865-9_124.
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Fernández, Matilde, Carlos Eiroa, and William Schuster. "Hot Spots on Classical T Tauri Stars with High Mass-Loss Rates." In ESO Astrophysics Symposia, 160–63. Berlin, Heidelberg: Springer Berlin Heidelberg, 1998. http://dx.doi.org/10.1007/978-3-540-68597-5_38.
Повний текст джерелаТези доповідей конференцій з теми "Mass specific mass loss rates"
1
Hedayat Mofidi, Seyyed Ali, and Kent S. Udell. "Study of Heat and Mass Transfer in MgCl2/NH3 Thermo-Chemical Batteries." In ASME 2016 10th International Conference on Energy Sustainability collocated with the ASME 2016 Power Conference and the ASME 2016 14th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/es2016-59099.
Повний текст джерелаАнотація:
Intermittency of sustainable energy or waste heat availability calls for energy storage systems such as thermal batteries. Thermo-chemical batteries are particularly appealing for energy storage applications due to their high energy densities and ability to store thermal energy as chemical energy for long periods of time without any energy loss. Thermo-chemical batteries based on a reversible solid-gas (MgCl2 - NH3) reactions and NH3 liquid-gas phase change are of specific interest since the kinetics of absorption are fast and the heat transfer rates for liquid — vapor phase change are high. Thus, a thermo-chemical battery based on reversible reaction between magnesium chloride and ammonia was studied. Experimental studies were conducted on a reactor in which temperature profiles within the solid matrix and pressure and flow rates of gas were obtained during charging processes. A numerical model based on heat and mass transfer within the salt and salt-gas reactions was developed to simulate the absorption processes within the solid matrix and the results were compared with experimental data. The studies were used to determine dominant heat and mass transfer processes within the salt. It is shown that for high permeability materials, heat transfer is the dominant factor in determining reaction rates. However increasing thermal conductivity might decrease permeability and reduce reaction rates. The effect of constraining mass flow rate on the temperature and reaction propagation is also studied. These results show that optimized heat and mass transfer within the solid-gas reactor will lead to improved performance for heating and air conditioning applications.
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Ng, B. C. N., and A. M. Birk. "CFD Simulations of Full Surface Passive Effusion Mass Injections in a Rectangular S-Bend Diffuser." In ASME Turbo Expo 2013: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gt2013-94700.
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A coarse grid CFD methodology was employed to simulate internal flow passages with full coverage effusion cooling by imposing momentum sinks on effusion cooled surfaces based on a perforated plate pressure loss analogy. The methodology was implemented by specifying 1D Porous Jump boundary conditions (available in ANSYS FLUENT) on the effusion cooled surfaces. Numerical simulations were conducted based on the experimental data of an S-duct diffusing passage where ambient air was passively drawn into the sub-atmospheric passage along the different effusion surfaces with 1 mm diameter holes spaced 4 mm apart. The porous wall simulations were also compared to an alternative CFD approach with mass inlet boundary specified on the effusion surfaces. The proposed porous wall model is promising for practical design applications with the reasonable simulations of the S-duct flow fields with effusion injections. A reasonable accuracy in the results of injection mass flow rates was also obtained for the different effusion configurations. Discrepancies in the simulations of flow momentum components were mainly contributed to the diminishing effects of discrete injections at the aft-section of cooling surface due to the development of a shear layer across the free surfaces (porous jump boundaries) between the main flow and coolant flow.
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Trifale, Ninad, Eric Nauman, and Kazuaki Yazawa. "Analytic Optimization of Porous Medium Heat Sinks for Energy Efficiency and Minimum Mass." In ASME 2013 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ipack2013-73187.
Повний текст джерелаАнотація:
Use of microchannel heat sinks for high heat flux applications is substantial for thermal management and it is also critical for scalable power generation. For both applications, the energy efficiency consideration of the pump power is crucial. A number of models have been created that predict the performance as a function of the geometrical parameters, taking into account, the pressure loss over the length and volume constraints. Most of the approaches either involve sophisticated calculations incorporating fluid dynamics in channels, or have an analogy with the pin-fin model, which gives simpler calculations but considers only a single laminar flow regime for optimization. Even with the simplified models available, the geometrical impact on mass and pumping power is nonlinear and not apparent for optimization. We propose an optimization of porous medium heat sinks with respect to the heat transfer rate, mass, and pumping power. These are functions of the simplest geometric parameters, i.e. porosity, pore density, and length of the porous medium. Considering large production, mass (cost of raw material) is nearly proportional to the cost of the heat sink, we consider minimizing the mass for indirectly minimizing the overall cost. The other factor for saving energy considered here is the pumping power. This connects to both the heat transfer rate and the power consumption to drive the fluid through the porous medium. The optimization is performed for a specific value of porosity and length of the heat sink. The model considers the effect of flow through the porous medium and the effective thermal conduction as a function of combined conductivity of the solid ligaments and the fluid in pores. An optimum coefficient of performance (COP) is found at over 90% of porosity for minimum mass, pumping work and maximum heat transfer. This mathematical expression of the model will give a quantifiable figure-of-merit to take into account the impact of the mass and the pumping power on the performance to cost ratio.
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Duan, P. H., and L. He. "Vortical Structures and Loss Mechanism of Tip Leakage Flow In Subsonic and Transonic Turbine Stages." In ASME Turbo Expo 2022: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/gt2022-83473.
Повний текст джерелаАнотація:
Abstract Aerothermal behavior and performance of turbine blade squealer tip has been extensively studied, but previously mainly confined to very low speed flows. Some recent research efforts have revealed some distinctive tip heat transfer as well as aerodynamic characteristics in a transonic flow, many of which are confined to a linear cascade setting. There is a need to identify driving mechanisms for such configurations and to quantify corresponding performance characteristics in general, and in the process address how those drivers would relate to some specific issues of interest such as: 1) the differences between a cascade and a rotor tip, thus the impact of relative casing movement? 2) The difference between a transonic and a high subsonic flow condition? 3) the difference between a squealer tip and flat tip? In this study, the vortical structures and the loss mechanism of the Over Tip Leakage (OTL) flow in a high-subsonic stage and a transonic stage are analyzed using a proposed vortex model and Denton’s loss model. The two stages are specifically designed to work in the same Reynolds number with the efficiency comparable to the one predicted in the Smith’s chart. Two counter-rotating vortices, the Pressure-side Separation Vortex (PSV) and the Casing-driven Cavity Vortex (CCV), are identified as key drivers as inside a squealer cavity strongly impacting aerothermal performance (OTL mass flow and the heat transfer distribution). The cavity flow pattern results from the balancing between the CCV primarily driven by the relative casing movement, and the PSV originating from the flow separation around the pressure side rim. Consequently a detoured flow path is created within the squealer cavity when the leakage flow separating on the pressure side is entrained by the two vortices to the squealer bath and finally leaves the cavity along the suction side of the squealer wall. The entrainment of the leakage flow induces a signature of a high HTC strip on the squealer floor. Without the relative casing movement, the CCV is absent in the majority of the cavity so that the leakage flow can directly cross the tip which increases the leakage mass flow rate and reduce the HTC value on the cavity floor. Due to the distinct difference in vortical structures, the change of the HTC with and without relative casing movement can be interpreted by the vortex model. The vortex model is also able to explain the variation of the leakage mass flow rate and the HTC contours with the increasing squealer height. From the best knowledge of the authors, this is the first-of-its kind effort in using in the cavity vortices to systematically and quantitatively study the effect of the relative casing movement and the aerothermal performance of the tip with varying squealer height. In counting the aero losses for the two stages, three sources are attributed to the total loss generation: the baseline loss which assumes there is no leakage, the in-tip loss which is generated within the tip gap and the out-tip loss which accounts for the mixing loss between the OTL flow and the main passage flow. The out-tip loss is found to be the major source of the loss caused by the tip leakage flow. Denton’s loss model is used to calculate the out-tip loss quantitatively. The model predicted loss agrees in trend with the one calculated from the CFD results. According to the model, the out-tip loss is related to the main flow Mach number, the OTL mass flow rate and the velocity difference between the main flow and the OTL flow. From the distribution of these terms along the tip, the loss is mainly generated at the rear portion of the tip. The reduction of the leakage mass flow rate by the squealer is mainly at the zones where the CCV and the PSV are leaving the squealer cavity. The present analysis and results indicate that the squealer in the transonic stage tends to be less effective in reducing the out-tip loss compared to the subsonic one. The region of the tip where the CCV has already left the cavity with the PSV remaining shows the highest entropy generation rate, due to locally both the high mainstream velocity and the high OTL mass flow given the PSV being left as the only sealing vortex there.
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Xu, Kewei, and Gecheng Zha. "Design of High Specific Speed Mixed Flow Micro-Compressor for Co-Flow Jet Actuators." In ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-90980.
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Abstract This paper conducts aerodynamic design of a high specific speed mixed flow micro-compressor used as an actuator for Co-flow Jet (CFJ) Active Flow Control (AFC) airfoil. The aerodynamic design poses several challenges, including: 1) Small size with very low Reynolds number; 2) High specific speed for mixed-flow compressor due to high mass flow rate and low total pressure ratio; 3) Static pressure ratio lower than 1 to match the low pressure of CFJ airfoil leading edge (LE) suction peak. The numerical design approach is validated with a mixed flow micro-compressor with very good agreement between the predicted performance and the measured data. Front loaded rotor blade work distribution is adopted to decrease boundary layer loss at the blade surface. Free vortex work distribution is applied for the rotor span to reduce spanwise mixing loss. The rotor efficiency achieved by the numerical prediction is 91.7%. Significant loss is observed downstream of the rotor when the flow reaches the stator and the outlet guide vane (OGV). For the stator, it is found that an inlet and outlet flow path area ratio of 1.05 achieves a very high total pressure recovery of 99.29%. A very good stage isentropic efficiency of 84.3% is achieved. The final design of micro-compressor achieves a flow coefficient of 0.3 at the design point with a total pressure ratio of 1.117 and a static pressure ratio of 0.987. A structure FEM analysis indicates that the rotor blades satisfy the structure strength and modal frequency requirement.
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Fajardo, J., D. Barreto, T. Castro, and I. Baldiris. "Effect of the Environmental Conditions of Tropical Climates on the Performance Parameters of a Gas Turbine Power Generation Plant." In ASME 2020 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/imece2020-23153.
Повний текст джерелаАнотація:
Abstract It is known that high temperatures adversely affect the performance of gas turbines, but the effect of the combination of atmospheric conditions (temperature and relative humidity -RH-) on the operation of this type of system is unknown. In this work the effects of atmospheric conditions on the energy and exergy indicators of a power plant with gas turbine were studied. The indicators studied were the mass flow, the specific work consumed by the compressor, specific work produced by the turbine, the combustion gas temperature, the NO concentration, the net output power, the thermal efficiency, the heat rate, the specific consumption of fuel, the destruction of exergy and exergy efficiency. Among the results, it is noted that for each degree celsius that reduces the temperature of the air at the compressor inlet at constant relative humidity on average, the mass flow of dry air increases by 0.27 kg/s, the specific work consumed by the compressors decreases by 0.45%, the output power increases by 1.17% and the thermal efficiency increases by 0.8%, the exergy destruction increases by 0.72% and the exergy efficiency increases by 0.81%. In addition, humidity changes relative to high temperatures are detected more significantly than at low temperatures. The power plant studied is installed in Cartagena, Colombia and since it is not operating in the design environmental conditions (15 °C and 60% relative humidity) it experiences a loss of output power of 6140 kW and a drop in thermal efficiency of 5.12 %. These results allow considering the implementation of air cooling technologies at the compressor inlet to compensate for the loss of power at atmospheric air conditions.
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VanGilder, James W., Zachary M. Pardey, Xuanhang (Simon) Zhang, and Christopher Healey. "Experimental Measurement of Server Thermal Effectiveness for Compact Transient Data Center Models." In ASME 2013 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ipack2013-73155.
Повний текст джерелаАнотація:
Server thermal mass can significantly affect the rate at which a data center heats up following a loss of cooling and moderate transient temperature fluctuations due to changing CPU utilization. Recently, a compact server model has been introduced which captures the effects of thermal mass while avoiding the impractical level of detail that would be required by an explicit representation of all relevant server components. Inputs to that model include server mass, overall effective specific heat, and a parameter called the “server thermal effectiveness”. The latter characterizes the server’s ability to transfer heat to/from the airstream passing through it and can take values between zero (no heat exchange) and one (maximum possible heat exchange). Server thermal mass is a physical property of a server and is not influenced by external factors. In order to use the compact model for practical applications, we must experimentally measure the thermal effectiveness of actual servers. The present study reviews the compact model and describes the development of an experimental technique for measuring thermal effectiveness. The technique is validated using simple plate fin heat sinks in place of an actual server. This “server proxy” is sufficiently simple so that it can be modeled accurately in detail in CFD, providing well-controlled benchmark data. CFD and experimental measurements both yield a value of server thermal effectiveness of approximately 0.6, providing confidence in the model and measurement technique for the future characterization of actual servers.
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Jones, Stanley T., Martin Sommer, Alexander Rios-Forscht, and Ivan Catton. "Experimental Determination of the Viscous and Inertial Coefficients in Highly Porous Metal/Ceramic Foams." In ASME 1998 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/imece1998-0983.
Повний текст джерелаАнотація:
Abstract An experimental program has been conducted to characterize the behavior of a series of highly porous, reticulated metal/ceramic foams composed of silicon carbide. Using information from the manufacturer, an expression was developed by which the volumetric porosity was determined. The range of porosities investigated was 0.72 to 0.90 for most materials investigated. Flow experiments were conducted to determine the pressure loss as a function of the pore Reynolds number. By implementing a form of the Kozeny-Carman equation for viscous pressure loss, the specific surface area was determined from low flow rate measurements. Air was blown through a 2” diameter circular cylinder of porous media of varying lengths. The mass flow rate and pressure difference were measured under steady flow conditions. Based upon a Reynolds-Forchheimer representation of the pressure loss, these measurements allowed for determination of the viscous and inertial pressure loss coefficients. Based upon these results, a series of expressions for the Fanning friction factor as a function of pore Reynolds number are proposed for this class of porous media.
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Lang, Fred D. "Monitoring and Improving Coal-Fired Power Plants Using the Input/Loss Method: Part V." In ASME 2007 Power Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/power2007-22009.
Повний текст джерелаАнотація:
This paper presents generic methods for verifying online monitoring systems associated with coal-fired power plants. It is applicable to any on-line system. The methods fundamentally recognize that if coal-fired unite are to be understood, that system stoichiometrics must be understood in real-time, this implies that fuel chemistry must be understood in real-time. No accurate boiler efficiency can be determined without fuel chemistry, heating value and boundary conditions. From such fundamentals, four specific techniques are described, all based on an understanding (or not) of real-time system stoichiometrics. The specific techniques include: 1) comparing a computed ambient relative humidity which satisfies system stoichiometrics, to a directly measured value; 2) comparing a computed water/steam soot blowing flow which satisfies system stoichiometrics, to a directly measured value; 3) comparing computed Energy or Flow Compensators (based on computed boiler efficiency, heating value, etc.), to the unit’s DCS values; and 4) comparing a computed fuel flow rate, based on boiler efficiency, to the plant’s indication of fuel flow. Although developed using the Input/Loss Method, the presented methods can be applied to any online monitoring system such that verification of computed results can be had in real-time. If results agree with measured values, within defined error bands, the system is said to be understood and verified; from this, heat rate improvement will follow. This work has demonstrated that use of ambient relative humidity is a viable verification tool. Given its influence on system stoichiometrics, use of relative humidity immediately suggests that effluent (Stack) flow can be verified against an independently measured parameter which has nothing to do with coal-fired combustion per se. Whether an understanding of coal-fired combustion is believed to be in-hand, or not, use of relative humidity (and, indeed, soot blowing flow) provides the means for verifying the actual and absolute carbon and sulfur emission mass flow rates. Such knowledge should prove useful given emission taxes or an imposed cap and trade system. Of the four methods examined, success was not universal; notably any use of plant indicated fuel flow (as would be expected) must be employed with caution. Although applicable to any system, the Input/Loss Method was used for development of these methods. Input/Loss is a unique process which allows for complete understanding of a coal-fired power plant through explicit determinations of fuel chemistry including fuel water and mineral matter, fuel heating (calorific) value, As-Fired fuel flow, effluent flow, boiler efficiency and system heat rate. Input consists of routine plant data and any parameter which effects stoichiometrics, typically: effluent CO2, O2 and, generally, effluent H2O. The base technology of the Input/Loss Method has been documented in companion ASME papers, Parts I thru IV, which addressed topics of base formulations, benchmarking fuel chemistry calculations, high accuracy boiler efficiency methods and correcting instrumentation errors in those terms affecting system stoichiometric (e.g., CEMS and other data).
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Klausner, Enrico, and Uwe Gampe. "Evaluation and Enhancement of a One-Dimensional Performance Analysis Method for Centrifugal Compressors." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-25141.
Повний текст джерелаАнотація:
The one-dimensional flow analysis along a mean streamline is an appropriate and established procedure for initial design and performance analysis of turbomachinery. One such method for performance analysis of centrifugal compressors was published by Aungier in the 1990s. The latest description of Aungier’s performance prediction model was applied to a set of centrifugal compressor stages published in literature. For each test case the whole performance map was calculated and compared with measurement data. The calculation results correspond well with measured data over a wide operating range. However, near choke or stall the mean streamline performance prediction deviates from measurements. After evaluation of this “standard” mean streamline model specific loss correlations, e.g. for choking, incidence and shock losses were replaced by theoretical models. The aim was to implement a more physical based loss model which is able to predict the performance of compressor stages outside the limits of the standard procedure. The modified procedure was again validated against measurements of the above mentioned compressor stages. The modified procedure gives a better prediction of operating performance and behavior. Shortcomings of the procedure are still the overestimation of vaneless diffuser losses at low mass flow rates and the uncertainty in prediction of choke limit. In conclusion recommendations for advancement of the one-dimensional performance analysis method are given.
Звіти організацій з теми "Mass specific mass loss rates"
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Fahima, Tzion, and Jorge Dubcovsky. Map-based cloning of the novel stripe rust resistance gene YrG303 and its use to engineer 1B chromosome with multiple beneficial traits. United States Department of Agriculture, January 2013. http://dx.doi.org/10.32747/2013.7598147.bard.
Повний текст джерелаАнотація:
Research problem: Bread wheat (Triticumaestivum) provides approximately 20% of the calories and proteins consumed by humankind. As the world population continues to increase, it is necessary to improve wheat yields, increase grain quality, and minimize the losses produced by biotic and abiotic stresses. Stripe rust, caused by Pucciniastriiformisf. sp. tritici(Pst), is one of the most destructive diseases of wheat. The new pathogen races are more virulent and aggressive than previous ones and have produced large economic losses. A rich source for stripe-rust resistance genes (Yr) was found in wild emmer wheat populations from Israel. Original Project goals: Our long term goal is to identify, map, clone, characterize and deploy in breeding, novel wild emmer Yr genes, and combine them with multiple beneficial traits. The current study was aiming to map and clone YrG303 and Yr15, located on chromosome 1BS and combine them with drought resistance and grain quality genes. Positional cloning of YrG303/Yr15: Fine mapping of these genes revealed that YrG303 is actually allelic to Yr15. Fine genetic mapping using large segregating populations resulted in reduction of the genetic interval spanning Yr15 to less than 0.1 cM. Physical mapping of the YrG303/Yr15 locus was based on the complete chromosome 1BS physical map of wheat constructed by our group. Screening of 1BS BAC library with Yr15 markers revealed a long BAC scaffold covering the target region. The screening of T. dicoccoidesaccession-specific BAC library with Yr15 markers resulted in direct landing on the target site. Sequencing of T. dicoccoidesBAC clones that cover the YrG303/Yr15 locus revealed a single candidate gene (CG) with conserved domains that may indicate a role in disease resistance response. Validation of the CG was carried out using EMS mutagenesis (loss-of- function approach). Sequencing of the CG in susceptible yr15/yrG303 plants revealed three independent mutants that harbour non-functional yr15/yrG303 alleles within the CG conserved domains, and therefore validated its function as a Pstresistance gene. Evaluation of marker-assisted-selection (MAS) for Yr15. Introgressions of Yr15 into cultivated wheat are widely used now. Recently, we have shown that DNA markers linked to Yr15 can be used as efficient tools for introgression of Yr15 into cultivated wheat via MAS. The developed markers were consistent and polymorphic in all 34 tested introgressions and are the most recommended markers for the introgression of Yr15. These markers will facilitate simultaneous selection for multiple Yr genes and help to avoid escapees during the selection process. Engineering of improved chromosome 1BS that harbors multiple beneficial traits. We have implemented the knowledge and genetic resources accumulated in this project for the engineering of 1B "super-chromosome" that harbors multiple beneficial traits. We completed the generation of a chromosome including the rye 1RS distal segment associated with improved drought tolerance with the Yr gene, Yr15, and the strong gluten allele 7Bx-over-expressor (7Bxᴼᴱ). We have completed the introgression of this improved chromosome into our recently released variety Patwin-515HP and our rain fed variety Kern, as well as to our top breeding lines UC1767 and UC1745. Elucidating the mechanism of resistance exhibited by Yr36 (WKS1). The WHEAT KINASE START1 (WKS1) resistance gene (Yr36) confers partial resistance to Pst. We have shown that wheat plants transformed with WKS1 transcript are resistant to Pst. WKS1 is targeted to the chloroplast where it phosphorylates the thylakoid-associatedascorbateperoxidase (tAPX) and reduces its ability to detoxify peroxides. Based on these results, we propose that the phosphorylation of tAPX by WKS1 reduces the ability of the cells to detoxify ROS and contributes to cell death. Distribution and diversity of WKS in wild emmer populations. We have shown that WKS1 is present only in the southern distribution range of wild emmer in the Fertile Crescent. Sequence analysis revealed a high level of WKS1 conservation among wild emmer populations, in contrast to the high level of diversity observed in NB-LRR genes. This phenomenon shed some light on the evolution of genes that confer partial resistance to Pst. Three new WKS1 haplotypes displayed a resistance response, suggesting that they can be useful to improve wheat resistance to Pst. In summary, we have improved our understanding of cereals’ resistance mechanisms to rusts and we have used that knowledge to develop improved wheat varieties.